33x9.50's on a C-10?

[Dieselfume]

Howdy,
Recent camping trip provided me more motivation (slightly damaged running boards) to create a bit more ground clearance.
87 C-10 right now with stock 225's. Been planning on putting bigger tires on it, but motivated to do it sooner (along with a rear axle swap, see post under the suspension section 14 bolt 5 log conversion question).

From what I have found off this site, the consensus seems to be 31x10.5 is the most that will fit on a stock C-10 and that 33's do not fit without lifting.  However, I've noticed the majority of 33's are 33x12.50. I see that there are also 33x10.50's, and BFG makes ATs in 33x9.50. Wondering if anyone has tried the 10.50 or 9.50 on to see if it fits and if it rubs?  My guess is the previous statements were about the 33x12.50 and that they are wide enough they rub when turning or turning under compression. (not to mention 12.50s shouldn't go on 15x7's)
Using a tape measure and eyeballing it, the diameter looks not to be the problem stock ride height.
Thoughts, concerns, questions?
Thanks! 

[Irish_Alley]

the width might make a difference on the inside frame rub but I'm still thinking it will rub there and almost certain it will rub the outside fender. the tire width difference between a 12.5 and 9.5 is an overall 3" but its only a 1.5" on each side i don't see that 1.5 making that big of a difference in rubbing

[Dieselfume]

Thanks for the reply Irish.  After doing a bit of testing, I believe you are right, if it's going to rub anywhere, probably the lower front and rear fender corners, and maybe some on the inside fender.

After being out in the woods again and having another few mild no damage scrape the bottom of the truck encounters, I decided to rig up a bit of a test (I'm a test engineer, can't help myself). I'll describe it for everyone's benefit.

Took some tire specs off the web and made some L shaped plywood templates. The inside of the L is the roughly the profile of the 225's I have. The outside is per measurements off of tire rack for 33x12.5, 33x10.5, 33x9.5, and 31x10.5, 4 templates total.  Knowing the worst case would probably be turning with the suspension compressed, I set the truck up in that configuration the best I could. I started off driving the L front and the R rear onto some ramps made out of 2 layers of 2x8, compressing each corner 3". While driving up on the ramps, the R front I places two pieces of sheetmetal with grease between em so turning would be easy.  Next I jacked up the R rear to the limit of travel on my jack and put a jackstand under the front eyelet of the R rear spring (so the R rear corner would no longer compress the spring if I jack the opposite corner up). Third, I jacked up under the L front lower A arm to the limit of travel on my jack.  The result was 7" of air under the L front, and the R rear about 4", so the same as 1 tire jacked up 11". You can really notice the frame twist here, cab to bed mismatch about 1 or 1.5".

Test results:
The results suggest that I could very possibly get away with 33x9.50's, and maybe even 33x10.50's, although I'll probably stick with 9.50's because of other factors.  The tight points up front are first the front lower fender corner at 1/2 steering wheel turns from center (of 1.5 steering wheel turns to full stop). Second would be the rear lower fender corner to about 6" up, also about 1/2 turns.  Third would be the inner fender at full steering travel, 1.5 turns.  Fourth would be rubbing the shock, but only for a 12.50.  Overall the clearance from the outside fender and inside fender are noticeably reduced between the 12.50 and the 9.50. Where the 12.50 hits by about 1/4", the 9.50 seems to clear by 1/4-1/2".  The fender top at this suspension compression is about 1/2-3/4" clearance. More clearance if the tire is turned straight and it was a 9.50, tire would appear to go inside the fender. The 12.50 wouldn't be able to do this, and the 10.50 would be real close.

On the rear axle, no clearance issues due to diameter. In the compressed R rear, the 12.50 template would rub on the sidewall on the inner fender with stock wheels and backspacing. The 10.50 would fit ok, but only 1/2-3/4" clearance for chains. The 9.50 provides more room for chains, about 1+" clearance. Slightly more room available when truck is level, about another 1/4".

Sources of error:
I think my templates were probably a bit square, and the template corner may stick out more than actual tire. A conservative error.
The other point of error is not reaching full suspension travel. This did not seem to be an issue for measuring clearances on the outside fender front and rear, as

Conclusion:
Carefully bend in the closest clearance areas (front lower corner outside fender, top inside fender edge) and eventually head to the tire store for an actual fit check. Inside fender rub would not be very harmful, but hitting the outside fender lower corners or fender top would.

[malibu795]

does this help at all? these are 315/75/16s. rims has 5.125" back spacing and a 6.5" wide. i have put 17x9 wiht 5.5" backspacing and not rubbed.. will get pictures

[Dieselfume]

Good pictures.
315/75-16 calculates out to 34.6", so 35x12.40-16, and I presume that's a stock ride height K20. I imagine the clearance is a bit closer at a part turn with the spring compressed, but it certainly looks like good clearance with the front spring with that backspacing.

C10 being a different suspension configuration and ride height makes the clearances a bit closer. Your pictures do perhaps suggest my plywood templates were a bit oversize at the corners and that I may have more clearance than I thought.  Have yet to go to the tire shop for a fit check. I have another vehicle that needs tires first, and it is the daily driver.

[Dieselfume]

Well, finally got around to actually test fit a used 33x10.5 Thornbird TSL. rear axle plenty of room front to back, closest spot is the top of the fender, but if that corner squished enough it would just sneak inside. And on the front I'm pleased to say that there is 1" clearance at the tightest spot, and that is with the front corner jacked up, and I haven't used a rubber mallet yet to provide any additional insurance. I had the truck jacked up so far in the corners that I was nearly on 2 wheels. Still had 3/4" before the bumpstop, so I drive out into the little drainage ditch in the front yard. Was able to get the suspension articulated within 1/4" of the bumpstop. Front and rear still have ~1" clearance, but I was a bit closer vertically to touching the inside fender, ~1.5". The thornbird specs out 0.3" smaller dia than the BFG, but it also specs out wider section width. This tire is pretty worn, so add 1/2" more for actual tread depth.
So, looks like I have 33x9.5 BFGs on the shopping list. (once I'm done putting new shocks and brakes on the truck).