elwood

iTrader: (1)

I have some ReSpeed adjustable rear springs, and my setup bottoms out on moderate bumps. My jounce bumpers are the original hard rubber ones, with about half their height removed. When the car bottoms out, there's a fairly hard "thud", and I think this will upset the car when it's on the track. I want to try some of the foam progressive jounce bumpers, but I haven't found any that bolt into position, like the OEM ones. The other option is to put them on my shocks, but I don't know if the shock brackets are strong enough to withstand the forces generated.

Also, my rear spring rate is 175#. I'll consider upping the rate, but I want to try the progressive jounce bumpers first, since I'm happy with the handling balance the way it is.

Has anybody upgraded their FB rear jounce bumpers?

Kentetsu

Elwood,

As I posted on your thread in the 1st gen section, I don't really understand how you could be bottoming out. My rear height is very low, and I'm only using 150 Lb springs back there (with the adjustable perches). I've never had an issue, even through construction zones and such. But I'm not sure if I even have the bump stops still installed or not...


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elwood

iTrader: (1)

I believe that foam bump stops are a good thing. If you look at OEM suspension setups, they almost always use them. Unless your spring rate / length is way overdesigned the system will bottom out at some point. When that happens, progressive bump stops will keep you from damaging stuff and losing control of the car. Carroll Smith and many other suspension experts agree. I could raise the rear of the car and eliminate the issue, but that's not the point. If your car doesn't ever bottom out, I'd say you should lower your car for better cornering and add progressive bump stops. No matter what height your car is, they improve the equation.

I found some GM parts, used by the Impala SS guys (of all cars), and I'm going to give them a try. They have a steel cup with the bump stop pressed into it. Looks like the right solution. I'll let you know.

Black91n/a

http://www.fatcatmotorsports.com/

I think many of theirs are just Koni ones. You can just cut off the stock ones and put some universal ones on the shock shafts.

elwood

iTrader: (1)

Thanks for the link, but it's a little different for us live axle folks. The jounce bumper on ours is a free-standing unit that isn't supported by a shock shaft. I'll send a pic when I receive them.

Black91n/a

Is there any reason you couldn't convert to using that style though?

elwood

iTrader: (1)

It would be tough to convert to the shock style jounce bumpers. I don't think the shock attachments are designed to handle the loads a jounce bumper would generate, since the springs on an FB are mounted separately. On the other hand, if I used that style jounce bumper in the OEM location, there wouldn't be a way to mount it.

Here are some pics of the GM jounce bumpers I just received (PN 15956547). They come with the steel mounting cup, and they're spongy, so they basically make the springs progressive. I think I'll be able to screw them right into the perches where my OEM pieces were.