Cotic roadrat disk brake mount

[vorsprung]

Please go easy on me about this as I don't know anything much about disk brakes

I am thinking about getting a cotic roadrat.  I already have a shimano disk brake generator hub front wheel
This has the electrical terminals on the right and the disk on the left
The roadrat comes with a fork that as the disk brake mount on the right

So to run the generator hub I'd have to run it "backwards"

Electrically this won't make a jot of difference as it is AC

But what about mechanically?

I have taken a shimano generator hub apart and I'd say it probably wouldn't make any difference provided that the outer shell didn't come undone

Your thoughts please.....

[vorsprung]

Here's a picture



Pretty isn't it?

[jellied]

Can't help but I'd very interested in any replies given this is the next bike intended for commuting.

[Paul D]

Not a helpful answer, but I solved this problem by hanging my shimano dynohub wheel up in the garage and getting Goldtec to build me a lovely XC Disc front wheel, then used my more than adequate for commuting Fenix torch.

Pretty isn't it?

Not in the slightest in cowpat brown. I take it they've stoppd doing 'anti-magpie black'?

[Greenbank]

I believe Mr Larrington runs a SON hub with disc mount backwards and has had no problems related to it.

[Chris N]

But what about mechanically?

I have taken a shimano generator hub apart and I'd say it probably wouldn't make any difference provided that the outer shell didn't come undone

Your thoughts please.....

Shimano advise against it (as do Schmidt, for that matter).  Mr Larrington uses a Schmidt with discs the wrong way round on his Roadrat and has had no trouble, AFAIK.  If you're worried, Cy might sell you a frame without the fork - then you could use a Kona Project 2 or some other disc-compatible fork (Bontrager Satellite?) with 400mm axle-crown length.

Pretty isn't it?

The bike, yes.  The brown, nooooooo.

[jogler]

Here's a picture



Pretty isn't it?

You naughty boy;you should not have posted that pic..I was becoming accustomed to the notion of not selling the Langster & fitting mudgaurds to it.
Now the indecision is with me again.
The colour looks o.k. to me.I am colour-blind & it looks much the same as the Langster currently does having been ridden on mud/cowshit cocktail lanes hereabouts.

[vorsprung]

Not in the slightest in cowpat brown. I take it they've stoppd doing 'anti-magpie black'?

Don't panic, the latest batch are in black and it's black that I would want meself

[rogerzilla]

Cotic have put the caliper in the correct place so it doesn't produce a wheel ejection force.  Early Hope calipers were also like this, but then they had to follow the (wrong) International Standard like everyone else.

I would go for a battery light, although the charging regime is a PITA compared to a dynamo.

[andrew_s]

It is a problem for any hub that has a load bearing screw in section, as do current Schmidt and Shimano dynohubs (the old black centre Schmidts are OK, but they have been out of production for ages).
If run the wrong way round, the centre will tend to undo itself, like the RH side of an Italian bottom bracket, or normal cranks/pedals used at the front of a tandem. How quick it will undo will depend on the quality of the threads, how tight it was done up, and any locktite present (or not).
If it undoes too far, the very thin wires connecting the generator on the middle of the hub to the terminals on the outside will snap, and you'll be left with a dead hub.

[tonycollinet]

With all that, I'd go for the alternate forks option. Will probably cost another £100 or so though.

[andrew_s]

Having considered it myself, I decided to accept the wrong side standard disc caliper location in order to be able to use a dynohub, and rely on lawyer lips, positioning the QR lever appropriately, and taking care.
Apparently the new Peregrine frames like I just ordered have the front dropouts facing forwards rather than down, which should resolve the disc ejection problem anyway.

[tonycollinet]

The disk ejection issue can't be that much of a problem else people'd be falling off mountains all the time as a result.

[Adrian]

Shimano advise against it (as do Schmidt, for that matter).  Mr Larrington uses a Schmidt with discs the wrong way round on his Roadrat and has had no trouble, AFAIK.  If you're worried, Cy might sell you a frame without the fork - then you could use a Kona Project 2 or some other disc-compatible fork (Bontrager Satellite?) with 400mm axle-crown length.

I decided that I was more concerned about my SON hub unwinding inside than I was about disk ejection and sufficiently concerned about it to question it with Cy. He had a frame in my size that was without a fork and which had a mark on the paint on the top tube. I bought that and fitted a P2 fork. I would recommend one as a winter weight commuter.

[Sergeant Pluck]

positioning the QR lever appropriately

I have a Roadrat fork so I ask out of interest only - and I note Rogerzilla made reference to this re his new bike-  how should the QR lever be positioned?

[vorsprung]

Given the problems with wheel ejection, backwards dynohub wheels coming unscrewed and confused iso standards the simple solution is: don't use disc brakes on the front.

I might put a disc brake on the back later if the mood takes me

[CommuteTooFar]

I was an early adopter of a right hand forward facing disc brake caliper.  Then I decided I wanted a hub dynamo.  I communicated with Schmidt via SJSC. They said that the generator could unscrew. They offered to make a special glued one for me but without any guarantee
against unscrewing. 

In the end I decided to buy the cheapest hub generator with disc bolts I could find. If it did unscrew it would not be a great financial loss.  This Shimano DH-3D30 ran backwards for about 15,000 miles when the fork broke and was replaced with a new fork with wrong but conventional disc caliper mounts.  The wheel has done a few thousand miles in the correct direction now and the hub is still fine.

[andrew_s]

I have a Roadrat fork so I ask out of interest only - and I note Rogerzilla made reference to this re his new bike-  how should the QR lever be positioned?

With the lever folded in below the disc caliper, so that it hits it if it starts to rotate.

The torque forces on the QR can be well over your bodyweight, even after allowing for your actual weight. If the QR moves a fraction under the braking force, and then your weight or the next bump pushes it back again, the QR will tend to undo a little each time.

[Mr Larrington]

I believe Mr Larrington runs a SON hub with disc mount backwards and has had no problems related to it.

He does and he hasn't.  I am given to understand that while Schmidt consel against running one backwards, the bit which unscrews is an absolute bugger to get off even if you've got the correct tools, so I'm not unduly worried.

[clarion]

Doesn't the front lamp suck light in?

[Mr Larrington]

Doesn't the front lamp suck light in?

The fonr light does suck light in, but then converts it to electrickery.  The dynamo boosts the amount of electrickery available, and sends five thousand voles to the rear light, thereby giving a form of ram-jet propulsion.

Or something.

[clarion]

Kewl.  iwoot!

[Tewdric]

Doesn't the front lamp suck light in?

The fonr light does suck light in, but then converts it to electrickery.  The dynamo boosts the amount of electrickery available, and sends five thousand voles to the rear light, thereby giving a form of ram-jet propulsion.

Or something.

Kewl.  That like some kind of large harddron provider like?

[tonycollinet]

Hmm

A ram jet ejecting voles - brilliant. If you know the mass of a vole, and the ejection velocity, it should be possible to work out the thrust (assuming a certain number of voles per second)

This in turn will tell you how far you can go, and for how long, with your tank of 5000 voles.