Tubbing
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Joined: Apr 2008
Posts: 3,002
Likes: 64
From: Wittman,Az
Car: 86 IROC-Z, '71 RS
Engine: 305 TPI/ 350
Transmission: 700R4/TH350
Re: Tubbing
I am getting ready to mini-tub my 85 T/A and the best thing I've seen is this thread: https://www.thirdgen.org/forums/fabr...t-started.html
It is a truly awesome and informative thread.
I will be putting a 335/35/19 under there (I think.)
Good luck!
It is a truly awesome and informative thread.
I will be putting a 335/35/19 under there (I think.)
Good luck!
Joined: Jan 2004
Posts: 1,761
Likes: 4
From: The "D"
Car: A Portly 85 Z28
Engine: 4.530 X 4.250 BBC
Transmission: under rated for this application
Axle/Gears: also under rated
Re: Tubbing
Thank you, it worked out good for me, I went a bit over board on the cutting but it`s just a drag car. For a street car I would leave the outer portion of the stock wheel well, no need to cut it unless your stuffing a huge tire and lowering it to the weeds. I`m going to add that info and a good before and after shot.
Joined: Aug 2006
Posts: 12,807
Likes: 108
From: Central NJ
Car: 86 Trans Am
Engine: 408 stroker sbc
Transmission: TKO600
Axle/Gears: Moser full floater m9, 3:70 trutrac
Re: Tubbing
with a 315 a don't think you could get them to tuck inside the lip and you would have to cut some other metal from inside the wheel well which aint no big deal, But what would all have to be done if i wanted 315/35R18's in the back with it being lowered 2-1.5"
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Joined: Apr 2008
Posts: 3,002
Likes: 64
From: Wittman,Az
Car: 86 IROC-Z, '71 RS
Engine: 305 TPI/ 350
Transmission: 700R4/TH350
Re: Tubbing
You are welcome, greezemonkey! It's an awesome thread with a lot of info! I will be airbagging my T/A and stuffing a turbocharged 383 in there(800 HP, est), so I will need a lot of tire in order to have any kind of traction! I have seen a 315/35/17 on these cars with minimal work, but the wheel offset has to be PERFECT! LOL
Joined: Aug 2006
Posts: 12,807
Likes: 108
From: Central NJ
Car: 86 Trans Am
Engine: 408 stroker sbc
Transmission: TKO600
Axle/Gears: Moser full floater m9, 3:70 trutrac
Re: Tubbing
same work. Lowering the car will require an adjustable panhard bar, and adjustable lower control arms would be a good idea too.
What is your definition of "tuck"? to be completely inside of the fender lip or just not out past it?
Im running 335/30/18's on the rear and the outside of the tire sits about 1/2" in from the outside of the car, which is what i feel to be, a perfect spot. However, it required a full mini-tub and some other custom work. making a 315 tuck like that would require almost as much work. You will have to cut and reshape the front of the wheel well, and remove the bumpstop area completely and rebuild that area as well. You will also have to run an aftermarket tubular set of lower control arms to clear the tires if you want to bring them more inboard that just flush with the side of the car.
What you can do is this. Remove a rear wheel. Get a straight edge about 26" long and a tape measure. Now, for the 315 tire you would want a, 11" wheel, and i get it siting in a good spot you would want 7.5" of backspacing from the face of the rotor/drum.
Lay the straight edge across the rotor/drum and measure back 7.5", that will show you the extent of what needs to be removed and modified. Keep in mind, that is where the rim will be and does not take into consideration where the tire will be, and after that you still need some breathing room for axle movement.
When i did mine, i used a totally measurement of 9.625" from the face of the rotor to my cut line. Im using a wheel with 8.5" of back spacing, i added 1/4" for tire bulge, leaving me 3/4" of extra room for axle movement, and .125" for the sheetmetal that i used to rebuild the side of the frame that i cut off and to form the inside of the new wheel well. This much cutting required relocating the springs or using coil-overs and using offset rear control arms. I dont think you will have to do that with a 315.
I found that i needed 1/2" minimum clearance from the tire to the inside wheel well to keep the tire from rubbing when i throw the car around.
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yea its a pretty common size, but they never "tuck" under the car, they are always flush with the side of the fender, not quite right in my book.
What is your definition of "tuck"? to be completely inside of the fender lip or just not out past it?
Im running 335/30/18's on the rear and the outside of the tire sits about 1/2" in from the outside of the car, which is what i feel to be, a perfect spot. However, it required a full mini-tub and some other custom work. making a 315 tuck like that would require almost as much work. You will have to cut and reshape the front of the wheel well, and remove the bumpstop area completely and rebuild that area as well. You will also have to run an aftermarket tubular set of lower control arms to clear the tires if you want to bring them more inboard that just flush with the side of the car.
What you can do is this. Remove a rear wheel. Get a straight edge about 26" long and a tape measure. Now, for the 315 tire you would want a, 11" wheel, and i get it siting in a good spot you would want 7.5" of backspacing from the face of the rotor/drum.
Lay the straight edge across the rotor/drum and measure back 7.5", that will show you the extent of what needs to be removed and modified. Keep in mind, that is where the rim will be and does not take into consideration where the tire will be, and after that you still need some breathing room for axle movement.
When i did mine, i used a totally measurement of 9.625" from the face of the rotor to my cut line. Im using a wheel with 8.5" of back spacing, i added 1/4" for tire bulge, leaving me 3/4" of extra room for axle movement, and .125" for the sheetmetal that i used to rebuild the side of the frame that i cut off and to form the inside of the new wheel well. This much cutting required relocating the springs or using coil-overs and using offset rear control arms. I dont think you will have to do that with a 315.
I found that i needed 1/2" minimum clearance from the tire to the inside wheel well to keep the tire from rubbing when i throw the car around.
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yea its a pretty common size, but they never "tuck" under the car, they are always flush with the side of the fender, not quite right in my book.
Last edited by //<86TA>\\; Nov 28, 2008 at 07:21 PM. Reason: Automerged Doublepost
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Re: Tubbing
Thanks for the info; I am planning on putting an intire setup of spohn suspention; panhard, control arms, sway bars, coilovers, basically the intire suspension front and back and all adjustable and chromoly. With your tire sticking out that much do you get any rubbing also is your car lowered. If you have any pictures could you possible post some. Thanks
Joined: Aug 2006
Posts: 12,807
Likes: 108
From: Central NJ
Car: 86 Trans Am
Engine: 408 stroker sbc
Transmission: TKO600
Axle/Gears: Moser full floater m9, 3:70 trutrac
Re: Tubbing
i have no rubbing at all, anywhere. and the tire does not "stick out"
its lowered a bit.


both these pics are pretty much straight down the wheel, so you can see where it sits.
ride height
its lowered a bit.


both these pics are pretty much straight down the wheel, so you can see where it sits.
ride height
Last edited by //<86TA>\\; Nov 29, 2008 at 12:13 PM. Reason: wrong pic
Joined: Aug 2006
Posts: 12,807
Likes: 108
From: Central NJ
Car: 86 Trans Am
Engine: 408 stroker sbc
Transmission: TKO600
Axle/Gears: Moser full floater m9, 3:70 trutrac
Re: Tubbing
no problem, but like i said, get a tape measure and a straight edge, pull a wheel and see where you stand as far as clearance. It will give you a visual to work off of.
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iTrader: (3)
Joined: Apr 2008
Posts: 3,002
Likes: 64
From: Wittman,Az
Car: 86 IROC-Z, '71 RS
Engine: 305 TPI/ 350
Transmission: 700R4/TH350
Re: Tubbing
My definition of "tuck" has always been that the axle/suspension can travel all the way to the bumpstops and not have the wheel/tire come into contact with anything. I definately recommend an adjustable panhard rod for lowering purposes.
Joined: Aug 2006
Posts: 12,807
Likes: 108
From: Central NJ
Car: 86 Trans Am
Engine: 408 stroker sbc
Transmission: TKO600
Axle/Gears: Moser full floater m9, 3:70 trutrac
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