Can a 12-25 cogset be changed to 12-27 easily?

I discovered yesterday riding out in Shawnee Mission, KS that even in my granny up front, the 25 cog in back was quickly reached, and I was really struggling on the surprisingly large hills (our first ride out that way) in my very lowest gear on my new-to-me Trek Pilot. I'm used to riding my Bike Friday, which was built for touring with mountain gearing (12-34) in back plus the smaller wheels, giving a tiny low gear that can get me up just about anything other than straight vertical.

The Terry Isis I rode back in 2003 had 12-27 in back, so I am wondering if I could have the 25-tooth cog changed to a 27t on the Pilot with no derailleur change, anyone know? I know that only gives me one more gear, but that's exactly what I needed yesterday!

Also, at the same time, I'd like to have the "cheater brakes" (don't know what they're officially called) removed from the handlebars. I never use them, and the bars are narrow enough (36cm) that I really can't ride on the top at all with those brakes installed.

Is this an easy DIY or something I should have the LBS do?

Thanks!

What rear derailleur do you have? The stock long cage Ultegra? If so, it's probably the same one I have (my bike is '07 vintage, not sure the model number), and all it takes is a little tweak of the B-screw and I'm set. The 27T cog makes all the difference in the world on those long hilly steep rides. I don't even have to readjust my cable, though YMMV on that.

(But, plan on replacing the whole cassette. You *might* be able to find the right cogs at a swapmeet, but Shimano doesn't sell individual cogs, or actually, the lower gears come fused together anyway.) They're easily swapped out so if your 12-25 isn't worn out, you can keep it for your flatter rides.

Can't help you on the suicide brakes. Were they added on to the bike? Trek's archive says your bike should've come with R700 brifters (also same as mine).

I'd have the shop do the brakes. That's something I'm not comfortable messing around with. (Would probably also require re-cabling.)

You should be able to swap the cassette out relatively easily--but I agree with Oak, you're probably going to have to replace the whole cassette.

Thanks for your input, ladies. I'll have to check on the derailleur.

The cheater/suicide brakes were original equipment on this bike, along with the R700 Brifters. I suspect the bike was marketed towards women who hadn't ridden in a long time and thus wanted a more relaxed geometry, so perhaps Trek thought the extra brakes would help them feel more comfortable...I dunno. But I'm used to the regular brifters and don't even remember the others being on there except when I want to ride on the tops and they are there taking up space! :D

Following up on my own post...looks like 12-27 cassettes are only available in 9-speed. I need 10-speed. Ultegra CS-6700 comes in an 11-28 or 12-30. Looking on ebay, appears I'll have to pay at least $80 (probably more, with shop markup) to get that, excluding labor; and then whatever they'd charge to redo the brakes. And I would probably need a longer chain and possible a new derailleur as well, if my bike doesn't use the long cage. One thing leads to another, I guess!

I'll have to wait to decide when/if to spend the money -- was hoping not to have to put a lot more money into bikes for awhile as I've just bought two bikes in the past half year, plus some gear, tires, etc.

The 105 cassette comes in 12-27, 10-speed. You don't mind a few extra grams, do you? I have never noticed a difference in shifting between Ultegra and 105 cassettes. Plus, it's cheaper! (And your bike specs with a 105 cassette originally, anyway.)

If you've got a triple up front, your derailleur is big enough for the 27. Going to the 11-28 Ultegra cassette *might* be an issue with the older derailleur, but it appears you and I have the same drivetrain, and the 12-27, 105 cassette is not a problem. I don't even swap the chain, it's close enough within a link, though if you were going to wait until you replace your chain anyway, you might make it a link or two longer with the 27T cog.

Really, swapping cassettes is no big deal. Fifteen minutes' work. No idea what a shop might charge, but it really shouldn't be much. A cassette tool and chain whip are good things to have around anyway.

Sizing and cutting brake housing, OTOH, is a PITA, and so is re-taping handlebars IMO, and I'd happily let the shop do that. :D

Ah, thanks, Oak! That is all very reassuring. Yes, I have a triple up front (that's why it's so embarrassing that I maxxed out my gears with the granny yesterday! But let me tell you, this part of Kansas is NOT flat at all!)

I may just be able to do this after all...actually, my DH has replaced cogsets before, but I am not sure he brought all his bike tools with us to Kansas. If not, we would just have the shop do it. I will talk to them the next time we're in to get an estimate of costs. I'd love to stay with Ultegra since I've already been adding weight to the bike with my new Mirrcycle road mirror and all the crap I carry in my seat bag, but if it makes a sizeable difference in cost, I'll go with 105.

Do it, Emily. You won't be disappointed. I have 105 on my custom, because it was the only thing that works with the newer short reach brifters. I don't notice any difference between that and the Ultegra on my other bike. I have a 34 on this bike, as it's a compact and my go to bike for really big climbing rides.
Oh, and my bike with the triple? I've gone from a 25 to a 27 and now to a 28. Don't ask me about the mechanics, but DH did it all himself.

Hi emily. Its trivial, but you do need to swap out the entire cassette. If you have a RD than can handle a 12-25 I would be very surprised if it can't handle a 12-27. You can do it yourself very easily, I do it all the time (but u do need a special tool and a chain whip). But yes, you probably do need either a longer chain, or to put back in a few links that you probably removed when the chain was first installed. This too you can do yourself. Depending on what RD you have, you could possibly accomadate a 12-28, which if the 25 is giving your trouble is probably worthwhile. If you need to change the RD, you could install a mountain RD and then use an 11/34 like on your friday. This is what i have with a compact double on my travel bike, and a 12/27 on my racing bike. I am surprised the trek pilot fits you. I would have thought it had too steep a seat tube angle for your body if I remember correctly (don't you have proportionally long femurs?). I ride a cervelo RS 48cm now w 650c wheels, which fits me like a dream (my racing bike). My terry isis 19" I had converted to a travel bike with s/s couplers and that works great too. My 17.5" terry isis was really too small for me and is now being ridden by my son's girlfriend.

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Originally Posted by emily_in_nc

I'd love to stay with Ultegra since I've already been adding weight to the bike with my new Mirrcycle road mirror and all the crap I carry in my seat bag, but if it makes a sizeable difference in cost, I'll go with 105.

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Emily, according to specs there is only a 37g difference between your 12 25 and the 105 12 27. You might want to look at the price difference between an ultegra 11 28 and the 105 12 27, a quick look at a few places online shows it as 20+/-......in any case as Oak wrote you probably won't notice a difference in shifting between the two. I talked to a friend and she said removing your cheater brakes should just be a cable and housing change.

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Originally Posted by rebeccaC

just a cable and housing change.

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YMMV, but IME there's not much "just" about replacing cable housing.

When you cut cable housing you have to (1) make sure you don't crimp the housing when you cut it, (2) use a smooth punch to open up the hole when you inevitably DO crimp the housing, and (3) file all the burrs off the cut end(s) so they don't catch and fray your cable.

A good housing cutter that will HELP cut without crimping, but not guarantee it, is like $50 (more than the cassette tool and chain whip put together), and will get very little use unless you've got a stable of bikes that all get ridden frequently. You will also want a small round file to get the inside surface, plus ideally a flat one also to get the outside and the edge most efficiently, though you can do it all with the round one - might or might not be something already in your toolbox.

Then you have to re-tape your handlebars. Ugh. I know some people here can do that all day, but I don't get enough practice, and I always wind up re-doing it six or seven times a side before I can get it smooth, and there's usually still a lump at the bar end. Actually the last time the shop did it for me, the mechanic's 11-year-old daughter did it flawlessly while I watched. SHE gets to practice on other people's bikes. :p

Sizing and routing the housing isn't a big deal - important for safety, but easy - but cutting it, I still say is a PITA and well worth whatever the shop charges to do it, which is usually minimal.

Thanks for all the feedback, ladies. I would definitely have the shop do the brake removal if I decide to do that. It's not worth the risk of screwing that up nor paying for a special tool.

As for the cassette change, I have no problem going with 105 but am also inclined to go with the 12-28 Ultegra instead, all other things being equal, as that lower gear can only help, and it's well worth $20 extra to me if that's all it is. But if I would have to change the derailleur for a 28 but not a 27, then I'd go with the 105 12-27 instead to keep it simpler and less expensive. I still haven't gotten around to asking DH if he brought his tools to change cassettes with us here; I know he has done it in the past as I bought a new cassette for my Titus in the past, and he changed it.

I don't have any extra chain links as I bought this bike on Ebay so did not shorten the chain, so that will be a factor as well. Need to discuss all this with DH as he does most of the bike work in this househould.

[Trisk, as an aside, the Pilot fits me extremely well! My Aegis Swift had a 75 degree ST, and I did fine with that from a fit perspective. The problem with that bike was because it had a flat top tube, I had zero standover -- I mean nothing, the TT was jammed up into my crotch. And even with the 650c wheels, since the TT was so short, I had lots of toe overlap. The Pilot has the sloping top tube, so the 47cm size gives me lots of standover and no toe overlap (or if there is any, it's extremely slight). And it came with the setback seatpost I need. I absolutely love the bike (and it was a great deal on ebay for full carbon/Ultegra, which is why I decided to take the risk of getting it), but the gearing is not as low as what I'm used to, and I don't have my Friday here to ride the steep hills. I could ride my MTB, but with Barry on his Trek, I'd be eating his dust even more than I do on a road bike! I *thought* Kansas was flat, but not this part of it!]

Thanks again! I'll follow up and let everyone know what I end up doing.

I have an 11-28 105 cassette on the rear (10 speed). That is another option to consider.

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Originally Posted by goldfinch

I have an 11-28 105 cassette on the rear (10 speed). That is another option to consider.

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Yes, I actually misspoke above, goldfinch. The Ultegra 10 speed cassettes are 11-28 or 12-30.

I asked DH, and he does not have a cassette tool or chain whip here, so when I get a chance to take the bike in, I will likely just ask the shop for an estimate to do the work and provide the cassette. From the research I've done, if I have the medium-cage rear derailleur, I could use the 12-30, which I'd prefer as it would give me a 27 and 30t ring, two additional gears. This would be great when I'm riding in the middle chainring in front, which is most of the time. I hit that 25t cog far too early since I'm used to bikes with more easy gears and am a spinner, not a masher. I'd need my granny chainring a lot less with a 12-30 than with a 12-25. But I'll settle for an 11-28 if that's all that will work without a derailleur change. I looked at my derailleur, and comparing it to photos on ebay, I think it's gotta be at least a medium cage, if not a long. It looks much longer than the short-cage.

We shall see!

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Originally Posted by OakLeaf

YMMV, but IME there's not much "just" about replacing cable housing.

When you cut cable housing you have to (1) make sure you don't crimp the housing when you cut it, (2) use a smooth punch to open up the hole when you inevitably DO crimp the housing, and (3) file all the burrs off the cut end(s) so they don't catch and fray your cable.

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Oak, I use a dremel with a cutoff wheel on both cable and housing. The dremel also has a thousand other uses unlike a park, felco, pedros etc. cutter. Eye protection, a steady hand, some tape on the cable and a piece of old cable in the housing where you cut makes it fast and easy to get a clean square cut.