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brake and clutch cylinder cap corrosion


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Sorry for further thread drift 

 thought the whole idea of twin master cylinders is to have 2 brake circuits for safety. 
 

but what is the new arrangement ?

front and rear separated 

or 

front and rear pair on a diagonal?

doesn’t this mean re-plumbing the whole brake system ?

 

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I asked Tony Sheach about the plastic reservoir on brake master cylinder, shown in Alf's photo.  This is Tony's reply:

Yes Stuart's right - there was a LUCAS branded clear cap and also an unbranded clear cap that fitted over the embossed alloy cap to give the appearance of a clear cap (I wondered if this was some sort of paperwork dodge, as it didn’t appear to do much).

I came by a few sets of brake and clutch master cylinders with the add on cap, but have only had one set of the clear cap versions ever - on a TR4 that originated in Luxembourg, if I remember rightly.  It was fairly original, but i sold it about 10 years ago to a new owner in France, not far from where my old 4A  LDU753F now lives. I did some rolling restoration work on that car and added many original bits to it, replacing various new and incorrect bits.  It won’t ever win a concours, but it has to be one of the most original cars left.  Sold to fund purchase of 5VC !  So a good cause.

Ian Cornish

Additional note from Tony: clearly, originals are embossed Girling.

Edited by ianc
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The diagonal design is ridiculous, failure of one circuit would lead to complete loss of brake control.

The front/back could work, but front failure would lead to a spin and loss of control, as rear brakes that work my ore than front always do.   

Rear failure would be a stable mode, just less brake effect, but not much.

The TRUE purpose of dual brake masters is found when they are linked by a balance bar, and allow adjustable brake balance, front/back, but that is only required for competition purposes, and in the hands of an expert driver.  One more expert than me, I hasten to add!

As for plastic caps,. Masters with plastic reservoirs, either directly or remotely attached, and plastic caps are widely available and easily fitted.   Any 'performance' supplier (eg Demon Tweeks, Merlin) will have them.   No need to research obscure OE fitments.

John

Edited by john.r.davies
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The point of fitting the twin cylinder setup is to give dual line braking i.e. the same as a modern and you also have the facility to proportion the braking effort to cope with so called "upgrades" note Im not a fan of fitting big calipers on the front without also uprating the rear to maintain brake balance.

FWIW I think the Racetorations kit is much better quality and I have fitted them.

Stuart.

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13 hours ago, silverfox4 said:

Ian- yes the master cylinder is OE removed from the TR4A.  I hope I am not solely guilty for extending this thread as I was only complementing Chris' experience

Stuart - My TR4A  is a Malines assembled unit.  Is it possible that the plastic reservoir was a legal requirement for say France and Belgium? 

Unless the plastic reservoir can be replaced, I envisage difficulty in getting the master cylinder rebuilt to as new condition, although the cap does screw on very nicely and leak free. I have to try this OE plastic cap on the new TRW master cylinder 

Cheers,

Alf

As your car was a Malines built one then yes I suspect it was a market specific issue as Tony Sheach has stated possibly Luxembourg market specific requirement. All Malines built cars had a certain amount of whats known as local content to qualify for the tax status that went with CKD Cars.

Stuart.

Stuart.

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Hi there and please sorry me,

the resulting force on a bar, lever or piston ( by a push rod) is only the one in the 90 deg. angle to the lever (or piston surface).

First,

to make one push rod shorter or longer only reduces the play of the system.

And this happens automatically on callipers (disc brakes) and also on the rear with self adjusting brake shoes.

Second

you can adjust both sides of the bar to slightly different length and so make the leaver  shorter on one master and longer on the other.

With this the push rod is out of 90 deg. in a worse position and this is why it causes nothing.

To give more force on one master the only way in my opinion is to move the hole master sidewaeds closer to the pedal - or the pedal sidewards to the master.

And then get the push rods in a 90 deg. angles again by the adjustable bar.

The system on the market don't do that.

Safety may be a reason to fit this units, but a sudden, not expected and surprising fault of a single citcut system is very unlikely.

Ciao, Marco

 

 

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2 hours ago, stuart said:

The point of fitting the twin cylinder setup is to give dual line braking i.e. the same as a modern and you also have the facility to proportion the braking effort to cope with so called "upgrades" note Im not a fan of fitting big calipers on the front without also uprating the rear to maintain brake balance.

FWIW I think the Racetorations kit is much better quality and I have fitted them.

Stuart.

Sad to tell you, Stuart, but the physics of friction don't work like that!    Friction depends on the pressure between the two surfaces.   Increase the area ( bigger pistons or pads) and the pressure goes down per unit area.   But they have a greater area, that cancels out, and the friction stays the same as before! 

The only advantage of multiple pistons is that a longer, less wide pad can be fitted FURTHER from the axle.   So the same friction has a greater moment of leverage.

But to be effective that demands a wider disc and bigger wheels, with lower profile tyres.     "Performance" is NEVER just one factor, but many used in balance and together.

John

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Friction is indeed independent of surface area but an increase in area allows the use of a softer compound without excessive wear rates and a greater area to soak the heat so there are advantages. 
Braking is one of those areas which seem simple until we start looking a little more closely. 

Edited by Drewmotty
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50 minutes ago, john.r.davies said:

Sad to tell you, Stuart, but the physics of friction don't work like that!    Friction depends on the pressure between the two surfaces.   Increase the area ( bigger pistons or pads) and the pressure goes down per unit area.   But they have a greater area, that cancels out, and the friction stays the same as before! 

The only advantage of multiple pistons is that a longer, less wide pad can be fitted FURTHER from the axle.   So the same friction has a greater moment of leverage.

But to be effective that demands a wider disc and bigger wheels, with lower profile tyres.     "Performance" is NEVER just one factor, but many used in balance and together.

John

Yes I know that hence my comment of not liking so called upgrades!

Stuart.

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8 hours ago, Z320 said:

Hi Andy,

what is your hope about this modification?

I

Marco:

My main interest to to provide dual circuit for safety, plus the added reliability of using high quality master cylinders as opposed the reproduction Lucas units.

 

My apologies to the original poster for the thread jump down the dual circuit rabbit hole, but I highly value the learned opinions here.

Happy Boxing Day to all in the UK!

Andy

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2 hours ago, silverfox4 said:

Stuart - many thanks for that confirmation

John - Could you please provide a link for the replacement TR4A MC with plastic reservoir - nothing on Demon-Tweeks 

Cheers,

Alf

Certainly, Alf.   

https://www.demon-tweeks.com/uk/motorsport/braking/fluids-actuation/master-cylinders-reservoirs/.  Click on the Wildwood M/c listing to find the 0.75" you need, and below that for the remote reservoir.

John

10 hours ago, stuart said:

 

 

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10 hours ago, silverfox4 said:

John - eventually identified two plastic reservoirs that appear similar to the OE version, namely OBP and Girling.  Will investigate further.

Thanks,

Alf

Be aware they are remote reservoirs.

Stuart.

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Thanks Stuart - so it's back to square one then finding a cap that does seals firmly with no seepage. 

I vaguely recall that the TRW MC I got from TRShop back in June did have a plastic cap, but since I preferred the esthetics of the metal cap. I ordered one separately and fitted MC  that way.  Now for the life of me I cant find that plastic cap anywhere to try it - just hope that I did not bin it.

Cheers,

Alf

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On 12/23/2020 at 1:10 AM, silverfox4 said:

This is interesting.  I recently ordered the subject plastic caps based on this post and had a similar problem - the threads just did not want take. I tried several times and then pushed down hard on the cap while turning it and it seemed to catch and screw on - maybe I cross threaded it.  The garage was freaking cold so I gave up in disgust as either I have forgotten how to screw on a simple cap or the cap is wrong.  I won't know until I feel like challenging the cold to see what is going on.

For context regarding Girling vs Lucas,  I purchased this Lucas TRW brake MC for the 4A last June from the TRShop and at the time of order I chose to add the ali cap in place of the plastic  thinking it was more in keeping.  I found the ali cap kept weeping because of poor integrity of the threads, so when I saw this post I ordered the 64474602 plastic cap from Demon Tweeks with the experience as above.  In hindsight I should have stuck with the plastic cap that came with the MC

Neither cap makes reference to Girling or Lucas.  I look forward to any further insight from this post.

IMG_5753.JPG.91a0de08ee26c25ccd05f888a7f4c91f.JPGIMG_5754.JPG.25c0b03bcf705f66043af3cad1ecac71.JPG

 

Merry Christmas  all,

Alf

Hi Alf, where you mention the thread on the plastic cap "seemed to catch"  I think what happens is the plastic shroud inside the cap which is a similar diameter to the inside of the reservoir gets wedged in the reservoir if you push the cap down hard. That shroud is removable, it clips on and I remove the one on my new cap after which the cap fell over the reservoir threads spinning freely and not biting on the threads at all.     Chris

Happy New Year to All.

 

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Hi Chris, that probably explains it, however it's been -2c in the garage for the past week and I am out of propane for the heater, so have not ventured out - will confirm in a few weeks. (still searching for the plastic cap that may or may not have come with the TRW replacement)

Thanks for that,

Cheers,

Alf

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