MTB speed increase ideas

Quoted message said:

Hi all,

A friend of mine just got his first MTB. It's an entry-level beast,
and used for commuting right now. My friend wants to extract more
speed out of the thing. I checked it out, and his gearing is one
culprit....a 42T large ring and a 12T sprocket is his fastest gear
combination.

He took it back for a tune-up (general sporting goods store), and they
indicated something about using a 9T or 10T sprocket!?! Does such a
thing even exist? I told my friend to forget about it, but it piqued
my curiosity....

Any sprocket less that 13 teeth is stupid. It wears too fast, and the
percentage change in gearing from one to the next is too great for
fine-tuning your cadence. The only reason it is acceptable on a road
bike is that you are working with a 53 or 54 tooth chainring and so the
relative change in ratios are still almost acceptable. With a 42 or 44
in the front, you are about 10% change from cog to cog.

Quoted message said:

In the meantime, I've got a cassette with an 11T sprocket to 'upgrade'
his bike, and I'll suggest a chainring swap from a 42T to a 44T. This
will buy him a little more speed.

Just get a 48 tooch chainring. 44 is a very small change from 42: 5%
That is less than the value of going from 14 to a 13 for instance. It
is equivalent to shifing from a 22 to a 21 in the rear: a small gear
change.

Quoted message said:

Are there any other obvious speed improvements to be made? Slicks will
reduce rolling resistance, but I'm reluctant to suggest them because
the bike will still be used for some light-duty off-road use. Since
the speed problem is due to him 'spinning out', slicks won't
appreciably change his top speed anyway.

Say what? "Spinning out" is not a problem for someone who can spin. I
can spin 150 RPM at a road speed of 25 MPH and keep at it for 20
minutes. It takes practice. Knobbies make a lot of wind resistance as
well as tread squirm. If you want to go fast, you have to reduce drag.
Jsut remember that slicks lower you gear ratios noticably and you need
bigger chainrings to compensate.

Quoted message said:

Can anyone recommend a suitable semi-slick that can be used for
fire/gravel roads and/or light trail use?

Get a road bike. :-)

I ride a road bike with road racing tubulars on gravel and dirt roads
all the time. You don't need some specialty tire to do that.
Mountainbikes are overkill for what your friend is riding on.

Have you ever watched Paris-Roubaix? Makes typical mountainbikes look
like extreme overkill.

On my mountainbike, I have a campagnolo road crankset with 39/53
chainrings. That is one way to get "extra speed" as you call it.
(Actually, just extra gearing). But some mountainbike frames are so
chunky that the 53 tooth chainring will hit the chainstay if you have a
normal bottom bracket.

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

Quoted message said:

Hi all,

A friend of mine just got his first MTB. It's an entry-level beast,
and used for commuting right now. My friend wants to extract more
speed out of the thing. I checked it out, and his gearing is one
culprit....a 42T large ring and a 12T sprocket is his fastest gear
combination.

He took it back for a tune-up (general sporting goods store), and they
indicated something about using a 9T or 10T sprocket!?! Does such a
thing even exist? I told my friend to forget about it, but it piqued
my curiosity....

In the meantime, I've got a cassette with an 11T sprocket to 'upgrade'
his bike, and I'll suggest a chainring swap from a 42T to a 44T. This
will buy him a little more speed.

Are there any other obvious speed improvements to be made? Slicks will
reduce rolling resistance, but I'm reluctant to suggest them because
the bike will still be used for some light-duty off-road use. Since
the speed problem is due to him 'spinning out', slicks won't
appreciably change his top speed anyway.

Can anyone recommend a suitable semi-slick that can be used for
fire/gravel roads and/or light trail use?

Cheers,
Dave

Perhaps cycle continuously uphill?
I jest of course however i was wondering what the primary function of his
riding is? if its a fitness thing and weight of the bike isn't an issue then
perhaps somehow (i'll muse on exactly how) add weight to the bike, in a
balanced matter of course. This would both stop him 'spinning out' as
quickly and if he's able to push the extra weight at a high ratio his top
speed would be significantly increased. this might cause braking/breaking
issues mind.

Quoted message said:

Any sprocket less that 13 teeth is stupid. It wears too fast, and the
percentage change in gearing from one to the next is too great for
fine-tuning your cadence. The only reason it is acceptable on a road
bike is that you are working with a 53 or 54 tooth chainring and so the
relative change in ratios are still almost acceptable. With a 42 or 44
in the front, you are about 10% change from cog to cog.

For my friend, I don't think a change to 11/12T will have much impact
on durability. He's a beginner and simply doesn't ride enough to worry
about wearing sprockets (particularly the low-end durable steel
variety). As for the change in ratio from cog to cog, I personally
don't have any trouble with an 11T (from a shifting or a power
perspective).

Most bicycle manufacturers would disagree with you...while I know they
exist, I haven't seen a new MTB with a 13T (smallest cog) cassette.
This may have more to do with the topography around here...very few
people have DH bikes.

Quoted message said:

Just get a 48 tooch chainring. 44 is a very small change from 42: 5%
That is less than the value of going from 14 to a 13 for instance. It
is equivalent to shifing from a 22 to a 21 in the rear: a small gear
change.

Most (Shimano) deraileurs specify a maximum tooth change from one
chainring to another. Usually, this is a 12T maximum (from large to
middle ring), and quite often there is a 10T minimum. Granted, you can
probably tweak a derailleur to operate outside these
specifications...but the potential for shifting problems definitely
exists.

Quoted message said:

Say what? "Spinning out" is not a problem for someone who can spin. I
can spin 150 RPM at a road speed of 25 MPH and keep at it for 20
minutes. It takes practice. Knobbies make a lot of wind resistance as
well as tread squirm. If you want to go fast, you have to reduce drag.
Jsut remember that slicks lower you gear ratios noticably and you need
bigger chainrings to compensate.

Quoted message said:

I'm sure it's possible to spin at 150 RPM for an extended period of
time, but this is far beyond the 'conventional' cadence range. I
personally cruise at 90-110 on the road (160 when going for speed), but
I find it uncomfortable to spin higher than 120 on my MTB...the
geometry is different and my saddle is lower. For my friend, I have my
doubts that 150 is a realistic target.

Quoted message said:

Quoted message said:

Can anyone recommend a suitable semi-slick that can be used for
fire/gravel roads and/or light trail use?

Get a road bike. :-)

Ha! The MTB cost $350, and an entry-level road bike is more like $700.
Not really an option, I'm afraid. Nice try, though 🙂

Quoted message said:

On my mountainbike, I have a campagnolo road crankset with 39/53
chainrings. That is one way to get "extra speed" as you call it.
(Actually, just extra gearing). But some mountainbike frames are so
chunky that the 53 tooth chainring will hit the chainstay if you have a
normal bottom bracket.

Yes, I meant extra gearing (which implies extra speed, assuming you've
got the power to back it up). My friend definitely isn't strong enough
to manage with just a 39...and I seriously have my doubts that a 53
would come close to fitting his bike.

The primary function of the bike is commuting, as well as some
off-roading on weekends. Adding weight or riding uphill isn't really
the point...he wants to go faster!

Cheers,
Dave

"bill" wrote: Any sprocket less that 13 teeth is stupid. It wears too
fast, and the percentage change in gearing from one to the next is too great
for fine-tuning your cadence. The only reason it is acceptable on a road
bike is that you are working with a 53 or 54 tooth chainring and so the
relative change in ratios are still almost acceptable. (clip)
^^^^^^^^^^^^^^^
Sorry, but the relative change in ratios is not affected by the size of the
chainrings. The change from 12 T to 10 T would be 17%.

bill said:

... "Spinning out" is not a problem for someone who can spin.
I can spin 150 RPM at a road speed of 25 MPH and keep at it for 20
minutes.

Clark Kent Baka! LOL Bill, I'd pay money to see you spin 150 RPM for
/half/ a minute! (This on the purple girl's Huffy or another marvel of
rolling efficiency?)

Quoted message said:

It takes practice. Knobbies make a lot of wind resistance as
well as tread squirm. If you want to go fast, you have to reduce drag.
Jsut remember that slicks lower you gear ratios noticably and you need
bigger chainrings to compensate.

Someone else can take that one.

Quoted message said:

I ride a road bike with road racing tubulars on gravel and dirt roads
all the time.

Ah, yes, the off-road centuries in blue jeans. Maybe Neil Diamond can do a
song about you!

"[censored] on the rocks...ain't no surprise.

Just pour me a drink, and I'll tell you some lies"

Might be a hit! LOL

Quoted message said:

Hi all,

A friend of mine just got his first MTB. It's an entry-level beast,
and used for commuting right now. My friend wants to extract more
speed out of the thing. I checked it out, and his gearing is one
culprit....a 42T large ring and a 12T sprocket is his fastest gear
combination.

He took it back for a tune-up (general sporting goods store), and they
indicated something about using a 9T or 10T sprocket!?! Does such a
thing even exist? I told my friend to forget about it, but it piqued
my curiosity....

In the meantime, I've got a cassette with an 11T sprocket to 'upgrade'
his bike, and I'll suggest a chainring swap from a 42T to a 44T. This
will buy him a little more speed.

Are there any other obvious speed improvements to be made? Slicks
will reduce rolling resistance, but I'm reluctant to suggest them
because the bike will still be used for some light-duty off-road use.
Since the speed problem is due to him 'spinning out', slicks won't
appreciably change his top speed anyway.

Can anyone recommend a suitable semi-slick that can be used for
fire/gravel roads and/or light trail use?

Maybe buy some semi-slicks; they'll /feel/ faster and more lively than
knobbies on pavement and gravel surfaces. Otherwise, don't waste money
trying to "improve" an entry-level mountain bike! The best way to "extract
more speed out of the thing" is for your friend to get stronger and better.
Then, sooner than later, he'll want a "good bike" and this can become his
beater.

Sorno

In article <[email hidden]>,

Quoted post said:

Are there any other obvious speed improvements to be made? Slicks will
reduce rolling resistance, but I'm reluctant to suggest them because
the bike will still be used for some light-duty off-road use. Since
the speed problem is due to him 'spinning out', slicks won't
appreciably change his top speed anyway.

Can anyone recommend a suitable semi-slick that can be used for
fire/gravel roads and/or light trail use?

Some folks like Continental Town & Country tires for such purposes.
These have an inverse tread. I've read some complaints of
inverse tread tires being lousy mudders, though. I expect they'd
be no worse than slicks on slippery mud (or wet grass for that matter.)
They should be okay on dry hardpack and finer gravel than egg gravel.
There are other brands of inverse tread MTB tires as well. IIRC,
Kenda and Cheng Shin make some.

cheers,
Tom

--
-- Nothing is safe from me.
Above address is just a spam midden.
I'm really at: tkeats [curlicue] vcn [point] bc [point] ca

Quoted message said:

In the meantime, I've got a cassette with an 11T sprocket to 'upgrade'
his bike, and I'll suggest a chainring swap from a 42T to a 44T. This
will buy him a little more speed.

Tell him to pedal faster. 42/12 on an MTB gets you up to 25 mph with a
normal cadence (90 to 95 rpm). If he needs to go faster than that on an
MTB with offroad tyres he must be some beginner.

Quoted message said:

Can anyone recommend a suitable semi-slick that can be used for
fire/gravel roads and/or light trail use?

I'd get tyres by a major brand like Continental or Schwalbe with a smooth
center of the tread. They're likely to roll a lot better than whatever
the bike came with.

-as

Bill Sornson said:

bill said:

... "Spinning out" is not a problem for someone who can spin.
I can spin 150 RPM at a road speed of 25 MPH and keep at it for 20
minutes.

Clark Kent Baka! LOL Bill, I'd pay money to see you spin 150 RPM for
/half/ a minute! (This on the purple girl's Huffy or another marvel of
rolling efficiency?)

Quoted message said:

It takes practice. Knobbies make a lot of wind resistance as
well as tread squirm. If you want to go fast, you have to reduce drag.
Jsut remember that slicks lower you gear ratios noticably and you need
bigger chainrings to compensate.

Someone else can take that one.

Quoted message said:

I ride a road bike with road racing tubulars on gravel and dirt roads
all the time.

Ah, yes, the off-road centuries in blue jeans. Maybe Neil Diamond can do a
song about you!

"[censored] on the rocks...ain't no surprise.

Just pour me a drink, and I'll tell you some lies"

Might be a hit! LOL

Sorni, I think this is a different "Bill."

R Brickston said:

Bill Sornson said:

bill said:

... "Spinning out" is not a problem for someone who can spin.
I can spin 150 RPM at a road speed of 25 MPH and keep at it for 20
minutes.

Clark Kent Baka! LOL Bill, I'd pay money to see you spin 150 RPM
for /half/ a minute! (This on the purple girl's Huffy or another
marvel of rolling efficiency?)

Quoted message said:

It takes practice. Knobbies make a lot of wind resistance as
well as tread squirm. If you want to go fast, you have to reduce
drag. Jsut remember that slicks lower you gear ratios noticably and
you need bigger chainrings to compensate.

Someone else can take that one.

Quoted message said:

I ride a road bike with road racing tubulars on gravel and dirt
roads all the time.

Ah, yes, the off-road centuries in blue jeans. Maybe Neil Diamond
can do a song about you!

"[censored] on the rocks...ain't no surprise.

Just pour me a drink, and I'll tell you some lies"

Might be a hit! LOL

Quoted message said:

Sorni, I think this is a different "Bill."

Rats. You're right, of course. The "road racing tubulars" should have
tipped me off, but that spinning 150 RPM for 20 minutes is just so...BAKA!

My apologies, Iron Bill. Hope you liked the song, at least 🙂

Quoted message said:

Yes, I meant extra gearing (which implies extra speed, assuming you've
got the power to back it up). My friend definitely isn't strong enough
to manage with just a 39...and I seriously have my doubts that a 53
would come close to fitting his bike.

I'm confused then. This "beginner" runs out of gearing doing 25 MPH
with a 42:12 doing just over 90 RPM, and yet he is too whimpy to get by
with "just" a 39 tooth small ring (and an MTB granny-gear block to
boot).

Something does not compute:

42/12 = 3.5
3.5 * 26" *3.14*90*60/12/5280 = 24.35 MPH. spin at 120 (that is
certainly doable with even a little practice) and you have 29 MPH.

replace the 42:34:26 or whatever with:
49:39 Cyclocross setup and you have a top speed at 90 RPM of
(49/12)/(42/12) * 24.35 = 28.41.

And you probably have a 28 toother on the block, so a low ratio of
39/28 = 1.39 or gear inches of 36.2, which is pretty damn low. Any
lower and you'll be faster dismounting and running. (What's worng with
mountainbikers anyway--get off and run you fools!🙂

Leo Lichtman said:

"bill" wrote: Any sprocket less that 13 teeth is stupid. It wears too
fast, and the percentage change in gearing from one to the next is too great
for fine-tuning your cadence. The only reason it is acceptable on a road
bike is that you are working with a 53 or 54 tooth chainring and so the
relative change in ratios are still almost acceptable. (clip)
^^^^^^^^^^^^^^^
Sorry, but the relative change in ratios is not affected by the size of the
chainrings. The change from 12 T to 10 T would be 17%.

You are right...brain fart.

I meant to say that the relative change per tooth is less severe, the
larger the number of teeth you have to start with, so 53 vs 52 is lless
change than 43 vs 42 etc.

Quoted message said:

3.5 * 26" *3.14*90*60/12/5280

*3600

= 24.35 MPH

sorry about the omission.

Bill Sornson said:

bill said:

... "Spinning out" is not a problem for someone who can spin.
I can spin 150 RPM at a road speed of 25 MPH and keep at it for 20
minutes.

Clark Kent Baka! LOL Bill, I'd pay money to see you spin 150 RPM for
/half/ a minute! (This on the purple girl's Huffy or another marvel of
rolling efficiency?)

Pay me real money and I'll spin 200RPM for you for 30 seconds.

Quoted message said:

Hope you liked the song, at least 🙂

Yep.

[email hidden] says...

Quoted message said:

Hi all,

A friend of mine just got his first MTB. It's an entry-level beast,
and used for commuting right now. My friend wants to extract more
speed out of the thing. I checked it out, and his gearing is one
culprit....a 42T large ring and a 12T sprocket is his fastest gear
combination.

Your friend doesn't need new gears. 42/12 is good for 24 mph (39 kph)
at your basic 90 rpm cadence. If he can sustain that for any length of
time on level ground riding a cheap MTB with knobbies, he should quit
his day job and get serious about going pro. However, semi-slicks will
help a little and there are a variety to choose from. I used Michelin
Jet-S for a while, but they are out of production, not to mention pricey
and prone to punctures. If he doesn't do any off-road, get a full slick
and a narrow one. After the slick tires, getting faster will depend
almost entirely on his level of fitness.

bill said:

Bill Sornson said:

bill said:

... "Spinning out" is not a problem for someone who can spin.
I can spin 150 RPM at a road speed of 25 MPH and keep at it for 20
minutes.

Clark Kent Baka! LOL Bill, I'd pay money to see you spin 150 RPM
for /half/ a minute! (This on the purple girl's Huffy or another
marvel of rolling efficiency?)

Pay me real money and I'll spin 200RPM for you for 30 seconds.

That rusty hamster wheel in your head doesn't count! <eg>

Quoted message said:

I'm confused then. This "beginner" runs out of gearing doing 25 MPH

Something does not compute:

The landscape here slopes gently down to sea level, with 15 MPH average
tailwinds. When travelling east, you can pick up appreciable
speed...and higher gearing is definitely appreciated by the average
commuter...why not travel faster if you can? Going in the other
direction is a totally different story...staying in the largest
chainring can be quite challenging at 90 RPM.

One other thing I should have mentioned (and this is changing as of
today), my friend is using platform pedals. This probably limits his
ability to efficiently spin at a high rate. He was trying 'em out
tonight, so we'll see if he reports any improvement.

Quoted message said:

Your friend doesn't need new gears. 42/12 is good for 24 mph (39 kph)
at your basic 90 rpm cadence. If he can sustain that for any length of
time on level ground riding a cheap MTB with knobbies, he should quit
his day job and get serious about going pro.

Problem is, there's very little in the way of flats around here, and
the prevailing winds are in the downhill direction....I personally do
about 40-50 km/h on worn knobbies, until I turn around and travel in
the opposite direction. Then I'm sure I average under 20 km/h.

Quoted message said:

However, semi-slicks will
help a little and there are a variety to choose from. I used Michelin
Jet-S for a while, but they are out of production, not to mention pricey
and prone to punctures. If he doesn't do any off-road, get a full slick
and a narrow one. After the slick tires, getting faster will depend
almost entirely on his level of fitness.

I'll check with my LBS...but they do tend to charge quite a bit more
than mail-order.

Cheers,
Dave