I had a pinch bolt snap at an inopportune time yesterday (Entering the left hander at Limerock) and i'm told it isn't all that isolated an issue. It seems to me keeping new bolts in there would be prudent, which (once I get the broken piece out) I will do to both sides. Just an FYI for those using these that drive their car hard..

 

Ahh, the left hander is probably one of the best places for that to occur, lots of runoff. I had them on my turbo but never had issues like you.

 

Dan told me it was pretty common, hence the FYI because that was something I never even considered. And yes, even if I went on a flyer there it would have been uneventful. After I let cars by in no-name I went up the downhill at about 5/10ths and even at that it wanted to toss me off.

So rookie, all set for the big race?

 

Seems like the only way that bolt would break would be in tension.

Time for a better bolt? I'd keep extras but I'd also upgrade to a better fastener. Does the bolt head have any markings?

 

Gary, I think that's the same bolt Dan replaced in my car over the winter when I had him do a check of my suspension setup.

 

Race not until May...

 

I'm going to the "bolt guy" tomorrow to get a few in the highest grade I can with am M8 Torx head. Dan also told me the arms themselves are prone to breaking. IMO the whole thing could be solved by making a solid arm (no cut for pinch bolt) and cutting a groove in the torsion arm for a circlip. If the arm still broke (which I highly doubt it ever would) they could simply beef it up. For now i'm ordering a spare arm and keeping bolts in stock.

 

Thanks for the heads up Gary.

 

Never had an issue with the pinch bolt, but I did break a lever arm at road Atlanta going over the alligators exiting turn 5 last year.

 

Mike called earlier tonight, I believe he said he broke both when he had her. Definitely a spares item for us.

 

Gary, put me down for a couple if you pick some up.

 

Gary, I'm aware of the early versions of the arms breaking, but not the bolts, that is odd, but goot to know.

 

I'll get 10 and hand them out like party favors...

 

A non pinch aluminum to steel spline fit would likely get loose after some time as the softer metal deforms unless it were a very tight heat to install type interference fit. Is there a torque recommendation for the bolt? To much pre-clamp pressure can open up stress risers in the thread roots. Can you see the mode of failure? Is there a small rust oyster surrounded by a recently opened up delta shaped failure zone across the rest of the split face of the bolt? If so try using a stainless bolt.

 

Kurt - I believe it is torqued to about 20 ft lb. I didn't get a look at the broken end as my shop removed it. As for the stainless idea, would that tend to gall more with the aluminum arm?