astrocub

i've decided that my next bike is going to be my first cross bike (i'm one of those skinny-tire
roadie folks). and after pouring over this forum and seemingly half of the www, i have decided
on getting a Redline Conquest Pro frameset to build up. now the question remains what size
frameset to get.

my road bike has a 59cm top tube (c-c) and i have a ~91cm inseam. looking
at the redline sizes, my initial thought was that a 58cm conquest would be a good fit.
the top tube dimension is nearly identical, but the stand-over height on the 58cm Conquest is 85cm!
this makes me concerned that with 85cm of stand-over height plus nobby tires, i'm going to be
cutting things close in a region that i don't want to.

https://www.redlinebicycles.com/modul...s-geometry.htm


so am i misguided in trying to match the top-tube measurement on my road bike? on a cross
bike do you tend to want a shorter top-tube to be less stretched out on the bike?

should i be concerned with the rather large stand-over height?

i realize that fit and comfort are personal preferences, but any help
would be most appreciated.
-m

SAB

There are several threads on this forum re: cross frame sizing. In general, cross frames have a higher bottom bracket than road frames (for extra ground clearance), thus the same length seat tube on a cross bike will yield a frame that feels bigger than a road bike with similar geometry. In addition, people I know who ride cross a lot tell me they like having a little more standover clearance (a lower standover height) as compared to their road bikes. I ride a 52cm road frame but I ridden cross bikes from 46cm to 49cm. Many cross bikes have a sloping top-tube, so the *effective* top-tube length is also important and this should generally be similar to your road bike. The practical upshot of all this is that, in general, one would ride a cross frame that is 1-2 sizes smaller than their road frame. The best way to find out is to ride one, of course.

astrocub

i've read most of the threads on this forum about sizing, but few have discussed top tube length
in particular. riding a cross-frame 1-2 "sizes" smaller is somewhat meaningless to me since frame
"sizes" are defined in random ways. while the size may be smaller on most folks' cross bike, how does
the top tube length compare????

SAB

In my experience, top tube lengths tend to be relatively long for any given size, as compared to the same size road bike. For example, my 52cm road bike has a 530mm horizontal top tube. My 46cm cross bike (a Surly Crosscheck) has an actual top tube length of 515, but since it slopes downwards towards the seat tube, the effective top tube length is listed as 529mm - essentially the same as my "larger" road frame. The 52cm Crosscheck has an actual TT of 545mm and an effective TT of 547, which would be way too long for me.

astrocub

okay, so it looks like redline might be a bit off relative to other manufacturers with
respect to their frame geometries. the 58cm (ST c-c) frame has a 585 TT (c-c) which nearly
matches my 60cm (ST C-T) size road bike's top tube. unfortunately redline does not emply
a sloping top tube, so the stand-over height is quite large in order to match my TT needs.
the redline sizing appears to be more like a road bike and less like other cross bikes.
looks like i will simply have to find either a 56cm or 58cm reline to test for size.....or opt
for another frameset that has a sloping top tube.

thanks for the help, SAB.
-m

BlastRadius

85cm standover with at 91cm inseam+shoes, that's plenty of standover (over 2 inches). You want the top tube (or eff. top tube) to be similar to your road bike. If you've been fitted to your road bike, that's where you'll comfortably put out the most power. When you mount and dismount, you don't do it over the top tube anyway and in a crash, you'll most likely fall over to one side where standover isn't a problem anyway.

astrocub

is there any argument for wanting a smaller or longer stem on a
cross bike? i would imagine that shorter stem (like 100mm or 110mm)
would be preferred for crisper steering.

Surferbruce

i'll say i love my new bianchi axis. for a prebuilt bike i think you can do a lot worse. for a frame only? i'd love a ritchey swiss cross...

astrocub

yeah, i like the axis too. but i prefer the redline conquest pro for two reasons:
(a) it has disc tabs on the frame and fork which is a nice plus.
(b) it comes standard as a double while the axis is built as a triple.

seely

Redlines run 2cm bigger than pretty much any other bike out there. You will often see a lot of them for sale on eBay because of this. In fact, my manager's 60cm Redline Conquest Pro is for sale for this very reason.

seely

Oh and if you want a sloping top tube, Giant's TCX frameset is where its at. Sweet carbon fork, and I believe it might be the only mass produced compact CX frame in existance. My manager bought one to replace his too large Conquest.

astrocub

yeah, i've been looking at this one too. it is a bit more expensive than the redline and
the shops near me don't have any in stock and are waiting to order 2005's in a few weeks.
giant does not have much info on their website about the TCX especially with respect to
geometry. i'm curious to see how much the 2005 frameset runs.

rollo

Beware: I ordered a 54. The shop I purchased it from told me the standover was 31.25". Perfect for me untill I threw my leg over it. Measured 32.25" to top of top tube.
Even Excel Sports lists the Standover for a 54 @79.8cm. Best to try one on. Silly me, I assumed stand over to be measured to top of top tube.

ddeand 

My limited experience (I'm 6'0", 225 lbs., 56 yrs old, inseam 33.5"):

I was looking for my first new bike since 1970 and decided on a CX bike. I tried a 2003 Lemond Poprad (57cm) that felt great. The components were low end, but the Reynolds steel frame was fantastic. I also checked out a couple bikes at a lbs sale - the main one I tried was a '04 Redline Conquest (not Pro) at 61cm. It felt exactly the same in terms of size as the Poprad with the exception of the top tube length which was a bit longer. It was a bit of a stretch, but I could have gone to a shorter stem to make it feel good. What surprised me was that the standover height and the overall feel (size-wise) was the same as the Poprad. I also tried a 58cm Specialized Allez that felt almost identical to the other two bikes in terms of size - it had a slope top tube, but measured the same as the Redline from stem to seatpost. Three different bikes, three different sizes, same feel size-wise. I ended up getting the Lemond because of the steel frame (the others were aluminum). No advice for you - just my experience.

Good luck, and have fun shopping!

Dean