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The Bikesmith, Seattle, shutting down - Page 10

post #136 of 137

Re: OT: Motorcycle skid plates Was: Re: The Bikesmith, Seattle,

Carl Fogel wrote:
> Something in this design must account for why fairly loose motorcycle chains under far greater
> loads in both directions rarely if ever de-rail, even with the rear suspension thrashing up and
> down, while fixed gear bicycles derail more easily and more often, if I understand what the fixed-
> gear folk are saying.

I'd guess you're right. Most bicycle components were designed to make shifting *easy*. Imagine
putting a bicycle-type front derailer on a motorcycle and attempting to shift chainrings. Just how
long do you suppose that dearailer would last? (rhetorical question, of course). That should give us
an idea about the relative ease of chain derailing.

I don't know what it is about the motorcycle chain design that makes it harder to derail, but I'm
guessing it's the width of the parts. Imagine the extreme case where the cog and chain are 1 m
wide but the pitch and tooth profile remain the same. That chain would be very difficult to
derail, I'd think.

I think the relative size of the cogs is probably not a significant part of the difference between
bikes and motorcycles.

As to this part of your message:

> ...while fixed gear bicycles derail more easily and more often, if I understand what the fixed-
> gear folk are saying.

Fixed gear bicycles, set up properly, are actually quite unlikely to derail. A poorly adjusted fixie
is quite likely to throw a chain.

To learn about this first-hand, I propose the same experiment that I proposed before. You can do
this all in your workshop. Take the chain off your bike, shorten it, and route it to your
favorite gear to make a singlespeed. Adjust the wheel properly for chain tension and then try to
derail the chain using your front derailer. Don't try too hard -- you don't want to lose a
perfectly good derailer!

Now readjust your wheel so the chain has plenty of slack (or insert an extra pair of links). Again
try to derail the chain. See how easy that was?

Dave dvt at psu dot edu
post #137 of 137

Re: The Bikesmith, Seattle, shutting down

I have hired Val at my shop.
Aaron's Bicycle Repair in West Seattle.

I too often went to Bikesmith for 'therapy' as I called it. Val is my friend and I am proud to work with him.

Come visit us.
www.RideYourBike.com
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