Driveshaftbolts

[jepsen]

I pulled my swingarm off, and then I read in my Haynes manual that the driveshaftbolts should be discarded and replaced. In addition they should be of the new updated shorter version without washer.
What is your opinion? New or reuse? Looks like I have the old long version of bolts with washer

[Kurt in S.A.]

You should use the shorter bolts...BMW had indications that the lock washer could break thus losing tension on the bolt and the possibility that it backs out. They put out a service bulletin on the change. The shorter bolts were torqued to within their elastic range to keep the tension on the bolt. A little blue Loctite doesn't hurt!! As for reuse, a repair shop would always replace them. If you were to finger thread them into the holes and find they went in/out easily, you might consider them unstretched and good to reuse again. For me, I'd probably not chance it. Small price to pay to use new bolts...they don't (or shouldn't) come out that often.

Kurt in S.A.

[RPGR90s]

I believe the "short" bolts are 14mm in length vs. 15mm for the "long" bolts.

The reason you need to replace them is because they stretch after being torqued and shouldn't be re-used. Same with flywheel bolts.

They're $2 ea. so no reason to take a chance on a driveshaft coming apart....IMHO.

I personally use the short bolts (26 11 1 242 297) with a drop of blue loctite, torqued to spec w/o washers on my R90s and have never had any loosening.

[mkj]

Always replace them, always have new set in stock they are very cheap. When I bought my R80/7 30 years ago the vendor was under the impression that the gear box was broken, I brought a airhead expert with me who whispered in my ear," this will cost £2 to fix if you don't buy it I will". I went to my local BMW agent and asked for a set, they quoted a 3 week delivery which was ludicrous , how can they operate like that, I got them next day from Motobins.

[gspd]

The recommended torque for the driveshaft and flywheel bolts will not even come close to stretching them.
Not even close.
We never re-used them on customer bikes at the BMW dealerships I worked at because we were instructed (by BMW) to replace them.
There were profit/liability issues involved which did not concern me.

However, on my own bikes, I re-use them all the time.
The ones on my present bike are original and have been re-used tons of times, doesn't worry me one little bit.

Those actual bolts will NEVER break. The MANY failures I have seen or heard of over the past five decades were all caused by the bolts coming loose and falling out. I would not install the old style longer driveshaft bolts with the lock washers because the lock washers are prone to breaking thus causing the bolts to come loose. We'd always find the pieces in the driveshaft housing or boot. The older style longer bolts can be shortened to compensate for the lack of washer so they don't protrude too far past the flange and rub on the seal or casing. Always clean everything impeccably and use blue Loctite and never re-use bolts that have fallen out or loosened during use, as these will undoubtedly have some degree of thread damage.

I've seen MANY failures where the bolts came loose in spite of (or because of) gobs of improperly applied Loctite. Loctite is one of those things where using just a bit is better than using too much.

[Kurt in S.A.]

The recommended torque for the driveshaft and flywheel bolts will not even come close to stretching them.
Not even close.

BMW said they were stretched under appropriate torque in their Service Bulletin. I guess the question is what do you define as "stretched"? Stretched doesn't mean to the point of plasticity or deformation...just in a way that introduces some residual clamping force and reduces the chances of the bolt from backing out. The bolt stretches elastically but returns to its original shape. That said, I agree that it's cheap insurance to just replace them after one use.

Kurt in S.A.

[gspd]

BMW said they were stretched under appropriate torque in their Service Bulletin.

Thanks K
Do you have a link to this service bulletin?

[ME 109]

I bet I've reused mine (short bolts) more than GSPD.
I even reused them three times in one day, but that's another story.

[Rob Frankham]

BMW said they were stretched under appropriate torque in their Service Bulletin.

Thanks K
Do you have a link to this service bulletin?

I would also be very pleased to see it... I have, for some time been building up a file of BMW service bulletins and I now have over 250 in pdf form... but I don't seem to have that one...

Rob

[Kurt in S.A.]

I gave all my service bulletins to Duane Ausherman, but I don't find this specific one on his site. Snowbum mentions 2078 on his site and discusses the elastic stretching of the bolt. I figured this would be good enough since you guys like him so much!

https://bmwmotorcycletech.info/drvshftb ... torque.htm

Kurt in S.A.