Rear bump stop clearance
Thread Starter
Le Mans Master
Joined: Jan 2006
Posts: 6,505
Likes: 139
From: Butler Pa
Rear bump stop clearance
I was looking under the car the other day and noticed that there's only about an inch of clearance between the top and bottom rear bump stops. Is this normal?
I have 225/70R15 BFG's which are 27.4" tall and the fender lip is about 3/4" above the tire. The half shafts do angle up slightly but not excessive. There have been several times that I've noticed the rear stops bottoming out.
I have 225/70R15 BFG's which are 27.4" tall and the fender lip is about 3/4" above the tire. The half shafts do angle up slightly but not excessive. There have been several times that I've noticed the rear stops bottoming out.
Melting Slicks
Joined: Nov 2001
Posts: 2,659
Likes: 7
From: Katy (Houston) TX
CI 7-8 Veteran
Those half shafts shouldn't be pointing upwards. Do you have a stock steel spring? Or aftermarket with long bolts? You shouldn't be bottoming out on those bump stops. Sounds like you need a new spring and probably new shocks.
Thread Starter
Le Mans Master
Joined: Jan 2006
Posts: 6,505
Likes: 139
From: Butler Pa
I have the stock steel spring with 8" bolts and I probably do need new shocks. The only way to change the distance between the bump stops is to raise the ride height. I'm not doing that.
I just wanted to know how much distance I should have between the bump stops.
I just wanted to know how much distance I should have between the bump stops.
Melting Slicks
Joined: Nov 2001
Posts: 2,659
Likes: 7
From: Katy (Houston) TX
CI 7-8 Veteran
There's no 'real' answer to that. If you were asking from an NCRS perspective you should have more. If you're asking from a looks perspective then it's up to you. If you're asking from a performance perspective then it depends on the setup. But no matter what, you shouldn't be hitting the bump stops except for under extreme conditions. If you like the height it is now, then you could possibly put in some stiffer shocks but that may still not help you. Typically the shocks just control the speed at which the spring compresses and rebounds, not the distance. So it sounds like you've got a tired spring. You could replace your spring and use the longer 10" bolts to bring it back down to your desired height but then you run into a safety issue where the bottom of the bolt is below the rim and if you have a flat you can risk tearing out your spring.
The other thing to consider is that when your half shafts start pointing upwards it puts a lot of stress on those u-joints. So if you've got any decent power there's another reason to keep your half shafts from going past horizontal. That's one of the first things a drag racer does to a stock c3 rear suspension: keep the shafts limited to only going horizontal.
The other thing to consider is that when your half shafts start pointing upwards it puts a lot of stress on those u-joints. So if you've got any decent power there's another reason to keep your half shafts from going past horizontal. That's one of the first things a drag racer does to a stock c3 rear suspension: keep the shafts limited to only going horizontal.
Supporting Vendor
Joined: Mar 2008
Posts: 576
Likes: 3
From: Muskegon MI
There's no 'real' answer to that. If you were asking from an NCRS perspective you should have more. If you're asking from a looks perspective then it's up to you. If you're asking from a performance perspective then it depends on the setup. But no matter what, you shouldn't be hitting the bump stops except for under extreme conditions. If you like the height it is now, then you could possibly put in some stiffer shocks but that may still not help you. Typically the shocks just control the speed at which the spring compresses and rebounds, not the distance. So it sounds like you've got a tired spring. You could replace your spring and use the longer 10" bolts to bring it back down to your desired height but then you run into a safety issue where the bottom of the bolt is below the rim and if you have a flat you can risk tearing out your spring.
The other thing to consider is that when your half shafts start pointing upwards it puts a lot of stress on those u-joints. So if you've got any decent power there's another reason to keep your half shafts from going past horizontal. That's one of the first things a drag racer does to a stock c3 rear suspension: keep the shafts limited to only going horizontal.
The other thing to consider is that when your half shafts start pointing upwards it puts a lot of stress on those u-joints. So if you've got any decent power there's another reason to keep your half shafts from going past horizontal. That's one of the first things a drag racer does to a stock c3 rear suspension: keep the shafts limited to only going horizontal.
-Andrew
Thread Starter
Le Mans Master
Joined: Jan 2006
Posts: 6,505
Likes: 139
From: Butler Pa
You also run the risk of pulling the side yokes right out of the rear end. The 10" bolt is usually a last resort option, for the reason stated above, but it is the easiest way to correct a ride height issue. If you plan on replacing the spring please let us know.
-Andrew
-Andrew
It seems that I just have the ride height set too low.
Why would it pull the side yolks out of the rearend?
Melting Slicks
Joined: Nov 2001
Posts: 2,659
Likes: 7
From: Katy (Houston) TX
CI 7-8 Veteran
The spring is fine, still has plenty of arch, hence the 8" bolts. I should clarify, it only bottoms out on one short stretch of road that I have no choice but to use. This road is literally falling apart.
It seems that I just have the ride height set too low.
Why would it pull the side yolks out of the rearend?
It seems that I just have the ride height set too low.
Why would it pull the side yolks out of the rearend?
It sounds like you just need a stiffer spring. The stock spring is pretty plush compared to most of today's sports suspension. I had a stock small block spring on mine when I put in a 383. With just north of 400hp I was squatting so low on launches that with my 275/60/15 drag radials I cracked my driver's side fender.
Thread Starter
Le Mans Master
Joined: Jan 2006
Posts: 6,505
Likes: 139
From: Butler Pa
If you have a flat tire, instead of coming down on the rim you'd be coming down on the 10" spring bolt. Depending on how that bolt digs and catches the pavement it can grab hard enough and rip stuff out of everything it's tied to....including the swing arm and up into the half shafts and rear-end.
It sounds like you just need a stiffer spring. The stock spring is pretty plush compared to most of today's sports suspension. I had a stock small block spring on mine when I put in a 383. With just north of 400hp I was squatting so low on launches that with my 275/60/15 drag radials I cracked my driver's side fender.
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Drifting
Joined: Jul 1999
Posts: 1,542
Likes: 43
From: Plano TX
I lowered my car so I had to remove some of the bump stop material so I could keep a 1.25 measurement from pad to bump stop. The bump stop will travel at extreme travel.
I always set the ride height frame to ground setting ride height through spring bolt. A longer spring bolt would actually lower the car further decreasing the free space at the bump stop so you have the right bolt at 8". Free space also depends on spring rate as higher spring rate can tolerate less free space.
I have my 80 setup so I end up with camber gain as the half shaft goes upward over horizontal because I use it for road race track days.
I always set the ride height frame to ground setting ride height through spring bolt. A longer spring bolt would actually lower the car further decreasing the free space at the bump stop so you have the right bolt at 8". Free space also depends on spring rate as higher spring rate can tolerate less free space.
I have my 80 setup so I end up with camber gain as the half shaft goes upward over horizontal because I use it for road race track days.
