98> V6 And 2.5d Rear Brakes, Be aware when changing pads.

[Masterclock]

In 1998 Citroen changed the design of the rear brakes fitted to both the Late V6 and the 2.5L Diesel saloons, from about RPO 7476 onwards. The change involved using the standard swingarm fitted with the standard caliper, but fitted with a larger diameter disk. The disk was increased from 224mm to 232mm, but with the caliper mounted at the same radius from the disks center. This means that the disk projects 4mm further into the mouth of the caliper. To make use of the extra brake area they re-designed the pad, using the standard backing plate, with the friction material extended a further 4mm out towards the outside edge.

Just for the record, the estates have a different combination again, a larger disk at 251mm and a different caliper to accomodate it with much larger pads.

Great, this gives about 8% more friction area for the brake using standard bin parts from the production line just by changing the disk and pads. However, there is a major flaw with this approach.

The aftermarket brake suppliers took one look at the backing plate dimensions, saw they were the same as a standard pad and have listed them as equivalents in their catalogues. Worse still, the pads fit in perfectly and unless you notice the 4mm of shiny disk protruding past the edge of the pads you will probably be non the wiser that you have just lost 8% of the braking effort off each brake.

When I came to replace my rear pads last year I ended up going through Delphi, Mintex, and I think Lucas's catalogues to find the same results. All three manufacturers catalogues had a separate field for both the V6 and the 2.5 for 98 onwards models, recognising the fact that there was some sort of change, but the part numbers listed for the pads were the same as for standard pads.

The only catalogue that not only gave a different part number, but also gave a drawing with the correct pad dimensions, as well as the backing plate dimensions was the Ferodo catalogue. However, when the autofactor inquired as to availability they had non in stock and weren't prepared to make an order from Ferodo for such a low volume part. SNAFU.

I ended up going back to the Citroen main agent for the pads. The final twist in the tail, when I opened the Citroen packaging and removed the pads, they were made in the UK by Ferodo. No wonder their catalogue had so much detail.

[xmexclusive]

Hi Masterclock

Did they make any changes to the estate rear brake design with the 1998 car changes?
Is the any reason why estate rear calipers and pads should not be fitted to a car? This would at least then use standard bits that are freely available.

There was a similar change to the front brakes early in the Mk1 production run. Then both disk and caliper size were increased but again pad backing size was retained with friction area increased. It is possible to fit the wrong pads and not realise it. Some of the older small disks and pads have recently been offered as surplus on ebay but advertised as fitting all XM's.

Regards

XMexc