Snapped axle pinch bolts...

[paddy]

I might have applied a little bit too much force to my axle pinch nuts and I've snapped one of the studs. I've removed all four as I suspect I have over tensioned the lot. It looks a lot light the following link:

http://www.thumpertalk.com/forum/sho...ght=front+axle

Apparently, the studs are only available as part of the lower strut assembly which is now discontinued. So here's my question: Does anyone see any reason I couldn't just use four high tensile M6 bolts of an appropriate length? Please consider that I ride this bike on the motorway before answering. Alternatively, where might I be able to obtain appropriate studs.

The bike is a DR250 XC Djebel 1997 (SJ45A).

[CookMySock]

Don't put my name on it, but I would be looking for some bolts that had similar torque settings to the ones you removed. Problems occur when you use very strong bolts that are torqued lightly, as they have no stretch and they come loose easily.

You need to find a fastener sales specialist who has numbers to go with his bolts. I'd be looking for some bolt that has a maximum recommended torque of approx 1.75 to 2.0 times the factory recommended. It will have at least some elacticity.

Carefully torque these up to the factory recommended amount and see how they feel. If they snug down suddenly and then reach their maximum torque settings in an only a few degrees rotation, then I'd say they were too rigid.

Failing any of this, I'd take the problem to a real engineer, but make sure you get a concise and rational description of the problem before you trust anyone, and certainly not some know-it-all idiot on some forum.

Steve

[paddy]

Thanks Steve,

That would lead into my next fundamental problem - I haven't been able to find a torque wrench that covers that sort of range at less that $471. The motorcycle mechanics I have talked too (torqued too? - okay it wasn't funny) suggested just doing them up tight as that is apparently what they do.

Do you see any fundamental problem with using bolts rather than studs and nuts?

P.

[nosebleed]

Pinch bolts don't require much torque, but they do require a torque wrench for the exact reason you're posting

I've just bought a 1/4" torque wrench off SARGE for this very purpose... FAR less than $471.00

Flick him a PM

[paddy]

Pinch bolts don't require much torque, but they do require a torque wrench for the exact reason you're posting

I've just bought a 1/4" torque wrench off SARGE for this very purpose... FAR less than $471.00

Flick him a PM

Thanks, I might just do that. I'm still stuck with what do I replace the studs with though. I'm wondering about high tensile threaded rod, or just plain bolts. I'm not sure of the implications of either though. Any engineers out there?

[CookMySock]

Do you see any fundamental problem with using bolts rather than studs and nuts?

I cannot imagine why, but I haven't seen it, and possibly there is a very valid reason one way or the other.

[Crasherfromwayback]

Thanks, I might just do that. I'm still stuck with what do I replace the studs with though. I'm wondering about high tensile threaded rod, or just plain bolts. I'm not sure of the implications of either though. Any engineers out there?

Studs are better as if you over tighten them like you have...you fuck the studs...which is much better than tearing the alloy out of the fork legs when you over tighten bolts!

[Pussy]

Get an engineer to make you some new studs.
And use a torque wrench. As suggested above... Sarge is your man

[Pixie]

If the studs were 8 mm they should be torqued to 16.5 ft/lb.

On Suzukis that use bolts on the axle clamps the bolts break at around 17-18 ft/lb

[Henk]

Have done exactly what you have my wifes KDX200. drilled out the shot stud, helicoiled and used an M6 bolt, no problems a couple of years down the track. It's up to you if you think a bodge job that worked on a dirt bike will suit a road application. I'd risk it myself but then I'm not sure I would on a road bike she was using.

[paddy]

If the studs were 8 mm they should be torqued to 16.5 ft/lb.

On Suzukis that use bolts on the axle clamps the bolts break at around 17-18 ft/lb

They are M6 (8 mm) and apparently the factory specified torque is 8 ft-lbs. My smallest torque wrench bottoms out at 10 ft-lbs and I'm sure it's not very accurate at the bottom of its range. I figured that if I were to do them by hand I would end up going beyond 10 ft-lbs anyway, so I went ahead and used the wrench. I got nervous because I really couldn't tell how much pressure I was applying with the 1 ft long 1/2 wrench, so I thought I would just nip them up with my normal 3/8 ratchet. That's when I broke one off. Go figure.

[paddy]

Have done exactly what you have my wifes KDX200. drilled out the shot stud, helicoiled and used an M6 bolt, no problems a couple of years down the track. It's up to you if you think a bodge job that worked on a dirt bike will suit a road application. I'd risk it myself but then I'm not sure I would on a road bike she was using.

I've got the stud out fine. It snapped off right where it went into the nut. I was able to unscrew it using a pair of vice grips (in fact I've removed them all because I figure the others are probably over-stressed now as well). I'll head out to an engineer tomorrow and see if they can supply some studs to screw in. (Or advise on the sense of using bolts.)

[CookMySock]

If the studs were 8 mm they should be torqued to 16.5 ft/lb. On Suzukis that use bolts on the axle clamps the bolts break at around 17-18 ft/lb

This is important data. Try to find bolts that match this as accurately as possible. These bolts will be stretched nicely into their elastic region, without damaging surrounding parts.

If you use a higher grade bolt then you cant set them in their elastic region without pulling other things too hard, so you either cant set them properly or you break something else in the process.

Maybe you will have to destroy a couple of them in a calibrated torque-wrench session (not on the bike please) to find out if they are in the ballpark.

Nuts and bolts are not just nuts and bolts.

Steve

[paddy]

This is important data. Try to find bolts that match this as accurately as possible. These bolts will be stretched nicely into their elastic region, without damaging surrounding parts.

...

Maybe you will have to destroy a couple of them in a calibrated torque-wrench session (not on the bike please) to find out if they are in the ballpark.

Nuts and bolts are not just nuts and bolts.

Thanks Steve. As I alluded to earlier, I am planning to visit an engineer tomorrow and garner their opinion. Hopefully they can produce something appropriate. I am very concious of there function on the bike and I definitely wouldn't want they coming off at 100 km/h. Originally I had presumed that putting in bolts of a too-high torque spec would just cost more money (rather than having any mechanical basis) so your input has been really valuable.

[gatch]

I don't think that it is necessary to use the exact same studs if you torque studs of the same diameter to the correct settings and use a decent thread locking agent.

The only reason they would have snapped is because they would be made from poor quality material, not because they are intended to stretch x amount.