I posted the other day a link to 650B Palace’s list of 650B-compatible 26" mountain bike frames, but that doesn’t help much if your frame isn’t on the list.
Assuming you already have a frame that isn’t listed, and all you want to know is actual measurements for various 650B tires on the market to see if you have clearance, you can check out the shared Google Doc below. The list originally showed up on MTBR.com, but I honestly can’t remember who shared it.
Also, if you’re looking for a 650B-compatible fork, here’s a thread on MTBR.com that will hopefully make it easier for you:
There’s a growing number of mountain bike riders out there who have chosen to keep their 26" bikes, while converting them to the new-to-MTB 650B (or 27.5") wheel size.
The advantage of 650B is that they’re larger and smoother rolling than a 26" wheel, but lighter and more agile than a 29". This disadvantage is, it’s hard to know what current 26" bikes on the market have room inside their chainstays for the larger wheels.
Fortunately, Cracked Headtube (if that is his real name) over at 650B Palace has put together one hell of a list of 650B-compatible frames, so if you’re looking to upgrade, take a look at his list.
I just found this older post from a guy who calls himself Guitar Ted, about the resurgence of the rigid mountain bike fork. Thought I’d share:
He didn’t really go into a lot of detail as to why it’s once again become the trend to ride a rigid fork, however. Personally, I always thought it was pretty stupid to ride rough ground without some sort of suspension, but since I’ve been riding a couple rigid forks these last few months (aluminum and carbon), I’m a believer in fat tires and rigid forks.
Yes, it’s bumpier, to say the least. But with that, I’ve gained a better sense of the ground as I roll over it, no longer wondering where my front tire is. I descend a little slower, obviously, although I make up for it on the climbs due to zero energy being lot through suspension bobbing. I can definitely see why so many 29er and 650b riders are ditching the suspension forks in turn for larger-diameter, smoother rolling wheel/tire combos. For the time being, though, I’m more than happy riding rigid on 26" wheels and 2.3" tires at sub-30psi.
If you haven’t given it a try yet, find an inexpensive steel fork and go for a ride. It just might change your mind about needing suspension to make up for your riding technique.