supton

I've been looking at some CX bikes lately, not for racing or riding off road but for regular road riding. While shopping, would I expect to be on the same size bike as if I were shopping for a regular road bike? That is, if I normally ride a 53cm road bike, would a 53cm CX bike be right? I know one typically rides an MTB a size or two smaller, for quicker dismount reasons; but the rest of the bike is sized to "fit right". Are CX bikes done in a similar fashion?

flargle

There is too much variance from company to company to say. A big part of the problem is slanted top tubes, but also, different companies have different ideas about top tube length compared with seat tube, etc etc etc.

That said, you will want to size the cross bike as if you were sizing a road bike, whatever its purpose. You might read or hear someone recommend "sizing down" a cross frame; don't listen to them. Road fit is easily converted to cross fit by (1) lowering the saddle 1 to 2 cm and (2) flipping the stem, both of which move the bars a bit closer to the saddle. "Sizing down" the frame does the exact opposite, it moves the bars down and away from the saddle.

zinncycles.com has a little program that converts three bodily measurements into recommendations for frame dimensions. Just do the measurements, especially pubic bone height ("inseam"), very carefully.

jbpence

i have found i ride the same size in a 2006 specialized sworks tricross (a 54) as one of my road bikes (a felt F1 Team frame - traditional geometry) and a size smaller than my specialized roubaix elite (relaxed geometry = slanted top tube). generally, one might expect to go down a couple of centimeters (compared to a road frame), but this is because the bottom bracket is typically higher on a cross bike. but as the other poster noted, cyclocross bikes, and road bikes v ary a lot between manufacturer and even between models from the same manufacturer.

like any bike purchase (iMO) just get a professional fit. problem solved.

flargle

It all depends on the "professional" who is doing the fitting.

jbpence

yup, though its obvious, i could have added 'from a competent fitter', though I gotta ask, why deal with a shop that has incompetent fitting??? Thats how I PICK the shop in the first place, so that fit competency is a given before purchasing is even discussed.

shapelike

I'm curious, in the past what's been a competent fitting process that you've undergone?

jbpence

Bikesport, in Dearborn, MI. a video is taken with you on the bike. then from stills from the vidoe (displayed on a large screen), measurements of key angles are taken. that was for my custom build Felt team frame. bike fits perfectly.

and I've been thru the FIT process, as well as some totally incompetent fittings that were a JOKE because the fitter was... well, a joke. I've even been thru fittings that basically was only a rudimentary check of the standover height, as in "that looks fine, thats your size"

TRaffic Jammer

Marinoni sent me a fit guide(jpg) for their Fango.

SS_MB-7

I just sent an email to Marinoni regarding their Fango. I'm looking for a custom steel CX frame. I was goofing around on the weekend, in between shoveling efforts, and plugged some numbers into BikeCAD. Here's my first draft:

sfcrossrider

My CX frame has a 57.5 tt (115 stem), and my track bike has a 60 (110 stem).

bitterken

Most of the people I know start with CX frame that has the same effective top tube length as their road bike.

PapaLegba

you're going to have to find a bike that fits you and to through all the geometry yourself.

because one company's 59 is another's 61 and so forth.

it's actually pretty arbitrary.

SS_MB-7

Yes, that's why I love plugging the numbers into BikeCAD to actually SEE what the bike looks like on paper instead of just numbers, angles, etc. There is a lot of variation amongst bikes, and unfortunately, not all the data is given when they provide specs, so it can be tough to get a full design. But, it's better than nothing.

sfcrossrider

I would go and test ride some cross bikes.