650B+ First impressions

There has been a lot of hype over the last year or so about the new B+ tyre standard (27.5 Plus or 650B+, call them what you will) it seems that they'll be everywhere for 2016 with many manufacturers making plus size models.  So I thought it about time to get some tyres to try them out to find out what it's all about. This quick blog will give you my thoughts and first impressions. This is all personal opinion so please take from this what you will!!

Spline 29 fitted with WTB Trialblazer 2.8" B+ Tyres

WTB were the first to produce a B+ option with the 2.8" Trailblazer and massive 45mm scraper rim. The initial talk was that the big tyre on a 650B rim was slightly smaller than a standard 29er tyre in diameter but obviously wider. This meant that they would fit into many existing 29er frames with the promise of improved grip and reduced trail chatter due to the ability to run lower pressure. Sounded great to me especially for use on the Spline 29 hardtail, could be a fun option..  So I ordered up a set of the Trailblazers from Charlie the Bike Monger and set about playing about with them!

Fitting
My first thought after mounting the tyres was they're not that big at all! I wanted to do as many will, and that is to mount them to existing wheels that they already own, in this case a set of Stans Arch rims. Obviously these are very much narrower than the 45mm Scrapers that WTB designed the tyre to work with.  Below are the measurements for my rim/tyre combination and a couple of non plus sized tyres for comparison.

WTB Trailblazer 2.8 on 650B Stans Arch - Width 62mm, diameter 716mm
On One Chunky Monkey 2.35 on Light Bicycle 28mm internal 29er - Width 60mm, diameter 740mm
Schwalbe Hans Dampf 2.25 on 650B Stans Arch - Width 57mm, diameter 700mm

This was a bit of an eye opener for me! They're actually closer to a 650B wheel than they are a 29er and on these rims they're not much wider than the On One tyre I'm using on my 29er currently. Sure, the wide rims would give extra width and volume but I cant see the diameter increasing by much more than a few mm. They'll end up pretty much bang in the middle of 650B and 29 sizes. 

The wheels were fitted into a Spline 29 hard-tail without issue. The clearances to the fork are getting a little tight on the sidewalls but perfectly acceptable, with the wide rims this may be more of an issue. We tried them in both Rockshox Reba and Marzocchi 320 29er forks with pretty much identical clearances.

One side note here, they actually fit really nicely into Rockshox 650B forks and I've been using a Trailblazer on my 650B trail bike as a front tyre! ​

Clearance to a Rockshox Reba 29er fork

Riding, the fun part!
Initial impressions are good for general use. They roll really well, seem nicely grippy considering the fairly modest tread pattern and indeed the larger volume does take out some of the trail chatter. When you push them harder you begin to find the limitations of this tyre/rim combination. I tried running low pressure (18psi) but frankly it just didn't work, they were squirming about a lot and you could actually feel the sidewalls creasing. I ended up running them at much the same pressure as I do my normal 29er wheels and they still felt a bit squirmy when pushed hard. 

​Conclusion
So then, this all leaves me a bit confused! Yes they fit into a 29er frame, yes they're slightly higher volume yes they roll really nicely and seem grippy. On the downside, they're not that wide and feel a little unpredictable (when really pushed), mainly I'm sure, due to the narrow rims I used. However, on wider rims I'm nervous of that tyre clearance on a standard 29er fork will be getting quite tight..... 

I don't feel that I have truly experienced plus size yet, more experimentation is needed, will try and get them fitted to some 35mm rims and see how that plays out. Stay tuned!!

Check out this link for an interesting read on why wide tyres roll nicely off-road
http://www.mtbonline.co.za/downloads/Rolling_Resistance_Eng_illustrated.pdf