WTB Trailblazer 2.8: 27.5+ revolution?

20 10 2014

Despite some folk bemoaning the introduction of yet another tyre size, the 27.5+ makes all sorts of sense.

For starters, a 27.5×2.8 tyre such as this one, the WTB Trailblazer, fits in the rear of a 29″er that has reasonable clearance. “So what?” I hear you cry. Width on my 35mm Velocity rim (tubeless) is 68mm and the diameter is 726mm – in other words, a wee bit less than a full blown 29″er, in order to keep the widest point of the tyre further back in the chainstays.

[NB: I had previously noted the diameter as ‘right around 735mm’ – after a prompt from Michael, see comments, I measured this accurately and the diameter at 14psi on the 35mm velocity rim, tubeless is 726mm…it just goes to show, always measure yourself if you want to be sure! – thanks Michael].

The benefit is you get some of the advantages of a semi-fat tyre (improved traction, lower pressure, better ‘float’) without having to get all weird building a custom bike with a yoke or fat-bike wide bottom bracket and rear hub: it should slot into many 29″er frames with minimal fuss. The only thing to consider is a slight drop in BB and slackening of angles if only the rear is retrofitted.

My suspicion is that there will be several 27.5+ tyres along forthwith and my guess is they will in some cases be larger than the Trailblazer from WTB, in some cases the same. Rumour is that the Vee 27.5+ tyre (the Trax Fatty) is a full 75mm+ wide and will not fit most 29″er frames. There are whispers of Bontrager and Panaracer 27.5+ tyres and another WTB in the pipeline too.

How does it ride?

Really well. Much better edge than a Knard and it gives up little in terms of the float/low pressure (I was running it at 14 psi and will probably drop it one or two). I was riding in slop today and I hardly ever lost traction despite the centre ridge being almost complete and the other knobs being not that burly. You don’t get the insane roll-over-ability of the huge 29+ wheels (which are near 770mm in diameter), but the low pressure helps maintain progress in rocky, chunky terrain. The compound seems good – minimal slip on wet, mossy rock and roots. and the tubless set up was a treat – TCS is good. It is not über light at 950 and some grams, but the sidewall is solid which is a good thing.

More time is required to see where this is going, but I like it so far. Most folk are going to comapare these to fat bikes and 29+ knards, I suppose, and I think that comparison leaves the Trailblazer in a favourable light.

As WTB say: Big Kid Shreddin’ / Plus Sized Grinnin’

As an aside. I set up the Velocity 35mm rim with a bead seat shelf augmented with a Gorilla tape lip after a discussion with davechopoptions. It worked surprisingly well…and we will see if prevents burps.

…and after a final layer of tape…you can just make out the extra ridge…

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One-up 40 tooth sprocket and RAD cage.

19 10 2014

When I was looking at doing the Highland Trail Race earlier this year, I was slightly concerned that my usual 1×10 set up would not have a low enough gear to cope with the combination of very tired legs, steep hills and a loaded bike. I looked at using a 30 tooth chainring, but felt this would diminish the gear range detrimentally.

At that point I became aware of the release of the RAD cage, by One-up components. The purpose of this is simple: it changes the way the upper jockey wheel moves in relationship to the rear freehub cluster. Why? you can adjust a traditional derailleur to cover a broader range of rear sprockets, primarily by increasing B tension, this creates enough clearance for a 40 or even 42 tooth sprocket. However, this compromises the jockey wheel’s tracking of the sprockets, particularly in the higher gears (smaller sprockets). In essence, shifting suffers as the upper jockey wheel is far in excess of the suggested 6-8mm from the sprocket.

The RAD cage is well made and following the video instructions for installation makes the process extremely easy.

A few months ago, I fitted a 40 tooth large sprocket and the provided 16 tooth sprocket that replaces the 15 and the 17 tooth sprockets in the original cluster (you must remove one in order to make room on the freehub body for the extra 40 tooth sprocket). I use a Wolftooth 32 tooth chainring, with an XT donor cluster and XT rear mid-cage derailleur. I decided on the 40 tooth rather than the 42 because I felt this would give the derailleur a little less of a hard time and it is also the same range as the new XTR that I am quite keen to use in the future.

I have a few hundred miles on the system now using the provided One-up 16 tooth replacement sprocket and then an aftermarket XT 10 speed 16 tooth sprocket*. The gear range has changed from 11-13-15-17-19-21-24-28-32-36 to 11-13-16-19-21-24-28-32-36-40. Unfortunately, the 15-17-19 area is where I spend a lot of time and I was concerned I would feel I was not in the right gear too often. It is true that I do feel the increased jump between ratios, but not badly enough to take away from the huge boon the 32-40 ratio is. You can climb walls, even loaded, with this gear ratio.

Shifting: the shifting has been a mixed bag. The ramps on the provided 16 tooth ring seem (to me at least) to be in an unusual orientation. The part has 2 fitting positions: one for SRAM and one for Shimano. I initially used the Shimano position and noticed a lag of around a second of chirping before an up shift was achieved. There was also a lag on the down shift. When I fitted the part, it was clear the SRAM position was much closer to keep the ramps on the sprockets in line, but I decided to follow the instructions to the letter. On refitting in the SRAM orientation, things improved but there was still a lag that bugged me.

I then fitted a *Shimano 16 tooth sprocket and with this, although not exactly in line, the ramps were really closely aligned indeed. Shifting quality is now almost at original ‘Shimano perfection’ levels. I think the detailed tooth profiling aids up shifts to higher gears and the ramps being in line helps the down shifts. Don’t get me wrong, the supplied One-up 16 tooth is good, but Shimano carry a big stick when it comes to shifting performance. This is something I would recommend if you go for this system with a Shimano set up – I cannot comment on the SRAM performance.

Longevity: you *can* see wear on the 40 tooth sprocket (it is anodised black aluminium as opposed to the steel of the original Shimano set up) but there has been no drop in performance.

All in all, I am extremely happy with this set up. Things I would like to try: a short cage RAD cage for the Saint derailleurs I love. I have no idea if this would provide enough chain gathering to let the system work, but I can dream.

All in all, I would say this system merits 8 out of 10. If longevity remains good as we come into winter that would be 9/10. Improved 16 tooth sprocket would give it a near perfect score: as a hop-up kit to provide increased gear range, with the accepted change in the jumps between ratios, it does exactly what you want it to do and it does it very well indeed.