Wanted XM rear rotors

[Dieselman]

I think they do.
I had originally misunderstood the O/p's query and having checked the parts manual believe the listing for the 3.0 Es9j engined version to be incorrect, as it lists the disks being 232mm diameter. I believe this is an error and having cross referenced a number of manufacturers, it should read 224mm.
232mm is probably a typo and was meant to read 223.6mm, which is rounded up to 224mm.

To XMdownunder, have you measured the disks fitted to your car?

[citroenxm]

I must say I've never ever seen two sizes of discs for All ages of hatch.. except the estate obviously

[Dieselman]

I've also now checked the part numbers for the rear suspension arms, which is relevant as on the Xm the rear brake caliper mounts directly onto the suspension arm, not onto an intermediate carrier.
All Xm saloons use the same rear arm and brake caliper, so the brake caliper is mounted in the same position: 224mm disks.
All Xm estates use the same arm and caliper, so the caliper is again mounted in the same position, to allow for the larger disks and pads: 251mm disks.

Given the significantly larger rear brakes, hydraulic rams and suspension arm bearings, Citroen really intended the estates to be used as load luggers.
Quite a combination, capacity and payload of a van, ride quality of a Rolls Royce.

[citroenxm]

All Xm estates use the same arm and caliper, so the caliper is again mounted in the same position, to allow for the larger disks and pads: 251mm disks.

Given the significantly larger rear brakes, hydraulic rams and suspension arm bearings, Citroen really intended the estates to be used as load luggers.
Quite a combination, capacity and payload of a van, ride quality of a Rolls Royce.

But a larger caliper and therefore a different arm to the hatch.. so if one wanted more rear breaking power despite saloon setup being more then adequate they would have to fit estate arms to take estate calipers.. but. As we know that's needless

[Dieselman]

The rear brakes on all cars are more than powerful enough to lock the wheels, which is very dangerous, hence brake proportioning valves are installed...to reduce rear brake pressure as the rear of the car rises under braking.
Electronic brake distribution/Abs has taken over the requirement for a proportioning valve, which it is why it has a warning lamp and is checked as working at Mot time.

Hydraulic Citroens automatically regulate rear brake pressure as the rear brakes are fed from the rear suspension, so if the rear of the car rises under braking, the brake pressure reduces to ensure the rear brakes don't lock, but conversely as the payload increases, so does the brake pressure.
I said if the rear of the car rises under braking because assuming the brakes are functioning properly without air in the system, the rear of an Xm doesn't rise under hard braking, the car stays level due to the rear brakes pulling the suspension arm down and the rear suspension fluid being used to press the pads inward.
In addition the front suspension is designed with anti-dive suspension and the Hydractive system selects firm mode under hard braking.

[citroenxm]

Absilutley... I also 90 percent of the time found rear end lift was aircand a bleed up made a huge braking power difference.


Our aussie friends have a few posts to catch up on later..

[Dieselman]

Our aussie friends have a few posts to catch up on later..

Merry Christmas...

[citroenxm]

And to you also Will.. haveva great time!!

[XMdownunder]

I must confess my clutch slips when you guys start talking anti submarining servos but thankyou you all for your support and advice and I wish you all a merry christmas from downunder. By the way my rear rotors measure 232mm OD maybe that was an export to Oz special?
To Alex many thanks for the kind offer of your spare rotors I am thinking I will shop for 232s or otherwise fit a set of 224 and monitor for problems. My XM has done 309kms the rear rotors are now worn to 5mm with 3 mm wide lip and 1mm step on both sides, is possible they are the original rotors and have been dressed down to 7mm. The reference to the ORGA change date was provided in the earlier discussion thread rear brake rotors the link provided at the top of this discussion. Kind regards Stephen

[Dieselman]

I did see the Rp change for 2.5 Td, to the same as the V6 disks, but checking part numbers gives only 224mm disks, even Ate, who make the calipers.
I suspect lack of demand has caused supply to be curtailed.
The disks and pads changed to larger ones, so given that obtaining 232mm disks doesn't appear to be an option, simply fit the 224mm disks and suitable, slightly smaller, pads.

The 232mm disks are 4mm additional radius and the pads have additional friction material which gives the friction material increase of 200sq.mm.

It is dangerous to fit larger pads and smaller disks, as when the pads wear down the friction material overhanging the edge stops them being pressed against the disk.

Assuming the larger pads are available, if one really wanted 232mm disks, obtain a pair of 251mm disks and have them turned down to 232mm.

Edit:
I've checked the pre and post Rp7475 change and the pads have different part numbers, but the service replacement part numbers are the same.
When looking online the pads have the same size of friction material and the same manufacturers reference numbers.
The trailing arms and calipers are the same, so it appears the only change is the disk size.
My thoughts are to fit what you can readily obtain.