I'm getting slightly N+1y, hopefully it's just lockdown toting with me,but who knows.
I currently have two bikes, my newish Arkose for travel, and my trusty old KTM 27.5 rigid mountain bike.
I'm wondering about fat, or at least + as theres a whole heap of beaches around here and I feel like I'm missing out.

So, about these plus bikes, what's the main differences between 27.5+ and 29+ ?

I'm assuming Surly and Salsa are the go to brands?

Would I be better going "full fat? Go straight for Mukluk or Icecream truck for example.

If you go 29+ you'll wonder what fat is like. If you are fat 27+ will be in your head. Id suggest go n+1 all out get 29 plus first then fat. Then 27 plus :)

From my limited experience of 27.5 plus, I’d say they won’t be good on dry, soft sand.

Not tried 29 plus, so no comment.

If it’s beach riding you’re after, I’d go the whole way and get a proper fat bike, think Trek, Giant and Kona still offer fat bikes as well as Surly and Salsa.

Have an old Salsa Mukluk and in the right conditions, it great.

If you’re after a bike for ‘all round’ then the plus may work for you

I've got a fat bike and 27.5+.

There's a surprisingly big difference between 2.8" and 4.0" in feel and flotation.

I'm not known for my love of fat bikes, so please take that on board

If conditions are right then a fat bike will likely be the ideal tool for the job or maybe the only tool. However, the right conditions may be few and far between - riding on the beach is all well and good but I know how quickly I'd get bored of pootling along a flat stretch of sand

Plus in either guise is a very different beast to fat and in my mind is a great platform for most conditions, so it's far less specific than fat. I like both B+ and 29+ but generally favour B+ as I find it better suits my stature. They do feel different to each other but you can tell that they're closely related ... fat's like a ginger stepchild.

Ask yourself what you're really hoping to use the bike for. The novelty of owning a fat bike and then having to devise crap boggy routes to justify doing so, quickly wears thin

How about you get yourself a second hand OO Fatty (NB: other fat bikes are available) and build yourself some 29+ and 27.5+ wheels? I've got just this, set up with discs. Swapping wheels over is literally a 10 minute job to remove the cassette, stick it on the wheelset du jour, fettle the brakes and away. The bike feels completely different with each wheelset, and each has its fun side and downside.

There is a big difference between wheel diameters going from 27+ to 29+ and its one of the major benefits of 29+, their ability to roll over stuff is amazing. Works best rigid in my view although a fair few folk have put bouncy forks on 29+. Surly Krampus are great bikes but Trek staches look good as well. If your riding generally defined trails, 29+ rules!

Full fat is a different animal. MY ICT has similar geo and weight to the Kramp but they feel wildly different. As stu says, you need good fat bike terrain to really justify one (although many people ride them on normal terrain) so its down to what you've got and where you are going.

If you’re after something totally different then get a fatbike. I use mine (OO Fatty Trail) as a general trail bike on the local woodsy singletrack, jumps and drops. It’s arguably not the ideal tool for the job but it’s bloody good at it and it definitely makes a change from my rigid bikes or FS.

I’m also a big fan of a 29+ front wheel on a rigid bike. Never tried 27.5+.

Fat bike good for fat bike stuff, although for better rolling then a 27.5 x 3.8” is a really good combination. I have this on the front of my Jones and it rides well. Full fat is better in snow though, the 4.8” tyre much more voluminous.

I know I am always saying this and some people say they find fat bikes slow... But I use a fat bike for most of my bikepacking. I find a 4" tyre just fine. You need to pump it hard for the roads so that it rolls nicely. On gravel and rougher I find it fast enough and comfortable. I have ridden with friends on other bikes and rarely found my pug slower - and often found it faster. I guess It may feel more ponderous at times but I guess I am just used to it. I am not saying it's better than a 29+, just that it seems to be a great bike and if you do want to ride sand or bog there is nothing better!

I think the main disadvantage is weight. I am not bothered about that until I have to carry my bike and I guess an ECR type thing would be nearly as heavy.

I'll repeat what I've said before - tyre width isn't the major thing affecting handling.

I've ridden quite a few of the "older" fatbikes, and had a 9ZERO7 for 8 years. I did lots of "standard" rides on it, bikepacked, took it to trail centres and did the sand/beach thing. It was amazingly good,though it was only one of my collection of bikes, so I could, and did, chop and change a lot. I recently replaced it with a Cube Nutrail. This feels much more like "just a big mountain bike", especially with the Bluto forks. I barely notice the tyre width until I hit something soft and sail across it. Newer tyres are faster rolling, geometry has become less ponderous, weight is less. I guess that the difference between that new fatbike and my B+ bike just feels a lot smaller than it did when I had the 9ZERO7.

I'll repeat what I've said before - tyre width isn't the major thing affecting handling.

It is on my fat bike with three different wheels sizes. The difference in geometry is negligible and sure doesn't account for riding a new bike every time I change wheels.