Trackday at Silverstone went well.. Coming into Stow corner giving it the full beans, on the brakes, grab the clutch to go down 3 gears.....clutch lever is solid, doesn't move at all. Bugger all engine braking. Poo everywhere. Had to coast round the corner in 6th and just kept it on the tarmac then clutchless shift for the rest of the session. Flange plate on the clutch drum sheared all eight bolts. Messaged Sigma performance about it (they make an identical unit) and the guy says he's never seen it happen and he wouldn't sell me new bolts or a new steel plate because it sounds sketchy and he or I can't even figure out how it happened. The bolts were tight (I checked when I put new plates in 1000 miles ago) and the bolts are punched on the other side to stop them coming loose. Bit lost really, absolutely brilliant when it works but don't really want to buy a whole new unit. Anyone selling or know anyone selling a DP or slipper clutch?
Looks like the screws have sheared due to the radial load of the clutch plates My slipper has tangs on the plate that locacte into the hub to take the force. The screws only clamp it to the hub Send it back to sigma Poor design
Have they sheared due to erosion of the heads over time? I've seen old clutches begin to polish/wear the screw faces. First plate in is a friction and as such, the plate will spin over the back plate as the drive is taken up. Could be a case of wear causing the ultimate failure rather than a design or component failure.
Hi folks, that is for the reply. Bit of an update... No surprises that I got very little return emails from the places I've contacted, and the places that did reply wanted nothing to do with supplying new parts, protecting their back incase something happens again which makes perfect business sense. I have drilled all the bolts out and they were all in there nice and tight so I guess the peening on the back of the bolts did it's job. On further inspection I think the constant forward and backward torque may have acted as a leaver pulling the bolts out with the angle of the countersinking. Stretching the bolts and allowing them to fail. I've got a new used assembly coming but I'm also doing donnington on friday and with fear it may not arrive in time, my plan is to get new M4 bolts and put them in and see how nicely it goes, if they don't go in very nice or don't tighten up too nice I'll go up to M5. Which ever bolt gets used I will be tig welding the bolt head to the steel flange plate so it can't come loose again. The clutch is basically scrap now so I'm trying to get some use out of it.
I also thought it was amazing that this drill bit didn't break, just twisted! Chinesiem drill bits aren't the best.
All bolts drilled out nicely, and new high tensile M4 bolts put in place of the OEM stainless ones, drenched in high strengh locktite and teeped over on the back. They all went in really nice and tightened up good so I'm quietly confident, hopefully the back up I ordered arrives before Friday!
