Mechanics and Fixing Any Questions Answered

Got links to some suitable options then? I ran out of patience looking for stuff yesterday.

I looked and there's not a lot of room to do that. It'd also probably foul chainrings on chainstays (something else I'd not thought about coz modern bikes seem to have worked out the fat tyres thing).

To enjoy more silly standards, you could always change your freehub to one that takes a 10t smallest cog

But really the square taper Spa cranks idea is the best (apart from just paying the money for the middleburn chainring). BB length adjustable to give you whatever chain line/chainstay clearance is the best compromise. I have the Spa cranks on my all road type bike and zero complaints

I needed 165mm too, and as above, cheap 110bcd narrow wides are easy to find

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Didn't really look at SRAM - Coz SRAM is shit :) but also I thought they all used funny BBs?

I'd pretty much resigned myself to 170mm anyway but thanks, with these models, maybe I could poke around ebay or somewhere and find one.

This one actually looks half decent too
https://www.sram.com/en/sram/models/fc-apx-1w-d1

"Compatible with 135mm, 142mm and Boost rear spacing" how does that work then? They have different spindle lengths? Can I use a normal 11s KMC/Shimano chain with this?

Yeah, I never had issues with square taper cranks. I just thought since the Middleburn rings were so spendy, I'd standardise cranksets so I could pull stuff off one bike and have spare BBs laying around, etc.

What (presume NW) chainring are you using on that?

Crankset 165mm https://www.ebay.co.uk/itm/135449341938

Chainring up to 46T https://alugear.com/chainrings-1x/231-round-for-shimano-dm-12sp-gravel.html

One of these
https://www.superstarcomponents.com/products/ring-raptor-110bcd

I thought the 12s stuff was all for Boost and so too wide?

Also saw Alugear rings but ordered a much cheaper "Deckas Narrow Wide Chainring Round 38t 96bcd Asymmetrical Black" because I wasn't sure what cranks I'd end up with and the point of this was new cranks was supposed to be cheaper than just putting a larger ring on the Middleburns.

Someone posted these in my Wanted thread:
https://www.paulmilnescycles.com/Shimano-SLX-FC-M7100-32t-Single-Chainset-165mm

Would they work if I threw on a larger chainring? My brain is melting.

https://www.mtbr.com/threads/anyone-using-a-fc-m8100-on-a-non-boost-frame.1157479/

Ok, spec mentions 135mm OLD and 73mm BB so do we have a winner?
https://bike.shimano.com/en-NA/products/components/pdp.P-FC-M8100-1.html

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too wide?

Isn't that what you want if you want clearance for this large chainring?

I don't understand why you don't do this?? 52mm chainline is fine no??

Yeah, I guess. I've now ordered the cranks that @coventry_eagle linked (thanks!) but I'll hold off on the Alugear chainring until I know the cranks fit (they have a 10 day processing time and it's basically xmas now so everything is touch and go anyway)

I've also got "DEORE M6000 10 Speed Double Crankset. 36-26t Rings. 170mm Arms." coming from ebay. So I'm hoping with the 20 cranksets I've panic bought now, one combination will work and I'll sell off the rest of the stuff.

Yup, yes they would.

Would they work if I threw on a larger chainring? My brain is melting.

There are other funny variations of it, do not go for anything XX20 which is the ones for 148 rear.

Cool. Well, I now have 3 sets of cranks for the Surly and a couple of BB and chainring options. :)

It says it wants BB-MT801 but is the 501 the same thing just cheaper or do I need a different BB too.

EDIT: Just looked and I did buy a 73mm MTB BB for the GRX cranks. Maybe I bought them at different times and just wasn't thinking straight at the crank purchase time.

I presume there's a way I can work out what my chainring size limit will be? ie. approx how wide will the chainring sit + diameter of 38T ring or whatever?

SRAM is shit :) but also I thought they all used funny BBs?

Yeah, Powerspline for one and Dub for the other. Depends how much SRAM BB fuckery you're prepared to live with in order to get the crank length you want

Both 801 and 501 will fit, 801 will need the plastic TL FC25 tool which will fit any regular HTII BB tool, basically a step down washer.

Surly says Chainring Clearance 24/36/48t so you should be able to clear quite a bit more than 36T.

Nothing beats actually trying one on though.

What's currently on there?

Photo of full biek?

I presume there's a way I can work out

Yes, it's called maths. The pitch circle radius of a roller chain sprocket is very close to Pitch×Z/2π, then add 4mm to get the top of the teeth
(12.7×38/2π) +4=80.8mm, so your stays need to be 2×(chainline-4mm*) apart at a point 81mm from the BB centre

*half the ring thickness + clearance for flex

Surly says Chainring Clearance 24/36/48t so you should be able to clear quite a bit more than 36T.

They don't say what chain line, but I'm guessing 50mm for the middle ring as that's a traditional MTB triple.

maths

Yes, but I wanted the maths... AND the chainline of whatever mess I've bought.

Chainline is 52mm if this is to be believed:
https://bike.shimano.com/en-NA/products/components/pdp.P-FC-M8100-1.html

There's nothing currently installed. It was only after taking off the Middleburn square taper 32T cranks and removing the BB that I suddenly thought "hmm, I wonder how wide that BB shell is?" and that's when it dawned on me that the cranks were for 68mm and the shell measured 73mm.

your stays need to be 2×(chainline-4mm*) apart at a point 81mm from the BB centre

That would put the chainring miles out from the stays so I've probably done something wrong.

I've probably done something wrong.

The pictures in the SRAM frame fit specification PDFs might help with understanding 🙂

They have different spindle lengths?

No, they have optionally offset chain rings to give 47.5mm chain line for normal and 51mm for boost.

Right. Well, I've got a couple of Shimano cranks coming from ebay so they're going to get tried first and if I can't make those work I'll look at one of those SRAM options.

Ah shit, I still need a chainring for the Deore XT FC-M8100-1 cranks.