Differences between 256mm and 280mm calipers (girling / lucas 54's)

Evening all,

I was previously unable to get conclusive info on the physical differences between the 256mm and the 280mm callipers. I was given a pair of girling 54’s for nothing when I collected my 9” servo upgrade. Unfortunately the seller was not sure what car they came off of as his son had accumulated a bunch of goodies before losing interest their mk2 project.

I figured they were probably standard mk2 256 calipers as I did not recall the guy mentioning that the mk2 was a g60. Anyway, I decided to get a pair of tired 280mm calipers off an early mk3 which I plan to recondition. Now that I have received the 280mm items, it is clear the ones I got for nothing were indeed 256’s. I thought I would post this up for anyone else that may find themselves in a similar position.

In this pic, both callipers are side by side, 256 on the left and 280 on the right. The 280 items are noticeable chunkier and heavier:



With the calipers laying on their backs, a steel rule can be grounded through the cooling slot, in the next 2 pics you can see the differences in the carrier depths:
256mm calliper, around 97mm carrier depth:


280mm calliper, around 109mm carrier depth:


Another difference can be seen in the cooling slots, the 256mm cooling slot is around 60mm long as seen here:


And the 280 items are about 70mm long as seen here:


Its worth noting that the 256 items are girling and the 280 items are lucas however I would not expect that to be the difference between these particular dimensions.

Hopefully this will be helpful to someone.

Pippo
 

yeah as you say, there are 2 differences:
1. carriers are spaced out more to push the caliper out enough to fit over 280mm diameter disc
2. caliper is thicker to fit over 22mm disc and 19mm pad (vs 20mm disc and 16mm pad on 16v)

you can use 16v calipers on 280mm discs becasue of this, but you will need to use part worn 16v pads and/or grind the slider pin hex heads down a bit to give you enough room to squeeze em over. plus obviously 280mm carriers

did you need the 256mm ones? i could use a set.