Rear track width / wheel backspace
Thread Starter
Racer
Joined: Sep 2008
Posts: 454
Likes: 7
From: SB County CA
Rear track width / wheel backspace
All,
I'm typically active on the C3 site. My issue: I've got a '68 roadster on a SRIII frame equipped with '87 suspension. I'm in the process of measuring for wheels. My track width is slightly wider than stock '68s but not sure how much (I haven't actually measured it yet).
Can someone confirm that '87 corvette specs define track width at mating surface to mating surface (in '68 it was wheel centerline to centerline)? Also what is your spec'd track width front/rear for a 84-87? Also, if anyone knows the spec'd width at the outboard fender edges, that would be great
I do have a jig/fixture, to measure things, but since its never been aligned, I'm trying my best eyeball/level method to set ride height and camber. Any help is greatly appreciated! By the way, I'm planning on 18x9.5 rear, 17x8.0 front on 275/40s and 245/45s. 285s are a possibility but only if they will fit well...
r,
Rob
I'm typically active on the C3 site. My issue: I've got a '68 roadster on a SRIII frame equipped with '87 suspension. I'm in the process of measuring for wheels. My track width is slightly wider than stock '68s but not sure how much (I haven't actually measured it yet).
Can someone confirm that '87 corvette specs define track width at mating surface to mating surface (in '68 it was wheel centerline to centerline)? Also what is your spec'd track width front/rear for a 84-87? Also, if anyone knows the spec'd width at the outboard fender edges, that would be great
I do have a jig/fixture, to measure things, but since its never been aligned, I'm trying my best eyeball/level method to set ride height and camber. Any help is greatly appreciated! By the way, I'm planning on 18x9.5 rear, 17x8.0 front on 275/40s and 245/45s. 285s are a possibility but only if they will fit well...
r,
Rob
3rd Gear
Joined: Nov 2011
Posts: 3
Likes: 0
I find it easier to think in terms of offset rather than backspace. I have zero offset wheels on the front of my Lark and it's still less twitchy than my (stock) 944. The 944 has a MONSTER scrub radius, from the factory,and you can feel it.
Last edited by JohnMartyn; Nov 15, 2011 at 06:44 PM.
Thread Starter
Racer
Joined: Sep 2008
Posts: 454
Likes: 7
From: SB County CA
Thanks,
They actually do offer a lot of help, but its just that when you get into fracrtions of an inch on some of these things car to car differences can be enough to cause issues.
I'm actually done with the measurements. It will be Front 17x8 w/5.50" on a 245/45 and Rear 18x9.5 w/6.75 BS on 275/40. The fronts will clear every radius and inset approx 7/8" from outboard fender lip. The rear will have approx 1/2" clearance inboard/outboard.
They actually do offer a lot of help, but its just that when you get into fracrtions of an inch on some of these things car to car differences can be enough to cause issues.
I'm actually done with the measurements. It will be Front 17x8 w/5.50" on a 245/45 and Rear 18x9.5 w/6.75 BS on 275/40. The fronts will clear every radius and inset approx 7/8" from outboard fender lip. The rear will have approx 1/2" clearance inboard/outboard.
Team Owner
Joined: Sep 2003
Posts: 25,383
Likes: 2,736
Thanks,
They actually do offer a lot of help, but its just that when you get into fracrtions of an inch on some of these things car to car differences can be enough to cause issues.
I'm actually done with the measurements. It will be Front 17x8 w/5.50" on a 245/45 and Rear 18x9.5 w/6.75 BS on 275/40. The fronts will clear every radius and inset approx 7/8" from outboard fender lip. The rear will have approx 1/2" clearance inboard/outboard.
They actually do offer a lot of help, but its just that when you get into fracrtions of an inch on some of these things car to car differences can be enough to cause issues.
I'm actually done with the measurements. It will be Front 17x8 w/5.50" on a 245/45 and Rear 18x9.5 w/6.75 BS on 275/40. The fronts will clear every radius and inset approx 7/8" from outboard fender lip. The rear will have approx 1/2" clearance inboard/outboard.
front- 8+1 (9.0) / (2.0) = 4.5 -5.5 = 1.0 X 25.4 (25)
rear - 9.5+1 (10.5) / (2.0) = 5.25 - 6.75 = 1.5 X 25.4 (38)
To check the rear fit you could use some 9.5 wide from an early C4 87MY or earlier 255/60's and your planned tire is maybe 5/8" taller and 3/4" wider at the section width. The 255 was used on both 8.5 and 9.5 wheels. You'll need to check the casting information.
Actually it might be interesting to try an 87MY or earlier 8.5 wheel on the front. It's 32mm and the diameter and section width is very close!!
These would at least "confirm" or prove your calculations "bogus"! It beats buying the wrong "stuff"!!!!!
How heavily modified and what purpose is the build? It's difficult for me to visualize a C3 with anything other than a tire/wheel that are 4 upped
Last edited by WVZR-1; Nov 17, 2011 at 03:41 AM.
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Joined: Jun 2012
Posts: 25
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From: Houston
Team Owner
Joined: Sep 2003
Posts: 25,383
Likes: 2,736
I've a friend that does C1's on SRiii for a fellow and it's certainly a quality product "without doubt"! He's done a couple others and I've seen several.
If I didn't have a chassis yet even knowing the quality of the SRiii and I lived in Houston I'd look into maybe Billy's chassis from Corvette Correction for a C1. Your concerns are bumper fit and finish as well as drive line availability. I don't recall ever reading any bad.
Tire/wheel combinations need to be done as an assembly. I'd have conversations with the chassis builder OR I'd go to the trouble of finding a finished product I liked wheel and tire wise and maybe duplicate that chassis build.
The 17X8 choice seems appropriate. I'll check maybe what's been used on the most recent build or two that he's done. They're generally picked up with body assembled, painted on the chassis and completed by the owner.
If I didn't have a chassis yet even knowing the quality of the SRiii and I lived in Houston I'd look into maybe Billy's chassis from Corvette Correction for a C1. Your concerns are bumper fit and finish as well as drive line availability. I don't recall ever reading any bad.
Tire/wheel combinations need to be done as an assembly. I'd have conversations with the chassis builder OR I'd go to the trouble of finding a finished product I liked wheel and tire wise and maybe duplicate that chassis build.
The 17X8 choice seems appropriate. I'll check maybe what's been used on the most recent build or two that he's done. They're generally picked up with body assembled, painted on the chassis and completed by the owner.
Last edited by WVZR-1; Oct 15, 2012 at 12:41 PM.
