Bigger disks, but same calipers, pads etc ?
steve m - 8/1/12 at 04:50 PM
Just a thought, but
If i was to fit bigger 10 mm diameter disks, but retain the same calipers and pads,
and space the calipers out by 5mm
so that the pads were to sit 5mm further away from the hub,than they currently do
Would this affect the brakes, if so, better or worse,
or in real terms, would not make a jot of difference
Regards
Steve
ReMan - 8/1/12 at 04:54 PM
imho
In real terms not a jot of difference
In theory improved braking force for the same pedal pressure
Xtreme Kermit - 8/1/12 at 04:58 PM
I would expect the braking to be better, because you would be getting more rechanical advantage by having the pads further out from the centre of the
hub.
They would be no better at dispersing the heat though, because the pad area would nt be an bigger.
r1_pete - 8/1/12 at 04:59 PM
There would be an improvement, but whether its detectable is another matter.
The increase leverage 5mm would give is probably not worth all the effort, think of a stiff bolt, would 5 or 10mm extra leverage make that much
difference?
steve m - 8/1/12 at 05:06 PM
Thanks guys,
I was under the same impression, so will probably leave as is
regards
Steve
SCAR - 8/1/12 at 05:44 PM
quote:
Originally posted by r1_pete
There would be an improvement, but whether its detectable is another matter.
The increase leverage 5mm would give is probably not worth all the effort, think of a stiff bolt, would 5 or 10mm extra leverage make that much
difference?
It would if your spanner/wrench was only 10mm long to start with
If the disc is 250mm radius thats 125mm dia. the centreline radius the pads run would be about 20mm less so about 105mm radius
Therefore moving the calipers/pads out by 5mm (in the above example) would give about 5% improved braking leverage
Thats why race and performance cars use the biggest discs they can get to fit.
The increase in disc size is small but as a percentage of the original its significant enough to be worth while
Wether you need 5% extra braking is up to you and how you use the car
Also you get the benefit of the swept area of the pads for one revolution of the wheel increasing as the disc gets bigger This is because
circumferance = 2 x pie x radius, a 5mm increase in radius would gives a 5mm x 2 x 3.14 increase in circumferance
Going for a lie down now
[Edited on 8/1/12 by SCAR]
v8kid - 8/1/12 at 05:49 PM
Or you could get much the same effect by machining 10mm off the inside radius of the pads. That would give pretty well the same mean braking
radius.
Of course the pads would heat up quicker but that might be a "good thing" if a braking system designed for a heavy car is used on a light
car.
Other benefits are a reduction (marginal) in unsprung weight rather than the increase in unsprung weight a larger disc would have.
In addition if there is room to fit a bigger disc I presume you have room to move the callipers outwards? So do it anyhow. Usually there is a 5mm wide
unused band at the edge of the disc which should be utilised.
So in true locost fashion you can get twice the effect of a larger disc for bu66er all just a bit of fiddling about here and there 
Only disadvantage is the pads would wear out quicker and unevenly but how many locost cars wear out the pads anyhow?
Cheers!
Having read SCARS post thats about 10% for nothing
[Edited on 8-1-12 by v8kid]
iank - 8/1/12 at 05:49 PM
quote:
Originally posted by Xtreme Kermit
I would expect the braking to be better, because you would be getting more rechanical advantage by having the pads further out from the centre of the
hub.
They would be no better at dispersing the heat though, because the pad area would nt be an bigger.
In theory they would fade a little later as the there's more metal in the heat sink (i.e. disc), but once the'd faded heat dispersal would
be almost the same so they'd stay faded for the same amount of cooling off time as the current ones.
Handling would also be very slightly poorer are there's more unsprung mass and it's rotating which is even worse.
The extra rotating mass needs the brakes to work harder which offsets some of the theoretical improvement from the larger disc.