What is difference between double and triple front mech?
When I bought my CR-1 I had the shop swap the 105 double chainset for a triple, the left shifter has a label on it saying it was double or triple compatible so nothing else was changed.
For a while it worked well but I am now having trouble (occasionally) dropping onto the granny ring. I stopped at the Mavic support on a sportive recently and they said the issue was the the mech was set too high however I have had to do this because the inner plate of the cage fouls against the middle chainring when I go onto the big ring otherwise.
When I look at the profile of the cage the curve on the inner plate appears to have a much smaller radius than the middle chainring (40 tooth) so instead of following it's profile neatly I have to set it vey high so the trailing end does not foul but this leaves the front of the cage sitting a long way above the rings with the consequent poor shifting.
I guess my question is, is the mech on the bike a double or triple mech, as it was origionally set up to be a double or is it by definition a triple because it works with a triple chainset? Would a new Triple specific mech (6603) have a different profile cage allowing me to drop the mech a little lower?
Many thanks in advance.
For a while it worked well but I am now having trouble (occasionally) dropping onto the granny ring. I stopped at the Mavic support on a sportive recently and they said the issue was the the mech was set too high however I have had to do this because the inner plate of the cage fouls against the middle chainring when I go onto the big ring otherwise.
When I look at the profile of the cage the curve on the inner plate appears to have a much smaller radius than the middle chainring (40 tooth) so instead of following it's profile neatly I have to set it vey high so the trailing end does not foul but this leaves the front of the cage sitting a long way above the rings with the consequent poor shifting.
I guess my question is, is the mech on the bike a double or triple mech, as it was origionally set up to be a double or is it by definition a triple because it works with a triple chainset? Would a new Triple specific mech (6603) have a different profile cage allowing me to drop the mech a little lower?
Many thanks in advance.
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Comments
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Double and tripple front mechs do have a different profile, the tripple is deeper.Dolan Preffisio
2010 Cube Agree SL0 -
If it is a Shimano mech there will be a part number stamped on it. If it's a double, the number will likely end in 00, if it's a triple then in 03. Current 105 triple cranks have 50x39x30 rings - if yours has 40T somebody may have swapped it and thus created your problem. Note that other Shimano triple cranks usually have different size rings, like 52x39x30, 52x42x30, etc, so it's best to match the chainring size difference with the appropriate mech.
From your description, it sounds as if the derailleur is mounted at the wrong angle. I'm not familiar with the CR-1, but if it has a "braze-on" mech attached to a bolt-on frame mount it would be worth checking that the mount is fitted correctly. BTW, it's usually possible to "adjust" the angle of the cage somewhat by levering it with a large screwdriver, however, damage can be done, so it may be best to get your bike shop to do this if this is you(!): http://www.buncombe.k12.nc.us/986201030 ... clined.jpg0 -
satanas wrote:If it is a Shimano mech there will be a part number stamped on it. If it's a double, the number will likely end in 00, if it's a triple then in 03. Current 105 triple cranks have 50x39x30 rings - if yours has 40T somebody may have swapped it and thus created your problem. Note that other Shimano triple cranks usually have different size rings, like 52x39x30, 52x42x30, etc, so it's best to match the chainring size difference with the appropriate mech.
From your description, it sounds as if the derailleur is mounted at the wrong angle. I'm not familiar with the CR-1, but if it has a "braze-on" mech attached to a bolt-on frame mount it would be worth checking that the mount is fitted correctly. BTW, it's usually possible to "adjust" the angle of the cage somewhat by levering it with a large screwdriver, however, damage can be done, so it may be best to get your bike shop to do this if this is you(!): http://www.buncombe.k12.nc.us/986201030 ... clined.jpg
Thanks both for your feedback.
Yep the "someone" who put the 40T on was me :oops: don't know why but thought the one I was replacing was also a 40T and didn't realise til too late. Even so the arc of the mech cage is still tighter than a 39T so same problem still exists.
Think I'll give the screw driver adjustment a swerve, ripping the mount out of the carbon fibre downtube would be an expensive mistake I suspect!
I'll have a hunt around the mech and see if I can find the part number somewhere.
Cheers.0 -
The part number will probably be stamped on the side of the inner cage plate facing towards the frame...0
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Thanks Satanas, yes the number was there and it is a 5603 so I guess I have to accept my mistake with the 40T and drop it back down to a 39 or even a 38 to improve shifting.
Anyone want a 40T TA middle chainring, one careful owner.....0
