Mk 7 rebuild begins

[Hal Mercier]

I'm finally starting to do a refurb on the 1975 road registered Mk 7.

It's not turned a wheel since the turn of the century/millennium, so I wasn't surprised when the calipers turned out to be seized. I can't shift the pistons using compressed air, so anticipate ruined bores and pistons.

These are Girling 2 piston units, and I'd like to know what cars were fitted with these?

The mounting holes are centred 82mm apart and the discs on the car are 262mm cross drilled and of unknown origin.





Anyone?

[Hal Mercier]

Looks like Girling type 14LF as used on the Triumph Spitfire. You can get them from Demontweeks for £150 per corner, or from Rimmer Bros for less than half that new, or £40 apiece exchange rebuilt. Their rebuilt ones are marginally more expensive than the new ones but almost certainly use stainless-steel pistons and are also better protected.

http://www.rimmerbros.co.uk/Item--i-GRID005768

Only problem on a lightweight car is the weight, at 3.195 kg.

I got some alloy period Girling 2 pots from Tim Duffee in 2001 and they only weigh 1.265 kg.
Unsprung weight is important for good handling....

The alloy units, though a larger bolt spacing, are more compact....

[Hal Mercier]

Discovered some interesting things which had puzzled me back in 2001 when we built the Mk 4 for the '02 race season.

I was going to use a set of Revolution wheels with Avon slicks, hand-cut,which had been on the Mk 7, but when I tried to fit the wheels on the Mk 4 they wouldn't go on over the calipers, though they are 13" wheels.

I had to 'modify' the alloy calipers to get the Superlite wheels on that I'd bought in desperation....

I was surprised to see today that the alloy calipers are a fair bit more compact. Didn't make sense, till I finally realised what the difference was.....it's because the iron cylinders can be made a lot thinner around the pistons, and this is critical on the inner side of the caliper where it gets very close to the bell of the disc.

To allow for this stand-off space, the outer face of the caliper is a fair bit further from the bell than the iron ones are. Enough to foul the Revolutions. So although they are smaller and lighter the alloy units aren't as snug a fit to the disc bells as the Spitfire Girling 14 units.



Critical dimension....bell to outer edge of caliper.



Anyone know a good caliper to use on the rear, with handbrake actuation?

I had a look at the rear calipers to see what they are, and surprisingly, they are identical.....which means there's no handbrake!

I suppose when the rear discs were fitted it was only used as a competition car, or the owner had a very good relationship with his MOT tester!

The handbrake cables are attached by clevis pins to the rear trailing arms!

Rimmer Bros are the best I've found for the Girling (iron) calipers, and their own brand drilled and grooved discs are a very good price.

https://farm8.staticflickr.com/7574/152 ... c987_b.jpg

I've heard of Fiesta units being used.....on the front I think, Anyone have pix?

[cheeser]

Hi Hal,
Suggest you look at this original Davrian brochure http://john.rawlins.com/ndr3/downloads/Disc_Brake.pdf , gives details of the Davrian hand brake arrangement and also shows your alloy calipers for competition use. I have the 'drum ' handbrake set up on my car and although not as good as some disc hand brake setups, can be made to work ok.I'm sure others will give you details of their disc hand brake arrangements soon.

[Hal Mercier]

Thanks, Cheeser.

So the alloy calipers are either Girling D14R or AR 111. I'd forgotten they have no dust seals and a really race only.
The Mk 4 has a hydraulic handbrake system and uses the same alloy calipers on the rear.

I think I'll make up some new sets of mounting brackets and keep the alloy system for racing as they aren't suitable for road use.

This means I'll either need a hydraulic handbrake system on the Mk 7, or I'll need to use the original Davrian rear brake system, I wonder if Tim Duffee still sells them?

The units fitted on Dave Cooper's car would be spot on, I already have similar bracketry welded on the Mk 7...but what exactly are they?

[Nugget]

I did a bit of research into options (and ended up sticking with drums, but that's a whole different subject).

Popular conversions at the moment use Fiesta discs and either KA or Fiesta calipers, Imp Club comp sec has produced and is selling kits for around £175 iirc that comprise discs (machined), brackets, bolts and hoses, just source some calipers, given the price of the heavy Girling items they could be a cost neutral and lighter alternative. As for rear calipers that have an effective handbrake mechanism I spoke with Tim Duffee regarding this he mentioned using Sierra items, not sure which model they are from.

[Hal Mercier]

Nugget, I saw that....stainless mounting brackets and bolts, Fiesta discs, source your own Fiesta calipers, but what I'd like to know is are the calipers pig-iron and what do they weigh?

I'd like to develop a kit with alloy 2 or 3 piston front units, alloy handbrake rears, this should allow a reduction in unsprung weight of probably 8 kg over the old Girling 14 Spitfire iron calipers, which can't be used on the rear anyway, unless you have a hydraulic handbrake like on my Mk 4.

I'm investigating alloy handbrake rears using the Gold Mk3 unit, made by Girling, this is a one pot design also used on some Audi, Passat, Leon, Bora etc. Not sure, but it may be Girling 38....in any case it's alloy.

I understand they won't fit using the Golf 3 carriers, you need the slimmer Golf 2 carrier for use under 13"wheels and the fins on the caliper may need relieving somewhat, depending on the wheel design.

If dimensionally correct I'd use the Rimmer Bros own brand drilled & grooved discs for Spitfire, which will need re-drilling to fit Imp hubs.

I can get special mounting brackets made up here, I have a friend who cuts the jet support brackets for Airbus so I think his waterjet can cope with Imp brake supports ;~)

Here are the Golf 3 or 4 type calipers...don't get Mk 2 units as they have a bad reputation for sticking....they were redesigned for Mk 3 for this reason.

http://www.ebay.fr/itm/BRAKE-CALIPERS-P ... 5b07e96d41

only thing is you need the Golf 2 type sliders as the Mk 3 slider is too fat for 13" wheels.

Here are the sliders.....rather expensive as shown here but it's a good photo.

http://www.ebay.fr/itm/Volkswagen-Golf- ... 3f2cb5db0e.

[Hal Mercier]

I'm currently discussing with Tim Duffee how I'm supposed to fit any FIA approved roll bar arrangement on this car.

It has a Ferrari Dino type rear window which seems to block fitting a normal rollbar with diagonal to the rear brace leg at its lower point. Were there two types of rear window treatment on the Mk 7?

I think my cars body may have been intended for the Mini engined variant....