chain rings vs rear cassette : is it worth changing rear cassette?
I'm considering making a minor change to the gearing on my bike.
I'm quite happy keeping the standard chain rings that I have however, I do spit chips a little every time I'm on a hill >7% when everyone around me drops into granny gear on compacts and blithely spins past me using a 34:26 gear while my granny gear is 39:26. (yes, yes, kudos to all of you who don't need granny gear to get up hills).
To resolve this, I'm looking at changing my rear cassette from the 13-26 I currently have (Campag) to a 13:29.
My question then is, how much benefit do you think I might get from changing to the 13-29 cassette? I don't know the configuration of the gears and I'm too tired to look it up right now, but the small one is a 13 and the big one is a 29... I've no idea what's in between. If I have the option to fiddle with the 'in between' gears, what size gears might you recommend?
Bearing in mind that my decision not to change from standards to compacts is founded largely on my being unable to afford a new crankset, so despite that being a potentially good option, it's not going to happen. Not to mention, I like the standards and, given my smallest rear gear is a 13, I want to keep my 53 up front!
:-)
Thanks all.
Replies to This Discussion
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Permalink Reply by Paul on -
oops. fixed now.
I should check these things when I first do them, sorry.
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Permalink Reply by Paul on
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Frank, the 50/40 setup was an import from Japan - Back when Bridgestone made bikes as well as everything else they do. It was a lovely bike, until I destroyed the rear derrailleur mount earlier this year.
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Permalink Reply by Tim B on -
Paul, sounds like you had a compact crankset to start with, not so easy the other way around.
If Juz's bike has 39-53 rings on it as standard, then its likely they are normal 130BCD (bolt circle diameter) cranks or whatever it is Campy do. With shimano, the smallest front ring you can use is a 38T, nothing else will fit a 130BCD crank. You need to go to a Compact Crankset (BCD of 110mm in Shimano land) to put a smaller ring on it. Once you have a Compact Crank, you can virtually put anything on it. With mine I've had 34-50, 36-52 and 39-53. Plenty of after market places to buy any size chain rings you want, just a matter to make sure they fit and your front derailleur can handle the difference between small and large chain rings (shimano is a 16T difference, dunno about campy)
Interstingly Shimano's new 9000 series DuraAce will be coming out only in a Compact configuration (although proprietary spacing) that will fit all of their chain ring combos rather than have to manufacture two different sizes
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Permalink Reply by Gemma K on -
Campy runs 135PCD.
To run smaller than 39 you need compact.
Just change the rear casette and be done with it!
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Permalink Reply by Dahondude on -
Jus, I can't find much about cog spacing on a 13-29 but you'll end up with a few largish jumps. I've also read that you might need to get a new rear derailleur since the short arm one you have may not provide enough reach to cover the 29 tooth. Might be worth talking to a decent bike mechanic...
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Permalink Reply by Juz on -
I've found that my current casette goes:
13-14-15-16-17-18-19-21-23-26with the 29, I'll have:
13-14-15-16-17-19-21-23-26-29(Thanks to Tim B for the link to that info earlier)
With the 29, it's only a 2 or 3 tooth jump at any point along the cassette, is that going to feel like any more of a large-ish jump than I currently have? I'm not sure if a 3 tooth jump is different at the big end of the cassette than at the little end... ??
As for the rear derailleur, I'll have to check that out with a mechanic and then my budget. Thanks :-)
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Permalink Reply by Patrick O'Kane on -
It will feel like a large jump, mine goes 24-28 but realistically you won't be making that great change that often for it to be an issue.You just have to decide if you can live without the 18 tooth cog and a bit less flexibility in the middle of the cluster. For a hubbard like me it makes no difference.
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Permalink Reply by Tim B on
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Juz, you already have a 3 tooth jump from the 23 to the 26 so the jump from 26 to 29 will be similar to that.
Actually, 23 to 26 is around a 13% difference, 26 to 29 an 11.5% difference.
Check out Sheldon Browns gear calculator, Change the "Gear Units" field to Gear Inches (the numbers make more sense to me), add your two chain rings (39 and 53) and select your cassette sizing (they have both the 13-26 and 13-29 in the drop down list) and hit calculate.
http://sheldonbrown.com/gears/
I guess you could look at it as having a 9 speed cassette With the range that you already have (minus the 18t) with the 29 waiting around till you need that bail out/ easy spin gear
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Permalink Reply by Dstone on -
+1 Short cage rear mechs are not nice on 29t.can be quite rough and noisy.
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Permalink Reply by Paul on
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Ahh, Tim, yes, my mistake: only with compacts can you go below 38 teeth on the lower ring for the 130pcd.
Ignore me Juz, I'm confusing myself from one bike to the next; I was thinking of my Giant which is on compacts running 50/34, and writing about my old commuter which is running the 15 year old stuff... after all, it's an 8spd cassette vs a 10spd...no comparison! :)
With what Gemma K noted regarding Campag running 135pcd, and 39 being smallest ring to suit before going to compact, I better understand your constraint; however, it could be worth considering that you might not need to drop all the way down to 34. I stand by what I said, I found a really noticable difference going from a 40 to a 39 on the same sized cassette; so it will depend on the availability of different sized Campag rings: you might find a world of difference with only a small drop. Then, it depends on your fdr... and comparing what provides the better gear range for the dollar: compacts & fdr change(maybe), or cassette and rdr change(again, maybe).
So without any knowledge about Campag component pricing, or any further ado; exit stage left Paul....
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