65 p6 caliper problems

Dave1966

Dave1966

Member
Hi, a couple of questions.
Trying to change the pads on my 65 p6 has revealed I'm going to need replacement front calipers. The part no. Is 688382 and made by Dunlop which were the same as fitted by jaguar. I suppose they are interchangeable, (jag to p6), because it's the same part no. Or alternatively does anyone know a company that will rebuild them.
Thanks
 
I believe MGBD do exchange on these. This will almost certainly be cheaper than a Jaguar specialist. Failing that, I'm sure they would be able to recon them. But out of interest, what is the issue with them?

Whilst they were common to Jaguars of the period, they won't be generic items. The commonality only really applies to the castings. The fittings will vary from model to model, so you may find compatibility issues on things like mounting points, flexible hose location etc.
 
Hi. One caliper on the driver's side is really stiff and now ive moved it there seems to be a small leak, but the other one refuses to move after being pushed back in with the vice. I've not touched the passenger side yet, but I can only assume it's going to be the same. To make things easier I looked at reconditioning my calipers. That works out between £80-90 per caliper + vat. Is that about the right price? Also can I fit later calipers if I change the back plate?
 
For that money I would look into updating to Girling type brakes. The late chassis (suff E) have the same uprights as the V8s, and there should be many more girling calipers around. Girling kits complete with pistons are around the same price, but seals alone are cheap.
 
jp928 said:
For that money I would look into updating to Girling type brakes. The late chassis (suff E) have the same uprights as the V8s, and there should be many more girling calipers around. Girling kits complete with pistons are around the same price, but seals alone are cheap.
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Several people seem to see 'Girling Front, Dunlop Rear' as the optimum combination, although I'm not sure this isn't largely driven by practical considerations due to the broader availability of Girling fronts and reduced delicacy and complexity (relative!) of Dunlop rears.

I believe the front discs would also need changing to accept Girling calipers.

For what it's worth, I'd stick to 2-pot Type 16 Girling calipers if I was upgrading from Dunlop. The V8 3-pot calipers also require the front hub to be changed as well as the disc. You would also do well upgrading the wheels to the wider 5.5J section to increase surface contact area, as I personally find Girling braked 2000s 'over braked' to begin with (easy to lock up), and the V8 brakes would only add to this, especially as they were designed for a car that is both heavier and had wider wheels/tyres. There's also the issue that your brake servo would not be matched to the bigger brakes and so give a very different pedal feel.

So personally, I'd have the Dunlops rebuilt, or transpose later Girling 4-cyl front legs onto it for ease of conversion, and then work out what pipe unions needed to be changed.
 
Thanks, that's what I thought too. It's a lot of work for a car that won't be used much. I'd like to keep it as original as possible.
 
I converted Bruiser to 3500 front brakes. I bought them as complete assemblies with pillars & it was a very straightforward job apart from the backplate bolts being seized. I can't say l noticed any difference in pedal feel but then in concept, Bruiser is a very different car to Dave's.
 
redrover said:
Several people seem to see 'Girling Front, Dunlop Rear' as the optimum combination, although I'm not sure this isn't largely driven by practical considerations due to the broader availability of Girling fronts and reduced delicacy and complexity (relative!) of Dunlop rears.

I believe the front discs would also need changing to accept Girling calipers.

For what it's worth, I'd stick to 2-pot Type 16 Girling calipers if I was upgrading from Dunlop. The V8 3-pot calipers also require the front hub to be changed as well as the disc. You would also do well upgrading the wheels to the wider 5.5J section to increase surface contact area, as I personally find Girling braked 2000s 'over braked' to begin with (easy to lock up), and the V8 brakes would only add to this, especially as they were designed for a car that is both heavier and had wider wheels/tyres. There's also the issue that your brake servo would not be matched to the bigger brakes and so give a very different pedal feel.

So personally, I'd have the Dunlops rebuilt, or transpose later Girling 4-cyl front legs onto it for ease of conversion, and then work out what pipe unions needed to be changed.
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I took the plunge and ordered 4 new calipers. £455 Inc vat.
 
Yes, I want to try and keep it as original as possible. Got my new pads, (and calipers), from MEV spares £14.95 + £4.95 p+p. Seems a good price to me. Spoke on the phone and seems like a fair bloke. When I took the old calipers off, the pads had hardly been used, so I thought they're going to be at least 20 yrs old so change them. That's why there wasn't much braking at the front, the pistons had seized.
 
Dave1966 said:
That's why there wasn't much braking at the front, the pistons had seized.
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What normally happens is one piston seizes, then gradually bends the disc towards the seized side, so wearing those pads, eventually snapping the disc around the hub.
 
Have a Haynes on the Jag D-type - original users of the Dunlop disc system. Back then they didnt realize that the right seal shape would pull the pads off the disc , so they devised the pull-off pin system. IIRC the calipers on the D-type had 6 pistons, and because it could take a whole DAY to change the pads, they put a lot of effort into pads that would not need changing.
 
It's not that they didn't realize seal pull off was a thing, they just though the mechanical ratchet thing was better. I wouldn't be surprised to find patents played a part. The same thing can be said about the Girling rear caliper, the improvement they were chasing there was service & E brake in a single mechanism. It worked, but however interesting the design in hindsight it's Rube Goldberg engineering. Modern designs use exactly the same principal, but incorporate it all coaxially into the caliper's hydraulic piston.

Yours
Vern
 
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