Hi all
Just looking at some breaks - is there a noticeable difference between 7.5s and 8.4s i have 12 inch wheels so dont mind either way but ones cheaper
Thanks

Generally speaking, you qwant the biggest brakes under you wheels you can get.
If there's not much cost difference, go the 7.5s.
If you had 13s I'd say go the 8.4s.

atm 8.4s are more $$$s

In theory (and correct me if I'm wrong) if they both have the same pads/surface area and calipers, the 7.5's as they are closer to the center of rotation so the disc is spinning slower BUT more force will be needed so it might cancel itself out .
8.4's probably have more upgrade options and could be cheaper as more were produced as standard on minis than the 7.5's.

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Respect mine and I'll respect yours.

Kenno, with the 8.4's the centre of pressure exerted by the pads is on a larger diameter circle than with 7.5's, which means they are more effective for any given pressure of application. This is also true of 4-piston calipers on the same diameter discs (albeit not as great a difference as 7.5->8.4) which explains why they're generally better than 2-potters.

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Simon

The adventures of an owner builder in the Tallarook Ranges

SGC is correct, however unless you have weak legs the ultimate breaking force is limited by the tires and not the brake...

IMO the reason for changing brakes is brake fade and probably only a problem in racing applications.
This is because all the stored (kinetic) energy in the car (ie great hulk of fast moving steel) is transferred to heat via the brakes. After numerous quick stops the brakes soon get pretty hot (think glowing red on the bathurst V8's...) and there efficiency drops because of this and eventually they won't work at all

- Stock drums are pretty poor with this fade, but can be made pretty good especially for light cars like mini's by using better shoe material and alloy drums and a few other tricks

- Next up is your disks which generally have better heat dissipation in standard form then you can go up to vented disks which are even better

Other factors like cross drilling, slotting, pad material, un-sprung weight etc. need to be considered when changing brakes...
I could probably talk for days on this but I'll stop myself...