Hitman's Pontiac Trans Am Forum

Trans Am Information => Trans Am Tech => Suspension => Topic started by: Tabazan on June 01, 2013, 10:06:18 AM

Title: Big fat at the rear
Post by: Tabazan on June 01, 2013, 10:06:18 AM: Hi to all,

I plan to change my snowflakes for American Racing Outlaw II 15" / offset 19 on front an rear.

I've got standard P225/70R15 with Bridgestone Serie 300 at this time, but want to go BFG Radial T/A (same size front but and a "big fat one" at the rear, like 255/70R15 or 275/60R15 for example)

1. What is the maximum size possible (for rear) without wheel well, suspension modification or tach settings ?
2. As it's mainly for style (I want to "spare" the original gear, nice too, for exhibitions purpose), how does it change the TA reactions and behaviour (now I use it for everyday driving, and even with big rain or snow that's fine :-) ?
3. Your advice for a more logic setup mixing look and good ride.

Thanks for advice guys

Gilles
Title: Re: Big fat at the rear
Post by: hada76 on June 01, 2013, 04:04:07 PM: you didn't mention the width of your new wheels, as with any set up the backspace is key to good fitment
Title: Re: Big fat at the rear
Post by: Tabazan on June 01, 2013, 06:25:49 PM: Oh, yeah, sorry ... :-\

There are two sizes 7" (-6 offset) or 8" (-19 offset). Honestly I don't know which to choose or which one would fit best.

The idea is the largest and fattest rear tire without it goes way out the fender (swiss cops don't like that) and without it rubs at any point of the well (on bumps).
Title: Re: Big fat at the rear
Post by: 72blackbird on June 01, 2013, 10:00:15 PM: A 255/60R15 is the same height as a 225/70R15 but much wider- it will fit on both 7" and 8" wide stock wheels. But as mentioned before, offset is critical to keep a wider tire from rubbing the shocks or suspension. A 275/60R15 will also fit at the rear, as well as a 295/50R15- these fit better on a 8" wheel- the 275 is clearly taller than the stock tire and will require a speedo gear swap to keep the reading accurate, the 295 is a bit shorter.

The -19mm offset translates to a 3 3/4" backspacing, which will push the wheel out too far and cause the tire to make contact with the wheel lip as the suspension travels. Stock 7" and 8" wheels have a 4 1/2" backspacing (zero offset), and you should be able to run up to a 28" tall tire with these wheels with no rubbing.

Geno
Title: Re: Big fat at the rear
Post by: hada76 on June 02, 2013, 01:11:08 AM: good info geno, and as said before on here, backspace and offset are 2 different things

http://www.youtube.com/watch?v=2K1lUlv9ZOA
Title: Re: Big fat at the rear
Post by: highway star on June 09, 2013, 02:20:14 AM: I'm satisfied with BFG Radial TA, 225/70-15 front and 275/60-15 rear. Ran the 295/50-15 on rear for a while, too short in diameter for my liking.