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Aarrrgh! Chain Drop is Denting my Cadd 4 frame(10 posts)

Aarrrgh! Chain Drop is Denting my Cadd 4 frameroaddog
May 4, 2003 11:46 AM
Did the hills again yesterday. (In midwest Florida thats
San Antonio). But at a crucial moment chasing the
group - the drop into the small chain ring resulted in
a bent link and a bad cut into the chain stay. Can't
risk this happening again. Verified the derailler limits
are at the correct tolerance. Can't rule out operator error.
Lizard skins won't fit that close to the BB. The tight spot
is right next to the small chain ring. Is there some good solution
to provide protection? Are Cannondales more subject to this?
(The right chain stay shape is unique.) I'll have to
resort to electrical tape. crude!!
get a chain watcher(nm)merckx56
May 4, 2003 12:09 PM
Chain minder is Dangerousroaddog
May 4, 2003 3:23 PM
At least that's what my LBS says. They won't
sell me one. Why I don't know. Are they safe?
they're full of crap...merckx56
May 4, 2003 5:47 PM
I rode with one on my custom Merckx for years without problems. I don't see how they are saying it's dangerous. It's a little piece of plastic with a metal clamp inside of it. It doesn't interfere with anything. They are pretty cheap too. If you are worried about the frame and/or paint, and can't get the derailleur dialed in, it's worth a shot.
Derailleur adjustmentKerry
May 4, 2003 3:45 PM
You say that your "derailleur limits are at the correct tolerance" but if you are regularly dropping the chain, then something is wrong. The front derailleur should be nearly touching the chain in the small/small combination. Also, you might want to look at the angle of the front derailleur relative to the rings - you can use this angle to reduce the likelihood of chain drop by adjusting the rear of the cage away from the frame. Also, shifting under full load is possible, but is going to aggravate chain drop. And unfortunately, this is one of the downsides of Al and CF frames - they gouge relatively easily.
re: Aarrrgh! Chain Drop is Denting my Cadd 4 framekenyonCycleist
May 4, 2003 6:33 PM
what ratio u in when the drop occurs?
Here's the situationroaddog
May 5, 2003 3:43 AM
I was using a 12-27 Shimano rear cog.
Stayed in the big ring (53) while the
rear cog was in the 21. Then shifted
into the smaller 39 chain ring - when
my pedal met sudden resistance.
Possible issue: Shifting to 39 when in the 21...Spunout
May 5, 2003 3:50 AM
because the chainline is already pulling the chain off of the 39. When you downshift the FD, the chain keeps moving and you've thrown the chain.

On a campy system, I can beat this by downshifting only two clicks, then one more to beat the rub. YOu should be able to do the same thing on a Shimano system. For example, try not to downshift all the way at once.

Other than that, anticipate your small ring shifts and get down there while in the 19 or 17: Which provide a straight chainline to the 39 and will be a cleaner shift.
Check Out JumpStopjamesau
May 5, 2003 4:11 AM
Had same problem on my hardtail mtb; scratched chainstay and bent chain resulting in woe and trailside repair. Installed Jumpstop (www.gvtc.com/~ngear/) and hasn't happened since. Jumpstop is a simple, beautifully executed design.

See also,
http://www.mtbr.com/reviews/Chain_Accessories/product_20650.shtml

Jim
3M Scotchcal is the best!Tommy B
May 5, 2003 2:02 PM
I don't have a good answer for why you're dropping your chain, though I would check to the lateral "trueness" of your chainrings. Hard pedaling would exagerate any bend and may cause you to drop the chain if your trying to shift at this time.

I can, however, offer you a good, clean looking solution for protecting all the vulnerable areas of your chainstay. I use 3M Scotchcal to make clear custom-shaped chainstay guards for all my bikes and it works great. If you're not familiar with this product it's what all of the "clear bras" for cars are made of. It is thicher than regular bike-specific chain guard stickers and you can cut it to whatever size and shape you like.

I bought a small length of it (cut from an 18" wide roll) from an online automotive clear-bra company. I first tape a piece of tracing paper to my chainstay. Then use a combination of a pencil, straight-edge and freehand arcs to draw the template right on the frame. Remove the trace and clean up the drawing. Then spray-mount the trace template to the back of the 3M Scotchcal. Cut it out with an x-acto knife, peel off the backing and carefully place it on the frame. Rub it down with your fingers and it comes out completely clear!

I know this sounds like a lot of work, but you only have to do it once and it will last the life of the frame!

Here's one of many sites that sell this type of product. (I don't work for them)

http://www.thedingcompany.com/3m.htm