Aftermarket bump stops

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Aftermarket bump stops

Postby Aure » July 29th, 2010, 1:19 pm

Hi guys!

I got these Fatcat Motorsports 36mm bump stops. The guy states that if you use those on Koni Sport shocks, you need to use spacers to prevent the shaft from hitting the bottom of the body. Now, FCM bumpstop + spacers is as tall as the stock bumpstops. So there is not gain in travel installing them.

Any feedback on this? It seems strange to me to have to put the spacers and I'd rather remove them to gain travel. But only if safe.
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Re: Aftermarket bump stops

Postby NicholasJay » July 30th, 2010, 5:47 am

I believe the spacers are there to prevent the shock rod from bottoming out in the body (like you said). If that is the case, then removing them won't increase travel, it would just damage the shocks.

I have the FCM 46mm bump stops on my car and all of the required spacers with FM springs.

If you want to gain travel, the tophats are the place to do it.
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Re: Aftermarket bump stops

Postby bill_keksz » July 30th, 2010, 7:10 am

OTOH, FM discouraged their rear top hats with aftermarket springs and Koni sports - coil bind, IIRC?
But they don't with stock springs. So I'm confused...
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Re: Aftermarket bump stops

Postby ChristianL » July 30th, 2010, 8:04 am

I've been with two NAs with Konis/Ground Controls and FM rear mounts - possibly one of the best setups I've experienced.
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Re: Aftermarket bump stops

Postby thebeerbaron » July 30th, 2010, 9:10 am

bill_keksz wrote:OTOH, FM discouraged their rear top hats with aftermarket springs and Koni sports - coil bind, IIRC?
But they don't with stock springs. So I'm confused...


I want to say those were those half-arsed progressive springs that were meant to be run with stock shocks. I haven't checked for signs of coil bind, but I think I would have noticed it. Pretty sure I've bottomed the car out in the Shenandoah Karoussel, but that was tires hitting fenders, not the sudden-infinite-spring-rate of a bound spring. Have to agree with CL, those top hats are sweet.
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Re: Aftermarket bump stops

Postby Aure » July 30th, 2010, 9:35 am

I got NB top hats front and rear. That's what Chris Windsor suggested to increase travel. The car is feeling great. I was just curious to see if I could get even more travel.
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Re: Aftermarket bump stops

Postby NicholasJay » July 30th, 2010, 9:40 am

Aure wrote:I got NB top hats front and rear. That's what Chris Windsor suggested to increase travel. The car is feeling great. I was just curious to see if I could get even more travel.


Taller springs would help :)
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Re: Aftermarket bump stops

Postby prostwest » July 30th, 2010, 11:57 am

Remember that the compliance of the bumpstop material and its construction can be as important as its length. As an example, one brand might provide only x compression distance before offering essentially infinite resistance, while another brand with the same static length may still be progressively increasing resistance at x, only stalling at 2x deflection. In that example, one 36mm stop might "bottom out" at 31mm, while another 36mm would give down to 26. Proper spacing would be more critical in the second example, since the extra 5mm could easily mean coil bind, tire clearance problems, etc.
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Re: Aftermarket bump stops

Postby NicholasJay » July 30th, 2010, 12:15 pm

prostwest wrote:Remember that the compliance of the bumpstop material and its construction can be as important as its length. As an example, one brand might provide only x compression distance before offering essentially infinite resistance, while another brand with the same static length may still be progressively increasing resistance at x, only stalling at 2x deflection. In that example, one 36mm stop might "bottom out" at 31mm, while another 36mm would give down to 26. Proper spacing would be more critical in the second example, since the extra 5mm could easily mean coil bind, tire clearance problems, etc.


I whole-heartedly agree with this. That's partially why the stock NB bumpstops are better than the NA stock bumpstops (NA bumpstops are hard rubber, while the NB bumpstops are foamy). I can't separate the bumpstop variable from the rest of the suspension upgrades I did at the same time, but the car doesn't crash over bumps like it used to.
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Re: Aftermarket bump stops

Postby ChristianL » July 30th, 2010, 12:17 pm

If anyone wants to see NA vs. NB bumpstops, I've got a set of each. And yes, they're drastically different.
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