Bicycle Mechanics - "Juniors" cassette + triple = shifting trouble?

From the Technical Service Instructions for the Shimano Ultegra cassette, CS-6600


If using the CS-6600 (14-25T, 15-25T, 16-27T) in combination with a chainwheel, use a double chainwheel. If you use a triple chainwheel, gear shifting performance will drop, and the bicycle may fall over and serious injury will result.

Forgetting the rather entertaining, "and the bicycle may fall over", and the rather silly, "in combination with a chainwheel" (What else would I do? Pull the chain with my toes?) they seem to be warning that by using one of these cassettes with a triple, there can be shifting problems.

What sort of shifting problems would result from using one of these cassettes on a 52/39/30 triple (Ultegra triple FD, 105-GS RD)? The bike came with a 12-27, FWIW.

The intended application, BTW, is when using my studded snow tires. I found last year that between the weight of the tires and slogging through slush, I spend a lot of time in the lower gears. With three and four tooth jumps between them, I never seemed to have just the right gear for any given condition.

I prefer close-ratio cassettes for three-season riding and wanted to try one in a lower range for this winter.

I've run 9-speed Shimno cassettes like 13-27 and 14-28 on my wife's Ultegra triple 52-42-20 with no shifting problems.

It sounds very silly. Why would the crank care what size cogs were used as long as the derailleur capacity isn't exceeded? I'd call Shimano and ask why this is considered a problem.

Thanks.

I can't think of anything either, and the part about the bike falling over smacks of lawyer interference and makes the entire thing suspect.

I'll ask at the LBS and if they don't know, maybe I'll call Shimano.

You won't really have any problems, but my guess is that they are just trying to discourage people from using a triple with these cassettes because of chain line issues. And since you can get more of a range with a different cassette, it makes sense to do it there instead. SHifting performance will drop as your chain line error increases, but it will work.

You think thats strange.

The CS 6600 junior clusters won't work on the wh 6600 wheels even though they carry the same part number as the normal cluster.

Good luck trying to make a close ratio cluster from one of these as they are rivetted together.

Good luck trying to make a close ratio cluster from one of these as they are rivetted together.

???
The "Junior Gearing" cassettes are in fact closer ratio than the "standard" cassettes. The central cogs
that are revitted together are straight-block, no teeth missing, no way to make them closer. The larger cogs are exactly the same as the standard cassette. Here's a link to the Shimano exploded veiw:
http://cycle.shimano-eu.com/media/techdocs/content/cycle/EV/bikecomponents/CS/EV-CS-6600-2370_v1_m56577569830608752.pdf

Based on Shimano's terminology I'm a 64 year old "junior", on most of my rides I'm running a 13-26 cassette.

Al

Fortunately, I'm not using Shimano wheels or hubs, so that particular compatibility issue shouldn't be a problem.

I'd originally planned on trying to make a 14-27 out of one of these and a few loose cogs. When I discovered the two carriers accounting for nine of the ten cogs, I knew that wasn't going to happen. And frankly, with the studded snow tires on, going any faster than a 52-16 allows, probably isn't a bright idea to begin with.

So I guess I'll just order the 16-27 and see what happens.

"junior" gearing is to meet USCF racing regulations for riders under the age of 19. On road courses the roll-out limit means that for a junior running 700x23 tires, the top allowable gear would be 52x14, so Shimano has come out with a line of cassettes to meet that need.

I'd originally planned on trying to make a 14-27 out of one of these and a few loose cogs. When I discovered the two carriers accounting for nine of the ten cogs, I knew that wasn't going to happen.

Oh yeah, you can make it happen. Two different ways to make a 14-27, neither is cheap.

1) Start with a 14-25 and replace the larger 3 cog cluster with the 21-24-27 cluster. since you already have a 12-27 you could simply combine the two cassettes. I have seen the 21-24-27 cluster for sale on the net but don't remember where.

2) Start with a 12-27, replace the 12, 13, & 14 with a first position 14 and insert a single 18 and single 20. These cogs may be more difficult to find but not impossible. If the 14 isn't a 10-speed you can grind down the built-in spacer to match the 10-speed spacer thickness. I was able to buy a first position 14 from Sheldon Brown a few years ago.

Al

Al, you're starting at the wrong end for my application. If I wanted three tooth differences at the low end, I could keep the 12-27 and its 21-24-27 cluster, which would be easy to do since I ride a 12-23 in the three seasons and the 12-27 just sits in a box.

But it's the low end I want to narrow. The 23-25-27 of the 16-27 was the base I was going to start from. If it was loose cogs from there, it would be easy and relatively cheap. It's not, so I'll stick with the 16-27 on the wheelset with the snow tires. As I said earlier, if I'm going fast enough to spin out in 52-16, I probably shouldn't be going that fast anyway on the studded snows.

Al, you're starting at the wrong end for my application. If I wanted three tooth differences at the low end, I could keep the 12-27 and its 21-24-27 cluster, which would be easy to do since I ride a 12-23 in the three seasons and the 12-27 just sits in a box.

But it's the low end I want to narrow. The 23-25-27 of the 16-27 was the base I was going to start from.

Ok, didn't understand that before. In fact I was not aware of the 23-25-27 cluster. It looks like you could combine a 15-25 with a 16-27 to make a 15-27 but the cost would be high and you may not see that combination as an improvement.

Al

It looks like you could combine a 15-25 with a 16-27 to make a 15-27 but the cost would be high and you may not see that combination as an improvement.

Right. Double the cost to shift by one gear.