Tandem Upgrade



Upgrading the Tandem from 8 spd. to 9 spd.
(Archived from 2001)

Hopefully this is helpful for those who are considering upgrading to the new 9 speed system....

Our Burley Duet tandem came stock with 8 spd. bar end shifters, Shimano XT RD, and Shimano LX FD. To get low enough gears for touring, we changed the stock 54/44/28 chainrings to 54/38/24. We had an 11-30 cassette for "normal" riding and a 12-32 for touring.

After a recent hilly tour, we decided that we wanted to have a lower low gear. Microadapters to put a smaller chainring would not work without getting a longer bottom bracket spindle, due to interference from the oversized bottom bracket shell on the Burley. And we didn't want to mess around with getting a new tandem crankset.

But then the new 9 spd. came on the market, with an 11-34 cassette that didn't have any big gaps, unlike the 7 spd. and 8 spd. 11-34 cassettes. This would give us the range we wanted for all of the kinds of riding we do, without having to constantly swap out the rear cluster. So we bought new 9 spd. bar end shifters, a 9 spd. chain, and the 9 spd. 11-34 cassette and installed it all on the bike. I kept the chain long enough so I could have one extra link of slack while in the big cog/big chainring combination. Due to the larger 34 tooth cog, we had to turn the B-tension adjustment screw on the RD all the way in for the top pulley to clear the cog.

Downshifts were OK, but upshifts were sluggish. It turned out we needed a new return spring in the RD. We replaced the spring, and I installed a Rollamajig I had lying around in the garage. The shifting on the workstand was much better. But then on the road, when we were in the large chainring and the smaller cogs, the shifting wasn't very good. The adjustment that allowed the top pulley to clear the 34 tooth cog in the granny gear had the unintended side effect of keeping the pulley too far away from the smaller cogs in the higher gears.

At this point, I installed a new 9 spd. Shimano XT RD. I had to remove one link of the chain to get the top pulley to clear the 34 tooth cog, even with the B-tension adjustment screw all the way in. (The chain was still long enough to shift to the big/big combination.)

Again, I had to replace the spring in the new RD. I took the spring I had put in the 8 spd. RD and moved it to the new 9 spd. RD and then installed everything back on the bike. The same spring was slightly weaker in the 9 spd. RD compared to when I had it in the 8 spd. RD. (I didn't overstretch the aftermarket spring when removing it from the 8 spd. RD, so I believe this difference is due to the RD design.) This difference was noticeable in the crispness of the shifting.

So in addition to the Rollamajig and the new 9 spd. RD, I installed a Bassworm, and I also changed out the cable and all of the housing. This improved the shifting quite a bit, although it was never quite as crisp and clean as the previous 8 spd. setup.

However, the 24/34 low gear wasn't too much of an improvement over the 24/32.  To get even lower, we ended up installing a 19 tooth fourth chainring.  With this setup, the 19/30 gear was low enough - we didn't need the 19/34 gear.  So we changed out the 9 spd. 11-34 cassette and went back to an 8 spd. 11-30 cassette, using the original 8 spd. XT rear derailer and bar end shifters.

Our current 8 spd. system shifts noticeably better than our 9 spd. setup - I'm rather surprised, since most others have noticed equal or better performance.  Here's a couple of thoughts why:

bulletWith the 30 tooth big cog instead of a 34, the B-tension screw on the rear derailer can be unscrewed all the way out.  This allows the rear derailer to sit under the cogs better, improving shifting.
bulletLonger lever/cable travel per shift for 8 spd. bar ends vs. 9 spd. bar ends - if the adjustment is off by a certain amount, then it's a larger percentage of the 9 spd. lever travel compared to the 8 spd.?
bulletShorter chain with the 30 tooth big cog instead of a 34?
Page Last Edited (though probably not for content): 14 September 2010