M20 New valve oem springs too short????

[zaq123]

M20b25

ordered new oem valve springs pn# 11341706583. Same markings as my old ones: orange and green line across 4 coils. You'd think that old spring would sag after 170k and 26 years.....but here is what I got:

old OEM springs:

free length: 45.50 mm
coil wire diameter: 3.95mm
spring diameter: 30.15mm

new OEM springs:

free length: 45.15mm
wire diameter: 3.95mm
spring inner diameter: 22.25mm
spring outer diameter: 30.15mm


Considering springs sag overtime, how can old OEM springs are longer than new OEM ones?

Any ideas?

[dnguyen1963]

I don't know the spec for the springs, but I know that as the spring ages the metal relaxes and the spring can increase its length.

[zaq123]

I don't know the spec for the springs, but I know that as the spring ages the metal relaxes and the spring can increase its length.

I think springs are generally sag.....never heard of them grow...hmm

[digger]

i dont see any big issues its 0.35 mm difference isnt it? if you have one of those spring testers just check them out

[dnguyen1963]

I think springs are generally sag.....never heard of them grow...hmm

The valve springs are very tough. They will not sag. Go to the junk yard sometimes and take out some old suspension springs. They are likely to be a bit higher than a new one.

[TobyB]

never heard of them grow

They ordered one of those thingys from the back of C&D that give you extra length.... in only 7 days.

Never heard of them growing, either. HAVE seen them grow shorter, tilt sideways, break...
...but seldom. I agree, BMW's valve springs, especially in the M10- M20 era are very durable.

Like Digger says, what matters are seat and nose pressures- and BMW may have
figured out a way (different alloy? heat treat? freud am farhen?) to get the right pressures
that led to a different relaxed height.

Personally, if it revs over 5500, I check the seat and nose pressures with the $65
spring pressure tester. But I got bitten once by 'racing' springs from a reputable
vendor that were 'exactly stock' rate and pressures... and low height, to boot.

Crap springs CAN sag. Good ones don't, and tell you how much they can change.

t

[zaq123]

i dont see any big issues its 0.35 mm difference isnt it? if you have one of those spring testers just check them out

Schrick lists 0.25, 0.30, 0.50mm etc spring washers in their catalog....not an expert but I though .35mm could be a big deal???

[digger]

Schrick lists 0.25, 0.30, 0.50mm etc spring washers in their catalog....not an expert but I though .35mm could be a big deal???

0.35mm is 4lb difference in preload. you can shim it back up if when you check the load its off where you need to be. you wouldnt want seat load to be lower than stock