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 ├╝ber 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.

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Bike packing bags.

17 12 2017

I have been subtly changing how I load the bike for bike packing. A little while ago, it became clear there are benefits to reducing the weight on the bars and reducing the volume under the seat – particularly if a dropper post is to be used.

As a result, a frame bag is needed to bring back the volume without loading it all into a rucksack.

So: a Porcelain Rocket Charlene (from Ride Auburn) which utilises a Wolftooth Valais dropper seat post guard (from MTBRiders) in order to give around 6l of storage that also still allows me 100mm of seat drop.

The Gas Tank and Tangle are essential and I also plan to swap in and out a full Revelate frame bag (all from Backcountry.scot).

The under downtube bag is actually a fork leg bag, from Oveja Negra – called the Bootlegger. I am mounting this to a bottle cage mount under the downtube with a Wolftooth B-Rad 4 plate I cut down to only leave 3 mounting holes. This reduces the overall unsupported length of the plate. It can also mount a King Cage Manything cage (from Justpedal.nl) if I want to use a dry bag instead.

The Revelate Harness, I have slightly modified to allow 4 point mounting to the Jones bars. This is so bomber that I am considering retiring my Revelate Sweetroll. We’ll see. The modification initially used the front ‘pocket’ straps, on which I unpicked the bar tacking I needed a way to utilise the webbing sewn to the Harness for a second set of bar mounts, with some extra foam spacers, but this was sub optimal, so I used some size 3.5mm locking oval carabiners. This also proved suboptimal on my recent overnighter – too much movement in the system. So I have changed it to use a simple wrap of double sided velcro with a Jones bar kit from Revelate and I am confident this is the way forward.

On the last overnighter, the Harness had my sleeping bag in a Mountain Laurel Designs cuben stuff sack (minimising the weight gain in using the Harness over the Sweetroll) and the Charlene had my wool longs and Mountain Laurel Designs Cricket Tarp/tent.

The Bootlegger held my Thermarest Neoair X-lite and some long wool socks and the frame bag held my tent poles (from Z-packs) Vaude ti tent pegs, MSR mini stove, a couple of large cuben stuff sacks to stow stuff overnight, an Opinel, a spare inner tube, another wool layer, a dyneema cord just in case and a wee bit of food. More food in the Gas Tank.

Everything else went in my Wingnut.

It all worked well and the bike felt lively, with plenty of stowage space.





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.