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Looking for anyone who installed the PNM rear brake callipers for Esprit S1 - Suspension/Brakes/Wheels/Hubs/Steering/Geo - The Lotus Forums #ForTheOwners Jump to content


Looking for anyone who installed the PNM rear brake callipers for Esprit S1


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  • Gold FFM

Hi, I hope that all is well with you.

I have replaced the original rear Girling callipers that were not performing well and had a faulty handbrake mechanism (They had been rebuilt previously by SJSportscars and I have since been told that the parts to rebuild are unavailable)....anyway I have recently bought a set of the PNM rear callipers and had them installed on the car.  Not necessarily linked, but during the installation process something happened that means none of the brakes work (!)

The point of my message is to ask if you or anyone you know in the community has installed the PNM callipers, what was thought of them and how did they perform.  The main guy at PNM has been helpful and supportive so I don't want to cause him any offence but....... More than two professionals/enthusiasts have told me I have made a massive mistake.... I am not sure what it is that I have done?! Can you enlighten me 🙂

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  • Gold FFM

Need more detail!  What is it that happened during installation, and what exactly is the nature of the failure? Please explain how the hydraulic system was bled after installation.  In pic 2, is that banjo connection tight?

British Fart to Florida, Nude to New York, Dunce to Denmark, Numpty to Newfoundland.  And Shitfaced Silly Sod to Sweden.

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  • Gold FFM
1 hour ago, Sparky said:

Need more detail!  What is it that happened during installation, and what exactly is the nature of the failure? Please explain how the hydraulic system was bled after installation.  In pic 2, is that banjo connection tight?

Apologies I wasn’t clear…

I am not entirely sure what happened during installation that affected the brake system as the car is with an engineer. The engineer doesn’t know either and it’s been in 8 weeks!

After installation the brake pedal felt hard when pressed until the car moved, then it went to the floor with no brake power.

The system has been bled by the engineer multiple times, the servo and master cylinder have been replaced with larger units (LotusBits) from an S3 Turbo, the Wilwood 4 pots on the front have been checked, a second set of PNM rear callipers have been installed, discs changed all round and the bias valve was removed and replaced… no change… no brakes 🤯

I believe the engineer will try adjusting the brake rod from the pedal to the servo to see if that affects the performance for the better. I’ll get him to check all of the connectors!

Its beyond my mechanical knowledge… it’s just stressing me!

My secondary concern is that I have been told via the engineer and consulting professionals that I should not have bought the PNM rear brake callipers;  I wanted to hear from those who have them to try and understand why not… I am hoping that the reason is not “because they aren’t original equipment”.

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I run the same setup with wilwood (front) and PNM (rear) on my turbo. It works perfectly. Huge performance upgrade vs original. I think we need more details here. Does the pedal fall through, chances are you have a leak somewhere. This is visible and can be traced. If the pedal goes hard without braking performance, chances are you have a vacuum or booster leak. The vacuum is pulled in your booster through the engine. The booster (aka servo) provides approx 80% of your brake power. No vacuum or a booster leak will feel like ‘no brakes’.

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  • Gold FFM

Trying not to do the engineer a disservice but I fail to see how a simple hydraulic system can be an issue for several weeks.  It's a very basic process, and any issue should be easily diagnosed in very little time.  And I have no idea why anyone would suggest the PNM kit might be the reason behind this.

If you're seeing no leaks, then I'd have to say the fault lies at master/servo.  Point of interest:  I replaced a DeLorean master last week with a brand new unit and spent ages trying and failing to get a pedal.  Turned out the new master was faulty.  Replaced, bled, perfect.

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British Fart to Florida, Nude to New York, Dunce to Denmark, Numpty to Newfoundland.  And Shitfaced Silly Sod to Sweden.

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I would honestly get a 2nd opinion on your engineer.   Brakes are incredibly simple.   I dont believe there is any condition possible (other than air in the system)  where the VAG rear calipers could cause there to be no brakes.  The only checks I would perform is that the piston size is compatible and the bleed nipples ar uppermost....

EDIT - Crossed with Gary's post, but pretty much says the same thing...

 

 

 

Edited by 910Esprit
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  • Gold FFM

Thank you Sparky, Gis and 910Esprit for your comments and advice. A plan is now forming!

Coincidently, today I have had a chat with a Lotus Forum member that was invited by my engineer last Friday to look over my car and give him an opinion. I am somewhat enlightened by the truth of that meeting.

So; the shoddy S3 Servo and mystery master cylinder (that I was billed £480 for on 15th June 2021 by Lotus Bits - who dealt direct with my engineer) currently fitted to the car will be removed by me (forcibly if necessary) on Saturday, when I go to meet my engineer, and returned to LB.

I will then reinstall the S2 servo previously fitted (Supplied by Lotus Bits in August 2020 for £258 - I assume the original servo was exchanged?! again dealt direct with my engineer) which doesn't leak, and purchase a functioning and suitably compatible master cylinder from the LF member.

The rod from the brake pedal to the servo will be adjusted (to full lock and then wound back - no one seems to know the correct adjustment) and then the brakes tested.

If they work, I'll take the car to an MOT station to check the front and rear braking pressures. I understand it should be about 40-60 in favour of the rear (?)

I will ensure that I collect up all the parts that were removed from my car and anything else I have paid for and drive to the sunset (or most probably walk).

I hope to be able to drive the car at some point this year!

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  • Gold FFM

Sounds like a plan; good luck!  If it's of any use, at any time, I'm only a few miles away in Watford.

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British Fart to Florida, Nude to New York, Dunce to Denmark, Numpty to Newfoundland.  And Shitfaced Silly Sod to Sweden.

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  • Gold FFM
7 hours ago, Sparky said:

Sounds like a plan; good luck!  If it's of any use, at any time, I'm only a few miles away in Watford.

Thanks Sparky, that is great to know. 🙂👍

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8 hours ago, grayp77 said:

The rod from the brake pedal to the servo will be adjusted (to full lock and then wound back - no one seems to know the correct adjustment) and then the brakes tested

Good that you have some progress here Paul. The rod adjustment is guided by the brake pedal position. You want it to be in line with the other pedals. You’re lucky that you have Gary close by. When I started out with my TE some years ago I contemplated flying him to Singapore a few times 😂

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  • Gold FFM

Best, then, that I don't tell you the airfare would have been around £200.  😂

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British Fart to Florida, Nude to New York, Dunce to Denmark, Numpty to Newfoundland.  And Shitfaced Silly Sod to Sweden.

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I fitted these to a friends S2. After a little modification to where the calliper was fouling on the mounting brackets, not allowing it to 'float' all was well. Read the thread here with pics:

 

 

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Pete '79 S2

LEW Miss September 2009

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Regarding line pressures, given equal bore sizes in both ends of the M/C one will see equal pressures for both front and rear circuits. Where braking balance is concerned, a differential is created when calipers of differing bore sizes fore/aft result in differing clamping force for a given line pressure. Further biasing on Esprit is created via differing rotor and tyre diameters, fore/aft.

Cheers

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  • Gold FFM

Whoops.  I'm disappointed in myself.  In my defense, I was knee-deep in a gearbox.

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British Fart to Florida, Nude to New York, Dunce to Denmark, Numpty to Newfoundland.  And Shitfaced Silly Sod to Sweden.

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