B-Tension screw adjustmen on SRAM X9 rear derailleur

d3matt

I'm new to biking and need some help. I found this page and video a good quide, but I'm having problems adjusting the SRAM X9 rear derailleur on my Boardman Team FS. I've got the high and low stops setup and the cable tension about right. Next is the B-Tension adjustment to get the gap between the top jockey wheel and the largest cog to around 6mm (as per the SRAM manual). The gap is currently around 18mm and the B-Tension screw was all the way in.

If I unscrew the B-Tension screw out, the derailler does move forward, but due to the position of it, the gap doesn't close significantly. With the screw all the way out, the gap is smaller, but only about 10mm. However, the chain slack is then really excessive, as the derailleur is almost horizontal.

I've taken some video with my phone. It's poor quality (inside dark shed), but it might help.
http://www.youtube.com/watch?v=D8WxrlPsFHc
http://www.youtube.com/watch?v=o8SAzIKGphM

nicklouse

what gears are you in? big rear and?
have you changed anything?

d3matt

I've just realised that the chain wasn't on the largest rear end cog when I took this video. However it was when I was doing the adjustments for real. The chain was on the smallest cog to show the amount of chain slack when in this position, when the B-tension screw was adjust out which gave me the tightest gap.

Bar Shaker

I'm sure my set up would give that amount of slack too, in small/small, its just a situation you would never find yourself in when actually riding.

10mm jockey to cog would do it, its the big gaps you want to avoid as they will lead to accelerated cassette wear.

d3matt

I called into a Halfords at Winchester yesterday and they had every boardman bike on display. They were like mine, with the b-tension screw wound all the way in, with a cap of around 2cm. I questioned it and the guy said that was fine. I don't believe him.