[4 BKT VET]

What happens if I run a 25.7" tall tire in the front and a 27" tall in the back?

 

[LYNMUP]

If the computer senses a difference in wheel speed it will apply the T/C measures. Turn off the T/C button and you should be O.K.

 

[Good 2 go]

There may be an ABS issue also.

 

[MeanGoat]

If the computer senses a difference in wheel speed it will apply the T/C measures. Turn off the T/C button and you should be O.K.

Don't think so. If both rear tires are the same size (since they are the gripping tires which would be controlled by T/C) I don't think there will be an issue since no diff in wheel spin will be occurring.

I can't possibly swallow that a front vs back tire spin calculation is taking place which would sense a difference in wheel spin from front to back.

Don't know about the ABS.

 

[LYNMUP]

I received paperwork form my dealer explaining the T/C system. When the ECM senses a difference in wheel speed from the front to rear tires, it sends a signal to the ECM telling it to kill the power and apply the brakes to the wheel that is spinning quicker. That is how the system is designed to work to prevent the car from spinning out of control on slippery surfaces. So yes! If the rear wheels are "larger" they will turn at a different speed and "possibly" effect the T/C system. But try and see, it may not be enough difference to affect it.

Good luck!

 

[bergenfelter]

You will definitely have ABS issues. The ABS system must see all four tires running at the same speed, OW the system will throw a fault. Ever see one of our rides on a chassis dyno? First thing the car does when you release the dyno drum is the ABS system throws a fault.

 

[4 BKT VET]

Were talking less than 5%, aren't we?

 

[LYNMUP]

It may be very minor but I would like to see if there would be a difference enough to affect it. I would love to put some big meats on the back for awsome hook-ups at the red light. Get with your local dealer mechanic and pick his/her brain about the T/C system. Make them work for their money!

 

[4 BKT VET]

Test 1 results.

Road Test results (T/C on);
Ran a 245/45/17 on the back (25.7") and 245/40/17 on front (24.5).
Drove surface streets normal, no issues or DIC warnings.
Drove freeway to 65++ normal approach, no issues or DIC warnings.
Launched car at 2000 RPM, slight tire spin, DIC displayed T/C but hooked right away.
25MPH in 2nd and jumped on it during a left turn, drivers tire very slight spin for a split second with T/C warning. Barely more tire spin than with all 4 tires the same.
Braking, couldn't find any water, otherwise no different.

 

[LYNMUP]

Thanks for being the guinea pig for this! Glad it worked. How much is your speedo off and did you have any clearance issues? If you get a programmer, you can correct it to normal.

 

[4 BKT VET]

Thie week we hit the rollers. Next week we do 245-45-17 front and 275-40-18 back. After the Corsa sport goes in, we hit the rollers. Allready did $8 CAI.

 

[JMVorbeck]

I received paperwork form my dealer explaining the T/C system. When the ECM senses a difference in wheel speed from the front to rear tires, it sends a signal to the ECM telling it to kill the power and apply the brakes to the wheel that is spinning quicker. That is how the system is designed to work to prevent the car from spinning out of control on slippery surfaces. So yes! If the rear wheels are "larger" they will turn at a different speed and "possibly" effect the T/C system. But try and see, it may not be enough difference to affect it.

Good luck!

That is correct. It is a BOSCH 3-channel traction control system. 1 channel in front, 2 in the back (L&R). The input signals are compared to each other to determine wheel spin.