Centre lock vs 6 Bolt Discs Pro's and Cons

[AndreZA]

 

I found that I can use one finger on the lever with little effort in most cases to be able to break. When I had a 160mm up front I had to use multiple fingers and really break "hard" to be able to stop.

 

 

 

and I take all the other elements like tyres, riding surface and weather were the same? On lose gravel you will never get the same traction as you would on tar so it does not matter if you've got a 203mm disc and use all ten fingers.

[SwissVan]

 

Other than larger = more power, the smaller the disk the quicker the heat build up of which to much would not be benifical to brake operation.

 

Normaly this is not a problem on XC type courses where the decents are relatively short and hence the reason XC bikes get away with smaller disks (to save weight).

 

 

 

 

[philip.maree]

 

just something I dont get ...... how does a 180mm have more stopping power than a 160 mm ? More surface area ? Cause that does not make sense. You dont get 180mm brake pads' date=' so the surface area of the brake pad is still the same ...... and I am sure the "width" of the brake area on the 160 and the 180 are the same .....

 

 

[/quote']

 

This sounds like the cue for JB

 

Basically the bigger the rotor the less force you are required to apply to the brake. The smaller the rotor the more pressure or force you must apply to the brake compared to the larger rotor to stop.

 

[philip.maree]

 

 

I found that I can use one finger on the lever with little effort in most cases to be able to break. When I had a 160mm up front I had to use multiple fingers and really break "hard" to be able to stop.

 

 

 

and I take all the other elements like tyres' date=' riding surface and weather were the same? On lose gravel you will never get the same traction as you would on tar so it does not matter if you've got a 203mm disc and use all ten fingers.[/quote']

 

Fair comment. The conditions where roughly the same but what it does give me is more confidence to brake later with less effort into the corners.

 

That is just my preference though.

 

[Slowbee]

oh dear I feel a mechanic/physics course comming on ..... if your brake lever determines the force and its hydraulic then surely the size of the rotor cannot affect the amount of force you apply.

 

Swiss, how does the heat affect the braking ? Surely the heat just means your brake pads dont last as long ?

 

[AndreZA]

how does the heat affect the braking ? Surely the heat just means your brake pads dont last as long ?

 

 

 

 

It's not just that the heat glazes the pad surface but the heat is transfered to the caliper and the oil and it expands and braking becomes "soft/pap".

[Slowbee]

mampara - makes sense, but in a closed environment like your brakes, surely the expansion makes the brakes "harder" as the only place for the oil to expand is to push the piston out more than it should - so surely the oil getting warm makes the braking better ?

[SwissVan]

oh dear I feel a mechanic/physics course comming on ..... if your brake lever determines the force and its hydraulic then surely the size of the rotor cannot affect the amount of force you apply.

Swiss' date=' how does the heat affect the braking ? Surely the heat just means your brake pads dont last as long ?
[/quote']

 

The larger the surface area of the disk the more place there is to dissipate the heat. 

To much heat build up and it gets absorbed by the surrounding elements i.e. brake fluid, disk, pads all of which expand more than intended and can cause the brakes to grab or at worst stay engaged. The brake pad surface can glaze over resulting in a unsatisfactory braking surface which is difficult to get rid of i.e you buy new pads.

 

 

 

 

 

 

[Slowbee]

oh yes this makes me think of something else .. do 29er wheels stop faster than 26er wheels ... they also have more surface area (maybe the area of a 26er is big enough that it does not get hot enough to change anything)

[AndreZA]

mampara - makes sense' date=' but in a closed environment like your brakes, surely the expansion makes the brakes "harder" as the only place for the oil to expand is to push the piston out more than it should - so surely the oil getting warm makes the braking better ?

 

[/quote']

 

 

 

maybe "expanding" was the wrong word to use. I don't know the correct word but the oil/fluid becomes "soft".

[Slowbee]

Thanks Mampara ... I think I know what you mean .... 

[brussel]

larger disk stop better fro two reasons:

 

 

 

1. larger surface area means better cooling and you can work the brake more (give about 15% more surface)

 

 

 

2. The large diameter gives you a larger lever. For the same reason a long handles spanner can exert more force on a nut for the same force exerted by your hand. So the force of the pad on the disk is the same for all rotor sizes, but the bigger the diameter, the greater the leverage you have...

 

 

 

 

[SwissVan]

mampara - makes sense' date=' but in a closed environment like your brakes, surely the expansion makes the brakes "harder" as the only place for the oil to expand is to push the piston out more than it should - so surely the oil getting warm makes the braking better ?
[/quote']

maybe "expanding" was the wrong word to use. I don't know the correct word but the oil/fluid becomes "soft".

 

Boiled?

 

 

 

 

[AndreZA]

 

2. The large diameter gives you a larger lever. For the same reason a long handles spanner can exert more force on a nut for the same force exerted by your hand. So the force of the pad on the disk is the same for all rotor sizes' date=' but the bigger the diameter, the greater the leverage you have...

 

 

 

[/quote']

 

 

 

now that makes sense and I can actually see in in my minds eye how that can work.

 

 

 

Now imagine how much braking power the Buell bikes has got.

 

 

 

http://upload.wikimedia.org/wikipedia/commons/thumb/5/59/Buell_disk_brake.jpg/800px-Buell_disk_brake.jpg

[29pgc10]

just something I dont get ...... how does a 180mm have more stopping power than a 160 mm ? More surface area ? Cause that does not make sense. You dont get 180mm brake pads' date=' so the surface area of the brake pad is still the same ...... and I am sure the "width" of the brake area on the 160 and the 180 are the same ..... [/quote']

 

increased leverage: the further from the centre the more stoping power for the same effort.

 

mampara - makes sense' date=' but in a closed environment like your brakes, surely the expansion makes the brakes "harder" as the only place for the oil to expand is to push the piston out more than it should - so surely the oil getting warm makes the braking better ?
[/quote']

maybe "expanding" was the wrong word to use. I don't know the correct word but the oil/fluid becomes "soft".

 

The larger rotor the larger cooling area, quicker heat disipation = better breaking.

 

It is not the fluid that looses its properties but /in most cases/ the hoses that connect the lever to the caliper. In other words they expand under the presure and heat and do not return to their original state. Therefore it is advisable to change to braided silicon hoses /like goodridge/ to negate this.

 

OK, I am writing this from a automotive perspective rather than cycling one, but the principles do not change.

[brussel]

Ok had to google because I do not know much about Buell bikes...

 

 

 

holy cow! that thing must have the most amazing braking power with that size rotor....of course it has a marginally more powerful motor than my legs so the increase in weight should not be as much of an issue as on a bike