waltersc

I did some test riding yesterday on a Giant TCX 2 and a Specialized Tricross. I am curious if cyclocross bikes run large? For example I ride a 58cm Tarmac (100mm stem), but I tested a medium TCX and Tricross. Since I like the way the TCX handles better, the shop is more than willing to order in a large TCX if needed. However the owner feels I would fit much better on a medium. The medium didn't feel to small, and should fit fine with a 110mm stem. I am 6'2" with a 33" inseam. Any others out there ride a smaller cyclocross than road bike? The cyclocross bike will perform multiple functions as a commuter, light trails with the kids and as a spare road bike.

droptop

it seems to me that it really depends on the specific geometry. Dedicated cx bikes will have less bottom bracket drop, which makes the bike feel a size bigger. i normally ride a 57, but on some brands, my cx bike fit would be as small as 52. I am not an expert yet, but others should chime in

waltersc

Thanks, the Giant M has a virtual top tude of 55.6 while my Tarmac is 57.2. Which could create a difference of two cm in reach. I have heard many riders ride a CX bike that is a little smaller than their road bike.

flargle

6'2" on a Medium sounds totally wrong.

What do you mean by "inseam"? Do you mean pant inseam, or do you mean pubic bone height?

waltersc

The measurement is pants inseam. I use is as a reference point only. I agree the medium sounds way to small. I plan on riding the large. Looking at the geometry charts the fit should be right on. While the XL is a 58cm, the virtual top tube is way to long 60.5cm.

knobster

I'm the exact opposite. I ride 54cm road bikes and my Tricross is a 56. I test rode a 54cm Tricross and the top tube was too short for me. 56 was fine with the same size stem.

flargle

I wish people would stop using the term "inseam" when discussing bike fit, because it is ambiguous. If it's a pants inseam, furthermore, it all depends on how you wear your pants. The relevant measurement is pubic bone height, i.e. distance from the ground up to your sit bones.

Not trying to single you out, just my little pet peeve.

The idea of "sizing down" a cross frame is a myth that won't die. If anything, you want a more upright stance and longer wheelbase in a cross bike, IOW a larger frame (all else being equal).

I can't understand why someone would try to put a 6'2" guy on a size M bike. Without tons of spacers and/or serious riser stem, the fit would be more like a track bike than a cross bike.

j. hughes

Isn't it really from ground to pubic symphysis and not the tuberosities (sit bones)?

Not trying to correct you, but am genuinely wanting to know.

isotopesope

my road bike and cross bike have the exact same seat tube and top tube sizes, with the same length stem. my bars sit higher on my cross bike though; they're close to even with my saddle height. also, my cross bike has a super high bb, so the top tube is rather "friendly" while i'm standing over it... which is irrelevant to how it fits while riding.

i'd go with which ever bike has a similar top tube length as your road bike... as long as the head tube lengths are also similar. as others have said, you don't want a million spacers to get your bars high enough.

flargle

Yes I think you are right and stand corrected, but the symphysis (had to check an anatomical chart) is easier to measure and a very good proxy for the tuberosities. I think other systems actually measure leg length directly. But I think ground to taintbone is the most practical way of getting an accurate read, for most people.

wireless

I am 6'5" and I am riding 2007 Giant TCX size XL. At the time of purchase LBS only had size L and it felt small for me, so I ordered XL without even trying. After about week of riding I changed the stem to shorter one with higher angle ( LBS did it for free) to have more comfortable position. No changes after that - great 2 seasons on the bike.
I think M is too small....

Richard8655

56cm Tricross here at 5'10" 32" inseam, very comfortable. Medium sounds way too small for 6'5". 58 or 60cm for a Tricross, I'd estimate. The compact frame philosophy is fine to a point, except when you feel like you're riding your kid's bike jacked up by a 3 foot seat post.

threeflys

I had a converstion with Paul Sadoff of Rock Lobster bikes in March and asked about sizing down on a cross bike... His response was that's a myth, most people do not need to size down on a cross bike. The exception may be if the bike has a really high bottom bracket height, most modern cross bike (some euro frames excepted) have a lower BB height more in with a road bike. While I don't know a lot about cross racing, I'd be inclined to trust Paul... he has a few years building top notch cross bikes...

Kasseien

I think the sizing down myth comes from people wanting enough stand over should the have to exit the pedals under duress. I think this is a pretty bad reason personally, but it is what I have heard people say in the same breath as the down sizing part.

That said, I ride a bike that many people thought was going to be to small but I think it fits me perfect!

pacificaslim

I'm a total newbie but my cross bike is smaller than I'd buy in a pure road bike. I bought it that way because I felt it'd be easier to move around on the bike and move the bike around under me. Face it, riding though dirt and mud and over obstacles often seems a lot closer to bmx or mtb short racing than it is to road racing or touring. You aren't looking for perfect 100-mile-comfort. You're riding for 30min to 1 hr. in a constant state of acceleration, deceleration, turning, pick it up, put it down, jump over this...

flargle

This is the other part of the myth (the first being the "high bottom bracket").

A smaller bike is not easier to maneuver, it is more difficult. Look through some of the pro bikes on cyclingnews.com, the cross bikes tend to have more of a "classic" fit, while the road bikes tend to have smaller frames and more aggressive geometry. Just a frinstance:

Sven Nys


Carlos Sastre

pacificaslim

Sure, that's why BMX bikes are huge, huh? (I grew up racing BMX so it's no myth for me that I find a smaller bike nice in the dirt).

flargle

BMX bikes work fine on pavement and smooth dirt. But when you want maximal speed and control over varied terrain, you get a mountain bike. Which is, yes, larger than a BMX bike.

pacificaslim

Silly me. I apologize for having an opinion.

isotopesope

someone is disagreeing with you. get over it. you also admitted to being new to cross. so why would your opinion carry much weight? you shouldn't believe everything you think.

pacificaslim

Huh? I guess I'll have to put those stupid emoticons next time so you can get the humor and not think I'm whining.

But fwiw, it's fine to disagree but not too polite to call someone's personal experience a myth and keep hounding them about their personal fit preference. It's like telling someone they are wrong for prefering tea to coffee. Being new to cross means my opinion may not be applicable to other people and that's why I, unlike what'shisname, wasn't trying to say I know what's best for other people. I was just presenting a reason why someone, me, likes a smaller bike for off-road riding.

I think he's also mistaken about what his pictures show: of course Sven's bike is bigger than Sastre's. Sven is like 3-4 inches taller. Sven is 5'11" and he rides a 55 seat tube with a 56cm top tube (link). Nearly everyone that height would ride a larger frame for the road. Sastre is listed at 5'8" (must be with his shoes on) but his top tube is a 53cm for example (link).

flargle

Of course their frames are differently sized. The point is the geometry, the relationship of the saddle to the pedals and handlebars. Normally, shorter people have less drop from saddle to bars; the reverse is true of Sastre and Nys.

I don't mean to pick on anyone, but there's this common misconception ("myth") that smaller frames handle better than correctly sized frames. The opposite is true, because when the frame gets smaller, saddle height stays the same. So the handlebars move down and away from the rider, even though top tube shortens. In Sastre's case, this is a deliberate decision to get a more aggressive, aerodynamic fit, but if he raced cross you would probably see a more classic setup like Nys'.

pacificaslim

Ah, I see where you're coming from. When I hear small vs. big, I think top tube lengths and not necessarily seat tube or head tube. But your point about bar drop is a great one. A lot of cross guys want a taller headtube so seat to bar drop isn't as extreme. Another option is just to run the stem higher and angled up a bit (that's what I have). Another good thing about a frame with a larger seat tube though is that it's easier to get it on one's shoulder! I wish I had a bit more room in that regard.

flargle

A lot of guys who come to cross from mtb get a bit freaked by the low standover clearance....

waltersc

Thanks for all the input. I did some research and found the smaller CX bike to be a myth. Sorry to say, I think the shop was trying to sell off inventory. I had another shop order in the large TCX 2. The large has a 58cm top tube just like my road bike. The seat angle and head tube are all very close to the bike I ride now. It should be a perfect fit. I will even save a little money over the other shop. Thanks again