Don't know if this is the correct section for this, or how often you get this question but I searched for it and didn't come up with what I was looking for.

Anyways, on my friend's Blazer his tires are getting worn as he drives a lot and Uniroyal Tiger Paw's aren't too great in the snow and such even when they're new, last winter we went to the gas station Christmas morning and there was a foot of snow on the ground. Didn't think with the newer tires and 4WD we'd have as much trouble as we did, just about got it stuck and wasn't easy to manuver and not hit a pump, had to did around the front after we stopped so we could get enough momentum to start up again without getting stuck, but that's besides the point.

Anywho, he wants to buy new tires only put the optional 31x10.5/15's that the ZR2's have. The only problem will be the speedo won't read correctly. I know in some cars and trucks they have a speedo gear in the transmission but I figure being all electronic it probably doesn't have that. What options are there to get the speedo to read acurately without an ECU tune? A tune would be very nice but they're not that cheap and he'd like to make other upgrades like intake and exhaust first so he only has to tune it once.

So if anyone can answer, we'd appreciate it, and sorry if it's asked a lot.

 

What year is his blazer?

If it uses a VSS (vehicle speed sensor), the PCM would need to be reprogrammed to correct the speedo.

 

Oh yeah forgot to add that, it's an 04, not sure what all it uses, i'd guess it's the 4L60E. If it needs a PCM tune, i'll tell him to wait and add a few more goodies so he only has to tune it once. On fullsizechevy.com where I often visit, most recommend BlackBear Performance for the custom tune, gonna give it a try on my Suburban after the header install.

 

Yep, that uses the VSS and the PCM corrects it for the tire size & gears. You'll need to get it tuned to correct the speedo for the tires.

 

Good to know, thanks.