Has anyone ever done an outboard disc conversion?
- Thread starter V8P6B
- Start date
I would first ask why, but you say to make access easier.
I think the way the suspension works relies on the breaking force being carried by the diff. I don't think the geometry would handle the breaking forces being handled throw link arms.
(now the kind of answer you may not have wanted
)
I would argue that it's not more work than some other out board disk set ups. Volvos and BMW's with rear disks like to use brake shoes operating on a small drum that's part of the disk for the hand brake. They get missed so much in services, my E36 handbrake failed because the shoes had fallen apart! So in this case it's not easier as the callipers and the carriers need to be removed just to service the handbrake.
Then look at the rear disks of the citron dx. I did a few and the bolts that hold them on are long and thin resulting in almost always them snapping off.
Ok, so the P6 rear brakes maybe harder than working on the fronts and harder than the rear of some other cars but it is really only a little harder. As it's only three bolts to drop the diff and two each side for removing the pads you could do them quicker than many other rear disk setups.
Changing the disk them self may be the hardest part but that's only really not too bad in my opinion. And as they stay in good shape much longer than say Ford's "mr easy to service" rear drums (not see any Ford where the auto adjusters work) I think the P6's are a very nice set up and I would not change them for the world, they get a bad rap because they are tucked up out of the way.
I think the way the suspension works relies on the breaking force being carried by the diff. I don't think the geometry would handle the breaking forces being handled throw link arms.
(now the kind of answer you may not have wanted
)I would argue that it's not more work than some other out board disk set ups. Volvos and BMW's with rear disks like to use brake shoes operating on a small drum that's part of the disk for the hand brake. They get missed so much in services, my E36 handbrake failed because the shoes had fallen apart! So in this case it's not easier as the callipers and the carriers need to be removed just to service the handbrake.
Then look at the rear disks of the citron dx. I did a few and the bolts that hold them on are long and thin resulting in almost always them snapping off.
Ok, so the P6 rear brakes maybe harder than working on the fronts and harder than the rear of some other cars but it is really only a little harder. As it's only three bolts to drop the diff and two each side for removing the pads you could do them quicker than many other rear disk setups.
Changing the disk them self may be the hardest part but that's only really not too bad in my opinion. And as they stay in good shape much longer than say Ford's "mr easy to service" rear drums (not see any Ford where the auto adjusters work) I think the P6's are a very nice set up and I would not change them for the world, they get a bad rap because they are tucked up out of the way.
I'm with Richard UK on this one, but for a different reason. I see no difficulty with the location, just the intricate design of the operating mechanism. As Richard says, it is easy enough to drop the diff or remove the calipers to work on them off the car. A lot of the bad reputation comes from people who have struggled to work on them in situ. I know that the mechanism shouldn't pose a problem if it has been properly looked after, but there are a lot of cars out there that haven't been, and then rebuilding the mechanism and finding replacement parts if required is not at all easy.
The P6 takes all the cornering loads up the drive shafts and through the diff into the bosyshell, rather than through the suspension as on a normal design. In fact braking and traction torque is resisted via the top and bottom links from the de dion elbow. But I do agree with Richard that it would be better to retain an inboard design.
I think the correct solution is to use different calipers with a more maintainable design. The key point being to separate the braking and handbrake functions. There are a number of proven solutions out there to achieve this. First up is Simon Owens solution of using a complete Jag diff, discs and calipers. Then Alan at Classeparts has done a number of conversions using Sierra calipers - standard to go round a non vented disc or Cosworth to go round a vented disc (which I prefer because of the inboard location). Problem with this set up (I don't know the numbers for the Jag, so can't comment) is that the braking effort Is increased relative to the Rover original. I define braking effort as piston area times pad area provided the discs are the same dia. In my view increasing rear braking effort is a bad idea - the brakes are plenty good enough overall already and greater effort at the rear only serves to destabilise the car under braking. It is possible to tackle this by varying pad material though - eg by using EBC red stuff pads or similar.
Alan also has a yet to be executed plan to use Audi calipers as well.
All these solutions finish up with a separate handbrake caliper acting on the same disc as the main caliper; which achieves the required simplification of mechanism.
Chris
The P6 takes all the cornering loads up the drive shafts and through the diff into the bosyshell, rather than through the suspension as on a normal design. In fact braking and traction torque is resisted via the top and bottom links from the de dion elbow. But I do agree with Richard that it would be better to retain an inboard design.
I think the correct solution is to use different calipers with a more maintainable design. The key point being to separate the braking and handbrake functions. There are a number of proven solutions out there to achieve this. First up is Simon Owens solution of using a complete Jag diff, discs and calipers. Then Alan at Classeparts has done a number of conversions using Sierra calipers - standard to go round a non vented disc or Cosworth to go round a vented disc (which I prefer because of the inboard location). Problem with this set up (I don't know the numbers for the Jag, so can't comment) is that the braking effort Is increased relative to the Rover original. I define braking effort as piston area times pad area provided the discs are the same dia. In my view increasing rear braking effort is a bad idea - the brakes are plenty good enough overall already and greater effort at the rear only serves to destabilise the car under braking. It is possible to tackle this by varying pad material though - eg by using EBC red stuff pads or similar.
Alan also has a yet to be executed plan to use Audi calipers as well.
All these solutions finish up with a separate handbrake caliper acting on the same disc as the main caliper; which achieves the required simplification of mechanism.
Chris
Demetris
Well-Known Member
chrisyork said:
I agree with Chris on this. Every time that i get my TC through our equivalent MOT test, it gets lots of compliments for the efficiency of the rear brakes, they say that they are more powerful in comparison with even the fronts of many modern cars, let alone the rears.
Increasing the braking effort at the rear of the P6 without some sort of pressure limiting valve it would lead easily to locking the rear wheels before the front ones during hard braking.
Mmm, a lot of food for thought there. I'm beginning to realise that as long as you can get the back end up, and now realising it is only 3 bolts to drop the diff, I'm beginning to be convinced that it's not all bad. I really hadn't even considered the cornering/braking forces issue. My car is almost ready for it's first MOT since 2005, and the only thing I'm a bit nervous about is dismantling/rebuilding, and servicing the rear calipers. They do look fairly complicated, but I'm going to be replacing the hoses and removing the calipers from the car to service them, so I'm hoping the nasty "under the car in a funny position" bit will be limited to removing/replacing the calipers, and sorting out the handbrake linkage. The rest can hopefuly be done on a bench. Cheers for the advice!
What they say ^ :wink:
The rear jag calipers are almost the same size as two pot front calipers, and have pads almost identical in dimensions to the two pot fronts. To rectify this I'll be using a brake proportioning / biassing (whatever they're called) to reduce footbrake effectivity on the rear. Ideally, I'd put the original calipers back on though.
Simon
The rear jag calipers are almost the same size as two pot front calipers, and have pads almost identical in dimensions to the two pot fronts. To rectify this I'll be using a brake proportioning / biassing (whatever they're called) to reduce footbrake effectivity on the rear. Ideally, I'd put the original calipers back on though.
Simon
The Rovering Member
Well-Known Member
There's no funny postion. Get the car up nice & high, all 4 corners if you can & a nice bit of carpet or a mechanic's trolley & with your legs sticking out from the rear end it's very comfortable & quite relaxing. You're already in a position to have a rest at any moment too.V8P6B said:
I've just removed the rear calipers from the Bruiser in order to put a re-conned pair on.
Hello V8P6B,
I agree that working on the rear brakes is not the most simple nor enjoyable of tasks, but then you really don't have to do it that often. Rear pads can last up to 50,000 miles, and once the the caliper piston bores are resleeved in stainless steel and a new kit fitted along with new hoses, it really should be at least 15 years before you need remove them from the differential for another overhaul.
If you indeed do have your heart set on moving the calipers and discs to an outboard position, then you should contact a Mechanical Engineer involved with automotive design. They will typically have qualifications such as BE, ME and possibly PhD after their name. MInd you the fee that you will need to pay for the consultation and detailed report will no doubt be many times the value of the car. This is the only way that you can be sure that doing such a conversion will not lead to a serious mechanical failure resulting in personal injury or worse.
Personally I would follow the advise of all of the entries above and leave it as the Engineers had originally designed it.
Ron.
I agree that working on the rear brakes is not the most simple nor enjoyable of tasks, but then you really don't have to do it that often. Rear pads can last up to 50,000 miles, and once the the caliper piston bores are resleeved in stainless steel and a new kit fitted along with new hoses, it really should be at least 15 years before you need remove them from the differential for another overhaul.
If you indeed do have your heart set on moving the calipers and discs to an outboard position, then you should contact a Mechanical Engineer involved with automotive design. They will typically have qualifications such as BE, ME and possibly PhD after their name. MInd you the fee that you will need to pay for the consultation and detailed report will no doubt be many times the value of the car. This is the only way that you can be sure that doing such a conversion will not lead to a serious mechanical failure resulting in personal injury or worse.
Personally I would follow the advise of all of the entries above and leave it as the Engineers had originally designed it.
Ron.
Here's a link to a blog I had going, not updated it for a while as the car's not given any more problems. But at the top it shows me doing the pads, further down it shows the two flex hoses being changed.
http://www.practicalclassics.co.uk/foru ... d137f53a20
But at the top it shows me doing the pads, further down it shows the two flex hoses being changed.http://www.practicalclassics.co.uk/foru ... d137f53a20