I’ve searched and read quite a few postings and various websites and it would seem that on a mixte the effective top tube length is the determining factor on sizing for a frame.

Over the weekend I picked up a built Buena Vista with a 42cm frame with 650b wheels. My girlfriend is 5’7” with a slightly longer torso than legs. I would assume 50cm, possible a 54cm would fit her better, but the differences are so small I’m not sure how much it would matter. There is more seat post in the tube than showing, and the stem is 90mm. I’m 5’10” and my bike is 56/56cm and I find her new bike comfortable.

She tried out a 50cm Rivendell Cheviot and an 18” 1985 Bridgestone 300 mixte. Including the Soma, all three feel the same size wise while riding, at least to me.

It would seem a mixte frame allows for a greater range of rider specs than a standard diamond frame.

Yes, no? Mixte frame sizing is new to me.

Virtual top tube length gets you in the ballpark. I have a Buena Vista in 58 and am 5’ 9” with swept back Albatross bars and a long stem and it fits great for me. Are you using drop bars on you girl friends bike? Drop bars will work a lot better on the small frame for her height based on the geometry you posted. It seems she (and you) would be cramped on the small frame and bars that are flat or come back. Any pictures of the bike? As always, fit is individual and where you ride, how far you ride, how fast, etc. all factor in.
Tom Palmer

The bike frame is too small.

Just because someone can straddle a bike and pedal it, doesn't mean it fits.

They make different sizes for a reason. If she was going to use Albatross bars as TomPalmer points out above, then the 54 cm. Drop bar or something with less pull back then maybe the 50 and I am hesitant on that one.

She is 7" taller than the person that bike was designed for. You wouldn't buy a bike for yourself that was designed for someone who was 5' 3" would you?

I have always liked the look of that frame and think it makes for a great bike, just buy the right size.

The seat height is set up for her. There is no toe overlap and her knee is above the center of the pedal.

Looking at the chart, I realized that the bottom bracket drop is 30mm less on the 42cm than the other sizes. I’m not schooled in bike geometry, but this bike feels better, less cramped, than a 50cm Cheviot with Albatross bars or an 18” Bridgestone mixte.


There is a shop local that has a 54 frame built up that I’m going to have the GF try out and see if she likes that size better. If we need to order a larger frame, that’ll be fine. I’ll just swap the parts over and sell the smaller frame.

She doesn’t do long rides yet, just short rides with me and my son to grab burritos downtown.

The photo just reaffirms my thoughts on this bike. As beautiful as it is, the spacers under the stem alone tells me that this isn't the correct size. The length of the seat post also is a good indicator it just isn't right.

That frame size was designed for 26" wheels so that is why the brake pads are at top the slots with your 650b wheels. If she has been riding this one and gets on the 54 she is going to feel like the bike is a monster bike but in time she will get use to it. My wife who is 5' 3" rides a 50 cm 650b Rivendell Betty Foy, though with Albatross bars.

My buddy is building up the Soma bike for his girlfriend and is using the 650 wheel size like you and she isn't 5" tall. He is also going with a 155 crank if I recall correctly.

You have done a nice job with the build, I like the IGH choice, very clean looking. Good luck with everything.

I didn’t do the build, I bought it this way. A local shop built it up. The original owner is now in her 70’s and unable to ride. Per her son, it sat unused for at least 5 years. She bought it around a decade ago and paid $1200 for it.

with regard to the brakes, they are tektro 559’s. I’m sure the shop knew that the frame was meant for 26” wheels, but felt the 559’s would make the 650’s work. My gut said the bike was too small, but I felt in the long run it would be cheaper to buy this bike, get a larger frame and swap parts if need be. We all know the secondary market for used bikes is goofy. The components are nice and the bike didn’t seem to have been ridden much.