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Shimano 600 8-sp, 55 & 42 rng, 11-21 cass - extra gears???(6 posts)

Shimano 600 8-sp, 55 & 42 rng, 11-21 cass - extra gears???trogdor
Aug 6, 2003 6:30 AM
In preparation for a fairly hilly IM course (IM Madison, WI) I have started to think, after riding doing a couple long brick workouts, that I may need a higher gear on the cog for some of the steeper climbs.

Given my specifications on a 650cc Tri-geometry frame, what would be the more efficient and economic way to get an extra gear?

e.g. upgrade to Dura-ace 9-speed group ($$$), combine a makeshift cassette which enables you to be 11-23 (risky shifting), Dura-ace 9-speed shifter and 9-speed cassette from 11-23 and keep old deraileurs (risky)
re: Shimano 600 8-sp, 55 & 42 rng, 11-21 cass - extra gears???LC
Aug 6, 2003 8:20 AM
I don't know what "risky shifting" is, but 11-23 will work fine. If you don't use the 11 (although you might on 650 wheels) then 12-23 will have the same gears as before + one more.
re: Shimano 600 8-sp, 55 & 42 rng, 11-21 cass - extra gears???trogdor
Aug 7, 2003 5:29 AM
12-23 is definitely what I should've had on the training wheel and then put the 11-21 on the disc wheel for the race. . .hindsight = 50/50

When you say to use an 11-23 are you suggesting that I take the core 11-to-15 and marry a 19, 21, 23 to the core cassette. If so, I would imagine there may be some problems shifting between the 15 and 19 gears for the rear derailleur.

Thanks
re: Shimano 600 8-sp, 55 & 42 rng, 11-21 cass - extra gears???LC
Aug 7, 2003 9:20 AM
No problem for the deraileur to jump up 4 teeth, but you do have to allow an extra half second for the gear change.

Another option which I did for one specific race course is get rid of the 12 since the hill was so steep that if I was going to pedal down it I needed the 11 and the 12 was not very useful on that particular course. You would then end up 11,13,14,15,17,19,21,23. Although this was on a 700c wheel and 9 speed with the 16 in there too, you might benifit from a similar setup. It just depends on your legs and the course profile.
re: Shimano 600 8-sp, 55 & 42 rng, 11-21 cass - extra gears???off roadie
Aug 7, 2003 9:16 AM
I've built my own "frakencog" cassettes, and they shift fine. The one I use on my 8 speed road bike is a 13-14-15-16-17-19-23-28 made up of cogs from an old 9 speed LX cassette, some 8 speed road cogs, and 8 speed spacers. It works great on hills, though I'm not a monster climber and like to spin pretty high on flats.

If you decide to go nine speed, there's nothing "risky" about keeping the old deraliuers. There is no functional difference between a "9 speed deraluer) and one sold as an "8 speed derailuer". The only difference is in the SHIFTER, which controls the amount of cable pull. Given the same cable pull, both derailuers will behave identically.

Shimano makes an 8 speed cassette which has 12 13 14 15 17 19 21 23 cogs that might be a good bet in your case. Putting an 11 on the bottom would be easy and cheap, and then you could just pull the 21 out of there, and maybe replace the 17 with a 16.
How about going from a 42 to a 39?trogdor
Aug 7, 2003 1:08 PM
Both of your comments regarding the rear cassette are excellent and a friend has already suggested that I have at least 3 sets of cassettes at my disposal - ready to arm my bike with the necessary ammunition for my legs to use.

However, this same friend uses a 9-speed with 650cc wheels but uses a 55/39 front chainring. This seems interesting and would help considerably with the keeping a clean cadence as the gearing would remain 11-21.

Thoughts?