Planet X brakes - performance difference between CNC and forged.

[Globalti]

I have Planet X forged brakes on my old Roubaix and the performance is excellent. So I bought some of the CNC brakes for the new Roubaix and and sorely disappointed by the lack of power; they are dangerously weak and on one occasion I squeezed the lever so hard that the cable pulled though the little nugget thingy.

The bikes are almost identical and both use Ultegra levers with the same pull ratio of about 4:1. The rims are the same width. The brake blocks are un-worn; Shimano on the silver forged brakes and Swisstop on the black CNC brakes. The rims are in the same good condition thanks to regular cleaning and removal of grit from the blocks.

Looking at the pictures there seems to be a difference in the length of the rear operating arm, meaning that on the forged (silver) brakes the pivot for the camming lever is about 10mm futher outboard from the main brake pivot, adding considerable extra leverage. I telephoned Planet X to ask about this and they denied that there is any difference.

What do forum members think?

Planet X forged brake with excellent perfomance:

Planet X CNC brake with terrible performance:

Forged: distance of camming lever pivot from main pivot, approx. 40mm:

CNC: distance of camming lever pivot from main brake pivot, approx. 30mm:
(..and yes, the lever angle is different but that won't make a difference of 10mm!)

 

[Hacienda71]

Are you running the same blocks on both types of brake? I have found the blocks one of the biggest factors in terms of stopping power.

 

[Globalti]

Er, as I wrote.... Shimano on the good, forged brakes and Swisstop green on the poor, CNC brakes. I thought Swisstop green were good.

 

[Rob3rt]

Try both brakes with the same blocks.

 

[Hacienda71]

Sorry, shouldn't have skimmed the post. As Robert says use the same blocks on the two different callipers

 

[Globalti]

Just swopped the pads over - same poor performance on the black CNC brakes. I even put the green Swisstop pads and the new wheel on the old bike with the forged brakes and the stopping was excellent, so it's definitely the brake and not the pads or the rims.

 

[amaferanga]

I have the CNC brakes and performance is every bit as good as any other road brakes I've ever used. You've probably checked this already, but are the calipers centred? Also, how much gap do you have between the pads and rim? Is it the same with both sets of calipers? What about pad alignment?

 

[GrumpyGregry]

sliver brake cam lever is horizontal
black brake cam lever is sloping down
&
silver brake cable adjuster is screwed all the way out
black brake cable adjuster is screwed all the way in

figure out why that is, setup wise, and my money is on that's where the performance issue is. The angle of the dangle... it always matters when it comes to brakes.

but I am not an engineer....

 

[fossyant]

Get Shimano Callipers, those are fugly.

I don't think the PX brakes have the best performance.

 

[amaferanga]

Get Shimano Callipers, those are fugly.

I don't think the PX brakes have the best performance.

Have you used them?

 

[tigger]

I have the CNC brakes with Swisstop pads. No problem with the stopping power for me.

 

[fossyant]

Have you used them?

No chance, they are fugly Fugly stuff doesn't get fitted on my bikes !

 

[Kestevan]

I've got the CNC Brakes/Swissstop pads on the RT-57. Braking power is excellent - much better than the 105 calipers/Koolstop on the other bike. They can be a PITA to setup/centre though, and if they're not centred they're not too good.

 

[Globalti]

sliver brake cam lever is horizontal
black brake cam lever is sloping down
&
silver brake cable adjuster is screwed all the way out
black brake cable adjuster is screwer all the way in

figure out why that is, setup wise, and my money is on that's where the performance issue is. The angle of the dangle... it always matters when it comes to brakes.

but I am not an engineer....

At the weekend I'll have another fiddle with the setup and see if I can get the CNC closer to the forged brakes.

 

[Venod]

sliver brake cam lever is horizontal
black brake cam lever is sloping down
&
silver brake cable adjuster is screwed all the way out
black brake cable adjuster is screwer all the way in

figure out why that is, setup wise, and my money is on that's where the performance issue is. The angle of the dangle... it always matters when it comes to brakes.

but I am not an engineer....

I have the forged ones excellent when set right, the reply from GregCollins seems spot on, get the cam lever set horizontal or just below ( so that it is horizontal when the blocks contact the wheel ) on the cable side to give the maximum leverage on the opposite end.