[HalcYoN]

Recent threads over at Roadfly about shipping blocks left by vehicle prep got me thinking about replacing/upgrading the rear spring bumpstops to give things a little more progressive spring rate at the limits and a bit earlier influence. I was thinking of H&R/Bilstein set up but since my car is mainly for touring (may get a kart to appease racing bug) I don't want to sacrifice ride quality too much.

The rear spring have rather feeble looking bumpstops on them. How are they mounted? I have found several off-road bumpstops that are pre-threaded and was wondering if these are similar to those on our coupes. http://www.suspension.com/Bumpstop.htm

Looks like this could be a quick and painless suspension upgrade to prevent rear coil binding and makes things a little more forgiving.

FYI, I have found that the Miata relies heavily on bumpstops as a means to give smooth ride and progressive feel.

 

[Daver]

The stock rear bump-stops just slip over the top spring locating post:

NOTE: this was on my Roadster... the initial coil I got was too soft and too short (6", 2.25" diam, 425 spring-rate). I ended up with a 7 x 2.25", 450 on that car, and a 6 x 2.5, 525 on the Coupe).

It's the black cone-shaped thing inside the coil at the top... it also acts as the upper coil pad. It's sort of like an inverted safety cone.

It shouldn't be too difficult to come up with something to work in it's place. The pad portion could be retained just by slicing off the bump-stop, but you'd need to find some way to affix the new bump-stop in place.

I'd be very interested in this as well... though I'm running 2.5" barrel coils (525 spring-rate), I can manage to get coil-bind in extreme cases. I'd much rather have a bump-stop coming into play rather than binding the coil (bam!).

 

[HalcYoN]

Perhaps the easier solution would be to place something in the lower spring mount that would cause the stock stop to come into play a bit earlier.

Unfortunately, I'll be out of town this weekend so I won;t have time to research it, but I may have a chance to stop by an off-road parts warehouse soon to check out our options.

 

[HalcYoN]

Well, aftr talking to local guy, I amy try to investigate by dropping out the spring. I have two options; add a disc bumpstop to the bottom to force the stock stop to come into play earlier or replace the top stop.

Since the top stop is part fot he spring perch, looks like door #1...

 

[Ron Stygar]

Pads part pic

 

[HalcYoN]

Thanks for the info, Ron.

Looks like I could add to the lower pad. Hmmm...

 

[caylan]

It looks like from Ron's parts list that

Thanks for the info, Ron.

Looks like I could add to the lower pad. Hmmm...

BMW has a lower & upper "bump-pads" available.

Would you get those or would you try getting a different application?

 

[HalcYoN]

caylan,

I was looking at a lower spring perch pad designed for a Jeep aftermarket suspension system. They had several height options and they simply slipped into the base of the coil springs.

 

[caylan]

Let us know how it goes w/ pixs too!

caylan,

I was looking at a lower spring perch pad designed for a Jeep aftermarket suspension system. They had several height options and they simply slipped into the base of the coil springs.

Interesting. This would probably great for city driving.

But whatabout Auto-X & track purposes... would it take away from any aftermarket susp. mods? I wonder...

 

[HalcYoN]

Most coilover kits (at least from Ground-Control) have some form of bumpstop, either in the spring or on the strut. The H&R springs have enough spring rate that in combination with the Bilstein Sports, they should not bind.

I figure, if we can get rid of the most twitchy moment, rear coil bind, the stock suspension will do fine for occasional track events but maintain its civility when on road trips. Just thinking outside the norm...

 

[killeen_john]

Brian,

Did you ever try out the bump stops? I'm thinking about getting another set of the upper spring pads (33531093935) with integrated bump stop for use on the bottom. Then hopefully the upper/lower bump stops would contact each other before my H&R rear springs bind.

 

[TeamM3]

the BMW bumpstop is on the shock/strut shaft, you should NOT run without them. You can buy them in various lengths, stiffness and shape configurations for tuning. Koni sells a number of them.

 

[ShifterKart Guy]

Asked Jeff at Ireland Engineering and

I asked if they used a lower bump stop on the E 30 rcing cars they run. He said no they don't, and that a little sign of metal binding on a HR Race sprong is normal.

I have noticed that the car appears to sit 1/4 to 1/2 inch lower in the rear than the front.
I wil measur ethis today.

Thoughts were that adding a lower bump stop to the spring perch might raise the car that 1/4 inch?

I do not think my springs are binding- the rear does not seem to have a lot of travel and when go over ...say a RR tracks- the car has a harsh thump in the back- I figured thats the price of stiff suspension on the street.

Am I correct in assuming that bump stops are more fior cars with softer spring loads and street shocks / struts to keep them from bottoming?

thanks

 

[dwm]

I asked if they used a lower bump stop on the E 30 rcing cars they run. He said no they don't, and that a little sign of metal binding on a HR Race sprong is normal.

I have noticed that the car appears to sit 1/4 to 1/2 inch lower in the rear than the front.
I wil measur ethis today.

Thoughts were that adding a lower bump stop to the spring perch might raise the car that 1/4 inch?

I do not think my springs are binding- the rear does not seem to have a lot of travel and when go over ...say a RR tracks- the car has a harsh thump in the back- I figured thats the price of stiff suspension on the street.

Am I correct in assuming that bump stops are more fior cars with softer spring loads and street shocks / struts to keep them from bottoming?

thanks

I think the wording is a little confusing here. When I think of a bump stop, I think of the bump stop on the strut as TeamM3 noted. What's on the spring perch I call a spring pad. And to the best of my knowledge, the spring pad isn't intended as a bump stop or to prevent the coils from binding. It's shaped the way it is to keep the spring centered (or if you've got much shorter springs, from falling out ) when the rear suspension is unloaded.

Yes, you can run thicker spring pads to change the height. Or you can buy height adjusters.

 

[TeamM3]

well you wouldn't see spring contact wear if the shocks were bottoming out first

or in a full boat racing setup it could be possible to have springs so stiff coupled with enough shock compression travel range that they'd never bottom

from the Koni Motorsport Catalog (not the street shock catalog), it's not uncommon to use bumpstops for racing, properly setup it serves as a secondary spring. The SCCA revised it's Stock class shock rules several years back because they learned people were using bumpstops to create a stiffer spring rate, now the compressed length of the shock at the point where the bumpstop touches cannot be longer than the same OE length

 

[ShifterKart Guy]

appreciate the clarification

I think the wording is a little confusing here. When I think of a bump stop, I think of the bump stop on the strut as TeamM3 noted. What's on the spring perch I call a spring pad. And to the best of my knowledge, the spring pad isn't intended as a bump stop or to prevent the coils from binding. It's shaped the way it is to keep the spring centered (or if you've got much shorter springs, from falling out ) when the rear suspension is unloaded.

Yes, you can run thicker spring pads to change the height. Or you can buy height adjusters.

That makes more sense to me know. I did some digging in my notes and found that the front strut had a 3/4 inch bump stop removed to accommodate the lower ride height. That is recommended by H&R it seems with thier Spring kits.

The rear Spring Pad is OE Config- so if I add a lower pad or thicker pad, I will effectively raise the rear end the 1/8 to 1/4 inch I would like- great thanks for the clarification.

 

[TeamM3]

that's the bassackwards method

the correct method is to shorten the overall shock/strut length and retain a proper bumpstop. This way you don't get quirky, unpredictable handling issues like you do with a reduced/eliminated bumpstop causing spikes of near infinite spring rate when it bottoms out

 

[ShifterKart Guy]

one would think

better- I would hope that H&R and Koni would have developed components that work together properly without having to reengineer the parts.

If the spring is shorter and I shortened the length of the strut- I would still need to shorten the length of the bump stop?? otherwise it would come into play too soon shortening the travel?

I am using the Koni Sport with the HR Sport Spring ( I assume that they are the progressive race spring since they are red). As per H&R the front bump stops were cut down 3/4 inch to accommodate.

Is this wrong?

I was looking for the spring load rate of the H&R- if anyone knows please provide-thanks

 

[dwm]

better- I would hope that H&R and Koni would have developed components that work together properly without having to reengineer the parts.

If the spring is shorter and I shortened the length of the strut- I would still need to shorten the length of the bump stop?? otherwise it would come into play too soon shortening the travel?

What TeamM3 is trying to emphasize is that you should always have a bump stop, and shaving 3/4" off of it isn't a great idea. He's also not talking about re-engineering what you currently have; he's saying that if the desired result is to lower the car, the lower spring perch should be lower and the strut housing should be shorter (or you should run coilovers with adjustable ride height). Shortening just the spring, without having a lower spring perch and shorter strut housing, reduces your travel. Trying to get it back by shaving off 3/4" of the bump stop leaves you with less progressive behavior in the bump stop. Bump stops are usually shaped somewhat like a cone to provide progressive rates when they bottom. Shave off the top 3/4", and you lose a lot of the progressiveness and get close to feeling like there's no bump stop at all (as TeamM3 said, sudden infinite spring rate). That said, I don't have Konis so the bump stop might be engineered differently (might be progressive on the bottom instead of the top).

I am using the Koni Sport with the HR Sport Spring ( I assume that they are the progressive race spring since they are red). As per H&R the front bump stops were cut down 3/4 inch to accommodate.

Is this wrong?

It depends on what you think of as 'wrong'. It might be the way H&R/Koni is set up (I'm running KW V3, so I don't know). An open question is whether or not the coils bind before the bump stop is hit. In either case the result is near infinite spring rate. The objective is of course to only rarely bottom out, and never at the track.

 

[dwm]

That makes more sense to me know. I did some digging in my notes and found that the front strut had a 3/4 inch bump stop removed to accommodate the lower ride height. That is recommended by H&R it seems with thier Spring kits.

I believe some other folks that have run H&R springs up front have had bottoming issues with stock-length struts. GC makes a strut that's 1" shorter with a Koni insert to eliminate this problem. Ask QikSilver about it over on bimmerforums.

The rear Spring Pad is OE Config- so if I add a lower pad or thicker pad, I will effectively raise the rear end the 1/8 to 1/4 inch I would like- great thanks for the clarification.

Why not just install a height adjuster in the rear? I like the ones that came with my KW V3, they mount on the top instead of the bottom so they're easy to adjust in-situ and don't have that about-to-tip-over look when set high (which made me nervous about any of the ones I've seen sitting on the trailing arm).