Stripped threads on fixed hub by pedalling hard

dombat

I accellerated away from some traffic lights this morning. Suddenly it felt like the sprocket was tightening a bit, but it didn't stop. I pulled over at the pavement and the sprocket was just turning by itself. I've take it off and the threads have completly stripped on the hub, the sprocket threads are fine.

Has anyone else had this problem? The wheel is less than a year old (the last weel had a snapped axle). Surely it can't be common.

I'm running 48x20 and I'm 100Kg.

dombat

Just found the answer, the sprocket has 3 tiny cracks in it's thread. I presume under load the cracks "open" enough to slide the sprocket over the hub threads.

Pete Beer

What hub is it?

pete.whelan

More to the point, what make of sprocket. If it is a cheap Cyclo one, then they are stamped and pressed and notorious for killing hub threads (as well as not being very round)

dombat

The hub is "On-One" branded and the sprocket is the one that came with the bike. On closer inspection it is very poor qualty, the face that meets the hub is not flat at al, it's almost tapered. It does look pressed too. Oh well, live and learn.

alien8

Not common but definitely not uncommon - I've known people do this before. I leave a free-wheel on the other side of my flip-flop just in case so at least I can get home.

spartacuscp

I had exactly the same problem with my on-one rear wheel. I stripped the thread. I ride the 48/20 combo and am 70kg.
I sent it back to them and they replaced it free. Otherwise the pompino seems a fairly priced package. I pressume they still churn them out with deficent brakes. I tried swopping them for damp toilet paper and found a massive improvement. Then switched to flat bars and mountin bike cantilever brakes which are amazing.

Monty Dog

As the hubs are only 15 quid, don't expect life-long durability. A quality sprocket like an EAI will last years in comparison. Just build up a White ENO Eccentric hub that uses a proprietary splined sprocket - huge amount of engagement and quality precision machining means it should last a while..

Dustine

I would give one of these a go:

http://www.velosolo.co.uk/756hubcvt.html

I built one up into a wheel for my fixed commuter, and its racked up over 4000 miles in the last 17 months. No problems, just added new grease a couple of times to the hub and adjusted the cones. Its a really simple but clever way of avoiding the usual problems of running fixed, the over/ under-tightened lock ring....

spartacuscp

Thanks Dustine.
I am interested in these as it looks like there is space for the chain to drop into should it come off .
I have ridden a fair few miles fixed over all terrain and only twice has the chain come off. Luckily i stayed on as my wheel locked up. This has put me off riding in a group on fixed in case someone behind runs into the back of me while skidding for England.
Is this the case with these hubs , would an unshipped chain just flop either side of the sprocket and not jam between sprocket and spokes ?
Thanks.

Dustine

It certainly looks to me like it would drop onto the hub shell or the spacers, depending which way it fell. Still a risk of it getting caught between hub shell where the sprocket attaches and the spokes/ flange, but i would think its much more likely to just sit on the hub. The other wat, it might possibly catch on the allen bolts, although i would think this is less likely also, and the risk of this could be reduced further by using those torx headed bolts. I can email you some photos of the hub on my bike if you want to put your email address here. I havent worked out how you paste them into these messages!!

spartacuscp

Thanks for that , they seem a bit safer than the standard set up.
I might give one a try.