question on rear suspension

[Belgian1979vette]

I have gotten the impression that my rear suspension has settled somewhat. Driven about 1000 miles with her, so this was somewhat to be expected.

I'm using 8" bolts in the rear and it seems that the rear is to low right now. As I'm using the 550 front end springs, the car is also lowered in the front. The front is about 1.6" lower and the rear about 1.4" after I turned the nut up today.

However I have very little distance between the rubber stops on the frame and the trailing arm. I've already experienced them hitting when going over a speed bump. What's the solution here ? Cut the bump stops ?

What about the stops in the front ? Same problem ? Same solution ? Any drawbacks for the shock travel ?

 

[Kid Vette]

Rear height should be set by the position of the half shafts. Greenwood recommended they be 1/2" higher at the differential than at the TAs to minimize the effects of toe steer.

 

[Belgian1979vette]

If you set it to the factory height in the rear, it leans down in the front due to the 550's being 1" shorter.

I think both in the front and back the bumper stops are too close to the frame or trailing arm.

I was thinking of cutting the bump stops. But apparently this makes them harder and cut cause damage to the frame.

 

[Kid Vette]

Lower in front gives you a little down force, right? Greenwood also recommended cutting the bump stops but I'm not sure if I would do that.

 

[JPhil]

Remember, your bumpstops are progressive in their snubbing due to the pyramid shape. If you cut them shorter by whacking the bottom point off, when they do make contact it will be much more jarring to the arms & frame.

With the car lowered, you're just going to lose suspension travel. That's just a fact.....

 

[Belgian1979vette]

How much is the actual suspension travel on our cars ?

 

[JPhil]

Wow, I just went and checked---with my front fender lip at 27 1/2" (69cm) above the floor, I have about 1 1/2" (3.8 cm) from a-arm to bump stop. Rear fender lip at 28" (71 cm), I have only about 1" (2.5 cm) clearance to t-arm! That's precisely measured by sticking my fingers in between them.....The stiff shocks & springs keep it from bottoming out too often, but I know I hit the bump stops a lot. Just part of the deal, it ain't a Buick.

A few years ago I bought rear tires that were too wide and had to jack the back up to clear the fenders, with the front still lowered with the 550 springs. It looked all jacked up like a street rod, but to my eye, being a Corvette, the stance made it look like a female cat in heat. It also ruined the rear end handling--it wobbled and swayed around like a big ass ho. Those tires came off quick and I got the back end lowered down again to where it handled properly.

On the 'to do' list is raise the diff to correct the rear toe steer I now suffer from.

 

[Belgian1979vette]

Wow, I just went and checked---with my front fender lip at 27 1/2" (69cm) above the floor, I have about 1 1/2" (3.8 cm) from a-arm to bump stop. Rear fender lip at 28" (71 cm), I have only about 1" (2.5 cm) clearance to t-arm! That's precisely measured by sticking my fingers in between them.....The stiff shocks & springs keep it from bottoming out too often, but I know I hit the bump stops a lot. Just part of the deal, it ain't a Buick.

A few years ago I bought rear tires that were too wide and had to jack the back up to clear the fenders, with the front still lowered with the 550 springs. It looked all jacked up like a street rod, but to my eye, being a Corvette, the stance made it look like a female cat in heat. It also ruined the rear end handling--it wobbled and swayed around like a big ass ho. Those tires came off quick and I got the back end lowered down again to where it handled properly.

On the 'to do' list is raise the diff to correct the rear toe steer I now suffer from.

Front is the same with mine. Rear was a bit lower at 69.5cm. Just raised it some. I only have a few fingers I can put in between.

I've experienced some erratic suspension movements before, like under hard acceleration in a corner, I've noticed it suddenly jump out in the left front. Could be that she was going on the stops at the time, hard to tell.

There is a measurement that calls for a 8.58 (22 cm) measurement of the moulding for the rocker panel to the floor. I now have about 19 there. So basically she would need to move up about 3 cm.

I don't know how much clearance this is going to give at the stops. I'm going to try and jack her up behind the front wheels and in front of the rear wheels to get that measurement and see what the difference is. If it's not too big I can shave the bushings some. However if it's an actual 3 cm difference I'm looking at, there won't be much left of them so that would be a no go.

That would leave me with the following options :
- using spring spacers in the front and return to the stock spring bolt in the rear.
- find myself a good set of Original gymkhana springs of correct height.

I want to keep the 550's up front.
I'm not sure I understand why all of those aftermarket 550's are shorter, unless this is done to be able to use a softer spring that is cut to provide 550 lbs of pressure. Dodgy way of doing that I think.

 

[MYBAD79]

What rear spring are you using? It's not really abnormal for a spring to somewhat settle..... Add a few washers if you want to raise the rear a little bit.... Why not ??

 

[Belgian1979vette]

What rear spring are you using? It's not really abnormal for a spring to somewhat settle..... Add a few washers if you want to raise the rear a little bit.... Why not ??

I can put the bolt higher so that's not the issue. But then the stance is with the rear higher than the front. My front springs are what determined the height on my car. They put the car about 1.6" lower in the front.

That on itself wouldn't have been such an issue, but the suspension travel is rather limited and I suspect the car riding the stops more than a couple of times.

Going to measure today how much difference there is between the stops and the frame in normal position vs the oem determined height. If it's not overly large, i might start cutting the stops.

 

[Belgian1979vette]

Did some measurements.

At correct ride height as per AIM: the travel on the front is 50-55 mm and in the rear 30-37 mm.

With the suspension being lower and equal front to rear, I only have about 30-35 mm in the front and 15-19 in the rear (which I already set a bit higher, so I guess it was thoughing the stop before).

The bumper stops would effectively need to be shortened aroun 20 mm in the front and rear, which in effect cuts them in half.

I think I'm going to try and find myself the correct height front FE7 coil springs and us my original spring bolts again.

Guess that my lower ride days are over.

 

[BBShark]

Is the travel (from the AIM) measured at the wheel? If so, the travel at the bump stop position will be proportionally less.

 

[Belgian1979vette]

Is the travel (from the AIM) measured at the wheel? If so, the travel at the bump stop position will be proportionally less.

I placed the rocker panel cover at the height as per AIM. I measued in the 'normal' ride height vs the height as per aim with play doh pushed between the bump stops. Difference is what I lost.

 

[Belgian1979vette]

To add to this : I think companies like VBP are screwing with us. I believe the springs they advertise as 550 lbs are actually 460's with 2 coils cut off. No wonder the car lowers. Those VBP 550's actually seem to measure 13" free length but so does a factory FE7 550. So the pounds are not correct otherwise it would not sink to the ground like it does.

Just ordered a package with an original FE7 front kit (coils, stabiliser and bushings).

Next is an original rear stabiliser and then I'm going to throw the damn long bolts out of there as well.

Looks will be a little less, but I want a suspension that works an not one that sits on rubbers.

 

[Sam Cogley]

1) what rear spring are you running with the 550 fronts?
2) with some shopping around, you may be able to find shorter bump stops that will fit from a different car.

 

[Belgian1979vette]

7 leaf

I have not come across a different bumper. Cutting them only makes them stiffer and impacts harder when they hit.

 

[phantomjock]

Might give a look at these guys:
http://www.energysuspensionparts.com/Energy-Suspension-Universal-Bump-Stops-Shock-Eyes.asp


Cheers - Jim

 

[mrvette]

Back in '95 I had the rear suspension totally rebuilt because I didn't know jack about it.....Tony's Corvette shop in G'burg Md.....I used Energy suspension for the front bushings, and the rear spring was proven to be a great choice for ME at 360 lbs....with Bilstein sport shocks....street driver, not raced.....
the rear is stock rubber bushings.....on the arms....but I have a plastic 360 spring in rear.....same shocks.....

Except for the eventual failure of the upper CA bushings I replaced them myself with stock rubber inserts....fine, and with a cross support....for some years now....

And yes, I would like to lower the car a bit, but have NO clue how to do it without maybe rubbing the larger tires on the fenders.....and if I cut springs, I can't just magic redo them.....:shocking::ill:

 

[MYBAD79]

To add to this : I think companies like VBP are screwing with us. I believe the springs they advertise as 550 lbs are actually 460's with 2 coils cut off. No wonder the car lowers. Those VBP 550's actually seem to measure 13" free length but so does a factory FE7 550. So the pounds are not correct otherwise it would not sink to the ground like it does.

Back in 2005 or so I bought and installed the 460's from VBP, got the classic 4x4 look .... I think the photos I posted back then made it three times around the world .... Lol
I then installed the 550's with Bilstein shocks and that was a great combo, ride height was perfect, not slamned to the ground at all

Since then i installed front and rear fiberglass springs, that's another step up ....

I think the VBP 550 coils are really good springs for the front of a C3 , I doubt they're just cut up 460's as I've seen both side by side ...

 

[JPhil]

The 550 is the same spring as the 460, but with fewer coils, thus making it a stiffer rate. I too went with the 460s first. Great improvement in handling over the stock whatevers, but yeah--it raised the front so far it looked like an old straight axle gasser. I whacked the coils but didn't like the way it seated in the pocket then. The 550s are at least a couple inches shorter than 460s, and probably an inch or more shorter than the stock. Considerably stiffer, but I'm used to it and appreciate the improved handling. Maybe I'll look into some of those aftermarket bumpstops.

I have a collection of springs in the attic--stock big block, stock small block, cut 460s, uncut 460s, and a couple other pairs too. And a couple old steel rears. And several sway bars. All just a bunch of metal sculpture parts far as I'm concerned.

 

[Belgian1979vette]

I raised the car under the rocker panels with jacks both front and back. If I can get it close to the AIM curbed values the height is just right. Could have been a tad lower, but overall the stance is not that bad, very stock looking.

Like I said, riding on those rubbers is dangerous. During one of my rides, I was cornering and accelerating. Car probably went on the rubbers on the outside corner, due to the engine being in its power band and the cornering power due to the speed. I was attentive enough to get my foot off the throttle or I would have ended up in the ditch besides the road.
On a second occassion I was driving over a speed bump (low, but not very low speed as I usually do). Car went down on the rubbers in the back which I felt like a blow in my back, bounced back immediatly and became very unstable in the rear.

Only way to prevent that was with the koni's on highest setting, but that was like driving with no suspension at all. Hard as rock.
We have some concrete roads here. They are concrete because the Leopard tanks go over them a lot. Not the most even road, but when I went over those with the koni's at the highest setting, my teeth would rattle out of my mouth, that hard kind of suspension setting.

Wil see what the stock spring buys me for ride height. Got me a pair of 78 Original FE7 springs and FE7 front stabiliser bar + back to the rubber bushings (as I believe that the rubber provides some friction to the rotating motion of the bar where the poly doesn't do jack in that area but keep the bar in place.

Luckily I've got my own alignment rack to deal with the realignment afterwards. So besides a couple of hundred dollars the rest is work.

 

[Belgian1979vette]

Might give a look at these guys:
http://www.energysuspensionparts.com/Energy-Suspension-Universal-Bump-Stops-Shock-Eyes.asp


Cheers - Jim

Thanks for that link.

Need to keep them below 1". Those with that height are only the round ones with no progressive rate. I can hardly imagine something like that doing something in the sense of dampening the blow when the suspension does bottom out.

You'd be surprise to see how little suspension travel there still is with the car lowered. In the back I can hardly get 2 fingers between the arm and the stops. In the front maybe 2 and a half fingers.

 

[Belgian1979vette]

Back in '95 I had the rear suspension totally rebuilt because I didn't know jack about it.....Tony's Corvette shop in G'burg Md.....I used Energy suspension for the front bushings, and the rear spring was proven to be a great choice for ME at 360 lbs....with Bilstein sport shocks....street driver, not raced.....
the rear is stock rubber bushings.....on the arms....but I have a plastic 360 spring in rear.....same shocks.....

Except for the eventual failure of the upper CA bushings I replaced them myself with stock rubber inserts....fine, and with a cross support....for some years now....

And yes, I would like to lower the car a bit, but have NO clue how to do it without maybe rubbing the larger tires on the fenders.....and if I cut springs, I can't just magic redo them.....:shocking::ill:

Well, lowering is not the real problem. A 550 lbs up front and a longer bolt in the back and you're there + suspension alignment.
However, you'll end up with what I have here right now. It's good for looks but it rides like **** if you get on her good.

Everything I've done to my car can be undone for this reason. Call me crazy, but it saved my butt a couple of times already.

I'm about to believe that those engineers at GM didn't fubar our cars as much as we believe. Not everything is done for beancounters, although we would like to believe that.

 

[Sam Cogley]

All of the steel rear springs suck, IMHO.