can SLIGHTLY shorter or taller tires in the rear comapred to the fronts really freak out the ABS/TC system?

Its not 4wd, there is no prblm.

Its not 4wd, there is no prblm.

but there is when the wheel speed sensors dont read the same front to rear. thats how the traction control system works. i was just wondering what kind of tolerences there were in the system before it started causing problems..
1/2" tire hieght difference acceptable, 1"? etc..

but there is when the wheel speed sensors dont read the same front to rear. thats how the traction control system works. i was just wondering what kind of tolerences there were in the system before it started causing problems..
1/2" tire hieght difference acceptable, 1"? etc..


My wife blew both rear tires - yes she backed up over a blow out strip -cleaning warning not to back up.

We put on two spare donuts (good samaritan felt sorry for my wife) and the ABS light came on after about 30 miles. ABS light was off when she picked up the car, after two new tires. Has not come back on - almost a year now.

Not sure if related, but that's my story and I'm stickin' to it!

I think that if the putting 2 different size wheels would cause the light to come on because the computer would see them as turning at different speeds.

im tellin ya, there no problem. I run 60's up front, and 40's in the back. no problem.

traction control works off of the rear wheels, if one is spinnin faster than the other.

im tellin ya, there no problem. I run 60's up front, and 40's in the back. no problem.

traction control works off of the rear wheels, if one is spinnin faster than the other.


thats great and all, but give us the important numbers too.. you just gave us the aspect ratio of the tire..
FWIW i'm running 275/40/17 rear, 245/45/17 front.
they should be the same height, but since they are different manufacturers, that doesnt mean they are.

and my question is concerning the part where, what if they arent the same hieght? how much tolerance is acceptable to the computers..

just an fyi,

t/c runs off both front and rear abs sensors,

think about it,if you have both rear tires spinning equally the system has to judge off the fronts too,otherwise the system would say,"well,everything looks peachy" and you would spin all day long

who need ABS or T/C

I ran different height tires on my Mark VII, didn't seem to make a differance, but it doesn't have traction control, only abs. My VIII I stuck with same size all around. Sorry it doesn't help much.

thats great and all, but give us the important numbers too.. you just gave us the aspect ratio of the tire..
FWIW i'm running 275/40/17 rear, 245/45/17 front.
they should be the same height, but since they are different manufacturers, that doesnt mean they are.

and my question is concerning the part where, what if they arent the same hieght? how much tolerance is acceptable to the computers..

Running 215/60-16's in the front & 225/60-16's in the rear no problem. Ran 235/60-16's in the rear for a while, no problem. The T/C will brake the spinning, loose, wheel up to thirty MPH to help get traction, braking a front wheel will not really accomplish anything. Believe you are all right in either case. Ed :cool:

would the tires being shorter than stock really throw off the system? all 4 are spinning faster than the computer thinks they should be, would that be an issue? i know people are running 245/45/17's...

I'm not sure but I do know the Gen 2 traction control is a lot more advanced than the Gen 1 system. I would like to know the answer to this as well since I have stock 225/60/16's all around right now and I would like to put 255/50/16's in the back...

just an fyi,

t/c runs off both front and rear abs sensors,

think about it,if you have both rear tires spinning equally the system has to judge off the fronts too,otherwise the system would say,"well,everything looks peachy" and you would spin all day long

But since its not a locker, they wont spin equally. and one will constantly be slower thanthe other, untill they both have traction again.

But since its not a locker, they wont spin equally. and one will constantly be slower thanthe other, untill they both have traction again.
this system still works with limited slip and what not,



and trust me on even open rears can slip equally on snow and ice,

the real question none of us can answer so far is how far of a difference one can go in front to rear tire size before a problem occurs,there obviously is a room for difference in size i think,if there was no tolerance for different sizes the system would probably engage even when just making a left or righthand turn,as one tire would be turning faster/slower than the other(more proof the system reads the front abs sensors,as they will each be turning different speeds when cornering also.)

hopefully someone can answer this,but it might come down to trial and error.

I'm not sure but I do know the Gen 2 traction control is a lot more advanced than the Gen 1 system. I would like to know the answer to this as well since I have stock 225/60/16's all around right now and I would like to put 255/50/16's in the back...

That would put the rolling difference at 2.2% different, I would seriously doubt the ABS/TC control system is programmed to react to such a small difference. Variations in tire size, tire pressures, etc can easily add up to that much. I would think that you would be ok up to a 4-5% difference. At least that is where I would put it if I designed it.

There are plenty of people, including me, that have run slightly shorter tires with no problems. I don't know about the front and rear being different sizes though.

There are plenty of people, including me, that have run slightly shorter tires with no problems. I don't know about the front and rear being different sizes though.

Smaller or taller tires will have zero effect on ABS/traction control if they are the same size on all 4 corners. If is the difference between them as the sensors compare the fronts to the rears for t-c, as I wrote above, it probably needs at least a 4-5% difference in diameter (which means the same percentage in circumference) between the front and rears to throw the systems off.

NO differences whatsoever. I have 35's on the back and 40's on the front and I have been staggered for YEARS with nothing at all going hay wire.

These cars aren't that sensitive.

ok. thats what i was thinking too, i couldnt see them being that sensitive, but then again i couldnt see someone in their right mind deciding that was a good place for an oil filter either..

check my other post, http://www.lincolnvscadillac.com/showthread.php?p=163827#post163827, thats what prompted this question..