Big drag radial tire result in lot of traction but create a problem

[SSDION]

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Join Date:May 2006Posts:22




Big drag radial tire result in lot of traction but create a problem



I have a C7 z06 a8 2015 car. For maximum traction when drag racing, I have install 30.2" drag radial at rear and 26" skinnies on front. I use 18 inch wheel. The car has so much traction at starting line it lift front wheel by 1 inch. I did reprogram speedo and trans with HP tuner but when I drive this car in the street over 60 MPH the computer send this message. SERVICE REAR AXEL All warning light comme on (engine abs,traction control, stability track). Transmission is not shifting well 1-2 and 2-3. I think there is too much difference betwen rear and front tire size and VSS and ABS sensors have too much difference in readings. Speedo is reading right speed when I compare with GPS speed. Do you know a way to adjust TCM so speed of driven and undriven wheel will match ?

Please help me.

[SSDION]

Better picture of wheels and tire

[8850]

Get a pair of Hoosier 315-30-18 drag radials and problem solved. What I have on my 2017 Z06 and no problem with shifting, ABS, etc. HP Tuner does not have the capability to tune for unequal diameter tire problems.

[SSDION]

Thanks for your advice. I try those tire 315-30-18 drag radials before and I spin tire on starting line after a strong burnout. I decide to install much biger tire 30.2" to get maximum traction. Now traction is excellent and good enough for taking mutch more HP and torque. I will not return back to smaller tire. I need to find a way to ajust adjust TCM so speed of driven and undriven wheel will match. Any other idea?

[jsllc]

HP Tuners does not have all of the necessary items. I had to use EFI Live to do this type of adjustment. I have an existing request in to add the required parameters to fix this issue.

[GHuggins]

^^^^ I requested the same thing a few months ago - there are actually the same settings for front tire diameters and differential settings in the calibration that we don't have access to at the moment... Of course I also requested quite a few other things and haven't heard back on any of it, so who knows if it'll happen?

[SSDION]

Thanks for your comments. What is the EFI Live table to do this type of adjustment. How can I REQUEST HPT to add this kind of table?

[jsllc]

The request is in the current queue and has been there. EFI Live has a section for Speedo. Not a table but rather group that allows for entering the correct data needed by the ECM.

[thesubfloor]

If you're spinning 315/30/18 Hoosier drag radials then you're doing something wrong and/or the track prep sucks.

I know this first hand as I use those tires as backups for my 2007 race car (my normal tires are 315/35/17 Hoosiers) and regularly cut 60ft times in the mid 1.3s.