Cross frame vs mountain hardtail frame?

[rice rocket]

Anyone know if there's a real difference? Looks like the standards have mostly converged (135mm rear dropout spacing, 27.2mm seatpost, 1 1/8" steerer, 68mm BB shell width). With the sloping downtube, they look even more similar. Thinking of picking up a fork to dump on my Nashbar cross frame, since I already have this mostly built up.

http://www.nashbar.com/images/nashbar/products/medium/NB-MDBAF-NCL-SIDE.jpg

http://www.nashbar.com/images/nashbar/products/medium/NB-XF-NCL-BAR.jpg


Can anyone tell which is which? ;)

Comparing it with the specs of the similar sized Nashbar mountain frame, the headtube on the MTB frame is 10mm taller, and .5 deg shallower angle. Everything else looks almost the same. The extra height in the fork (uncompressed) should lift the bars to a more "mountain-like" posture.

[Peter P.]

Of course, wheel diameter is different unless the ATB is a 29er. Top tube lengths will usually vary as well due to the difference in handlebars and upper body position between the two styles.

But yes; they have merged somewhat.

[spartacus]

Go to Belgium for an answer.

[DfCas]

Most mountain frames, unless they are very large, are hard or impossible to shoulder due to the small triangle. The mtb wheelbase is longer due to longer stays and slacker head angles, the BB is usually higher, resulting in a higher saddle. All of these are generalizations, as cross geometry is all over the map, as is 29er geos.

[nahtnoj]

I think I'll just say that frames manufactured for Bike Nashbar which come in three sizes and wholesale for $25 are not representative of the CX and MTB race frame market.

[Jawn P]

I think I'll just say that frames manufactured for Bike Nashbar which come in three sizes and wholesale for $25 are not representative of the CX and MTB race frame market.

:)

[Nooch]

would the position of the canti posts be off, too, if you're looking at a 26" mtb frame vs a 700c cross frame?

[djg]

I'm not sure there are standards and, to the extent that there are, I'm not sure that they've converged all that much. Some cross frames use mtb spacing in the rear, but most don't. Most folks use wheels that could easily double as road wheels if the tires were changed. Any proper cross frame is going to have enough room inside the main triangle for shouldering a bike. And I'm pretty sure that "typical" geos vary -- I'm guessing, for example, that cross frame seat tube angles vary a bit, but that they vary around a different mean or median than mtb seat tube angles.

None of that answers the question how different two Nashbar frames are from each other or what's the best frame for you, for some cluster of purposes that's not just cross racing or mtb riding. But my cross bike is not an mtb bike.

[twhet]

Just some quick thoughts:

The difference in HT length would also have to account for the suspension correction on the mtb. and not on the CX frame.

The TT on a Cross bike is going to be shorter.

Rear spacing is different from road to mtb (touched on by dig) however, since the frame is disc compatible, I'll bet they are both 135mm (MTB) spaced.
It'll be interesting now that the UCI Regs have changed to see if CX bikes will migrate towards 135mm spacing for disc compatibility.

[rice rocket]

Oh right. I forgot most MTBs are built around 26" wheels, so the geometry wouldn't necessarily match up.


The Nashbar cross frame is more a touring frame, w/ the compact geometry. Which is what I want, really...I'm no crosser, just someone lookin' for a versatile frame.