Bilstein Lowering Stop-rubber Issue

[goldNSX]

Recently I went for new Bilsteins (ok, 3rd set :wink and had the impression that the ride was bouncier than before. Why this?

Before I used Zanardi springs, F -2 cm, R -0.7 cm and shortened Bilsteins (shock BODY was 2 cm shorter).

Now I run the same springs but Bilsteins with untouched body length but with rebound.

That's the height of the car, not very low actually but too low is not fast anymore IMO. The tires are small 205/40/16 and 245/40/17

 

[goldNSX]

I undid the blue rubber protector of the Bilsteins to see how much way there is between the shock body and the stop-rubber. In the front it was nearly touching, in the rear it's about 1.5 cm. But as you can see on the rear (second pic) the stop-rubber was quite a few times touching the shock-body in the last 500 km since install.

Bilstein advises NOT to use the lower perch on the shocks with lowering springs. Now I know why! This means that anything lower than my car is always running in the stop-rubbers (what a word! ). This may give the car a go-kart-feeling but it's not nice for the chassis and for the driver (bouncy).

 

[goldNSX]

This is a comparison of the Bilstein to the OEM shocks. The body of the front Bilstein is slightly shorter.

My intention: I'd like to give it more suspension travel which should reduce the bounciness a little bit. Too much will result in touching of the wheel to the inside of the fender which is not good. Are there any other restrictions? I don't see any. I could cut the existing stop-rubber by about 1.5 cm to give it more travel. Or I could use another stop-rubber material (black) which is much less flexible but would allow me 2 cm more travel. BTW the OEM stop-rubber is more flexible than the Bilstein thingies. What would you do?

 

[Big_D]

Great info gold, thanks for taking the time to post. I am considering bilsteins on lower perch with factory springs...seems to be the best combo for the buck. I think am running on original struts. I have no record of them being changed by previous owners. They are amazingly good for how old they are.

 

[goldNSX]

I decided on cutting the Bilstein bump-stops from 4.5 cm down to 3 cm by cutting away the most flexible (= lower) part of it. I've installed the shock without the spring and lifted the wheel with a jack till I thought the wheel shouldn't go more within the fender, checked for all other components to clear and measured the distance between the shock body and the upper mounting plate (= the minimal bump-stop height) This was 2.5 cm, as the thing is flexible I've added 0.5 cm = 3.0 cm. This results in 1.7-1.8 cm bump-stop-free compression.

Regarding my findings I guess that a lot of NSX's with Bilsteins or any other shock with the same height as OEM and running lower than mine (it's actually not very low at all) are purely running on the bump-stops. But don't remove them!

@Big_D: For OEM springs and Bilsteins on the lower perch it's not necessary cutting the bump-stops.

 

[valenzul]

I have Eibach's w/ bilsteins on upper perch. I felt it is bouncy as well.

Any follow up w/ cutting the bump stop? Rides better?

Had H&Rs w/ stock struts before and it wasn't this bouncy.

-Val

 

[nis350]

This was 2.5 cm, as the thing is flexible I've added 0.5 cm = 3.0 cm. This results in 1.7-1.8 cm bump-stop-free compression.

Does it mean that your car only has 1.7 to 1.8 cm (.75 in) spring travel? Is this for the front?

If that is the case, I suspect that with other lower springs such as Eibach (1.25 in. drop) would be riding on the bump stopper...???

 

[goldNSX]

I have Eibach's w/ bilsteins on upper perch. I felt it is bouncy as well.

Any follow up w/ cutting the bump stop? Rides better?

Had H&Rs w/ stock struts before and it wasn't this bouncy.

-Val

I had this combo before I've changed to Zanardi/Bilstein lower perch. The ride height is the same in both cases. So the situation with the bump stops is the same. With cutting the Bilstein bump stop to 3 cm in the front the ride is not as bouncy as before. I have to wait for the rear.
H&R are said to lower the car more than the Eibachs so this would result in driving on the bump stops anyway. Too low is not too good. Remember how low Honda went in the Type R where they didn't have to compromise in any way as daily driver is concerned. The Type R is not that low.

 

[goldNSX]

Does it mean that your car only has 1.7 to 1.8 cm (.75 in) spring travel? Is this for the front?

If that is the case, I suspect that with other lower springs such as Eibach (1.25 in. drop) would be riding on the bump stopper...???

Yes, in the front, it's 1.7-1.8 cm COMPRESSION suspension travel UNTIL the bump stop takes action. The REBOUND suspension travel is about 4 cm. As the thing is soft it acts like a very progressive spring and transmits a lot of force to the chassis directly than the suspension alone. This is what resulted in the bounciness in my car before cutting them.

Same as above: Eibach with Bilstein/high perch is about Zanardi springs with Bilstein/low perch as far as ride height is concerned. The distance from the fender to the center of the wheel is 32.5 cm in the front.

 

[nis350]

Yes, in the front, it's 1.7-1.8 cm COMPRESSION suspension travel UNTIL the bump stop takes action. The REBOUND suspension travel is about 4 cm. As the thing is soft it acts like a very progressive spring and transmits a lot of force to the chassis directly than the suspension alone. This is what resulted in the bounciness in my car before cutting them.

Same as above: Eibach with Bilstein/high perch is about Zanardi springs with Bilstein/low perch as far as ride height is concerned. The distance from the fender to the center of the wheel is 32.5 cm in the front.

With so little spring travel in the front, that would mean that it would be sitting on the stopper on the leaning side on a turn. What negative impact would that have on the handling of the car?

 

[goldNSX]

With so little spring travel in the front, that would mean that it would be sitting on the stopper on the leaning side on a turn. What negative impact would that have on the handling of the car?

I have the Type R front and Type S rear swaybar installed. My car can't move very much over all and I believe with 1.7-1.8 cm suspension compression till the bump stop she doesn't drive on them around even hard corners, except hard road irregularities. 1.7-1.8 cm are about 2.0 cm of wheel travel as the shock is mounted inside (don't know the exact word for it). As the stop bump is flexible I think the compression travel in the front is about 3.5-4.0 cm max. That's quite a lot. BTW a stock NSX has a compression suspension travel of about 4-5 cm in the front. So the lowering takes quite a big amount of susp. travel away. I'm no racing man but someone told me that for a racing car it's favoured be IN the stop bumps through turns as they pressure the car on the road. My concern are road irregularities and the much less forgiving handling in this extrem state. The characteristic of the stop bump is the one of a (very much) progressive spring, like 0 or 1. And this can be very dangerous IMO as you get used to 0 but the car changes it's characteristics in maybe unexpected situations.

Ok, all theoretical and hypothetic but worth of discussing. Maybe a racing guy can give us some input.