MTB speed increase ideas

Leo Lichtman wrote:
"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.

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

*3600

= 24.35 MPH

sorry about the omission.

Bill Sornson wrote:
bill wrote:

... "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.

Hope you liked the song, at least

Yep.

says...

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 wrote:
Bill Sornson wrote:
bill wrote:

... "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

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.

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.


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

wrote:
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....

I have one with an 11 tooth small sprog in the back but I have never
heard of a 10T or 9T since it does not look like they would fit over the
bearings and such in a rear hub. Maybe I missed something. My absolute
top is a 58/11 and I have to lose the granny for that but pedaling a
58/11 around town is a serious quad workout, just not practical once I
see a hill.

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.

I just bought a 26x1.80 slick yesterday aw Wal-mart only because it
caught my eye and I was there to return a defective (Belkin) router.
I got the super heavy duty tube too, but by the time I was done it was
too hot to ride. 92 degrees at 10 A.M, 100 by noon, and 112 by 4 P.M.
As much as I like to ride, I hate sweating buckets even more.
Bill Baka

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

Cheers,
Dave

Bill Sornson wrote:


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

I didn't say I got any useful power at 150 RPM but I can do that cadence for about that time and then I have had it, even at 12 MPH.

The cadence itself wears me out.

Bill Baka