Cyclocross - Standover height / sloping TT

Just curious, where is standover height measured on a frame with a sloping top tube? Many of the cross frames appear to be too tall for me. I'm thinking of building up a cross bike but the geometries of many frames I have looked at don't compare at all to my classic frame roadie, not that I expected them to. My 49cm roadie fits perfectly but I imagine that I would want a bit more clearance for racing purposes. Thanks for helping.

Actually you want more clearance under the top tube for shouldering and unshouldering the bike. IMO there is no good reason to consider standover as a metric for choosing a frame.

It's a bit tricky to compare geometries when the top tube isn't horizontal. Effective top tube is only half of the equation ("effective seat tube" being the other half, but is rarely published). There's also the general weirdness in geometry for 700c bikes under 50cm. If you are honing in on a bike and don't have a chance to test-ride, you might want to draft up a scale drawing to compare with your existing bike.

There is a persistent myth that a cross frame should be sized smaller than a road frame. IMO that's a mistake. A smarter rule of thumb is to size the cross frame same as road frame, but set up the bars/stem 1cm shorter and 1cm higher.

in agreement with the above post: standover doesn't matter, steeply sloping top tubes make the bike hard to shoulder.

at 49 cm you should be able to find a mtb frame with a horizontalish top tube, canti brakes, 26 inch wheels. put some skinny tires (and bars/levers if you want) on there and you've got a sweet small cross bike.

at 49 cm you should be able to find a mtb frame with a horizontalish top tube, canti brakes, 26 inch wheels. put some skinny tires (and bars/levers if you want) on there and you've got a sweet small cross bike.I wish I could agree with you but finding a light rigid mtn bike that fits the bill is really tough.

Does anybody make a stock CX bike for 26" wheels that doesn't suck? AFAIK no.

it's tough to find new model bikes that fit the bill, but in the early 90s they were all over the place. i was thinking something like an old stumpjumper or rock hopper. light is a matter of opinion, but an extra pound on the frame can pay for itself in toughness, if you can find a good frame.

I lifted a friend's old rigid stumpjumper, it was suprisingly light. Easily under 25 pounds. With some modern parts it would make a good steel cross bike. Stumpjumpers, as opposed to hardrocks, have always been pretty light with racey geometry. Rockhoppers are somehwere in between, probably depends on the year.

I got my butt handed to me last race by a guy on an old rigid mountain bike (was high end in its day, actually) during my last race.

you can find lots of cross bikes out there in the 49 or 50 cm range. screw the mtn bike option. felt makes a 49 cm and surly makes a few small options in the cross check,..and there's the bianchi's...etc. as i said, plenty of options. all of them 700c.

Redline makes a 44 and a 48cm cross frame.

Kona makes a 47cm Jake with 700cc wheels. I know this cause I have the 2008.