1970 Pontiac Trans Am Detroit Speed wheel size help needed

[alwayskaos]

Hello, new to this site, but I have not been able to find the information here yet, although it has probably been discussed many times. My vehicle is complete DSE with subframe, quadralink, mini tubs etc. I asked DSE the tire size and backspacing of their blue 1970 Camaro test car, and they said it had 18x12 with a 335 rear and 18x9 with 255 front with Front back spacing is 6.125" and rear of 5.5". I'm ok with this, but I would like to get a little wider in the front if I can. Since it was their test car, maybe they went with the largest that fit in the front without modification of the inner wheel wells? I don't mind having to either modify my inner wheel wells, or purchase the fiberglass/Carbon fiber versions for more clearance if needed. If you have a similar setup....please share. Its ready to come off of the rotisserie and get rolling

[Alponcho]

I have a 70 Formula with DSE subframe and run a 18x10 wheel with 6.25" backspace, 275 35 18 tire. I had to put a single spacer (travel limiter) in the rack on the RH side to prevent the RH control arm from rubbing the wheel...but otherwise no issues, and running unmodified OEM inner fenders. Should be OK with 6.125 backspace, which is what DSE recommended.

[alwayskaos]

Thanks Alponcho....that's more like the size I was looking for. Can you send a photo if possible? What rims did you use?

[Alponcho]

Forgeline GA3. Let me know if you want a photo of something specific. But this should give you an idea of what the wheel/tire set up looks like on a 2nd gen bird.

[badazz81z28]

I would caution on the rear tire…the back spacing is totally dependent on how much you have narrowed the rearend. In my case apparently, a DSE spec’d rear needed 5.75 BS to give 1/4 lip clearance, even with the lips rolled.

[Alponcho]

I would caution on the rear tire…the back spacing is totally dependent on how much you have narrowed the rearend. In my case apparently, a DSE spec’d rear needed 5.75 BS to give 1/4 lip clearance, even with the lips rolled.

Yep, totally agree. Also, Firebirds have rounded wheel openings and so the lip isn't as much of an issue as it is on a Camaro.

[Raszaron]

Beautiful car Alponcho! Not trying to take over the thread, but I too am looking to get the right wheel/tire combo and fitment on my 72/73 Firebird (Fool's GOLD the 'strike' formula) right now. Is your Firebird mini-tubbed and did you have to roll your fender lips?


I am temporarily using a previous cars wheels on my Firebird as shop wheels (Flow One F4s from my C5 Z06 - 18x9.5 +54 with a 1.5" spacer on the front and 285/35R18 tires, and 18x10.5 +50 with a 1.5" spacer and a 10mm lug-centric spacer with 315/35R18 tires on the rear. My car isn't mini-tubbed and have no intention of doing that as the above setup currently fits without issue, but I am looking to get a set of Forgelines and want to make sure I am spot on with the backspacing, and don't run into a problem with the fender lips cutting into the tire going over bumps.

https://www.pro-touring.com/threads/...ontiac-Formula

[Alponcho]

Beautiful car Alponcho! Not trying to take over the thread, but I too am looking to get the right wheel/tire combo and fitment on my 72/73 Firebird (Fool's GOLD the 'strike' formula) right now. Is your Firebird mini-tubbed and did you have to roll your fender lips?


I am temporarily using a previous cars wheels on my Firebird as shop wheels (Flow One F4s from my C5 Z06 - 18x9.5 +54 with a 1.5" spacer on the front and 285/35R18 tires, and 18x10.5 +50 with a 1.5" spacer and a 10mm lug-centric spacer with 315/35R18 tires on the rear. My car isn't mini-tubbed and have no intention of doing that as the above setup currently fits without issue, but I am looking to get a set of Forgelines and want to make sure I am spot on with the backspacing, and don't run into a problem with the fender lips cutting into the tire going over bumps.

https://www.pro-touring.com/threads/...ontiac-Formula

Thank you! Yes, my orange bird is mini tubbed. Did not have to roll the fender lips. Rears are less of an issue on a Firebird since the wheel opening is round. I'm enjoying watching your progress on Fools Gold!

[Raszaron]

Thank you! Yes, my orange bird is mini tubbed. Did not have to roll the fender lips. Rears are less of an issue on a Firebird since the wheel opening is round. I'm enjoying watching your progress on Fools Gold!

Thank you for the quick reply and watching my progress! My biggest worry on my build is getting the wheels right the first time and hopefully only time. I have been slacking on putting updates on the forum, but have been putting videos on Facebook. Once I get some more time freed up, will try to update my build thread here.