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bacardincoke

Understanding Brake Force Regulator Parameters...

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bacardincoke

Have recently discovered my car had one of each of the 2x types of fixed ratio brake force regulators that are fitted to GTI's.

 

The parameters for the later 'E' type (4861.49) are given by Ate as 2/20, while the earlier 'F' type (4861.45) is 3/15... the first ones are what should be fitted to my post chassis number 1831921, 1989 car.

 

I'd looked into load sensing regulators quite a few years ago, specifically as fitted to VW MK1/2 Golfs and there's a simple formula you can use to work out a front / rear bias in understandable percentage terms.

 

Same formula unfortunately doesn't appear to apply to the fixed ratio variety (getting nonsensical results)... anyone aware of how it's calculated on these?

 

Purely me being interested in the extent to which my having a mix of parameters on the rear brakes may have been affecting things.

Edited by bacardincoke

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welshpug

the inline type used by peugeot (and ferrari, one part number directly crosses to a Ferrari of the same era)    are a rising rate restrictor which has an upper limit, the 15 and 20 are in Bar,  i.e   that is the max pressure the rear brakes will recieve.

 

the 309 also used the same type,  as well as the Zx,   the 16v in particular used 25 bar versions.

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bacardincoke

Ahh, so the latter numbers relate to actual bar, rather than used to calculate a percentage... makes sense put like that.

 

Leaves the first number just, the 2 of 2/20 and 3 of 3/15, we were speculating it might be to do with a measurable point at which the max bar (20 or 15 in these cases) is reached?

 

For example, to use a hypothetical comparison of a 2/20 regulator versus a 4/20 regulator - they would both ultimately rise to the same max. of 20 bar, but the point at which the 2/20 reaches there is twice as earlier than the other?

 

Problem was we didn't know how that difference was calculated, was it say a scale of 1 to 10 for example, 10 being the least aggressive?

 

 

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bacardincoke

@SRDT Found an old post you made here https://www.205gtidrivers.com/forums/topic/174580-315-rear-proportioning-valve-help/

 

The measurements you quote -

 

25 front --> 25 +/- 2.5 rear

40 front --> 29.5 +/- 2 rear

60 front --> 35.5 +/- 1.75 rear

 

Do you know what the parameters of the regulator those refer to are, for example 3/25?

 

I've trawled the Ate catalogues and while there is one to that spec. it was on a Ford Mondeo estate... however that's meaningless, as I suspect the reason others aren't listed (by Ate) isn't because they didn't exist, it's just that they didn't make them, someone else did.

 

Ironically it was finding that Lotus document that lead me back to this forum, if I've understood it correctly it's looking like I was interpreting things in reverse and it makes more sense now!

 

Knowing what the unknown parameter is may help confirm I'm on the right track or not.

 

 

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SRDT

It is likely the early unmarked regulator with a curve slope of 0.3 that is also used on some non GTI 309.

Looking at the curve it should be labelled as a 3/25 but I can only find it as 0.3.

854233521_Compensateur3-25.png.b87139486ed737b5c296725206dbc335.png

 

I only have partial and half reliable information about other regulators but for what I can deduct the "F" one could be a 3/15.

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bacardincoke

That's great, thanks... I was speculating (hoping!) it might be 3/25, which would fit in with what I think may be how this type of regulator is marked/rated.

 

(You're right that the 'F' regulator is 3/15, Ate give that against it in their catalogue.)

 

Getting back to my initial post - how to work out the differences between the 3/15 and 2/20 regulators.

 

All subject to confirmation, my maths being correct, dodgy terminology, it being almost midnight here etc., etc. (so don't be surprised if I row back on some of this later on!)

 

3/15

 

The 3 (x10) denotes 30% percentage (used to calculate the force to the rear.) 

 

The 15 is the BAR at which the regulator begins to take effect. 

 

Up to 15 BAR there is no reduction, front and rear are equal.

 

Thereafter for every 1 BAR rise to the front, there is just a 0.3 BAR rise to the rear.

 

That 0.3 BAR rise is in addition to the already present 15 BAR.

 

SRDT's chart uses three points of reference... the BAR at which the regulator begins to take effect (15 BAR in this case) then 40 BAR and finally 60 BAR.

 

Using the same system, the below is the map for the 3/15 regulator -

 

 

Front 15 BAR    Rear 15 BAR

 

Front 40 BAR    Rear 22.5 BAR  

 

Front 60 BAR    Rear 28.5 BAR

 

 

2/20

 

The 2 (x10) denotes 20% percentage

 

The 20 is the BAR at which the regulator begins to take effect.

 

Thereafter for every 1 BAR rise to the front, there is just a 0.2 BAR rise to the rear.

 

 

Front 20 BAR    Rear 20 BAR

 

Front 40 BAR    Rear 24.0 BAR  

 

Front 60 BAR    Rear 28.0 BAR

 

 

In bald figures doesn't look to be much variance, just 0.5 to 1.5 BAR at the Front 40 and 60 BAR points, but I'm not knowledgable enough to say whether such differences between the left and right rear brakes is significant or not? 

 

What maximum BAR could potentially be seen at the front brakes, does the chart finish at 60 BAR for a reason? 

 

 

 

 

 

 

 

 

 

 

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Tom Fenton

All the theory is great, but to establish if you can measure a difference in brake performance, the roller brake tester at a MOT station would be the way to test the car. 

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bacardincoke

Baptiste, may be something in the fact each 1 x BAR increment with the 3/25 regulator equates to 0.3 BAR and what the author of your chart uses as a measure?

 

Where ever you're seeing that info's a great resource by the way.

 

Is the 'Blank' 309 regulator (or any others that interest you) difficult to come by?

 

Potential scope to get them from non-Peugeot vehicles, possibly as equally scarce but you never know and at the very least could broaden the net  for you.

 

For example, Ate list those on the Ford Mondeo MK1 16v 1.6 and 1.8 Kombi's (1/93 - 12/95) as being in-line 3/25.

 

The 1.6's version (03.6043-1773.3) appears to be M10 fitment, but the 1.8 version (03.6043-1783.3) mentions M12 also, would need checking, but potential to be a straight fit / no adapter needed?

 

 

 

 

 

 

 

 

 

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SRDT

On yet another book I managed to find the exact same kind of curve for a 3/15 regulator but again just labelled as a 0.30 curve slope.

As expected the values are:

15 front --> 15 +/- 2 rear

40 front --> 22.5 +/- 2 rear

60 front --> 28.5 +/- 1.5 rear

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bacardincoke

Thanks for that... that confirms it then, how these regulators are rated.

 

Your book gives a +/- tolerance of between 1.5 and 2 BAR, depending on the reference point being checked.

 

That allowable fluctuation could potentially make a 3/15 regulator, in some circumstances, match a 2/20.

 

Peugeot presumably changed the regulators spec. for a reason, but that'd suggest there's not much difference between them regardless... the main one is the earlier 'F' kicks in 5 BAR sooner than the later 'E,  which may be less desirable.

 

Anyhow, thanks again for taking the time / input, you've helped me to find out what I was wanting to know!

 

   

 

 

 

 

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SRDT

They also confirm that you can replace older regulators by the new kind but only if you change both.

Looking at the tolerances two regulators of the same kind will mesure at most 5 bar apart. On the other hand a 3/25 and a 3/15 can mesure up to 14.5 bar apart and still be within spec.

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bacardincoke

Useful to know... from what I have seen when looking into this is new earlier 'F' regulators seems to be consistently a bit more expensive than the later 'E' versions, and that includes those sold by the same maker.

 

Granted not much in it, but worth being aware of if cost is a consideration.

 

Likewise, it seems the 'F' regulator is a visually solid item whereas the 'E' has a single groove around its circumference about a 1/3 of the way along from the M12 end.

 

Possibly to help identify one regulator from the other when they've been in place for a while and any markings aren't visible?

 

 

 

 

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SRDT

One more thing to note about testing is that you can mesure 15 bar front and 17 bar rear but in reality that's not possible. The front gauge must be reading low and the rear one high.

Doing multiple tests and switching gauges could get you closer to the truth but the test itself is mostly to check that each regulator isn't out of whack and that they are both of the same kind.

You are also likely to only test the pressures to see what's wrong after a failed roller brake test at MOT.

 

The groove could also be used to better secure the regulator on a bracket.

Compensateur.thumb.jpg.57cac9783c31cce1fe191ad7f729932d.jpg

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bacardincoke

It's amazing how they designed a cheap / reliable / accurate mechanical means to regulate the pressures, very impressive.

 

 

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