Practically Classics Forum

Nice finish !

Do you realise that calpiers are either 'leading' or 'trailing' i didnt think you could simply swap them over.?
Stud pattern is the least of your worries as the weight of the car is placed on the centre spigot not the wheel studs.

Calipers are both leading and trailing since their effort isn't exerted in a plane which alters their trajectory with direction of travel. Unlike drum brake linings, which tend to have one trailing element in each rear assembly to lead when reversing, but provide far less effort. So no, it matters not one bit which side of the hub they're fitted.

The calipers fitted to both front and rear sides of each hub in the Dolomite Sprints that had four for racing were simply two pairs of regular ones, they work like that because no matter where the clamping is applied, it balances perfectly and would do so even if one were fitted in front and one behind, without the extra pair.

Cheap upgrade ? http://www.ebay.co.uk/itm/4-pcs-Univers ... 7738wt_768

Probably safer:

http://www.ebay.co.uk/itm/BOAT-ANCHOR-3 ... 3ce3b4b22a

Taken from the Willwood brake website.

Multi-piston calipers, normally with six or more pistons, have bore sizes that increase in size from front to rear.

This allows a pressure differential between the leading and trailing edge of the caliper, thus providing an even wear pattern along the entire length of the brake pad, hence it controls brake taper. This is necessary because incandescent material and debris from the leading edge of the pad is trapped between the pad and rotor; it tends to float the trailing edge of the pad off the rotor. A larger piston at the trailing edge of the pad provides more pressure to compensate for this debris buildup and keep the pad flat against the rotor.

So if you switch them over side to side the different size pistons will be on the incorrect side for leading or trailing.

Not so, because whichever side of the hub you fit the caliper at, that description refers to forward and back relative to the hub, not to the front of the car so even if you fit one above and one below, something which exerts its effort laterally, as calipers do, will apply the same effort at any part of the disc regardless.
Think of a trailing shoe. It's less effective in one direction because the distance from its fixed end to the drum surface means that when it's trailing, the contact period is long and the effort required far greater, but when it leads by virtue of the vehicle moving forward, the contact period is reduced by roughly the time taken for the drum to travel the distance between thae two points.

With the disc and pads, that distance is constant regardless of whether the pad and/or its means of applying that force upon it is parallel to the surface [of the disc] or is approaching it at an angle. I see why you might think otherwise because of the way in which that information has been presented, but it is quite misleading.

tractorman wrote:Probably safer:

http://www.ebay.co.uk/itm/BOAT-ANCHOR-3 ... 3ce3b4b22a

I have to confess, I was unsure about jimmybob's statement, but as it had some "technical stuff" to support it, I checked AP racing's site to see what they said and their 45 page PDF had some interesting reading that tends to support his comments. There are, of course, leading and trailing callipers (ie the caliper is in front of, or behind, the hub). However, they also show that some (if not all) of the 4-pot callipers have two sizes of piston - and the technical bit says much the same as the Jimmy's quote.

I suspect that a disc brake, even if less efficient in reverse, is self adjusting and still capable of stopping a car in reverse in a reasonable distance - even when warm and worn, so the "leading/trailing shoe" problem isn't repeated to the same extent in a disc-based system (but might become more obvious if you were trying to slow from 100MPH in reverse!).

I remember one or two of my old bangers (sorry, classic cars in waiting) used to have pads that wore at an angle - and they were all single pot callipers!