Anyone know anything about disc brakes?

Most of the time I don't even use a wrench to true rotors. Pushing and pulling with (very clean) thumbs is usually good enough

Best tool I've found is this cheap thingy from SRAM (11.5015.014.060):

https://www.ebay.co.uk/itm/354302968824?var=0&mkevt=1&mkcid=1&mkrid=710-53481-19255-0&campid=5338268676&toolid=10044&customid=Cj0KCQjw9deiBhC1ARIsAHLjR2DswQ2UPqcsa7tk4LEs_aIHCV1QcWwnmH496omq3Y72X8XqYpbbpi4aAhFQEALw_wcB

This disc adapter, will it get me killed on a steel Dutch style cargo bike? The bike in question has roller brakes, and I want to sub out the wheel for one with a motor.

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The bike in question has roller brakes

If it already has roller brakes, you'll be fine if you use the same pick up for the brake torque reaction as currently.

Thanks Tester. Your answer leads me to another question, which is how I can ascertain the brake torque reaction for this frame. Is it something I can work out mathematically, or do I need to write to the manufacturer?

Is it something I can work out mathematically

It is, but you don't need to, if you use same pick up point as the roller brake used. They will have built the frame to accommodate as much torque as the tyre can generate.

The maths is coefficient of friction (assume 1.0 for rubber on tarmac) × normal force (i.e. the weight loading on the tyre) × contact radius (half the overall diameter of the tyre). For the rear you can assume the normal force is the static load, typically 50-70% of all-up weight, but for the front you should assume that the tyre is bearing 100% of the all-up weight because under braking the load transfers fully off the back tyre.

Sample:
150kg all-up, 70% on the back tyre, on Earth rather than any other planet, 700×40C tyre
1.0×0.7×150kG×9.8N.kg^-1×0.35m=360Nm

FWIW, you'd want a single grade 8.8 M6 bolt to be a mere 0.1m from the rotation axis to safely withstand the shear generated by a 360Nm torque.

Shimano disc brake pads.

I'm new to this.

Brakes are BR-R317. I've done a search on Merlin and I find three types that seem to be compatible.
GO5S RX
GO5A RX
GO3S

What's the difference? It's for a tandem so I don't mind paying for the best ones, but can't work out which that would be!

The difference is the compounds used in the pad material, although these all appear to be resin, aka organic. The other option is sintered, which include metallic particles. This is a good article explaining the difference.

Resin ones are meant to give better braking performance but wear faster, sintered are harder
wearing.

Thanks, that's interesting.

Make sure that your rotors are suitable for sintered/metallic. Some of the cheaper ones are resin only.

G is the pad shape, so all G work with your caliper, the number is the compound, used to be 01 was resin and 02 was sintered but there have been improved compounds since and they've gone up in odd numbers for resin, S or A is backing material S for steel, A for Alu, Ti for something completely obvious, I've not got round to learning why they've started adding RX to all of them yet. I'd generally recommend going for the 05S that fits unless you're riding MTB where sintered makes sense, or very big descents, where cooling fins can help, or both.

Thanks - that has really helped me to crack the code! I'll order some 05S now

RX means “resin, no cooling fin”.

Since you can deduce the compound type from the number and no Gxx has fins (they’re Jxx instead) it’s entirely redundant.

Ah yeah, I had read that somewhere and thought it was pointless so promptly forgot it.

Winter SFAB gravel or CX is probably better with sintered too.

Seem to have a bit of a leak from the rubber port on this calliper, any suggestions for how to fix? Thanks. Calliper is near enough brand new.

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Assuming the bleed port screw above it is closed properly?

Yes it is closed, or at least it is now. I'll continue to monitor. Also tightened up the nut on the hydraulic line.

Did I read somewhere that default brake pads on Spyres are pretty bad and worth replacing straight away?

Considering some to replace my BB7s as the pivots are knackered.

Yup.

Which of the shimano pad options here would work as replacement for juintech gt-f brakes? Several options in what looks the same shape, so not sure what the difference is… are the new saint ones thinner to go with finned inserts?
https://www.uberbikecomponents.com/category/513/E-Matrix-Disc-Brake-Pads

I've been using the stock pads since I got my Spyres. I'm happy enough with them but don't have anything to compare them to yet.

Question please; I've fitted a new fork to my gravel rig (10 year old Arkose) that has internal routing for the front brake hose.

To fit this am I right that I need to a) disconnect hose from lever b) cut off the old olive & barb c) thread hose through fork d) fit new olive & barb and reconnect to lever e) bleed ?

thanks

You don't need to do a).