Wheel Correction
 

Hey guys, I recently up'ed my rims from 16's to 17x9.5's and I know my speedometer is off. I rolled with my sisters WS6 and her at 80 is me at 90 so I'm really off. Wondered if you guys knew a place I coudl go to to correct this. Or tell me how to do this on my own. Yeah sorry if I should've just searched this, but I thought it would be more helpful if I posted it in a western thread. Thanks guys.

You'll have to reprogram the PCM for the different tire diameter. LS1edit, HPtuners or one of the handhelds (HPP, Predator) will allow you to do this. Dealer might change this (for a fee) for you also.

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Wow you are off by 10 miles, and you got 17. I have 18 on the back my Z28, and I am not off that much.

Its under gear settings. Tire height for that size is 25.63".

not 100% true, we have seen many different tire companies with different heights, so we just measure it to be 100% sure..

What size tires are you running??

Yeah, it's all in the tires...

I upgraded from 16s to 17, with no change and now I'm up to 18s and again... no change. Maybe a mph but not 10(!?!?)

Get a HPP3 and reprogram or just watch your speed. :) :drive:

Yup....I went from 16 to 17 without problems. Now Im going 19 with 275/30...my speedo will be just fine...find proper tires for your 17.

Wait, so your tire diameter is actually smaller with the 17's? (Smaller tires will make your speedo read high)

The difference between 245/50/16 (stock) and 275/40/17 is very minor, not enough to cause a noticable variance. I don't think it really matters what tires you run, tire brand might cause a 1-2mph difference. Now if you choose a nonstandard tire combo then you might see a difference... even the 315/30/18s I run are close enough not to require tuning on a camaro, although since I have them on my vette right now I had to dial it in.

If his speedo is reading that high with 17s he's probably running something like 255s instead of 275s.

Very simple to find the "actual" tire diameter, call the tire shop where you got the "tires"..., and ask them to give you the "overall tire diameter" from their info they DO have at their shop (or if they are to stupid to find it :eek2: , they can call the supplier who sold the tires to them and get it!).

Changing a tires overall "outside" diameter from stock MOST assuredly DOES change the "speedo" read out...electric or manual (cable) drive!

Most tire manufactures have a website today (for this very reason because most tire shops are "lazy", or stupid, or BOTH!!! :judge: ), where you can get more "true info" than the "bullshit artist" at the tire store tries to tell you.

Why am I so critical of these people??? I have been in the industry 30 years and there are not but a "handful" that really know their ass from 3rd base!!! Especially today, when all they try and sell is cheap "knock off, wanna be" brands from places I have never heard of... even in school!!!

Do yourself a favor, and read the info available and... try and drive the same car as yours with different tire brands on it. You'd be amazed at the difference in ... "black, round, and got a hole in it" can have!

And "yes", most every tire manufactures tire size (275/40R17 example) IS different in dimensions...width and height...and it's LEGAL!!!

Good luck!

"We have a thousand reasons for failure but not a single excuse."
- Rudyard Kipling

What is the speedo difference from 25.65 to 25.44? When you are going 65 it reads 64.5... half a mph...

Tire brands aren't going to make a 275/40/17 vary more than maybe .1 to .2

That being said, you get what you pay for. If you drive your car hard, don't put cheap tires on it. When I picked up my vette, it had Kuhmo Ecstas on the back. Worst tire I have ever seen for lateral traction. I about killed myself going down the hill on the 67, got it sideways at about 120 in the last long lefthander at the bottom of the hill. I've done that turn harder than that in my camaro, but it had BFG TA/KDs. Fortunately I had my other set of wheels ready which I put on, and the Pilot Sport PS2s are probably the best street tire available imo.

Of couse I would never put a 19" rim on my car unless it was a 19x12 and I was gonna run 345s, cause with a 19" wheel and 245-275 tire is retarded from a performance standpoint.