Tire size for rear of 69 gs?

Discussion in 'The Hides' started by dan zepnick, Sep 8, 2021.

  1. dan zepnick

    dan zepnick Well-Known Member

    What can you fit under the rear? Has 215/70/15's on it now.
     
    Jeremy zepnick guy likes this.
  2. Premier 350

    Premier 350 Chris (aka Webby)

    225/70/15s on Buick Rallys on mine. No issues.
     
    dan zepnick likes this.
  3. Mike B in SC

    Mike B in SC Well-Known Member

    245/60-15's fit nice on my 68.
     
  4. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    It depends on the back spacing and width of rim you use. 15" wheels never came on a 1969 A body as near as I can tell. On a 7" wide wheel, I say you need 5" of back space minimum to fit the widest tire possible.

    I base my conclusion on the Rallye wheel chart in this Forum. The 1968-70 14 X 6" wheel has 4 3/8" of back space. A 7" wide wheel would need 1/2" more back spacing to center the wheel/tire as stock. That's 4 7/8".
     
    Last edited: Sep 8, 2021
    dan zepnick likes this.
  5. mbusher83

    mbusher83 Well-Known Member

    I have 15x7 with 4” backspacing and bf Goodrich L60’s on the back of my 69 skylark. No issues, I think it’s similar to a 275/60/15 but the L60’s are an inch shorter.
    upload_2021-9-8_9-30-33.jpeg
    upload_2021-9-8_9-32-1.jpeg
     
    Max Damage, Waterboy, Q8 GS and 2 others like this.
  6. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Mark, have you actually measured that back spacing? That contradicts everything I know about back spacing requirements for the pre 1970's cars. No stock 15 X 7" wheels had 4" of back spacing, so those wheels have to be reproductions. I don't understand how they can fit with L60-15 tires.
     
    Last edited: Sep 8, 2021
  7. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    The L60-15 has a section width of 10.50"(266.7mm) and a tire height of 27.86". A P275/60R-15 has a section width of 275mm (10.8"), and a tire height of 27.99". The measurements can vary a small amount depending on the rim width they are mounted on. So an L60-15 is actually a little smaller by the numbers. It may appear bigger because of the overall tire construction. The G60-15 has a bigger look than the P245/60R-15 even though they are very close in measurement.
     
    Last edited: Sep 8, 2021
  8. mbusher83

    mbusher83 Well-Known Member

    They are reproductions Larry. 15x7’s from Coker tire if I remember correctly. I’ll pull one off and measure it again this weekend.
     
    1968_GS400 and dan zepnick like this.
  9. Eric

    Eric Founders Club Member

    20180211_095821.jpg I have 4ea 1970 Buick 15×7 WG rims with BFG
    245/60-15's on my 69 convertible.
    No issues whatsoever!It's 4-3/8" backspacing.
    20210227_223221.jpg
     
    Last edited: Aug 10, 2023
    dan zepnick likes this.
  10. Jeff Pulera

    Jeff Pulera Well-Known Member

    I had 275/60 rears and that was a bit too much, tight quarter lip clearance. Went to 17x9 with 275/40 and have more clearance now due to proper backspace/offset
     
  11. 1968_GS400

    1968_GS400 Founders Club Member

    What do you have on front? 14x6s still?
     
  12. Gary Bohannon

    Gary Bohannon Well-Known Member

     
    1968_GS400 likes this.
  13. Gary Bohannon

    Gary Bohannon Well-Known Member

    68 & 69 unique body style is well suited to wide back tires and stock size on front. Makes them look really tough.
    That's the 1st thing I would do on any 2 door model stepchild.
     
    1968_GS400 and TrunkMonkey like this.
  14. TrunkMonkey

    TrunkMonkey Well-Known Member

    I have 245/70/15x7 4.5 back spacing on my 68. About 3/4" from lip.

    Edited to add my post is likely irrelevant since I put in a 10 BOLT 8.5 1971 Olds A-body rear end.
    (monzaz build)
    Thanks Larry.

    Apologies.
     
    Last edited: Aug 10, 2023
    1968_GS400 likes this.
  15. Waterboy

    Waterboy Mullet Mafia since 6/20

    I have 275 x 60 x 15 on one of my 68s and on my 69. Stock Buick mag wheel. 15 inch diameter and 7 inches wide. I don’t know the backspacing but I believe 68GS_400. I’ve never heard any scraping or felt any scraping or seen any scraping.
     
    1968_GS400 likes this.
  16. Jeremy Zepnick

    Jeremy Zepnick STEELMAN

    I got Hoosier DR2's for the track. I cut some lip out, but still have some slight rubbing on sharp turns.
     
    Last edited: Aug 10, 2023
    1968_GS400 likes this.
  17. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Everything I have ever read about tires on the 68-69 says the wheels need more back spacing than the 70-72. Some of you may be getting away with it, but it is far from optimal. To fit the biggest tires, you need to center the wheel in the wheel well. 4 1/2" on an 8" wide wheel is NOT enough.

    Have a look at the 65-69 14" wheels. They were 6" wide. They used 4 3/8- 4 1/2" of back spacing. A 7" wide wheel would need another 1/2" of back spacing to keep the wheel centered. That's 4 7/8- 5" of back spacing. An 8" wide wheel needs a full 1" more back spacing. That is 5 3/8- 5 1/2" of back spacing.

    https://www.v8buick.com/index.php?attachments/wheelchart-jpg.158600/
     
    Last edited: Aug 10, 2023
    1968_GS400 likes this.
  18. Jim Weise

    Jim Weise EFI/DIS 482

    Might depend on what rear end is in Mark's 69.. the 65-7 A body rear ends were 1" narrower overall. Pretty sure that includes the 10 bolts, for sure on the 12 bolts, because I owned and used one for many years on the 70 GS race car. Mine was from a 67 Chevelle SS396 that was wrecked in the mid 80's. I Specifically found and installed that rear end so we could maximize our tire size with the Centerlines we had at the time.

    Complete, very good condition 12 bolt Chev with 4.11 posi from the factory.. paid $400 for it.. found it thru a classified ad in the Sunday MPLS Star/Tribune.

    Those were the days..

    JW
     
    1968_GS400 likes this.
  19. Starc Traxler

    Starc Traxler Well-Known Member

    P255/70/15 on stock 15x7 work very nice
     
    1968_GS400 likes this.
  20. Jeremy Zepnick

    Jeremy Zepnick STEELMAN

    I've got 275's on. 10" tread width 12.7 section width. I only cut the fender to the trim. So 1/4". But they fit
     
    Waterboy likes this.

Share This Page