99Bluz28

iTrader: (35)

I've got exactly what he needs right here:

99Bluz28

iTrader: (35)

Here's some Energy Suspension bump stops I came across that look like they would fit in the rear with little , or no modification.

http://www.energysuspensionparts.com...sp?prod=9.9137

JasonWW

iTrader: (2)

I have a feeling these are going to be much stiffer than we want. Polyurethane can be made in numerous levels of hardness. Even if they make these really soft, it's still going to be too rubbery. You want long and progressive bumpstops, not these.

99Bluz28

iTrader: (35)

Your very correct! You don't want you rear axle to close to these bump stops when going down a bad road! I now know from experience, that's why I just put my cut-down factory bump stops back on. But on the other hand their still better than no bump stops at all.
For stock ride height, and drag racing I think the E.S. bump stops would work fine.

wannafbody

iTrader: (2)

I have the longer bumpstops on my Miata. Some claim that when fully compressed the rate shoots up to 600# and some go as high as 900#.

JasonWW

iTrader: (2)

No, when fully compressed they become like a block of metal and can withstand many thousands of pounds because there is no give left in them. When you run out of bumpstop travel and the wheel wants to keep compressing, then things like the A-arm and chassis flex as well as the tire compressing more until something catastrophic happens, like the tire gets pinched between the ground and the rim or a suspension piece breaks (shock, shock mount, a-arm etc...)

wannafbody

iTrader: (2)

Here's a graph

http://www.fatcatmotorsports.com/iga...6_46_NA_63.JPG

JasonWW

iTrader: (2)

There's something screwy with that graph. How can a 46mm bumpstop be compressed more than 46mm? Maybe they should all start at the same point at the lower left?

Here's a quick correction:

(click on thumbnail)



Once you squish all the air out of the bumpstop, it acts like a solid and the rates jump through the roof. With a well designed suspension you will slow the compression down before the bumpstop is fully compressed. Because once the rates go sky high the suspension no longer suspends, it becomes solid and things can start breaking.

wannafbody

iTrader: (2)

There are 3 different bumpstops graphed there- 36, 46, 63-and ya, once it is fully compressed it goes sky high.

JasonWW

iTrader: (2)

They were not graphed correctly in your link, but I made a correction.

In response to your original post, it's not the actual pounds per inch numbers that are most important. It's the rate in which it compresses. You want a smooth progressive ramp up over the longest amount of travel you can get, combined with a good material that does not want to rebound. Rubber rebounds badly and they make for a bumpy ride. The cellular polyurethene (or microcellular urethane ) used by Koni and other aftermarket companies rebounds very slowly, which means it is not pushing the car up after full compression. It is merely absorbing the compression forces. A rubber bumpstop will compress and then release that energy back with force which is not good for the ride or handling.

BTW, if your fully compressing your bumpstops, it's a sign that either your spring rates are not high enough or your compression travel is too short.

z28bryan

iTrader: (7)

So do you think the square SS/WS6 bumpstops would be easier on your back than the poly bumpstops?

If a particular bumpstop is extremely stiff, does that kind of ruin the point of the bumpstop? Since your not allowing any cushioning, wouldn't that be hurting the mounting point area?

pjb

iTrader: (2)

any bump stop may be better then no bump stop, because you don't want other parts smashing into each other. but clearly softer will give you better ride and less impact harshness.