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Wheel and cassette issues-need advice!

Hello everyone,

Need some advice on changing wheels and cassettes. I recently changed my wheels from some standard Shimano wheels, wh500's or something (i.e. the worst model) to some Mavic Krysiums. As well as that I changed my rear cassette from a 12:25 to a 12:27 to help with taking on the big hills in longer events(i had to buy a new chain as well as apparently it wears with the cassette)....Anyway since doing this about a 2 weeks ago I have found that I am consistently slower when out cycling, i.e. I would go along before at around 19-20mph pretty comfortably, and now im grinding out 18mph with my heart rate about 10bpm higher- basically feels like i'm riding with the brakes on (and they're not as I checked!!)....Has anyone experienced this, or knows whats going on? Does it need time to wear in before it gets better, or could it be a problem with the new wheels or maybe the new ratios aren't working (this is what some guy said from the shop where i bought my bike-but surely there would be comparable ratios between the two set ups??)..Any advice would be great as this is really confusing/annoying me!




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    RobRob Posts: 209
    Hi Johnny, are you sure you're not just knackered & overtrained?[;)]

    What are the ratios in between the smallest/biggest gears? You may find one or two might be different, so the gear you comfortably cycled in before may be one up or one down from what it was before.


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    peddlerspeddlers Posts: 18
    I would set up your bike on a turbo trainer, rear wheel computer and similar work/rest day before doing a 30min to 1 hour session, using your new wheels and gears, make notes of speed in certain gears at heart rates, then you should put your old wheels back on bike the following week (replicate as best you can that day) and do the same set again. you will see if there are any major differences as the session and conditions are the same (roughly) and you can see what your hearts doing without fear of traffic, padestrians and pot holes.

    Another suggestion to the apparent up in your heartrate and drop in speed would be tiredness or if you had a cold/patch of illness lately as this can affect overall performance.
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    My guess is you are now missing a ratio that you used to use a lot.

    Assumming you are running 10 speed you would have had the following sprockets 12/13/14/15/16/17/19/21/23/25 so you are probably missing the 16 now.

    I am still only running 8 speed due to coming back to the bike after a seven year break but using my old kit. I went the other way and went from a 12/21 to a 13/21 so giving 13/14/15/16/17/18/19/21 (adding the 18) so no real gaps through the gears, the 13 with a 52 chain ring still means you can touch 30 MPH all be it with cadence in the 95 to 100 region and 21 is plenty for most hills. It worked for me on the New Zealand Ironman.

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    TTX PROTTX PRO Posts: 225
    Its pretty simple realy.Its all to do with how much tension is in the cain.Becouse youve changed the ratios.the chain is going to have more slack in it.all chains are mostly the same lenth so it doesn't matter what chain youve got.the only way to reduce the slack is to convert from a short cage rear mech to a medium cage rear mech.This should recuce the slack and give you more pull.Simple when you know how
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    What are you talking about !!!

    The last message was quite possibly the funniest thing I have read on this forum
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    KarlOnSeaKarlOnSea Posts: 28
    This is going to sound really silly, but have you checked the obvious things . . .

    Like that the breaks' are actually clearing your new wheels (i.e. you're NOT riding with the brakes on!)

    Or that the cones / axle is setup correct - does the wheel spin freely when you take it off the bike, and hold it by the axle?
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    JasonBJasonB Posts: 303
    I found this thread interesting, but due to lack of knowledge, did n't quite understand the gear ratios.

    Can somebody give me a quick overview of how it works. the only thing I know is going from 7 to 14 gears, gives you more gears. but changing sprockets, short cage, long cages, huh??

    I have realyl basic Shimano 7 speed 2200 rubbish. Can this be upgraded?

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    TTX PROTTX PRO Posts: 225
    ah but being a cycle engineer and having a nvq level 4 in a cytech bicycle engineering course so i do know what im on about plus i studied physics at plymouth uni.combine the two.
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    MikeyBMikeyB Posts: 135
    For advice on all things to do with bikes (except fashion) go to Sheldon http://sheldonbrown.com/gearing/index.html
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    Thanks for all the advice guys (and girls??). Anyway, since my last post i have seemed to overcome my blip. I think it was due to a number of reasons-exhaustion, getting used to the new gear ratios (i was spinning at 120 i think(no wonder i was going nowhere!)) and just wearing it all in. Anyway im back on track for Sherbourne, so fingers crossed- thanks for all the help!

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