Shock Replacement???

[kjack]

I used bilsteins to replace the OEMs on a 5-series with sport suspension once and I noticed the car didn't sit as low as it did before the change. It sat as if it had the non-sport suspension. I was told it was due to the stiffness of the bilsteins. Do you think the height of the X5 will be affected by the stiffness of the Bilsteins vs the OEMs?

[FSETH]

Originally Posted by kjack

I used bilsteins to replace the OEMs on a 5-series with sport suspension once and I noticed the car didn't sit as low as it did before the change. It sat as if it had the non-sport suspension. I was told it was due to the stiffness of the bilsteins. Do you think the height of the X5 will be affected by the stiffness of the Bilsteins vs the OEMs?

I am not a mechanic, but that just doesn't make sense to me. The spring is what actually lifts the car up. The shock just keeps the car from bouncing on the spring, so I am not sure that whoever told you that was correct. That is why you can buy lowering springs and not lowering shocks.

I don't see how putting Bilsteins on the X5 would change ride height at all.

vinuneuro, do you think the Bilsteins differ from OEM Sachs enough to be adversly affect the handling characteristics of a BMW with the standard sport suspension? I am not sure if it would be noticeable. If so, what do you think would be affected the ride (comfort) or handling?

[vinuneuro]

Originally Posted by FSETH

vinuneuro, do you think the Bilsteins differ from OEM Sachs enough to be adversly affect the handling characteristics of a BMW with the standard sport suspension? I am not sure if it would be noticeable. If so, what do you think would be affected the ride (comfort) or handling?

I've seen many shock dyno's at not once has has aftermarket damper's valving matched the oem. There's no reason to go with any aftermarket damper with a Bimmer, since BMW developed the oem shocks, and Sach's (ZF Sachs) manufacture's them.

If you're really obsessed with Bilstein you can buy one new front and rear oem damper, dyno them, and then have Bilstein revalve the bilstein shocks to oem specs.

[FSETH]

Originally Posted by vinuneuro

I've seen many shock dyno's at not once has has aftermarket damper's valving matched the oem. There's no reason to go with any aftermarket damper in this situation since BMW developed the oem shocks, and Sach's (ZF Sach's) manufacture's them.

If you're really obsessed with Bilstein you can buy one new front and rear oem damper, have it dyno'd, and then have Bilstein revalve the bilstein shocks to oem specs.

Just curious, but could the fact that the car appears to sit higher with new shocks have anyhting to do with the fact that most people who change their shocks have significant mileage on the springs? In other words, could the springs be sagging a little by typical shock replacement milage, 60-150K? That would make the car appear a little lower and then when you slap some stiffer Bilsteins on there it raises up? Could that also be part of the issue?

Sorry kjack, I would have never in a million years guessed that shocks could make a car ride higher. I know the Bilsteins are stiff, but figured the weight of the car would have been to much to make a difference.

[vinuneuro]

Originally Posted by FSETH

Just curious, but could the fact that the car appears to sit higher with new shocks have anyhting to do with the fact that most people who change their shocks have significant mileage on the springs? In other words, could the springs be sagging a little by typical shock replacement milage, 60-150K? That would make the car appear a little lower and then when you slap some stiffer Bilsteins on there it raises up? Could that also be part of the issue?

Sorry kjack, I would have never in a million years guessed that shocks could make a car ride higher. I know the Bilsteins are stiff, but figured the weight of the car would have been to much to make a difference.

Bilstein monotube's are notorious for a slight ride height increase. The spring is not a consumable, but you do have a point. I'm sure a worn shock would allow the car to sit lower. That coupled with a Bilstein replacement is probably the difference he saw. Monotube's in general are high-pressure shocks, but that pressure affects the shocks stiffness/softness little. It's the rate at which the oil passes through the shims and piston that affect the ride/handling.

All this being said, on basically any vehicle other than a BMW, I'd go with a Bilstein damper for a replacement (I think Euro Porsche's and VW's come with Bilstein from the factory, for NA they use super-crappy Monroe shocks).


If you'd like to learn about dampers, read through the Penske manual. Some of it just regarding their shocks but they also discuss damper tuning. Quickly before you look at it: bump is the compression stroke, rebound is the opposite. For basic purposes, bump controls the unsprung mass (suspension components), rebound controls the sprung mass (body). Low-speed (shock piston movement) movements are things like rolling in a turn, mid-speed is situations like more gradual undulations, high-speed is curbs, potholes, etc. Notice that on any shock dyno graph, the force produced by a shock is a function of (piston) velocity.

http://www.penskeshocks.co.uk/downlo...TechManual.pdf

From the Bilstein site, this is basically what the inside of a monotube damper looks like:

[vinuneuro]

Originally Posted by kjack

I used bilsteins to replace the OEMs on a 5-series with sport suspension once and I noticed the car didn't sit as low as it did before the change. It sat as if it had the non-sport suspension. I was told it was due to the stiffness of the bilsteins. Do you think the height of the X5 will be affected by the stiffness of the Bilsteins vs the OEMs?

Actually, that's really common with Bilstein monotube's because the high-pressure within the shock doesn't compress as much when loaded.