Mechanics and Fixing Any Questions Answered

Shimano chainrings don't tend to be compatible as they insist on having slightly different shaped fittings around the bolt holes. Shimano 12 speed chains work amazingly with their HG+ cassettes, I saw a test where the deore level ones wore more quickly than higher up, although I've not heard either are particularly fast wearing, not that it matters as you're an 11 speed cassette, so use an 11 speed chain which will be fine with 12 speed chainrings if that's what you end up with.

interesting - any you would recommend? i actually need to buy another chain for my 12sp group on my summer bike.....

I have a BNIB 11sp chain ready for my winter bike (which will have a 12sp crankset installed soonish)

too short

In tests, scientists concluded that there was no such thing*. The difference between 170 and 172.5 is not only too small to notice, it's also too small to measure reliably in terms of biomechanical efficiency because the noise floor is above the signal.

*Tests between 150mm and 200mm

i don't doubt that for a second. but in my head it makes a difference

FWIW, none of my bikes have cranks the same length. The only ones I actually notice being any different are 155mm. The longest are 175mm and I cannot tell the difference between 175, 172.5 and 167.5

You’re not wrong there.

Back in 2008, was convinced I have 170mm on the Bianchi Pista, and longed for a 165mm.

Turn out it’s 165mm and it’s just us bullshitting ourselves for no reason.

Converting a though axle hub to bolted?
My thought is
Pop out the end caps and replace them with top hat style spacers with an internal diameter of 10mm and an external diameter to match the hub bore that meet in the centre of the hub. Then have the thicker part at an external diameter of 20mm and a thickness of whatever is needed to get to 100mm or whatever is need for the fork/frame spacing. Then use a long m10 bolt remove the head and cut a thread into the end to bolt it together with nuts on each end.
A stupid idea or not?
I may have access to a technician for a few hours in the new year as they set up the new lathe.

Pop out the end caps and replace them with top hat style spacers with an internal diameter of 10mm and an external diameter to match the hub bore that meet in the centre of the hub. Then have the thicker part at an external diameter of 20mm and a thickness of whatever is needed to get to 100mm or whatever is need for the fork/frame spacing. Then use a long m10 bolt remove the head and cut a thread into the end to bolt it together with a nuts on each the other end

Your top hat spacers just need to register in the bore, the hub is expecting to be squished by the stock through bolt and should be equally squished by your new bolt. If they meet in the middle, the hub will have undesirable end float on your top hats.

Using a nut on each end of a stud is fine, but a bolt with its head intact is better. Definitely don't behead a bolt and thread the soggy end, it's more work for the lathe operator than just making a stud from raw stock.

Awesome! A bolt works even better for me too, I just thought it would look more normal. Good too know the spacers don’t need to touch. I can now see what you mean about float. Now to convince them to do it, instead of just turning up a random thing of no use like normal.
Cheers chap.

Dynamo woes. Always used to work, has now stopped working - both front and rear - without me changing anything. Wiring seemingly fully connected. The SP hub is only a few months old, the B&M lights are many years old. Possibly water damage as the front light is slightly foggy inside - although this has been the case for years without any ill effects.

What order should I start trying to diagnose problems in? I'm going to need to buy a multimeter aren't I

I'm going to need to buy a multimeter aren't I

Unless you have some bulbs and wire knocking around then it’s probably your best route.

So I would then test 1. voltage from the hub connector, and if that works, 2. voltage at the end of the wire to the front light, and if that works, 3. voltage at the connector from the front light to the rear light wire, and if that works, 4. voltage at the end of the wire to the rear light, and if that works, it's the rear light?

I know nothing works if the rear light is connected the wrong way around, so presumably a fault anywhere in the system means it'll all be off

I've tended to use wire and bulbs to test stuff, like, connect the front/rear lamps as directly to the hub as possible and see if they light up, probably really only used a meter to check for a circuit from one end of the wiring to the other.

I'd start with that as it seems unlikely the hub is dud if it's that new. If the wiring checks out then you probably should be able to get some illumination of the lamps with some AA batteries?

I remember always having 170s and then noticing a slight difference when a had a pair of 175s; a hair easier to push a taller gear but a tad harder to spin. I liked the extra leverage but not the lower... redline? Had 172.5s ever since, which as you say is hard to notice the difference, but it's obviously a good compromise between what I liked about the sizes either side.

Then again, I'd probably be among the first to notice, given I despise cassettes without a 16t, and am not keen on ones without an 18t... And a jump between 11t and 13t makes me shake my head in wonder. Been wanting to mod some Ergos to friction in order to shift a CVT forever.

Is anyone else noticing chains rusting much easier these days? Have always generally used KMC in the shop.

Same here. I've got cranks from 165mm to 175mm on various bikes and don't really notice the difference. The only ones where I notice the difference is the 135mm cranks.

easier to push a taller gear but a tad harder to spin

Yeah, that's just maths. It's like the difference between a 52T ring and a 53T*. Crank length is part of your overall gearing, so of course you notice a change in crank length if you don't also change some other part of the ratio chain to compensate.

When you eliminate the change in gearing, nobody can detect a 2.5mm change in crank length in blind tests. People can't even tell if their left and right crank lengths differ by 2.5mm.

* (52/53)×(172.5/170)=1.00 😀

Except it stands to reason that the longer the crank, the harder it is to spin, even if you change the gearing to compensate, right?

And there must be a flipside to this, otherwise the ultimate crank length would be 1mm.

I don't understand why having longer cranks isn't better. Greater leverage fulcrum¿ (brain can't think of the right word)of the load so easier to pedal for higher gear.

Except it stands to reason that the longer the crank, the harder it is to spin, even if you change the gearing to compensate, right?

But you don't have to spin, because you're pushing a bigger gear. Within the ordinary range of crank lengths, your speed for a given effort is the same if the gain ratio is held constant.

easier to pedal for higher gear.

But you have to move your feet faster because they're going in bigger circles. Power is force times speed. There's no free lunch.

there must be a flipside to this, otherwise the ultimate crank length would be 1mm

For typical riders, biomechanical efficiency is very nearly flat (±1%) from 150mm to 200mm, but starts to drop more and more quickly outside those ranges. At the long side, it's probably an issue with range of motion, you can't apply the necessary force across such a large joint articulation angle. At the short end, you run into timing/latency issues as the muscle firing repetition rate exceeds what is viable for such a large mammal. You'd need to be a hummingbird to hit the 3000rpm necessary to exploit 5mm cranks🙂

Give me a big enough lever and I can move the world ;)

I think I understand (get) the physics of the situation but don't comprehend how it works. I'm putting this down in the category of science not understanding why cycles stay up.

Strange one. My 10 speed deore derailleur has stopped shifting into two smallest cogs, even with the cable tension completely backed off.

Any explanation other than the derailleur has got bent? It's on my MTB which gets bashed about a bit in cars/the shed

don't comprehend how it works

I assume you mean the biomechanical bit, rather than the levers. Put simply, within the narrow range defined by common crank lengths, the product of force exerted by muscle and the speed of contraction is very nearly constant. I imagine this is because power is limited by the fuel delivery rate across a range even larger than the above.