questions for noob on CX bike

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Permalink Reply by Chris Mayhew on June 30, 2011 at 11:47am

Get the same size 'cross frame as you have road bike. You may go with a shorter/higher stem and a slightly lower saddle but the basic fit should be the same.

http://www.cycle-smart.com/articles/find.php?search=31

 

Road wheels and 'cross wheels are basically the same thing. I use mine interchangeably.

 

Yes, you can use your road group on your 'cross bike, minus the brakes and with a tweak in gearing as you mention.

 

Good luck!

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Permalink Reply by Joey Mullan on June 30, 2011 at 6:16pm

Remember though, some companies have a higher BB than std road frames so a 56 top tube bike would ahve a 54cm seat tube. With Cannondale, you would ride a 54... Just have a qualified shop help you out with your frame/bike purchase. As per your fit to your bike, you are not trying to cheat the wind, just have a lot more leverage over the bike, a little more upright riding position would be ideal.

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Permalink Reply by ZenNMotion on July 1, 2011 at 2:07pm

I'm the same height and weight as you and my CX rigs all have 56cm top tubes, with 11 cm stems.  My road bikes are also 56cm with 12cm stems.  My CX saddle position is about 1cm lower and a little forward of my road position, and the reach to my bars 2 cm shorter and the bar is about 2cm higher than my road bike. I like to sit a little lower in the saddle, more upright and forward for cross for better handling on technical sections and high end power. Some people choose a CX bike with a top tube a little shorter than their road bike- I rode a 54cm for my first couple of years with the same 12 cm stem that I ride on my road  bike.  It felt comfortable enough, but eventually I figured out that the smaller frame with a longer stem put too much weight on my front wheel. The larger frames handle better in sand and deep mud where they don't sink in and plough- hold a better line, and it's easier to lift the front end over obstacles.  So I'd just get a 56cm and a slightly shorter stem than your road bike, and be sure you're able to raise the handlebar with spacers or higher rise so that it's a little higher than your current position.

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Permalink Reply by andrew on July 2, 2011 at 11:51am

Just a little geeky but impt point. Not all 56cm top tube bikes will fit the same.  You can't compare top tube lengths between road and cyclocross bikes, or even between two cyclocross bikes, without looking at seat tube angles. 

 

You position your seat fore/aft in relation to the bottom bracket, so seat angle really determines the "effective" and "adjusted" top tube length. 1 degree difference can mean more than .5cm difference at your size. Seat tube angles can vary 2 degrees or more.

 

So a bike with a steep seat angle, whether a road or cx bike, has a "default" saddle position further forward than one with a shallow angle.  That's why many people make mistakes in buy a Lemond bike that's too small because they get tricked by the long top tubes that are paired with slack seat angles and think the bike is long. Assuming you can move your seat forward a bit on the rails, sizing down ends up with a cramped position and needing a longer stem.

 

Regarding positioning, I do find a more upright position, with brake levers tilted up a bit more than road, is comfortable for me. It also helps avoid endos when things get steep!

 

Hope that helps. Good luck. You'll have a blast.

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