Can I change my rear cassette to get lower gearing?

[emily_in_nc]

Hi,

Tech. question here. My Trek Pilot currently has a 12-25 cassette (10 speed) in back with Ultegra derailleur. It's a triple in front (I think it's 30/42/52 but haven't actually counted). In lieu of springing for a new road bike right now, I would really like to change out the cassette for a 12-28, which I assume would be pretty easy. However, I'd love to go even lower (12-30) if my derailleur could handle it. I'm pretty sure it's a medium cage simply because the bike has a triple crank (and from its appearance).

What's the upper limit on what rear cassette I can put on with my current setup without having to go to a long-cage derailleur?

Thanks very much in advance!

[ny biker]

I made a similar change to the cassette for my road bike last year:

http://forums.teamestrogen.com/showthread.php?t=55780

The short version is: I went from 11/26 to 11/32. I did have to change the derailleur, from short cage to mid-cage so you might be okay with the one you currently have.

At the time one of my friends encouraged me to get cassette with a 36 cog. I think that would have necessitated a long-cage derailleur but am not sure.

My components are all SRAM, and IIRC I was able to find good information about compatibility with cassettes and derailleurs on their website.

p.s. I am SO happy that I made these changes. Totally worth it.

[north woods gal]

I agree with NY that changing from a 12-25 to a 12-28 is probably doable without a derailleur change, but, to be honest, that's not much of a change. Personally, if you're going down this road, I'd go all the way to at least a 30 and a 32 or 34 is even better and Shimano does make a 10 speed cassette in those. Might have to change out your derailleur, but that's still a lot cheaper than buying a new bike. For sure, though, find a bike shop with a mechanic that knows the ropes on Shimano.

[ny biker]

Another thing to look at is the specific sizes of all the cogs on your current cassette vs whatever you're thinking of replacing it with, to see what you will lose when you add 28 and/or others. I actually had wanted to go with a 12/32 because I really don't use the 11 cog all that much, but due to a failure to communicate with the LBS I got the 11/32 instead, which meant I lost one around 15-17, I think.

As is often the case, Sheldon' Brown's gear calculator can help you figure out the before and after scenarios. And I think the number of teeth should be stamped on each of the current cogs, though I needed a good light and reading glasses to read mine.

I just looked up my old road bike, which had a triple (vs the current one which has a compact double).

Chain rings: Shimano 105 52/42/30
Cassette: Shimano HG-50 12-25, 9spd

I ran Sheldon's calculator when I bought the current bike to compare the lowest gears for the old and new bikes, and as I recall the 34-28 combination on the new one was about the same gear inches as the 30-25 combination on the old one. Either was ok for the short steep hills around here, and adding the 32 cog made them significantly less difficult.

I will look to see if I still have the emails that some of my friends sent last year with details on their touring bike gears, which they use for riding up mountains.

[Crankin]

I am not an expert, but I made the change you are talking about on my last bike, with not a lot of work, according to DH. My new (not so new now) Trek came with a compact/11/32, which I really like, but is missing the 15 cog, I was always in, on my triple. I got used to it, but I change gears a lot more. My custom Guru was bought before they had lower gears for road bikes. I have a long cage, mountain bike derailleur with an 11/34 on my compact double.
I am hoping to upgrade my Trek to the 34 in the next year or 2.

[emily_in_nc]

Thanks all!

I should have mentioned that my setup is all Shimano. I don't even know what SRAM looks like...lol!

I am not planning to change to a compact double up front since that would be a much more significant change. I just want to keep my triple and see what I can do in the back. I'll take it by the LBS and see what they have to say. Even one more low gear would be helpful, but if I could get the 30 without changing the rear derailleur, I'd do that in a minute. I can probably live without a 32 or 34 in back as I do have a mountain bike and Bike Friday with mountain gearing in back, so I can always ride one of those bikes if I think I'll be climbing huge mountains.

As it is now, I feel like I run out of gears on the middle ring quicker than I'd like, and I hate having to go to my granny chainring. If I had one more gear to shift to, I could stay in the middle ring more and only rarely have to go to my granny on my road bike, which is mostly what I'm looking for. And yes, occasionally I would like one more gear even in my granny chainring on that bike, but not often.

I'll let you know how it turns out!

[Crankin]

Emily, unless you are having trouble shifting to your granny gear, then what is your reason for not using it? Is it because of that out of date mind set mumbo jumbo about it being for grannies? When I teach a basic bike class, the first thing I ask is what is your most important gear? And the answer is your lowest one! Seriously, use the gears you have. This does not in any way rule out switching out your cassette. My bike that I changed from a 25 to 28 was a triple and I used the granny gear a lot on bigger climbs. I had some smaller hills where I stayed in the middle ring, but basically it hurt my knees and slowed my speed to do so on anything over a 3-5% grade. This is especially important as we age. The goal is to keep riding.
I changed my cassette from a 25 to a 27, then to a 28 on my triple. I sold this bike to a woman who is a much stronger rider than me and she has no trouble using the granny on climbs. I would have bought a triple again when I bought my Silque, but they don't make them anymore.

[north woods gal]

For sure, the industry is moving away from triples on road bikes and MTBs. Something to think about if you like that triple, but decide to go with a new bike. MTBs, these days, are even moving away from doubles to 1x systems with only one chainring in front and no front derailleur.

I use compact doubles on my two road bikes and for our hills, they do just fine. Like you, Emily, I sometimes get a little stubborn about dropping down to the bottom ring when I should, just so I can avoid shifting back up to the big ring once I've crested the hill. Actually pretty silly when I think about it, not to mention being less than prudent at my age. I do understand, though.

[ny biker]

When I had the road bike with a triple, I only used the small chain ring for the granny gear on steep hills. Otherwise I stayed in the middle ring. Though in part that was probably because the Tiagra derailleur was not great and I often had shifting problems in front (until finally the derailleur broke from being adjusted so much and the replaced it with an Ultegra, after that the shifting was fine but by then my habits were set).

[emily_in_nc]

Emily, unless you are having trouble shifting to your granny gear, then what is your reason for not using it? Is it because of that out of date mind set mumbo jumbo about it being for grannies?

No, it's really not that. It's more just the logistics. Usually unless I realize ahead of time that I'm approaching a hill that is absolutely going to require it, I'm already in the easiest gear in back in my middle ring, and if I start thinking "Damn, I really wish I could shift one more time..." it's a pain because I have to upshift in the back a gear or two before I shift in the front to the granny ring. It's not always very successful to shift from the largest cog/middle ring right to the granny (easy to drop the chain). So, certain hills, I know right away are going to require the granny, I will shift well ahead of time, and I'm fine, but all too often it seems I wind up in the 42-25 combination and just wish I had one more gear since I am *so close* to being at the top of the hill. Usually in those cases, I get out of the saddle and power over (and my knees have been fine so far, knock wood!) but sometimes I'm getting tired and wish I could just stay seated.

It just seems so much easier to stay in the middle ring most of the time, and if I just had one more gear (or two, even better!) I could avoid the hassle of shifting to the granny (and then back, almost immediately afterwards, to the middle ring). I do use all my rings up front as needed, but I am not crazy about it. I'd prefer to stay in the middle and have a wide range of gears in the back...just keeping it simple.

Perhaps I am just a little lazy? But it's really more than that as with some of the places we ride in true mountains, I do need a lower gear in back even in the granny up front, and maybe I have taken my Trek so I have some hope of staying with DH. I have my Bike Friday with lower gearing, but it's a slower bike overall.

I do know that most newer bikes use the compact double, and in fact, I used to have a lovely, racy Aegis Swift with 650c wheels and a 34-50 compact double that I adored. I built that one up myself with Campy Chorus in 2004, and it was my splurge bike. The rear cog was a luscious 13-29, and I could handle anything with that combo. Of course, I was only 43 years old at the time. I ended up selling the bike eventually because I had my bad accident on it and just couldn't do fast road rides for a long, long time after that for physical and emotional reasons, and just the sight of the bike was rather upsetting to me. But that gear combination was lovely. With the 650c wheels, the gears were even a bit lower than they'd be on a 700c bike, like my current Trek Pilot.

[emily_in_nc]

MTBs, these days, are even moving away from doubles to 1x systems with only one chainring in front and no front derailleur.

Interesting! I love that idea. It surely would simplify things. When I was riding hilly MTB trails frequently I found I stayed in my inner/granny ring on my MTB most of the time just so I could avoid shifting errors when the terrain got crazy and ever-changing. I would much rather coast downhill but be able to tackle pretty much anything uphill than get stuck unable to shift fast enough to handle a sudden steep climb after a descent.

[Crankin]

So, one of the things I usually teach people, that is as you approach a hill, especially one you don't "know," is to gear *up* 1-2 gears, or even 3, on the rear. You will slow, but then, you are in a position to gear down on the front, asap. You are really cross chaining if you are in the lowest cog and in the middle ring. When you feel you need to get down to the lowest cog in the middle ring, that's your cue to stay in a bigger cog and you get into the granny then.
Another thing is, if you are dropping your chain, check your limiter screw on the derailleur (your DH can probably do this). But dropping the chain is usually a signal you are in a cross chained combo.

[ny biker]

I have never learned the "right way" to shift. With the triple, I would go up hills in the middle chain ring and whatever cog worked. If I shifted down to the easiest cog and needed an easier gear, I shifted to the small chain ring without changing anything in back. I don't shift up when I stand on the pedals, either.

[Crankin]

I never stand, except to stretch. It reduces my speed so much and hurts so much, I have developed into a "spinner." I may be going 3 mph, but I can stay seated on almost anything. I say almost, because there have been two 17-20% grade climbs in the Berkshires that had me off my bike. It still kills me I had to walk, as I have some pride. But, this is just a style preference. I know exactly when my DH will stand on a hard climb (he mostly spins, too) but it's like I cannot get myself up.
I find with beginning riders, shifting is often not intuitive. I am a spazz, but this may be the only thing about riding that I learned correctly. Sometimes on our New Members' Ride or bike rally, I coach people through on little hills.

[Jean_TZ]

Hi,

Tech. question here. My Trek Pilot currently has a 12-25 cassette (10 speed) in back with Ultegra derailleur. It's a triple in front (I think it's 30/42/52 but haven't actually counted). In lieu of springing for a new road bike right now, I would really like to change out the cassette for a 12-28, which I assume would be pretty easy. However, I'd love to go even lower (12-30) if my derailleur could handle it. I'm pretty sure it's a medium cage simply because the bike has a triple crank (and from its appearance).

What's the upper limit on what rear cassette I can put on with my current setup without having to go to a long-cage derailleur?

Thanks very much in advance!

According to the Shimano specs for the Ultegra 10-speed rear derailleur (aka Ultegra 6700), your bike probably has the GS shifter (designed for road triples). The maximum capacity is 39 teeth and the maximum rear cog (which is kind of dependent on the B-screw adjustment) is ~28 teeth.

Using the capacity spec, you could use cassette with 17 to 18 tooth difference between the largest cog and the smallest cog (max rear tooth difference = total capacity – front tooth difference).

Since you want lower gearing, using a 12 to 29 (or 12 to 30) cogset would be within the limits. Shimano does make a 12-30 10-speed cassette. This would give you one step lower gearing using the “30 tooth front x 30 tooth rear” combo. This ought to be low enough for road riding.

If you do an internet search, you’ll find that some people have successfully exceeded Shimano’s capacity spec.

P.S. If you decide to replace you current cassette, you should also get a new chain.