[earn it]

I have had my rear derailer sucked into the spokes on my giant ac while riding hard on fast rough single track. Three times. Busted spokes, derailleurs, hangers and chains!!! This bike works great until the drive train self destructs in an instant. The lbs says that there is no reason other than a stick or rock hit the derailleur and pushed it into the rear wheel. I think it is severe flex in the rear wheel and triangle. Anybody got any ideas on what causes this and any possable cures??

 

[fred3]

Don't see how rear flex could cause a lateral move in the derailleur. If it's all installed correctly I'd have to agree with the bike shop unless your hanger is bent, your upper limit is not set properly. Maybe if it is the rough terrain causing it(never heard of that happening) you might want to look at a single speed.

 

[Jayem]

Anybody got any ideas on what causes this and any possable cures??

Check the chain length.

 

[shiggy]

Causes:
A stick or rock hit or stuck in the derailleur and pushed it into the rear wheel.
The derailleur is misadjusted.
The hanger is bent and/or loose.
Your chain is too short.

Cures:
Check all of the above.
Stay out of the (and the close to) big-big and small-small gear combos.

 

[mechmann_mtb]

something that might help protect the RD is the Specialized RD protector. i have one that came on my enduro. it wouldn't have helped my XTR RD when i bashed it on a rock in sedona (bent it all to hell) but it can't hurt.

 

[Mudflaps]

something that might help protect the RD is the Specialized RD protector. i have one that came on my enduro. it wouldn't have helped my XTR RD when i bashed it on a rock in sedona (bent it all to hell) but it can't hurt.

This type of item will help keep the derailleur hanger from getting bent (the usual cause of derailleur going into the spokes).
Otherwise I completely agree with what Shiggy said, with one addition being to check the spokes for good (relatively high) tension. If a wheel were flexing excessively, it could suck a derailleur if you are in first gear. For this, have the wheel looked at by a shop person who has a very good reputation for his/her wheelbuilding abilities. Keep all of these things properly adjusted and you'll keep these events to a minimum, not completely out of your life, there is still the rogue stick here & there.

 

[deathonwheels]

I have had my rear derailer sucked into the spokes on my giant ac while riding hard on fast rough single track. Three times.



Which RD are you using???

 

[earn it]

Shimano xt rear derailure, adjusted by several competent mechanics. The chain is not too short. This happins when going fast (actually racing on downhill trails) and the chain is on the big ring and the small cog.That is a long way for the rd to move to reach the spokes. I am at a loss and will likely get a new bike since this seems to be bult into the design. I was hoping sombody had the same problem and found a cure.

 

[james_caswell]

Shimano xt rear derailure, adjusted by several competent mechanics. The chain is not too short. This happins when going fast (actually racing on downhill trails) and the chain is on the big ring and the small cog.That is a long way for the rd to move to reach the spokes. I am at a loss and will likely get a new bike since this seems to be bult into the design. I was hoping sombody had the same problem and found a cure.

I also have a gaint ac 06 model, like ur self i have been through 2 new drop-outs and one new RD in a period of 2 weeks. this usaly happens after a serious downhill session but allways brakes on a flat surface. i dont have any solutions but im very keen to know if anyone dose have??

 

[earn it]

James, you own an 06 ? I did not know that the giant still made this model. I am sitting here wondering how much you weigh. I am 180 lbs and race several times a year @downhill events. This bike is sweet until the self destructing chain busting derailure twisting hanger bending event occurs at speed on smoother faster sections of trail. What did the lbs tell you caused this?

 

[james_caswell]

James, you own an 06 ? I did not know that the giant still made this model. I am sitting here wondering how much you weigh. I am 180 lbs and race several times a year @downhill events. This bike is sweet until the self destructing chain busting derailure twisting hanger bending event occurs at speed on smoother faster sections of trail. What did the lbs tell you caused this?

Yeah you can still purchase this moddle in australia, i bought it about 1 month ago. i also way 176 lbs. the majority of riding i do is all free ride. The bike shop told me that it was very unlikely that the RD would have shifted into the spokes and blamed the problem on somthing thats hit the RD like a stick or a rock. Have you got yours fixed yet? and also is it still playing up?