Saturday, 5 November 2016

Scratching the N+1 itch

One of the Velominati rules is "The correct number of bikes to own is N+1 where N is the number of bikes you currently own." In real life this is limited by W which is the number of bikes your wife owns.

Since I got the Cotic Solaris it's pretty well scratched that N+1 itch, every time I've looked at another bike to cover some particular off-road activity I've realised that the Solaris will do almost all of what I'd be getting the extra bike for and most of the time the new bike would gather dust. As a result I've stuck with the Solaris, modern steel hardtails are surprisingly adaptable beasts.

I did get myself a set of "Plus" or "semi-fat" wheels which is a cheap way of completely altering the nature of the bike. As their name suggests they are a sort of halfway house between standard MTB wheels and tyres and those on fat bikes. With limited space in the house they are also an efficient option in that regard. Which sort of brings me to the one category of bikes that the Solaris or any standard hardtail can't cover: fat bikes.

Yep, those comedic looking bikes with a pair of life buoys for tyres.

I'd an idea that required a fat bike and it just so happened that I remembered seeing a post on the Bearbones forums that someone had one for sale. A bit of crawling back through the classified section and there it was: a Singular Puffin rolling chassis, basically frame, forks, wheels, seatpost as well as a prototype frame bag. It was being sold by Ian Barrington who'd used it for the same ride I was thinking of. It was still available so a couple of messages and a transfer of funds later it was mine. Now there was just the job of getting it to me. We were both doing the BB200 so easiest to get it then. He was also selling a set of Avid BB7 brakes which he'd used on the bike so I grabbed them as well since they'd be set up for the bike.

In the meantime ...

Internet shopping!

Walk in to any decent sized bike shop (or even the mega-stores that are appearing) and there's a bewildering plethora of parts on offer, not only that there's multiple choices for each part. Look closely however and you'll notice something, or rather you won't, there are virtually no parts for Plus or Fat bikes. Not even tyres. Even though a fat bike might stick in the memory when you see one out on the trails they are very much a niche product. (There are fat bike specialists like Charlie the Bikemonger but these are the exception.) To accommodate the wide wheels three areas also need widening: the front fork and axle; the bottom bracket and cranks; the rear triangle and axle. In my case the front and back ends of things were already dealt with since the rolling chassis had the wheels, all what I needed was a set of cranks. 

It turns out that there aren't that many fat bike cranks around, who'd have thunk it? I'd another item on my shopping wish list: a 28T oval chainring. This really limited my options as to use that sort of chainring would mean a direct mount rather than a traditional spider where the arms would foul the chain. The choice came down to two: a fairly expensive alloy model or a stupidly expensive carbon jobbie. Of course I went for the alloy one - the carbon set would cost £2 for every gramme saved in weight. Why a fat bike specific crankset? Well the width of the tyres means that using a normal width crankset would cause the chain to rub against the tyre at its closest point to the bottom bracket so things need to be moved out a bit.

The rest of the parts weren't fat bike specific, derailleur, chain, stem, shifters but one does stand out, the Jones Loop bars. These look weird and to anyone accustomed to standard mountain bike handlebars, just wrong. This summer I'd had a very short ride on a bike with them fitted, the ride was actually to try out the Lauf forks that the bike also had but I couldn't isolate how they worked because of the Plus tyres on the bike. The bars felt right though in the same way that the Solaris had felt right when I first rode one around the car park at Dales Bike Centre. More searching and I managed to get a virtually unused 2nd hand pair of carbon loops for £200.

The first evening of work was fitting forks, stem and bars as well as brake rotors to the wheels. I just had an hour or so before having to make tea. Because of their shape getting the angle of the bars is quite critical to comfort. Without riding it I could only make a guess.

Raceface cranks and Absolute Black oval chainring.

The next evening's short work session saw bottom bracket, cranks, cassette, derailleur, brakes and saddle fitted. Again, without riding, I wasn't able to judge the best angle or position for the brake levers. I left the calipers loose as I needed daylight to be able to get them properly aligned. The same applied to setting up the derailleur.

So on a Saturday morning I set to work to complete the build. The brakes were easy enough, I've had BB7s before, but I did need a new set of pads for the rear brake which I fortunately had "in stock". On to the drivetrain. At this point I noticed two things: 

  1. In my eagerness/stupidity I'd ordered cable outer for brakes not gears!
  2. I'd fitted the bottom bracket without the spacers so needed to remove the crankset and the BB to sort that out. The instructions for the cranks had notes on how to install them but not how to remove them! More internet searching and it turns out I need an ISIS crank puller.

A trip to Rider's Cycle Centre got me some gear cable outer but none of the shops in town had the crank puller. Back home I began to ring round more local shops, the shop near my work had one so I asked them to keep it for me and headed down the valley. An hour and a bit later I'm back home. It took longer to get the puller out of the blister pack than getting the crank off! The right tool for the job and all that. I also checked my phone to find a missed message from the same bike shop that the bar tape I'd ordered had arrived! Oh well, that would have to wait.

With the bottom bracket and cranks sorted it was on to the derailleur. I've never fitted or set one up before. I read some notes on the web, then re-read them several times, then read them again. Cable outer on, measure twice cut once, set the high stop, fit the chain, fix the cable and click down the gears. A bit of twiddling of the low stop and I'm in the bottom gear. Going fine. Except I can't now change gear plus the gears are making an awful grating sound. Then I realise I've not set the B-screw! So turn that in a couple of turns and now everything's working as it should. Last job is to cut the cable and put on the cable crimp.

Cassette and Derailleur.

The Puffin comes with removable cable guides in case you run singlespeed so these need fitting and the relevant cables fixing in them.

Having picked up all the bar tape on the Monday morning I got home then realised that I'd need some black electrical tape to finish things off so another day of waiting and a visit to the local hardware store. 

Taping the bars. I've gone for a two colour scheme to reflect the multi-coloured beak of the puffin itself: the rear part of the loop will be yellow and the front part orange. I could equally have gone for orange and red. The central part of the front loop is clear to allow fitting of lights, this gap is the same width as that around the stem clamp on the rear part of the loop. The real difficulty comes with how to tape around the junction of the two parts of the loop as the welding and fillets make it quite awkward to get a complete coverage without creating excessive bulk.

After considering various sequences I settled on doing the rear tape first, starting from the stem and working towards the joint, this way allows the tape to sit better on earlier wraps on the taper between the 31.8mm and 25.4mm tube sections. The end of this tape was then wrapped around the joint in a cross pattern, extra layers in the corners of the joint aren't a problem. Then I did the front tape, again starting from the front and working back towards the joint. This let me apply the tape in a spiral that matched the angle of the joint. I did a sort of figure of eight around the joint covering up the finishing loop of the first tape before finishing a couple of centimetres behind the joint.

Repeat on other side.

The taped bars. Ignore the grips, they'll be replaced with black ESI grips. 

I've a couple of old grips lying around so put them on as an interim measure but I'll keep them on for a while and move the levers and shifter around a bit to get an idea of which position is best for me, then I'll cut the ESI grips to suit. My Hope flat pedals that I swap on and off the Solaris get fitted, time to have a quick ride round the yard. But first a weighing, there's no bar tape but the lock-on grips are heavier than the ones I intend to use so probably balance out. The scales say 14.3Kg. Pump the tyres up to something that should be OK, 7.5psi!

The final build!

So, apart from the grips it's done.

First ride: it's definitely different. Yes it's a bike but the front end seems to have a mind of its own due to the gyroscopic effect of all that spinning mass, particularly when you build up speed. There's a feeling that the front wants to tuck in as you turn, there's also a slight twitch when you come out of a turn and you are bringing the bike upright again. All this is much more noticable on tarmac as the tyres have so much grip. This grip also manifests itself by amplifying those small lateral movements that occur when riding. On something like a road bike on 23C tyres you'll see the front wheel "twitch" almost continuously but it has little effect on riding. On the fat bike these all continually conspire to pull or push you to one side

The next ride sees a bit of progress: lean in to a corner and give a definite shove to the handlebars on the side that I'm turning towards, it's just enough to counter the tuck feeling. I've never ridden a motorbike but I imagine the riding technique is pretty similar in terms of handling the spinning mass. A bit of investigation reveals that it might be caused by running at too low a pressure so I have a look around and find a fat bike equivalent to the Stans formula: 

  • weight in Kg divided by nine then subtract 0.5psi for the front and add 0.5psi for the back.

There's another formula:

  • 1psi for each 10Kg in weight of rider and kit

These both produce very similar values.

With the tyres now at the "correct" pressure the next ride was somewhat less fraught and the bike just about went where I aimed it.

One thing that I wasn't sure I'd got right was the angle of the bars. I'd fitted them with around a 20deg slope towards the rear almost the same angle as the rake of the top tube but this felt a little strange so I lifted them up by five degress. Another ride or two and that didn't feel right so eased the angle a little more as well as ease the downward angle of the saddle nose. Having the saddle level doesn't work for me as the constant buffetting from the trail forces my weight on to my hands causing numbness over time. A slight nose down is the answer. I also move the saddle back a cm.

All this is really trial and error to find what works. What setup works on one bike won't necessarily be correct for another.

On the descent into Kentmere

I've been using the Puffin for my commute in order to get used to the handling and as a set of shakedown rides as well as getting the handlebars and saddle positions sorted.