Maybe I am not looking hard enough

[10Aniv]

Curious on the biggest tire I can stuff into a 79 Trans AM without tubbing it. Going to have the year one wheels custom made for it and I know I will need to measure but just getting a rough idea and starting point.

[damannhw]

Curious on the biggest tire I can stuff into a 79 Trans AM without tubbing it. Going to have the year one wheels custom made for it and I know I will need to measure but just getting a rough idea and starting point.

I've got a '70 Formula with a 285/40/18 on the rear. I did have to flatten the seat belt hump, roll the quarter lips, and massage a few areas, but nothing major to make it fit. The later Birds, from what I've read, may have slightly less clearance than mine though. I would say a 275 w/ no problems, and the 285 if you don't mind tweaking it a little. BTW, My rear wheel is an 18X10 w/ 6.0" backspace. I would recommend 5-7/8 backspace though.

[10Aniv]

I've got a '70 Formula with a 285/40/18 on the rear. I did have to flatten the seat belt hump, roll the quarter lips, and massage a few areas, but nothing major to make it fit. The later Birds, from what I've read, may have slightly less clearance than mine though. I would say a 275 w/ no problems, and a 285 if you don't mind tweaking it a little. BTW, My rear wheel is an 18X10 w/ 6.0" backspace. I would recommend 5-7/8 backspace though.

Do you have any pics of your tires/wheels?

[damannhw]

Do you have any pics of your tires/wheels?

Here's a couple..




I need to get a few shots from directly behind the car. I'll try to do that for you.

[10Aniv]

Very nice! I am thinking mine will sit a little higher, maybe an inch off the fender wells if that makes sense. I never realized how flat the rear windows were on the early 2nd gens.

I was also thinking a 284/40/15 with a turbos might be kinda cool too but I am guessing it would sit alot lower?

[damannhw]

My car acutally sits just slightly higher now since I changed springs. Pics coming shortly.

[10Aniv]

Just noticed the 285/40/15 is no longer made. Plus the back spacing on my turbos will probably not allow a much bigger tire

[damannhw]

Just noticed the 285/40/15 is no longer made. Plus the back spacing on my turbos will probably not allow a much bigger tire

I drove my car to work today, so here are a couple more. The springs are Detroit Speed 3" drop, but I think it still needs to go down just a little more.

[10Aniv]

Thats about the exact stance I want

[Skip Fix]

I used to use a 305-40-16 drag tire on my 78 TA on "front" IROC Z wheels. They are pretty close to a zero offset. The car also fit a 255-50-16 on "rear" GTA wheels that have a fair amount of inboard offset 5" backspace.

Years ago several local TA guys ran the 295-50-15s on 8" snowflakes.

Most of these like he said you have to hammer the rear seat belt hump.

[10Aniv]

Thanks guys. I hope it will be off to the body shop in late winter early spring for the floor pans and body work. I will have them "massage" the seatbelt hump so it looks good and roll the lips on the wheel wells.

I wish someone made an aftermarket turbo wheel that had more offset.

[10Aniv]

I used to use a 305-40-16 drag tire on my 78 TA on "front" IROC Z wheels. They are pretty close to a zero offset. The car also fit a 255-50-16 on "rear" GTA wheels that have a fair amount of inboard offset 5" backspace.

Years ago several local TA guys ran the 295-50-15s on 8" snowflakes.

Most of these like he said you have to hammer the rear seat belt hump.

How do you like the 455?

[opnwide]

Which year one wheels were you referring to? The 17" cast or the 18" billet? The 17" wheels fit well with 275s up front and 295s in back at stock to 1" lowering. If you lower the car 3" or more then you may need to go 255s up front and 275s in back to avoid rub at full bump.
At 2" I guess it depends on your car and suspension settings.

[10Aniv]

I am looking at the billet ones. I have to figure out how low I am going. I would like to see the whole tires, I hate when the tire is tucked way up inside, I want to be able to drive the darn thing in the real world. I am thinking about .5 to 1.0 inches above the top of the tire.

[opnwide]

Sounds like a 3" drop to me.