schnee

Been looking at Cyclocross bikes. I'm not going to race them, I'm one of the people that's looking for an all-around bike to complement my MTB.

Odd thing I've noticed... the top tubes in most CX bikes are incredibly short. The top sizes for most CX manufacturers end at 58, and at most 60. For those bikes, oddly enough, it's rare to find a top tube length over 57cm. Many are even shorter - I've seen even 56.5cm top tubes on a 60cm frame.

My full suspension MTB, the Ibis Mojo, has a 62cm top tube, and it's definitely considered an 'all mountain' style frame, which puts you more vertical than a race-oriented cross-country frame. Even my 59cm Soma Rush has a ~58cm top tube.

I would have thought CX bikes would have *longer* top tubes than a comparatively sized MTB... yet they're a full 2-3cm shorter.

Is there something I'm not seeing here? Am I really going to have a more compact cockpit on a CX bike than on my MTB? Or am I just looking at frame manufacturers that cater to smaller riders? (PS, I'm 6'-3" with 37" sleeves - gorilla arms.)

seat_boy

Bikes made for drop bars typically have shorter top tubes than mountain bikes. This is because you spend a lot of your time stretched on the hoods or in the drops, where the forward curve of the bars gives you more room.

As a point of reference, I'm 6'3" with a 35" sleeve. A 24.5" mountain bike top tube feels fine, but the 23.3" top tube on my Gunnar Crosshairs feels too long--I have to use a stubby stem to make it work (although I like a bit more upright stance on the road bike, since I tend to ride the MTB more aggresively).

Eric

schnee

CX bikes seem to have even shorter top tubes than road bikes as a rule. Is that to put you in a more vertical position for off-road?

My Rush has a 58cm top tube and Bell Lap cyclocross bars. It feels a bit cramped on the road, especially since it's a fixed gear and I have to stand on the pedals so much up hills. If I get a CX bike with an even shorter top tube, are you saying that's by design because of the nature of the things a CX bike does?

hamr22

I agree with seat boy. Flat bar bikes often even have some rearward sweep to the bars, decreasing the effective reach. By contrast, drop bar bikes have a forward reach to either the drops or the hoods of about 7-10cm. If you are comparing flat bar geometry to drop bar geometry, you have to add about 10cm to the top tube length of the drop bar bike. All other things being equal, a 56cm-top-tube drop bar bike has the same reach as a 66cm-top-tube flat bar bike. Someone correct my math/logic if I've made a mistake.

schnee

K, I get it, but why are cyclocross top tubes all so short in relation to other road bikes? Is it to force a more upright riding position?

dragonmg

If you will be riding your cross bike on the road, then it makes sense to set it up like a road bike. But if you plan on riding it off-road, you'll find yourself constantly working yourself to more upright on the bars when you get into the trails and bumps. Pretty decent rule-of-thumb for cross bike fit is one cm shorter TT and one cm shorter stem than your typical road fit. With that in mind, cross bike stock TT's will typically be shorter than road.

Another thing to keep in mind, cross bike sales aren't as strong as road sales. Size runs of each model aren't going to be as extensive, so bigger sizes might miss out as a result. For instance, Trek only offers five sizes in their XO cross model (w/ max TT length of 56.5!), but seven sizes in the Madone. Check out the Jamis Nova, https://www.jamisbikes.com/usa/bikes/07_bikes/nova.html - seven sizes in a steel frame, w/ max TT of 60cm. Great line of bikes.

BDS

+1 on the Jamis Nova.

isotopesope

i think the main problem is what dragonmg is talking about... us tall guys get shafted by big production companies because they sort of skimp on how big they'll go, plus cross bikes get the shaft even more. though, cross bikes typically have a more upright position than a road bike.

i have found many larger frames tend to have a shorter top tube than the seat tube, which i personally don't mind one bit. my de rosa road bike is a 61 c-c seat tube with a 58.5 toptube. fits me perfect with a 115 stem. my douglas cross bike is a 60 with a 58 tt. i run a 120 stem flipped up and it fits just fine. i have personally found i like about 70cm of combined top tube and stem on my drop bar bikes. i don't compare the fit to my mountain bike to my drop bar bikes. my on-one inbred 29er is the XL size... which has a 25" top tube. that's 63.5cm! i run a 100mm stem on that, which is more than my 70cm target, but it still fits great. i think the difference between your hand positions account for that.

i also think those jamis nova's are sweeeet.

adrien

this was bugging me, so i went and measured my JTS. It's a 58, and the top tube is...58. It's got a pretty long stem, and, while i feel a little cramped sometimes, it is definitely more nimble than a roadie and a little more upright.

joe v

Yep, cross toptubes ARE short compared to road equivalents (crossers rarely ride 'in the drops'), that's why you have to be very careful in choosing your frame-size : forget the often heard credo to 'take two sizes smaller than a comparable road bike', or you risk ending up with a VERY short toptube (and having to use a VERY long stem to compensate!), I've bought a crossbike 2 sizes BIGGER than my road bikes and it's a very comfortable fit, thank you very much! Once again, no two bikes are the same, so try before you buy...

schnee

Well, I did a bunch more research, rode some bikes, then lo and behold a 2005 60cm Jake the Snake in awesome condition popped up on eBay. It's got a 59cm top tube, which is ~2cm longer than my current 'slighty too small' fixed gear. I got it for $900, and it's built up with some custom parts like a Thompson seatpost, XT hubs and Mavic 719 rims. Rock!

Thanks for all the feedback. It really helped clarify my thinking.

ldesfor1@ithaca

surly crosscheck has a 605mm toptube for a 60cm frame and a 610mm TT for a 62cm frame. this seems longer than those of bikes you are describing. check out surly's website for more info.

ldesfor1@ithaca

whoops... congrats on the Kona. enjoy!