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8/11/10 2:18pm - Original Message: 'Correct wheel/tire combo'
74-454 Lifetime Member
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, - Canada

Coupe 74 - 454 Drive it like you stole it!

Joined: 8/6/2004
Posts: 533
It's been asked countless number of times.  The past week I have read 100's of forum posts and scoured wheels & tires sites for 10's or hours.  I have made up my mind; final and definitive... about 7 times!  Every time I think I got it; I read something else and have to start over.

I think I have it down path; but I'm left with one question; just to be sure!

Before the question; here is the necessary background info:

My current setup:
  1. Stock suspension (old and tired leaf rear spring)
  2. Replica rally wheels 15x8
  3. Previous owner had spacers for the rear wheels.  When I replaced the rotors and did not put spacers back; the parking brake cable is now rubbing big time on tire and there is a little paint transfer from the caliper to the wheels.  This leads me to think that the backspacing of those replicated wheels is 4.5" but I have not measured it yet.
  4. GTII 235/60R15 front
  5. GTII 255/60R15 rear
  6. Before removing the spacers; there was no rubbing and everything was fine.
  7. Planning to replace leaf rear spring for fiberglass one (nothing else; just the spring) at the same time as the wheels.

74 Corvette Stock setup (as far as my research goes...):
  1. Tire size: 225/GR70 x 15 (in today's measurement : 255/60R15)
  2. Wheel size: 8x15
  3. Bolt pattern: 5 bolts, 4.75
  4. Offset Range: -13 to 10
  5. Wheel Size Range: 15×6.5 to 20×8.5
  6. Backspacing : 4"

What I want:
  1. Torq Thrust 2.1 Polished 15x8 direct fit
  2. Firestone Firehawk Indy 500 of 235/60R15 front & 255/60R15 rear

Here's my questions
  1. I found the said Torq Thrust wheels in 15x8.  They have a 3.79" backspacing and -18mm offset.  Does that sound about right for what I'm looking for?  I want direct fit!
  2. Any recommendation for the fiberglass spring; concerning rating and bolt length; given it's a big block and will have 255/60R15 as rear tires?


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8/12/10 12:11pm - Reply: 'Correct wheel/tire combo'
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Mounds View, MN - USA

70 LT1 coupe, 69 350 HP coupe, 69 390HP 427 coupe, 71 LS5 convert, 85 coupe, 93 coupe

Joined: 5/24/2007
Posts: 1031
Correct backspacing for Corvette Ralleys is 4".  The wheels you mention would move tire out about 1/4", which will certainly clear inside, and with your tire size, will probably be fine on the outside.  My '71 has 255/60s on the rear, and they have plenty of clearance as long as you don't try to lower the car way below factory height.

Corvette Specialties is your best source for Corvette parts, accessories and gifts. www.CorvetteSpecialties.com


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8/12/10 5:08pm - Reply: 'Correct wheel/tire combo'
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Frederick, MD - USA

1969 convertible L71 427/435 4-speed black interior

Joined: 9/8/2003
Posts: 3398
I don't know about the Torq Thrusts, but many aftermarket wheels need the spacers to clear the calipers, so keep that in mind.  

You're incorrect on one thing...the GR70-15 does not correspond to P255/60R15.  It corresponds to P225/70R15.  That would be the correct size for a '74.  Chevrolet didn't authorize 60 series tires as optional until the '78 model year.  You may have clearance problems, though many don't and many do.  It seems to be a car by car thing.  If your coil springs have compressed at all it can be a problem.

Poet...Mystic...Soldier of Fortune. As always...self-absorbed, adversarial, c o c k y and in general a malcontent.

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