650b on womens/small frames

[vqdriver]

there always seemed to be a lot of reluctance to adopt 650c wheels on the smallest of frames, and i'd always assumed it was the lack of wheel and tire choices.
with the popularity of 650b in mtb, coupled with the trend of road discs, it appears a very nice set of wheels is not difficult to find or build. road tires are certainly there, if not plentiful. but i wonder if framebuilders are more accepting of this size on their smallest of frames?

yes, i'm sure it would change the handling and ride characteristics. but it's not like super steep st angles or nutty forks were ideal either.

just wondering out loud

[deechee]

Would it make a difference to design with a 650b?

From SheldonBrown
"If you are going from a very narrow 622 (700C) tire to a fairly wide 584 (650B), the difference may be minimal. For instance, a 19-622 (700 x 19C) tire would theoretically have exactly the same outside diameter as a 38-584 (650 x 38B)."

http://www.bikerumor.com/wp-content/uploads/2012/06/650B-wheel-size-comparison-diagram.jpg

ps. I loved my 650c tri bikes. One was a Serotta but the fact that I could never count on others for a spare tire/tube was a royal pain.

[Mark McM]

As noted, a 700c wheel with a narrow tire, a 650b wheel with a medium width tire, and a 26" (MTB) wheel with a fat tire are all very similar in outer diameter (they are all roughly 26", or 330 mm in outer diameter).

As far as bike design and fitting, there is nothing magical about 700c. Using smaller 650c wheels does require some differences in various dimensions, angles, etc. in comparison to 700c wheel bikes. Since most people in the bicycle industry operate from rote (i.e., do things the same way as they always have), they may not be able to adjust for the changes required for 650c wheels. But someone who really knows what they are doing should have no problem. So the only reluctance that should remain to smaller wheels is wheel/tire availability.

[pavel]

there always seemed to be a lot of reluctance to adopt 650c wheels on the smallest of frames, and i'd always assumed it was the lack of wheel and tire choices

Speaking only from my experience, but tire choices will still be the limiter. On a very small frame / for very small people, standover is a big deal. You and I probably dont think about it much (I dont think about it at all actually), but it is. One of the reasons that my gf rides a 43cm bike with 650c is because the standover is correct for her using 571/650c with a 23mm tire.

650b is only a little bit bigger than that, but just about everyone out there is riding a 650x42 tire if they are using 650b for a road type application. This brings you back to the same size as a 700cX23 wheel/tire, which is the supposed appeal - that you don't change your geometry but gain comfort and lose rolling resistance.

Now, what is the smallest 650b road tyre available? Is it 32? If its smaller than that, its not by much. I dont see anything on Compass' site smaller than 32 and I think they are more or less the road 650b experts, right?

So in my scenario, 650b with 32mm rim is already 2.2cm higher from where we started (584 - 571 + 32 - 23 = 2.2cm), nearly an inch taller than 650c with 23mm. Which puts the toptube all up in her business. Which, as she has informed me, she does not like.

Standover is issue one. Issue 2 is length. Again, in my case, she needs a short top tube, I think her ideal is like 48cm or something ridiculous. But, at least with 650c, the geometry of the bike can be set up such that it is still 'within reason' in terms of what you and I think of in traditional road geometry. I think her 43cm trek is something like 74 STA and 71 HTA. The reach measurement is very short, its like 355 or something.

Now go back to your 650bx32. Now to accomodate the extra 2.2cm we are gaining not only in height but also in horizontal diameter, now either the top tube has to be longer because we are just going to stretch the bike out to preserve the geometry - so no go for us - or you have to do slacken the headtube, sharpen the seat tube, which will change the handling characteristics and probably have various other unfavorable consequences like toe overlap.

I realize that I'm talking about a corner case, but even for women who are not as XS as my partner, this is all still a problem. Take a look at any really small frame - lets consider the specialized amira, a "women specific" 700c bike.

http://cdn.sigmasport.co.uk/media/TA/925/522/Miscellaneous/Specialized-amira-2014-geometry.jpg

first of all the angles for those first two sizes are terrible. Transpose that into whatever bike size you ride and I guarantee you're going to be pissed off. Second of all, imagine you are a person who needs to be on that 44cm or 48cm bike frame. Now imagine you are a woman and proportionately you also need shorter reach in relation to your overall "frame size" and certainly shorter than the reach of a man of the same size.

Does it make sense to you that the shortest top tube is already 498mm? This chart doesnt even show reach, but you start looking at the reach numbers for some of these frames and they are just bonkers. Another random example - my friend's kid is on a 42cm surly straggler. in the 42cm size, the reach of this bike is 1cm shorter than the reach on my 54cm cross bike with 'normal' angles. :eek:

Here is a better Amira chart.
http://bicyclesportshop.com/images/library/features/spec_amira_compact_geo_12_m.gif

So the 44cm, the SMALLEST women's bike made by the arguably biggest and loudest name in cycling, has a reach of 365mm. My 54cm cross bike with normal geometry - 72HTA and 73STA is 373mm. Yes, some of that we can fix with stems - but does this make sense? It's absolutely crazy. The woman who needs a 44cm sized bicycle gets a reach length thats less than 1cm of a difference from a 5'9" man. And coming back to my specific example - my partners 43cm trek with a 355 reach measurement - this Amira gained an entire centimeter of reach JUST by going to 700c tires and increasing the bikes "size" by 1cm. I think one would be very hard pressed to find such an extreme reach change correlating to such a small frame size change anywhere else.

Anyway I digress.

Back to tires - so ok, in the case like the specialized amira or some similar "small" or "extra small" bike frame - yes, in this case it would TOTALLY make sense to use 650b rather than 700, but only if again, you could get the tire sizes you wanted.
With 650x32 being the smallest I am aware of currently, this saves you 1cm only over a 700cx23 (assuming that650bX42 = 700cX23). Now, 1 cm saved in height is good because it also means you can make your wheelbase shorter by 1cm and start working on making your angles slightly more normal and hopefully start getting reach under control. If you had tires down to 26mm or even 25mm, you could design bikes around those sizes and really, REALLY improve the current market offerings.

Meanwhile, my partner will continue to suffer from the ever decreasing popularity of 650c and continually shrinking market.


Even more so (and actually should be the overarching theme here) is that realistically, the cycling industry for the most part doesnt give a ���� about women. If they did, we would not be having this conversation about 650c never catching on because of limited tire choices.

I'm far from an expert on bike fit. My qualifications are as follows: I have a basic understanding of geometry and trigonometry, I like my girlfriend a lot, I like bikes and I also have eyes and ears. So if any of the above is so goddamn obvious to me. I find it hard to believe that no one in the industry has thought of any of this before.

[Tickdoc]

My wife sure loves hers!


http://img.photobucket.com/albums/v234/Handgod/193FD179-4BE0-489D-9033-D4AA3B64EBD5_zpsacunzotk.jpg

The kyseriums are plenty tough for her small frame, too. Only thing that look really out of place are those ugly ass ergo drop bars.

One of these days I'll upgrade her tires to something plusher, but for now the gatorskins are fine. They hold good air pressure for eons, too. Need to find out what kind of tubes are on it.

[pavel]

Now THAT is a fine bicycle. If you ever sell, I'm buying.

[vqdriver]

for comparisons sake, we'd be comparing the same tire sizes, so 700x28 vs 650bx28, etc. which, incidentally, is the smallest tire i've seen and i doubt it's a 'racey' tire.

really, the thought crossed my mind because with 650b being embraced by the mtb side, there's actually quite a few very nice rim choices. coupled with the road disc trend, you could conceivably just swap wheels with an xc type bike.

but again, i'm just wondering out loud.

[pavel]

interesting, just looked that up and I see a ritchey tire in that size.

[goonster]

So the 44cm, the SMALLEST women's bike made by the arguably biggest and loudest name in cycling, has a reach of 365mm. My 54cm cross bike with normal geometry - 72HTA and 73STA is 373mm. Yes, some of that we can fix with stems - but does this make sense? It's absolutely crazy.

Yes, it's crazy, and the only solution is smaller wheels.

46.5 cm eff. TT, 73 deg STA, 26 x 1.25 Paselas:

https://farm5.staticflickr.com/4141/4856869541_2e994b7571_b.jpg