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:
Stock suspension (old and tired leaf rear spring)
Replica rally wheels 15x8
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.
GTII 235/60R15 front
GTII 255/60R15 rear
Before removing the spacers; there was no rubbing and everything was fine.
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...):
Tire size: 225/GR70 x 15 (in today's measurement : 255/60R15)
Wheel size: 8x15
Bolt pattern: 5 bolts, 4.75
Offset Range: -13 to 10
Wheel Size Range: 15×6.5 to 20×8.5
Backspacing : 4"
What I want:
Torq Thrust 2.1 Polished 15x8 direct fit
Firestone Firehawk Indy 500 of 235/60R15 front & 255/60R15 rear
Here's my questions
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!
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?
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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Corvette Specialties is your best source for Corvette parts, accessories and gifts. www.CorvetteSpecialties.com
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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Poet...Mystic...Soldier of Fortune. As always...self-absorbed, adversarial, c o c k y and in general a malcontent.
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