Niloc

So I've got to fix my drivetrain one way or another and I'm pondering options. I just ran my first cyclocross race Sunday, had hella fun and didn't place too poorly. I ran 46/36 rings with a 9 speed 12-25 cassette. Right before the race my left shifter mount failed but I didn't need to get out of the small ring the whole race anyways. I understand other courses may be flatter with more straightaways than this one, so I got a little lucky.

I need to replace the front shifter (unless I go to a single ring, which I debated in another thread I recently started) but also the cassette is pretty tired. Sunday's race wasn't particularly muddy as I understand, but I did have some chain skipping issues on the rear end. The cassette being worn might have contributed, but it also got clogged. How often is cassette clogging a problem for you experienced racers out there?

So I'm wondering does anybody run, or think it would be a good idea to run fewer gears in the back, say seven? Heck I could go down to six with an old Deore XT hub with a 6 speed uniglide cogset 13-26 I have laying around. But if rebuild it to a 700c wheel and I'm thinking in the process I'd transplant a 7 speed hyperglide hub body onto it. Uniglide stuff is hard to find but 7 speed hyperglide cassettes are still readily available. I already have a 7 speed thumbie to shift it.

Here's why I'm thinking this could be an advantage for cyclocross:

- Cogs are more widely spaced, 5.0mm for 7 speed vs 4.34mm for 9 speed (and even less for 10 speed). I presume this would make 7 speed more resistant to clogging as there is more room between cogs? Maybe they would be easier to clean out in a hurry as well.

- The cassette overall is narrower (4.6mm shorter than 9 speed) so the rear wheel can be built with less dish on the drive side making it stronger. This is an advantage in general but I would think more so in 'cross than other road riding because you're intentionally careening over roots and rocks etc.

The main disadvantage of course would be fewer gears and wider intervals between them. However for 'cross it seems like the range of gears you actually need is not as wide as other cycling disciplines so this factor is not the disadvantage it seems. Hence many folks racing on single rings. Hence the closely spaced compact double cranksets. I've raced exactly one race so I don't have a lot experience to speak from but I did it on one chainring and 8 cogs between 13-25T (I never used the smallest cog on my 9 speed cassette). If I stick with my double crank (yes flargle) then wouldn't a 7 speed between 13-26 cover it decently? I'd stop at 25 but there doesn't seem to be a cassette in that range. Any slower than 36x26 and I should be running and I doubt even on a faster course I'll need more than 46x13. In fact I could probably look at getting a smaller big ring next.

Am I onto something here? Will the big companies start releasing special close ratio, mud shedding, seven speed cyclocross components? (that was a joke, they're too busy developing 12 speed)

pmt

Yep, seven is more than enough. One of my juniors runs seven, and I *love* that I never have to adjust it or tweak it or do anything to it. It just works, every race, perfectly, dry or mud. Great stuff!

Cynikal 

I would just use 8 speed at that point. The indexing is almost identical and the parts and wheels are easier to get. Trying to race cross on a 126mm wheel would be fine until you try to replace it in a hurry.

Niloc

Hmm not a bad point Cynikal. BTW my XT hub is on a 130mm axle (that was the mountain standard when road was 126mm) and it fits my frame which is 130mm OLD. Eight speed cogs are almost as widely spaced as seven speed so I'd keep that advantage, but the wheel would be more dished.

I don't have an 8 speed specific thumb shifter, but I could use my seven speed and push it past the end, using the limit screw to set the largest 8th cog.

Cynikal 

You are right, you don't need an 8 speed thumbie just use the limit screws for #8 . I have 2 bike with this setup. Keep in mind that you can mix and match road and MTB stuff of the 8 speed era.

ThermionicScott 

I think 7-speed is great, but do what makes the most sense for you.

GeoKrpan

7 speed cassetes are uber cheap, cheaper tha 8 speed, much cheaper than 9, and vastly cheaper than 10. Keep in mind that some people are racing CX singlespeed, 7 is an embarrassment of riches.

fietsbob

just the 7speed cassette hubs are long discontinued , the driver is narrower than the 8 speed by that 1 cog.

if you can lay in a few spares , Kool, in a 130 frame they can be de dished those 4mm past the 126mm

of the period, so less imbalance of the 2 sides spoke tensions .. So laterally stronger, a bit.

standard 6 is allowing more gaps for crud between them cogs,

I use either on my Touring bike , though freewheels .. Phil Hub.

RaleighSport

Gotta agree with this.. but it should be noted between TS and I there, almost all our geared bikes put together are 7 speed.