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    1. #1
      Join Date
      Sep 2012
      Posts
      31
      Country Flag: Ireland

      Max wheel size/width on 73 Trans Am

      Hi Guys,

      Apologies 1st - this question has been probably asked a million times already!



      I have a '73 TransAm 455 (sadly a 400 lump now) which I'm restoring at the moment and I'm planning on going the pro-touring route.I like the staggered/deep dish look of the TransAm in the picture below and would like to know what are the maximum wheel widths/offsets that I can go with on a stock car to get a similiar look? Ideally, I'd like to go 18" all around.

      I'm assuming the mini-tub route allows for even wider wheels at the rear, but does that mean a rear axle change? thanks!


    2. #2
      Join Date
      Jun 2007
      Location
      Easley, SC
      Posts
      249
      Country Flag: United States
      Hi, welcome aboard ! Yes, that question has been asked a few times ! No sweat, just remember the search function will help you find tons of info on this awesome site. To answer your question, I have a '70 Formula 400 with 18's. I'm running an 18 x 8.5 (4.875 bs) on the front with a 255/48/18 . The rear is a 18 x 10 (5.875 bs) w/ 285/40/18.

      The front and rear lips have both been rolled, and I also had to flatten the seat belt hump in the rear fenderwell (big hammer). I did end up adding a 1/8" spacer on the rears to give me a touch more clearance from the leafs too. My car is lowered 3", so if your ride height is not as low, you may not have the fender lip issues I did.

      If you have any more questions, feel free to PM me. Good luck w/ your car !
      David

      Current rides:
      1970 Firebird FORMULA 400
      1964 Pontiac Tempest
      1986 Mustang LX 5.0 coupe

    3. #3
      Join Date
      Jan 2010
      Posts
      81
      could you post apicture of your car to give an idea of the look

    4. #4
      Join Date
      Jan 2012
      Location
      Virginia
      Posts
      237
      Country Flag: United States
      5.75 inch BS up front for a 275 18"... Rear would be 295 (not sure on back spacing). If you went with DSE mini tubs you could get rears like the car above, 335s w/ a 5.5" backspace but that is narrowing the rear 9". If you don't narrow the rear, adjust the BS accordingly. Hope this helps.

    5. #5
      Join Date
      Jan 2012
      Location
      Virginia
      Posts
      237
      Country Flag: United States
      My front is a 9.5" width 18, sorry forgot to add that. No pics of the front yet, but here is the rear:

      Note that the 335 would require moving the leafs inboard or going with a link setup.


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    6. #6
      Join Date
      Mar 2007
      Location
      Florida
      Posts
      2,376
      Country Flag: United States
      I ran front 17 X 9.5 - 5.5 backspacing with a 275 40 tire and 17 X 11 - 5.75 backspacing with 315 35 tires.

      My car is modified with aftermarket suspension. I did not roll the lips and early 2nd gens have no seatbelt bulge and wider rear wheelwells. The fronts will hit the fat sway bar at full lock so I just don't turn that far. The rears will just barely rub on both the inside and outside now at very high cornering loads on track since I added the weight of the cage. Before the cage they did not rub and they do not rub on the street. Anyone considering the wheel tire combination should carefully consider the use of the car, suspension, and payloads before jumping into such wide tires just for looks. While I do drive the car on the street, most of my use the past several years is on track. I stopped taking the car on vacation trips loaded with stuff and on street, there's no rear passengers, spare tire, or any other payloads. And before ordering any wheels Measure Measure Measure!!

      My new Rushforths are 18 X 10's all around with 285 and 295 30 tires. Haven't mounted them and tested yet so I won't comment on the backspacing.

      Here's the 275 /315 setup


    7. #7
      Join Date
      Jun 2007
      Location
      Easley, SC
      Posts
      249
      Country Flag: United States
      Quote Originally Posted by gold79ta View Post
      could you post apicture of your car to give an idea of the look
      Here ya' go. Man, there's no way I could cram a 295 in there. I'm not sure how you guys are doing that !

      [/IMG]


      [/IMG]
      David

      Current rides:
      1970 Firebird FORMULA 400
      1964 Pontiac Tempest
      1986 Mustang LX 5.0 coupe

    8. #8
      Join Date
      Jan 2012
      Location
      Virginia
      Posts
      237
      Country Flag: United States
      Best thing to do would be to measure your car, since the as-built tolerances may be eaten up more on one side vs the other. What fits nicely on one, may rub on the other. As a thought, I used to run 295/50s on a 15x8 snowflake in the rear and had to smash a flat spot on the tail pipe, just cause the install from either side wasn't symmetric.

      FYI, 295 would require a BFH (big fuggin hammer) on the seat-belt humps... so if you wanna run rear seat belts, you may need to come through that too.

    9. #9
      Join Date
      Jan 2010
      Location
      Burleson, TX
      Posts
      40
      Country Flag: United States
      Like Chadman said, every car is different even when it is rebuilt. My car (the one in your original post) the right side started rubbing once the suspension settled. I could have cranked the adjustable QA1's up a little but I liked the stance. Also the front and rears didn't match the body lines so I decided to change the fronts to 9". I'm still running a 275 up front. BFG recommends 9"-11" and I don't feel that it makes the tire bulge. Do your homework, take advice and measure twice.

      Good luck on your build.
      1973 Trans Am. 535 Butler IA2 Block, 700hp, 5-Speed TKO 600, Tri-Y Headers, DSE 4-link rear, DSE Mini-Tub, Pro Touring F-Body front suspension, Rushforth Night Train 18x9 and 18x12, BFG 275/35R18 and 335/30R18, Cerullo Seats

    10. #10
      Join Date
      Sep 2012
      Posts
      31
      Country Flag: Ireland
      Quote Originally Posted by damannhw View Post
      Hi, welcome aboard ! Yes, that question has been asked a few times ! No sweat, just remember the search function will help you find tons of info on this awesome site. To answer your question, I have a '70 Formula 400 with 18's. I'm running an 18 x 8.5 (4.875 bs) on the front with a 255/48/18 . The rear is a 18 x 10 (5.875 bs) w/ 285/40/18.


      The front and rear lips have both been rolled, and I also had to flatten the seat belt hump in the rear fenderwell (big hammer). I did end up adding a 1/8" spacer on the rears to give me a touch more clearance from the leafs too. My car is lowered 3", so if your ride height is not as low, you may not have the fender lip issues I did.


      If you have any more questions, feel free to PM me. Good luck w/ your car !
      Hi Damannhw! Yes - fantastic site - love looking at all project car updates and the great work to upgrade them - they have given me fair a few ideas for this build!

      Did the wheels and tires rub against the rear leaf springs before the spacer? Out of interest, why did you go with a 40 profile tire on the rear and not a 45? Was it because of clearance?

      I love the look of your setup - that's exactly what I'm after. What wheels are they and do you have a close-up pic of them?

      Here's a pic of the Trans Am in her current state. She's sitting on 275/15/60 tires at the moment with 255/15/60's up front. I eventually plan to do a brake disc conversion/upgrade at some point this year also.

      Rowan.

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    11. #11
      Join Date
      Sep 2012
      Posts
      31
      Country Flag: Ireland
      Quote Originally Posted by Chadman27 View Post
      5.75 inch BS up front for a 275 18"... Rear would be 295 (not sure on back spacing). If you went with DSE mini tubs you could get rears like the car above, 335s w/ a 5.5" backspace but that is narrowing the rear 9". If you don't narrow the rear, adjust the BS accordingly. Hope this helps.
      Hi Chadman! Nice car! what size wheels are those you have on the rear? I want to avoid going the mini-tub route - I want to try and get the widest wheel possible at the rear but without any serious modifications.

    12. #12
      Join Date
      Sep 2012
      Posts
      31
      Country Flag: Ireland
      Quote Originally Posted by NOT A TA View Post
      I ran front 17 X 9.5 - 5.5 backspacing with a 275 40 tire and 17 X 11 - 5.75 backspacing with 315 35 tires.

      My car is modified with aftermarket suspension. I did not roll the lips and early 2nd gens have no seatbelt bulge and wider rear wheelwells. The fronts will hit the fat sway bar at full lock so I just don't turn that far. The rears will just barely rub on both the inside and outside now at very high cornering loads on track since I added the weight of the cage. Before the cage they did not rub and they do not rub on the street. Anyone considering the wheel tire combination should carefully consider the use of the car, suspension, and payloads before jumping into such wide tires just for looks. While I do drive the car on the street, most of my use the past several years is on track. I stopped taking the car on vacation trips loaded with stuff and on street, there's no rear passengers, spare tire, or any other payloads. And before ordering any wheels Measure Measure Measure!!
      Hi John!, nice looking car - love the colour! Am I reading that right - a 11" wide wheel on the rear? Do you have a better picture of the rear wheels in that setup above? Trying to get an idea as to how much of a lip is on the wheel. Good point on the wheel rub up front - forgot about that.... planning on a 255 up front anyway so I should be good. Biggest job now is to decide on a set of wheels I like!

    13. #13
      Join Date
      Aug 2011
      Location
      North Platte,NE
      Posts
      876
      Country Flag: United States
      Go big or go home lol! Ive been considering 285s on the front of my Dart, still need to let the 275s finish clearancing themselves first haha....

    14. #14
      Join Date
      Jan 2012
      Location
      Virginia
      Posts
      237
      Country Flag: United States
      Quote Originally Posted by v8 stingray View Post
      Hi Chadman! Nice car! what size wheels are those you have on the rear? I want to avoid going the mini-tub route - I want to try and get the widest wheel possible at the rear but without any serious modifications.
      18x12 w/ 5.5 BS (rear is narrowed), 335 Tire. You would need to mini-tub to fit this size. Let me know if you have any other questions, I'd be happy to help!

    15. #15
      Join Date
      Sep 2012
      Posts
      31
      Country Flag: Ireland
      Quote Originally Posted by Chadman27 View Post
      18x12 w/ 5.5 BS (rear is narrowed), 335 Tire. You would need to mini-tub to fit this size. Let me know if you have any other questions, I'd be happy to help!
      so max I could really go for is 285 in the rear? What kind of backspacing would I need on this in order to get that deep dish look?

    16. #16
      Join Date
      Nov 2013
      Location
      near Charlotte, NC
      Posts
      152
      Country Flag: United States
      What did you end up doing?
      Conrad
      Original owner '84 Grand National. CAS V1 (big) front-mount intercooler, Comp roller hyd cam, Champion Al intake/heads, T66 turbo, 3.5" custom cat-back exhaust, RideTech TruTurn front & DSE rear swaybars/ctrl arms, Ridetech 3-way coilovers, Baer 6P 14/13. FAST w/TouchScreen & GM Flex Fuel sensor, 120 lb injectors, Ricks SS tank, Aeromotive Eliminator pump.

    17. #17
      Join Date
      Aug 2006
      Location
      austin
      Posts
      357
      275 is safe for the rear. 285 may require a BFH. 295 may be too big for even a BFH (all cars a little dif). Just bite the bullet and minitub it!

      Greg
      1976 Trans Am SacrilEdge
      twin turbo 455
      Ttops and 4spd
      one of 110 made
      https://www.pro-touring.com/showthre...ect&highlight=
      https://www.pro-touring.com/showthre...ilEdge-is-free!

    18. #18
      Join Date
      Sep 2012
      Posts
      31
      Country Flag: Ireland
      Quote Originally Posted by alphaenvirmgt View Post
      What did you end up doing?
      Conrad
      haha... nothing to-date! My '66 Wildcat Convertible has been keeping me busy!

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      The Trans Am is actually going to the body shop this weekend, so I'm looking to action the wheels/suspension now.

      I am probably looking to for for something similiar to Damannhw in that I am looking at running an 18 x 8.5 (4.875 bs) on the front with a 255/40/18 and an 18 x 10 (5.875 bs) w/ 285/40/18 on the rear.

      Damannhw > you mentioned you had to put in a 1/8" spacer on the rear wheels to clear the leaf springs - I want to try avoid using spacers, so should I compensate by adjusting the backspacing on the rear wheels to something else other than 5.875?

    19. #19
      Join Date
      Jun 2010
      Posts
      56

      Max wheel size/width on 73 Trans Am

      I run a 315's on an 17x11" in the rear of a 73' Camaro. Slight rub on high load turns. Just enough to smear the tire shine into the inner quarter. My fronts are a 255 on a 17x8.5 and have more than enough room. Shoulda went 9".

      http://www.nastyz28.com/forum/showthread.php?t=243415

    20. #20
      Join Date
      Jun 2010
      Posts
      56

      Max wheel size/width on 73 Trans Am

      Also. I had to add a 1/8" spacer on one side in the rear. Some of the 2nd gen rears are not exactly centered.

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