9 replies to this topic

[spiguy]

Hi folks,

 

Whilst replacing my steering rack, I took the opportunity to replace the well squashed rubber subframe tower mounts. I have gone for poly on the bottom, solid metal on the top. When putting it back together, initially I retained the large metal washer under the bolt head. However as I was tightening up it never came to a 'stop' -  I have always found in the past that the bolt tightens until it stops, ie the bolt shoulder is hard against the subframe. I looked at the poly mounts and they seemed very squished.

 

So, I backed the bolts off, removed the washer and did them back up again. This time the bolt tightened down to a stop, the poly bush looked just a bit squashed (I checked and I could not move it so it seems to be 'trapped' OK') and the metal top mount seems secure. I think this is the correct arrangement.

 

Just wondering if others kept or discarded the washer when fitting solid top mounts? And do you agree with me that the bolts shoulder should bear against the subby (and therefore come to a stop) rather than be tightened to a torque value as a measure of the clamping force on the crossmember / mounts?

 

Cheers

Craig

[Steve220]

They should be torqued down. Even polybushes will squash.

[A-Cell]

Front Turret bolt torque setting 67Nm

[spiguy]

OK, so are you guys saying that the bolt shoulder should not meet the subframe tower then?. I always thought it should (though I can't recall where I saw that, it has always been the case on my minis over the years).

 

Of course I can still torque the bolt to a specified value, but in one case (where the shoulder has not come up against the subframe) this torque will represent the clamping force being applied between the underside of the bolt and the threads in the subframe -  and in the other case (where the shoulder has butted up to the subframe) it will only represent force being applied between the shoulder and the threads. In the latter case, the amount of clamping force applied between the bolt / crossmember / mounts / subframe is not indicated by that torque value.

 

Cheers

Craig

[cal844]

Why fit mixed bushes? Go either all solid or all rubber/ poly

Edited by cal844, 10 February 2015 - 05:35 PM.

[A-Cell]

The bolt shoulder length as designed is toleranced for the fitment of the 2 standard rubber mounts. Any deviation from this will result in a different clamp load.

[Cooperman]

Poly mountings are not well regarded.

The best thing is to fit solid steel mountings all round on the front sub-frame.

[Spitz]

I fit poly at the top and solid on the bottom....... I found this was the wrong thing to do after my floor started cracking.

Go all solid.

[spiguy]

I fit poly at the top and solid on the bottom....... I found this was the wrong thing to do after my floor started cracking.

Go all solid.

Agreed, I previously fit solid floor mounts. Never again, cracked my floor. I believe the later shells use a thinner pressing for the toe board and this is why this is a common issue. According to minispares, the solid top and poly bottom *tower* mounts (nothing to do with the floor mounts) is in their opinion the 'best' all round option when replacing tower mounts, which was why I chose this option. I'm not looking to upgrade the handling and I am keeping standard rubber mounts at the floor mounting points.

[spiguy]

The bolt shoulder length as designed is toleranced for the fitment of the 2 standard rubber mounts. Any deviation from this will result in a different clamp load.

That's what I thought - and in the standard setup, you are torquing the bolt shoulder against the subframe. The resulting clamping force I believe, will be whatever it will be with standard rubber mounts in there. So with my choice of mounts I'm trying to best replicate that situation, which as far as I can see is best achieved with the washer removed. Time will tell!