Slim... The differences between a rigid mtb and cyclocross bike go much further than wheel sizes.

The geometries are markedly different.

The primary difference is tire width, not geometry, Sixty...

- Slim :)

CX bikes and MTBs both have Geos that are all over the charts. Pretty tough to find a CX bike with a wheelbase as long as a MTB, though.

I guess the 1991 Gary Fisher Montare has a wheelbase about the same as some CX bikes. It was a pretty special MTB, though.

http://mombat.org/91MontareSide.JPG

Actually I invented the mountain bike - in 1960 when I was seven years old. I don't remember the make or model of the bike in question, only that it was a Christmas gift. Over the next couple of years I, along with all the other seven year olds in the neighborhood, rode and rode and rode. We lived in Lakewood Colorado, west by Alameda Ave up there by Green Mountain and there is not one square inch of that mountain that we didn't ride on. The mountain bike was invented by thousands of us 7 year old kids bombing through the mountains and forests. We want our credit and some of the money, please

Actually, the U.S. Army invented the mountain bike back in the 1890's. African-Americans were the first MTN bikers here in the United States of America. They were called, the Buffalo Soldiers. They traveled from Missoula, Montana, to St. Louis, Missouri, back in 1897. A total of 1,900 miles, as an experiment. The U.S. Infantry was thinking about riding special MTN bikes in order to have a greater advantage in surprise attacks upon possible enemies. Rather than have the sound of galoping hoofs of horses announce the planned attack from greater distances away, they could take greater advantage of the element of surprise. However, the invention of the motor car stifled the bicycle war implementation, as the motor car proved to be far to swift for any enemy to adequately prepare for the onslaught of an impending attack. Therefore, the first MTB, was a rigid hardtail, for certain!

- Slim :)

http://bikeforums.net/attachment.php...hmentid=227490

I have heard the Cruiser argument before. They were coasting down hill for a thrill and the Cruisers fit larger tires. They quickly dumped the heavy single speed cruiser frames for touring frames with 26 inch wheels laced to the multi speed hubs to get wider tires on them and gears to deal with the hills.

Its the same line as the BMX has it roots in the Stingray as bike thats really a kids sized cruiser.

70's Mountain bikes gemoetry was closer to Touring bikes when they first came out with the "Mountain bike" except they had 26inch wheels to make more room for wider tires primarily and flat bars. The Top tube length was close to the same as the seat tube. Now mountains tend to have long top tubes in relation to the seat tube to allow for climbing steep hills without slamming your knees into the bar.

Cross bikes are more of a road geometry with clearance for wider tires that are usualy 700c based and drop or dirt drops more like a road bike.

While the exploits of the 25th Infantry U.S. Army Bicycle Corps are remarkable, they were hardly the first use of a bicycle for traveling where there were marginal or no roads. Roads of the 1890 weren't all that great to begin with and the bicycle of the day resembled mountain bikes of today only because of necessity. The 25th Infantry's trip was 13 years after Thomas Steven's trip around the world on an ordinary and 2 years after George Loher's ride across the US. He even passed through Missoula and the 25th followed much the same route as he, and Stevens, took to St. Louis.

Nor were they the first military application of bicycles. That distinction belongs to the French Army in the Franco-Prussian War of 1870. And those bikes were ordinaries.

Their bikes weren't even 'mountain bikes' since they were slightly modified Spaulding Roadsters. The bikes were modified to carry the heavier loads that soldiers had to carry but they were, essentially, the same bikes that consumers used that were build for the conditions of the roads in 1897...which was abysmal.

Close but no cigar. The first production mountain bike geometry...the Specialized Stumpjumper...was closer to the Schwinn Excelsiors on which the Marin County mountain bikes were based. Touring bikes and touring bike geometry was a solid road bike geometry with slightly longer wheelbases and slightly slacker head angles than racing bicycles. In fact, cyclocross bikes were based off of touring bikes that racers used for winter training and touring bikes have little in common, frame-wise, with mountain bikes.

There's also more to the changes in mountain bike frames than just lengthening the top tube. The rear stays have been made shorter to tuck the wheel under the rider so that the wheel doesn't spin out as much, making climbing easier. The front to center of the bike has been made longer to balance the rider between the wheels so that the front wheel doesn't come off the ground while climbing and the rear wheel stays engaged. Head angles have been steepened to reduce wheel flop...a big problem with a 69 degree head angle of the Excelsior. The changes aren't about keeping the rider from bashing their knees but about making the bike a better hill climbing machine.

You are right about the tire width. That's just a small part of the differences and certainly not the primary one.

Caught me before the3 edit LOL

another sliver of history
 

When we first moved to Phoenix in the 60s there was this huge empty lot across the street with an abandoned pit. The neighborhood kids were riding everything in there. Stingrays, 10 speeds, customs, motorcycles, etc.

There was an assortment of downramps with hillocks so you could coast down one ramp and jump the next hillock. The ramps were smoothed from all the kids riding up and down them. This was long before I ever heard of BMX or anything similar. I never learned to jump well. I did manage to land almost perfectly upside down with my schwinn varsity once. :D

Truth is I think all kids push the limits with whatever they have. Part of growing up.