gearing question

[martinrjensen]

I'm building up a bike and have a 12- 25 cassette on hand. If I buy a 13-29 cassette does anybody know if I will be able to swap cassettes without doing anything to the chain?
I'm thinking it might set up a condition where I can't cross chain, or physically shouldn't. I do know you are not supposed to do so for wear reasons.

[false_Aest]

i think the issue will be cross chaining.

[Ralph]

If you make it a little tight with the 13-29 (but still able to wrap the big to big), it will be just fine with the 12-25.

[Pete Serotta]

yep 29 in back and large in the front is not recommended. Try the other combo ones on the stand first. Also on stand check and see if rear der pulley is touching the 29 when the chain is on it. THis is just insurance and should be ok, that is why I just said check for I do not know what it is (although a 29 seems to be a CAMPY one :D :D PETE

[martinrjensen]

Thanks for the replies. I definitely would be more careful regarding cross chaining if I put this one. I'm thinking of certain "special occasions".
right now I'm over in Hawaii on the Big Island and they have this hill (Hina-Lani) I have to go up everyday if I want to ride my bike to the work site and back. If I had more than a week here I would probably go buy a different cassette for my bike. In fact now that I think about it, I just might see if it's available locally anyway....

[Ralph]

I'm not suggesting you ride big to big....what I'm saying is that is how you set it up. You don't want to accidently shift onto the big to big, and have chain too short to do that.

So if you set it up with chain barely able to handle all combinations with a Campy 13-29, although tight, you'll be fine with a 12-25 without removing links. Simple

[RPS]

I'm building up a bike and have a 12- 25 cassette on hand. If I buy a 13-29 cassette does anybody know if I will be able to swap cassettes without doing anything to the chain?
I'm thinking it might set up a condition where I can't cross chain, or physically shouldn't. I do know you are not supposed to do so for wear reasons.
If I understand your question correctly, what you are asking is whether you can cut a new chain length to work with both cassettes, so it’s essentially the same as asking whether it would work with a 12-29 cassette (assuming one is made).

Since the chain itself is not the issue, do you know what the specifications are for the rest of your drivetrain? What chainrings are you using, and what is your rear derailleur’s capacity? Without that information I don’t know how your question can be answered.

[martinrjensen]

Good point. Standard chainring and short cage rear der. I have a week left of work here and the hills are killing me with me 25 gear in back. If I understand your question correctly, what you are asking is whether you can cut a new chain length to work with both cassettes, so it’s essentially the same as asking whether it would work with a 12-29 cassette (assuming one is made).

Since the chain itself is not the issue, do you know what the specifications are for the rest of your drivetrain? What chainrings are you using, and what is your rear derailleur’s capacity? Without that information I don’t know how your question can be answered.

[RPS]

Good point. Standard chainring and short cage rear der. I have a week left of work here and the hills are killing me with me 25 gear in back.
I’m more of a Shimano guy so the following should be confirmed by others with more Campy experience.

First, even though the 13-29 may officially require a medium cage RD, many riders successfully use a short cage with a 13-29 cassette. I think whether it will work OK or not comes down to the derailleur hanger and on many modern bikes it will work OK. I suggest just trying it and going through the entire range of gears on the stand before taking the bike on the road for testing.

On the subject of total rear derailleur capacity (or wrap capacity) to cover a total rear range of 12 to 29 teeth (a difference of 17 teeth) and 53-39 chainrings (I’ll assume that’s what you mean by standard) which requires another 14 teeth, you’ll need a total capacity of 31 teeth. As I understand it, that exceeds a short cage RD capacity by a significant amount (I believe Campy rates short at 27T capacity). If these numbers are correct, there is a significant chance you may not be able to cover the entire range of gears. Given the choice, I’d personally install the chain just long enough to cover the big-ring + big-cog combination and then not use the smallest cog(s) when riding on the small ring if the derailleur runs out of take-up.


If nothing else, your dilemma shows why compact or even sub-compact gearing is a better choice for many riders. You can cover the same range of gearing with less wrap capacity. As I’ve stated on other threads, there is a reason not many cassettes are manufactured with a 13T small cog. Even 12T small cogs are becoming less popular. In my opinion smaller cogs in combination with smaller rings is a better choice in many ways.

[cmg]

i just went through this. the 13-29 will work fine on a bike setup for a 12-25 campy. I had to adjust the derailluer but afterwards it ran fine.

[palincss]

If I understand your question correctly, what you are asking is whether you can cut a new chain length to work with both cassettes, so it’s essentially the same as asking whether it would work with a 12-29 cassette (assuming one is made).

Since the chain itself is not the issue, do you know what the specifications are for the rest of your drivetrain? What chainrings are you using, and what is your rear derailleur’s capacity? Without that information I don’t know how your question can be answered.

Is there a modern rear derailleur that will not work with a 29T sprocket? Sheldon was of the opinion that all Shimano rear derailleurs, regardless of Shimano's ultra-conservative specification, worked fine with a 30T -- and, of course, Campagnolo makes a road 29T cassette and as far as I know doesn't say certain derailleurs in its line do not work with them.

[RPS]

Is there a modern rear derailleur that will not work with a 29T sprocket? Sheldon was of the opinion that all Shimano rear derailleurs, regardless of Shimano's ultra-conservative specification, worked fine with a 30T -- and, of course, Campagnolo makes a road 29T cassette and as far as I know doesn't say certain derailleurs in its line do not work with them.
Maybe, but it would depend on RD hanger location relative to axle. On most modern dropouts I think larger-size cogs clear OK but it can't be assumed just because it works for someone else (unless they have equal bike). On Shimano I have briefly installed a 30T cog under a 9-speed 12-27 in the past but decided to buy a 9-speed 11-28 instead for when I need wider ratios.

As I said before, I'm not into Campy equipment so I don't have all their information memorized. As far as I can recall, a few years ago the short cage RD was rated at 26T maximum cog size and 27T maximum capacity (wrap). I believe the official word was that a 13-29 required a medium cage derailleur. Obviously, ratings are based on worse-case scenario and most of the time it can be exceeded. Also, I don't have their newest catalog so I don't know the latest short-cage RD ratings.

In general when riders consistently need lower gearing I think they should consider smaller rings rather than continuing to increase cog sizes. An exception is when a larger cog is used but to achieve a wider cassette range (like 11-32). To me small rings make more sense than using a 13-29 unless it’s only temporary to achieve climbing lows on a quick basis that will be reversed.

[palincss]

In general when riders consistently need lower gearing I think they should consider smaller rings rather than continuing to increase cog sizes. An exception is when a larger cog is used but to achieve a wider cassette range (like 11-32). To me small rings make more sense than using a 13-29 unless it’s only temporary to achieve climbing lows on a quick basis that will be reversed.


Been there, done that and I won't do it again. 13-30 with a 36/48 works better and lasts longer than a 12-27 and 32/44, and no hassles trying to find a front derailleur to work with microdrive rings. The crank sets are much nicer in 110/74 than whatever the current MTB standard is, too. And with 110/74, you won't be stuck (as I am) with an obsolete Shimano standard that nobody supports anymore.

[RPS]

Been there, done that and I won't do it again. 13-30 with a 36/48 works better and lasts longer than a 12-27 and 32/44, and no hassles trying to find a front derailleur to work with microdrive rings. The crank sets are much nicer in 110/74 than whatever the current MTB standard is, too. And with 110/74, you won't be stuck (as I am) with an obsolete Shimano standard that nobody supports anymore.
palincss, in my opinion the extreme you are describing here is highly atypical for most road riders; and certainly not within the context of what I was attempting to imply. I can honestly say I don’t personally know a single rider that uses a top gear below a 50/12 on a road bike. Most riders I know with compact cranks use a 50/11 top gear. A few use 50/12. In any case I do agree with you that cranks with 110 BC or with 110/74 BCs are great choices. I have that on my Cannondale tandem and like the gearing flexibility it provides very much.

I was referring to compact cranks with maybe smaller large rings if necessary to replicate similar gearing. As an example, 53/39 rings with 13-29 cassette can be replaced with 46/34 (compact 110 BC) rings with a 11-25 cassette, or with 50/36 rings with 12-27 cassette.

It’s just about personal choice, and I recall that on this subject yours and mine are a little different. :beer:

[Ken Robb]

[QUOTE=RPS]palincss, I can honestly say I don’t personally know a single rider that uses a top gear below a 50/12 on a road bike.

Hello, My name is Ken and I'm a wimp with 50-34 cranks and 13-26 9speed Campy on my Strada Bianca. Now you know two. :)

[Ralph]

One of my bikes has a Campy 9 speed with a top gear of 52-14 (39-52 and 14-28). I can pedal hi 20's with that.....and if I go faster than that, I'm coasting down hill. About the same as a 49-13 or 45-12.

Lots of us know all about figuring different ratios.....but I like somewhat larger cogs and chainrings for a daily rider because they last longer.

[palincss]

One of my bikes has a Campy 9 speed with a top gear of 52-14 (39-52 and 14-28). I can pedal hi 20's with that.....and if I go faster than that, I'm coasting down hill. About the same as a 49-13 or 45-12.


52x14 is around 100 gear inches, same as 48x13 or 44x12. According to Sheldon's gear calculator, turning a 52x14 at 120 rpm on a generic 27" wheel gives you 35.8 mph. Slow that down to 90 rpm and you're still doing 26.9 mph.

[RPS]

[QUOTE=RPS]palincss, I can honestly say I don’t personally know a single rider that uses a top gear below a 50/12 on a road bike.

Hello, My name is Ken and I'm a wimp with 50-34 cranks and 13-26 9speed Campy on my Strada Bianca. Now you know two. :)
Ken, I was not being judgmental; it’s just that when I say I know “personally” I mean in person, not through the internet. I appreciate you and palincss ride with relatively low top-end gears, but I speculate you guys make up a small minority.

One of my present requirements when gearing a bike is being able to pedal comfortably at 40+ MPH at no more than 120 RPM. It’s not something that happens often, but when I want to do it I don’t want to miss out on the opportunity for lack of top-end gears.

[palincss]

I appreciate you and palincss ride with relatively low top-end gears, but I speculate you guys make up a small minority.


Well, sure - most club riders buy a road bike and ride it the way it came from the LBS. And most road bikes come with very high gears that until relatively recently were found only on tandems. I'm not sure whether most of those people are entirely satisfied with what they have, if they are even aware that there are alternatives, or if they just use the gears that seem useful and ignore the ones that are too high.

It's strange hearing 100 gear inches described as "relatively low", but of course, by modern standards it is. When I started, the big names in the TdF were riding with 52x14 top gears that seemed entirely adequate -- for some of the strongest riders who ever lived.

[flydhest]

Well, sure - most club riders buy a road bike and ride it the way it came from the LBS. And most road bikes come with very high gears that until relatively recently were found only on tandems. I'm not sure whether most of those people are entirely satisfied with what they have, if they are even aware that there are alternatives, or if they just use the gears that seem useful and ignore the ones that are too high.

It's strange hearing 100 gear inches described as "relatively low", but of course, by modern standards it is. When I started, the big names in the TdF were riding with 52x14 top gears that seemed entirely adequate -- for some of the strongest riders who ever lived.

you've got nothing but facts on your side, so you'll have to do better. :D

Seriously, though, your comment about club riders rings true, but I would layer on the fact that most "enthusiasts" don't know much about riding a bike (Ti Designs, can I get an amen?) and so they may be using the high gears, but spinning at like 40 rpms on the flats (this has happened on the shop ride that I started and used to lead). Using the gears and using them well are two very different things.