Stock 15" - How Big Can I Go?

[90.GMC.ST]

I might be asking a couple of questions in the coming days, just trying to get all my parts together and want to ensure everything is going to work. I currently have 15" wheels on the truck that are stock. What's the largest size of wheels I can get without having to do a lot of work to make them fit? I'm hoping to get 18" wheels on it, but I'm not sure this is possible without a lot of work having to be done.

Thanks,
Jordan

[davbell22602]

what year and model truck is this?


http://www.mickeythompsontires.com/T...Guide_2008.pdf


http://www.mickeythompsontires.com/W...Guide_2008.pdf

[90.GMC.ST]

Oh shoot, sorry I forgot to mention the main details! It's a 1990 GMC ST that is stock.

Thanks,
Jordan

[davbell22602]

Your sure its 15in and not 16in. I have 90 chevy c2500 with 16in rims.

[90.GMC.ST]

I know for sure that it was factory built for 15's, and I'm pretty sure it hasn't been nodded. I'm going to pick up the truck either tonight or tomorrow and the PO isn't the type to do any modifications. Just by the RPO search on the VIN it came up saying it has 15's as stock wheels.

Thanks,
Jordan

[jb1016]

15s woulda been stock on a 1/2 ton 2wd. You can run 20s, at least, without issues, assuming the truck isn't lowered. I'm running 18s with 255/55s, no problem. I think my wheels are either 8 or 8.5 inches wide. Hope this helps.

And welcome to the board. Be sure to post some pics once you pick it up!

[BIGphillip79]

its not so much the wheels you got to worry about, its tires. You can go pretty big as long as your tires don't get to fat.

[90.GMC.ST]

Okay thanks guys! I'm going to pick it up bright and early tomorrow, hope all goes well. So what all needs to be adjusted as far as brakes and such to accomodate the larger wheel? I'm not to worried about the size of the tire, as I plan on getting lower profile onces compared to the avg tire.

Thanks for the welcome as well as the answers! I'll be sure to post pics as soon as I get the vehicle into my hands!
-Jordan

[BIGphillip79]

With 18s you shouldn't have to change anything on the truck, your brakes and all are fine. Just want to make sure your backspacing on the wheel are correct. Just try them on before you buy them. turn the wheel lock to lock and make sure you got know rubbing around the tire,If it clears your good to go.

[90.GMC.ST]

Really? That's great! Who lot less work than I anticipated! So really, the only thing I'll have to do is something with the speedometer then to properly measure my rate of motion?

Thanks,
Jordan

[ChevLoRay]

For 15's, the SS trucks in '90-92, came with 275-60R15's, on 8-inch wide wheels.

I'm running that tire size on the back of mine with 245-60R15's up front on 7-inch wide wheels.


Oh, by the way

[BIGphillip79]

you probably will not hav eenough difference in overall height of the tire wheel combo to make a differnce in speedo. your going with a taller wheel but lower pro tire so it should be about the same. Just stand the tire/wheel combos next to each other. If there the same or really close your speedo will be close enough as well.

Calibrating the speedo is kind of a pain our trucks cus the kit to it is discontinued, though it can be doen with some soldering and few threads about it. The dealer should be able to do it for some big change.

But I wouldn't bother. You won't notice a difference.

[90.GMC.ST]

Okay, sounds good to me. Now that I think of it as well, it would be useless to alter the speedo mainly due to the factor that in the winter, I'll be using different tires and all because here they basically have to be studded if your wanting to stop at all. Thank you for everything though, you've been extremely helpful!

Thanks,
Jordan

[TennesseeZ]

I went from stock 16s to stock 18" Escalade wheels and tires with absolutely no problems or changes.