Making use of Shimano RS785 shifters+calipers on a postmount road fram = impossible?

Discuss light weight issues concerning road bikes & parts.
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alcatraz
Posts: 2054
Joined: Mon Aug 29, 2016 11:19 am

by alcatraz

Hi ww

My friend has a road frame with postmount 160 mounting points for the disc brake calipers.

He also happens to have a set of nice shimano RS785 11s hydro shifters and flatmount calipers that he was planning to use with 160mm rotors.

To his surprise there is no common bracket that allows for mounting flatmount calipers on a postmount 160 frame.

The only bracket we've found is from ass solutions and they are like 80 usd which is ridiculous.

Looking over our options the question is what would be the simplest course of action to get this bike rideable.

1. Get some hydro postmount calipers a la mtb and connect to the road shifters? What of shifter compatibility anyone?

2. Get cable actuated shifters and brake calipers.

3. ?

Thank you for your help... I'm uploading some pictures to show the stuff.
/a
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by Weenie


mattr
Posts: 4601
Joined: Fri May 25, 2007 6:43 pm
Location: The Grim North.

by mattr

alcatraz wrote:
Tue Mar 19, 2019 8:44 am
1. Get some hydro postmount calipers a la mtb and connect to the road shifters? What of shifter compatibility anyone?
Can get any shimano MTB caliper and it should be plug and play, SLX starts at about €30 an end including all the hardware and pads. Might need to be careful with hose compatibility. (They should work, but might look odd if they have the wrong end fitting, worst case you might need new hoses. Or end fittings.)
alcatraz wrote:
Tue Mar 19, 2019 8:44 am
2. Get cable actuated shifters and brake calipers.
Expensive, new shifters, and new calipers, probably north of €400 for the complete set of Ultegra level kit, maybe more. Unless the RS785 are stil BNIB and returnable to offset the cost. Selling them second hand probably won't get you enough.

ooo
Posts: 769
Joined: Sat May 21, 2016 12:59 pm

by ooo

calipers with banjo connector route hose outside of the frame, it is not good for low q-factor cranks,
this is one of the reason why shimano changed BR-R785 (banjo) to BR-RS785 calipers (straight hose)

BR-RS785 ($29) - Shimano recommend this caliper (same as XT/SLX+straight hose)
BR-M6000 ($19) - same caliper as RS785, but use resin pistons instead of ceramic
'

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ms6073
Posts: 2730
Joined: Fri Jul 23, 2004 8:24 pm
Location: Houston, Texas

by ms6073

ooo wrote:
Tue Mar 19, 2019 10:29 am
BR-RS785 ($29) - Shimano recommend this caliper (same as XT/SLX+straight hose)
BR-M6000 ($19) - same caliper as RS785, but use resin pistons instead of ceramic
This. Here are a pair of Pre-owned calipers on Ebay.
Michael - The Anaerobic Threshold is neither...

wpccrunner
in the industry
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by wpccrunner


alcatraz
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Joined: Mon Aug 29, 2016 11:19 am

by alcatraz

Thanks, looks like we will put some shimano mtb calipers on the bike.

I'm curious to know if the hoses or their fittings are different between mtb and road on shimano hydro?

/a

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ms6073
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Joined: Fri Jul 23, 2004 8:24 pm
Location: Houston, Texas

by ms6073

alcatraz wrote:
Tue Mar 19, 2019 3:36 pm
Thanks, looks like we will put some shimano mtb calipers on the bike.
Depends on the model/vintage of the caliper. Why not go with the post mount suggestions previously mentioned?
Michael - The Anaerobic Threshold is neither...

kafreeman
Posts: 104
Joined: Thu Jul 23, 2015 8:46 pm

by kafreeman

https://bike.shimano.com/en-EU/product/ ... -R785.html

Post mount br 785. Running these on a cross bike you will need an adapter for the 160mm rotor.

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alcatraz
Posts: 2054
Joined: Mon Aug 29, 2016 11:19 am

by alcatraz

The guy already bought some xt m8000 calipers. How are the br785 different?

Now I'm afraid the brake hose fittings will be different.

The frame already has 160mm postmount mounting points. Do we still need an adapter to run 160mm rotors?

Thank you all very much!

ooo
Posts: 769
Joined: Sat May 21, 2016 12:59 pm

by ooo

he can use xt calipers with road sti using hydraulics hose with banjo connector

BR-M8000 = BR-M785 = BR-R785 (banjo) ≠ (straight) BR-RS785 ≈ BR-M6000
'

by Weenie


kafreeman
Posts: 104
Joined: Thu Jul 23, 2015 8:46 pm

by kafreeman

alcatraz wrote:The guy already bought some xt m8000 calipers. How are the br785 different?

Now I'm afraid the brake hose fittings will be different.

The frame already has 160mm postmount mounting points. Do we still need an adapter to run 160mm rotors?

Thank you all very much!
I don't think they are very different, just a different connection to the caliper.

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