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Old 12-19-2010, 10:11 AM   #1
Messe46
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Join Date: Nov 2007
Location: New York/Burlington
Posts: 674
My Ride: 325xi ZSP - ONRLS
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Sport vs HD direct from bilstein (2)

I posted this up a few weeks ago in the Xi forum and figured it would also apply to non-Xi's as well. Here you go:


Quote:
Originally Posted by Messe46 View Post
Hey Guys,
So it's time for my rear shocks to be replaced and I was searching around for info between the 2 shocks list above (Sport and HD, for those who can't/don't read everything ). All the stuff I came across in the "xi section" did not help answer my question: "what's the real difference(s) between the 2?"
That's when I finally called up Bilstein directly, down in Mooresville, NC. The woman I spoke to sounded very knowledgeable, confident, and timely in her responses (did not have to put me hold on, etc. after I asked my questions).

Here's what I came up with:
The Sports and HDs have the exact same internals (same valving, compression ratios, rebound, etc.). The difference in the 2 is the height of the outer tube, which is to accommodate different spring heights. She assured me that the 2 shocks will have similar ride qualities, but the sport will be slightly stiffer. This is not because of internals, but rather the shorter tube length makes for the ride to be slightly stiffer since there is less room form the fluid to move (there's probably more head-loss and other factors from having more area to move (I'll let you know when I take compressible flow next semester )).
As for ride height (important for me and others in areas with snow (Vermont for me)), the car will have the same height whether you have the Sports or HDs (ride height will depend on the springs you use).
**Read this if you read nothing else** She also told me that if you have any lowering springs (H&R, Eibach, etc) with the HD shocks and the shocks blow-out, YOUR WARRANTY IS VOID!!! I don't know about you, but that helped me make up my mind on which ones to get.

Summary:
-Same performance
-Same internals (valving, etc)
-Different length tubes (shorter tube makes slightly stiffer ride, but both rides will be similar)
-WARRANTY BECOMES VOID for HDs with lowering springs (if/when they blow)

I hope that helps anyone else out if they were in the same boat as me.



Disclaimer: this is based on information provided by Bilstein in Mooresville, NC. This is not my opinion or fact, nor am I stating it is. Other factors, such as tires, rim size/weight, and other modifications done to your car might have varied results.
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