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"anti-derailment device" anyone use one?

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"anti-derailment device" anyone use one?

Old 07-29-08, 06:43 PM
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mr handy
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"anti-derailment device" anyone use one?

So I switched to a Compact crankset a while ago and have been tweaking my front derailleur for best functionality. (switched from triple... got a great deal on a rival compact)

anyway I have been noticing that I drop the chain when downshifting the front on occasion, which seems to be the nature of the compact, and I was wondering if anyone else has used one of the "anti-derailment device"'s that Sheldon talks about on his sight, and sells... https://sheldonbrown.com/harris/derai...tml#deflectors

Anyway if you have an experience, opinion, thought, criticism, etc... let me know.
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Old 07-29-08, 06:44 PM
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Install it.

End thread.
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Old 07-29-08, 06:47 PM
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They work well. You'll even see them on a lot of pro bikes. If you can fit it on your bike (not all frames can), put one on.
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Old 07-29-08, 06:47 PM
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Originally Posted by operator View Post
Install it.

End thread.
I don't have one. I was wondering if anyone has used one, and if it's worthe the $10/ $15 to get one?
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Old 07-29-08, 06:51 PM
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Originally Posted by ericm979 View Post
They work well. You'll even see them on a lot of pro bikes. If you can fit it on your bike (not all frames can), put one on.
Thanks!

I will see if I can get one at my LBS (not open on Wednesday) Seems like a cheep piece of insurance, espeshilly in race situations, but I never heard anyone mention one.
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Old 07-29-08, 07:04 PM
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I use the Deda dog fang.
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Old 07-29-08, 07:31 PM
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Deda works quite well on standard (i.e. round) rings. And I like their clamping system.

If you use Rotor Q, you'll have to choose a mid-range (unless you happen to drop the chain at a very specific point). And even then, it's still not as precise.

Of course, if the rider performs really well on the Rotor Qs (like some dude who recently won a race in France), that will be a trade-off he'll have to live with.

And, no, proper front derailleur adjustment does not always guarantee the chain won't drop (usually at the worst time possible).
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Old 07-29-08, 07:35 PM
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just skip the Third Eye brand, the Deda or Ritchey one a is much better design.
fwiw, i had to dremel out a spot on mine to get it in the right spot, the bb lug on my LOOK prevented me from being able to get it low enough.
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Old 07-29-08, 07:38 PM
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Another point.

If you decide to install one, take into account bottom bracket shell flex if: 1) your bb shell is on the soft side; 2) you are heavy; 3) you are a wattage monster. (also note that, as you tighten the clamp, it can move a mil one direction or another)

It took several sprint drills before I dialed in a placement that left the most narrow gap possible without the small ring rubbing the device.

Last edited by LifeIsSuffering; 07-29-08 at 07:42 PM.
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Old 07-29-08, 08:00 PM
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I have never had my chain drop on my SRAM compact. Are you sure you have it adjusted correctly?
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Old 07-29-08, 08:06 PM
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Thanks for all the suggestions guys! I knew I could count on the large knowledge base of BF.

Originally Posted by LifeIsSuffering View Post
Another point.

If you decide to install one, take into account bottom bracket shell flex if: 1) your bb shell is on the soft side; 2) you are heavy; 3) you are a wattage monster. (also note that, as you tighten the clamp, it can move a mil one direction or another)

It took several sprint drills before I dialed in a placement that left the most narrow gap possible without the small ring rubbing the device.
I will make sure to consider all these things. It's going on my AL felt, so mounting should be simple, no lugs or the like in the way. I'm not sure about the BB shell, but seems plenty stiff to me, I'm 150lb and lean to the spinner side... AKA I don't think I'm a wattage monster...
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Old 07-29-08, 08:06 PM
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Originally Posted by yak View Post
I have never had my chain drop on my SRAM compact. Are you sure you have it adjusted correctly?
No...

I know it's close, it only tends to drop when I have been cross chaining, and forget to shift the back before I shift the front... normally when I underestimate a hill, or my ability.... Happens a lot.
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Old 07-29-08, 08:10 PM
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cheap insurance to protect an expensive frame.
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Old 07-29-08, 08:20 PM
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I have a Cervelo R3 and wanted to try one but none of them will fit on the rectangular shape of my frame so I made one myself (took about 10 minutes). I basically copied the N-Gear so it would fit on my frame. https://n-gear.com/

I took a 1" strip of metal and bent a "L" shape angle on it (about a 20 degree angle). I epoxied it to a small piece of rubber cut to the proper width so it would sit next to my inner chain ring. I connected it to my downtube with a couple of tie wraps. I haven't had a chain drop in over a year.
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Old 07-29-08, 10:05 PM
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My Synapse has a triple. It kept dropping on FD downshifts. It really was quite annoying. I took it into the shop that sold me the bike, asking them to take care of it. They worked on it, but the first time I took on another hill, it dropped again. Then I took it to a different LBS, asking them to adjust it for me. Again, the next time I attacked a hill I dropped the chain on FD downshift.

I think the issue is that the synapse frame is not terribly stiff, so with a rider on board putting pressure on the pedals, the adjustments that seem adequate when the bike is suspended on a rack in the shop are inadequate once I'm sitting on the bike.

Anyway, I was about to get one of those little devices of which you speak, but decided first to try adjusting the FD myself. I tinkered with it for about an hour, carefully watching the chain's reaction as I shifted while riding on a trainer. Finally I got everything dialed in perfectly, and in the last 250 miles it hasn't dropped once.

You may just need to adjust more carefully.
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Old 07-29-08, 10:14 PM
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Old 07-30-08, 10:28 AM
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Originally Posted by daoswald View Post

I think the issue is that the synapse frame is not terribly stiff, so with a rider on board putting pressure on the pedals, the adjustments that seem adequate when the bike is suspended on a rack in the shop are inadequate once I'm sitting on the bike.
I am not sure about the Synapse Sport, because it is Aluminum, but the carbon Synapse has a very stiff bottom bracket. Check out this report: https://www.cannondale.com/lab_report/synapse.html

That said, aluminum is certainly not known to be noodley.

I have never dropped the chain on my carbon Synapse. I have a compact double.
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Old 07-30-08, 10:30 AM
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Its a good device...simple and effective. Friction shifting is also pretty spectacular
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Old 07-30-08, 11:09 AM
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I e-mailed Nick at N-Gear "jump stop" and asked him to send me one of his... https://www.gvtc.com/~ngear/

Apparently he sends it to you and lets you try it before you pay... not bad and it' only $12.

My thoughts are that I have a bit of a mismatched drive train... 9spd 105 front and rear derailleur, kmc 10spd chain, and rival compact.

My guess is that all of this paired with cross chaining before shifting, causes the chain to drop. I have worked on the bike on the stand, and the small ring has a hard time catching the chain when in the big 2/3 cogs in the back. As i can see the problem is when the chain tries to angle off the big ring, the angle is to great and the chain over shoots the small ring, After the FD... if that makes sense. the FD is also aligned properly with the crankset.

PS. I have the lower limit on screw set so that the chain just clears the inner plate of the FD when in the Big back/ Small front combo.

I think I already said all this but that's whats up... I will tinker with it a little more today, and when I get the jump stop I will let you all know what i think of it.
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