Taller gears on a MTB?

"David S. Maddison" <[email hidden]> wrote in
message

Quoted message said:

I have a friend who feels that he wants taller gears on his MTB, the
problem being that he is pedalling as fast as he can at 60kph. I said
that MTBs are optimised for speeds less than that and if he wants
gearing to go to faster speeds he should go for a road bike.

He might be able to pedal faster than that with training?
Find out what his cadence is at 60kph.. I'm sure it's pretty hard
to really spin out in mtb top gear?

Quoted message said:

Is there any reasonable compromise? Is it possible to have a good low
range and a gear or two for fast speeds such as 60-80 kph+?

With a standard 42-32-22 set of chainrings, he could fit a
road cassette and still have a fairly good range of gears.
I used this setup briefly and from memory it's quite good for
a commuting setup. Assuming he has a 12T or 13T cog on
the rear, going to a 21-11 or 23-11 cassette should give
him a bit more speed in the top end. Looking at Sheldon's
chart, it seems some of the mtb cassettes go down to 11
teeth too?
Meh! Tell him to pedal faster! ;-)

http://www.sheldonbrown.com/k7.html
http://www.sheldonbrown.com/gears/

Quoted message said:

BTW, in case you are wondering, we are talking about down-hill or wind
assisted speeds :-)

What, he's not doing 60kph through the mountains? Pfft! ;-)
I wish I had his luck with downhills and/or tailwinds..

hippy
Oh, he could go to singlespeed.. that'll learn 'im! :-)

"hippy" <[email hidden]> wrote in message news:[email hidden]...

Quoted message said:

"David S. Maddison" <[email hidden]> wrote in
message

Quoted message said:

I have a friend who feels that he wants taller gears on his MTB, the
problem being that he is pedalling as fast as he can at 60kph. I said
that MTBs are optimised for speeds less than that and if he wants
gearing to go to faster speeds he should go for a road bike.

He might be able to pedal faster than that with training?
Find out what his cadence is at 60kph.. I'm sure it's pretty hard
to really spin out in mtb top gear?

Quoted message said:

Is there any reasonable compromise? Is it possible to have a good low
range and a gear or two for fast speeds such as 60-80 kph+?

With a standard 42-32-22 set of chainrings, he could fit a
road cassette and still have a fairly good range of gears.
I used this setup briefly and from memory it's quite good for
a commuting setup. Assuming he has a 12T or 13T cog on
the rear, going to a 21-11 or 23-11 cassette should give
him a bit more speed in the top end. Looking at Sheldon's
chart, it seems some of the mtb cassettes go down to 11
teeth too?
Meh! Tell him to pedal faster! ;-)

http://www.sheldonbrown.com/k7.html
http://www.sheldonbrown.com/gears/

Quoted message said:

BTW, in case you are wondering, we are talking about down-hill or wind
assisted speeds :-)

What, he's not doing 60kph through the mountains? Pfft! ;-)
I wish I had his luck with downhills and/or tailwinds..

hippy
Oh, he could go to singlespeed.. that'll learn 'im! :-)

MTB Bike cassettes do indeed go down to 11 teeth, but there are times when that's not enough. What he wants is a 54T chainring,
I've seen a few roadbikes with MTB cranks so I don't see why not the other way around.

Rob

what gears he has now would really help.
he must be spinning pretty fast already, if he has 42/12 l make it about 140
cadence. so going to an 11 on the back will get him to 65. then a 48 on the
front will get him to 75. but you need to worry about chain length and how
many links difference his derailleur can handle

"Rob" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

MTB Bike cassettes do indeed go down to 11 teeth, but there are times

when that's not enough. What he wants is a 54T chainring,

Quoted message said:

I've seen a few roadbikes with MTB cranks so I don't see why not the

other way around.

My roadbike doesn't even have a 54T chainring..
If he's that fast, maybe he needs a roadbike?!

3rd party chainring makers might be able to supply
a larger chainring for your mate's cranks - cheaper
than a whole crankset - assuming he has cranks
that allow chainrings to be swapped? What type
of cranks does he have (Acera, Deore, XT, etc)?
Maybe Shimano has larger chainrings for mtb but
I don't think they'd go near 54T. I'm not sure if
the spider design allows road rings to be fitted to
an mtb either.

Shifting from 22 to 32 to 54 could be a problem.
Front derailer adjustment would be horrid I'm
guessing, if possible at all?

Looking here:
http://www.cambriabike.com/cranks&rings/chainrng.htm
48T seems to be the largest chainring.

Try:
<http://www.phantomcycles.com.au/Content.asp?S=Details%20@ID=420>
or maybe www.dirtworks.com.au

Sounds like a bit of a pain for a few kph at the
top end of his gearing..

HTH
hippy

David S. Maddison:

Quoted message said:

I have a friend who feels that he wants taller gears on his MTB, the
problem being that he is pedalling as fast as he can at 60kph. I said
that MTBs are optimised for speeds less than that and if he wants
gearing to go to faster speeds he should go for a road bike.

Is there any reasonable compromise? Is it possible to have a good low
range and a gear or two for fast speeds such as 60-80 kph+?

BTW, in case you are wondering, we are talking about down-hill or wind
assisted speeds :-)

Most MtBs have compact chainrings which are fine for off-road, but not
really suitable for on-road if speed is desired.

There is no need to buy a road bike; getting larger chainrings might be
sufficient. "Traditional" or "standard" chainrings which typically have
ranges of 26-36-46T or 28-38-48T can add significantly higher gears,
even if the cassette is left unchanged. An additional cost, however, is
a new front derailer if the current one can only operate up to a 44T
large chainring.

Experiment with a 26-36-48T setup; this gives a higher top gear while
allowing for mid-gear ratios suitable for off-road tracks.

David S. Maddison <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

I have a friend who feels that he wants taller gears on his MTB, the
problem being that he is pedalling as fast as he can at 60kph. I said
that MTBs are optimised for speeds less than that and if he wants
gearing to go to faster speeds he should go for a road bike.

Is there any reasonable compromise? Is it possible to have a good low
range and a gear or two for fast speeds such as 60-80 kph+?

I used to always bump the gearing on my MTBs but now I'm having second
thoughts. I came from a road background so MTB felt way too short.

I go 46 or 48 up front, 11 at the back.
My dedicated off-roader is standard MTB gearing.

Problems include:
4 arm crank with 48 tooth is very flimsy.
You need a longer more slappy chain.
MTB front derailer curvature is matched to smaller ring.
Clearance is reduced.
MTB chainstays splay out faster, possibly requiring wider BB which
over extends the front derailer. This also gives a bad chain line.
Replacement rings are harder to find.
Shifting isn't as good (up front).
Most MTBing is not at very high speed, that's not what they're for.
If you have open downhill you're either between trails or wasting
altitude that could be spent on more tricky stuff.
There's probably more I can't think of right now.

There really aren't any problems with the rear end. You can try going
road up front but chances are you'll need a much wider BB leading to
above mentioned problems.

Cheers,
Duncan.

Duncan:

Quoted message said:

I go 46 or 48 up front, 11 at the back.
My dedicated off-roader is standard MTB gearing.

Problems include:
4 arm crank with 48 tooth is very flimsy.
You need a longer more slappy chain.

A couple of added links doesn't make an appreciable difference to the
chain "slapping".

Quoted message said:

MTB front derailer curvature is matched to smaller ring.

You need a matching front derailer.

Quoted message said:

Clearance is reduced.

Clearance for what?

Quoted message said:

MTB chainstays splay out faster, possibly requiring wider BB which
over extends the front derailer.

Chainstays are fixed; increasing chainring size from 44T to 48T doesn't
require altering the chainline.

Quoted message said:

This also gives a bad chain line.

Not if you don't change the BB length, and there is no need to unless
road chainrings are used.

Quoted message said:

Replacement rings are harder to find.

Depends on the number of arms on the crank; 46-48T 5-hole chainrings in
110mm BCD aren't hard to find.

Quoted message said:

Shifting isn't as good (up front).

Front derailer must be replaced appropriately; a compact fd will not
work well on a "traditional" chainring set.

Quoted message said:

Most MTBing is not at very high speed, that's not what they're for.

But a compromise can be reached when using it on the road. That's
what's being debated.

"Jose Rizal" <_@_._> wrote in message
news:[email hidden]...

Quoted message said:

Duncan:

Quoted message said:

I go 46 or 48 up front, 11 at the back.
My dedicated off-roader is standard MTB gearing.

Problems include:
4 arm crank with 48 tooth is very flimsy.
You need a longer more slappy chain.

A couple of added links doesn't make an appreciable difference to the
chain "slapping".

Maybe not, but it doesn't help.

Quoted message said:

Quoted message said:

MTB front derailer curvature is matched to smaller ring.

You need a matching front derailer.

True, they might be a bit hard to find and limit options though.

Quoted message said:

Quoted message said:

Clearance is reduced.

Clearance for what?

Rocks and logs and stuff.

Quoted message said:

Quoted message said:

MTB chainstays splay out faster, possibly requiring wider BB which
over extends the front derailer.

Chainstays are fixed; increasing chainring size from 44T to 48T doesn't
require altering the chainline.

It does if the ring now hits the frame, you then need a longer BB axle.
You need good clearance here as bikes flex a fair bit.

Quoted message said:

Quoted message said:

This also gives a bad chain line.

Not if you don't change the BB length, and there is no need to unless
road chainrings are used.

See above.

Quoted message said:

Quoted message said:

Replacement rings are harder to find.

Depends on the number of arms on the crank; 46-48T 5-hole chainrings in
110mm BCD aren't hard to find.

Unfortunatly most modern MTBs are 4 arm.
A road crank often doesn't fit striaght on an MTB due to the wider stays.

Quoted message said:

Quoted message said:

Shifting isn't as good (up front).

Front derailer must be replaced appropriately; a compact fd will not
work well on a "traditional" chainring set.

True, but the bigger the gap the less refined the shift.

Quoted message said:

Quoted message said:

Most MTBing is not at very high speed, that's not what they're for.

But a compromise can be reached when using it on the road. That's
what's being debated.

Of course, I still run a 48 on my commuter bike, but it sucks when I take it
off road.
I've tried a variety of setups on previous bikes, but none have been that
successful. Maybe if I threw more money at it I could sort it all out, but
I tend to wait for things to wear out before I replace them.

The road cranks didn't work well at all because the end of the cranks hit
the frame. After buying an expensive long axle BB (ultegra?) the chain line
was all screwed and by that point I ran out of interest.

hippy said:

"Rob" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

MTB Bike cassettes do indeed go down to 11 teeth, but there are times

when that's not enough. What he wants is a 54T chainring,

Quoted message said:

I've seen a few roadbikes with MTB cranks so I don't see why not the

other way around.

Quoted message said:

My roadbike doesn't even have a 54T chainring..
If he's that fast, maybe he needs a roadbike?!

Quoted message said:

3rd party chainring makers might be able to supply
a larger chainring for your mate's cranks - cheaper
than a whole crankset - assuming he has cranks
that allow chainrings to be swapped? What type
of cranks does he have (Acera, Deore, XT, etc)?
Maybe Shimano has larger chainrings for mtb but
I don't think they'd go near 54T. I'm not sure if
the spider design allows road rings to be fitted to
an mtb either.

Quoted message said:

Shifting from 22 to 32 to 54 could be a problem.
Front derailer adjustment would be horrid I'm
guessing, if possible at all?

Quoted message said:

Looking here:
http://www.cambriabike.com/cranks&rings/chainrng.htm
48T seems to be the largest chainring.

Quoted message said:

Try:
<http://www.phantomcycles.com.au/Content.asp?S=Details%20@ID=420>
or maybe www.dirtworks.com.au

Quoted message said:

Sounds like a bit of a pain for a few kph at the
top end of his gearing..

Quoted message said:

HTH
hippy

I have a friend who put 105 cranks on a Shogun MTB.
It worked fine.

You could look around for some secondhand cranks.

Cheers.
--
Nick

"David S. Maddison" <[email hidden]> wrote in
message news:[email hidden]...

Quoted message said:

I have a friend who feels that he wants taller gears on his MTB, the
problem being that he is pedalling as fast as he can at 60kph. I said
that MTBs are optimised for speeds less than that and if he wants
gearing to go to faster speeds he should go for a road bike.

Is there any reasonable compromise? Is it possible to have a good low
range and a gear or two for fast speeds such as 60-80 kph+?

BTW, in case you are wondering, we are talking about down-hill or wind
assisted speeds :-)

David

David,

44 front, 11 rear, 100 cadence, 26"MTB tyre= ~49kmph. This should be easy.
If your mate is capable of getting to 125 cadence he is doing over 60kmph.

You can pick up a 46 fairly easily, this brings 100 cadence to 51kmph and
125 to to about 64. Remember you still have all the MTB range to select
from eg 28~34 or thereabouts. The cadence of 125 is not super quick, many
riders regularly spin at 90-110.

If your mate can push a MTB at 80kmph even with a tail wind and slicks, then
get him into racing.

Kevin

K&C Russell said:

David,

44 front, 11 rear, 100 cadence, 26"MTB tyre= ~49kmph. This should be easy.
If your mate is capable of getting to 125 cadence he is doing over 60kmph.

You can pick up a 46 fairly easily, this brings 100 cadence to 51kmph and
125 to to about 64. Remember you still have all the MTB range to select
from eg 28~34 or thereabouts. The cadence of 125 is not super quick, many
riders regularly spin at 90-110.

If your mate can push a MTB at 80kmph even with a tail wind and slicks, then
get him into racing.

hmmm... if only I could sustain it, and it wasn't only down huge
hills... 60's easy downhill - even off road - not singletrack, mind
you!

I run 44/11 and knobbies or a rear semi slick.

But racing? I suck! You have to go uphills too!

Tony F
www.thefathippy.com

"tony f" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

hmmm... if only I could sustain it, and it wasn't only down huge
hills... 60's easy downhill - even off road - not singletrack, mind
you!

Rode the 'Red Hot Rim Run' near Healesville with Keiran Ryan's ORCA group a
few years back. 800m descent in about 12 kms, on sketchy gravel firetrail
and double track dodging through mountain ash forest. I hit 59 kmh - heart
in the mouth stuff. Thought this was pretty good until I spoke to some of
the guys on their downhill sleds, they hit 79 kmh !!!!

Quoted message said:

I run 44/11 and knobbies or a rear semi slick.

Sounds a good setup for road and dirt riding. Mine is a 46/11 and the 46 was
the standard chainring on MTBs when I bought mine 10 years ago. Now does
very well as my touring setup, for road riding and high country back track
touring.

Cheers
Peter

"Peter Signorini" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

"tony f" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

hmmm... if only I could sustain it, and it wasn't only down huge
hills... 60's easy downhill - even off road - not singletrack, mind
you!

Rode the 'Red Hot Rim Run' near Healesville with Keiran Ryan's ORCA group

a

Quoted message said:

few years back. 800m descent in about 12 kms, on sketchy gravel firetrail
and double track dodging through mountain ash forest. I hit 59 kmh - heart
in the mouth stuff. Thought this was pretty good until I spoke to some of
the guys on their downhill sleds, they hit 79 kmh !!!!

My max was 88 down that track, and that was with a 42/11 gear. What really
makes the difference is knowing a few corners before the really steep bit
not to touch the brakes. At one point the ground drops away faster than you
can and you float above the surface :-)

I'm about to replace my 46T outer ring with a 48T and the 24T inner with
a 22T one. The middle ring will remain a 34T. This is nearly the same as
one of the 2 new Shimano XT crankset ring options 48T-36-22. As XTR and
XT front derailleurs are often compatible with a 48T outer ring, this
should give adequate shifting with my new XTR fd I'm hoping. I'm
currently running a custom 11-30T 9spd cassette which is due for
replacement at this time also. I've been encouraged to adapt my existing
Race-Face cranks as the new XT ones r costing around $440 🙁.

The upcoming 20th anniversay Great Vic Ride is also starting atop Mt
Hotham this year so with around 40kms of downhill on day 1, I expect to
exceed last years 80kph coming down Mt Macedon.

We do all know that a WRX Suburu is sort of the equivalent of a road
riden MTB dont we? So why cant we have our cake and eat it too with just
a few adjustments?

(ps. On the 1st Great Vic Ride I had a racer with 60T-46 rings and a
6spd 13-24 cluster. Yes! ....not exactly a good uphill gearset around
Beechworth, but what a blast coming down. Nowadays I spin much faster
than my old slogging and can go nearly as fast with 46/11.)

--

Quoted message said:

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