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Discussion Starter · #1 ·
Hello all, looking for a little sizing advice:

I ride a 17.5/Med Mtb.
and a 55/56 roadbike...

What size cx bike should I be considering?

Thanks in advance.
 

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three things to measure off your road bike are the top tube length and the length from tip of saddle to center of handlebars, then also the ht of top of saddle from the floop (minus) the height of handlebars from floor (handlebar drop)

Now, you want to get either same length top tube or a bit shorter (my choice) and a stem that gives you a little shorter (maybe 1 cm) length on the second measure and a little less handlebar drop. "a little" means half an inch or so. You want a slightly shorter, taller setup compared to your road bike.

This assumes your road bike fits correctly in the first place.
 

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Discussion Starter · #3 ·
thanks jroden - that is exactly the sort of info for which I was looking. Are there any gereralities, such as, "typically people ride a cx bike one size smaller/larger than their road bike"?
 

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I generally do, I ride a 58 on the road and like about 58.5 top tube for road, but have ridden as small as a 56 cross bike, now I have a Merckx which has a 57 top tube, I think the seat tube is a 56, so I am actually riding 2 sizes down but this is on a larger frame than you were talking about. I rode a year on a 58 cross frame which is my normal road size and felt it was a little large for my tastes, but there are plenty of riders better than me who like to run the same size as their road bike. You will have a larger standover height on most cross bikes in the same size as your road bike, which I don't really liek as it raises up your center of gravity and you have to jump just a little higher to get back on the bike, so for me I like the smaller bike and feel like I ride better on it--all I do with my bike is use it for racing and training for racing, it's not too comfortable for road rides as it is somewhat short across the top.

You have to really look at the frame geometry tables and go into the shop with a tape measure, don't use rules of thumb for a major purpose, figure out the size based on number, if you go half inch shorter and half inch taller than your road bike, or maybe a shade more, I think that is a good size, others may differ, that's just what works for me. Be careful of buying used / ebay if you don't know for sure what size you need.
 

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cjpavlov said:
thanks jroden - that is exactly the sort of info for which I was looking. Are there any gereralities, such as, "typically people ride a cx bike one size smaller/larger than their road bike"?
There shouldn't be any hard and fast rule about riding one size down. My road bike is listed as a 54 but has a 55 top tube. Both of my cross bikes have 54.5 top tubes which I find to be very comfy. Stem lengths are identical on all bikes.

Try to ride some cross bikes before buying -- even if you plan to buy used, head down to the LBS's and ride as many bikes as you can to get a good feel for what you like. Pay attention to stem setup (spacers, stem up/down) and then lookup the geometry. That will get you a pretty good idea of what works for you.

Get the bike that feels right. Don't size down from the one that feels right.
 

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Discussion Starter · #6 ·
Thanks so much for all the good info! I will do some measuring of my current bikes and then test ride some before I purchase. Thanks again
 

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I like a size smaller. 54cm road toptube. 52.5cm cross. If it is a traditional toptube (non-sloping) you may go a little smaller to get better standover.
 

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hairscrambled said:
I like a size smaller. 54cm road toptube. 52.5cm cross. If it is a traditional toptube (non-sloping) you may go a little smaller to get better standover.
As long as you have standover, that's enough. It is a fallacy that cross requires more room than road. Cross bikes often have higher bb's and the tires have a bit higher profile so that will reduce standover a bit so YMMV.
 
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