Putting Road gear on to MTB

Hello all,

while I think of myself as a roadie I am forced to commute to work on my
trusty old MTB as I feel my road bike would be too attractive a target
in the local car park.

While this works well I am reasonably fit and find that I only ever use
the top 3 gears despite some good stiff climbs on my route.

My MTB drive train is now pretty worn and a recent spill has damaged my
front mech so almost all needs replacing.

My local dealer says that I could actually put a front dual mech, double
front chainring (road), new chain and new rear sprocket (keeping rear
mech as is).

Has anyone else done this ?

It seems like the logical move but i'd welcome the thoughts of the group
on this.

Cheers

TJ

tj wrote:

: My local dealer says that I could actually put a front dual mech, double
: front chainring (road), new chain and new rear sprocket (keeping rear
: mech as is).

You could, but it might be an expensive way of doing things.

And though we always say this, I'd wonder what sort of cadence (pedal
rotations) you are keeping if you're only using the top couple of
gears even uphill.

Arthur

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Arthur Clune wrote:
tj wrote:

: My local dealer says that I could actually put a front dual mech, double
: front chainring (road), new chain and new rear sprocket (keeping rear
: mech as is).

You could, but it might be an expensive way of doing things.

And though we always say this, I'd wonder what sort of cadence (pedal
rotations) you are keeping if you're only using the top couple of
gears even uphill.

The big ring could be a 42 and the smallest rear cog a 14.. And he
could live in Cambridge or Norfolk where the hills are marginally
larger than the camber in the road..

Everyones definition of a hill is a bit different.. (Do I feel the
ghost of an old thread looming?)

...d

And though we always say this,

True, but as I've pointed out before, a few years ago a great many
mountain-style bikes were sold with ridiculously low top gears. Eg a
"compact" chainset with a 14-whatever cassette.

I agree, it's probably an expensive way of doing things. The OP needs
to post details of what he's got already, but I would have thought
he'll probably need to change the chain and cassette so will be able to
put on a cassette with 11-tooth smallest ring. Then if he's still
under-geared he could (later) change the largest chainring, but he
probably won't need to.

As another suggestion, the MTB-derived hybrid I commute on (rather than
the MTB I got very muddy on yesterday) doesn't have a front mech at
all. It just has a simple single front 42T chainring.

It's as on the one he
URL:http://www.edinburghbicycle.com/news/reviews/edin_courier.html

Cheers
Stross

iakobski wrote:

And though we always say this,


True, but as I've pointed out before, a few years ago a great many
mountain-style bikes were sold with ridiculously low top gears. Eg a
"compact" chainset with a 14-whatever cassette.

When has such a thing ever been available?

James
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tj wrote:
While this works well I am reasonably fit and find that I only ever use
the top 3 gears despite some good stiff climbs on my route.

If you don't have to change gear, they aren't climbs - merely
undulations. ;-)

Do you ever find yourself "spinning out"? (ie not being able to pedal
fast enough to make any difference to your speed)

If not, then I wouldn't worry too much about giving your bike higher
gears - if your problem is not being able to go as fast as you would
like, you might find you will get more benefit by spending your money
on slicker, narrower, higher pressure tyres (presuming your mountain
bike currently has off-road tyres) which will give you extra speed for
the same level of effort.

If spinning out /is/ a problem, a larger "roadie" chainring will
certainly help, especially if you are replacing the parts anyway. But
like Arthur says, it will be expensive, so don't rush into it.

If you only spin out on downhill stretches, I would say it's not worth
getting a larger chainring. Personally, I'm becoming increasingly of
the opinion that variable gearing is over-rated. I have mostly given up
changing gear on my commute (even when I do the long version of my
commute - 17 miles - as I did this morning) and tend to stick to a
42*16, which allows me to maintain a comfortable cadence (usually
somewhere in the range 80-100 rpm), isn't too high to comfortably pull
away from lights and isn't too low to stop me going fast when I need a
burst of speed.

I rarely change down, even on the "climbs", and usually only change up
for the really fast stretches (on the flat, with a tailwind, drafting a
large vehicle, etc) but if I didn't have the larger gear, I wouldn't
miss it.

d.

David Martin wrote:
The big ring could be a 42 and the smallest rear cog a 14.. And he
could live in Cambridge or Norfolk where the hills are marginally
larger than the camber in the road..

I do most of my commuting in 42*16, and my commute (central London) is
not exactly mountainous in its profile, yet I don't often find myself
spinning out. 42*14 should be plenty big enough for most circumstances.
The OP describes himself as "reasonably fit", not Lance bloody
Armstrong!

Everyones definition of a hill is a bit different.. (Do I feel the
ghost of an old thread looming?)

Fair enough... up to a point. You need to have a reasonable cut-off
point so the term retains some semblance of meaning - what some people
call hills would barely register as an upward gradient for many of us
in this forum. Are we to allow those slight slopes to be described with
the same word we use for an Alpine pass?

d.

On Mon, 06 Jun 2005 12:52:07 GMT, tj wrote:


while I think of myself as a roadie I am forced to commute to work on my
trusty old MTB as I feel my road bike would be too attractive a target
in the local car park.

While this works well I am reasonably fit and find that I only ever use
the top 3 gears despite some good stiff climbs on my route.

My MTB drive train is now pretty worn and a recent spill has damaged my
front mech so almost all needs replacing.

My local dealer says that I could actually put a front dual mech, double
front chainring (road), new chain and new rear sprocket (keeping rear
mech as is).

Why bother with a double set up at all? If you only use 3 gears now it
sounds like a single ring Courier type set up might suit you, and your
commute, very well.

Keep current chainset but remove all three chainrings and put them in
your bits box for later. Buy a larger chainring and mount it in the
middle ring position on the spider, you'll probably need some shorter
chainring bolts (or spacing washers) for that. Ditch the damaged front
mech and cable, and, if you want, remove the front shifter from the
handlebars.

Lighter bike, simpler bike, faster bike.

Cheap too. One chainring and a set of bolts, job done.

If you go this route you may have to modify your chainset slightly. My
MTB spider had to be filed down a little to accept an outer ring in
the middle position, it was only a ten minute job though.

The only other potential problem will be how much clearance your frame
has for a larger ring in the middle, there will be a limit before it
fouls the chainstay.

If you wanted to spend a bit more money you could also put on a more
road oriented rear cassette, for closer ratios and perhaps a bigger
gear, depending on what's already at the back.


"Bob"

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iakobski wrote:
True, but as I've pointed out before, a few years ago a great many
mountain-style bikes were sold with ridiculously low top gears. Eg a
"compact" chainset with a 14-whatever cassette.

I've just done the maths... (well, I got an online calculator to do the
maths for me)

For a bike with 26" wheels and a "ridiculously low" top gear of 42*14,
you get:
18.6mph @ 80rpm
20.9mph @ 90rpm
23.2mph @ 100rpm

I'd be really surprised if too-low gearing is the root of the OP's
problem, unless his "big" chainring is very, very tiny.

d.