Originally cross bikes were just old road bikes that had canti's added to them so that they could fit in the cross knobbies. The result of this is that it essentially lifted the bottom bracket the extra radius increase of the tire thickness, perhaps an inch or so.
Somewhere the idea became popular that a cross bike needed more clearance. So they lifted the bottom bracket still higher. There's some good reasoning behind this - the ground is not flat where you ride a cross bike and more bottom bracket clearance gives you more clearance for the pedals over broken ground.
In order to retain the same stand-over height this made the seat tube shorter. So in those types of cross bikes the fit is a bit funny.
Remember, you would usually want a slightly less stand-over height because off-road you may have to dismount on the side of a hill or some such and it is nice to have a little more crotch clearance. Add to that the higher bottom bracket and the higher ground clearance and you now are faced with some guy who normally rides a 58 cm road bike is now getting a 53 cm cross bike.
But only for some cross bikes.......
Other cross bike makers had other ideas. Tall bottom bracket bikes set the center of gravity higher and they don't feel as maneuverable as road bikes. They also don't corner as easily and they are clumsier in slow tight stuff.
So another school of thought makes a bike with a lower bottom bracket. When you put knobbies on these bikes it lifts the bottom bracket up to the original road bike height. These bikes feel a lot better to road bike riders. Mountain bike riders are used to the feel of high center-of-gravity bikes and might not even notice it.
Whether or not these bikes are a bit more manageable in close quarters is a matter of opinion more than fact. Let’s face it, feel is not everything and some relatively minor quirk of geometry really doesn't make a great deal of difference in a 20 lb-ish bicycle that you can throw over your shoulder. But people have tastes and some people are particular about one thing while others might not even notice.
Because you STILL want the additional crotch clearance most makers will design the top tubes slightly longer than a road bike would be. That means that if you, for instance, normally ride a 58 you might want a 56 in this sort of design.
A third school says that they want to duplicate a road bike down to the last detail. World Championship ‘cross bikes from the late 70's and early 80's were like that. They were built to race so they didn't give a flick about extra crotch clearance, you'd ride the bike through anything possible and you'd run everything else. On these bikes, they had the low bottom bracket and the normal length top tube so you'd fit your normal road size. Some times the top tube would even be a little short like on a touring bike in order to get you a little more upright for better visibility.
Now let's add some further complications. Are you intending to race or recreational ride or both? It makes a difference to the way the bike will fit.
Cross racers will want shorter chainstays and tighter geometry to make steering lighter in nasty mud and gunk. They want lighter bikes because they spend more time carrying them than a recreational rider. Lighter means more expensive and more fragile. Of course fragile is relative and cross bikes have to be more heavily built to begin with because of the much higher impact loads encountered in racing.
On a recreational cross bike you want it to be a little larger and maybe with longer chainstays since you can then use it for commuting or touring and there will be heel clearance for pannier and more overall comfort. You would normally have a shorter and higher stem so that you aren't tilting your head WAY back to see forward.
Now this does give you a whole lot of confusion over the correct size bike to buy. It makes buying a cross bike you don't know really difficult unless you're standing next to it or have complete specifications and a full knowledge of bike fit. So you should usually buy a cross bike from a dealer where you can sit on it and actually take it for a test ride. And that can be a challenge in this day when most bike shops stock low end mountain bikes and the occasional road bike.
And that's what this forum is for. Ask questions and don't forget to add your crotch measurements and height.
The BikeForums Team
-adv-
This is an archived thread, you can find the full version of this thread, with images, links and more content here.
i just bought a surly cross-check frameset. i normally ride a 54ish cm road frame, but ordered a 52cm cross check, to run fatties and still have the standover.
my gf also got a cross-check. she rides a 48cm road frame, got her a 46cm cross-check, but she had no standover on it, so i had to get her the next size down, a 42! tiny considering she rides a 48!
we will be racing SS CX this upcoming season, i know the cross-check isnt at all out race bike, but the flexibility of it is nice. we plan on touring with them someday, so its a good bike to have in the stable.
nad45
Here is a couple of pretty helpful articles for 'cross equipment selection if you are racing 'cross
http://www.cycle-smart.com/Articles/find.php?search=31 bike fit article
http://www.cycle-smart.com/Articles/find.php?search=32 Tire and wheel choice
http://www.cycle-smart.com/Articles/find.php?search=33 other stuff
I have been to one of Adam's Clinics and it was really top notch and I learned a ton.
Can't wait...first 'cross race of the season is on Saturday
optimus78
Good info. I am looking into buying my first cross bike (never had a road bike either). I am 6'3" and have a 33.5 inch inseam. I weigh 184lbs. I am looking at the Fuji cross '05 model. There is a 61cm at a nearby lbs that I am trying out tonight. What size do you recommend?
DRLski
Here is a couple of pretty helpful articles for 'cross equipment selection if you are racing 'cross
http://www.cycle-smart.com/Articles/find.php?search=31 bike fit article
http://www.cycle-smart.com/Articles/find.php?search=32 Tire and wheel choice
http://www.cycle-smart.com/Articles/find.php?search=33 other stuff
I have been to one of Adam's Clinics and it was really top notch and I learned a ton.
Can't wait...first 'cross race of the season is on Saturday
I was gonna go to Adam's clinic this weekend but kind of caught me off guard with the price, I'll have to save up for next year.
Great post, didn't know most of that. Good stuff. Should be a sticky.
nad45
Good info. I am looking into buying my first cross bike (never had a road bike either). I am 6'3" and have a 33.5 inch inseam. I weigh 184lbs. I am looking at the Fuji cross '05 model. There is a 61cm at a nearby lbs that I am trying out tonight. What size do you recommend?
What size road bike do you ride? I would try to match up the Effective TT length of your road bike and find a 'cross bike that is the same and shorten the stem by 1-2 cm.
nad45
I was gonna go to Adam's clinic this weekend but kind of caught me off guard with the price, I'll have to save up for next year.
Great post, didn't know most of that. Good stuff. Should be a sticky.
If you ever get the chance to go to the clinc do so. I went 2 year ago and have organized clinics with Cycle-Smart coaches for the past 3. Worth every penny if you want to perfect your technique and have a good weekend.
yasono
I am looking to build a Surly Cross-Check with either a size 52 or 54 frame. I am 6'0 tall with ~32" inseam and I can fit comfortably on an 18" mountain bike.
I plan on using the bike mostly for commuting, though perhaps I may get some off-road and touring use out of it as well.
Recently, however, I found a good deal on a 56 frame, but I don't know if this would be a little too large for comfort. Any suggestions?
legalize_it
a 52 or a 54 sounds too small for someone 6'0! i have a cross check in 52cm and i am only 5'8". but the best thing to do would be to standover it... go to surly's website and check out the geometries. the TT lengths between a 54-56 are not a lot longer.
cyclintom
Good info. I am looking into buying my first cross bike (never had a road bike either). I am 6'3" and have a 33.5 inch inseam. I weigh 184lbs. I am looking at the Fuji cross '05 model. There is a 61cm at a nearby lbs that I am trying out tonight. What size do you recommend?
I would expect you to be looking at a 58 cm myself but as I noted, individual bike manufacturers make each bike differently. I'm an inch taller than you and have legs 2" longer. I'm riding a Raleigh Team Cross 59 cm and it might be the slightest pinch large. But I ain't changing since it's a great bike and more than worth the price.
cyclintom
I am looking to build a Surly Cross-Check with either a size 52 or 54 frame. I am 6'0 tall with ~32" inseam and I can fit comfortably on an 18" mountain bike.
I plan on using the bike mostly for commuting, though perhaps I may get some off-road and touring use out of it as well.
Recently, however, I found a good deal on a 56 frame, but I don't know if this would be a little too large for comfort. Any suggestions?
I would have though that a 56 was more up your alley. If all you're finding is a frame it's pretty hard to tell unless you can talk to someone around your own size that has one.
Thor29
I am looking to build a Surly Cross-Check with either a size 52 or 54 frame. I am 6'0 tall with ~32" inseam and I can fit comfortably on an 18" mountain bike.
I plan on using the bike mostly for commuting, though perhaps I may get some off-road and touring use out of it as well.
Recently, however, I found a good deal on a 56 frame, but I don't know if this would be a little too large for comfort. Any suggestions?
Holy clown bike, Batman! That is way too small. I'm 6'1" and a 33" inseam and ride a 60cm Crosscheck. It fits me perfectly. You definitely don't want one smaller than 56cm, 58cm is more likely.
trick
So that's why the Poprad felt so tall. Thanks! saves me asking! :)
now, the next question, then, is which frames fit into these different schools of thought?
Martyr
On a recreational cross bike you want it to be a little larger and maybe with longer chainstays since you can then use it for commuting or touring and there will be heel clearance for pannier and more overall comfort. You would normally have a shorter and higher stem so that you aren't tilting your head WAY back to see forward.
I have recently built an il Pompino - which would fall into the recreatinal catagory. I mainly use it for my daily commute of 50km round trip, with the occassional off-road excursion. I intend to race it next year when we get some races going down here, but given that I ride fixed gear, I would just be the joker in the pack so would be for pure amusement value. In any case, I can't afford another bike!
my inseam is 85.5cm and I am 181cm tall. My frame size is 57cm which is the same size as my road bike, a Gios compact pro. I could ride a 56cm but need the frame size since my torso is long relative to my leg length. The Gios has a short Top Tube while the il Pompino has a long Top Tube.
The next frame size below ( in the Pompino range ) is 54cm and i feel now that i am a bit between these sizes, although am adequately setup for my intended use of this bike.
Presently my il Pompino has a 120mm stem, but I should have 130 to 140mm. Had I chosen the 54cm il Pompino them my stem length would likely have been well in excess of 150mm and i believe that this would be too long for offroad work.
Any thoughts?
SAB
This has been said many times before on this forum, but a good rule of thumb is that your cross frame should be at least 1 or 2 sizes smaller than your road frame. Probably the best single measurement to match on both your road and cross bike is EFFECTIVE top tube length. Most cross bikes have sloping top tubes, so the effective top tube length is the equivalent top tube length if it were horizontal. I ride about a 52cm road frame, with a 52.5cm effective top tube. My Cross Check is a size 46 with a 52cm effective top tube. The bottom bracket is higher and the frame is slightly longer as compared to my road bike. I use it as my travel bike and have it outfitted with canti brakes and Ultegra triple group. I find it handles very well, epecially down hill and through high speed turns.
FraAngelico
I don't have a road bike. I'm 6'2" , 35" inseem. Average proportions. What crosscheck is good size for me? 58 or 60?
ccharles
FraAngelico, I would get a 60cm if I were you. I am 6'2" with a 37 inch inseam, I recently had to make a similar decision between a 58cm and 61cm Bianchi Axis. After much deliberation and research, I went with the 61cm, and I am sure it was the right choice. I felt cramped on the 58cm, and most of the information from more reputable sources that I came across said that the advice to size it down a lot from your road size is bunk, and you should just get the frame size that fits you. If you don't know your road frame size there are a few formulas around on the web, one more extensive one can be found on the wrench science website, although it told me I needed a 66cm road bike, which seems a bit big.
deathintransit
I would imagine that if your intended riding was to involve lots of racing that you would opt for the slightly smaller frame for faster mounts/dismounts.
If you don't plan to race, or race much, then you could get away with a more traditional fitting frame/bike that you will (hopefully) be staying on for the duration of your fun.
Maybe if you have a history of BMX racing this may make since?
-Just stirring up the pot a little more.
TSG
Hi guys, I just began racing cross and using my vintage Ritchey 87' mtn bike, no shocks. Anyway, I am looking to build up a cross bike but have no idea what frame size. My road bike is a women's specific compact frame and I love it, really want the same performance on the cross bike (size wise). Please advise...
Height 5'3
Inseam 29
Thanks,
TSG
Scott H
I would imagine that if your intended riding was to involve lots of racing that you would opt for the slightly smaller frame for faster mounts/dismounts.
If you don't plan to race, or race much, then you could get away with a more traditional fitting frame/bike that you will (hopefully) be staying on for the duration of your fun.
Maybe if you have a history of BMX racing this may make since?
-Just stirring up the pot a little more.
Help me understand: I'm coming up on a barrier, lift my butt off the saddle with all my weight on my left foot. How, exactly, does a smaller frame help me do that faster? I'm going to set my saddle height relative to the bottom bracket the same h eight on any bike I ride. How is going to have an extra cm of seatpost showing on a smaller bike going to help???
ccharles
I agree with ScottH. For a dismount, you swing your right leg around the back of your bike, over the rear wheel, so the frame size makes no difference whatsoever. Then for the remount, you jump onto your seat, again from behind, so the frame size again does not come into play. I think the benefits from riding a frame that fits you properly and that you are not cramped on will far outweigh any real or imagined benefits of having a frame that is too small for you.
SpongeDad
I'm still having a hard time figuring out what size frame I would need. I have a 31.5 inch inseam and my road bikes have about 54.5cm top tubes.
Any CX bike I see with a 30 inch standover has a really short top tube. Any thoughts?
FraAngelico
thanks ccharles, i think i'll go for the 60. I'm trying to choose between the Bianchi Volpe and the Crosscheck. I can't decide. I can get a volpe for $750 and crosscheck for $900.
jfmckenna
I read somewhere that the old cross bikes were made with higher bottom brackets because of the clips on the pedals. Racers would often ride a little bit on the under side of the pedal before a dismount for example and the clip would scrape the ground. With advent of clipless pedals they have gone back to normal. So I will agree with some posters here that the TT length is really where its at so long as you have the proper stand over.
My Trek is a 61 and I am 6'3"
Martyr
So I will agree with some posters here that the TT length is really where its at so long as you have the proper stand over.
which leads to the obvious - what is considered to be optimum stem length? Is there advantage in a shorter stem for off-road work? my guess is that 120mm is a good length and that once you are requiring in excess of 140, your TT is too short.
Any ideas?
marty
seniorspeeder
The issue of standover height has nothing to do with getting over barriers. Standover height comes into play during other riding conditions; getting stuck on a steep hill, catching a pedal on an off camber turn where you are forced off the saddle and onto the top tube. There are times in a cross race and just riding off road where you may be forced off the saddle and have your feet on the ground and scoot your bike. It is those situations where a little more room is important.