Check your front suspension arms people

sco said:
Didn't notice any change in road noise when I did mine and I'm usually sensitive to that sort of thing - I'll have another listen tomorrow though. Can't think what would cause it other than the front bush not being in the right place - was the tracking still spot on?

Simon.
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Tracking was slightly out and has been adjusted.
Made no difference to the road noise. The car is still noisy in rough road surfaces but better than it was on motorways and other smooth roads.
In a few weeks I will accept it as normal.
 
Have I just committed the ultimate stretch bolt faux pas?
Been under the car rattle hunting today and while I was there checked the tightness of all the suspension and brake bolts I have replaced recently. All stretch bolts were new and were torqued to spec and then tightened further as specified. All were absolutely solid.
Today without fail every stretch bolt went further and I’ve not been eating Shredded Wheat. Standard bolts were all still solid.
Thoughts?
 
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You mean when you applied the seating torque they turned - shouldn't do unless the joint has colapsed.

Sure you are not mixing lbft with Nm on your torque wrench?
 
sco said:
You mean when you applied the seating torque they turned - shouldn't do unless the joint has colapsed.

Sure you are not mixing lbft with Nm on your torque wrench?
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? absolutely not, I know the difference and they were solid when the extra turn was applied. But what you are saying is a few miles and some hot weather should not enable me to turn these things further. Interesting!
I thought somebody was going to say you will be OK until it gets cold then all your bolt heads will pop off.
 
If you are talking about the bolts that go through the wishbone carrier then they should get tighter with hot weather as the ally casting will expand more than the steel bolt.
 
sco said:
If you are talking about the bolts that go through the wishbone carrier then they should get tighter with hot weather as the ally casting will expand more than the steel bolt.
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Good point, all 4 through the consoles, all 4 to the steering rack, all 4 to the anti roll bushes and both sides of the lower suspension arm to console. All went further without much effort.
 
How are you gauging how tight they are? With the xxNm + 90 degrees etc, isn't it difficult to check if they are still correctly tightened after the event?
 
TFG said:
How are you gauging how tight they are? With the xxNm + 90 degrees etc, isn't it difficult to check if they are still correctly tightened after the event?
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No, xxNm + yy degrees when fitted. The yy degrees was cring worthy and the bolts were solid. I went went back today with the same breaker bar and socket and easily got some more. The bolts are less tight than they were.
 
But that's what I'm getting at - if the bolts were initially tightened correctly and now they are loose, or looser at least than when you fitted them, then how are you supposed to re-tighten them without taking the bolts out of spec?
 
Fasteners using the torque + angle method of tightening are often called stretch bolts and that is literally what happens to them. The bolts are tightened past the yield point of the material and are in the first stage of 'necking' off.
In any bolted joint its the clamping force which is critical and not the torque applied to the fastener. Setting the bolt with a low initial torque value, then stretching it with the angle tightening process gives a more accurate clamping load than torque alone
I have a dial gauge torque wrench and it makes it easy to see how the torque reading maxes out then drops off as the full angle value is reached. The 'drop off' is caused by the bolt being taken past the yield point of the material, that's why you can't re tighten it by repeating the torque + angle process.
Safest way to check 'tightness' would be to use tables to check the standard torque value for the size of fastener.

One example - http://electronicfilters.tpub.com/TM-10-4330-237-13P/css/TM-10-4330-237-13P_105.htm

Cheers Spike
 
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Thanks all for your responses.

TFG I agree and for somebody who has spent years feeling when a bolt is tight these stretch bolts are unsettling to use as you can feel the bolt go past its elastic limit. My question re stretch bolt faux pas related to me possibly having put these bolts outside their spec.

Kleynie, summers day with a cold Northerly vs car been drive on a motor way on a still hot day then being allowed to cool.

SCO I agree and even if (as it should) the bolt has been taken past its elastic limit the amount of force to turn the bolt should be the same even after it has been left for a while. All stretch bolts were considerably easier to turn. I like the linked info thanks

Spike useful chart thank you and yes the drop off that you gauge shows can also be felt. Perhaps to a lesser degree with the larger sizes as my long breaker bar was bending nicely getting the extra yy degrees. Stretch bolts large and small all behaved the same yesterday, the same tools used to assemble the car easily turned a further 45 degrees.

I suspect this will remain a mystery but if anybody else experiences this please post up.
 
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Might it be worth droping a line to somebody in your local Audi service department (or even Audi UK) to see if they can offer any insight? It must be a problem that they come up against time and again.
 
I'd be tempted to check the bolts with a torque wrench using the values in the linked table. I think they will be grade 10.9 but may be worth starting with the value for an 8.8 bolt and working up in increments (assuming you have a 'click' type wrench)
My concern would be the bolts could have been overstretched.

Cheers Spike
 
spike said:
I'd be tempted to check the bolts with a torque wrench using the values in the linked table. I think they will be grade 10.9 but may be worth starting with the value for an 8.8 bolt and working up in increments (assuming you have a 'click' type wrench)
My concern would be the bolts could have been overstretched.

Cheers Spike
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Will do, probably at the weekend.
I have two wrenches in the right range. Will try both just in case one is out of calibration. I will report back.
I can’t use my normal approach to measurement though. Mark bolt position, back off a fraction. Increase wrench tension until bolt back in original position.
If I back a stretch bolt off it’s it does not contract to it’s original length so the above method does not work. Also in theory it should be replaced. All I can do to measure the torque is increase the wrench tension until movement is threatened.
Yesterday I thought I saw two different torques specified in my manual for console bolts. Will check again today and update.
Edit: the manual is consistent throughout, 70Nm + 90 degrees.
 
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Apologies for always going back to basics but hopefully it makes the discussion more informative for members who don't have an engineering background.

Cheers Spike
 
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