anyone tried vw passat/audi a6 calipers on the rear of their pre 85 cars?

[naasaa]

I must agree on the cost of these Wilwood, as they are a bit pricy.

At front I have the PNM Wilwood 4 pot kit. which by itself is a great upgrade., but recognize that I could use more brake force at the rear.

When in my garage I will check the diameter of the original rear calipers. Not sure, but it seems as the Passat caliper piston diameters are 41mm.

I do have brake bias valve fitted, which I believe is beneficial to fin tune the brake bias. But should be second after proper dimension of rear/front brake force. Hence I am leaning toward a bigger caliper for the rear.

[peteyg]

16 hours ago, naasaa said:

Well, the piston diameter, area, is what makes the difference in brake force. 

A larger diameter will result in a higher clamping force. 

Fair point Lars. They do look very similar to the originals size-wise though.

Pete

[drdoom]

Lots of good points made, lads, and I should suggest that anyone considering re-work of the brake system be quite clear on what is desired/expected by the time it's all said and done. The BOE chaps whose site was linked in my prior post are the first I've encountered, after a great deal of research over a very long time, who make clear statements on braking as related to a Lotus. I recall a long journey of discovery when upgrading my classic Elan chassis performance in which it was made clear how much common wisdom is not so wise. It takes soundly effective measures to enhance the chassis characteristics of a Lotus in my experience, but it can be done. I was quite surprised to read the BOE views on OEM Elise/Exige braking, prior remarks notwithstanding, but they make their argument in plain terms. I suggest those insights, if correct, should be rather applicable to the Esprit as these are all cars of comparable masses, platform dimensions and weight distribution.

I'm no engineer and please do not mistake me for one with accredited expertise, rather I'm one who seeks knowledge through the joys of driving, tinkering and study. We must never fiddle with the machinery unless always vigilant of the critical consequences pertaining to safety. It's fairly safe to say that the VAG calipers appear to be a welcome and nicely suited replacement when simple substitution is desired. A more comprehensive program to upgrade brake performance should begin with identifying what parameters are in question. Do we like the pedal feel, for example? Is the braking limit adequately fierce, and if not for which reason? Is the front/rear balance optimal?

Happy to share thoughts on the merits of any components, as far as I may understand them.

[naasaa]

I meassured the pistons in the original calipers to app. Ø 36mm

If the WV caliper is 41mm the clamping force is then increased about 30%.

Not a bad upgrade in conjunction with front brake upgrade. And I do agree with Steve that this one should be cautios doing so.

When I did my front brakes I was working on mounting front calipers from a Citroen C5 at the back, but found it too troublesome. However, the need for rear brake upgrade was obvious. So I`m happy if these WV works well. But still curious to know the diameter of the piston!

[GTK]

5 hours ago, drdoom said:

... comprehensive program to upgrade brake performance should begin with identifying what parameters are in question. Do we like the pedal feel, for example? Is the braking limit adequately fierce, and if not for which reason? Is the front/rear balance optimal? ...

I might have said this already, getting deja vu; I had a really interesting conversation at the TLF Christmas party about Lotus brakes. Can't remember who it was, but they said that people often think the Esprit's brakes aren't up to much. Said that they were designed to be progressive and when compared to modern brakes can give you a fright, but that they're very effective and by design load up given suitable input.

to be honest I'll be very happy with the VW calipers if they have all the same characteristics as the Girling originals, but shave weight.

[drdoom]

George adds another good observation to the thread, that the Esprit brakes as delivered perform at a rather high level. I have been recently reminded of this by a mate who's owned his S1 since the early '80's and has plenty of on track and over the road experience from which to draw. We are collaborating in an effort to maximize the performance limits with the greatest attainable pedal feedback on our two Esprit. Too early in that effort to report results but we are exploring servo delete, dual master cylinders on balance bar, proportioning valve for the rear circuit, larger discs/calipers all around and, for good measure, some sort of electric e-brake. We have a substantial appetite for intellectual stimuli.

[910Esprit]

Couldn't agree more George.   Take with a pinch of salt anyone who says the pre-ABS brakes are inherently shit, and look at the contemporary performance (braking & fade) statistics which were excellent!.  I suspect poor current performance is more indicative of 30+ years of wear and tear or an ill tuned engine 

NB - most ebay listings include caliper statistics.  I assumed they have a 38mm piston?

[naasaa]

I do not agree that the Esprits brakes are delivered to perform at a rather high level, either I do not see how they should act progressive.

As far as I can see and experience the Esprit's brakes; they are a match of suitable parts off the shelf, non vented to sheed weight, and not up to the task for a sportscar in this league.

My old Corvette 68 or 70,ties Volvo 240 had better brake force and pedal feedback. Albeit much heavier. But I do agree that these modifications should be done wisely and not at least balanced. There are several upgrades for the front, but I do miss a matching upgrade for the rear. 

Any one who now what year these VW calibers are from? Seems as they are made with both 38 & 41mm bore?

[910Esprit]

Ha Ha -  two contrasting opinions.  Take your pick! 

[naasaa]

9 minutes ago, 910Esprit said:

Ha Ha -  two contrasting opinions.  Take your pick! 

😁 very different. I will not call the brakes shit; but rather average suitable for a standard car.

[silverfrost]

Lars,  

I do not think lotus had weight saving in mind when they used solid discs,  I would of thought that was all that was availible at the time as vented discs started to catch on they got fitted imo

[naasaa]

35 minutes ago, silverfrost said:

Lars,  

I do not think lotus had weight saving in mind when they used solid discs,  I would of thought that was all that was availible at the time as vented discs started to catch on they got fitted imo

My 68 corvette had vented disc's. Volvo's from the seventies as well.

[GTK]

I have no idea how the brakes perform, having only heard varying opinions. I do have a pile of the big name auto magazines from the late '70's [and more recent] with reviews of the S2.

I personally have the impression that like the rest of the car the brakes were great back then, but less impressive when compared to the performance levels cars achieve after 43 years of automotive development...

 

[naasaa]

George

Hard to argue against these articles. As mentioned before, I do not find the standard brakes shitty. But honestly, way for improvement. 

This articles compare the Esprit braking performance to similar sportscars these years.

🙄 not sure why the image is upright!

 

[lotus-62]

 I am a bit surprised that the pre'85 esprit rear brakes have just 36mm pistons at the back as my '85 has 45mm at the back, (and single pot 57mm at the front)  wondering what the pre'85  has at the front.  there are some french cars around that have the handbrake on the front caliper and have a bigger piston diameter (like the BX has an 50mm piston.  so maybe there is a better caliper around for the rear when upgrading the front. 

[drdoom]

Rick's rear calipers are a mystery to me, my rears measured about 36mm and are the factory originals. I believe the original non-Turbo front calipers had 48mm pistons. We know that by '85 the car had been fitted with Toyota sourced front brakes but the rears remained inboard as original and alternative piston sizes have not been listed anywhere until Rick's posting. Curious.

In summary of Esprit braking performance let's be clear - the Esprit has always performed at a high level. Mate's car was thoroughly rung out at 3 circuits out here in the West and never found wanting. Local track, Westwood, was 1.6 mile in length with peak speed near 120mph attained on a slight downward grade leading to the slowest point, a tight hairpin requiring practically all that energy be dissipated on each lap. The car was lovely throughout.

Our primary motivations arise out of desire for more direct pedal feel/ergonomics - hence the booster delete - concern for ongoing parts availability - see substitution of rotors/calipers for aftermarket. Once we've committed to going that deep then the further aspects to optimize simply follow rationally. Less rational is our taste for tinkering, as admitted, but what is life if not lived with a touch of madness? Others may well have good reason to pursue use of OEM or similar components, as originality and high baseline performance do make clear.  

[GTK]

Here's that comparison the right way up. Have to say the figures seem much more night and day than the reviews the Turbo Esprit got. But maybe there is journalistic bias in all of the articles, who knows. Def worth keeping in mind the Turbo Esprit is 200kg heavier than the earlier cars, that's going to make a noticeable difference. 

[drdoom]

One thing I have learned over my many years is to take everything written or said with one big grain of salt. Journalists work as much to entertain as they do anything else, and often not terribly well. Apologies to any who may be offended in this characterization. What has been put forth from Lotus themselves was not always particularly accurate, which is altogether what one should expect from a crafty lot working so competitively in delivering these rare treasures for road and track. I find it necessary to parse thoughtfully through even the most forthright writings on Lotus, Mr. Rudd's fine memoir for instance, as comments which are in themselves truthful still leave room for interpretation. Those who truly know are not necessarily compelled to reveal all, as knowledge is the stuff of Lotus fortunes ongoing. As for journalists and writers in general, well . . . . . .🤨  

[The Real Stig]

I have recently changed the rear calipers on my 2009 Lancia Delta = AR Giulia. The calipers look identical to the  VW-ones mentioned here. 

I guess they are very widely used in modern cars. I would also guess, they come in different piston sizes. 

Seek and ye shall find.

[lotus-62]

15 hours ago, drdoom said:

Rick's rear calipers are a mystery to me, my rears measured about 36mm and are the factory originals.

the pre 85's are Girling calipers and the later one's are bendix, same calipers as renault 25/21/espace but with a bigger piston (from the matra bagheera and alpine A310 if my information is correct) ) used on the early stevens esprit as well on the outboard.  

[drdoom]

8 hours ago, lotus-62 said:

the pre 85's are Girling calipers and the later one's are bendix, same calipers as renault 25/21/espace but with a bigger piston (from the matra bagheera and alpine A310 if my information is correct) ) used on the early stevens esprit as well on the outboard.  

Thanks for the correction Rick, I reviewed the Parts Manual and now see that there was a change to rear caliper late in the Citroen box equipped cars. Always open to new insights.

[Lotusfab]

Anyone of  you Chaps now got a spare rear left girling caliper? I just need the ratchet handbrake bit  which I can take out so it doesn't matter if the rest Is damaged. 1/2 is on the piston. Might be able to get out of a right one. I'll buy it from you of course. This type. Thanks.

[Paul Coleman]

On 19/08/2019 at 10:30, Lotusfab said:

Anyone of  you Chaps now got a spare rear left girling caliper? I just need the ratchet handbrake bit  which I can take out so it doesn't matter if the rest Is damaged. 1/2 is on the piston. Might be able to get out of a right one. I'll buy it from you of course. This type. Thanks.

SJ do a rear brake exchange

[Lotusfab]

Thanks Paul, tried them they only rebuild the ones you have and have no spares.

[82s3]

I read this post several times a while back, thought about it and decided to have a go, because my handbrake has always been a bit naff.

In case it did'nt work, I've initially bought just a nearside Audi A6 caliper (brand new & only £20 on eBay) which I've found you need to fit on the offside in order place the bleed nipple uppermost. There's a bit of a knack to getting the calliper in place because there isn't much space - the rear chassis loop that runs under the gearbox gets in the way. This loop also runs very close to the bleed nipple, so bleeding the rear brakes may be easier said than done.

Anyway I got the calliper in and then fiddled a new set of A6 brake pads into place and bolted it up, no problem and it slides without fouling the carrier.

The bracket on the calliper that retains the handbrake cable outer ferrule needs to opened up a little so that it will slide in. Once this has been done, the cable fits and works as normal. I opened it up with a conical grind stone in a drill.

Routing the nearside handbrake cable is up the side of the engine bay, past the coolant header tank and the down to the caliper. No problem.

Last job is the brake line. This is a different fitting at the calliper end - it needs a banjo. I'll call PNM tomorrow to see if they'll sell me a set.

Bob