Road Bike, Cycling Forums banner
1 - 4 of 4 Posts

· your god hates me
Joined
·
1,605 Posts
Discussion Starter · #1 ·
I understand how a Dork Disk protects your spokes from a chain going past the largest cog. But I've heard folks explain that its primary purpose is to protect your spokes from catastrophic damage due to a rear derailleur getting bent into your wheel...and the more I think of that the less it makes sense.

The rear derailleur is hanging a good 6 or 7" away from the center of the hub. If it got slammed into the wheel, it would make contact well beyond the circumference of the Dork Disk. I can't see how a 5" diameter pie plate in the center of the hub is preventing the spokes from getting slashed to bits by a bent derailleur contacting the spokes 6" away from the center of the hub.

What am I missing?
 

· Registered
Joined
·
876 Posts
you're not missing anything. The disk won't technically protect the spokes from the rear derailleur going into the spokes. Practically it might if all the planets line up at the right moment etc. etc. but in general it just protects the spokes in case the chain comes off. A properly aligned derailleur prevents this from happening anyway.
 

· Registered
Joined
·
11,555 Posts
As an aside . . .

For a brief time in the 1970's, some bikes came with metal spoke protectors that actually ate spokes. To give the disk some stiffness, the sharp edge around its circumference was bent over at 90 degrees.That sharp edge made hard contact with every spoke it touched. From the first mile, the disk started sawing at your spokes.
 

· Steaming piles of opinion
Joined
·
10,520 Posts
Look at the upper jockey wheel. That's what's going to trash your spokes should something go awry. Wherever the chain goes, it gets there first, and because it can't move along with the spokes (like the chain is already doing) shifting it into the spokes is a very real problem.

All the dork ring really needs to do is provide a curb to keep the jockey wheel/derrailleur cage from hitting the spokes from hitting the spokes if A) the limit screw is out of adjustment or 2) a laydown bends the der. hanger in enough to let it happen. On a properly set-up and equipment-matched bike, it only needs to be a smaller bit bigger than the largest cog to do it's job.

You're right, the chance of anything bending a der into the spokes? After than impact, the spokes would be the least of your worries.
 
1 - 4 of 4 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top