Rothrock-er

25 07 2018

I have ridden in Rothrock Forest , State College a number of times since the single speed worlds in 2005.

The riding here is rocky, intense and generally awesome.

I made good friends with some of the guys who live here and have met others over the years of visiting, or passing through en route to Harrisonburg, VA or elsewhere.

On day 2 or 3 I destroyed a maxxis Ikon but lets be serious, I was under-tyred for following a talented local into the chundery rock gardens. The replacement, a maxxis DHR has been amazing and not too draggy when I have needed to use dirt or sealed roads.

I purchased the tyre from Freeze Thaw Cycles, a superb shop filled with a knowledgeable and helpful team of staff and mechanics.

It also has a Grove Innovations museum! well worth a visit!

The Police bike lacked the doughnut holder that came with it – apparently they were thrown away by the non-plussed bike cops who used the bikes!

The bike has been a delight to pilot through these trails. Plus tyres are a real boon for rocky riding if you want to go hardtail or even rigid. A year on, and I wouldn’t change a thing on this bike. It is unreal.

So, a few scuffs have been added along with a bunch of smiles, brews and memories.

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Chainline versus cinch.

9 05 2018

A few years ago, I started running Race Face Next SL, SIXC and then Turbine cranks. The weight and low ‘Q’ factor of the Next are pretty awesome, but I (like others) have had a crank axle insert come loose. Others have had pedal inserts come loose: but, I do have 3 sets on the go which have been fine so far. I am always messing around with things and the shared axle crank interface between Cannondale Hollowgram and Race Face Cinch has had my attention recently. The Hollowgram SI are within grams of the Next SL and may be a reasonable alternative whilst retaining the unbelievable versatility of the Cinch.

A case in point.

The Turbine has a few millimetres greater ‘arm’ offset than the Next SL and I had a use for this. My 44 Bikes ~TNT~ had a Saint crank. The reason was the 83mm BSA shell (mated to a 150mmx10mm thru QR rear hub). There were only so many cranks that were available in this width and this width works well to get short stays and good ring clearance with 3″ tyres. It is a sturdy crank to say the least and the arms are quite bulky. I had been getting some medial knee pain on riding the 44 and I had isolated it to the crank.

On my Vertigo Cycles Kraken, Sean machined a SIXC 83mm crank axle so that the Next SL cranks would fit and work with the 177mm rear end. This used a flipped ring and thus gets a great chainline despite the ‘snow bike’ width rear hub.

A quick note – most geared bike set ups are biased to the smaller rear cogs. This is essentially to get stay/ring/tyre clearances in the manageable bracket. However, there is an argument that the ring should be more inboard at the front for todays gear spreads. Some manufacturers had started to address this when 1x systems became popular, offering aftermarket rings that were spaced to be slightly more inboard than usual.

Then, of course, rear hubs started getting wider and ‘boost’ then ‘super boost’ happened. Sean has been guiding me for years on this sort of thing and the bikes he has built for himself, others and me have often used 150 mm DH rear hubs with either flipped rings on 73mm shells, or ‘normal’ ring position on 83mm shells and as time has progressed and ‘plus’ tyres happened, moved even wider with flipped rings on the 83mm shell equivalent widths and 177mm rear hubs.

Phew.

I had been wondering about converting the 44 to the Cinch system. Interestingly, Race Face – perhaps due to the proliferation of 157mm “super boost” rear hub selection by several manufacturers (very sensibly, I might add – I have been advocate since 2010) – had quietly released a 143.5mm crank axle and also a 149.5mm axle for Next SL. The latter is equivalent to an 83mm BSA shell – the usual standard for a 150/157mm rear end – and had previously only been available in the DH orientated SIXC. The ring would normally be mounted in the inboard biased traditional position.

But you will know that often, direct mount rings can be flipped, if they are round, and there are different offsets of rings. The ‘normal’ is 5 ish mm towards the bike midline. Flipped, it is 5 ish mm outwards Why ‘ish’ ? well, different brands – a list would take too long – use a different offset – from Race Face’s 4.5mm to Absolute Black, Wolftooth and IIRC One Up using 6mm. There are others, but these are probably the major players.

Then there is Boost offset – usually around 3mm less. Soooooo….

If I took the BSA 83mm shell, which utilises the three 2.5mm spacer rings, which normally uses a 149.5mm axle equivalent, bought a 143.5mm axle (designed, most likely, for 148mm rear hubs?), removed 2 of the spacers (take away 5mm of the 6mm difference) and fitted BSA 30mm bb cups, a boost ring (add 2mm back to the chainline which with the shorter axle was 1mm more inboard) and the larger offset Turbines, I reckoned I would get great chainline and get the stay clearance and a slimmer, lighter and therefore more flexible crank on the bike.

In short, it worked.

This stuff is a minefield. I have another bike I want to do something somewhat similar with – my Vertigo Maul. It has a normal 73mm BSA shell, and I am going to use Cannondale Hollowgram cranks with (I hope at least!) a Wolftooth FAT CAAD (listed as -1mm but it seems to be more like +1mm) CAMO spider so that again, I can get a great chainline biased more inboard for the 150mm rear end on the bike.

I have been collecting data on all the different spiders and DM rings around, but the listed offsets are often either hard to find or seem wrong on measuring and thrown together with the different ring mount positions on different brands of cranks, different crank arm offsets and requirement for spacers etc, you need an obsessional trait to try and make it work. My advice? have the bits in hand, measure and then work out if it will fit. The downside is simple – cost.

But, with all the interplay between Cinch kit, Hollowgram and SRAM cranks (which have even more standards for where the ring mounts) you can make an über sweet, bespoke crank work on most bikes and get great chainline.

The bummer is giving myself a reason to pull King BB’s out of frames. Chris King deserve an award for making a bb that is seemingly impervious to scottish weather – no small feat!

Ok – this was probably as hard to type as it was to read and digest. If I have made any mistakes, I will correct them and fire away with questions if you are interested.





Maxxis Rekon 29×2.6″

29 01 2018

Yet another tyre size. Why oh why? whats the point? Blah blah blah.

I, for one, like all the different choices we now have in wheel and tyre sizes. You can really pick the one that works for you.

About 18 months ago, maybe longer, I built a front wheel for my trusty race bike – Maul – that could take advantage of 29+ tyres or fit a ‘wide trail’ tyre. I used an Enve fork so that offset could also be adjusted. I wanted to see how it all worked and figured the increased offset may work well with the bigger diameter wheel than the bike was designed for.

It was ok. The big tyre helped absorb some shock at the Wilderness 101, though I was still beaten up and with the release of the 29×3″ Minion series tyres, it gained preposterous front traction. To the stage where I had to replace the rear tyre with a Tomahawk, to get back some semblance of balance in terms of edge and cornering ability. Basically, with the Ikon I was using on the rear, or even the Ardent Race, the Minion wrote cheques the rear could not cash.

The geometry was always a little funky, though, and with the news of the Rekon 29×2.6″ I figured that would be the sweet spot. It would also drop over 300g from the front wheel and still be a reasonably absorbent and grippy front.

Well, I have a few hours on it now and its pretty good. It *is* light at sub 800g, but it doesn’t seem too fragile so far. The edge holds up and it certainly rolls fast.

I have 16 psi in it at present and doubt I want to go much lower.

It is in no way a plus tyre. That much is immediately obvious. The volume is just not great enough to make it behave in the way I have come to love with plus tyres in general.

The bike is back to its snappy, light, xc orientated ride and I’m happy about that.

As part of the project, I built a new Junglefox II 45mm internal rim onto a 100mm front hub. I have a notion to try the Minion DHF 29×3″ on the front of BA using an Enve fork. I feel that a ~50mm rim is ideal for true 3″ tyres. The bike is designed around a 120mm travel fork and normal 29×2.3″ wheel, so it might be just a wee bit steep at the front. We’ll see.

Interestingly, the build seemed much less tight than I am used to. Then it dawned on me that I hardly ever build with narrow OLD hubs any more! Still, 3x disk, 2x non, Sapim D lights and good balance and straightness should make for a decent wheel.





As the seasons ebb and flow.

24 09 2016

It is Autumn now. The daylight is retreating and the ground is becoming waterlogged and thick with fallen leaves.

I wanted to head towards the coast, for some reason. Lacking imagination for more interesting challenges, I took the Vertigo fatty, temporarily shod with plus wheels, to the Ardgarten loop.

It is not a particularly challenging loop, though the initial climb. westwards, followed by the climb up Glen Croe will keep your legs honest.

The trail over the Duke’s Pass is singletrack and at times offers a bit of challenge, particularly if it is as slimy on the rocks as I found it, but the views west are what took me there.

I probably ought to type something about my further exploration of plus tyres, as the fatty has allowed me to get time with a 27.5×4.5 a full 27.5×3 (on the rear) and 29×3 front and 27.5×3 rear. With interbike showing upcoming plus tyres from Maxxis that are on the knobblier end of the spectrum, *and* the growing 27.5×2.6 segment (which may well fit more 29″ bike rear ends), it is an exciting time.





Bontrager Chupacabra.

14 12 2015

Mounting a new tubeless tyre on a wheel that has a well sealed tyre already in place is an exercise in overcoming inertia. How much better will the tread *really* be? Will it seal again? How much of a pain is it going to be to remove the old sealant and, maybe, tape? Will you need a compressor?

I finally got over the hump and removed the Maxxis Chronicle from my Nextie Junglefox front rim and got to work removing the old Gorilla tape and recalcitrant adhesive. For this I use isopropyl alcohol and a Good Grips ‘deep clean’ brush set. This brush is stiff enough to remove the old adhesive and the hard rubbery ‘poker’ can be useful at lifting really obstinate sticky stuff.

Next, I apply a new layer of 3M 764 vinyl tape. I spent a bit of time recently researching tape characteristics and this stuff is stretchy, sticky and it comes off cleanly should this be required. It is also damn near airtight itself. I get it from Viking Tapes and although the order minimum is 6 rolls, you soon start to use it up.

Previously I used Gorilla tape, as mentioned, which has two drawbacks. Well, three. It doesn’t come off easily – leaving a lot of residue. It also seems to become boggy with sealant in time, and is quite porous, so I tend to need to keep topping up my sealant. Okay then, four drawbacks: it is also h e a v y. The difference between these 2 tapes (one layer) is ~40g. Admittedly, the Gorilla tape weighs only ~60g, but functionally the 3M is better *and* lighter, so it is a win-win.

Talking of weight, the Chupacabra is 860g or so and the Chronicle was just over 1000g (for the non-exo version, in this case). So all in all I lose 200g from the front wheel.

A blast with the Airshot and BAM! up it went.

It has been far from ideal conditions to ride recently and I am only slowly feelign my way back to any sort of regularity on the bike, but I am looking forward to seeing how the 2 compare. Volume wise, there is very little in it.





“The wide World is all about you…”

11 07 2015

Over the last few years, wide rims for bikes (road and mtb) have become more common. Back in the day, wide rims were the norm until a certain Mr Bontrager came along and re-rolled Mavic MA-2 rims from 700c to 26″ wheel size. Why? quality and weight: the aluminium rims were much lighter and easily as durable as the poor quality offerings available at the time specifically for mtbs. With wheels, there is always a balance point between tyre performance, weight and durability.

This re-rolled rim heralded a general move to sub 25mm external width rims. Tyres at the time were relatively narrow for the most part and with inner tubes, you were running 25psi+ in order to avoid (frequent) punctures.

Fast forward to Surly releasing the Pugsley with the ridiculous Endomorph tyre. Yes, DH bikes had arrived and wider rims and tyres were not unheard of, but they were too heavy for XC use for the most part. The Endomorph was designed for truly questionable terrain: snow and sand. Even with the 50-60mm trials or the Surly rims of the day, sub 10psi was a *maximum*.

My first experience of a Pugsley was riding hot laps on Shaggy‘s Pugsley at Bristol Bike Fest. The race course is baked dry, usually, in the summer and was very rooty with low amplitude rocks and rough trail in places. On the Pugsley, you could charge into the roots, overtake other racers in the rough next to the smooth line and bomb the descents with abandon.

There was definitely something to this.

In the proceeding years, I experimented with light tyres and lighter tubes as I moved to 29″ wheels. It was’t unusual for me to ride 600g tyres with 100g tubes. I flirted briefly with tubeless systems, but struggled to get my tyres of choice (Continental) to seal well. The sidewalls were very porous and the interface with the rim bead seat was loose.

In the end, I began to use a small amount of sealant inside very light tubes, but I’ll admit I was plagued with punctures.

Many years ago, I had procured a 50mm wide Uma ‘snow’ 29er rim. This was heavy, singlewall and of questionable strength, but it changed the tyre profile out of all recognition and if the interface had been better, I would have relished the low pressures I was able to run with minimal risk of pinching.

I stopped using this set up because the angle of the spokes combined with the relatively noodly rim made me suspicious it would fold in use. That, or the tyre would roll off the rim. Still, it was interesting.

Wider hubs, or at least flange spacing, make all the difference.

When Surly, again, led where others follow and produced the Krampus I knew I wanted to try the new, 29+ wheel size out. The raison d’etre for this frameset was fitting the, frankly, ridiculous Knard 29 ‘plus’ tyre. 700c but 3″ wide. Huge. Having messed around with Endomorphs and then Nate tyres on the front of my bikes for a few years and the brief spell with a wide rim and standard 29er tyre, the likelihood was that it would work well.

It was a game changer.

The full-on fat bike tyres of the time were heavy 1300-1800g. The Knard offered a lot of floatation, shock absorption and did so with a relatively small weight penalty over a normal 29er tyre: they weigh 1000g or so.

Yes, the sidewalls were thin and the tread pattern minimal, but in fairly short order there was reasonable choice on the market and with the Chronicle from Maxxis, EXO sidewall protection. 9psi and 35-50mm rims is a magic carpet ride for a rigid bike.

Syntace offered a simple exlpanation for the benefit of wide rims, which I would recommend reading, here. There is more discussion of value on the Open Cycles blog.

I started using carbon fiber rims a number of years ago as it is a fantastic material to make a light, strong, stiff rim from and this pays dividends particularly as the rims become wider. Indeed, it allows the whole ‘plus’ tyre thing to be fully realised. One of the main detriments of plus bikes is the added weight of the wheel at the outer edge. With the development of improved tyre-rim interfaces and tyre construction, tubeless is a snap. Light, wide rims paired with wide tyres make for a superb system for covering rough ground.

Lately, for 29ers, I have been looking seriously at Kappius’ offering, the 46mm external/40mm internal, cross country orientated KR-XCW-29, with a weight of 435g +/-15g and a good looking profile to facilitate tubeless set up. I have appended some links regarding the Kappius offering at the end of the post.

Things were turned round again with the arrival of the WTB Trailblazer, a 27.5+ tyre – in essence a 650b bead size, with a 2.8 to 3″ tyre, designed to retro-fit in 29er frames, but offer much of the benefit of the 29+ Knard. In the words of Bob Poor: “the idea was hatched in a seine skiff while catching 20,000 lbs of salmon every hour in the remote waters of SE AK”.

I am very glad Mark Slate at WTB took the idea on and had the tyre mould made. The 29+ is amazing, but in some instances the huge diameter is a slight hinderance. I’m going to come back to this; I have been having some interesting conversations with bike designers on the matter that do not feel concluded and I am also in the embryonic stages of working with Sean at Vertigo Cycles on a 27.5+ bike, perhaps like this one.

As much as you hear complaints that there are too many wheel sizes available at the moment, choice is a good thing to have.

“The wide world is all about you: you can fence yourselves in, but you cannot for ever fence it out.”

― J.R.R. Tolkien, The Fellowship of the Ring

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Kappius on facebook.

Kappius in Mountain Flyer.

Kappius on Fat-Bike.

Kappius on empty beer.

Kappius on Pinkbike.

Kappius on Vital mtb.

Kappius on Singletrack World.

Kappius on Cycling Dirt.

Kappius review on MarathonMTB.

Kappius on bikerumor.