I ride a compact crank (50x36) and a 12x25 cassette, if I'm going up into the mountains will changing to a 11x28 cassette really make that much of a difference?? Any suggestions?
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I ride a compact crank (50x36) and a 12x25 cassette, if I'm going up into the mountains will changing to a 11x28 cassette really make that much of a difference?? Any suggestions?
You could also change the front chain ring to a 34 instead of a 36 - most compact cranks are 50x34.
And yes - switching to an 11-28 will make a huge difference. I used to run a 50-34 with a 11-25 and just switched to a 11-28 this spring. I take a lot of hills in my big chain ring now instead of switching to the small one, last year I'd switch to my small one.
If you go on Sheldon brown's site, you can use the gear calculator to calculate how many gear inches or whatever you gain - if those numbers are meaningful for you.
I would play around with the website below to get an idea, but then again I like numbers. You would have about an 11% difference between the 25 and the 28. I don't know what that would feel like for you but it seems comparable to the difference between your 17 and 19 so I guess you could imagine that the drop in resistance from 25 to 28 would be about the same "amount" of resistance drop that you would feel from the 17 to 19. Does that make any sense at all?
http://www.sheldonbrown.com/gears/
I live in the mountains, and have tried different rear cassettes - and for me I would say yes - you will appreciate the additional gears - on a long climb if you need a spin break, or on some really steep pitches they just might save your knees. But again - that is a personal choice. Enjoy climbing!:D
I can change out just one chain ring? Wow I learned something new today! If I change out my cassette will I have to change the deurailler (sp?) And chain too?Quote:
Originally Posted by Catriona
Quote:
Originally Posted by VeloMel
Depends on what you have on your bike.
I've been looking into changing the 12 - 25 I have on my Cervelo for an 11 - 32. I can manage a 6 mile 5% average grade with it, as is. But on a longer ride, with multiple climbs and anything more than 5%... my knees scream at me. I need to change my derailleur and my chain to switch my cassette. Currently I have SRAM Force on my bike. I need to move to a mid size derailleur to have room for the larger cassette. So, I'll be putting a mid size SRAM Apex derailleur on.
Veronica
You'd have to check your cranks, but i think probably you can just change the 1 chain ring.Quote:
Originally Posted by VeloMel
If you change out your cassette, you're supposed to get a new chain. Your rear derailleur can probably handle the 11-28 no problem, because my short cage ultegra one did on mine - but there's a slight chance you'll have to get a long cage rear derailleur.
No, I think you have to change the whole cassette but others might know more about that. I was just referring to the fact that what you will really notice is the new 28 teeth cog because the rest of the gearing on the 11x28 will be very similar to your current cassette.Quote:
Originally Posted by VeloMel
For example, your 12x25 cassette is probably 12-13-14-15-16-17-19-21-23-25.
Those numbers represent the teeth on each cog.
When you switch to the 11x28 you might get, lets say:
11-13-15-16-17-19-21-22-25-28
I don't know for sure which 10 cogs you will get (I just guessed at those above) but you as you can see, much of the gearing will be identical to what you already have, what you will really notice is the 28.
Also, looking at Sheldon Brown's site and the gain ratios that different front chain rings and different rear cassettes would produce will show you that all these set ups will have lots of overlaying gears. You just need to figure out which hard gears you need for speed and which light gears you need for climbing based on your experience with hills and your current gearing.
I'm not sure if you would have to change derailleur or chain. I'm not knowledgeable enough.
Since you already have a compact AND a 12-25, I'd say you would be fine on most mountains. If you are going up really steep mountain passes, then you may consider going up to 26 or even 28 - but with a compact crankset you are very unlikely to need it.
I think it really depends on the individual rider, her knees, and where she's riding. My knees really do need a larger cassette - and I have a 34 small chainring. I use a 13-29 (campy) on my bikes that I use in hilly areas and mountains (Colorado). In Florida, my bikes with a standard double with a 12-25 is fine.Quote:
Originally Posted by TxDoc
I am going to make a similiar change from 11-25 to 11-28. You should definitely replace the chain at the same time. The RD depends on compatibility, it has to be able to to carry the chain to the slightly larger cog.
To calculate the ratios, you simply divide the front by the rear. For instances 36/25 = 1.44. If you change only the rear cassette 36/28 = 1.29. The closer you are to 1.0 the easier it will be to pedal. If you only change the front to a34, then 34/25 = 1.36. If you change both then 34/28 = 1.21.
Good luck!!!
Cross chaining like that is a bad habit..... even if you don't hear that nasty grinding noise its hard on the components and makes it more likely you'll drop your chain when you do shift.Quote:
Originally Posted by Catriona
Just to clear up:
Chainrings are the cogs in the front. You can buy and change those individually.
Cassette is the collection of cogs and spacers in the rear. For Shimano cassettes (and I think it's the same with other brands), the larger 3-4 cogs are one piece, and the smaller ones are loose. So you can change the smaller cogs (taller gears) individually, BUT they're not sold individually, so you would have to find a shop or a friend you could swap with, if you wanted custom gearing. Also, not all cogs can necessarily go in all positions on a given cassette.
Going from a 25T rear to 27 makes a huge difference to me on the steeper hills.
Do check your derailleur compatibility, although I think any cage that can accommodate 25T will handle 28? You'll probably need to adjust your B-screw if you make this change.
Also, I haven't noticed any ill effects or increased wear from using the same chain length with both. Technically I should probably be using one more link with the 27 than with the 25, but my long cage derailleur is big enough to accommodate it. If I were going to make a permanent change, or swapping back and forth with a larger gear difference (as I plan to replace my 11-25 with an 11-23 as soon as it wears out), then I would/will have to use two different chains as well. How badly you need to change your chain length probably depends on your chainstay length and derailleur cage size. Park Tool has a couple of methods for determining chain length.
If you're making a permanent gearing change but decide that you can keep your old chain until it wears out, then don't forget to make your new chain longer when you do replace it. If it were me, I'd put a note on my chain tool so I wouldn't forget. ;)
I have a Specialized Ruby with compact 50-34 chainrings. It had a 12-27 rear cassette. This was not working for me in the Santa Cruz Mountains. There are places with over 10% grades. I changed the rear cassette to a 12-32 IRD (since Shimano does not make a wide range 10 speed cassette). I changed the 105 short cage derailleur to a 105 long cage derailleur and a new chain. Now the bike can do hills much better. Even with this setup, I see even more experienced riders with even lower gears than I now have. I can see how much more they spin than I do. Many of them have triples (or mountain bike triples) with 11-34 cassettes. So, if you are going to make some changes, I would recommend going even further than you are planning since the expense would probably by similar anyway. Of course, it depends how steep your hills are.
VeloMel, where do you ride now? What mountains do you plan to ride?
It's the grade, not the elevation. You'd probably need shorter gearing for most of the Appalachians, even the foothills, than you do for the Rockies.
Terrain is something we can tell you about, as is how to change gearing. What your legs are happy with is something that only you know. Do you like to power up hills, or sit and spin? What about on the descents (I see you're thinking about an 11T top gear)? Are you using all the gears you have now?