Speedo fix for different tire height without a tune?
 

Just wondering if anybody knew of a way to fix the speedometer after changing the wheel and tire height. I am running about 1" shorter front and back and mph is a bit off. No TC system issues though since the height stagger front to back is near stock. Thx in advance.

Unfortunately no. Speed is measured electronically by wheel and transmission sensors.

Thanks anyways!

You could buy HPTuners and the credits required to unlock the ecu, but that would be a pretty penny just to adjust the speedo yourself. Also, when I adjust mine to the autox tires the cruise control stops working. It seems to be confused by the extra RPMs for the speed I'm doing. No TCS issues though. YMMV as the ZL1 and 2.0T are totally different cars.

If you did this for speedo fix, would that be registered as a tune by the ECU?

If so, seems like a bad idea to void warranty to fix speedo :-)

I'm not entirely sure how HP Tuners works, it seems much faster than SCT or Cobb that I've used on other cars, but I can only imagine it would show up as being recently flashed should someone check.

I personally wouldn't do it just to adjust the speedo, but it is an option.

if the ECU is flashed for any reason, the dealer service can tell. Their GM Tech machine can detect it.

Dang; didn't even think about that. Changing my 20s out for some OEM Z/28 wheels (19") tomorrow...

I believe in your case, if the tires them selves are the same as the ZL1 1le your speedometer will not be affected !

Best option is just use GPS to measure actual speed vs indicated and note the difference (it’s a fixed percentage). Use waze or other navigation is an easy way. Best way to tell actual speed so you can really know how far off you are

My suggestion as well. When I GPS'd mine it was dead-on with the car and I was on a shorter tire (305/30 > 285/35) not a huge difference but shorter. assuming too that GPS was accurate.

My girls jeep with 22"s/35" tires is off by 4mph (faster).

When I first got my autox tires (305/30-19 compared to 275/35-20 for daily) I knew going in there would be a 5% difference. So 3 mph at 60, 4 at 80 etc. It's not too difficult to account for once you've figured it out.