Poor disc brake performance

[DWM]

Hi All

I have a Croix de Fer with TRP HyRd disc brakes. I have never been entirely happy with them, but I guess over time I have got used to them. I have tried various different discs and pads (including changing to resin ones) but nothing really seems to make them any better.

I rode my other bike over the weekend for the first time since getting the Genesis last year, and I was amazed at how good the brakes were (I nearly went over the handlebars the first time I used them!). This bike has basic Shimano long drop calipers (R450) and Swissstop green pads.

Is this difference in performance to be expected? I am not expecting the disc brakes to be any better (in the dry at least), but I was very surprised at quite how much worse they were. Any suggestions?

Cheers

Dave

 

[ianrauk]

I would say that they disc brakes are not set up properly.

 

[Arjimlad]

That's odd - I have cable activated discs on one bike and calipers on the other and the discs are streets ahead if properly adjusted. Have you had them looked at by a LBS at all ?

 

[DWM]

Thanks for your replies. You have confirmed what I thought!

The problem is I have tried everything I can think of to make them better, having a good knowledge of bike maintenance, and following all the information online that I can find. I haven't been to my LBS as I'm stubborn and want to sort it out myself!

As far as I can tell they are adjusted correctly. The disc is true, the pads an even (close) distance either side, I've cleaned the caliper and piston, replaced pads and rotors, been careful not to contaminate anything, and I bedded them in properly.

I have a spare rotor and set of pads - I will start from scratch again and see if I can make them any better.

Cheers

Dave

 

[T.M.H.N.E.T]

You havent mentioned bleeding

 

[mythste]

I have TRP HYRDS on my Equillibrium. There is a bit of a weird phenomenon when you re-set the pistons that I seem to have worked out (all be it through trial and error rather than a traditional "scientific" approach, and perhaps someone with more brains than me can decypher it!)

Once the wheel is back on, I stand the bike on its back wheel and pump the brakes for about 5 minutes straight. Eventually its like something "catches" and then I can go through the usual bedding in period. If I don't do this no matter how much bedding in I try and do, its like someone gently pinching the disk and not much happens!

 

[Yellow Saddle]

You havent mentioned bleeding

Perhaps because that has nothing to do with brake performance?

 

[Yellow Saddle]

Post a picture of the discs. I want to see the surface texture, perhaps they are glazed. Also, you make no mention of bedding them in when you fitted new pads. Also also, did you fit the same class of pads (resin/metal) as what was on there previously?

 

[T.M.H.N.E.T]

Perhaps because that has nothing to do with brake performance?

You're right. Hydro brakes are no different when there's air in them.

How dare I..

 

[jowwy]

Perhaps because that has nothing to do with brake performance?

It does when they are cable operated hydros that havent been fitted correctly and may well have trapped air in the cylinder

 

[Yellow Saddle]

Brake performance has nothing to do with bleeding. If the pistons compress and retract with a single push of the lever, no amount of bleeding will improve the stopping force.

Disc brakes require much more force to operate than rim brakes because the coefficient of friction between the pad and disc is low and the amount of torque supplied by the small disc (vs large rim), is small. Therefore, if the friction changes just a little bit due to say, glazing, then the brakes perform poorly.

@DWM still has to answer a Q or two before we start bleeding.

 

[raleighnut]

I think I'm going to fit drum brakes on my next build.

 

[Yellow Saddle]

I think I'm going to fit drum brakes on my next build.

Pure carbon brakes with gold inserts on a Ti rim and spokes. Kewl!

I hope the bearings are at least ceramic.

 

[raleighnut]

Pure carbon brakes with gold inserts on a Ti rim and spokes. Kewl!

I hope the bearings are at least ceramic.

 

[Kajjal]

Maybe the pads or rotors are contaminated with oil or similar, this really reduces disc brakes effectiveness.