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8/11/10 1:18pm - Original Message: 'Correct wheel/tire combo'
74-454 Lifetime Member
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, - Canada

Vette(s):
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?

Thanks!

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

Vette(s):
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.

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8/12/10 4:08pm - Reply: 'Correct wheel/tire combo'
Gunslinger
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Frederick, MD - USA

Vette(s):
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.


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