Durability of aftermarket motor mounts

[M-tinker]

Last week I found both of the motor mounts were broken. One had a broken stud, on the other the stud had come loose from the inside and grounded the thread around it. Luckily I discovered the problem before the time trial weekend and was able to put back the old mounts.

Has anyone experienced similar problem with aftermarket mounts, esp for cars that see mostly track duty? Mine are Vorshlag 70A Poly mounts. I'm thinking of using 740i motor mounts in hope of getting factory part durability.

-Fred

[Bruce]

I would say they were overtorqued.

[blyguy]

I have had a so-so experience with my Vorshlag motor mounts.I have the white nylon mounts installed 2 1/2 years ago. They have not failed but the top of the passenger side mount has moved and the nylon portion is bowing out. I've been on the track twice with them and the rest has been daily driving.

There is more vibration than stock and they firm up the driveline, so that is a plus. I don't think they're more durable than stock, and I don't know about 740i mounts. I will probably try the 740i next.

I agree with Bruce, that your mounts look overtorqued in order for them to fail like that. The thread on the top pic looks sheared off.

-Bryant

[M-tinker]

Here is the thing I noticed during installation. When I tried to torque the top nut to 30 ftlb as recommended by Koala CD, the bushing would be squeezed really fat and it sit shorter than the stock mount. I didn't want to overstress the bushing, so I backed off the nut until the height was somewhat close to the stock mount height. But then the torque on the nut was not 30 ftlb (more like 20ftlb). Could the problem be caused by under-torquing the nuts?

[blyguy]

You know, I was thinking undertorquing could cause the rod to shear like that as well due to vibration. Vorshlag says that their motor mounts are designed to have the same height as a compressed stock mount, and maybe the Vorshlag mounts should be compressed the same way? If you search for it, there's a thread from the Vorshlag guy where he describes the way the mounts are installed.

-Bryant

[UweM3]

with any "bolt-through" type of engine mount there is no give. The bolt will see all the load and the more the mount material is able to compress, the bigger the stress on the bolt is.
I was running a mount made from ice hockey pucks for quite a while but whilst one side was perfectly ok, the other side bolt was deformed at the top right where it sticks out of the mount.
If you fit sticky tyres, it will get worse.
If I will run this setup again, I will use M12 bolts, not M10.

[1st Roundel]

Be careful with factory torques specs on non factory parts. I'd think 30 ft lbs would be OK, but maybe not what Vorshlag recommends. IIRC, when I bought my identical mounts, the recommendation was to just bring one line of thread past the nylon lock. By compressing the mounts more, you'll get more deflection and more rigidity I believe.

[99M3Riverside]

I thought with the vorshlag mounts you torque them until it starts to compress. I don't think you torque to a certain ft/lb rating.

[Az in Oz]

^...a bit from one up
^^ and a bit from two up.

I've been running mine for over a year now and I tightened them as above, just till they compressed on the rubber.
One thing I did find however was that they have needed a full turn retighten since then. I noticed everything getting a little "vibratee" and after the tighten is was ok.

Aaron

[Ironhead]

In all the time I have been following this stuff, I have heard of so much bad experience with aftermarket engine mounts....I cannot even recount it all.

The factory Group N mounts are the ideal answer, but they are big bucks unfortunately. If I could not afford them, I think I might just stick with stock.....

[M-tinker]

Yeah I stopped tightening the nuts until the bushing was slightly compressed. When I examined the broken parts, the top nuts were still in place, no sign of backing off. Just the studs came off from the inside. I see the mount was held by two studs threaded through a common aluminum housing. On compression, I can see the bushing doing its job of dampening the force. But when the mount is lifted, only the stud and the alum housing is holding the mount together. Probably the constant pulling and pushing action on the mount is stressing out the stud.

Anyway, I hope this is just a freak incident or an installation error on my part. But don't forget to check your engine mounts every now and then. It's no fun to see your engine bouncing around on the track

-Fred

[MMMM]

I have used stock mounts until I installed the new S14 2,5l + Alpha-N + CF airbox. I tried AGK but both broke within 2.000Km of use (street + track). Since I have opted for Gr.N mounts both for the engine + transmission which have worked well so no more experiments ...

[Jake]

+1 for the Grp N motor mounts.

Jake

[Walter Boggs]

motor mounts

Hey guys,
Just out of curiosity, how much are Group N motor mounts any way? Are they available from the dealer? Thanks.
/WB

[UweM3]

Hey guys,
Just out of curiosity, how much are Group N motor mounts any way? Are they available from the dealer? Thanks.
/WB

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