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Replacing rear cogs in order to go up steep hills
Last year I purchased a Trek Pilot 5.0 wsd for my wife. I asked the bike shop to change the gearing so the bike would be easier for her to go up steep hills. They changed the rear cog (I believe) but she still has trouble on the steep hills, so I want to try to change out the cassette myself with my very marginal skills. The chainrings are 28-39-52 and the cogs are currently 12-13-14-15-17-19-21-24-27. I am looking on-line at a Shimano XT M770 9-Speed Cassette. Would that work? I am also wondering about changing the 52 chainring to something smaller. She is not interested in speed, but really wants to get up those hills. I wish I would have better understood gear inches when I bought the bike! Any advice would be greatly appreciated.
You can change to a, 12-32, providing the shifting will work as thats a big jump, and a maybe a longer chain, or you can designate your small crank chain ring for climbing by using a 24T sprocket.

I'd go with the small chain ring.
Never Give Up!!!
First thing to watch out for.
If you change the cassette to larger sprockets you may have to also change the rear dérailleur.
We need to know the model of the RD to advise.

From the sound of the sizes of the chainset rings it is already limited to the minimum size of 28T for the small ring and 39 for the middle.
You could change the chainset for a smaller range one - such as 46-36-24.
Any smaller than this and you may have to also change the front dérailleur. Again depends on your current FD.

You could even opt for a 44-32-22 (MTB) but this would definitely require a new FD & possibly a bottom bracket.
Ride hard or ride home alone!
If she wants to go up steep hills the I would put on the 44,32,22 crank set and go with a rear cassette with 11,34 on it but you will have to change a few parts to make this work out but to me it would be worth it. I did it to my LHT but thats me. You will need to change out the FD and the rear dérailleur as well and you will have to reset the front FD but its not hard to do Alex has the videos here to help you on this. Good luck and let us know what you did.
My dad always told me a Sledge a matic can fix any thing.
Thank you, everyone, for your comments and advice. I am a bit overwhelmed by the prospect of changing cogs, chainrings and front and rear derailleurs. I am willing to learn and develop new maintenance skills, but where do I go to understand what combination of gears and derailleurs (and chains) would work well together? I am inclined to try this in steps, to see if I can create more hill power with relatively simple changes. I could always go for the Sledge-O-Matic approach later! By the way, I looked at my rear derailleur and see no model markings...only Shimano Ultegra. Is there a super-secret, double probation location for model markings?
No need for markings.
The Ultegra is a "road" range of Shimano.
Rear road mech's have a large sprocket limit of 27T (you can get away with a 28T though).
So basically you are stuck with the 12-27 cassette unless you use one of the MTB range of dérailleurs. Any will do such as Deore, LX, XT suitable for 9 speed. This will still match your STI shifter and you can then go to a larger rear sprocket of 30, 32 or 34 teeth. Shimano even do a 12/36 now but I have not heard of anyone using these yet.

For the front you will have to change the whole chainset if you want smaller rings. The mounting holes of your chainrings will not allow any smaller rings than you currently have.
If you study the small chainring you will see that the 5 (?) mounting bolts are close to the teeth of the ring. The same goes for the middle ring (39), much smaller and the chain will contact the mounting bolts.
Ride hard or ride home alone!
I am embarrassed to admit this but upon further inspection of my cassette I counted 10 cogs. Somehow I missed the 16T cog.
Hi I looked up your bike, very nice with carbon frame road bike. So as a first time mechanical project on this expensive bike with a fragile frame I suggest you research well and maybe get your local bike shop to help.
Here are some links to great gearing info, and how to measure your crank to determine what drive chainset will fit.

The 46/36/24 sounds like a good combo, you may even be able to get the front deraileur to work with that.




Never Give Up!!!
I sent emails to both peterwhitecycles and harris cycles to get more input. I didn't have a response from peterwhitecycles but did have response from harris. Their tech recommended this as possibility:

First item: 11-34 10 speed cassette for Shimano Hubs (CSX831) $159.95.
Second Item: Shimano Deore SGS Rear Derailleur Model RD-M590 $54.95.
Third item: Wippermann ConneX 10-speed Chain (CH1437) $44.95.

I am seriously thinking of going with this unless I hear that this would not work with the Trek Pilot. I am assuming I could still use the Ultegra front derailleur as is. As usual, any comments are greatly appreciated.
OR look at Craigs list or ebay and get a nicely set up vintage mountain or cross bike for less, save the high end road bike for level terrain and work your way up to hills.
Than you will have two bikes.
Never Give Up!!!
BTW if you absolutely positively are committed to that bike than the 28T & 39T front rings with the 11-34 rear are a good MTB ratio gearing on the lower end. The 11 is a bit smaller than I would use, but maybe whats out there.
Never Give Up!!!

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