Z4M: How soon should struts wear out?

RADRACR · 12-06-2016, 09:38 AM

- 64K miles.
- H&R lowering springs (actual drop about .75") at 20K.
- It's been driven on some really shit roads for extended periods of time.

I'm noticing significant body roll and general disconnect with the road at highway speed. Makes turns like ramps kind of scary. Not noticeable at low speed.

I told my trusted indie to go over the suspension in detail. He even test drove it and found nothing. I trust him because it would have given him an opportunity to sell me something even if it were halfway worn out. In fact he spotted worn FCABS on my X5.

But I bought the car brand new and I can tell something is up. What could it be?

The HACK · 12-06-2016, 11:33 AM

Factory struts have a half-life of about 30,000 miles. Meaning their effective damping rate HALVES as measured on a shock dyno every 30,000 miles. So by 6x,xxx miles your dampers are only about 1/4 as effective as when they're new. Combined with lowering springs they likely would have been even shorter.

RADRACR · 12-06-2016, 11:38 AM

Good to know. What about aftermarket adjustable coilovers like KW Clubsport?

The HACK · 12-07-2016, 12:07 AM

I've only seen Dyno data for factory dampers. However, I did remove my Koni yellows to be revalved at 46,xxx miles, about 30,000 miles after they were installed, and the pro shop ran it on their shock dyno and said there's nothing wrong with them and they were well within their tolerances.

Can't speak to KWs but I would have to assume they're of equal if not better quality and construction as the Koni's.

12-06-2016, 09:38 AM	#1
RADRACR Captain 84 Rep 924 Posts Drives: '08 Z4 M Coupé // '09 X5 d Join Date: Apr 2010 Location: Sioux Falls, South Dakota iTrader: (2)	Z4M: How soon should struts wear out? - 64K miles. - H&R lowering springs (actual drop about .75") at 20K. - It's been driven on some really shit roads for extended periods of time. I'm noticing significant body roll and general disconnect with the road at highway speed. Makes turns like ramps kind of scary. Not noticeable at low speed. I told my trusted indie to go over the suspension in detail. He even test drove it and found nothing. I trust him because it would have given him an opportunity to sell me something even if it were halfway worn out. In fact he spotted worn FCABS on my X5. But I bought the car brand new and I can tell something is up. What could it be? __________________ '08 Z4 ///M Coupé (#1765/1815) — 1 of 68 Sepang Bronze / Black Nappa / Madeira Wood / 1 of 1 this combo 19" Advan RS / AP Racing / Bridgestone RE-11 / Autosolutions SSK / R.E. Diablo / R.E. trans mounts '09 X5 35d — Space Grey / Saddle Brown 20" Forgestar F14 / SCR Delete
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12-06-2016, 11:33 AM	#2
The HACK Midlife Crises Racing Silent but Deadly Class 1821 Rep 5,337 Posts Drives: 2006 MZ4C, 2021 Tesla Model 3 Join Date: Oct 2007 Location: Welcome to Jamaica have a nice day iTrader: (1)	Factory struts have a half-life of about 30,000 miles. Meaning their effective damping rate HALVES as measured on a shock dyno every 30,000 miles. So by 6x,xxx miles your dampers are only about 1/4 as effective as when they're new. Combined with lowering springs they likely would have been even shorter. __________________ Sitting on a beat-up office chair in front of a 5 year old computer in a basement floor, sipping on stale coffee watching a bunch of meaningless numbers scrolling aimlessly on a dimly lit 19” monitor.
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12-06-2016, 11:38 AM	#3
RADRACR Captain 84 Rep 924 Posts Drives: '08 Z4 M Coupé // '09 X5 d Join Date: Apr 2010 Location: Sioux Falls, South Dakota iTrader: (2)	Good to know. What about aftermarket adjustable coilovers like KW Clubsport? __________________ '08 Z4 ///M Coupé (#1765/1815) — 1 of 68 Sepang Bronze / Black Nappa / Madeira Wood / 1 of 1 this combo 19" Advan RS / AP Racing / Bridgestone RE-11 / Autosolutions SSK / R.E. Diablo / R.E. trans mounts '09 X5 35d — Space Grey / Saddle Brown 20" Forgestar F14 / SCR Delete
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12-07-2016, 12:07 AM	#4
The HACK Midlife Crises Racing Silent but Deadly Class 1821 Rep 5,337 Posts Drives: 2006 MZ4C, 2021 Tesla Model 3 Join Date: Oct 2007 Location: Welcome to Jamaica have a nice day iTrader: (1)	I've only seen Dyno data for factory dampers. However, I did remove my Koni yellows to be revalved at 46,xxx miles, about 30,000 miles after they were installed, and the pro shop ran it on their shock dyno and said there's nothing wrong with them and they were well within their tolerances. Can't speak to KWs but I would have to assume they're of equal if not better quality and construction as the Koni's. __________________ Sitting on a beat-up office chair in front of a 5 year old computer in a basement floor, sipping on stale coffee watching a bunch of meaningless numbers scrolling aimlessly on a dimly lit 19” monitor.
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