Mechanics and Fixing Any Questions Answered

If the fucking bike industry stopped being dickheads for 5mins this never would've happened.

This is why I always try to buy bikes with the same boring things - 68mm BBs, 27.2 seatpost, etc are a more important consideration to me than most other factors. I'm trying to fight "standards" propagation one silly purchase at a time. Used bikes are tickier though.

Yeah, I can get 2.6" MTB tyres in the Ogre. That explains why they went with a larger BB shell I guess.

Now I'm spoiled for choice... which set to I start with? How much are we betting that none of them work?

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Hmm, anyone got a "Park Tool LRT-4 - Shimano Direct Mount Chainring Lockring Tool" in west London? My BB tool ain't gonna engage enough to tighten the 12s chainring on.

https://www.amazon.co.uk/LRT-4-Shimano-Direct-Mount-Lockring/dp/B083WMQP91

This article mentions a plastic spacer that goes between crank and chainring, which obviously isn't on the fucking cranks I bought. How important is it? Something an LBS might have?

https://mountainbikevibes.com/how-to-replace-a-shimano-direct-mount-chainring/

Someone borrowed my tool and didn't return it, I actually know where he works so might pay him another visit...

That plastic spacer is only required for the XX2055mm chainline cranksets.

I've ordered a Shimano one. Figure I'll try and test fit these 12s cranks and if it looks like it will work, I'll get the LBS to tighten the lockring and then I'm good to go.

What about BB spacers? It's a 73mm shell and a 73mm BB so I assume I don't need any of their spacers? ASS u ME.

1 spacer on the drive side to take up the space of a chain guide.

Well, the 36T clears and the cranks look like they fit properly without any spacers (fck you and your new standards, world)

So, any reason I shouldn't install a new chain, ride to the LBS and get this lockring tightened?

Neither shop had the tool. #sadface

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AliExpress. Ztto jobbies, in different flavours of bearings

Definitely needs a spacer on the drive side.

Either that or a chainring with a greater offset from the likes of unite or wolftooth..

11-30 probably ok, it really down to the hanger length.

Why? It's not as close to the chainstay as the photo appears to show. I never found a lockring tool so I'm not going to bother putting the chain on until I know it will fly.

Because they're designed to have one, you'll have 2.5mm excess axle going into the NDS crank and slightly asymmetric cranks, which will probably do nothing if you can preload them without bottoming out the nut.

slightly asymmetric cranks

I have this with a pair of middleburns at the moment, it's actually better if I remove the DS spacer specified by Shimano for the BB

Asymmetric, as measured by distance from pedal eye to centre of seat tube, as I wasn't certain whether the chainstays would be symmetrical. IE the q factor is slightly different on each side

But it got me looking into it, and I found loads of comments on forums etc saying slightly asymmetrical cranks are completely normal and you'd be amazed how often this is the case. So I've decided to just not worry about it

I am no expert on square taper but I think it's particularly the case on these, as the BBs were often deliberately asymmetric? I think they often aimed to put the drive side crank where it needed to be for chainline and chainring/chainstay clearance, then just put the left hand crank as close in as possible, for narrower overall, but asymmetric, q.

Given we are talking about 2.5mm, there is a good chance your legs are not that symmetric anyway?

Hippy's chainline will be 2.5mm out, without the spacer, assuming (!) it's a correct match otherwise. But whether that will make any difference to anything is another question

But also - that BB comes with not 1 but 3 of the spacers, as it is compatible with both 68 and 73 shells - so you ought to have it somewhere

Yeah, I said it'll probably do nothing, most people's legs and frames are a bit wonky anyway.

That's a fuckload of grease for those splines (and yeah, I noticed it's the Shimano stuff, fancy) - did you smoosh it in and bugger off the excess before fitting the crank, or are you riding around with most of that between the crank and BB?

Swapping from 9/8th threaded to threadless; should the steerer tube od be the same and either fork freely fit in the head tube with headset removed?

Yeah.

Makes sense, thanks!

It's factory grease that I just boshed the crank through to see if it fit.

Why would a spacer be required on a stock 73mm install, is it coz these are newer cranks in an older BB? Looks to be about 50mm on each side of BB but cranks aren't installed coz I don't have tool to tighten DM chainring.

I've got older style M6000 2x cranks too. I could try them. Do they also need a spacer?

Why would a spacer be required on a stock 73mm install

68mm + 2x2.5mm spacers = 73mm, the other 2.5mm spacer is to take the place of a BB mounted derailleur or chain guard, it's kinda obsolete now, but they've stuck with it. 3 spacers on 68 and 1 on 73.

Because they're designed to have one

This is what I don't get - why build a thing that needs a spacer? I assumed the spacers were for silly crank variations, not Shimano cranks in Shimano BBs (but then I thought well hangon, now we have Boost and a bunch of other new shit even within the Shimano BB world, so I've no fucking idea.)

Ah, so the BB isn't 73mm? I thought because it was "MTB" BB as opposed to road it was already 73mm wide.

What should the BB measure externally when installed? 93mm?