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Rear brake pressure reducing valve - recommendations pleases for IVA


Wavey
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Some rather concerning information in this post about Hi Spec brake setups.

 

The only other 2 things that spring to mind would be plumbing a 60/40 tandem Mc the wrong way round (rears to the first port and fronts to the second) or the addition a Bias valve to alter the front to rear bias would help.

The latter suggestion would really be a solution for what could be a major design issue and obviously one that needs addressing as a matter of urgency.

 

With regards to the large bore Wf supplied Tandem Mc I got mine they first started supplying them, now about 5 years ago.

I'll have a look and see if I can find any ID on it. But WF should surely know if it is a 50/50 split or otherwise.

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Master cylinder is plumbed up correctly, port furthest from pedal to rears port closest to pedal to fronts, so 60 front :40 rear  in theory.     Here are some pictures of the front pads.  Judging by the rings of grease on back of pads they have 34.6 mm pistons x 4 up front, so pistons are correct.    As you can see there is a bit of bedding-in still to do on one of the pads, so it looks like the theory that the fronts bed-in slower than the rears may be sound.   I believe it is common to have uneven wear on the fronts so not stressing about that.

 

Went to do a bit more bedding in around the little island outside my house, 15 mph no skids, 5 mins later neighbour tells me he has called the police , no police yet but the access road is being resurfaced and it is still a private road till builder hands over to council, so perhaps they wont bother to come round, ho hum, he seemed such a nice chap, you just can't tell.

 

I assume I can pay a garage to drive it around on trade plate for an hour or two as my last option.  refuse to do the cheats.

piston_pad.JPG

front_pad1.JPG

front_pad2.JPG

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Thanks for advising on piston sizes. sorry to hear you've got a jobs worth neighbour!

 

Given the low speed your trying to bed in at, I'm not surprised you've not achieved it yet. Ferrodo for DS2500 pads,  suggest 10 stops from 70mph to 30mph in quick succession and then drive without using the brakes for 10 mins to cool them down.

 

I like the idea of asking the garage to bed them in with the trade plates. Though if you take a long enough route to the MOT test, you may achieve this yourself!

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I had similar issues with mine pre IVA , and several people on here told me the wd40 trick . I didn't like that idea so bedded them in as you have, before starting though I  also roughed up the disk, probably not necessary for you now. The discs from new have a protective coating that has to be removed, I used some emery cloth on mine to make sure it was all off, If this isn't removed I think the pads will glaze up, together with pad alignment until bedded in is all it is I reckon.

 

Good luck

 

 

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Called the police for driving at 15mph 😂 there's kids on bikes pulling skids on my street faster than 15mph :d😂

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Just to add to this,  I too recently had this as a fail on my iva,  even the testers are aware of Westfield's failing it a lot and wd40 being put on rear brake pads to get it through tests.  Doesn’t seem ideal to me either.  I’ve too changed my front pads it feels better but the rears still lock before the front.  Not easy to get them to bed in when you can’t drive it!

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I really would be getting together for a discussion with the factory and I don't mean to discuss the bodge procedure. Retests and buying new pads etc aren't cheap and if its a complete setup purchased from them it should be suitable for purpose and pass the test. 

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1 hour ago, TomW said:

Just to add to this,  I too recently had this as a fail on my iva,  even the testers are aware of Westfield's failing it a lot and wd40 being put on rear brake pads to get it through tests.  Doesn’t seem ideal to me either.  I’ve too changed my front pads it feels better but the rears still lock before the front.  Not easy to get them to bed in when you can’t drive it!

Sorry to hear you are having the same issues.  I have re-bled all four corners again and got some new pads for the rears ready for the test ( got them from HiSpec a lot cheaper than WF they also have them half moon cut out).  Westfield factory seem to be sticking to the mantra of take it on a trailer so rears don't bed in before fronts.    I suspect if you had the full size pads on the rear, rather than the reduced size due to the cut out, they would probably be ok, but because the pads are effectively smaller, there is more pressure per square cm and heat so of course they bed in fast.   My plan either change rear pads and hire transporter guy (if foul weather), or drive there and get local garage near test centre to fit my new pads to the rear, that way I can get another 30 miles bedding in on the front.

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30 minutes ago, Two7 said:

Sorry to hear you are having the same issues.  I have re-bled all four corners again and got some new pads for the rears ready for the test ( got them from HiSpec a lot cheaper than WF they also have them half moon cut out).  Westfield factory seem to be sticking to the mantra of take it on a trailer so rears don't bed in before fronts.    I suspect if you had the full size pads on the rear, rather than the reduced size due to the cut out, they would probably be ok, but because the pads are effectively smaller, there is more pressure per square cm and heat so of course they bed in fast.   My plan either change rear pads and hire transporter guy (if foul weather), or drive there and get local garage near test centre to fit my new pads to the rear, that way I can get another 30 miles bedding in on the front.

This has been similar to my plan,  I take it then your rear pads had been cut down,  I only checked my front pads and swapped them but they’d been cut. I changed mine to carbotech  xp8 pads which weren’t cheap but supposedly some of the best pads you can get and the problem remained.

 

@Two7 Maybe we should make a joint complaint to the factory as @Steve (sdh2903) suggested as since it’s the pair of us there’s something wrong somewhere and this could get very expensive very quickly!

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@TomW Hi  we seem to be approaching the same problem from opposite ends literally.  You are improving the front pads , I am going for new rears that hopefully wont be as effective as the bedded in ones.    I have my retest next week, if I get through it with the new rear pads, I will put it down to me not reading the blogs in enough detail.  If it fails again, I agree it is time to have a discussion with WF and Steve as the kit is currently verging on the not fit for purpose.   WD40 is not an option, give them there due WF have never suggested that cheat.   

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41 minutes ago, TomW said:

@Two7 let me know how you get on with your test,  what pads did you use on the rears?

will keep you posted.  I went for the cheapest EBC pads £26 for 4 incl postage ( apparently they are the ones WF provide).  

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This was known issue at IVA 10 years back too. I fitted a pressure reducing valve to the rear brake line as it seemed like a more permanent fix. The factory said that they advised against it and that the fronts would eventually catch up with the rears, although they still supplied the valve, and 10 years on it still works perfectly. I can't complain about the braking, either overall or front-rear balance.

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I am not advocating others to do this but all three of my cars that have gone through IVA or SVA I took the standard rear pads and using appropriate safety gear I routed the centre section of each rear pad out to roughly double the size they come with.

 

Each car passed brake test first time no issue at all. They all were great on the road and my current car, which did not go through IVA as it was a rebuild, has the same set up on a live axle and never locks up unless we are heading for the armco, where they all do.

 

I do feel it would be an easy fix for Westfield to have some pads made properly with the area reduced in size to cure this once and for all without people having to resort to valves etc.

 

 

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1 hour ago, jeff oakley said:

I am not advocating others to do this but all three of my cars that have gone through IVA or SVA I took the standard rear pads and using appropriate safety gear I routed the centre section of each rear pad out to roughly double the size they come with.

 

Each car passed brake test first time no issue at all. They all were great on the road and my current car, which did not go through IVA as it was a rebuild, has the same set up on a live axle and never locks up unless we are heading for the armco, where they all do.

 

I do feel it would be an easy fix for Westfield to have some pads made properly with the area reduced in size to cure this once and for all without people having to resort to valves etc.

 

 

Yeah, I’ve been wondering about something like this,  the problem is if it fails iva for it, then fitting a valve means the entire braking section of the test needs to be redone which I’m keen to avoid, just wondering if I reduce the surface area of the pad would that decrease the braking force?

 

The pressure would still the the same just on a smaller point?

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