Hello. I am trying to figure out if running a half inch smaller than stock tire diameter will create problems with things (like drive train internals) spinning too fast. I am trying to put on 255/60 18's and someone said it was a bad thing to run smaller than stock. First thing I thought of was y'all. Thank you for any help.
Running smaller tire diameter and negative effects on suspension and drivetrain internals
- Thread starter John T.
- Start date
Mooseman
Moderator
If going to a smaller diameter tire, I don't think it would cause extra wear or anything like that, however, it will increase fuel consumption if you do mostly highway driving. It may help a little with city driving. Basically you are doing the same as changing to a higher numerically gear (i.e. from 3.42 to 3.73 gears).
But, the size you are proposing is actually LARGER than stock. The stock size is 245/65-17, which is 29.5" and the 255/60-18 is 30". So going to a larger tire will decrease RPM. When going 60 MPH on the speedo, you will actually be going 61 MPH.
Reference:
tiresize.com
If you want to go to an 18" without changing effective gearing and speedo reading, you could go to a 245/60-18 which is almost the same size (29.6") as the original tire. That is also the size on GMT360's that came with 18" tires.
But, the size you are proposing is actually LARGER than stock. The stock size is 245/65-17, which is 29.5" and the 255/60-18 is 30". So going to a larger tire will decrease RPM. When going 60 MPH on the speedo, you will actually be going 61 MPH.
Reference:
Tire Size Comparison
Tire size comparison the easy way. Use our tire size comparison calculator to compare diameter, width, sidewall, circumference and revolutions per mile.
If you want to go to an 18" without changing effective gearing and speedo reading, you could go to a 245/60-18 which is almost the same size (29.6") as the original tire. That is also the size on GMT360's that came with 18" tires.
Uhhh....I started reading some of the other tire info posts and see now that I probably should have stated I was running one inch thick adapters that change it to the full size wheel pattern. I also have a Belltech lowering kit that drops it quite a bit from stock. I have NOT swapped/flipped the upper control arms yet as I am waiting to afford a brand new one for driver side since I just replaced the worn out pass. side. The wheels on it now are 20" aftermarket that came off a Yukon. Rubber is 275/45 Proxes ST's. that are severely worn on front inside shoulders. Wheels I want to put on are 18x9 with 52 mm positive offset for the adapters. My purpose in going down in wheel size is to try and recapture some of the original ride quality by adding sidewall but admittedly, I have very limited knowledge and budget. Most sincere apologies if this was crucial info as I'm not used to asking questions on a forum. Thanks once again for the help though. Please let me know if I should add more info. I'm going to do the thing where I describe my truck and mods in my profile later today. Thanks again!!
Mooseman
Moderator
I'm not up on full size wheel swaps so I can't help you there. You might have to go through the whole wheel and tire section to find info.
