7 12 2016

Fast and furious. The development of new* tyre sizes that is, not so much the covering of ground!

It probably goes without saying that I have enjoyed several years of messing with 29+, 27.5+ (or B+), 26 fat, 26 fatter, 27.5 fat (B fat) and even 27.5 (B) fatter. There have even been some options appearing with the 27.5 fat, not that my love for the Bontrager Hodag is in any way diminished.

I have also spent some time messing with mixed wheel sizes. Typically a bigger rim diameter on the front than the rear or a bigger tyre volume on the front than the rear.

Is it time for any conclusions?


27.5×4.5 (the Bontrager Barbegazi – and recently released Gnarwhal) is the undisputed best in super soft conditions. The huge diameter and massive paw print is quite frankly remarkable. However, it is a HUGE wheel – over 770mm in diameter. This is bigger than 29+.

26 fat does an admirable job of not being too big, hefty or cumbersome but offering good floatation.

B fat (as I have become accustomed to calling the Hodag and the new Maxxis Minion DHF 27.5×3.8) makes an outstanding front tyre in combination with a 2.8 or full 3″ rear 27.5 tyre. These tyres both have insane traction, in crappy or dry conditions, but don’t add too much rolling resistance when paired with a faster rolling b+ rear tyre.

B fat as a rear tyre is tricky: both options are very knobbly tyres and as such, rolling resistance is relatively high. If this is not an issue, or indeed a bonus, fire away, with the same up front or even a Barbegazi.

29+ is the king of roll. The effect is more pronounced on the front than the rear, but there is no doubting a bigger diameter, relatively fast tread will cover (moderately rough) ground like nothing else. Special mention here must go to the Bontrager Chupacabra for being both light and seemingly durable. Not the most aggressive, but adequate.

29+ front 27.5+ rear appears (to me at least) to keep a lot of the benefits of the roll over of a f+r 29+ but – for an indefinable and physics-defying reason – feels a little more playful. about the only factor that can really make much of a difference given that some of my bikes will have the same stay length regardless of which diameter is in use, is the radius and therefore how the bike behaves over different amplitudes of hits. The bigger radius might also potentially change lean angle in cornering.

The more I read about this, the more confused I become. For starters, within the parameters of a bike, the weight of the rider far exceeds the bike and thus acceleration differences are likely to be negligible. Wheel stiffness and response are probably very, very small effects also.

The difference in gyroscopic force and moment of inertia between the sizes would seem to be too small to be detectable at the speeds we ride at (with the wheel weights we use) and the same would go for the difference in effect of acceleration with the torque that can be applied (see here for a nice, plain explanation of applying torque to a wheel and then consider the force a human can produce and the difference in wheel diameter/weight).

I have also always wondered if the gyroscopic force of a wheel *not* in line with the direction of travel affects how a bike feels (consider sitting in a rotating chair and holding a spinning wheel then twist this and you will spin around on the chair. Surely, when we tweak that move in mid air, the two wheels rotating affects your position in the air? and would a bigger wheel exert more force noticeably?

And what of B fat front? Can the added weight and girth be detrimental? particularly with the Hodag – which weighs little more than a robust 29er tyre – I believe not. The combo of low psi and ~745mm diameter (the same as a good size 29er) mean you get the low pressure smearing grip, the lack of knocks from impact and good roll over obstacles, too.

It makes normal 29ers feel like a ‘cross bike.

No doubt as more sizes become available, (I’m looking at you, 27.5×2.6) and more tread patterns are brought to market, I will refine my thoughts.

At present, B fat front/B+ rear or 29+ front/B+ rear is the best performing wheel combo for my riding.

*it all stems from the Gazzaloddi, right?


8 02 2014

Over the last wee while I have been pondering bikes. Not so unusual, but things have been a bit more focussed than typical. The Vertigo Cycles fat bike is taking shape and some decisions regarding parts were required. It is not until you sit and look at the current state of play that you realise just how many ‘standards’ there are. One of the main decisions has been dropouts (front and rear) for this bike.

As Sean recently pointed out: “so just in case anyone is curious, fat bikes are made with the following FRONT axle “standards” 9×135, 15×135, 15×142 and 10×135 rear. Do you know where you can buy an aftermarket 15 x anything skewer? Me neither. 12×142 woulda been a good idea y’all if only because it already exists.

And the rear “standard” is: 10×135 offset, 12×142 offset, 10×170, 12×177, 10×190 and 12×197.”

Then things get more complicated still. This bike will have Paragon sliders, and I would like it to run a shimano saint derailleur as a direct mount (ie, the b-link is removed, the derailleur hanger is angled back rather than down and the whole shebang is stiffer and further out of the way for wheel fitting). Then, if i have my druthers I would like a 177mm thru axle, probably DT swiss. This means the drops have wee pockets to aid wheel placement and the thru axles are just great. But wait! The Paragon sliders are available with Maxle 12mm- a 1.75mm pitch thread- Shimano 12mm- a 1.5mm pitch thread and Syntace & DT swiss- a 1mm pitch thread. Some of these are available direct mount some with traditional hanger.

My head hurts trying to work it all out.

Then again, I have a 29+ bike coming from Kris at 44 Bikes. This will replace the Krampus, which I have enjoyed very much. Why replace it after barely a year of use? Well, the trick with the Krampus is that it was made to fit 73mm bb/135mm rear hub standard kit. Very cool, but if you take away this restriction, instead using an 83mm bb and a 150mm rear hub, add in a skilled builder experienced with fitting drive chain and fat tyres past short stays, you can sneak that fat knard into a 16.5″ chainstay.

Why wouldn’t you want to do that?

Truth be told, I don’t think I am going to fully realise the potential of 29+ bikes until better tyres become available. The Knard is fine until you hit wet roots, then it is an issue. It would be really nice to have a more aggressive tyre. The word is the Dirt Wizard will be around in spring – this new Surly tyre looks much more aggressive, but is likely to be a 2.75″ so we’ll see. If I had my druthers I’d have a 2.8″ Maxxis Minion DHF.

This bike will also have sliders. And a SON front hub, maybe 135mm, maybe 100mm.

So… here we go again….it is a *good* problem to have though!

Good stuff.

23 10 2013

Occasionally when I come to update my blog, the only things that spring to mind are domestic, work or even weather related issues. When this happens, it usually means that riding has taken a back seat for what ever reason. None of this stuff is of any interest to anyone, so the blog gets a bit neglected.

Sometimes though, there have been some intermittent points worthy of note: collected here are a few things that I have been messing about with and they may prove thought provoking to others. I know I would certainly value any opinions and input.

The bikes have all been working flawlessly. Several routine-maintenance-type updates were required, though. The Jones headset (a Cane Creek Jones ‘special’ 100) finally wore enough to begin creaking with a tiny amount of play after, what, 4 years? In this case, the angular contacts were a little worn, meaning that new bearings weren’t going to remedy the situation. After thinking options over, I decided to replace it with a dual griplocked King headset. Fitting this was very tricky indeed because the griplock system seems to grab the steerer tube under extremely minimal compression, easily done as you try to hold the truss and all the parts in the correct order, and pass the ‘floating’ steerer tube through. It is hard to explain until you try it, but eventually after splitting two of the green rubber o rings that help to fully snug up the griplock, I put a bigger chamfer into the steerer tube, which allowed it to pass through the second, lower griplock more easily.

The pewter colour is dark, but the sotto vocce graphic has been my favourite since it’s introduction. In use, smooth.

The next update was to pull the Knard/UMA snow rim/Paul Whub combo off the front of the Jones, replacing it with the original edge am rimmed wheel with a Maxxis Minion DHF 2.5/XC exo sidewall (rather than the heavy duty DH version) with dual compound tread. I have initially fitted tubes, because these rims are the older, non tubeless style, but even with a fairly beefy tube, it dropped 400g from the Knard/UMA combo. 400g! Initial impressions are that even running at 17psi, it is in no way as plush as the Knard set up, BUT the DHF has so much grip it may be worth persisting.

It is widely known now that fat bikes will take over the world and, as such, there have been a slew of carbon fibre rims shown at trade shows recently. In addition, various companies offer chinese made carbon 29er rims in various widths, including Derby, who offer a 35mm 29er rim.

In theory this would allow me to mount a Knard, whilst keeping the wheel weight down. I will wait to see how these rims perform for others over time. One concern I have is that they have drilled non-angled nipple holes, which makes them a bit tricky to build with a Whub, that has such wide flange spacing. I’m sure that before too long an even wider carbon fibre rim will be available, so I am going to keep my eyes peeled, and my mind open. 40-45mm would be ideal with the Knard I think. Meanwhile, the Rabbit Hole rims have been trouble free and once the wheels are rolling, the girth is maybe even a benefit, in a flywheel sort of way. After years spent trying to get light durable wheels, it is clear that there is a place for heavier wheels too.

Along with this on the Jones, I finally succumbed for the second time to making a bike tubeless. The Vertigo cycles Maul has the newer style enve tubless ready XC rims, which are a bit more puncture prone in the rough stuff than the AM rims, so I though it might be worhtwhile to try. I am using Conti Revo sealant, which is problem free at this early stage and a Conti MKII 2.2 bc/protection on the rear. I wanted to run a 2.4 version on the front but I couldn’t seat it with my Lezyne dirt drive, a ghetto set up, CO2 or a proper compressor. In the end I got hold of a 3C exo High Roller 2 which popped into place with minimal effort with the track pump and is superb in the mixed conditions I ride. I used to use Maxxis a few years ago exclusively and they are certainly back on the menu now. The High Roller is 900g or so and a real grippy tread and compound.

The Works Components thick-thin rings have been fantastic, finding their way onto BA and soon Maul as well. Several trouble-free months in the muck on the Krampus have been inspiring. If you need a high quality ring for a 1x build I would thoroughly recommend them. I have been researching the fitting of a 11-36 cassette with Saint 10 speed derailleur and I think I have a clear way to ascertain if this combo will strain the mech too much for these bikes. More on this in a stand alone post.

A very recent addition to a couple of bikes has been the new Jones 710mm loop bar. Basically this adds a bit (25mm iirc) to both grip ends, while keeping the looped section the same. I almost didn’t notice the difference after fitting them, which in some ways was good as I had anticipated lots of hang ups on the tight trees around here, but this has been a non-issue. However, when I look down, I do notice that my hands are around 1.5cm further back on the grips than I would normally be able to with the narrower, original bars. Overall, I like them a lot – a subtle improvement. Strangely, they are considerably better when it comes time to push the bike over very rough ground or up über steep pitches – very few strikes on my calf with the pedal. An unexpected benefit to me, but maybe not so strange. My understanding is that the Surly guys were keen to have the additional width when offering these bars with some of their bikes and this was off the back of a few gnarly off road adventures that involved a fair amount of off bike time as well as super tough, rocky terrain. In such circumstances, a wider bar is likely to shine for multiple reasons.

Last, but not least, I’m working on something new…a short trail. It will be called ‘Fearsome’. So far, I have cleared it once. More to add, but it will be a testing addition.