I picked up a 15 year old BMW 128i in July. The suspension has all the creaks and groans. I replaced a couple arms in front that had worn out bushings but the rest of the arms seem good. I plan to replace the shocks and bump stops and all the associated hardware. 97k miles. I'm not after lowering, just a refresh would be great. I'm trying to understand if the original springs need to be replaced.
How can you tell?
Without measuring spring rate, height with no load vs a brand new, or any number of other tests that would require disassembly... no clue.
You'd have to take them off the car, i believe.
Depends on length and metallurgy...some sag after 5-10 years, some last approximately forever. If the ride height hasn't decreased from stock then they haven't sagged.
Usually about 3 months a year.
Appleseed said:Usually about 3 months a year.
Ba dum tisssss
GameboyRMH said:Depends on length and metallurgy...some sag after 5-10 years, some last approximately forever. If the ride height hasn't decreased from stock then they haven't sagged.
This is logical but I just bought the car and there are no "same but new" examples to compare.
New springs in a kit are not a huge cost but in principle I'd like to avoid replacing parts that are still good.
I had a spring shatter on my E36 last year. It wasn't original but at least 15 years old. The only spring I"ve ever had go bad including on my well abused racecar that's much older.
OHSCrifle said:GameboyRMH said:Depends on length and metallurgy...some sag after 5-10 years, some last approximately forever. If the ride height hasn't decreased from stock then they haven't sagged.
This is logical but I just bought the car and there are no "same but new" examples to compare.
New springs in a kit are not a huge cost but in principle I'd like to avoid replacing parts that are still good.
As a reference, in the early-mid 2010s, I changed the springs on my '93 F150, 225k on the clock. Did not notice a difference.
If I remember my classes correctly, springs don't wear when they are compressed or they are completely unloaded, they wear as they cycle between loading and unloading.
15 years old with 97k? I wouldn't worry unless you want a set of spares for whatever reason
Put car on a level surface, measure, and compare as appropriate for your suspension:
https://www.1addicts.com/forums/showpost.php?p=17795834&postcount=2
Results can be validated by checking on multiple different presumed level surfaces.
If notably out of tolerance, remove and replace springs. Otherwise, use as is.
Driven5 said:Put car on a level surface, measure, and compare as appropriate for your suspension:
https://www.1addicts.com/forums/showpost.php?p=17795834&postcount=2
Results can be validated by checking on multiple different presumed level surfaces.
If notably out of tolerance, remove and replace springs. Otherwise, use as is.
This ignores bushing sag and shocks which, with the miles and age, is not a good assumption.
Keep in mind that springs lasting approximately forever is the norm, especially on modern cars. Saggy springs are usually seen on older cars that weren't so well-designed or didn't use a great choice of alloy for their springs, or on race cars with tiny short springs that sag more easily.
cyow5 said:Driven5 said:Put car on a level surface, measure, and compare as appropriate for your suspension:
https://www.1addicts.com/forums/showpost.php?p=17795834&postcount=2
Results can be validated by checking on multiple different presumed level surfaces.
If notably out of tolerance, remove and replace springs. Otherwise, use as is.
This ignores bushing sag and shocks which, with the miles and age, is not a good assumption.
OE bushings are set to zero deflection at ride height, and OE (twin tube) shocks have no meaningful spring rate.
IMHO, more likely alternative culprits would probably be the strut mounts in front and the spring isolators in back. Those should automatically be replaced as part of the refresh though.
Driven5 said:cyow5 said:Driven5 said:Put car on a level surface, measure, and compare as appropriate for your suspension:
https://www.1addicts.com/forums/showpost.php?p=17795834&postcount=2
Results can be validated by checking on multiple different presumed level surfaces.
If notably out of tolerance, remove and replace springs. Otherwise, use as is.
This ignores bushing sag and shocks which, with the miles and age, is not a good assumption.
OE bushings are set to zero deflection at ride height, and OE (twin tube) shocks have no meaningful spring rate.
Bushings can sag and/or wallow. Shocks can bind and stick. My point is that your error bars are going to be pretty large. Heck, tire pressure and tread depth would add in. As with the others, I'd just assume the spring does not sag - although I do always replace the springs with the shocks since that's just how I prefer it. The labor is similar, and springs aren't typically expensive, especially compared to the effort and cost of replacing a shock.
In reply to cyow5 :
My point is: If measuring the suspension with the factory service method (no tire effects) and it's within the factory service tolerance band, it's pretty assured that the springs are still good too. If the suspension is only out a little beyond that, it's likely the springs are still good and a refresh should bring it back in. If the suspension is 'notably' out though, it might be a good idea to replace the spring while you're in there if you only want to do it once.
Of course, this discussion all seems to assume good replacement OE springs are actually available too.
On the suspension in question, the only rubber bushing that reacts the static load is the rear lower inboard. It's not a common failure point and would pretty much have to be missing to put the ride height out of tolerance. The rear lower outboard is spherical and the front reacts the static load through the strut mounts.
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