Girling AR Calipers - help required

[Frogelan]

I'm still looking for some Girling AR calipers for sale for my Elan S1.5 GTS project. Obviously in Britain, Kelvedon / TTR / Paul Matty etc. stock these as new parts, but I am trying to keep to being as historically correct as I can.

I have found a set of Girling Aluminium calipers with the casting reference "64320805" ...

Are these the period and FIA correct calipers ?

They look very similar to a set sold recently (see link - apologies in advance to the Editor if I'm not allowed to do this):

https://racecarsdirect.com/Advert/Detai ... r-calipers

Obviously these do not have the external pipework that the "modern" AR calipers have, but I have seen similar ones on a 26R (I have also e-mailed the owned).

[bill308]

Hi Frogelan,

I believe all the early AR/BR calipers used an external cross over pipe. Some new ones do away with the external pipe and use internal passages.

Bill

[Frogelan]

Bill

Isn't it the other way round ?

(having seen a Belgian 26R with "early" calipers this had internal pipes...)

Thanks for your interest.

[Davidb]

Somebody was selling a set of 'modern' AR calipers recently because they had the internal piping and failed FIA scrutiny as a result. Original AR calipers had external pipe.

[Frogelan]

Thanks David. The whole subject is not very clear...

[Mazzini]

I had a 26R S2 in the 80's, it was a very original car, it had externally piped AR's.

Years later I was warned off buying some externally piped AR's (also off a 26R) because with use the caliper bodies were so worn that they flexed with under braking.

[Frogelan]

I have had a look at the FIA papers which show the (vulnerable) external pipe.

I have seen 3 sets for sale with the internal pipe with numbers corresponding to 64320805 or 64321080...but the vendors are not 100% sure that these are the right ones for an Elan.

What we do know is:

- the mid-point of the bolting is 3.5" but it is difficult to second guess whether they are somehow offset...
- they were made in aluminium by Girling and the trade ref was I believe the AR2 caliper...
- the photo on the FIA papers suggests that the external pipe is obligatory

[Mike Ostrov]

All Climax Elites from 1958 to part of 1963 ( end of production) were fitted with Girling AR externally piped calipers. or ordered as an option.

If you are curious, these calipers will flex. The flex is even visible. I have fitted the MK II internally AR calipers and they, too flex. Just place a dial indicator on one and hit the brake pedal, hard.

Our MC is .70 bore. Have forgotten the pedal ratio. I have inserted a glycerin filled gauge to measure line pressure and depending on your gorilla leg, 900 to 1300 psi is easily attainable.

Must confess no measurable benefit to my Super 95 vintage race Elite with AR's, even with brake pads with a .45 to .50 co efficient of friction.

They certainly do look nice!

Still have two sets of the Mk II AR's on my Elite/Elans, as both gained a bit of poundage to 1870 or so, compared to the usual 1525/35 pounds of factory weight for a standard Climax Elite. The TC is a monster, compared to the Lady Climax and the C-4 automatic is really huge.

Hope these comments/experiences are useful. Cheers. Mike.

[SJ Lambert]

Triumph Spitfire calipers are said to not suffer from the AR flex problems. The quick open wheeler guys have to file the pads in their AR calipers square due to the amount of flex they suffer.

[nmauduit]

- the photo on the FIA papers suggests that the external pipe is obligatory

does it really? the period photo I've seen on the site does not show the caliper, and the color photo appears to be a recent one... short of an official statement, it could just mean that alloy calipers of the shape nd material of the Girling AR are accepted (with or without external pipe)

[Frogelan]

Nicolas - this subject is very unclear although I'm sure the interested retailers have their views!

The FIA limited the definition to "AR" calipers with that recent photo on the website which shows a "recently restored" Elan which shows the external pipes. The 26R manual is not clearer (no part number than I could see).

The "AR" also exists in several sizes and versions (AR 2, 3, 4...) and with internal and external pipes.

In period, the FIA were more interested in swept area and piston size.

I would prefer to have calipers that appear to be period (most of the internal pipe versions seem to be very authentic looking through my rose-tinted specs) rather than the "modern looking" outside pipe repro "Girling" ARs.

I was interested in Mike Ostrov's comments on flexing but mystified by his pressure calculations which imply a 10:1 brake pedal ratio (which I would have imagined to be closer to 5 or 6.

[nmauduit]

I was interested in Mike Ostrov's comments on flexing but mystified by his pressure calculations which imply a 10:1 brake pedal ratio (which I would have imagined to be closer to 5 or 6.

eyeballing the pedal ratio to 5 gives the following order of magnitude

0.70" >> ~2.5cm2 MC piston
50kg foot pressure * 5 / 2.5 = 100 bar *14.7 = 1470 PSI

as for the Girling AR flex, racers have been using them for a long time now, so I imagine they must be good enough - though I'm interested in finding out where to grind the pads to insure proper operation under load...

[Elan45]

With regards to the flex of the AR calipers, I have never noticed any problems with flex although I am sure there must be some, on my Lotus Eleven or 20/22 FJr. But in the larger alloy calipers, the BR or CR, these have a steel reinforcement added to the alloy body. Of course this does add weight and the pads are even larger than the AR. And the pair of these larger calipers; I don't know which (BR or CR) that I have, but they also have the external cross-over pipes.

Roger

[Mike Ostrov]

Taking life and limb, I measured the brake pedals on my Elites (all are identical) and with a new wound on my head, the pedal ratio is 4.15.. Remember I was upside down doing this intricate measurement!

If you are really curious, I could measure the AR Girling MK II, caliper flex, next time I have a wheel off.

Since I make and bend all my hard lines from stainless steel tubing with 37 degree single flaring (double flares are not necessary and almost impossible with stainless) to match the AN -3 Aeroguip lines I also fabricate.

I have a bit of experience with brake, lines and fittings. I do pressure test to +2000 psi each flex line and final caliper fittings in a bucket of distilled water.

There are no banjo fittings on my calipers or oil or fuel lines. They simply do not like me. 3/8 x 24 AN bulkhead fittings into the calipers are perfect for the connection to the flex lines of which we have only one at the rear to the inboard diff and brakes and the standard two at the front..

Not sure about the Elan brake pedal ratio.. You can see a gorilla leg application will develop significant pressure on the brake pedal box and surrounding glass fibre support. I re enforce the Elite three sided pedal box with additional laminates of cloth, using epoxy resin. Easy when the 310 pound body shell is on a rotary.

Ok, breakfast with some glazed jelly donuts and Tony the Tiger Frosted Flakes. Cheers. Mike.

[Frogelan]

Thank you Mike for the info pedal ratios and the Californian diet (I'm a black coffee + m?sli / unpasteurised yogurt / bio fruit fellow).

I'm going to have a go at making my own LHD pedal box and will no doubt enroll a local, unsuspecting forum member to help!