I was surfing through ebay the other day. There in the used bike section was a FSR Stumpy, a near clone to my 26er, same size frame with 650b rims and tires. The owner stated it worked fine, but due to clearance, riding muddy trails could be an issue. I looked into making the swap. I can pick up a new set of wheels and tires for under $200. The axles will fit the older 26er frame and shock dropouts. I have an older Fox F-100 that, for some strange reason, has an additional 0.5cm clearance in case I need it. Also, the hardtail has better clearance in the rear, so if the dual sus doesn't work, maybe the hardtail will.
My question is, has anyone on here tried this or know someone who did and what were the results. Any experience input is welcome.
Here are the two bikes I'd be trying this on:
The dual sus has a Talas

The hardtail has a F-100.

I've read about it a shedload, and I'm fascinated as to why someone would do it for a 4% larger tire. Yet we have a whole industry and consumers doing exactly that.

Anyway, I like to run wide 26" tires, 2.25" to 2.35". On a conversion, you'll have to run narrower 650B/27.5 tires. That alone is a dealbreaker for me. But, yes, a 2.0" 650B tire should clear many 26" bikes except for XC race bikes that can't even fit a wide 26" tire.

Thanks for the input. Yeah I'm concerned about the width of the tire too. I'm running 2.3 on the front and 2.1 on the rear of the green bike. However, the hardtail has tubless 2.1's on both. Granted, I only use it for milder trails.

I don't know about any 4% difference as I never measured. But I do know Its Night and day for me, a 26 to a 27.5

The 650b has most of the roll over advantage of the 29er's without the added rotational mass and added cost to make a larger hoop as stiff, And IMO it has ALL of the flickability of the 26 inch bikes..
All the newer downhill bikes are jumping on 27.5 it looks like..

My simple math says its an 8% difference and so far almost every Improvement I have made to my bike's handling has been the smallest of Increments.

Raising the handle bars just half the bars diameter,
then rotating them up a a few degree's

Moving my seat back 1/4 inch.

Moving the controls inboard a half an Inch,
Using only one finger on the front brake,

Its the little things sometimes.

The 27.5 wheels on a bike with geometry for a 26 inch wheel set,,, center of gravity up some ?
Other than getting the crank up over rocks the only other advantage is better roll over right ?

Its all in the little things IMO.....

Nice looking sleds OP

By published ETRTO numbers, the 27.5 bead (584) is 4.5% larger than 26 (559).

To find mounted tire height & width, you have to read test reviews. I've never seen such a review show that a 27.5 tire to be more than 5% larger than the same tire model & width in 26. But of course, no one is doing those comparisons anymore, because new 26" bikes are nearly extinct outside of department stores.

My first guesses as to why you like your 27.5 better than a 26 would be that you have a better bike, better tires, and better setup. Those are real things that could and probably did happen. Less flattering would be simple confirmation bias - a consumer getting something new expects it to be better, so they often feel that it is better.

I had a Santa Cruz Superlight in my stable . This is a popular conversion for that bike. I opted to go new 29'er -- i had the same opinion as Colin -- didnt seem like a lot in the cost/ benefit ledger and i wanted something that would be a bit more noticeable

I could have spent 5-600 on a set of wheels, possibly the same on a new fork with better clearance, then a little more to replace the worn out chi chi's (cables, chain, cassette) and made it an awesome 650b'er

But then again, i also would have just spent a bunch of cash on an aging platform and would have been miles ahead just replacing the wear items and tires and keeping it rockin'
(if you have parts laying around to do this, or can build wheels yourself with a minimum investment, -- go for it though)

Just run 2.5 tires on the 26" rims, it will be very close to 27.5 with skinny tires.