Shock Replacement???

[kjack]

Good day to all the knowledgeable folks on X5world. I have an 01 X5 4.4 with 83k miles and was wondering is there a certain mileage when you should replace your shocks and struts. My ride seems not to be as stable as it once was and i have already replaced tension struts,control arms,inner & outer tierods as well as the lower ball joints. I figure the only things left are the shocks and struts. What do you guys as well as gals(don't wanna be considered to be a sexist)think? Also what is your opinion on bilstein shocks for the rear and OEM on the front?

[vinuneuro]

Worn shocks would definintely add instability. On most vehicles, shocks start becoming tired after 60k miles. On our E53, I noticed it at around 70k miles.

Mixing oem and aftermarket shocks is about the worst thing you could do for performance. BMW has among the best chassis engineers in the world, and suspension on all their vehicles is developed very acutely. Go with OEM all around.

[kjack]

Thanks for your advice. I think I'll definitely replace with OEM all around. Could you suggest a site where I can buy the shocks at a reasonable price?

[vinuneuro]

Originally Posted by kjack

Thanks for your advice. I think I'll definitely replace with OEM all around. Could you suggest a site where I can buy the shocks at a reasonable price?

Morristown BMW consistently has among the lowest prices available. Email them for a quote: [email protected] .

[FSETH]

Originally Posted by vinuneuro

Worn shocks would definintely add instability. On most vehicles, shocks start becoming tired after 60k miles. On our E53, I noticed it at around 70k miles.

Mixing oem and aftermarket shocks is about the worst thing you could do for performance. BMW has among the best chassis engineers in the world, and suspension on all their vehicles is developed very acutely. Go with OEM all around.

I agree with never mixing shocks. Whatever you go with, be sure to use the same shocks all around. It just isn't safe to do otherwise.

Just curious why you wouldn't consider Bilsteins vinuneuro? They are designed to last a little longer than average and give a slightly firmer ride. What's wrong with that? I have had them on my 325i for over 100k and they still work great.

My personal opinion would be to go for the Bilsteins.

[vinuneuro]

Originally Posted by FSETH

I agree with never mixing shocks. Whatever you go with, be sure to use the same shocks all around. It just isn't safe to do otherwise.

Just curious why you wouldn't consider Bilsteins vinuneuro? They are designed to last a little longer than average and give a slightly firmer ride. What's wrong with that? I have had them on my 325i for over 100k and they still work great.

My personal opinion would be to go for the Bilsteins.

I think Bilsteins are great; in fact we've got Bilsteins in the 4runner. The oem shocks are made by Sachs, which aren't bad quality by any measure. The reason I won't change from OEM on a BMW is that the shock valving is never the same when you go to an aftermarket damper regardless of the vehicle. It'd be fine for most vehicles out there.

That's not a bad thing, but why go to different valving when the some of the best chassis/suspension/shock engineers in the world came up with the valving curve for the OEM shocks? Most people don't realize it, but the shocks determine 90% of the handling characteristics of a vehicle once suspension geometry is fixed. There's a LOT that goes into developing the right curve. I can guarantee you Bilstein engineers wouldn't have put in even 10% of the time that BMW engineers put into the oem dampers.

A firm ride doesn't equal better handling. All a firm ride means is more high-speed damping. Ever wonder how BMW's have that perfect balance between ride stiffness and handling? That's all in the shock absorber. There's a question of whether to use digressive or linear valving for the entire curve. If digressive, do you want the low-speed section to be digressive, linear or progressive. Where do you want the knee of the curve. At what rate do you want it to digress. Etc etc etc. Then using the sway-bar size as a tuning tool beyond the shock absorber. There's a lot to account for mathematically with the chassis frequency, spring rate, tire rate, etc. Then you have to do a lot of testing after you've got a decent baseline. There's quite a bit to it, and the aftermarket company- even if it's Bilstein isn't going to invest as much in it as the company that prides itself on vehicle dynamics- the one that designed the vehicle in the first place.

Imo, Bilstein probably makes the best quality shocks handsdown. They're oem shock suppliers to the VW group, also have a ton of motorsport experience in F1 and a ton of Porsche LMP, Grand Am, etc cars use them. BUT they did not develop the oem BMW shocks.

[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 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.

[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.