Torque Arm to Final Drive Bolt - This doesn't look right

chris r · Post by **chris r** » Sun Jul 28, 2013 2:38 pm

Just been replacing some nuts & bolts on my R1100s with a box of bits I blagged off ebay. I removed the bolt that secures the paralever arm to the final drive/bevel box, and this is what it looked like

:

Hmm, that's not quite right is it? Needless to say, this has now been replaced, but does anyone know what could have caused it to get so bent out of shape? I'm amazed it hasn't snapped outright.

eyore · Post by **eyore** » Sun Jul 28, 2013 3:00 pm

Crikey.

Lucky you changed it.

Merecat · Post by **Merecat** » Sun Jul 28, 2013 3:18 pm

Looks like its been stretched by overtightening.

chris r · Post by **chris r** » Sun Jul 28, 2013 3:34 pm

That would explain why it's skinny in the middle, I didnt think bolts did that, thought they would have snapped long before getting to that state.

chris r · Post by **chris r** » Sun Jul 28, 2013 4:18 pm

That would explain why it's skinny in the middle, I didnt think bolts did that, thought they would have snapped long before getting to that state.

cornishflat · Post by **cornishflat** » Sun Jul 28, 2013 6:49 pm

How does it compare to the new stock bolt as in total length, shoulder length. The old bolt looks to have a lot of thread and a short shoulder, could explain the deformation.
Mind, lucky your on the ball could have been a nasty experience.

Merecat · Post by **Merecat** » Sun Jul 28, 2013 7:18 pm

chris r wrote:That would explain why it's skinny in the middle, I didnt think bolts did that, thought they would have snapped long before getting to that state.

Under normal conditions a bolt that is correctly torqued can be stretched. Cylinder head bolts are a good example, and when slacked off they will return to their original size, much as an elastic band does.
When over tightened they are taken past their "elastic limit" and will "waist" or "neck" causing the narrowing of the bolt on its smallest diameter.
Seriously compromising the tensile strength of the bolt. The next stage is failure.

Work clothes off..........back to beer

Boxered · Post by **Boxered** » Sun Jul 28, 2013 7:24 pm

That just shows how important it is to use a torque wrench, I always used to just do everything up to FT ( fekkin tight) but I'm better now

Steve

chris r · Post by **chris r** » Sun Jul 28, 2013 7:48 pm

I'm beginning to wonder if this bolt was the correct one to begin with? After looking at the parts list on Motorworks the bolt is meant to have something called a fillister head, after looking at some pics of what those are in comparison to mine, the heads look quite different. The part number is: 33172332610.

The bolt I took off looks to have just a bog standard hex type head. Did the previous owner just whack any old bolt from a box of beemer bits on?

Merecat · Post by **Merecat** » Sun Jul 28, 2013 8:46 pm

Ah. I see

http://www.bmwmcchattanooga.com/showAss ... ct=1038452

My guess would be No 13 and No 17 have been swapped.
Someone may have maxed out on twattage?

Dai wiskers · Post by **Dai wiskers** » Sun Jul 28, 2013 9:12 pm

Fillister head is a bolt or screw with a rounded head above the flats hard to explain without showing one to someone

The bolt in mine looks like your's should very slight fillistering but easily mistaken for a normal bolt

But as other's have said yours is stretched and needs replacing

EDIT have a look at the head of the bolt you will notice that it looks like someone has been at it very gently with a grinder on the edges

chris r · Post by **chris r** » Sun Jul 28, 2013 9:13 pm

Oops, my mistake I wrote the wrong part number down

It's definitely 13

Merecat · Post by **Merecat** » Sun Jul 28, 2013 9:25 pm

chris r wrote:Oops, my mistake I wrote the wrong part number down It's definitely 13

Then the problem was hamfisted oaf with more spanners than sense

Lets see how many threads I can get sticking through this nylock nut!!!

Dog Tyred · Post by **Dog Tyred** » Sun Jul 28, 2013 9:42 pm

chris r wrote:I'm beginning to wonder if this bolt was the correct one to begin with? After looking at the parts list on Motorworks the bolt is meant to have something called a fillister head, after looking at some pics of what those are in comparison to mine, the heads look quite different. The part number is: 33172332610.

The bolt I took off looks to have just a bog standard hex type head. Did the previous owner just whack any old bolt from a box of beemer bits on?

THe bolt you have taken out is correct i.e just an M10 x 55 hex head bolt in grade 8.8 steel. That must have been given some serious torque to do that to it!!

The 'filister' head bolt for which you give the part number, is for the front of the paralever arm where it connects to the frame.

From the link in the post above the apparent BMW part number you need is 07119900139

Alternatively Probolt do a very nice flanged head titanium one for about £13.00 exc postage!!. And don't forget the ti Nylok nut which is a further £6.60

Tightening torque is 43 Nm with an 85 Kg load sitting on the bike when you tighten it!!

DT

PS: just noticed that say it has now been replaced. Dare I ask what with ?? as in material, grade, etc??

Boxered · Post by **Boxered** » Sun Jul 28, 2013 9:47 pm

Dog Tyred wrote: Tightening torque is 43 Nm with an 85 Kg load sitting on the bike when you tighten it!!

DT

Does that mean we need your left leg to be slung over the seat before we torque the bolt up? you could earn a good living there mate

( pot calling kettle etc)

Steve