Rear tire size/limp mode?
 

Got a hold of a set of " toliman" 16 " lightweight wheels to put together a drag wheel package. Before ordering a certain size tire, I had some questions you guys that drag may know the answers. My thought was to order a tire size that is shorter than the tire on my srt6 now, so the car reacts like it has a lower gear ratio in the differential. Was reading other threads on changing gear ratios and that it would put the car in limp mode if the tcu wasn't altered. Would a smaller ttire put the car in limp mode? I plan on going from the stock 26" height to 25.xx. How small can I go without the Ecu thinking something is out of whack? Any and all help would be appreciated .

Re: Rear tire size/limp mode?
 

I don't have an exact answer BUT if you go with a lesser diameter in the rear you should try and do the same with the front. The trick is to keep, more or less, the same percentage of change front and rear so the sensors don't send confusing information to the PCM. You have some wiggle room but if you get too far off, front to rear, you'll have trouble.

I run 18 inch rims for road racing, 245/35/18 and 275/35/18 with no trouble. Stock sizes on the street.

Les

Re: Rear tire size/limp mode?
 

Thanks for the quick response! The tires I'm looking at, nittos are 25.68 tall. Can I get away with it without changing the fronts? Is there room to go smaller. Thanks

Re: Rear tire size/limp mode?
 

NO it will not set off the limp mode,,as long as you are going somewhat straight, I mean don't try to drift. I in all my tire testing I tested 205/50-16 24.1" tall , BE CAREFUL ALL YOU DO IS SPIN.
the best and only tire size you should use is a 255/50-16 drag radials if you are using 16" rims,, any thing smaller will spin also. there are 17 18 and 19 drag radles,, also i would not go smaller than a 25.7 tall and not taller than 26.2
jim

Re: Rear tire size/limp mode?
 

Thank you Jim and Les. This is good information to work with. What do you think caused the smaller tire to loose so much traction? To much torque for the smaller tire, less contact? I am assuming these smaller tires are drag radials you tried? I'm running hankook v2 now with 1.8+ 60', so they are working well. Was looking for the lighter wheel and shorter tire to achieve a quicker 60'. I am an old school drag racer, we used to do it with taller or shorter gears.

Re: Rear tire size/limp mode?
 

all my testing was street tires on the street, as i was checking ratios, and limp mode ,like what you ask,,
always my drag radials and drag slicks were 255/50-16 and is 10.0 wide and 26.0 tall. the drag slicks ,with radials on the front ,,,don't do it ,makes the car wonder, and at 130 that is one of the last things you want., My street tires are hankook 275/35-19 at 26.6 tall,, a lot of people run 285/35-19 --26.9 tall street. the only thing i found in a 25.68 is a 245/50-16 which is 25.7 tall but only is 9.6 wide.
here is nitto website I found a 245/ 50 16 is 9.6 wide,, 4.8 sidewall,,25.7 tall
NITTO Extreme Performance NT555R Drag Radial - 245/50-16


here is from Micky thompson which is what I use. M T website
90000000996 3793R P255/50R16 26 X 10.50R16






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