73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Brakes, Frame, Steering & Suspension => The Highs (Raising/Lifts) => Topic started by: 5l1p5tr3am on January 23, 2016, 03:43:32 am
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Hi All :-)
Well, the 12" lift I've had sitting in the garage for the past year is finally going on next week. As I was going thru all the parts tonight, I realized that I didn't purchase any steering components with all the suspension stuff. Anyone know what parts I'll need? Unfortunately crossover steering isn't an option at the moment for financial issues.
Thank you in advance for any input :-)
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What front axle are are you working with?
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Gonna need a Dana 60 with a crossover tie rod to run 40's
A large transfer case drop bracket
Maybe cut and turned knuckles
I assume you're running 40 or 44's with a 12" lift ?
Cause 33's will fit with no lift
35's fit with a 2" or 4" lift
Sent from my iPhone using Tapatalk
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12" lifts are illegal in almost every state. That does not stop anyone however.
12" lifts are dangerous to drive on the road, that goes without saying... so making the steering perfect is expensive. A crossover is the only practical safe way to do that and stay legal. Most use hydraulic steering but that, for some reason, is also illegal in most states to my understanding.
The best I think you will get is a poor fix at best. A lifted steering will give you 2"-4", a dropped pitman arm will give you 2", a steering arm block will give you 2" (max), so maybe 8"'s of correction leaving you with 4" of wrongness. However, once the 40" tire mark is achieved all these fixes will break due to the weight of the tires and stresses involved in turning them when stuck in a rut. Of course you might not know they broke until you are going home at 65mph at which time they will make their presence known. None of these fixes takes into account the weak frame rails that the steering box hangs on. My steering box broke the frame rail in the middle of a bridge in St. Louis with only 36" monster mudders. It happens. I got it home but it was like driving a piece of wet spaghetti. I also would not recommend driving a 12" lift with the stock rag joint. I had that come apart on me in the truck I currently have, luckily it happened after a high speed run up the road to test something, I had just pulled into the parking lot at work and it came apart...instant no steer, just a steering wheel turning aimlessly.
Unless the truck is a trailer queen I would highly suggest you think this through thoroughly before committing. Over 6"-8" of lift and things get spendy and dangerous quickly.
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i let my brother drive my 79 with 6' of lift and a steering block on the dana 44. he made it a little down the road and it broke, he called me and asked how much play is supposed to be in the steering wheel. i thought he just wasnt used to the big tires. i get to him and 2 of the 3 bolts broke. fitz even had a 12" lift took it off for a smaller more comfortable ride. granted im 31 now but i wouldnt want to ride in a 12" lift maybe in my early 20s but not now
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Another major point that Irish made.
In addition, a 12" lift has the ends of the springs pointing nearly straight up. That leaves very little room for movement and little to no suspension action. The action that is there is severely limited by the length of the shackle straps. Of course, double acting shackles https://www.google.com/search?q=revolver+shackles+shackles&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjhn5Gmj8HKAhWCFj4KHVJoAUIQ_AUICCgC&biw=992&bih=410 (https://www.google.com/search?q=revolver+shackles+shackles&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjhn5Gmj8HKAhWCFj4KHVJoAUIQ_AUICCgC&biw=992&bih=410) could be used (again illegal for road use) but they really only work for droop and they were never intended as a fix for a tall lift.
Tall lifts are fun to watch at mud bog events, but those trucks likely were never driven to the event except on a trailer or from really close distances. The amount of stress exerted on the frame rails from sideways stresses is also something that needs considering. Not to mention the weight of the unsprung parts (tires, axle housings, springs, brakes, etc). Stock frames were meant to handle the loads of weight that went inside the beds, weights of trailers on a tongue (up to acceptable tongue weights) and the weight of the puny little tires the factory put on them. Back then things had overkill built in however. There was very little CAD testing used to predict the breaking point of the parts used. So what we would consider strong then would never even be considered by a manufacturer these days, it would be considered a waste of resources to build beyond barely adequate. They get around that today by using strategically placed bracing, not shear strength of the parts.
As has been mentioned, a 12" lift will easily accommodate 40+ inch tires (about 100+ lbs apiece- TSL Bogger: 18/39.5-16.5LT 115lbs; 19.5/54-20LT 198lbs), the rim weight, the brakes needed to stop all the rolling weight, and the shocks needed to control all of it.
Not to mention having to have a ladder just to get in and out of it. ;)
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Wow, BIG thanks for all the input guys. Legality isn't an issue. I live in Cali so lift kits aren't prohibited per say. I am limited, however, to a 30" maximum frame height. Even with a 12" lift I'm still in compliance. Safety is a big concern for me though. Not just for myself but for others on the road so I have to do it right. I didn't realize how expensive this was going to get. In retrospect, I should have gotten a smaller lift. But alas, I already dropped the cash on this 12" ORD kit and 40" tire/wheel combo last year so I may as well finish what I started. I got the leaf springs, shocks, u-bolts, steering box brace and shackles with the kit.
Sooooo... being that my current axle is a corporate 10-bolt, it looks like I'm ponying up for a D60, dropped pitman arm, steering arm, draglink, and some beefed up tie rod ends. Did I miss anything, gents?
Thank you all again :)
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I live here in California, both of my parents were police officers, 1 of which was a traffic officer. If you think you can legally get away with a 12" lift then you are wrong. There are many rules and regulations that go along with lift kits and not just frame height. There are also rules for headlight adjustments, tire size, mud flap size (which 100% will be required with 40 inch tires & wheels). Not to mention the slew of questions that will be thrown at you if one of those components ever fails and you end up in an accident that seriously injures or God forbid kills someone and you aren't seriously injured or killed yourself. Questions that will be about your knowledge and vast experience with installing lift kits of this size and their steering components, questions about do you know the science behind weight vs stopping power vs steering ability. They will also ask if you installed it yourself or had an experienced shop install it and probably most decent shops would advise against something that large unless it was a show only vehicle. Not to mention you miss judge a corner or emergency maneuver wrong one time and depending on the speed and other factors that whole truck could simply just tip over. You would have no warning or control over it, it's just gonna happen and you won't be ready for it.
If you like I can ask my parents and some of our still active friends in law enforcement about the current vehicle codes for lifts of that size. My best advice to you for YOUR safety and the safety of OTHERS on the road is just DON'T. Find a smaller, safer lift, one that doesn't compromise the integrity of the parts and frame of the truck like the others above said a lift of that size does.
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Irish is right. My 81 long bed step side had a 12" lift with 44" Super Swampers when I bought it. I bought this truck with the intention of lowering it down and using it as a daily driver.
Newer members may not recognize this truck. I blew the motor years ago and put into storage and started driving my CUCV Chevy Military trucks.
I got this truck from a friend of mine who built it as a local show truck. It would only come out a few times a year for car shows, and it would make its yearly appearance at the July 4th parade.
The truck was great to look at, but like Ralph Nader said about the Corvair, it truly was "unsafe at any speed".
I lowered it down with a 6" lift and some 35"s and it was a much more driver friendly truck. I drove it daily for a short time until the SB 400 TPI motor blew up on the highway. I put the truck in storage that day and it hasn't seen the light of day since.
What transfer case do you have? My truck had a divorced transfer case set up. It ran a 2 W.D. turbo 350 with a short drivesfaft leading to a Rockwell gear driven transfer case.
What gears do you have? My truck had 5:13 gears to turn the 44"s.
My friend spent a lot of money building this truck. I was able to sell of the lift & tires to offset some of the cost of lowering it down to (if you can call a 6" lift & 35"s lowered). I had to change the tranny output shaft, transfer case, lift kit, driveshafts, tires & rims, etc.
My advice would be to sell the 12" lift and buy something smaller like a 6" lift.
Are there allot of trucks in your area running a 12" lift with 40"s? If not, there is probably a reason why not.
Hopefully you will consider the advice myself & others gave you, but in My younger days, I would ignore it also.
Keep in mind that there are other cost that you have not mentioned like the transfer case, driveshaft, gears, etc. This stuff adds up quick.
In the end, you might build a truck that the Police aren't a fan of. I'll save that story for another day.
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I'd sell the kit and use a 6" and trim the fenders a little
You're gonna need a Dana 60 front and a 14 bolt full floater rear for 40's
Anything smaller will break
Gotta beef up the frame around the steering box too
Sent from my iPhone using Tapatalk
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Half of 40" tires is 20" and add a 12" lift (above stock) is 32" so your frame will be above that.
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Don't think we're trying to beat you up about the 12". but each one of us is trying to point out problems that we have faced and giving you a heads up about them. Just looking out for you and others
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Don't think we're trying to beat you up about the 12". but each one of us is trying to point out problems that we have faced and giving you a heads up about them. Just looking out for you and others
Yes, we aren't picking on you. Just giving you all the information so that you can make an informed, smart and SAFE decision.
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In the olden days a 40" (39" actual) tire would fit fine with a 6" lift and some minor trimming of the rear of the front fender (remember, the tires move backwards when under compression on both axles) assuming the width worked (a 15" wide tire is about the max the stock-offset rims can take) with the right offset a 18" wide tire will fit but look goofy IMHO and cause some serious tire scrubbing in turns.
As fitz said, when we were younger we would also be likely to ignore this advice too. But to do so is at not only your peril but the safety of others on the road with you. Back in the day a favorite bumper sticker said 'Smile as you go under'. There was a reason those tall lifts got to be illegal.
However, as you are learning, a 1/2 ton frame really is not up to the task of a 12" lift and a 10 bolt rear-end is barely capable of handling 31 inch tires much less 40". NO rear-end that carry's the load with the axle bar itself will stand up to even mild street use with 40" tires. (I ruined two 12 bolts before I got a 14 bolt) A D60 or 14 bolt (both FF'ers) is minimum back there. A D44 up front will handle the mild stuff as long as you keep the tires in firm contact with the ground, which means easy rock climbing and rational go pedal while mudding. However, stopping is still an issue. I had 39's (about an actual 38") and had no problems (because I swapped the largest disc brakes that would fit as stock on the front and the 14 bolt had one of the largest available drum brakes on it), I could lock up all fours easy enough but the tires were not radial tires.
I think you might be really happy with a 6" lift and use the tires you have. Cutting the fenders in no way compromises the looks of the truck if done with some thinking beforehand. My old 6" lift and 39's put the bottom of the window right at my nose height and I'm 6' even barefooted. That makes getting in and out an acrobatic experience. As a word of caution...do not hold the door as leverage to hoist your but into the seat or you will have perpetually misaligned doors, use the A pillar instead or put in baby bars. Better yet is those motorized steps ;) Whats money after all?
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Here's my 6" +3" with 40s
(http://i333.photobucket.com/albums/m387/rebel_cowboy_83/IMG_20130807_194815_zpsead58c4c.jpg)
And with 44s
(http://i333.photobucket.com/albums/m387/rebel_cowboy_83/Mudding/IMG_20140608_193506933_zpsscadgreq.jpg)
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As Greybeard pointed out, if done with care, there is nothing wrong with trimming the fenders.
Check out this truck (its not mine, found the pic for online). Someone did a great job of "stretching" the front wheel opening, like the hot rod guys do to the rear 1/4's when they tub a pro street car. Notice how there is no front fender marker light? Someone did some serious work on this truck to fit big tires with a small lift.
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Here's the picture.
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Don't worry guys; I'm not butthurt. lol. I definitely appreciate all of your knowledge and experience. As I stated in the beginning, safety is my primary concern. 12" lifts are common here where I live, but those are all on newer Ford F250/F350s. Totally different story to be sure. After much consideration I think it would be best for me to sell the 12" lift and go with a 6". I have a set of 37s too, so I should be OK without fender trimming. But if I need too that's fine.
Thank you again for all of your time and insight 8)
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I want to weigh in on this but don't have the time to type a 16 page post.
Check back later.
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Here's the picture.
I believe those are aftermarket fiberglass fenders, an outfit in Florida (I think that's where they are) makes them, http://www.usbodysource.com/ (http://www.usbodysource.com/).
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Here's the picture.
Yea I was gonna say, that doesn't look like heavily messaged body work on the fenders. I don't think the tires are really as big as one might think.
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I'm thinking fenders like this with a 6" lift might clear the 40" tires.
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I want to weigh in on this but don't have the time to type a 16 page post.
Check back later.
I'm looking forward to your reply.
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Sorry it took so long to get back to this thread.
This picture is of my '77 with 8" Skyjacker front springs, custom rearched rear springs, and a 3" body lift. 11" of lift total. For steering corrections the truck has the standard Dana60 block, and a Skyjacker drop pitman arm. And that is all.
The 18.5/44-16.5 Gumbo Monster Mudders were purchased, mounted, and balanced by Midwest 4x4 in StLouis, MO.
The truck drove like a dream.
(https://lh3.googleusercontent.com/-MKHNCU_LLBg/VcKVLlSpiyI/AAAAAAAAANE/pcdM7AmRCVw/s512-Ic42/44s.jpg)
Now, for my thoughts on a 12" lift. Based on previous replies in this thread there may be some disagreement with my opinion, but that is fine, the great thing about this website is that we can discuss our differences and be civil about it.
You can get away with a 12" lift on a street truck. It is doable. But it is not as simple as bolting on the lift and putting the truck in gear. If the Super Duty trucks are getting away with it so can you. However as has been mentioned there are epic compromises to make it work.
A spring that gives 12" of lift will in all likelihood have such a high spring rate that a degradation in stability won't be noticeable.......think of it this way......your suspension will basically be solid. There will be some change in handling as your center of gravity is greatly altered. Ride will be something you cannot consider if you want this to work.
In engunearin skool they preach sprung, (what is held up by the springs) and unsprung (what isn't supported by the springs) weight ratio. If you want a comfortable ride you limit unsprung weight as much as possible. The reason a 1976 Cadillac Eldorado rode like a pontoon boat on a lake is because it has enormous amounts of sprung weight over a moderate amount of unsprung weight.
What relevance does sprung weight have to do with a 12" lift? The more sprung weight you have the more leverage this places on the springs. Without heavy dampening the result is an unstable platform. Now lift that weight up into the air and the result is instability added exponentially.
Now back to my aforementioned theory on spring rate. To gain the lift more leaves will need to be added to maintain the height. This has the unavoidable consequence of adding spring rate. Bad for ride comfort, but, in theory, good for stability. Bear with me on this. By adding spring rate, making the springs less likely to deflect from highway forces, you limit the squishy feeling that makes the truck drive itself. In this case if the truck body could be lighter it would have the effect of lowering the center of gravity. However, since the body is sprung weight, the ride will suffer more.
There are stupid fads in off-roading that come and go. Like kicker shocks. Crossover steering is not in this category. There is a reason crossover steering has been around for 30 years, it works. Spend the coin for crossover steering. It is the only sane way of making this work. Modifying the factory steering requires too many changes that are only patches at best. The crossover steering keeps the steering forces in a more workable plane. Still not perfect but better than the short linkages that result from modifying the factory stuff. Dropping one pivot point 12" away from the travel plane of the other pivot point will result in less angular stress across the front of the truck which is about 48" away versus using the factory drag link which is only about 15" between pivots on the factory drag link.
Now there is an advantage to retaining the factory front-back traveling steering linkage. If modified properly bump steer can be avoided with the factory setup since it can be made to cycle in an arc that will change in a similar amount as the natural rearward travel of the front axle as the suspension cycles. Crossover steering cannot be built in a way that prevents bump steer entirely. With crossover steering as the suspension cycles the front axle travels laterally to the centerline of the truck whereas the crossover link arcs perpendicular to the centerline of the truck. The best bet there is to keep the crossover link as level as possible to minimize the arc it travels in.
To run 40"+ rubber you need a Dana60/14-bolt. 'Nuff said.
If I were to build a street rig with the 44" tire route again I believe I would opt for 2 1/2 ton Rox. Stronger knuckles, housings, axle shafts, and the raised location of the pinion with the double reduction helps keep the u-joints from slinging themselves apart every 6 months. Which brings up another point. With stock axles a 12" lift will force you into radical u-joint angles, especially on the front. The Saginaw CV-joint, after the tabs are ground off, still won't accommodate much more than 8" of lift.
As far as legality, CA regulates even how you knot your shoe laces. I can't imagine the noobs in Sacramento have managed to ignore even the slightest modified pickup.
I love lifted trucks, the bigger the better. I encourage you to build the truck of your dreams, but there are reasons why most tall lifted trucks are trailered to the car shows and mud pits.
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As far as legality, CA regulates even how you knot your shoe laces. I can't imagine the noobs in Sacramento have managed to ignore even the slightest modified pickup.
Everything Engineer said is great. This part tho, couldn't be a more accurate statement of the truth. Hahaha.
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im going to add one thing.
everyone talks about the dana 44 or 12 bolt needing to be upgraded
but this is me and my dana 44 with a posi unit up front turning 40s (first time for the posi unit which could be why it held up idk)
(http://i333.photobucket.com/albums/m387/rebel_cowboy_83/Mudding/IMG_1817_zpsatewhevn.jpg)
now dont think this means it will hold up, cause i know its only a mater of time before one breaks again. ive broken i think 3 with just 38s and granaded the dif with 44s. the dana 60 is 3" longer than the dana 44 so you will need a shorter driveshaft. so if you start with a dana 44 and decide to switch you will need to have the driveshafts shortened.
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Engineer, can't thank you enough for your insight. It's great to hear some practical examples of theory as it helps understanding. Your projects are awesome! I appreciate your input and experience as well, Irish. At this point, as much as I'd loooooooove to have that 12" on, I just can't throw another 2k at the truck for the, D60, x-over steering, upgraded steering components, changing the pinion angle, etc. I know I could get by with the D44 for a while but still. I think I'll be just fine with the 6" suspension lift and maybe a 3" body down the line if I feel the need. Assuming I can get this 12" kit sold, I will recoup enough to pay for the 6" plus some small additional stuff.
Thank you again, gents!
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you might want to wait till tax money comes along and you can sell it to someone with a big pay check from the irs
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Sorry it took so long to get back to this thread.
This picture is of my '77 with 8" Skyjacker front springs, custom rearched rear springs, and a 3" body lift. 11" of lift total. For steering corrections the truck has the standard Dana60 block, and a Skyjacker drop pitman arm. And that is all.
The 18.5/44-16.5 Gumbo Monster Mudders were purchased, mounted, and balanced by Midwest 4x4 in St. Louis, MO.
The truck drove like a dream.
Now, for my thoughts on a 12" lift. Based on previous replies in this thread there may be some disagreement with my opinion, but that is fine, the great thing about this website is that we can discuss our differences and be civil about it.
You can get away with a 12" lift on a street truck. It is doable. But it is not as simple as bolting on the lift and putting the truck in gear. If the Super Duty trucks are getting away with it so can you. However as has been mentioned there are epic compromises to make it work.
A spring that gives 12" of lift will in all likelihood have such a high spring rate that a degradation in stability won't be noticeable.......think of it this way......your suspension will basically be solid. There will be some change in handling as your center of gravity is greatly altered. Ride will be something you cannot consider if you want this to work.
There are stupid fads in off-roading that come and go. Like kicker shocks.
Now there is an advantage to retaining the factory front-back traveling steering linkage. If modified properly bump steer can be avoided with the factory setup since it can be made to cycle in an arc that will change in a similar amount as the natural rearward travel of the front axle as the suspension cycles. Crossover steering cannot be built in a way that prevents bump steer entirely. With crossover steering as the suspension cycles the front axle travels laterally to the centerline of the truck whereas the crossover link arcs perpendicular to the centerline of the truck. The best bet there is to keep the crossover link as level as possible to minimize the arc it travels in.
To run 40"+ rubber you need a Dana60/14-bolt. 'Nuff said.
If I were to build a street rig with the 44" tire route again I believe I would opt for 2 1/2 ton Rox. Stronger knuckles, housings, axle shafts, and the raised location of the pinion with the double reduction helps keep the u-joints from slinging themselves apart every 6 months. Which brings up another point. With stock axles a 12" lift will force you into radical u-joint angles, especially on the front. The Saginaw CV-joint, after the tabs are ground off, still won't accommodate much more than 8" of lift.
As far as legality, CA regulates even how you knot your shoe laces. I can't imagine the noobs in Sacramento have managed to ignore even the slightest modified pickup.
I love lifted trucks, the bigger the better. I encourage you to build the truck of your dreams, but there are reasons why most tall lifted trucks are trailered to the car shows and mud pits.
Hi Engineer,
You live in or near the St. Louis area? I am originally from Florissant, MO. I knew Bob Chandler through my brother-in-law first before he ever opened Midwest and was simply selling some items out of his garage. Back in the mid-seventies to early eighties I used to wheel with some of his early frame fabricators and mechanics down on the Black River in Lesterville
My '78 truck is on the left, still in it's 4" lift and 36's. This was in about 1984 I guess. Not a beauty by any stretch but more than capable of running in 5' of water all afternoon.
(http://i1216.photobucket.com/albums/dd361/1john9/truck%20stuff/IMG_20140227_231730.jpg) (http://s1216.photobucket.com/user/1john9/media/truck%20stuff/IMG_20140227_231730.jpg.html)
before I moved permanently out of the state in 1985. They closed the Black River to public wheeling about 1987 I believe. My last year on the river was in 1986 when I traveled back there from Colorado to visit with the gang. I haven't been back to Missouri since.
Me and my future niece in 1986 at Midwest 4x4 visiting. This is BF2.
(http://i1216.photobucket.com/albums/dd361/1john9/truck%20stuff/IMG_20140227_230554.jpg) (http://s1216.photobucket.com/user/1john9/media/truck%20stuff/IMG_20140227_230554.jpg.html)
(http://i1216.photobucket.com/albums/dd361/1john9/truck%20stuff/IMG_20140227_230543.jpg) (http://s1216.photobucket.com/user/1john9/media/truck%20stuff/IMG_20140227_230543.jpg.html)
(http://i1216.photobucket.com/albums/dd361/1john9/truck%20stuff/IMG_20140227_230534.jpg) (http://s1216.photobucket.com/user/1john9/media/truck%20stuff/IMG_20140227_230534.jpg.html)
I'd like more of your thoughts on the stock steering setup. You mentioned that you had an 8" lift on your truck and used a block under the steering arm and a dropped pitman arm. With a D60 this is all that is necessary with a 8" lift to get the steering as close as it can be. A D44 will still come up rather short of the desired alignment IIRC. However, beyond 8" I shudder to think of those that use the bent drag links. They do work (if reduced lock-to-lock steering is acceptable) but like every piece of steel that has a bend in it the overall strength of the rod has been severely compromised under compression not to mention that the angle between pivots, like you said, should remain as level as possible no matter the style of steering used. Even though the axle housing does move in a rearward plane (arc?) during spring compression, the actual movement does not cause as much feedback through the steering as does the misaligned pivot points. Am I correct?
As an aside, back in the days when I spent three weeks a year on the Black river I talked to a few folks that mentioned they dislocated or outright broke a thumb because of bump steer with a bent drag link. It happens I guess.
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I will say this.. my truck with a 4" lift rides pretty rough. I would hate to be in a truck with 12" of lift on the road. UGH.
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Greybeard-
I'm really busy right now. I want to answer your question and to do so will take some time to properly explain it. Check back in a couple of days.
Also, when my wife and I were dating and first married we used to go to Lesterville. The last time we were there a guy I went to high school with got his '79 Ford F-150 4x4 smoked by a dude on an ATC-250R. The guy on the 250R was helicoptered to StLouis. The guy I went to high school with had to have his Ford towed home do to the extensive front end damage. Never found out what happened to the guy on the 250R. Darryl's Ford had to have the front end sheet metal replaced and the crash ripped the steering box apart.
And check out my build thread. I have a post in there where I describe visiting a guy's shop who built Bigfoot's last two race trucks.
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NP.
For thirty or more years I have lived by the rule that Chevy steering has to have the pitman end at the draglink and the steering arm end at the drag link at as close to parallel with the truck and ground as is possible and practicable. Plus or minus an inch does not hurt too bad. Four inches causes steering problems, all a bent drag link does is connect the pitman to the steering arm so the truck can be steered, it does not fix any misalignment between the two...it's band-aid.
enaberif
Have you played with air pressures? There is a sweet spot for every tire and that spot is not necessarily the pressure on the door jamb or the sidewall. My Mickey T Tall Bajas (39-15/15) took 30 psi from the sidewall. I ran about 13psi all the time on road and went as low as 3psi offroad and never had any problems. Of course they were bias belted tires. My current Dodge 2500 I have ten ply rated tires on it and run about twenty pounds less than the sidewalls ask for and have for the last three years. Just sayin....sidewall pressure is for max loads on that one tire. I have never come close to loading my truck to that max weight. A couple weeks ago I did air them up to max pressure because I had one ton of catfood in the shortbox and three tons in a trailer. I'm certain I still never came close to loading those tires to near their maximum capacity though.
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Its not tire pressure its straight up rough suspension. I live in a City where the roads will bottom out a lot of cars so on a solid axle truck it just jars the crap out of you everywhere. Now it could simply be a choice of springs and shocks which I could improve down the road.
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have to disagree its a combination of both. i know one set of tires i have are max at 85lbs. theyre now on my ½ton with only 40psi even the tire shop asked if i would be hauling anything, i told them no. they said they would put 40 lbs in them so it doesnt ride so rough. its not a bad ride and the wife doesnt complain.
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I'm running with 32-35psi in my tires so I know its not that. I don't want to derail the thread it was just a comment I made about how I think a 12" lift would be rough.
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I don't know, I think we've beat the 12" horse to death already. ;D
But just to make certain....I believe the OP has determined that everyone here cannot be totally wrong and has determined that good judgement is to sell the 12" lift and use the proceeds to buy something more practical. The way I see the 12" lift riding is similar to writing the letter U and putting a truck on top of it. Both ends of the U point nearly straight up. How on earth can that flex? And without 12" long shackles there is not enough movement in the spring end anyway. Of course my numbers are not accurate but the idea is still valid.
As for tire pressures in over sized tires...I read on offroad magazine years ago (one of the magazines anyway) the way they figured it was most practical to find the desired tire pressure for a given tire on a given truck. I used the technique and found it worked pretty good. It may not work as well with radials but it still works OK.
It's simple, use some kids sidewalk chalk, make a good wide, about 1/2" wide will do, mark across all the treads from sidewall to sidewall in a couple of different places on the tires. No need for uniformity. Do this in a parking lot or someplace with fairly clean, really dry, and smooth asphalt. Drive the truck in a figure eight two times at least at a reasonable speed but not to fast. Try not to make the figure at steering lock tightness either. Look at the chalk stripes. If they are not worn off drive another lap or two and check them again. The chalk should wear faster off the high spots of the tire tread IE, the sides if under-inflated, the center if over-inflated. Some experimentation on the speed and tightness of the turns used might be necessary. It works though. It, like a lot of other things, just takes time and patience (and no cops wondering what the heck you are doing).
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Ive done the same thing with chalk. But drive in a straight line and see how it wears of
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i know with racing, if the tire temp isnt even you dont have maximum tire contact. which if you want top speed less is better but if you want acceleration more is better. i keep that in mind when airing my tires. max psi will cause a high center, wont be good for traction but better for mpgs. low center will be good for traction but more drag so less mpgs. too much of either or will have more problems.
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Yup, but the issue here is ride quality, there is no all around perfect air pressure for all. Like all this automotive, the stock tires had the pressures set for a compromise. That's the best one can hope for I believe.
And maybe the test with the chalk was in a straight line, I read that article about 20 years ago. Details elude me at times. :P
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I'd like more of your thoughts on the stock steering setup. You mentioned that you had an 8" lift on your truck and used a block under the steering arm and a dropped pitman arm. With a D60 this is all that is necessary with a 8" lift to get the steering as close as it can be. A D44 will still come up rather short of the desired alignment IIRC. However, beyond 8" I shudder to think of those that use the bent drag links. They do work (if reduced lock-to-lock steering is acceptable) but like every piece of steel that has a bend in it the overall strength of the rod has been severely compromised under compression not to mention that the angle between pivots, like you said, should remain as level as possible no matter the style of steering used. Even though the axle housing does move in a rearward plane (arc?) during spring compression, the actual movement does not cause as much feedback through the steering as does the misaligned pivot points. Am I correct?
Greybeard think of it like this:
(Before you start reading don't think I assume you to know nothing. I realize you already know most of what I am posting here but for the benefit of those who don't it may read a little elementary. I just hope to explain what I have to say so that everyone can understand it.)
Position yourself outside of our trucks (73-87 Chevy/GMC) looking at the driver's side front tire. Assuming a stock suspension the spring is flat. With this spring you get very little extension/contraction of the length of the spring as it cycles. Additionally the spring is only slightly canted downhill toward the rear of the vehicle by about 3° (you have about 4° built into your axle housing for roughly 7°total caster) to facilitate suspension cycling as the truck is moving forward. Therefore on an unmodified truck it is most optimal to have the steering pivots in a level plane with the horizontal axis of the truck.
Now as lift is added to the truck typically this is done by adding arch to the front spring. With the arch, as the suspension cycles the length of the spring will grow, or elongate. Since the front of the spring is anchored to the frame the axle will deflect rearward with the elongation of the spring. The more arch you have the more the spring will elongate for a given deflection.
One thing that is constant regardless of how much arch a spring has is the fact that the axle will deflect exactly 1/2 the distance of the total deflection of the spring. Now this is dependent on having a spring anchored on one end and a pivot on the other end. And the axle must be located in the center of said spring. (As is the case on our trucks)
Now back to our truck. Assume we have an 8" lift. If we are to look at our left front tire from the side and we can envision the axle moving upward from a bump in the road, let's say the axle deflects rearward 1" as it is cycling. In order to prevent bump steer with our stock steering we would need the rear steering pivot to motion rearward the same 1". Now we know the front steering pivot will stay stationary to the horizontal plane of the truck because the steering box is mounted solidly to the frame in the same manner as the front of the spring. We also know the steering pivot on the axle will deflect up and down exactly as the axle does. With our factory steering, look at the front steering pivot as if it is the center (or axis) of an imaginary circle. Now picture the rear steering pivot as the out side of the same imaginary circle. The typical drag link on our (73-87 Chevy/GMC) is about 15" long. If we were to drop the rear steering pivot, use 3" as a baseline, below level this would cause the pivot to move rearward a measured amount as it rotates around that imaginary circle as the axle cycles upward, and of course rearward as we compress our 8" rearched spring.
The way to limit or stop bump steer altogether is to build correction in our steering that finds the "sweet spot" in the imaginary circle that will allow the correct forward and rearward travel of the rear steering pivot in a way it matches the forward/rearward travel of the axle.
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Graybeard to answer one of your questions that I missed in my last post, I should've added that you want your crossover link as flat as possible because if everything is correct in your suspension the axle shouldn't cycle sideways.
But this flat link theory does not apply when using modified factory steering. With modified factory steering you definitely can't run the steering pivots level with the ground and have the proper geometry as I have previously explained.
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The spring cycle being talked about is one of the reasons why longer shackles exist for the front. Its quite common and possible that with lifted springs the spring itself can and will hit the frame.
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I see what you are saying, however, in order to lesson the total bump-steer the drag-link needs to be in as neutral a position as possible to facilitate both up and down motions. That rearward movement can never be eliminated as you say. Therefore, by starting in a position that does not initially push against the pitman arm any bump steer is reduced to the minimum during the upward and rearward movements of the housing. If the drag link starts at an upwards angle towards the pitman arm, that imaginary arc (as the truck frame/body moves down in relation) and the very real rearward movement of the housing moves it (the drag-link) directly into the pitman and subsequently through to the steering wheel.
A drag-link that starts level between the steering arm and pivot arm ends reduces the total amount of deflection the pitman will realize as the suspension starts to move in either direction.
The way I visualize it is that as soon as the drag-link moves out of horizontal between the end of the pitman and the steering arms the effective length of the drag-link starts being different (meaning the distance between point A and point B changes). As you described, the rear pivot point moves down (or up) in an arc while the front pivot point basically remains moving in a relatively flat linear motion moving from static to forward during droop to rearward as it moves into compression. Nevertheless, the wheels in a moving truck are seldom ever pointing in one direction for very long which helps to negate the feel of the bump-steer even more.
Regardless of whether it can be eliminated completely or not, it can be reduced to negligible amounts by keeping the drag-link as level as possible no matter the amount of lift. However, as the lift increases the returns diminish because the components involved lose strength very quickly assuming the loads that are placed on them by the resulting very over-sized tires that are commonly the reason for the ultra-tall lifts in the first place.
And I completely agree with the crossover idea, anyone familiar with solid coil sprung front ends understand the sideways movement that setup brings into the equation. Leaf springs would break or bushings would quickly be destroyed with that kind of constant flexing.
Not arguing here, just trying to see if we or I am on the same page. The science may say I'm wrong, physical experience says I didn't have any perceptible bump-steer with a six inch lift, 4" steering arm, and 2" dropped pitman.
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The spring cycle being talked about is one of the reasons why longer shackles exist for the front. Its quite common and possible that with lifted springs the spring itself can and will hit the frame.
With a 6" lift or taller this is a real possibility. However, the reality is that even when I rock crawled with my truck in Colorado I could not compress or droop my suspension enough to cause that. At least with a SWB the weight of the rear of the truck allows the frame to flex first, then the rear wheels lift off the ground because they are short and light (even with a 14 bolt). I can't say what a LWB does in this regard because I have never wheeled in a LWB truck. I know I had my truck so twisted up the front side of the box had about four inches of it hanging outside the cab line (with no body lift). Maybe the shocks were the limiting factor, I don't know. Going slow is different from jumping the truck however. Mine got jumped once by a buddy. He broke the front driveshaft is all. I didn't see it happen but the group told me he got about five feet of air under the front tires. The rear not so much because he had a thousand pounds of monster truck tire in the bed. That's what I get for being the nice guy and lending my truck out so the monster truck with the flat tire could get back to camp.