Mountain Bike Sizing is Really Annoying

[anthonymaietta]

I get really annoyed with mountain bike sizing. They're all spec'ed/sold in SAE sizes and, and all us f'builders design them in SAE sizes (from what I've seen at least). However, all the components come in metric sizes with metric bolts. Why do we continue to refer to it as a 16 7/8" chain stay insead of a 42.8cm?

Garro, do you design in SAE or metric?

[nahtnoj]

I have no idea what metric means in MTB sizing. It's weird, because if I'm looking at a road bike for sale that someone lists as having a 23" top tube, I'm clueless on that too. Someone should take the lead on carrying us away from this dual standard.

[vulture]

Versed and proficient in SAE and Metric. I design my frames all in metric but often critical dimensions such as top tube length, seat tube length and chainstay length are more easily visualized and compareable to the customers in inches. When 29ers came around the customer education and obsession with chainstay length has promoted an understanding of that dimention in millimeters. I have no problem going between the units.

[sailor]

units are easy to convert if your not sure. TT length and seat angle will tell you how its going to fit, the big question is bar height because every different for has a different length so its hard to figure out.
I don't understand the obsession with short 29er stays, my mamasita has 455mm/18" chainstays which most consider long and i think its well balanced and have no problem getting the front wheel up, if anything longer would be better for climbing. Then again I'm 6'3" and like my seat pretty far back

[Ken Robb]

I guess the SAE sizing stems (pun?) from mtn. biking's origin when American balloon tire bikes were modified for riding off-road (search "repack hill"). Those "clunkers" came measured in inches and so things remain.

[962]

I've heard all of aerospace is SAE.

What I thought of when I saw this thread title was saddles slammed forward on zero-setback seatposts.

[spopepro]

This might sound facetious, but it's not really. Wouldn't it actually be more logical to move everything to SAE? There continues much confusion about the 31.8 and 31.7 clamp size (It's neither: 1.25") and so on. Not being a builder, I don't know if it's true all around, but it seems like most stock is drawn to SAE dimensions. Listed specs are rounded metric conversions.

[VertigoCycles]

It's all irrelevant anyway eh? I imagine you have to do some converting any time you use one of your americun masheen tools. BTW, you can toggle between the two units in BikeCAD if that's your program of choice.

[edoz]

I worked in a shop that did oil rig work, and whenever we got a print from Schlumberger (the French Haliburton) everyone would whine and cry 'cause it was in metric. I ended up building all those parts because I was the only one who didn't care. Once you get used to it it's easy to work in either system or even switch between the two seamlessly. Hell, I don't even separate my metric and SAE nuts and bolts. 6mm and 1/4-20 stand apart like they're painted different colors after a while. The only bummer is having an American lathe made in the 30's with lots of new accessories that are metric. Metric allen wrenches and standard 4 points.

[SteveP]

many remember the time when some company built space shuttle parts in sae when it was supposed to be metric?
funny shiite that i bet..
might have been vice versa anyway. dont remind me.

" errr, they seem kinda big and dont fit..."
"hmmmmm, let me go check the drawing..ill be right back..."
" doh"

[Human Epic Jolt]

yeah, lets standardise the bicycle! come off it.

[spopepro]

I know you said don't remind me... but I used this all the time as a math teacher trying to stress the importance of labeling your units. NASA loses 320 mil satellite due to metric conversion error

many remember the time when some company built space shuttle parts in sae when it was supposed to be metric?
funny shiite that i bet..
might have been vice versa anyway. dont remind me.

" errr, they seem kinda big and dont fit..."
"hmmmmm, let me go check the drawing..ill be right back..."
" doh"

[steve garro]

Garro, do you design in SAE or metric?

I mix them all up when building/thinking. my shop is actually split in 1/2 - one side is the framebuilding shite - pretty much all SAE, except my HJ jig, which is calibrated in metric. the other side is for bike mech/assembly & is all metric. I have to say that I do not think of frames at any point of manufacture as a "size." I pencil in the person's geometry & then draw the bike into it. people ask "what size is my bike?" to which I awnser "yours."
......Hell, how about spokes - MM's or gauge? - Garro.

[niedz]

I get really annoyed with mountain bike sizing. They're all spec'ed/sold in SAE sizes and, and all us f'builders design them in SAE sizes (from what I've seen at least).

suck it up wimp.
you know whats really annoying? a framebuilder complaining about something as stupid as that.
i will leave you with this--

25.4

[edoz]

......Hell, how about spokes - MM's or gauge? - Garro.

Ha! Last time I got spokes at my favorite lbs I asked for 14ga and the service manager tilted his head, stared at me for a second and said "how many millimeters is that?"

[anthonymaietta]

suck it up wimp.
you know whats really annoying? a framebuilder complaining about something as stupid as that.
i will leave you with this--

25.4

Haha, I'm perfectly capable of the conversion. Thank you for the conversion number , though.

Maybe I should have said mountain bike sizing is dumb, rather than annoying.

[Human Epic Jolt]

S, M, L + speed dial + cc machine.

[WadePatton]

"full suspension" rigs--fork travel described in mm whilst frame travel described in inches. it may have changed by now, but it used to be that way and i always got a kick out of it.

converting odd 32's or 64's to thousandths can be a pain. and by pain i mean a glance a chart or few strokes of pen/keypad.

i think of all frame dimensions in mm. convert if necessary. don't care for cm's. too coarse and easily confused with mm's atmo.

[rabo]

My local Advance auto part guy stated: "we don't do metric here", to wich I replied: "you be looking for a new job pretty soon then".

BTW I think NASA did not loose a sattelite because of a conversion but the Arriaane Euro rocket did.
The Hubble telescope mirror error was because of a conversion error as well , if I remember well.

[niedz]

Haha, I'm perfectly capable of the conversion. Thank you for the conversion number , though.

Maybe I should have said mountain bike sizing is dumb, rather than annoying.

hey im glad you arent the sensitive type