Hope rx4 with 9270 levers

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caballero
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by caballero

Are the new 12 speed Dura ace 9270 levers compatible with the hope rx4 mineral calipers ?

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ms6073
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by ms6073

Seems straight forward but the real question is hydraulic hose fittings that interface with the Shimano shifter. There are a couple threads on here asking similar questions about whether the rx4 calipers can be fitted with Shimano shifters to include R9170. There is a multi page thread on the Hope rx4 calipers and the last few pages are spent discussing pads and issues with pistons not retracting.
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Karvalo
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by Karvalo

ms6073 wrote:
Thu Jan 27, 2022 8:17 pm
Seems straight forward but the real question is hydraulic hose fittings that interface with the Shimano shifter. There are a couple threads on here asking similar questions about whether the rx4 calipers can be fitted with Shimano shifters to include R9170.
???
That's not even a question - of course they can. Fitting to Shimano road levers is literally the reason the caliper exists.

For the R9270 specifically I don't see why not. The RX4+ are already stated to be compatible with the GRX815 levers which were the first to get the full servowave treatment that the R9270 have now as well. That said, while I run them with GRX and love them for off-road power, I don't think I'd personally bother for a road bike. I can't see that I'd need/want the extra power and the extra cross section of the pistons does mean they simply do not retract as far as original 2 pot Shimano calipers. I'm not particularly heavy though, so YMMV.

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caballero
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by caballero

Thanks Karvalo !

I guess I kind of already knew the answer, but haven't seen anyone do it.
I already have the brakes and planned to run them with my 9170 but might upgrade to 12speed.

Something to think about.

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Cheers!
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by Cheers!

Hope needs to confirm it. Hydraulics work on the physics of the master cylinder's piston diameter (total surface are) and the caliper's total surface area of the pistons.

youngs_modulus
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by youngs_modulus

Cheers! wrote:
Sat Jan 29, 2022 12:44 am
Hope needs to confirm it. Hydraulics work on the physics of the master cylinder's piston diameter (total surface are) and the caliper's total surface area of the pistons.
Does Hope need to confirm that, though? Do you have some reason to think that the master cylinder diameter has changed between 9100 and 9200?

If so, why do you think that? And, since the caliper piston area hasn't changed between 9100 and 9200 do you think that the RX4 calipers wouldn't also be interchangeable between those two levers?

In other words, what exactly could Hope tell you that we don't already know?

MichaelB
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by MichaelB

youngs_modulus wrote:
Tue Feb 01, 2022 6:23 pm
Cheers! wrote:
Sat Jan 29, 2022 12:44 am
Hope needs to confirm it. Hydraulics work on the physics of the master cylinder's piston diameter (total surface are) and the caliper's total surface area of the pistons.
Does Hope need to confirm that, though? Do you have some reason to think that the master cylinder diameter has changed between 9100 and 9200?

If so, why do you think that? And, since the caliper piston area hasn't changed between 9100 and 9200 do you think that the RX4 calipers wouldn't also be interchangeable between those two levers?

In other words, what exactly could Hope tell you that we don't already know?
+1 to that.

The RX4's already work with all other generations of levers. Yes, technically they could update their 'compatability chart', but Shimano a while ago listed the 4 pot calipers and twin pots are compatible with other shimano levers, so whilst technically the piston sizes (and hence total surface area) are different, they all still work.

Have been running Zee MTB calipers and RX4's on various Shimano road levers for years now without an issue.

Hexsense
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by Hexsense

^ and does RX4 comparable to Zee in the stopping power and pad clearance?
I'm impressed with 4 pot m8120 caliper on my MTB and want to replicate that on my road bike.

MichaelB
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by MichaelB

Hexsense wrote:
Wed Feb 02, 2022 12:16 am
^ and does RX4 comparable to Zee in the stopping power and pad clearance?
I'm impressed with 4 pot m8120 caliper on my MTB and want to replicate that on my road bike.
They are a bit more fiddly to setup (as noted in the RX4 thread), but really happy with them now. Virtually same stopping power too

Edit : Main reason for changing is new bike had flatmount, and the flat/post mounts are ugly.

ccparkhill
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by ccparkhill

Curiously Shimano compatibility chart says R9270 shifters can only be run with R9270 callipers, though it does say running R9270 hydraulic callipers with R9170 shifters is fine. So perhaps they can't be run with any callipers?

MichaelB
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by MichaelB

ccparkhill wrote:
Thu Feb 03, 2022 9:34 am
Curiously Shimano compatibility chart says R9270 shifters can only be run with R9270 callipers, though it does say running R9270 hydraulic callipers with R9170 shifters is fine. So perhaps they can't be run with any callipers?
Shimano compatability charts says (or doesn't) lots of things.

If they publicly stated what will work, then they are liable. As with many Shimano specs, they are conservative (cassette max teeth and RD teeth difference are classics).

What you personally use and find works (such as Zee 4 pot calipers and road hyd levers as I have done with RS5685, R7000 and R8000 levers) is different.

pkaro
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by pkaro

If you really want ultimate stopping power, then you should look into the 4-pot XTR M9120 (post-mount only) brakes with 180mm rotors :). Go and read the whole hope RX4 thread, it really put me off using them because they're apparently very fiddly to set up and have a tiny gap between the calipers for the rotors.

As I find a bulky post-mount brake to be an affront to my aesthetic sensibilities I will just go with standard 2 pot shimano calipers using GRX Di2 levers for the benefit of servowave and nicer ergonomics

ccparkhill
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by ccparkhill

MichaelB wrote:
Fri Feb 04, 2022 12:37 am
ccparkhill wrote:
Thu Feb 03, 2022 9:34 am
Curiously Shimano compatibility chart says R9270 shifters can only be run with R9270 callipers, though it does say running R9270 hydraulic callipers with R9170 shifters is fine. So perhaps they can't be run with any callipers?
Shimano compatability charts says (or doesn't) lots of things.

If they publicly stated what will work, then they are liable. As with many Shimano specs, they are conservative (cassette max teeth and RD teeth difference are classics).

What you personally use and find works (such as Zee 4 pot calipers and road hyd levers as I have done with RS5685, R7000 and R8000 levers) is different.
I realise those charts are conservative, I just find it currious that they state that the current gen shifters will only work with current gen callipers, but that current gen callipers will work with previous gen shifters.

Karvalo
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by Karvalo

pkaro wrote:
Fri Feb 04, 2022 8:10 am
If you really want ultimate stopping power, then you should look into the 4-pot XTR M9120 (post-mount only) brakes with 180mm rotors :). Go and read the whole hope RX4 thread, it really put me off using them because they're apparently very fiddly to set up and have a tiny gap between the calipers for the rotors.
The 4 pot Shimano brakes will also suffer from smaller than intended clearance between disc and pad. As someone said upthread it's simple physics that more caliper piston area matched to the same lever piston will result in less travel.

Hexsense
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by Hexsense

^
On Shimano m8120, It's not really more caliper piston area though.
There are 4 smaller pistons that has the same piston area as 2 bigger pistons. Both use the exact same lever regardless if it pair with 2 or 4 piston calipers.

Additional modulation come from 2 piston engage the disc first, then 2 more later in the lever throw. This cause the pads to toe in.

Additional power then mostly come from larger brake pads and the 4 piston distribute the force in a wider but less tall area. In basic simplified theory, additional brake pad area doesn't increase braking power because the same power just distribute to a larger area but that ignore the extra mechanical locking and bonding between material as well as better distribution of force more toward outer edge of the rotor.
Shimano claims 15-20% power increase only, which is pretty realistic number that come from bigger brake pads but same piston area (which is shaped less tall but wider, closer to rotor's edge).

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