disc brake advice..

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willcee
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Location: castleroe,co.derryUlster

disc brake advice..

Postby willcee » 6 Dec 2019, 6:53pm

Late to the party but acknowledge benefits esp on a heavy powered E machine.. so realising that I needed big tyres I had to go disc and did so with a set of Juin Teck which I liked, after going to decent XT pads, about 2 weeks ago a mate who deals with Planet X and got a blog saying Good quality 11 sp chains at humble money, he needed one or 2 for his factory Giant road & Carbon Orbea Gain so I had a look and saw an advert for RS 505 sti levers and RS flat mount disc calipers and jumped on them with a 11sp chain for less than 200.. happy days until they arrived and I soon realised there are 3 stds for disc mounting... mouse in hand I trawled all the UK sites that I had used in the past, ending up in Germany with Star bike for a pair of post mount BR 785's for 100 home and no one in UK had stock or if they had they were mad money wise...
So my questions are will the supplied hosing which is on the flat mt caliper fit the same into the new 785's.. they are not banjo fittings, but seem to be a newish std... also would it be best to bleed the calipers off the machine and then fit when bled. ... I have bled hundreds of car brakes , but not any bikes, I have a friend who is into this[ black art he says] and rather than trail the machine to his workshop just leave the sti's and the calipers and watch him do it.. nor have I the tools to carry out this operation... so I need a crash course in caliper fettling.. will

Brucey
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Re: disc brake advice..

Postby Brucey » 6 Dec 2019, 8:22pm

https://si.shimano.com/pdfs/ev/EV-BR-RS505-3901B.pdf

and

https://si.shimano.com/pdfs/ev/EV-BR-RS785-3743.pdf

tell me that BR-RS505 and BR-RS785 use the same hose and the same hose fittings, so I think you will be OK there.

Bleeding is not that difficult but it is a workshop-only job, so you don't want to be having a problem by the roadside. The usual shimano method is to purge from the bottom up using a syringe loaded with fresh oil, and to use a funnel to catch the overspill at the MC. This is best done with a bleed block in the caliper rather than the brake pads (which are easily contaminated with oil during bleeding). However there is more than one way of skinning a cat and all that.

cheers
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Redvee
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Re: disc brake advice..

Postby Redvee » 7 Dec 2019, 2:12am

You might need a BH90 Flange Nut to fit the hoses to the levers, I got caught out like that with my R7020 levers and post mount M7000 callipers. The part looks like this though it is available from plenty of places.

https://www.bike-discount.de/en/buy/shi ... ssr-905688

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willcee
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Location: castleroe,co.derryUlster

Re: disc brake advice..

Postby willcee » 9 Dec 2019, 7:16pm

MY BR785'S arrived from Germany over the friday evening DHL working late!! on opening could find no olives or nuts and the bleed screws are now hidden..WHY?? nor when examined were there any olives visible in the original kit from PX. a quick phone conversation to a friend who works for a Shimano service depot in a local bike shop, says they now insert the olives in the sti levers just cut hose to size retrieve the brass coloured inserts and insert them ,ram the hose home in the lever and sweeten up the hose nut to collapse the olives and seal everything up.. the bleed hidden tool items are or should have come with the new calipers, a black slim hose cover very thin about 8mm long.. found them.... works with the hose and the hose clamp i hope??? my bleed kit came yesterday and the oil today so when i finish setting the hose size on the frame and clipping it down again i will be in a position to bleed and have watched several vids useful to me a pilgrim at bike caliper bleeding.. cannot wait.. i can see me doing this a few times before i get it sorted....hope my temper holds.. no fags these days.. 4 months and counting.. will

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willcee
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Re: disc brake advice..

Postby willcee » 13 Dec 2019, 6:00pm

Armed with no less than 2 bleed kits, I called upon a friend to assist, now he's a great auto mechanic and a spark, he like me frowned when he saw the so called bleed ports on the new post mt calipers, you have to remove a small rubber bung for want of a better description , nor was there any sound descriptive or '' how to'' in the paperwork in either kit, I called my contact in the localish Shimano Tec Centre[ a LBS ] He says there's a small 7mmm plastic black gaiter hose like affair which you fit over the clear plastic hose then use that yellow 'thing' which slides up and when you fit the hose end into the port squash the ''black gaiter'' overhose up tight with the yellow 'Thing' and if you have an extra one ''Wullie'' bring it over to me ..I had 3 extra...he shouts...They cannot get me one anywhere in the Shimano world.. Madison have none!!! Shimano Technical excellence no doubt about it..!!!!!

Dear God My friend says ''the guys who thought this up came up with Di2''!!!! Are we going backwards?? it seemed that way to him and me.. what the hell was wrong with a normal bleeder nipple??? no better have a port and then a side mounted 2mm allen key opening screw.lol. we faffed about but stuck at the job filled from the bottom as directed, found that the olives were missing or misplaced in the sti levers sorted that after a trip to get new olives.left him a ''black hose gaiter thing''. tightened them 3 times and eventually got 2 tight dry joints then faffed about bleeding downwards and I got a'' good pedal'' ..he says.. we did this on both brakes and have a good brake mid way travel.. today i refitted the pads, and the brake is still mid pull, however i intend after a few light trips to rebleed both it seems that bleed blocks don't just let the pistons out far enough.. saga over.. Will

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Redvee
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Re: disc brake advice..

Postby Redvee » 14 Dec 2019, 1:35am

It took a few miles for my brakes to improve, they were good when they left the shop that I took the bike to for the final set up and the guy did say to bring it back after a few miles cause the vibrations from the road will get any air in the system to the resevoir. He had a second fettle of the brakes and whilst at it advanced the pads so they bite sooner in the lever travel.

AndyA
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Re: disc brake advice..

Postby AndyA » 14 Dec 2019, 9:22am

I really don't know what shimano were thinking when they decided to chage the size of the bleed port on hydro STIs.
The bit point of those brakes is normally in the middle of the stroke. When playing with a bike on the floor it seems too close and if you give the lever a death grip you might be able to pull the lever to the bar if your hands are strong. In use this is fine - the bite point doesn't move as the hydraulics self adjust for pad wear and if you pulled the lever anywhere near that hard you'd lock the wheel.
I find you can advance the pads a bit by removing the wheel/rotor, pulling the brake lever almost to the bar and refit the wheel/rotor. If it's too tight, push the pads back and start again. Much harder to get the brakes to not rub if you do this - it depends what annoys you more - rubbing rotors or close bite point

Brucey
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Re: disc brake advice..

Postby Brucey » 14 Dec 2019, 11:58am

if the hose runs are favourably oriented (which for rear brakes mounted on the chainstays, is unlikely, unless the bike is hung up at an angle) then any trapped air may gradually work its way up and into the MC reservoir and the brake feel will improve.

However the system still needs to be bled again in order to be 'perfect' because there should only be oil not a mixture of oil and air in the MC reservoir. If there is too much air in the MC reservoir the brake won't work when the pads are worn and even if there is only a little air in the reservoir, should the bike be turned upside down or even just lain on its side, the air may get into the working parts of the system and will turn all mushy again.

Any 'open' (self adjusting) hydraulic system will have a certain amount of dead travel at the top of the brake stroke; this is necessary to close off the compensation port in the MC, without which brake pressure cannot be developed. Then comes a little more travel which brings the pads square to the disc. Often the latter becomes less over time as the pads wear and the pistons become draggy enough that they no longer retract fully.

cheers
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