Discussion of wide ratio 10spd Cassettes

The Rookie

I guess it depends on how often you use them, to be fair the spocket sizes are similar to the common ally chainwheel sizes, how often do you swap them?

satanas

Sane people wouldn't consider using alu cassettes for everyday use! Mildly insane people would use them only for occasional events with extremely long or steep climbs, i.e., TDF Alpine stages or similar; Lance Pharmstrong reportedly used TA alu cassettes for some climbing stages.

BTW, it might have been 1000 miles that was advertised life too, not km - I was thinking of the now defunct American Classic cassettes. If you totally trashed the cassette it'd probably last quite a bit longer, but shifting would get worse as everything wore.

Re cassettes being the same size as chainrings: That's why I'd be prepared to believe they might be less of a problem if there's supporting evidence forthcoming; IIRC, the SRAM GL has 29x34x40T and the Shimano one has 25x29x35x42T. However, it's worth bearing in mind that XX double rings are known to wear out rapidly, and that XTR double rings are most likely better made and only have to shift to one side, not both. Sensible people don't shift chainrings under high load either.

If you look at the Shimano XT/XTR triple cranksets, the middle rings are not alu, being Ti/CF for XTR and steel/CF for XT, and I'm fairly sure the XT inner is steel also; I'm sure Shimano wouldn't be using heavier materials than alu without a good reason.

Kowalski675

njee20 wrote:

Be interested to see how long those General Lee adapters last.

Not too well, based on the one What Mountain Bike mag have been testing for four months - hooking of the teeth and some broken teeth.

zerodish

I took a 39 52 tooth chainring set and put it on the rear. http://www.flickr.com/photos/63373992@N07/10695461823/ It turns out a Shimano old style megarange derailleur with a 15 tooth jockey pulley it will shift to a 48 tooth large cog provided the second largest cog is 34 or greater. I've made 38 39 40 teeth rear cogs and put 10000 miles each on them. It is important you find some method the strengthen us the splines or they will strip. 10 speeds are not ergonomic. The theory is simple at low speed gravity predominates and the difference in energy from shifting is proportional to the ratio of the two cogs. A high speeds aerodynamics takes over and the difference in energy from shifting is proportional to the cube of the difference of the two cogs. By noticing when I shift and adjusting the cog sizes I have found a 13 15 17 20 24 30 39 cog set is the most ergonomic. The high gear here would need to be some thing like a 11.5 to be ergonomic. I use 12 as the high gear. With a 20 38 42 front this allows me ride at walking speed of 2.5 mph up a 12 percent grade with a touring load to 28 mph with a reasonable cadence. Using 9 cogs with an 8 cog spacing allows me to build dishless wheels in 135 mm over lock nut.

supersonic

Can you expand on the ergonomics and "A high speeds aerodynamics takes over and the difference in energy from shifting is proportional to the cube of the difference of the two cogs"?

njee20

^^ this

Huh?

Chunkers1980

Don't think it really matters much in MTB. I'm in whatever gear my legs are happy to be spinning in at that point in time, which could differ from day to day on the same place with the same wind.

The Rookie

supersonic wrote:

Can you expand on the ergonomics and "A high speeds aerodynamics takes over and the difference in energy from shifting is proportional to the cube of the difference of the two cogs"?

According to bablefish the original language is English (BS).......

zerodish

Sorry about the typo. Use a calculator one is here http://www.hull.ac.uk/innovation/Bicycl ... ulator.htm Actual inputs from my own date is 4.6 mph with the 40 tooth cog and 6.4 mph with the 30 tooth cog yields .04 hp and .058 hp ratio of the cogs is 1.33 and ratio of the hp's is 1.45 not too bad agreement. In the 12 tooth cog 28 mph is .76 hp and in the 13 tooth cog 25.8 mph is .63 hp. Ratio of the gears cubed is (13/12)^3 = 1.27 and ratio of the hp's equals 1.21 not too bad agreement. Of course the agreement is not perfect the low speeds were climbing hills the calculator did not calculate and I did not enter. Also in real life you would use a different cadence climbing and at top speed. The best cog set commercial made is the Santana Tandem set it is 11 13 15 1719 21 23 25 29 34

cooldad

zerodish wrote:

Sorry about the typo. Use a calculator one is here http://www.hull.ac.uk/innovation/Bicycl ... ulator.htm Actual inputs from my own date is 4.6 mph with the 40 tooth cog and 6.4 mph with the 30 tooth cog yields .04 hp and .058 hp ratio of the cogs is 1.33 and ratio of the hp's is 1.45 not too bad agreement. In the 12 tooth cog 28 mph is .76 hp and in the 13 tooth cog 25.8 mph is .63 hp. Ratio of the gears cubed is (13/12)^3 = 1.27 and ratio of the hp's equals 1.21 not too bad agreement. Of course the agreement is not perfect the low speeds were climbing hills the calculator did not calculate and I did not enter. Also in real life you would use a different cadence climbing and at top speed. The best cog set commercial made is the Santana Tandem set it is 11 13 15 1719 21 23 25 29 34

njee20 wrote:

^^ this

Huh?

njee20

Indeed, I'm really not sure what your point is, at all? Higher gears require more effort?

Are you actually running a 20/38/42 chainset too? Bet that shifts a dream...

zerodish

My point is a 32 to 36 tooth shift is not worth doing. An 11 to 13 tooth shift is too hard on the knees. The closest thing to my cassette is built by Santana Tandems they use 11 13 15 17 19 21 23 25 29 34 The current cassettes are a compromise between one that shifts well and one that is ergonomic. Also removing a gear doubles the strength of the rear wheel by my own calculations and Santana's. Yes I'm really using a 20 38 42 front 12 13 15 17 20 24 30 39 rear. The 39 is 2.5 mm wide at the splines and 2 mm wide at the teeth this puts about the same amount of stress on the splines as a 28 tooth 1.74 mm wide one. The 39 shifts as well as the others even though it has no ramps or pins. And yes I really have toured 90000 miles and broke my first spoke a week ago. It was a used generic one and the wheel was temporary while building my new one.

cooldad

I'm sure you have a point somewhere, but I, for one, am still missing it.

Chunkers1980

Still not a scooby. Not much relevance to MTB.

supersonic

My point is a 32 to 36 tooth shift is not worth doing. An 11 to 13 tooth shift is too hard on the knees.

In your opinion, for your riding. But for others, it will of course vary.

njee20

Was about to say exactly what SS did - by what measure is it a 32-36 shift 'too hard'? Sticking in a 32 is harder on the knees than changing down...

satanas

Gearing is nothing if not personal, but I have to say that 24-30-39T jumps would drive me absolutely crazy. Please everyone, if it works for you, fine, but don't try to convert anyone else. (Unless you're the Borg.)