Thread: Correcting for a shorter tire

I know you're not supposed to for "reasons".

But I'd like to run G force sports on my stock wheels.

Namely because I'm too cheap to buy new wheels and would like more traction.

thus i'd be forced to run 245/50r16.

This is 25.65 unloaded versus 26.63 unloaded for my stock tire size of 225/60r16.

Ignoring the difference between unloaded and loaded for now, my main concern is not the VSS signal and the speedo.

That can be easily taken care of via HPT.

However, what I am concerned with is the ABS system.

The following information is based on our wiring diagrams and how the system behaves in GM trucks. I have yet to find information on how the system operates in our cars, however I can't imagine its much different.

Namely because the EBCM receives the wheel speed sensor inputs directly and converts them to speed. A tech 2 scanner would read the speed, not a VSS style pulse which the wheel speed sensors emit.

It appears the PCM then sends the vehicle speed to the EBCM via UART and the EBCM then decides what to do.

It also appears this can be corrected in the EBCM, but only with a tech 2 scanner.

Now this is fine and dandy if I was going to leave this size tire on the car all the time, but come winter time I might want to go back to stock size so I can run a more reasonable winter tire.

Finding a tech 2 scanner every time I wanted to make this change would be rather impractical and possible costly.

It seems buying 17" wheels and running 225/55's instead would be a much easier route.

Turns out the 17's in g-force sports are $9 less per tire. Go figure.

Why are all of the cheap wheels ugly?

http://www.thewheelgroup.com/wheel.asp?b=11&p=382

For $90 a piece.

Also found this interesting: http://tomboynton.com/GMnetworks.pdf

The ABS is exactly that, anti-locking and that's pretty much the only time it engages is when a wheel is locked or near it and with the variances in the wheel bearing OHMS just from a ambient temp change I'm betting there is quite a bit a wiggle room.

Oh and I just sold a set of the 06-07ish Pontiac Torrent wheels that I had on my wife's Grand AM They look really good for a 17" IMO and I bought the set of 4 with nice GM chrome lugs for $120

You can't seriously be doing a tire changeover twice per year.

As you have implied, all-seasons are no-season tires.

You can buy a 2nd set of 16's locally on Kijiji for under $200. Maybe thats an option for you.

get proper wheels son. and get summer tires for grip.

i use summer tires year round

**** ABS

The abs does use pulses, but I'm mainly saying a lockup or almost lockup is gonna do the same thing... It may want to try and lock up faster on you and engage sooner just cause of the smaller tire but I think it would work fine.



And I do wheel changes twice a year, I even built a tire rack on top of one of my shelves to hold all my wheels and tires. Both seth of tires I have are all seasons though, Pirelli scorpions on my 18"s 235-50-18(over sized) and then stock replacement insignias or whatever on my fat fives. Bout to go get the fattest set of used 16" tires they have down the road for my strip wheels, drags or anything grippier would grenade the trans

Matt... it's not going to make enough of a difference to effect ABS on you.

yeah, it won't make a difference. i ran that exact tire size on stock wheels forever. so did a lot of people.