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FD mount bracket too high
The smallest gap I can get between my Ultegra 8050 DI2 FD cage and my big chain ring teeth (50 tooth ring) is between 3.7-4mm. It is my understanding the Shimano spec is 1-3mm. The FD mount bracket riveted on the seat tube is a couple of MM too high and the FD is mounted as low as it can go. Should I be worried about this? The FD seems to shift okay and I haven't had any dropped chain issues so far. The frame is used by some Pro Teams which I would imagine run 50/34 cranks at times. So I am wondering how this would be considered normal.
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I would say as long as shifting is still crisp, don't worry too much about it.
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Originally Posted by jmess
(Post 20430800)
The smallest gap I can get between my Ultegra 8050 DI2 FD cage and my big chain ring teeth (50 tooth ring) is between 3.7-4mm. It is my understanding the Shimano spec is 1-3mm. The FD mount bracket riveted on the seat tube is a couple of MM too high and the FD is mounted as low as it can go. Should I be worried about this? The FD seems to shift okay and I haven't had any dropped chain issues so far. The frame is used by some Pro Teams which I would imagine run 50/34 cranks at times. So I am wondering how this would be considered normal.
If the bracket is beefy enough, you can lower the bolt slot with a file. |
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Thanks, I thought about filing it down but there isn’t much at the bottom of the slot to work with. So unless I start having some shifting problems I am inclined to leave it alone. Surprising that no thought would have been given to a 50/34 crank when designing the location for the bracket attachment. I have the 2013 version of this frame but it has a clamp on FD bracket so there wasn’t any problem setting the correct clearance with 50/34 rings.
Originally Posted by Kontact
(Post 20431096)
Some front derailleurs have two holes to prevent this problem, Shimano does not. But your frame was built with 52t or greater chainrings in mind.
If the bracket is beefy enough, you can lower the bolt slot with a file. |
As said, above, leave it be if there's no problem and the changes are crisp and true. I bet that out of all the teeth on the largest chainring, some sit closer than the 3-4mm you state.
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Was probably right for a 53 39 double , but 50t is smaller..
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Di2 is surprisingly forgiving, so (as previous posters suggested) don't fix it if it ain't broke.
If it does become problematic, one possible fix is to change the crank/chainring size, either to 52 or 46 (the larger one to be compatible with the hanger, the smaller one to allow enough room -- possibly -- for a clamp-on under the hanger). I think you are right not to try to file or alter the hanger itself. |
A picture would help to determine whether there is enough material to file the slot and bring down the FD. I've done it a bunch, never had any problems afterward. |
I've filed several as well, and as long as there is a fair amount of material and there is a curved washer on the front of the mount to lock it all together, this is a reasonable way to shave a few MMs of mounting height. The added Di2 support screw takes some of the load off the braze on, anyway.
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The FD bracket has about 2-2.5MM of metal left at the bottom of the slot. So it should be possible to file it down by 1mm which would get me closer to or on the Shimano 3mm recommended maximum. I went for another ride today and I really can't fault the FD shifting. As others have said Di2 is pretty forgiving so I am going to roll with it now. Thanks.
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or just put the bigger outer chainring on.. 54 vs a 50t...
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