differences in tire size
- Thread starter warmpancakes
- Start date
sytyguy
Moderated User
Re: differences in tire size
Words to live by.
I did this back in 1999 with 1-2 psi changes in pressure until I found the best results. I had a compressor in the field with me and just kept trying runs, letting the tires cool, checking temps, and adjusting pressures. All runs were made under controlled variables with tires being the exact same temp (as verified by temp probe), same distance, and same mph. I was pretty meticulous about the test, because I actually cared back then
(I had only had the truck for a year at that point).
When you own the road that you test on, it makes it easy to do that kind of stuff. :lol:
Hood
warmpancakes said:
Words to live by.
protosy said:
I did this back in 1999 with 1-2 psi changes in pressure until I found the best results. I had a compressor in the field with me and just kept trying runs, letting the tires cool, checking temps, and adjusting pressures. All runs were made under controlled variables with tires being the exact same temp (as verified by temp probe), same distance, and same mph. I was pretty meticulous about the test, because I actually cared back then
(I had only had the truck for a year at that point).When you own the road that you test on, it makes it easy to do that kind of stuff. :lol:
Hood
Re: differences in tire size
cool. i knew someone did it. 8 years ago is a while, i guess my memory just doesn't work good that far back.sytyguy said:I did this back in 1999 with 1-2 psi changes in pressure until I found the best results. I had a compressor in the field with me and just kept trying runs, letting the tires cool, checking temps, and adjusting pressures. All runs were made under controlled variables with tires being the exact same temp (as verified by temp probe), same distance, and same mph. I was pretty meticulous about the test, because I actually cared back then
When you own the road that you test on, it makes it easy to do that kind of stuff. :lol:
Hood
Treymen
Donating Member
Re: differences in tire size
You guys make me nervous with this stuff. My tires are 4 rotations per mile different. 25.6 in the rear and 25.7 in the front. I have 2#'s less air in the front to compensate a little more.
Also, doesnt the weight , front to back make a difference as well. The front of the truck weighs a lot more than the rear. Thereby flattening out the front tires, changing their actual height. Right????
You guys make me nervous with this stuff. My tires are 4 rotations per mile different. 25.6 in the rear and 25.7 in the front. I have 2#'s less air in the front to compensate a little more.
Also, doesnt the weight , front to back make a difference as well. The front of the truck weighs a lot more than the rear. Thereby flattening out the front tires, changing their actual height. Right????
sytyguy
Moderated User
Re: differences in tire size
Ummmm.....yeah it does. That's the whole point of the aforementioned test that I did back '99.....to see just how less stress the driveline sees when rotational diameter is equalized front to back. It's significant and why, to this day, I ride with more psi up front than in the back.
warmpancakes
New member
Re: differences in tire size
Tires have been on for 2 years with zero issues, There has to be tolerances built in, 2 tires from the same mold can vary in size driving straight down a road can have variances due to crowns in the road , changing lanes can affect the size of a tire, turning a corner,if it was critical on awd cars they would have warnings or notices about it , Im willing to assume the tolerance is bigger than some of the differences guys here run, These are trucks built for the average owner who will do things the cheap way if they get a blow out they will buy one tire not all 4, Engineers have to plan for these people as they are 99.9999999999999% of car owners who look at vehicles at a point a to b tool, were not curing cancer here
Tires have been on for 2 years with zero issues, There has to be tolerances built in, 2 tires from the same mold can vary in size driving straight down a road can have variances due to crowns in the road , changing lanes can affect the size of a tire, turning a corner,if it was critical on awd cars they would have warnings or notices about it , Im willing to assume the tolerance is bigger than some of the differences guys here run, These are trucks built for the average owner who will do things the cheap way if they get a blow out they will buy one tire not all 4, Engineers have to plan for these people as they are 99.9999999999999% of car owners who look at vehicles at a point a to b tool, were not curing cancer here
warmpancakes
New member
Re: differences in tire size
just some quick findings
Audi As published in their vehicle owner's manual, "rolling radius of all 4 tires must remain the same" or within 4/32-inch of each other in remaining tread depth.
Porsche Cayenne within 30% of the other tire on the same axle's remaining treadwear.
Subaru Within 1/4-inch of tire circumference or about 2/32-inch of each other in remaining tread depth.
these are way more advanced systems that our old school mechanical systems
just some quick findings
Audi As published in their vehicle owner's manual, "rolling radius of all 4 tires must remain the same" or within 4/32-inch of each other in remaining tread depth.
Porsche Cayenne within 30% of the other tire on the same axle's remaining treadwear.
Subaru Within 1/4-inch of tire circumference or about 2/32-inch of each other in remaining tread depth.
these are way more advanced systems that our old school mechanical systems
warmpancakes
New member
Re: differences in tire size
I think boost launches and general "hard " driving has alot of the affect on the life of the VC here as some people here are very very rough on these trucks and ask some of the parts to do things they were never designed or intended for, as far as I know our transfer case is just a carry over from the astro/bravada that were designed to get the kids to soccer and school, not for launching at every traffic light
I think boost launches and general "hard " driving has alot of the affect on the life of the VC here as some people here are very very rough on these trucks and ask some of the parts to do things they were never designed or intended for, as far as I know our transfer case is just a carry over from the astro/bravada that were designed to get the kids to soccer and school, not for launching at every traffic light
93TyphoonPacetruck
Member
Re: differences in tire size
Does having different size tires in the front and rear only effect the transfer case? Or would it also have an effect on the differentials front or rear?
Does having different size tires in the front and rear only effect the transfer case? Or would it also have an effect on the differentials front or rear?
sytyguy
Moderated User
Re: differences in tire size
The VC "makes up" for the difference. No abnormal wear should be noticed on diffs from differing tire sizes.
93TyphoonPacetruck
Member
Re: differences in tire size
Cool thanks,just making sure this wasn't the culprit in my old SY having the front diff go to shit on it.
Cool thanks,just making sure this wasn't the culprit in my old SY having the front diff go to shit on it.
Raist103
Engine Killer, iPhone Killer, Lawnmower Killer
Re: differences in tire size
last Pittsburgh meet i drove the sy out with 245 45 18 front and 315 30 18 rears and my t case didnt even make it out there. did the tire size have anything to do with it? dont know but ill be as close as possible from now on.
last Pittsburgh meet i drove the sy out with 245 45 18 front and 315 30 18 rears and my t case didnt even make it out there. did the tire size have anything to do with it? dont know but ill be as close as possible from now on.
wheels
Donating Member
Re: differences in tire size
I'd say it did. There's a 4.65% difference in diameter in that combo.
I'd say it did. There's a 4.65% difference in diameter in that combo.
7dhamper
New member
Re: differences in tire size
I got 325 / 30 / ZR19 rears and 255 / 35 / ZR19 fronts General Tires for a great price from Tire Rack. I'm scared to run them cuz the rears are so much taller. Even with max pressure in the front and like 25 PSI in the rear they still look iffy to me. I figured I'd bolt the rears on my S-10 and smokem for a while to knockem down some. Maybe it's cuz the rears have a higher weight load rating that the sidewalls stay so stiff at low PSI. I wish I could just hit 4X4 off but there's no button on my dash like my old Jimmy had. Considereing yanking AWD transfer case and selling it to replace it with on the fly unit but I know the split will go from 70% / 30% to 40% / 60% which I don't mind for snow and would be worth it to do 2WD burnouts in summer. Any input from youguys with this mod would be great.
I got 325 / 30 / ZR19 rears and 255 / 35 / ZR19 fronts General Tires for a great price from Tire Rack. I'm scared to run them cuz the rears are so much taller. Even with max pressure in the front and like 25 PSI in the rear they still look iffy to me. I figured I'd bolt the rears on my S-10 and smokem for a while to knockem down some. Maybe it's cuz the rears have a higher weight load rating that the sidewalls stay so stiff at low PSI. I wish I could just hit 4X4 off but there's no button on my dash like my old Jimmy had. Considereing yanking AWD transfer case and selling it to replace it with on the fly unit but I know the split will go from 70% / 30% to 40% / 60% which I don't mind for snow and would be worth it to do 2WD burnouts in summer. Any input from youguys with this mod would be great.