Early vs late C4 rear suspension width difference?
Thread Starter
Tech Contributor
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From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Early vs late C4 rear suspension width difference?
Did a search but didn't find what I was looking for. Trying to find the rear suspension width difference between the early and late designs (rotor hub to rotor hub).
Thanks for any help.
Thanks for any help.
Burning Brakes
Joined: Nov 2008
Posts: 1,159
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From: Orange Park Florida
width
There was a post on here recently about it. And I inquired about it also and it seemed that if I changed the rear spindles on my 1987 to the later 90's model spindles. Then I could run the deeper offset wheels without a concentric spacer. That is the little bit I know so far.
Team Owner
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Just spotted this from Flatout Engineering
Last edited by WVZR-1; Dec 16, 2017 at 09:19 PM.
Thread Starter
Tech Contributor
Joined: Jun 2004
Posts: 20,868
Likes: 961
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
There was a post on here recently about it. And I inquired about it also and it seemed that if I changed the rear spindles on my 1987 to the later 90's model spindles. Then I could run the deeper offset wheels without a concentric spacer. That is the little bit I know so far.
Team Owner
Joined: Sep 2003
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I understand. I'm contemplating going the other direction. I've got a '93 rear suspension under my '51 Chevy truck, but I'd like to tuck the wheels in a touch to give a little more fender clearance for the outer sidewalls. I need this width difference to also calculate how much room I'd be losing on the inner sidewall side too.
Safety Car
Joined: Aug 2013
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From: Minneapolis Mn
Kind of relates, remember later ones have a disc parking brake while early have drum.
Thread Starter
Tech Contributor
Joined: Jun 2004
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From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
If I'm understanding your info correctly, the wheel offset differences (18mm/.71") seem to be the measurement to focus on if Chevrolet kept the early and later 9.5" wheels in the same place in the fenderwell. (I would hope that Chevrolet wouldn't do something odd like change the wheels by 18mm and change the suspension knuckles by something other than 18mm also.)
Pulling the current (C3 aluminum) wheels in by 18mm/.71" on each side by swapping in the early knuckle assemblies should do the trick.
Again, thanks.
Edit: Just saw your edit in post #3. It says the suspensions are 1" (.5" per side) different. That should still work fine.
Last edited by 69427; Dec 16, 2017 at 09:46 PM. Reason: Added content.
Burning Brakes
Joined: Nov 2008
Posts: 1,159
Likes: 31
From: Orange Park Florida
????
it's all a bit confusing.. So am I safe to believe that if I change just my rear spindles on my 1987 C4 to the later model rear spindles say from a 1992 or newer. Then I could run the 11" wide rear rims witn my 275 wide tires without a concentric spacer. I am trying to get the rim and tire combination to set inside my C4 body and not stick out to far. Thanks, gary
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Burning Brakes
Joined: Nov 2008
Posts: 1,159
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From: Orange Park Florida
I think I may have spoke in error. The front has spindles and the rear is a modular wheel bearing. I changed the modular wheel bearings after the passenger side went bad. So my question is what parts did they change to make the later model narrower to use the wider offset rims on the back. Thanks for any info, Gary
Safety Car
Joined: Apr 2005
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From: Dale City VA
I have owned C4s with both suspensions under them and this is what I know.
Using this diagram as a reference.
http://repairs.willcoxcorvette.com/1...ar-suspension/
Number 48, the outer stub axle, is different. It's longer on the 88-96. It has to be longer because....
Number 40, the mounting block for the wheel bearing and also the brake caliper mount, is different. They are much wider on 88-96.
Number 23, the inner camber arm mount, is different. It places the inner pivot point for the camber arm higher and closer to the center on 84-87, creating more roll steer and camber gain as the suspension travels... The 88-96 places the camber arm pivot further out towards the side to reduce roll steer and chamber gain.
Those are the pieces that GM changed in 88 to make the rear suspension track width wider and reduce roll steer/camber gain.
Also number 63, the trailing arm bracket is different. On 88-96 they lowered the mounting holes to reduce "Anti Squat" A/S%.... on the 84-87 the holes are higher up and the suspension has more A/S%. But it does not effect the width only the geometry.
Will
Using this diagram as a reference.
http://repairs.willcoxcorvette.com/1...ar-suspension/
Number 48, the outer stub axle, is different. It's longer on the 88-96. It has to be longer because....
Number 40, the mounting block for the wheel bearing and also the brake caliper mount, is different. They are much wider on 88-96.
Number 23, the inner camber arm mount, is different. It places the inner pivot point for the camber arm higher and closer to the center on 84-87, creating more roll steer and camber gain as the suspension travels... The 88-96 places the camber arm pivot further out towards the side to reduce roll steer and chamber gain.
Those are the pieces that GM changed in 88 to make the rear suspension track width wider and reduce roll steer/camber gain.
Also number 63, the trailing arm bracket is different. On 88-96 they lowered the mounting holes to reduce "Anti Squat" A/S%.... on the 84-87 the holes are higher up and the suspension has more A/S%. But it does not effect the width only the geometry.
Will
Last edited by rklessdriver; Dec 18, 2017 at 11:55 AM.
Burning Brakes
Joined: Nov 2008
Posts: 1,159
Likes: 31
From: Orange Park Florida
Thanks
Thanks for the reply and info and the time you spent on this. I was hoping for a quick fix to get those 11" rims to fit in the wheel wells of my 1987. It sure seems like they would have changed a dimension on part #58 or #40 or in the bearing hub #41. It seems like such a small amount of offset that the difference is between the 87 and the 88. Maybe I will just have the tires mounted and take a swag at what it looks like. I do have the right concentric adapters for all four wheels and the new rims ( worse case senario.) I would have to remount the older chrome A mold wheels and live with it. Ehhhhh, Thanks again, gary
I haveowned C4s with both suspensions under them and this is what I know.
Using this diagram as a reference.
http://repairs.willcoxcorvette.com/1...ar-suspension/
Number 48, the outer stub axle, is different. It's longer on the 88-96. It has to be longer because....
Number 40, the mounting block for the wheel bearing and also the brake caliper mount, is different. They are much wider on 88-96.
Number 23, the inner camber arm mount, is different. It places the inner pivot point for the camber arm higher and closer to the center on 84-87, creating more roll steer and camber gain as the suspension travels... The 88-96 places the camber arm pivot further out towards the side to reduce roll steer and chamber gain.
Those are the pieces that GM changed in 88 to make the rear suspension track width wider and reduce roll steer/camber gain.
Also number 63, the trailing arm bracket is different. On 88-96 they lowered the mounting holes to reduce "Anti Squat" A/S%.... on the 84-87 the holes are higher up and the suspension has more A/S%. But it does not effect the width only the geometry.
Will
Using this diagram as a reference.
http://repairs.willcoxcorvette.com/1...ar-suspension/
Number 48, the outer stub axle, is different. It's longer on the 88-96. It has to be longer because....
Number 40, the mounting block for the wheel bearing and also the brake caliper mount, is different. They are much wider on 88-96.
Number 23, the inner camber arm mount, is different. It places the inner pivot point for the camber arm higher and closer to the center on 84-87, creating more roll steer and camber gain as the suspension travels... The 88-96 places the camber arm pivot further out towards the side to reduce roll steer and chamber gain.
Those are the pieces that GM changed in 88 to make the rear suspension track width wider and reduce roll steer/camber gain.
Also number 63, the trailing arm bracket is different. On 88-96 they lowered the mounting holes to reduce "Anti Squat" A/S%.... on the 84-87 the holes are higher up and the suspension has more A/S%. But it does not effect the width only the geometry.
Will
Last edited by gman35; Dec 18, 2017 at 09:55 PM. Reason: typing error