Comparing geometry to predict fit vs known comfortable fit bike?

[jim1274]

I’ve test ridden several e-bikes, finding none that were comfortable until recently, most in the largest frame size available still too small for my 6-3” height and 35” inseam. So many bikes come in only “one size fits all” or 2 frame sizes, many having lower max recommended rider height/inseam. By chance, I rode one that came in 3 frame sizes, the largest one seeming just right. I noticed this bike seemed to have higher handlebar height relative to the seat position than any of the others I test rode.

The bike at the top of my list is the Zen Photon (19” frame size):

Zen Photon Long Range Electric Bike

Experience the ultimate ride with Zen Photon e-bike featuring a powerful 1000Wh battery. Enjoy an 85-mile pedal-assist range for endless adventures!

zenebikes.com

This is the bike that felt right on fit (Large size):

Serfas® - eDASH 500W E-Bike - Serfas

Serfas® Dart 500W - Step Over and Step Through Frame - 500W Electric Motor - Samsung® Battery - 30 Mile Range - Class 3 E-Bike

www.serfas.com

Comparing the reach, the difference is less than half an inch—check.

Comparing the head tube length, the Serfa is over 3” longer—would that mean the handlebars would be 3” higher if the head tube angle was the same and handlebars same geometry? The derailleur drivetrain on the Serfa is a deal breaker for me, plus the Photon is a better spec bike in many ways beyond that. The Photon is exactly what I’m looking for, trying to decipher the comparison in geometry to predict fit.

Comparing 2 bikes, If the reach is the same, same handlebar geometry, and same handlebar height relative to seat height, wouldn’t they “fit” the same? Obviously this would be for one rider, the head tube angle and seat tube angle changing things as adjustments were made as rider anatomy changes.

Does this make any sense? Is it possible to even compare the geometry specs to predict fit?

 

[Ben J]

There are tools like https://bikeinsights.com/ which will show you the geometries of two bikes superimposed.

My understanding is that you can go by geometry if you're talking about a very similar style of bike (comparing two road bikes, for example). It probably doesn't mean much if you compare across bike types.

You might have just discovered that you are looking for a bike with a more upright posture, which also affects how the saddle fits, etc. That makes me think you've identified a style you like more than a specific set of measurements.

 

[jim1274]

There are tools like https://bikeinsights.com/ which will show you the geometries of two bikes superimposed.

My understanding is that you can go by geometry if you're talking about a very similar style of bike (comparing two road bikes, for example). It probably doesn't mean much if you compare across bike types.

You might have just discovered that you are looking for a bike with a more upright posture, which also affects how the saddle fits, etc. That makes me think you've identified a style you like more than a specific set of measurements.

Thanks for the input, Ben. I guess the general category here, broadly speaking, would be hybrid? Yes, a more upright riding position seems to be the most comfortable to me, most e-bikes for road use seeming to fall in this general category.

The Zen Photon has about the same reach as the Serfa that felt right, but found out the Photon was a 38 degree handlebar sweep back compared to the 15 degree on the Serfa, so that would seem to change “fit” a lot. I believe the Photon handlebar probably could be replaced with a smaller sweep to try and match the fit, if needed. The sharper sweep would seem to put one’s wrists in a different position, maybe less neutral than a less pronounced sweep? I had another bike with a very sharp sweep angle, wrists in an awkward position, resulting in numb hands after less than 30 minutes of saddle time.

I have not used that geometry comparison you linked, but have explored the one on 99 Spokes. The problem with them is a lot of bikes are not in the database—I’ll try your suggestion to see if more bikes are included.

I’ve been struggling with the same fit issues on a non-electric bike too. Taller riders just seem to have a lot less choices when you get into XL frame options or trying to make a large work, electric or non.