Cross frame sizing chart: use this to estimate your frame size

[Sir Bikesalot]

I've gone through most of the posts where ppl have reported their height/inseam measurements and what frame size they are on (including model). Hopefully this will help those who are trying to determine what size frame they should be looking at.

I'll keep this document updated as more ppl post their data.

[Sir Bikesalot]

Just realized not everyone may want to d/l word documents so here's a screenshot instead.

[Cynikal]

I'm 70" with an inseam of 32" my poprad is a 54 and fits perfect.

[Sir Bikesalot]

At the risk of over-simplifying, I've plotted frame size versus height; seems to show a good correlation. To use, find your height on the bottom axis and then draw a straight line up to meet the red line, then move left to find your frame size. I would say accuracy is plus or minus 1 cm. Should get much better as I add more data. Keep the numbers coming!

[MillCreek]

I wonder if the chart would be better if you plotted cycling inseam vs. frame size. Can you try that and post it? It would be interesting to see the correlation there as opposed to height.

[Slow Train]

Bike: Specialized S-Works Tricross
Frame Size: 54 cm
Height: 70 in
Inseam: 32 in

Comments:
Nice upright riding position for urban commuting. Position is cramped when down in the drops. Suppose if I wanted to favor fast road riding over commuting I would change to a longer stem.

[Podolak]

My LBS has a 2007 54CM Tricross Sport. I rode it for a few miles and really felt comfortable on it. I felt like I was stretched in the drops properly and the standover was perfect. My height is 69 inches with a 32 inch inseam.

When I can finally afford it that is most likely the size I will buy.

[shapelike]

Bike: Devinci Tosca
Frame Size: M/55 (effective top tube length)
Height: 70"
Inseam: 33.5"

Obviously I've got long legs and a short torso. I opted for the Tosca because it's a "medium" frame with a really tall headtube (140mm). Paired up with a 90mm or 100mm stem (depending on the rise) I've got a comfortable reach and I don't have to deal with excessive drop down to the bars. I see a lot of steel frame sets out there that I'd love other than the fact that the miniscule headtube length basically makes the bike unrideable for me (I don't consider pushing the number of steerer tube spacers to the limit of safety + the highest rise stem I can find an acceptable solution ... I don't like maxing out frames to get the fit right).

[Sir Bikesalot]

MillCreek, frame vs inseam correlation is not as clear. Not sure why this is...my guess is that ppl choose sizes based more on comfortable reach to the handlebars rather than standover (as long as there's enough).

[Sir Bikesalot]

Here's the latest plot. For you statisticians, Rsquare = .71 (vs .67 last time) Which means the line fit (in red) is getting more accurate with more data, so keep the numbers coming!

[MillCreek]

MillCreek, frame vs inseam correlation is not as clear. Not sure why this is...my guess is that ppl choose sizes based more on comfortable reach to the handlebars rather than standover (as long as there's enough).

Wow, that is interesting. I wonder if traditional vs. compact geometry can also account for the differences. Although I have not done an extensive study, it is my impression that a lot of today's cyclocross bikes are with compact geometry, in conjunction with so many of today's road bikes. I am a traditional geometry fan, myself.

[Sir Bikesalot]

Actually I couldn't help but notice that if I took out the Surly Cross Check data, the frame vs. inseam plot turns out much better. Maybe because Surly measures their frame from BB to TT instead of seat post?

[flargle]

Rsquare = .71 (vs .67 last time) Which means the line fit (in red) is getting more accurate with more dataThis interpretation of R^2 is common, but wrong.

R^2 is the percentage of the variance in frame size explained by rider inseam. It needn't increase with an increase in sample size. Even if you gathered data from a million riders, there would still be points scattered around the regression line because of other factors--personal dogma, bike geometry, frame availability, etc--which are responsible for roughly 30% of the variance in frame size.

[flargle]

Actually I couldn't help but notice that if I took out the Surly Cross Check data, the frame vs. inseam plot turns out much better. Maybe because Surly measures their frame from BB to TT instead of seat post?My suspicion is that people are talking about two different inseam measurements, one being public bone height, and the other being the pants inseam length.

[jasonguard]

Why doesn't your chart go any lower than 30"?

The inseam measurement on my pants is 27.5". I have to buy 30" pants and then have them altered.

[MillCreek]

My suspicion is that people are talking about two different inseam measurements, one being public bone height, and the other being the pants inseam length.

Always a distinct possibility. Many people are unclear as to the difference between the 'cycling inseam' and the 'pants inseam'. I always quote my cycling inseam of 32", as opposed to my pants inseam of 30".

[Sir Bikesalot]

Why doesn't your chart go any lower than 30"?

The inseam measurement on my pants is 27.5". I have to buy 30" pants and then have them altered.

Here you go. Looks like you might want to start with 48-50cm. If you're closer to 5'6" I'd go with the 50cm, if closer to 5'4" then 48cm. If you're taller than 5'6", then you have a long torso and should look at possibly 52cm even.

[Sir Bikesalot]

This interpretation of R^2 is common, but wrong.

R^2 is the percentage of the variance in frame size explained by rider inseam. It needn't increase with an increase in sample size. Even if you gathered data from a million riders, there would still be points scattered around the regression line because of other factors--personal dogma, bike geometry, frame availability, etc--which are responsible for roughly 30% of the variance in frame size.

Good info about Rsquare. You're right that it needn't increase with sample size, however, I think we're in a regime in which the current sample size is insufficient to represent the actual mean and variation of the parent population. The fact that Rsquare is increasing with more data so far is encouraging though, and indicates to me that the linear dependency is strong enough to show through the other factors you mentioned that contribute to the variance.

[El Duke]

All I have to add is that this is great and thanks for doing this Sir Bikesalot. I'll post my data once I get my frame picked out. I'm 6'1.5" and have an inseam of 32, I'm guessing between 56-58 cm size frame (58cm top tube length should fit me) will work. I rode a 58cm Motobecane fantom cross last night on the road and it was pretty comfortable. I'll have to try some mounts and dismounts later this weekend to see if it will work.

[Sir Bikesalot]

Thanks El Duke, my hope was that ppl would find it useful for narrowing down their possible frame size and it looks like it might actually be working!

Here's the latest plots. Use the following preocedure to get the most accurate estimate: 1) Find your frame size using both plots; 2) average the two numbers to get the final result. For example, I come out with 59cm (6'2", 35").

[massocrat]

This is a great attempt at some difficult data gathering/crunching. If you'd like to add the Fuji Cross Pro (and Comp), the Lemond Poprad, and the Spec TriCross Comp, here are my meausurements. I am a 34.5 true inseam (but 32 in pants), and 6'0. I just bought a 58 Cross Pro. The 56 was ok, but the 58 was absolutely ideal. Same with the TriCross-58. 57 in the Lemond. Hope this helps. Good job!

[El Duke]

Okay, I am 6'1" and just finished the fit calculator on competitivecyclist.com. Here's the results from my body measurements:

Measurements
-------------------------------------------
Inseam: 33.75
Trunk: 25.625
Forearm: 14
Arm: 26.625
Thigh: 26
Lower Leg: 22.75
Sternal Notch: 60.75
Total Body Height: 73


The Competitive Fit (cm)
-------------------------------------------
Seat tube range c-c: 55.5 - 56.0
Seat tube range c-t: 57.2 - 57.7
Top tube length: 54.9 - 55.3
Stem Length: 11.5 - 12.1
BB-Saddle Position: 73.4 - 75.4
Saddle-Handlebar: 54.7 - 55.3
Saddle Setback: 6.8 - 7.2
Seatpost Type: SETBACK


The Eddy Fit (cm)
-------------------------------------------
Seat tube range c-c: 56.7 - 57.2
Seat tube range c-t: 58.4 - 58.9
Top tube length: 54.9 - 55.3
Stem Length: 10.4 - 11.0
BB-Saddle Position: 72.6 - 74.6
Saddle-Handlebar: 55.5 - 56.1
Saddle Setback: 8.0 - 8.4
Seatpost Type: SETBACK


The French Fit (cm)
-------------------------------------------
Seat tube range c-c: 58.4 - 58.9
Seat tube range c-t: 60.1 - 60.6
Top tube length: 56.1 - 56.5
Stem Length: 10.6 - 11.2
BB-Saddle Position: 70.9 - 72.9
Saddle-Handlebar: 57.2 - 57.8
Saddle Setback: 7.5 - 7.9
Seatpost Type: SETBACK

I have found a good deal on a 56 cm Ridley Crossbow frame, which I am pretty sure I will be able to set-up for a good fit. I suggest that everyone at least try the fit calculator at competitivecyclist, just for knowlegde sake and to take the guess work out of sizing/fitting.

[climbhoser]

This is interesting, and I have a question.

I'm looking at an IRO Rob Roy. Tony says I should get the 58. I'm 5'10" with about a 32 cycling inseam (I wear 30 pants). I've got a pretty average torso, and actually shortish arms.

I know IRO measures differently, and Tony has this frame's S/T c-c listed as 54 cm and a 32" standover. That puts me restin' the package on the top tube when I straddle the bike.

What do y'all think?

[MillCreek]

This is interesting, and I have a question.

I'm looking at an IRO Rob Roy. Tony says I should get the 58. I'm 5'10" with about a 32 cycling inseam (I wear 30 pants). I've got a pretty average torso, and actually shortish arms.

I know IRO measures differently, and Tony has this frame's S/T c-c listed as 54 cm and a 32" standover. That puts me restin' the package on the top tube when I straddle the bike.

What do y'all think?

Hmm, you and I sound like pretty much the same size, and I have a sleeve length of 32/33". That being said, I wonder if the frame you are looking at is a bit on the large size. Depending on the geometry and how they measure, I would probably be looking at the 54 to 56 cm. range.

[flargle]

I'm 5'10" with about a 32 cycling inseamI'm skeptical of these measurements. 32" seems low for somebody of your height.

My recommendation is to take a careful set of measurements by closely following these instructions:
http://zinncycles.com/fitsystems/DimensionPage.aspx
Enter them here:
http://zinncycles.com/fitsystems/default_ie.aspx
And then post the results.

[MillCreek]

I'm skeptical of these measurements. 32" seems low for somebody of your height.

My recommendation is to take a careful set of measurements by closely following these instructions:
http://zinncycles.com/fitsystems/DimensionPage.aspx
Enter them here:
http://zinncycles.com/fitsystems/default_ie.aspx
And then post the results.

I am of the same height, cycling inseam and dress slacks inseam. We do exist.

[JustBrowsing]

I'm skeptical of these measurements. 32" seems low for somebody of your height.
I'm a little over 5'11" and have a cycling inseam of 32". My pants inseam is 30" or 32" depending on the fit.

[flargle]

I'm 6'0" and my pubic bone height is 35". Y'all weirdos should be swimming, not cycling!

[climbhoser]

6' with a 35" inseam. You're 2 inches taller with a 3 inches taller inseam. Not that out of the ordinary, I think I'm plenty normal.

BTW I am guesstimating my cycling inseam, but I could be 33" instead of 32" on the cycling inseam. I'm basing this on the fact that my satchel likes to hang unimpeded, so that means 30" pants (the maestro can slide to the side). I can't think my bags hang more than 2-3", which leads me to conclude I have a 32-33" cycling inseam. I should probably measure it, but I think it's a fairly astute guesstimate.

Swimming is too tough...I was a wrestler, and a damn good one. But cycling is where it's at now.

Tony at IRO said he rides a 60 cm and he's 6' with probably a 34-35" cycling inseam. So, obviously they measure differently...I just wanna know if anyone else has that experience and if it's way off base to go with the 58 cm bike recommendation.

[flargle]

Tony at IRO said he rides a 60 cm and he's 6' with probably a 34-35" cycling inseam. So, obviously they measure differently...I just wanna know if anyone else has that experience and if it's way off base to go with the 58 cm bike recommendation.I was looking at the IRO site and it looks like the sizing is based on a traditional (horiz top tube) geometry. So the 58cm frame seems not unreasonable for a guy your height. But my initial recommendation stands: Do the measurements, use the online calculator, and compare the results with the IRO frame dims.

[flargle]

I should probably measure it, but I think it's a fairly astute guesstimate.I was correct to be skeptical about your measurements.

"Standing up straight with your feet 2" apart, pull a leveled broomstick or a carpenter's 3-foot level firmly against your crotch, holding it with one hand in front of you and one hand behind you. It should be level and as snug as if you were straddling a fence rail with your legs hanging down off either side. The goal is to fully compress the soft tissue up against the lower edge of the pelvic bone."

[climbhoser]

You don't think my nutsack hangs 2-3"?

J/K I'll be measuring tonight

[nikvdw]

If you want to add a recent Fuji Cross Pro Comp
69" tall, 32" inseam, 54 framesize

and from Massocrat other recent purchase
72" tall, 58 framesize

[D0ugB]

surly cross check 62cm
78" tall 36.5" inseam (cycling)

just to completely ruin the curve

[andmalc]

I don't think this method will always work. I'm height 71", inseam 33 (right up to crotch), but I need a 58" frame. Why? My long arms.

I don't yet have a cross bike so not contributing my figures.

[Richard8655]

Help!

I'm 70" tall with cycling inseam 32" or so (maximum into crotch) and planned to go with a 2007 Specialized Tricross Comp 56cm frame. I found the smaller 54cm frame just doesn't give me the pedal extension my legs yearn for. It's as if I can kick out to the max with the 56cm larger frame that I can't with the smaller.

Well, I went into the LBS for a customized sizing. After their calculations, they informed me that I'm on the shorter torso and longer inseam side of things, and that a 56cm would be fine for the legs but impossible for the arms. They said I must go with a 54cm and they'd swap to a shorter (nearer) handlebar extension to correct for the apparent arm overreach stretching to the Tricross's lower grips.

I test rode both the 54cm and 56cm, and the 54cm seemed cramped in the legs, despite their telling me the seat can be adjusted incredibly high. Maybe I'm old school, but I just feel weird riding a relatively tiny frame (my perception) with the seat extended a foot or more.

My dilemma - go with the more comfortable 56cm for legs and swap to shortest possible handlebar extension and live with some stretching, or take their advice and go with 54cm more cramped legs and smaller frame feel and raise the seat high?