Wishbone bolts

[barryw]

Hi,
I changed one of the wishbone bushes on my Audi 80 at the weekend and noticed that on both bushes, there was some slack around the bolts. The diameter of the unthreaded section of both bolts is 8.9mm. Can anybody tell me if this is correct, or should I get some new bolts?
Thanks.

[scotty33]

Hi

I wouldn't worry too much about the bolt shank being undersize, the thread is probably formed on a thread rolling machine which 'throws up' the threaded part to the correct size. This 'forged' thread will be stronger than a die cut thread, but the shank size needs to be a little undersize as you have found.
I have read that these bolts are angle tightened and therefore are stretch bolts, in which case they should not be reused. My Haynes manual quotes a torque figure only, which suggests they are not stretch bolts. To be honest it's hard enough getting spanners on them let alone anything else!
I would warn that you should tighten these bolts with the weight of the car on the wheels, if you tighten them with the wheels off the ground, the bushes are under stress as soon as you lower the car down, they don't last very long like this.

[Col]

I am of a different opinion on this one.

A true stretch bolt will have a reduced section diameter for part of it's length usually just under the head.

I think the advice for the renewal of the wishbone bolts is due to the fact that when re-used the green self locking compound that is applied to vag group bolts is no longer effective.

Now, a drop or two of locktite on the threads should remedy this but it is my belief (from experience) that any residual factory goo and locktite do not mix and that the locktite doesn't seem to work. I did notice a long time ago with locktite'd bolts I had to re-remove to do some other work.

Now I renew any safety critical bolts as a matter of course.

In fact once in my local VW dealers (back in my MK4 Golf days), I got into an arguement with the parts guy and their head technician who happened to be present. I was told, when ordering new engine mounting bolts that I was trying to buy prior to me doing a cam belt change that "We never renew them". Funny that, as VW's own literature clearly states that these bolts should be renewed. And what isn't funny are the number of reports you read of MK4 Golf engine mounting bolts working loose and wrecking the engine.

Suspension bolts therefore are a must !

[barryw]

Cheers for the tips. I think I might get some new bolts, just in case! Didn't know about the tightening with the weight on the wheels either, thanks!