Torque Settings truths...

[Royalratch]

Whilst scouring the web and various printed manuals (Bentley / Haynes etc) for rear differential torque settings, I have come across wildly differing values - some upto 25Nm in difference.

Is there a sort of equation or rule for just calculating this shit?

Using the bolt / nut diameter and thread spacing and if its a heavy load bearing part then you can calculate the correct torque?

[Brianmoooore]

http://www.bmw-m.net/TechData/torq/bmw_torq.pdf

[capnmchl]

The torque that can be applied is result of the tensile strength of the bolt (the little number on top of the bolt, like 8.8 or 10.9), the thread pitch and bolt diameter.

There are many charts littered across the internet that will tell you the torque of any bolt you should need to do up. The only problem is when you find very specific thread pitches.

[Brianmoooore]

Most of the common sizes and grades are actually printed on a little chart on one of my torque wrenches.

[ross_jsy]

Haynes manuals are full of shit. Sheared 3 head bolts on a 2 stroke I was rebuilding going by the torque settings in a Haynes manual before realising my error. Apparently it's quite common.

In fact I seem to remember you sheared the subframe mounting bolts going by their stated torque level?

[Royalratch]

No - that was from advice in here lol. Serves me right - should my own checks.

[Royalratch]

Dudes - I've been getting in new fasteners from BMW for this but its getting stupid expensive.

They wanted £20 for 4 nuts and bolts for the prop to diff connection. Are they special?

Would any hi-tensile M-8 stuff do?

[capnmchl]

I think the nuts are ovaled, which makes them locking nuts. In theory you can use what you want, but there may be some design in the shank or an odd thread pitch.

[Royalratch]

Look pretty regular to me.

Its a wider question for all hardware as we work on these cars dealing with rotten and crusty bolts - ordering new stuff from BMW, unless very specific and unique, is a pain and rip off.

[daimlerman]

Prop to diff is a special bolt with a splined head that is held in the diff flange IIRC.
Nut needs to be at least a nyloc type in the correct size.

In general,most nuts/bolts are standard metric sizes and can be sourced from any nut and bolt supplier,I keep a small stock of stainless steel fasteners and routinely replace any worn/rusty fasteners as I work on my cars.

Some bolts,however,do have odd thread pitches that are BMW only,two that come to mind immediately are diff top mounting bolts and caliper mounting bolts,these use a finer pitch thread than that which is regularly available.Obtaining,and using :Da thread pitch measuring gauge is the way to find these blighters.

[Royalratch]

I have a pitch gauge.

i was more talking about strength? A lot of online sellers just quote material or Stainless etc but not tensile strength...

[capnmchl]

I buy all my bolts from this seller on ebay. Seems to have most things, cheap, and it usually turns up within 2 days even being second class.

http://myworld.ebay.co.uk/benb4ll?_trks ... 7675.l2559

[G-Bear]

I buy all my bolts from this seller on ebay. Seems to have most things, cheap, and it usually turns up within 2 days even being second class.

http://myworld.ebay.co.uk/benb4ll?_trks ... 7675.l2559

Just dug this thread out, looking for tightening torques for my steering rack.. Good ebay find here.. shall try him out soon..

[G-Bear]

I buy all my bolts from this seller on ebay. Seems to have most things, cheap, and it usually turns up within 2 days even being second class.

http://myworld.ebay.co.uk/benb4ll?_trks ... 7675.l2559

Just dug this thread out, looking for tightening torques for my steering rack.. Good ebay find here.. shall try him out soon..

[Grrrmachine]

How does it compare with this?

http://www.e30zone.net/e30zonewiki/inde ... e_Settings