Is it OK to change an ebike 27.5” front tire/wheel to a 26” on an ebike cruiser?

Question

I am interested in switching, for the winter, a 26” studded front tire/wheel on a 2019 Rad city cruiser to a new avinton level2 with 27.5” wheels without studs. Will this work? I routinely ride 20-30 miles a day, weather permitting.

Answer 1

If you’re asking if a 26” tire is compatible with your 27.5” rim, the answer is “no, it’s too small”.

If you’re asking if it is possible to take a different 26” wheel and mount it in a frame/fork whose original spec included 27.5” wheels the answer is “maybe + some caveats”.

You’ll be able to put your other wheel in there if:

1. the drop outs are compatible (e.g., QR vs 12 x 100 mm thru-axles)
2. The brakes are of similar type (e.g., disc vs rim brakes). Since the frame is recent enough to have come with 27.5” wheels, my best guess would be that it also has disc brakes. If the 26” wheel already has a rotor, it needs to be the same diameter of the existing one. I would clean it and go through the “bedding in” process with them. There is also the question of rotor alignment — different hubs don’t place rotors in exactly the same place. If you swap wheels and rotor rubs on the brake pads, you can realign the caliper, but in the long run it’ll be more convenient to space out one rotor or the other so that no adjustments are necessary with a quick wheel swap.
3. Final and easiest thing to consider is the width of the 26” tire (i.e., will it physically fit into the fork with sufficient side clearance (vertical clearance won’t be an issue with the short diameter).

However, if all of these things fall into place, this would not be an attractive option to me.

The reason for that is that I wouldn’t want to ride the bike with the altered geometry (lower front end, lower bottom bracket, steeper head tube and seat tube angles, and longer effect reach/top tube) that you get when you put a smaller wheel up front.

That said, 26” tires and 27.5” tires aren’t as different as the industry would have had us believe in the early 2010s when the MTB world sold 27.5” as the great compromise between 29” wheels and 26” wheels before they figured out 29” geometry very well. The outer diameter of a 27.5” tire is much closer to a the same width 26” tire than the corresponding 29” tire (it’s not “halfway” between the two by any means). If you have lots of frame clearance, you might be able to find an even wider 26” tire to make up some of the difference.

In short — if the axles and brakes are compatible, it’ll probably work. It’ll change the geometry of the bike, but possibly not too much. In an ideal world, you’d have a second front 27.5” wheel dedicated to the studded tire, with the same model hub so that the rotor alignment is consistent between wheels.