Bump stops

[snowborder714]

I need to purchase bump stops for my DG suspension setup. I will have at least a 600 spring in the front and 300 in the rear. I'll probably get Koni stops unless someone else has a recommendation.

Koni has 2 options for a shock with a 12mm rod diameter. They are linear soft (45mm length) and progressive soft (55mm length). From talking to a tech guy at Koni he said if possible, he would recommend the progressive soft. But I would need to make sure I can give up an extra 10mm of shock travel.

So, if anyone knows if one of these won't work because of the suspension travel, I'd like to know.

Also, if anyone has experience with both types of bump stops, any input would be helpful.


It looks like DG uses the linear soft, but I'm not 100% positive.

You must be logged in to view this image or video.

You must be logged in to view this image or video.

 

[greengoblin]

A progressive soft would be better for sure. Can't you just trim off extra 10mm? Or is that needed to make them progressive?

 

[snowborder714]

The guy at Koni would not say anything when I asked him that question. His response was "That's a question for a spring guy." I'm thinking, ok I understand that, but I was questioning more to what you mentioned - is it ok for the bump stop or will it affect performance.

I may just get them any try trimming them if need be. It looks like the one side in the above picture can easily be trimmed. They're only about $13/stop, so it wouldn't be a huge loss.



Any one know how to tell if your bump stop is the proper length, or if it's too long/short?

 

[turbosax2]

From Koni's site:

Modifying Bump Rubbers

The tapered end of the bump rubber helps to provide its progressive nature. If it is neccary to increase shock travel, trim the non-tapered end of the bump rubber.

 

[snowborder714]

Well, that confirms my thoughts on what side to trim if need be.

I'm guessing no one is going to know about the length and shock travel though.

 

[snowborder714]

Would this be a valid way to check if the bump stop length is too long? Or would this strictly be for ride height?
http://www.dsmtuners.com/forums/1544856-post5.html

 

[wasabi37]

I just installed my rear koni shocks last weekend. and I don't even have enough length to put my original bump-stop in. So I just left it without. I also wonder if it has any ill effect??

 

[snowborder714]

I believe most people cut the OEM ones to size for Koni installs.

 

[Weapon-X]

It's really gonna be hard to say what will be right and what will be wrong

Are you gonna have a lowered static ride height?

Are you gonna have an OEM ride height?

Your answer to the above questions will likely determine what bumpstop to use.

I'm sure you all ready know, but 10mm of travel on our suspension is a lot. And that measly 10mm becomes an even greater amount so to speak if your taking some away by inducing a lower then OEM ride height.

I can give my suggestion if you let me know where your at on your ride height alone EXAMPLE .......... OEM height..... 1" lower..... 1 1/2" lower.....etc.

 

[bjones18]

Bump stops are just that.

If you will not bottom out your suspension... you don't need them. Problem is... who plans on hitting a pot-hole.

I prefer a progressive load-displacement curve. To compare bumpers look at the corregated design as a cross-section. The "minor" diameter sections will compress first (fully). When they are compressed the "major" diameter will start compressing.

So visually, you can look at the minor diameter and major diameters and compare them with other bumpers.

Soft entry bumpers provide the best (progressive-predictable) response if you hit a bump in the corner.

An overly soft bumper (or lack there of) will not provide protection for your body attachments as your sprung mass flys-up and slams into the upper mount. Applied[F=ma (a=deceleration in this case)] and dissipative[F=Kx] where K is the bumper stiffness and x is the bumper length. You will not change the F=ma part of the equation (unless you drastically reduce sprung mass... or install large section height tires).

So... protection from potholes comes from a good sized jounce bumper; and predictable handling (under various passenger loading and road surfaces) depends on a soft entry, progressive bumper. A non-progressive bumper allows more free-travel before engagement (but this engagement can be suprising, and does affect under/over steer in a corner).

Reducing ride height (lowering springs) reduces your "playground" for tuning this behavior. On the better side, most of us are not tuning for four passenger, with loaded trunk handling.