Hi All,
I recently purchased a compact 50/34 and cassette 12/27 and have dura ace di2. For some reason I can not get to shift into the rear cog with the most number of teeth. I was reading about something with reversing the b limit screw… but wanted to post the question here to see if I can some help.
thanks
chris
Hi All,
I recently purchased a compact 50/34 and cassette 12/27 and have dura ace di2. For some reason I can not get to shift into the rear cog with the most number of teeth. I was reading about something with reversing the b limit screw… but wanted to post the question here to see if I can some help.
thanks
chris
Have you tried the auto-trim feature of Di2? That usually solves all RD related adjustments for me.
Did you have to adjust the chain length?
Might also want to check the limit screws
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This same thing just happened to me when I changed frames. I adjusted both limit screws and also the b screw several times and still couldn’t shift all the way up. After trying several things I realized my chain was too short and that’s why the RD was maxing out when I was on the big ring. If you can shift all the way up on your small ring, but not when you go to the big one then you might have the same problem. Hope it helps!
Bent derailleur hanger is always a possibility too…check that if the above things fail
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I agree with the advice about changing the chain when you change to compact ring.
Here is something else that might bug you going from big to compact ring: You might want to look at the big ring derailleur and make sure it’s the correct height on the downtube. The bike I bought used had a compact and it wouldn’t shift correctly up to the big ring. I took it back to the shop a bunch of times. What we finally figured out was that the big ring shifter was positioned correctly for a standard ring, but not the compact. We lowered it, and the bike shifts great now.
First and foremost I would recommend you take the bike into a shop you trust and ask them to help/show you how to fix this. It sounds like a limit screw adjustment or bend derailleur hanger. Di2 dosnt have an auto trim feature, it has a digital barrel adjuster if you will. Same way you add or subtract tension with your barrel adjuster on a mechanical bike you push the di2 derailleur up or down using the adjustment button on the A junction (front) (hold down the button for 1-2 seconds untill the solid red light comes on) then using the up/down shift buttons for the rear shifter to trim or fine tune your shifting.
Take a look at the alignment of the upper pulley and the cog that the bike is currently in. The chain should come off of that cog in a straight line and wrap down on to the pulley. If the derailleur is too far down in relation to that cog than you need to adjust it up, if it is too far up then do the opposite. If your derailleur looks like it is bent or tilted to one side then your hanger is bent. If all that looks good then shift up to the top of the cassette and take a look at your limit screws you are likely hitting your LOW limit screw and that is causing the derailleur to stop short of the largest cog.
If you chain is too short STOP!!! and take the bike to a shop immediately as you can do irreversible damage to your bike. Though you just put a compact on your bike so your chain would not be short… if anything it would be too long. There are numerous videos and demos online on how to do all of this but nothing beats showing your local TRI shop some love and having them show you the correct way to solve this issue. and if they cant figure out that your front derailleur is too high… go to another shop.
Yea not the chain because I bought a brand new one and cut it based on the calculations from park tools. Thanks for all the help!!!
Di2 dosnt have an auto trim feature, it has a digital barrel adjuster if you will. Same way you add or subtract tension with your barrel adjuster on a mechanical bike you push the di2 derailleur up or down using the adjustment button on the A junction (front) (hold down the button for 1-2 seconds untill the solid red light comes on) then using the up/down shift buttons for the rear shifter to trim or fine tune your shifting.
Maybe auto-trim wasn’t the proper terminology but there’s an auto-adjust feature you didn’t mention.
Hold down the button (while pedaling) for a few seconds and the Di2 will shift through each of the gears and auto-adjust itself. You may have to do some fine tuning in the manner you described but the auto-adjust feature has worked perfectly well for me.
That feature is Shimano’s crash recovery mode. In the event that the rear derailleur hits the ground hard enough the motor will disconnect from the link not allowing the derailleur to shift up or down. That is recovered by holding down the button on junction A for 5 seconds. What the derailleur does then is shift from the bottom to top to make sure that the system is working fine and that the derailleur will not jump off the largest cog. You still need to do all of your adjustments by using the adjust feature (holding the button down for 1-2 seconds and using the up/down buttons to adjust the rear derailleur)
What i did fail to mention and you have the terminology correct is that shimano does have an auto trim feature. It works to adjust the front derailleur as you shift through the rear cog set; but that dosnt pertain to this instance. As you shift higher on the cassette the front cage moves in towards the frame with the chain and as you shift down the cassette it moves away from the frame to keep the chain from rubbing. That is what they call auto trim.