Shimano R8070 (and R8020) issues

[brucelee]

Hi all,
I got these fitted to a road bike and though they kind of rub all the time (especially when hot), they got worse today so I decided to inspect the pads. This is the first time I've done a disk brake system and the the first time I've done a hydraulic system (on bikes anyway). Anyway, watched a youtube video and removed the pads, measured them and the disks - still in Shimano spec (just). Ordered a new set of pads and went to refit the old ones. Couldn't get them in. Tried pushing the pistons back in with a plastic tyre lever and they go so far and stop. Slackened off caliper mounting bolts. Disks are centered correctly. Photo below :

Is the system just a simple hydraulic one (I'm just pushing against a hydraulic lock) or is there some thing clever going on here ? I read about them being 'self adjusting', but just assumed it meant self centering. Is it possible that the disks could have moved W.R.T. the calipers ? (remember disk newb) There a tiny amount of warp but nothing significant. If it is hydraulic lock, where do I bleed from in the scenario ? Why would there be a change in the fluid volume. Is it OK to use DOT4 or do I have to use the shimano stuff ?
Bit shocked by what appears to be corrosion on the rear callipers (conspicuously NOT on the front):

Is this to be expected ? Is it a thermal issue ? They will have been subjected to extreme rider weight/speed/long steep decent scenarios.
The bike came fitted with tektro disks and looking at the Ultegra ones designed to go with this caliper, it would appear that there is significantly more surface area available on the Ultegra disks to facilitate cooling and some attempt seems to have been made to create turbulence to improve this as well. If the cooling of the tektro disks were insufficient, could it effect the working temps of the caliper significantly ? Does anyone have a ball park watts figure for the dissipation capabilities of these brakes ?
As far as the metal vs resin pads is concerned, which is most cost effective (miles/£)(I've ordered some resin pads for £9 , can't find discounted metal pads (about £23?)), factoring in extreme rider weight/speed/long steep decent scenarios.
Really trying to avoid doing a strip down because of the nice weather and I have no bleeding kit.
The hydraulic joint on the R8020 levers sucks big time, digs right into the base of my thumb. I'm assuming everyone who has these has had the same experience. Are there any novel solutions for this ? I've chucked a load of bar tape round it but it's only half worked.
Cheers,
Bruce.

[peetee]

Do not use DOT. The brakes require mineral oil, of which the pink Shimano fluid is an option. The pistons will need to be backed off by removing the bleed port at the lever. Best to use the Shimano ‘bucket’ to keep the lever clean. Don’t force them back with a screwdriver or other metal object, use a nylon tyre lever.

[thelawnet]

brakes shouldn't rub. i find loosening the caliper bolts, grabbing the brakes (with pads installed) and then tightening the bolts still holding the brake lever tends to work quite well for centering.

new pads will require pistons to be pushed back to install, as self-adjusting means they moved in over time, but won't move out.

pistons AIR should go back flush with brake caliper body.

ultegra calipers are ceramic supposedly better for heat than resin.

bleeding requires a few bits but not too hard.

https://si.shimano.com/api/publish/stor ... 07-ENG.pdf

Shimano don't use DOT5, it's mineral oil. You can use theirs or anything else calling itself mineral oil brake fluid.

suggest to bleed before proceeding.

ultegra discs are not required, cheaper ones will be fine. the more expensive 'icetech' models are a metal sandwich which is supposed to dissipate heat better, but at expense of less wear.

asusme you have the right pad - cheaper Shimano brakes use a pad that is deeper (towards the hub) but narrower (around the circumference). The more expensive pad is wider but less deep, idea presumably is to reduce the disc size to save a gram or two. third-party discs probably tend to be deeper for compatibility reasons.

[Brucey]

with luck you will push a little air and MO (mineral oil) fluid out of the (open) bleed port when you push the pistons back and you will avoid the need to bleed the brakes fully. But it is always a risk.

One thing that is troubling to me is the thought that the brakes should have been OK when they were new, but now there seems to be 'too much fluid' in the system. That is not uncommon with a DOT system (the fluid soaks up water amongst other things, and fluid volume can increase as a consequence) but the same thing is not so common with MO systems.

Last time I checked hydro brakes were still heavier than rim brakes and shimano's posh discs/pads (without which their 'road' brakes are somewhat underwhelming) wear out faster than wheel rims and are more expensive to replace too. And as you have discovered the Hydro STIs/Ergos etc are usually warty great lumps..... So much for 'progress'....?

cheers

[Redvee]

Best to use the Shimano ‘bucket’ to keep the lever clean. Don’t force them back with a screwdriver or other metal object, use a nylon tyre lever.

When doing this put some brake fluid in the bucket. Not much is needed, only 1/2" at the bottom.

[brucelee]

brakes shouldn't rub. i find loosening the caliper bolts, grabbing the brakes (with pads installed) and then tightening the bolts still holding the brake lever tends to work quite well for centering.

I've done this a couple of times, the disks are a tiny bit off but they get a hell of a lot louder at the bottom of a decent.

new pads will require pistons to be pushed back to install, as self-adjusting means they moved in over time, but won't move out.

This implies the presence of some sort of reservoir and valve system, hence the question about how sophisticated the mechanism is. It seems to me that given the travel differences between a new and worn pad, they wouldn't have bothered with this, just let the lever have more travel and that would also serve as an indicator to the rider that the pads needed to be replaced.

pistons AIR should go back flush with brake caliper body.

don't know acronym 'AIR'

ultegra calipers are ceramic supposedly better for heat than resin.

Does this apply to the pistons or to the caliper body as well ? Could this explain what I'm calling corrosion in one of the photos ?

ultegra discs are not required, cheaper ones will be fine. the more expensive 'icetech' models are a metal sandwich which is supposed to dissipate heat better, but at expense of less wear.

I'm interpreting 'but at expense of less wear' to mean you get less wear out of them, is this correct ?
The pads fitted were L04C. I can't find any disks that look the same on the web, they look like this

I also just noticed there are some inline adjusters on the cables. One says shimano on it the other doesn't, they don't seem to operate as one would expect, the ridged bits don't move with reasonable pressure. Why are there adjusters on the self adjusting system ?

Cheers,
Bruce.

[brucelee]

So much for 'progress'....?

They're not much better at stopping than my Jagwire/Mavic CNC combination frankly. The origonal idea was to have wheels with super posh tubs rims - and the not have to penny pinch because of the cost of replacing the rims bit it's been such a palaver... And the disks/pads are soooo expensive.
Cheers,
Bruce.

[ElCani]

also just noticed there are some inline adjusters on the cables. One says shimano on it the other doesn't, they don't seem to operate as one would expect, the ridged bits don't move with reasonable pressure. Why are there adjusters on the self adjusting system ?

The thing in the top middle of the pic isn't an adjuster, it's a joint in the hydraulic hose that allows it to be split. Makes things a bit easier with internal hoses etc. The thing in the lower right of the pic is an inline gear cable adjuster.

What you describe as corrosion is... corrosion. The brakes look like they've seen road salt and generally look rather scabby. From what I can see of the exposed pistons, they look dirty/contaminated/damaged and it's possible that the seals and caliper that surround them are also in a bad way. A new caliper might be the solution here.

[brucelee]

So, nothing was jammed, I took the caliper off and applied pressure across the piston rather than just shoving a tyre lever in like on the video and it popped in easily. 3d printed a funnel but had no fluid and I cant remember if the lever bleed cap was open or not when I pushed in the piston. No fluid came out anywhere. Now there is more travel and it's gone a bit spongey so I guess some air got in (I actually prefer it a bit spongy but I'm guessing the amount of spongeyness would be difficult to control).

The thing in the lower right of the pic is an inline gear cable adjuster.

Wow, my brain just edited that out, why would they put an adjuster in for the front mech and not for the rear ?

What you describe as corrosion is... corrosion. The brakes look like they've seen road salt and generally look rather scabby. From what I can see of the exposed pistons, they look dirty/contaminated/damaged and it's possible that the seals and caliper that surround them are also in a bad way. A new caliper might be the solution here.

I'm a little worried about this, I've treated this bike with kid gloves. Assuming the caliper bodies are aluminum, why would I see corrosion on the caliper and not other components ? It's not in the firing line of the spray from the front wheel, and the front caliper and mechs show no sign of corrosion. Also, assuming the pistons are ceramic, are they more vulnerable to salt than the aluminum components ? I've got an older ultegra mech with the same blue finish on it on my tourer which has been subjected to this sort of thing for years with no sign of any corrosion ....

[Brucey]

The thing in the lower right of the pic is an inline gear cable adjuster.

Wow, my brain just edited that out, why would they put an adjuster in for the front mech and not for the rear ?..

there is usually a barrel adjuster on the RD itself, but not the FD, hence on some bikes (typically with no barrel adjuster built into the cable stops for example), an inline one is required.

Re corrosion; one thing that helps cause corrosion is wear debris that is thrown out of the caliper body when the brakes are on. This is both hot when it lands and (because it has metal particles in it) potentially corrosive when it mixes with water subsequently. Your rear caliper looks as if it may have been attacked this way.

If no fluid came out into your funnel when the pistons were pushed back (I hope the funnel seals properly BTW) then there is a chance that the brake is underfilled, and the brake will (quite suddenly) stop working properly when the pads wear or even the bike is turned over or just lying on its side for a while.

If the brake feels firm at present, I suggest in lieu of a full bleed, you add fluid to the funnel, and pump the brake pistons out a little, push them back, and repeat until no air comes out into the funnel. Push the pistons back fully and then reseal the system.

A little silicone grease on the exposed parts of the piston will probably help rather than hinder the performance of the brake. Once you have pushed the pistons back, excess can be wiped off so that there is no chance of contaminating the friction surfaces.

hth

cheers

[thelawnet]

The pad options from Shimano:

K - no fins
L - fins

02 - older resin compound
03 - newer resin compound, supposed to last longer
04 - sintered

Ti - titanium backed, lighter weight
S - steel backed
A/C - aluminium backed

So you have L04c. The K03S type should be cheaper.

I would definitely add some brake oil to the system and pump at the levers to try and get the bubbles out.

Apparently the Dura-Ace discs are not being used in the TdF, as they prefer the (slightly lighter) XTR models.

[Redvee]

This video gives the various weights of MTB v Road rotors.

[youtube]Xp1Y5kCri4Y[/youtube]