Front subframe bolts - reusable?

[billybob]

So next job is to replace my rear lower control arms. I did the rest of them last year.

From what I understand you need to lower the subframe a little (on one side at least) to get the control arm bolt out. I've seen mention of either one (rear) or all of the subframe bolts being one-use only (TTY). Can anyone advise if this is the case.

If they are one use only does anyone know the part number as I'm not able to spot these bolts on the various online catalogues

Or if it is possible to re-use them once or twice can anyone advise as to torque settings for a re-used bolt?


Many thanks

[Roverfan]

Not familiar with the a4 but TTY bolts are those which have a torque setting followed by an angle to further tighten. The initial torque is their max and thereafter they deform to provide the maximum clamping force. Using this manufacturers can use lighter and smaller diameter bolts to apply larger clamping force. I have seen the comment that they are OK to reuse once however that's not actually true imo. It really depends on the deformation suffered by each bolt each time it is torqued. They become unreliable after first use because each bolts precise deformation is unknown. Most will reclamp seemingly satisfactorily but some wont or may need a retorque down the line, may need keeping an eye on etc hence unreliable.

There is cases of engines falling down months after a repair where the mounting bolts were not changed also subframe knocking noises due to reused bolts becoming loose are very common

[Crasher]

The required information is available from erWin

[billybob]

I can't really justify paying just to find out that one bit of info but next time I have a larger job that I can't find resources for I may check this service out

Thanks

[William G]

Apologies for possibly hijacking this thread with a different subframe related Q. I replaced mine just over a year ago with used unit from a local breakers. It was in excellent condition as had been completely coated in oily muck which once removed revealed original paint with only a couple of minor areas of corrosion, so I had no concerns about the structural integrity of what was going in. Problem is ever since, the car has had a clunk under certain combinations of braking/steering input. Everything has been checked and torqued by my local (and very competent) garage and we've drawn a blank. No clunk before, so it's something to do with the subframe change. I've read it could possibly be weakened pinch welds in the subframe, which is surprising given the apparent condition of the replacement. Anyone have any other suggestions please!