Profile Bitchin Bolt backup: Fine Thread 3/8 Hex Bolt with Washer

I was about 3/4 through my evening ride last Thursday at the Tapeworm, approaching the last stunt before the final climb out, when I went down for no apparent reason. It didn’t take long to figure out the apparent reason: I had lost my Bitchin Bolt and my crank had fallen off.

The Bitchin Bolt is the flush mount bolt that is used on Profile style cranks, it has a taper from the head to the threads and takes a special matching washer.

I called every local bike shop and no one had the right one in stock. I was referred to a shop I had never heard of before; he said he had a bolt that would work but not the flush mount type. I swung by, his fix was to use a Grade 8 Fine Thread 3/8 hex head bolt with a 3/8 Grade 8 washer. He said most bikers he works with use that setup rather than the Bitchin Bolt as you can get better torque on it.

The bolt he had was too long for my SH hub so I ran down to the local hardware store and got the bolt and washer for about $0.75.

Moral of the story: For less than two bucks, you can have a full set of back-up bolts for your Profile crankset.

Bitchin Bolt:

Advantage: Flush mount, protects crank against impact at bolt interface. Uses Hex Key.
Disadvantage: Can be hard to find. Expensive @ $20.00 per pair. Hex Key interface can strip out under high torque.

3/8 Fine Thread Grade 8 Hex Head:

Advantage: Cheap @ less than $2.00 per pair. Can get higher torque.
Disadvantage: Stick out a bit more. Does not protect crank at bolt interface against impact. Need to carry another wrench or socket to tighten.

Here is the Bitchin Bolt on a Profile style crank:

Here is the Hex Bolt on a Profile style crank:

Here is the Hex Bolt & Washer and Bitchin Bolt & Washer:

Bitchin Bolt On Crank.jpg

Hex Bolt on Crank.jpg

Hex Bolt & Bitchin Bolt with Washers.jpg

The rest of the Tapeworm trail after that last stunt is a difficult technical uphill anyways. You’d have been walking that bit anyways. :wink: I walk parts of that uphill.

I’ll keep an eye out for a lost bolt next time I ride Tapeworm.

You’ll notice I said last climb, not last ride, out. You want a good story or the truth?

Sounds like a job for the MUni Metal Detector.

Another bonus, the 3/8 bolt takes a 14mm/ 9/16 socket. The same size as the standard square taper crank puller.

Crank Puller.jpg

what if you get a allen key carriage bolt and the same washer? then you could go as far as de nubbing the cranks as well.

You would have to ride pretty funky to need to modify the nub on any Profile style cranks.

That’s handy to know, even though imperial sized bolts are difficult to obtain in NZ. What kind of cranks are those in the photo? They look like GT. I didn’t know that any cranks other than Profiles would fit on the Profile hub. What lengths do they come in?

Those GT cranks are Profile, just stamped for GT. I think the GT stamped Profile cranks were originally made to put on whole GT bikes.

My MUni has a Steve Howard one piece splined hub. He had found those cranks on e-bay a few years ago. I just Googled “Profile GT Cranks” and got am ebay hit for a pair of 175’s, with bike bottom bracket, for $200.

Also, given the 3/8 fine thread bolt head fits in a standard crank puller socket, I think they may be the same thing as the standard crank bolt used on a square taper. I haven’t confirmed this yet.

A standard crank bolt is M8x1 (8mm diameter 1 thread per mm.) A 3/8 fine thread bolt is 3/8-24 (9.5mm diameter 0.94 threads per mm.) Both thread specs can be found here under fine threads. The pitch is very close but the 3/8 bolt seems too big to fit. Apparently it works, though.