The 650b fork meets the Yeti SB-66c — a love story

By Matt Kasprzyk

Why mess with a good thing? To make it better, of course. If you agree with the reviews and press; Yeti’s SB-66c is a good thing – if not a great thing. So good that I leapt at the chance for the super-bike to kill my quiver. Yeti has already received several accolades from our staff and many others for their Switch Technology suspension bikes. They must be a good thing, right? So why f’ck with it?

Here’s my reason. Maybe you’ve heard about the 650b craze that is now the 27.5 craze, or what may become the 27 rage? If you have, then you’ve also heard about the shortcomings of 26-inch wheels and the overcompensating 29-inch wheels. What you’re about to read is my attempt at taking a good thing and making it slightly better by asking one question: How would a really ballin 26-inch bike feel with a 650b front wheel.

The steps to answer that question aren’t so simple. Sure, you could grab any 650b fork with a wheel and slap it on there.

The problem with that solution is it could affect the bike’s geometry and characteristics. Maybe the new axle-to-crown length is longer, thus slackening the head-tube-angle. In turn that raises you handlebar and bottom bracket height. Blah, blah, blah and see what a slippery slope this gets into. Sure some of those adjustments could be favorable, but this experiment is solely about a 650b front wheel on a 26-inch bike and what the slightly larger diameter wheel feels like out front. Will this give the “goldielocks” ride while largely maintaining the personality of the bike? Is the slight diameter increase even perceivable?

First, I needed to isolate some variables in this experiment. I wanted to preserve the geometry of the bike as much as possible. That means you need to do some math. Or find someone smarter than you who knows what math to do, which is exactly what I did. Enter Justin Steiner, our resident engineer and mecha-builder. (I’ve never seen Justin build a mecha, but it would be cool.)

Step 1: Measure twice

Know your current measurements

  • Head tube angle
  • Axle-to-crown
  • Front wheel axle height

New setup

  • New fork axle-to-crown
  • New wheel axle height

Step 2:  Sketch

Step 3: Math

Step 4: Space fork down and install

Step 5: Ride

Ride Impressions

I’ve done some intense rides on this 627.5er or SB6/27.5-6/5. My first impression was that there was more wheel flop. With equal HTAs the math shows that there will be a slight increase to Trail. This could account for the added perception of wheel flop while climbing.

However, other than that there really isn’t much to say. The bike’s character wasn’t drastically altered. The 650b wheel is actually not smack-dab in the middle of 26 and 29. It’s closer to a 26-inch wheel then a 29. On the trail I could hardly tell a difference. I like to think that I was able to truck through the rough a little easier without getting a smaller wheel sucked into divots, but it wasn’t as obvious of a change as the move from 26-inch to 29-inch. I attacked descents with the same reckless abandon and emphasis on inertia, rather than grace, as I always do and there was never a moment where I wished for a smaller wheel up front.

The X-Fusion Vengeance fork used in this conversion was slightly heavier than the Fox 36 I had been using. Even so, with the larger wheel and heavier fork, lofting the front wheel wasn’t unwieldy. The Vengeance travel was supple and smooth but I did miss the CTD settings of the Fox.

I think there’s still some fine-tuning and experimentation yet to do, but my final verdict is that the 650b wheel is on there for keeps. I see no reason to take it off. Even if the benefits are minimal, there weren’t any drawbacks.