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E46 Xi Forum
The E46 XI was produced from 01-05 in sedan and touring body styles. Powered by either a 2.5L inline 6 in the 325xi or a 3.0L inline 6 330xi. Discuss all thing about BMW AWD E46 'Xi' here.

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Old 12-08-2010, 03:44 PM   #1
Messe46
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Arrow Bilstein Sport vs. HD (Direct from Bilstein)

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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Old 12-08-2010, 03:49 PM   #2
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Originally Posted by Messe46 View Post
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 )).
The fact that there is less room to move the fluid doesn't matter. The fluid is incompressible no matter if you have an ounce or a gallon. It's all about the orifice (valve) that the fluid travels through. The shorter body just means there's less travel distance.

Good research though!
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Old 12-08-2010, 04:47 PM   #3
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OP so what shocks do you think you'd get? i wanted a bilstein sport/HR sport combo but now with that warranty thing idk what to do
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Old 12-08-2010, 04:52 PM   #4
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Old 12-08-2010, 10:00 PM   #5
Kubica
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I had a nice chat with a Bilstein rep at the Bavauto show'nshine this year- he specifically mentioned three separate times that the HD's for the xi are good for up to a .75inch drop.

I don't know of springs that give that small of a drop, but that's where the cutoff line is.
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Old 12-09-2010, 06:49 AM   #6
lotar_6
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Originally Posted by Glissco27 View Post
OP so what shocks do you think you'd get? i wanted a bilstein sport/HR sport combo but now with that warranty thing idk what to do
He stated the warranty would be void for HD's on lowering springs... not sports on lowering springs.
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Old 12-09-2010, 09:48 AM   #7
SamDoe1
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I don't know if this is stated or clear on this one, but the shocks/struts do not contribute very much to at all in lowering a car. They are simply the damper in a mass(car)-spring(obvious)-damper(shock/strut) system. The springs are the only thing which will lower your ride height. The dampers only reduce the oscillation (bounciness) of the spring. The reason you can't use the longer shocks on short springs is because they will always ride in a low position which will eventually blow the valves because they aren't designed to operate for extended periods of time at such pressure.
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