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Full Version: Technical Question - Brake Proportioning Valve
Ford Owners Club - Ford Forums > Ford Models > Ford Mondeo Club
Sevenman
I drive a [url="http://farm3.staticflickr.com/2571/5722547665_36e1bb2a89_z.jpg"]Mk3 Mondeo TDCi[/url] (which is the best car I have owned), but I have a question on a Ford part fitted to a car from a different manufacturer that I am hoping someone can help with.

My second car is a[url="http://farm9.staticflickr.com/8305/7919662860_8c82223508_z.jpg"] TVR Tamora[/url] and this, like all the later TVRs, uses a Ford brake proportioning valve. This valve sits in the brake lines to the rear and reduces the hydraulic pressure to the rear brakes.

My TVR has some issues with brake bias - too much force is going to the rear brakes and they lock before the fronts when braking at the limit. I swapped the Ford valve for an [url="http://www.apracing.com/ProductImages/CP3550-14%20prop%20valve.jpg"]AP racing adjustable valve[/url] but still have some problems.

I am trying to find the specifications of Ford part number 7 117 274. the parts chap at my local Ford dealer was helpful and could find it on his system at £49.56 + VAT, but could not find any technical information. I need to know what fraction of hydraulic pressure it lets through, e.g. 0.4, so I can check it is within the adjustment range of the AP Valve.

I contacted Ford and got a response from the technical department which was not helpful - they wouldn't provide information because the car was not a Ford (but the part is, and that is what I asked about), and said to contact the manufacturer. Good luck to anybody who tries to contact TVR.

The TVR specialists don't have datasheets for the part - they just know the part number so they can get one if needed.

If anybody knows how I can get some technical information on Ford part 7 117 274 I would be most grateful and it will help to get my TVR braking as it should and avoid ending up in a ditch.
FOCA
Picture shows AP Racing brake bias valve for single circut system - is it a twin circut system

Does the car have ABS?

What are the condition of the rear discs and pads? the fronts?

Did you disconnect the Ford proportioning valve completely when you fitted the AP valve?

Is the car for track days etc or for the road?
Sevenman
Thanks for the reply, apologies that it has taken me some time to post again, I should find a way to get this site to notify me by e-mail.

The car does not have ABS

The car have twin circuits (front, back). The valve is positioned such that it affects the rear lines.

Disks all round look good. Rear pads are fairly new and specced to match the front pads. Front pads are a recommended compound for the car, with plenty of pad material, but are of unknown age / history - I am having these changed for new next week.

The Ford valve was removed and the AP valve fitted in its place.

The car is used for road and track days, although not much point going on track until the problem is fixed.

I have written to Ford Technical Services requesting information on th valve since the main customer service helpline (who then asked technical services) kept sending me information for questions other than the one I was asking.
FOCA
I was thinking about this, and it led me to consider the sort of setup a rally car or race car would have -

the solution may be to upgrade your braking system to a similar setup as found on a rally/ race car

You may be able to keep your existing discs/ calipers/ slave cylinders, (for now, anyway) -

and upgrade/ change your master cylinder to an adjustable twin racing- type one (you would probably remove the AP valve)

this may be expensive and/ or difficult,(you may have to change your pedal box, etc to a racing one) but may give you the results / range of adjustment you want/ are looking for

the car may have an underlying problem - eg weight distribution/ too light at the back? -

you could get track car prep engineers to get your corner weights done/ adjust your weight distribution, i don't know how they would do this - battery in the boot etc?

finally you could upgrade your fromt brakes to massive discs/ racing calipers, this would not be cheap and you would probably need to fit larger diameter wheels to fit over them, you could fit wider rins/ tyres while you are at it

Ok so altogether this would be a fair bit of money/ work/ hassle but this could turn your TVR the way it is now to an awesome track-day weapon :)
Sevenman
The master cyclinder changes might be overkill for this problem - the system should be fine as standard, so I just need to find what isn't workign.

I am hoping that ne front pads may be the cure, and that I will be able to somehow find out the spec. of the Ford proportioning valve that is fitted.

There is a fairly simple upgrade from 304mm to 322mm front disks (just needs caliper spacers) which would give greater front braking force, and apparently the 322 disks are cheaper than the 304. However either should eb able to cope on track as the car is only a little over 1000kg.

Corner weight measurement (not adjustment) is being done next week. We will see what the results are...
BOF
Hmm, this isn't really the correct set up for a race car (you don't say that this is what the car is, but effectively that's what you want for the track days, but may not be suitable/legal for road use, so it is just a discussion point).

For a race car, you wouldn't want a proportioning valve at all, but a brake bias bar that allowed you to manually alter the front:back balance. This would be ideal for track day use, but I'm unsure of how the MoT man would react if your car was modified in this way. I wouldn't be surprised if they reacted badly to the fact that you can adjust it wrong, but that's just because they seem to take the most negative interpretation of everything.

[quote name='Sevenman' timestamp='1351089356' post='213362']
I am trying to find the specifications of Ford part number 7 117 274. the parts chap at my local Ford dealer was helpful and could find it on his system at £49.56 + VAT, but could not find any technical information. I need to know what fraction of hydraulic pressure it lets through, e.g. 0.4, so I can check it is within the adjustment range of the AP Valve.

I contacted Ford and got a response from the technical department which was not helpful - they wouldn't provide information because the car was not a Ford (but the part is, and that is what I asked about), and said to contact the manufacturer. Good luck to anybody who tries to contact TVR.

The TVR specialists don't have datasheets for the part - they just know the part number so they can get one if needed.

If anybody knows how I can get some technical information on Ford part 7 117 274 I would be most grateful and it will help to get my TVR braking as it should and avoid ending up in a ditch.
[/quote]

I'm not surprised (disappointed, maybe, but not surprised) that Ford are unhelpful; the valve will be manufactured by a brake specialist (eg, Teves, ATE, Girling, etc, etc) and they might be a better source of information. Certainly TVR themselves won't be of much help at this stage. There might be an owners club who would help, though?

[quote name='Sevenman' timestamp='1351089356' post='213362']
I am trying to find the specifications of Ford part number 7 117 274. the parts chap at my local Ford dealer was helpful and could find it on his system at £49.56 + VAT, but could not find any technical information. I need to know what fraction of hydraulic pressure it lets through, e.g. 0.4, so I can check it is within the adjustment range of the AP Valve.

[/quote]

If I understand correctly, the Ford part will allow through pretty much all of the pressure up until the point that it starts limiting, at which point the pressure will rise no further. This is a very approximate way of stopping the rears from locking, and doesn't really work well in extreme conditions.
Sevenman
Thanks for the information.

I don't know much about bias bars. The idea behind the adjustable valve was that the standard valve would sit within its range of adjustability. However, it may be the case that the standard valve was fine, the fault lies elsewhere, and I have just made things expensive / complicated for myself...

Regards MOT testing - it has passed an MOT with the valve fitted (MOT station next door to the TVR specialist that fitted the valve), but I agree that it could be seen in a bad light by some testers - even though it is trying to fix a problem that doesn't seem to stop it passing MOTs (it had been recently MOTd when I first found the issue with the rears locking).

I may well go back to a new standard valve if I think i have sorted an underlying problem.

If I could find out who made the valve then I might be able to follow it further. The TVR specialist I am visiting next week may have some in stock so I can check the packing - but I think they just come in Ford boxes.


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