650B wheel on Yeti 575 ?!?

Aaron wants to build a sweet new Yeti 575 with a 650B front wheel. This brings up some issues. Let’s have a look, shall we?


Okay, I’m going to throw a monkey wrench into these three posts:

Stem and bars: long and low or short and high?
Stem length/rise for a trail bike
Pros and cons of a shorter stem

I’m going to put a 650B front wheel on a 575.

So far I’m leaning towards 2″ bars/50mm stem, but I need to determine whether or not I’m going to put on a 70mm stem.

The 650B front wheel is my only hangup.

Any suggestions? And please don’t suggest to not run a 650B front wheel. 🙂


P.S. I forgot to mention that with a 160mm fork the TT length increases and I’ll be running one of those 36 Fox Van Rs.

Hey Aaron,

Well … OK … I won’t tell you not to run a 650B front wheel.

According to your site — bicyclesbyaaron.com — you build custom bikes. So you must know what you’re doing.

Just be aware of some things:

A 650B wheel is the midpoint between a 26-inch wheel and a 29-inch wheel. 650B wheels are about 27.5 inches in diameter. They supposedly provide the improved rolling of 29-inch wheels, with fewer of the drawbacks (immenseness, slower handling, frame/fork design constraints).

On rough trail, 29s roll about 6 percent easier than 26s. Let’s say 650Bs roll 3 percent easier. I’m not sure that’s worth the hassle.

First, is there room?
I have an older 36 FLOAT on my Enduro SL, and there is only about 5/8 inch clearance between a 2.3 Specialized Clutch and the fork arch. I don’t see you fitting a decent-sized tire on a 650B wheel in that fork. But: I have asked Fitz at FOX, and we’ll see what he says about the new models.

Bar height
Given the same tire cross section, a 650B wheel will raise your front end 3/4 inches higher than a 26-inch wheel. So take 3/4 inch of your combined bar/stem rise.

Unbearable slackness
Raising your front end 3/4 inch will significantly change your geometry.

On the Yeti site, the difference between a 140mm fork and a 160mm fork (.8 inches) is 1.6 degrees. The bigger wheel will slacken your geometry about 1.5 degrees. So, with a 160mm fork, an all-mountainish 66.9-degree head angle becomes a DH-ish 65.4 degrees.

Stem length
Slackening your whole bike will lengthen your effective top tube by about 0.4 inch, or one centimeter. You can offset that by adding 10mm to your stem — but with a 65.4-degree head angle (and now a 68-degree seat tube angle) I wouldn’t be too worried about the seated climbing position. You’ve turned your 575 trail machine into a freeride beast.

My opinion
Some very smart people designed the Yeti 575 and FOX 36. As a matter of fact, these guys work together to make the bikes handle a certain way. I’m inclined to trust them.

If you decide to go 650B punk rock, be sure you make the proper adjustments. And please tell us how it goes.

— Lee

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