Anyone know anything about disc brakes?

Thanks! Before I pull the trigger… I've ordered a 5800 hydro groupset and it didn't mention that it came with rotors but do they generally?

Open up the piston carefully with flat headed screw drivers.

Nope, no rotor, recommend cheapest shimano one which work well.

where can I buy SM-BH90 in London today?

is there anything new/special required to bleed R8070 brakes? I have shimano road bleed kit that I use for R785.

ah fuck I need this too.

Likely not, if you need CL/160mm, Ribble have these Shimano Ice-Tech rotors for £14 each
https://www.ribblecycles.co.uk/shimano-rt70-ice-tech-centre-lock-rotor/

My front brake feels a touch sticky and it's made me realise I don't have anything in the toolbox for servicing hydraulic discs.

So, I assume I need a bleed kit. Anything else?

@edscoble, I have a pair of centerline rotor on my bike and after 6000km I can feel a small edge between the braking surface and the rest of the rotor.
From your experience I should change them ? Isn't it a little low mileage ?

What system? Got my SRAM kit from http://www.epicbleedsolutions.com/
It didn't come with a bleed block but you can make one out of old store cards.

If dealing with Dot fluid, if you don't have gloves already get a box of black mamba gloves from eBay. Then also some lint-free cloths & isopropanol alcohol cleaning fluid. Not sure if you need any of these for Shimano mineral oil.

Sorry, shimano 105

I haz the adapter but it’s in Gloucestershire

If you have bought the shifters it is in the bottom of the box.

Ah lemme check the box actually! Rookie #buyer mistake.

the BH-90 and olive is still an issue though ..

It’s almost certainly a sticky piston which you can fix without a full bleed. I don’t think you’ll need any additional tools either.

6,000km isn’t low mileage by a long shot! Change rotor and pads, not changing rotor can accelerate pads wear and increase chance of piston pushing out too much with a thinner rotor.

Great stuff

I already changed the pads twice but I thinked that a rotor would last longer than that. Thanks for the answer !

That sound about right TBH, some customer managed rotor at every pads wear, some haven’t changed their yet.

It’s varies on the condition and mileage you do, riding it through winter will accelerate wear a lots quicker, especially on disc brakes that’s likely to be contaminated by road grit.

Edscoble is right, you've done a lot of riding! And indeed if the road threw up grit onto the rotor then it will have acted a bit like sand paper and increased the rate of wear.

To expand a little on the question of whether you should change your rotors, Centerline rotors are 1.83mm-1.85mm when they are new. Sram, unlike some manufacturers, do not give a minimum thickness for safe use of their rotors, so we have to use common sense. As the rotor becomes thinner it gets hotter more quickly, leading to it warping more easily and affecting the performance of your brake fluid as it is compressed (called 'brake fade'). Also, because the metal is being worn by abrasion (as opposed to cutting) it becomes rougher and wears down your pad more quickly, as Edscoble says.

So that's the information you need to make a decision. If your notice any of the above symptoms, it may be time to change the rotors. However, be aware that the small edge you noticed on your rotors is very common and not a cause for concern in and of itself. If you can access a vernier gauge, measure the thickness of your rotors. I personally wouldn't consider changing them until they are less than 1.5mm.

Hope that's helpful.

Thanks for the advice ! You're both right, this discs are mounted on my do-it-all bike, and have seen a lot of abuse in the past year.
I'm using spyre so not subject of brake fade due to temperature. I managed a new set of pads this afternoon, I will source a vernier gauge to mesure them precisely.
Anyway, I find that the centerline worned out more quickly than an xt disc used in a similar way.

I will source a vernier gauge to mesure them precisely

Make sure you get one of these:

And not one of these:

Do Shimanos STI levers work with MTB calipers? I've got some (admittedly old) SLX calipers that have been in a tool box for about 4 years, could I buy some of the RS685 levers and use them on the road bike?

If the calipers have 22mm (white ceramic) pistons then yes.

if the pistons are aluminium edge, black center / 21mm then also yes but you now get more less mechanical advantage and levers move less for same brake action and probably feel too hard (but could work, never heard of anyone trying it).

Hmm ok, I'll dig them out and have a look. It might be a daft idea but I'd rather use something I've already got if I can. I'm trying to remember when I bought them, I think they're the first generation SLX so got to be over five years.

So in theory, less pull needed to engaged the brakes?

yes piston area is ~10% smaller so ~10% less fluid needed to engage. A bit like different lever pull with cable brakes.

...I dont know if it works in a good way.

A micrometer then :)