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holed discs ?
barrie sharp - 8/7/02 at 10:10 PM

Hi can anyone tell me the advantage of having holes in your discs, also the differance in performance between groved discs and holed discs.
not sure if its a cooling thing or surface area thing .
or how many holes?,do the pads wear uneven?
is more better or is there a set amount
Can anyone help me with the theory about this
thanks!

UncleFista - 9/7/02 at 10:46 AM

Holes or grooves in the disks are there (allegedly) to give the gases that are created between pad and disk during heavy braking somewhere to escape. Unnecessary in a car as lightweight as a "7" IMHO

David Jenkins - 9/7/02 at 11:32 AM

On bikes these holes and/or grooves also help to fling water off when it's raining.

Again, not relevant to most Locosts!

David

barrie sharp - 9/7/02 at 06:20 PM

has anyone tried drilling there own holes are there any problems with it.

Jon Ison - 9/7/02 at 06:49 PM

Done it for off road use, not sure i would want to for road use, then again i paid for drilled discs and the buggers came coverd in swarf, so i guess they took em off the shelf n drilled em......
not sure wot insurance assessor would do/say if you ever need'd him and he found home drilled disks......
Just for fun, i have 2 fairley new cortina dics in garage, which i have drilled and used on grass cars, can somone weigh a undrilled disc and post weight, will pop into garage later and weigh one,

unsprung weitght n all that......

Jon Ison - 9/7/02 at 07:01 PM

Just a tad under 3kgs on cheapo kitchen scales, (don't tell our lass) how much weight did it save ?

02GF74 - 15/12/05 at 02:45 PM

quote:
Originally posted by barrie sharp
has anyone tried drilling there own holes are there any problems with it.


this was discussed many years ago when I had my MGB.

the idea being increased surface area (maybe but you are not going to get them much air flowing through when the discs are spinning), somewhjere forthe surface water to go, less weight and deglazing pads.

you needed a stepped drill platform to turn the disc so the holes are drilled neatly. also the discs, mgb at least, are cast to you will need several drills asthey blunt quickly; 4 mm is the size that springs to mind.

also you want to drill the holes in a stepped fashion so the sweep over the whole brake pad.

JAG - 16/12/05 at 12:58 PM

Biggest issue I am aware of (and the reason they don't come as standard on your tintop) is the holes need to be chamfered on both sides of disc and the disc should be stress relieved.

If not the disc will crack around and between the holes which can lead to dramatically reduced braking efficiency

britishtrident - 16/12/05 at 05:30 PM

Holes should be chamfered but I think no need to stres relieve that will happen first time you warm them up.


It will help water/dust/gas clearance and help stop the pads glazing -- on cooling it will almost no effect.

On the downside it will make the discs more liable to warp. Is it worth the effort on a road or track day car --- no, on a bike or kart -- yes.

jon_boy - 16/12/05 at 05:46 PM

And dont forget to get all the holes exactly parrellel otherwise they will be unbalanced. Which could be a problem...

JB - 18/12/05 at 07:22 PM

I personally would not drill discs as holes are quite a bad stress raiser, and brakes are not something to take chances with.

The way to prevent the gas build up is to mill a couple of slots in the disc with a ball end cutter (approx 4mm). The slots do not go all the way to the edge.

Look at AP racing discs for ideas.

If you do drill holes, make sure they are chamfered and then get a ball bearing and place it in the hole and hit it. This peens the edge and reduces the likely hood of a crack.

Read Carroll Smiths books, he has quite a lot of info on this subject.

John