Suspect repro Girling type 16 callipers?

[Nick Jones]

I've moaned a bit about this before, but the story goes on.

When we upgraded the Spitfire brakes we didn't have any type 16 calipers to rebuild, so I bought some brand new ones.  Actual retailer probably irrelevant as I think they all come from the same place.

They looked good but the first problem was that we apparently couldn't bleed the system fully and just couldn't get a decent pedal - almost to the floor whatever we did.  Wasted loads of brake fluid.  Turned out not to be a bleeding problem but the caliper pistons over-returning.  Got around this by taking the pads out and pumping the pistons out, then pushing them back just enough to squeeze the pads and anti-rattle shims in.  Instant pedal.

Trouble is, the problem returns every 1000 miles or so (depends how fussy you are about pedal travel) as the calipers basically don't self adjust, so we have to remove the wheels, whip the anti-rattle shims out, pump the pistons out and refit the the shims.  We've stuck with it hoping they'd settle but they haven't.

I know we are not the only ones to have this issue - a local friend has an identical problem and have seen at least 2 more references on the forums.

Problem seems to be that there is too much stiction between seals and pistons.  There is mean to be a degree of "seal-roll" before they slip in order to pull the pads back from the discs, but there is just too much.

I had a set of "proper" seals in stock so today we pulled them off and swapped the seals.  Caliper quality looked pretty good and there wasn't alot obviously wrong apart from some mild scuffing on the piston/bore

and a thin black line on the piston, presumably where the seal had been sitting.

Seals, dust covers and pistons all in apparently good condition as would be hoped after a little over 1 year / 5 k miles.

Measure old v. new seals which showed slight variations, with the new ones being a little narrower (~0.1mm) but about the same thickness.  Old also felt a bit squashier.

Having fitted the new seals (on both calipers) with plenty of red rubber grease and reassembled everything the problem is........ worse . 

2 - 3mm roll-back now.  Unusuable.....   Suspect that the dimensions of the seal grooves in the caliper bodies are incorrect.  Will have to try and measure tomorrow......

Repro parts.......

Anyone else had this issue and, if so, how did you get around it?

Nick

[thescrapman]

I fitted a set to a mates TR4 before a 10CR.

Exactly the same problem. Not yet r esolved 7 years later.

Just have to remember to give the pedal an initial quick press before braking.

He has been advised to keep the brake pedal pressed down for a few weeks to "reshape" the seals.

I wonder if the pistons are not a smooth as they look, so the seal and piston grip each out slightly,  Perhaps a few hours with some very fine wet and dry?

[dave.vitesse]

Sometimes not using the anti-squeal shims helps.

Dave 

[Colin Lindsay]

23 hours ago, thescrapman said:

 

I wonder if the pistons are not a smooth as they look, so the seal and piston grip each out slightly,  Perhaps a few hours with some very fine wet and dry?

I'd still blame the seal, it's cheaper than altering the pistons. If you're going to all this bother I'd get a second-hand set of calipers and rebuild them myself, so at least I'd know what to blame, or not, if they still didn't work.

Incidentally have you checked the other end ie the master cylinder? It could be that something isn't right at that end, so when the pedal is pressed you have pressure, but when it's released you have a vacuum that sucks the pistons back in again. I could be talking out of my hat but it's a thought....

[Nick Jones]

6 hours ago, Colin Lindsay said:

I'd still blame the seal, it's cheaper than altering the pistons. If you're going to all this bother I'd get a second-hand set of calipers and rebuild them myself, so at least I'd know what to blame, or not, if they still didn't work.

I was inclined to blame the seals too....... hence the swap attempt.  The seal kit just fitted was a TRW branded one, so as close to OE as possible without being actual NOS (which could be really quite old now). Parts quality looked good and measured well compared to two old sets I had. 

Forced to dismantle again, we had a lot of trouble getting the pistons out. I could squeeze the pistons in easily a few mm by hand and they'd spring back to the start position when released. Likewise, a few psi from a foot pump would move them a few mm out but not further. We could then apply up to 100 psi short term and have them return to the start point when pressure released! It was only when I left 100psi on there for 2 - 3 minutes that they slowly crept out.

we've done some comparing of the insides of these and an old OE calliper and also 5 different seal kits of various origins.

Conclusions are that the seal dimensions and quality vary considerably, but more significantly the seal groove in the calipers has a different internal profile and appears to be too shallow, resulting in too much compression of the seals. Our slightly ghetto (and hopefully temporary) fix is to re-use the old OE seals recovered from the OE M16 GT6 callipers I rebuilt recently. These are in perfect condition but have compressed slightly to conform to the angled profile in the bottom of the groove.

By taking care to fit them in the same direction as they were we've ended up with pistons that move more or less as they should, though possibly still a little tight.

Brakes now working better than ever, but remains to be seen how well they will self-adjust.

Interestingly enough, the seals removed from the new callipers seem well made (definitely better than some of the kits) and similar dimensionally to the new OE ones, but softer compound, which is presumably how they worked at all.

Want some OE Girling 16PB callipers to rebuild now!

Repro parts....  where's the spit-on-the-floor smiley?

 

On 8/19/2018 at 9:37 AM, dave.vitesse said:

Sometimes not using the anti-squeal shims helps.

Taking them out, standing on the pedal then squeezing them back in again does help, but only until the pads wear down again and you are back to square one.  We've done this 4 times in under 5k miles (fairly gentle miles at that) on these callipers hoping they'd settle.  They haven't........

Nick

[dave.vitesse]

Taking the anti-squeal shims out does remove some of the indirect feeling on the pedal. However, only up to a point and it does sound as if there are problems. 

 The rally people in the 1960's wouldn't used the shims as they tend to reduce the direct feel of the pedal.

Dave

[Pete Lewis]

Lockheed machined a relief to the piston edge, does the same antisqueal but maintains the feel , until  the piston rotated and the relief ends up opposite the leading edge amd the squeal is back.

The nasty plastic anti squeal  pads l are pretty intolerable  

The piston contact relief  given by the shim must always be facing the  leading edge of the pad in its normal direction of disc rotation

Pete

 

[Nick Jones]

Lockheed calipers...... hateful design with no proper dust/weather shields so doomed to rust, stick and die young.

Some pics

OE seal groove

 

Repro seal groove

Dodgy not-to-scale-or proportion sketch showing the differences.  Regret that I have no way of measuring properly........  Disc to the left as drawn.

Pistons appear to be a good match in terms of major diameter and surface finish (ground then chromed).  All the groove IMO.......  Wonder if someone transfered a detail groove/seal design from a sliding calliper - which needs twice as much retraction?

Anyone had any that worked as expected?

Nick

[Nick Jones]

I understand there has been some lively discussion about this on face-ache?

Haven't seen it though......

Nick

[Gully]

Resurrecting this thread...

Anyone found a solution yet, please? I'm getting bored with having to pull the pads out of mine, pump out the pistons and then push back to the point where I can just get the pads in to recover sensible pedal travel. I still have the original Girling Type 16P calipers in a box (albeit looking a bit scruffy after 2 years in the darkness) - is it worth getting a seal kit, or seal kit and new pistons, to re-build them? 

Thanks,

Gully

[NonMember]

I'd say it's worth a go rebuilding them. I did a pair (many years back) for my Spitfire and they seem to work fine, although for other reasons it's not had that much mileage.

[Nick Jones]

We are still having issues with ours, though less so with the "pre-stressed" seals.  We now have a pair of OE Girling calipers to rebuild with new pistons and seals and I'm confident the problem will be gone once they have been fitted.

As I said above, I'm fairly confident that the issue is with the shape of the seal groove - it's the only significant difference between OE and copy parts.  Needs taking up with the suppliers.

I did discuss the problem with the guy at Bigg Red when we ordered up the parts for the OE calipers.  Initially he appeared to be saying that they supplied the new units to a lot of the "usual suspects" and became defensive when I suggested they didn't perform properly.

Rebuild your originals...….  Another example of repro tat it seems.

Though is there anyone out there with new type 16 calipers that are actually working as they should?  I should think many have been sold?

Nick