On Sat, 04 Aug 2007 16:27:49 -0500, Tim McNamara
wrote:

In article ,
wrote:

On Sat, 04 Aug 2007 12:33:57 -0500, Tim McNamara
wrote:

In article ,
"Tom \"Johnny Sunset\" Sherman" ""sunsetss0003\"@invalida .com"
wrote:

See http://www2.trekbikes.com/Bikes/2007/mountain/69er.html.

Is the bigger front wheel to better roll over obstacles, or is it
just a demented fashion statement? Conversely, does the smaller
rear wheel provide any real advantage?

Back in the day, Charlie Cunningham built MTBs with a smaller rear
wheel- IIRC 20" rear and 26" front. Many dirt motorbikes have a
smaller rear wheel. I have no idea why. Maybe Carl Fogel does, he
used to ride trials and the like.

Dear Tim,

Sorry, but we fooled you.

Don't feel bad, since 9 out of 10 trials riders will mistakenly
insist that their front tires are bigger.

After all, trials machines use 21-inch front rims and 18-inch rear
rims, so the front tire must be 3 inches taller, right?

Nope.

Interesting! Never having and anything to do with motorcycles, I'd not
thought much about this. The cycling parallel would be something like
having a 650B X 37 rear and a 700C x 18 front. The overall diameter is
just about the same, but the section width of the tire is very different.

Dear Tim,

Exactly--fat or thin, they end up awfully close to the same height.

Incidentally, high-level bicycle trials riding rarely involves tires
"rolling" over obstacles or even pedalling. It's mostly acrobatic
hopping with locked wheels and motionless cranks:

http://www.youtube.com/watch?v=kTAUQrQVTTk&eurl=

In contrast, motorcycle trials still rolls up and over wet rocks:

http://www.youtube.com/watch?v=HwzykvxNeCY

This is closer to bicycle trials:

http://www.youtube.com/watch?v=x5QJCXkYea8&NR=1

Cheers,

Carl Fogel