Daniel B. Martin said:I have a new road bike, a Specialized Sequoia. It has:
Crankset Sugino Comp
Chainwheel 52/42/30
Front Derailleur Shimano Sora
Rear Derailleur Shimano Tiagra
Rear Cogs Shimano HG-50, 8-speed: 12-25
Shifters Shimano Sora STI
I like the bike but find it necessary to change the gearing.
I need really low gears for my slow-up-the-hills riding style.
Please advise what I should change. If possible, give specific
make/model of parts. I hope to keep the cost of these changes
reasonable by replacing the cassette and rear derailleur *or* the
crankset and front derailleur, but will change both if necessary.
Is it realistic to install a 9-speed cassette (with derailleur and
chain) and expect it to work right with the factory crankset and derailleur?
Before anyone says "Dude, if you need low gears you should have
bought a mountain bike" please understand this: the bike was a gift,
and you don't look a gift bike in the gears!
I'd put on an 8 speed HG-30 11-32 cassette (8 euros 50 at Rose) and see
where that'd get me, and if the derailleur *really* couldn't handle the 32
I'd put on a E9,90 Acera or E18.50 Alivio derailer. Don't be too snobbish
for the Acera, I'd say, especially with Sora shifters on the bike to start
with (which are that same quality level in Road rather than MTB).
You could (again, at the expense of some compromised shifting,
particularly under load, due to the ramps not lining up any more) also use
some cogs from the 11-32 in combo with some from your 12-25 to make a
cassette that's even better for you (I think HG50 and HG30 8s are almost
certainly all loose cogs, possibly, after removing a rivet or three).
12-13-15-17-19-21-23-25 and
11-13-15-18-21-24-28-32
Okay, you probably don't need the 11 since you want lower gears rather
than higher, and depending on whether you can get the 32 to work you might
want to go: 12-13-15-18-21-24-28-32 or 12-13-15-18-21-23-25-28 -- the
first one is just replacing the starting 11 with the 12, which should
compromise shifting not at all, and might be necessary in any case if the
cassette body is not a Compact type.
I suspect that the rear der actually gets pretty close to the 32 -- both
long and short cage current Tiagra derailers are conservatively specced
at a max cog size of 27, with a total capacity of 29 and 37 respectively,
and since it's a triple it's probably the long cage one. At the expense of
not quite as good shifting, you can probably make the 27 versus 32
disconnect work, and the 43 verus 37 teeth capacity difference is only
really relevant in small/small which you shouldn't be riding anyway.
Going to 9s is not really cheap or cheerful and should probably be avoided
(unless you're doing the entire bike up just keeping the frame), and
getting a new crank is something that I think is probably not necessary.
Although even that can be done rather cheaply, an Alivio crank is in the
20s and you can probably reuse the existing BB and with a little bit of
luck the existing front derailer.
Jasper
