Jynx

Hey guys. I was adjusting my derailler and have a question. Bike is full 10 speed shimano ultegra 6600. I set the high and low limit screws and they are fine.

1. Setting the cable tension. I took all tension off the cable. Shifted the rear shifter to go to the largest cog. chain stayed on the second to largest cog. i added tension until it went up to the biggest cog. shifted back and forth to make sure it was good and it is. my question is how much shifter travel should there be once you are in the lowest gear and tried to shift to a lower gear. there is a verry little bit. I could take that out with more tension but feel like that may be to tight. any input?

2. b limit screw. turning it does nothing. i screwed it all the way in and all the way out and noticed no difference. I am talking about the screw all the way on top in this picture. is that right?

operator

https://www.parktool.com/repair/readhowto.asp?id=64

Jynx

that is what i used which doesnt answer any of my questions

norwood

The screw all the way on top is used for adjusting derailleur position for chain wrap on the cogset. Which may or may not have a noticeable effect on your shifting. It has the effect of adding tension on the forward-backward spring movement of the RD.

AEO

for most road applications which don't stretch the limits of the RD specs, you can totally ditch the b-limit screw as it does nothing.

when you add a 29T or 30T to the cassette, then the b-limit might help the RD clear such a large cog.

Jynx

ok sunds good. i adjusted it and didnt see any difference so ill be good. thanks

IK_biker

The function of the B screw, and its adjustment is described very well in Barnett's Manual:
https://www.bbinstitute.com/manual.htm
Download Chapter 32, and follow the instructions. I don't think I can answer your particular questions any better than the said Chapter could.

We can debate here over the B-screw usefulness on RDs used with drivetrains within their specs until cows come home, but B-screws do a job, although sometimes a subtle one, and very well.

operator

You're joking right. There's and entire section in that link that says "B-Tension adjustment screw".

And you would be wrong.

The closer the jockey pulley is allowed to ride to the cogs while still retaining clearance from them in the entire range, the better it will shift. Go read barnetts, think about it and come back. Whether or not this difference is noticeable is irrelevant. No good mechanic leaves this on "some random setting" or tells others "it does nothing".

AEO

I've yet to come up with a combination of 26/27T cog and short cage RD where the upper pulley even came close to running into the cogs.

Jynx

Again the section that says "B-Tension adjustment screw" DOES NOT ANSWER ANY OF MY QUESTIONS. I have read park tools site. I know what the B limit screw does, that is not my question. My question is why when I turn the B limit screw it makes no changes. I'll make it clear for you, THE PARK TOOL WEBSITE DOES NOT ANSWER MY QUESTION of why the screw is not changing anything. Do you get it now?

I am running a 52-39 with a 12-25 cassette. It seems as though since I am not anywhere near the max of the rear derailler I do not have to adjust the B limit screw as it doesnt come close anyway.

shelbyfv

Check that the b screw is actually in contact with the tab on the rd hanger. The rd can be mounted incorrectly and the b screw is not pushing against anything.