Xantia rear brake MoT failure - untrue!

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grizzlycx
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Xantia rear brake MoT failure - untrue!

Post by grizzlycx » 15 Oct 2019, 13:57

Hello guys

Does anyone have experience of dealing with DVSA over contested MoT failure?

My Xantia failed on rear service brake recently. Spent loads on refurbishing calipers (no parts) at a Citroen specialist and did all the usual. Still failed. Thought back to the old days and loaded the boot with about 100kg. Answer? Went through with flying colours. I thought that this 'remedy' had died with the GS.

My argument with DVSA is that their test and / or equipment is not able to handle a car with automatic brake balancing, thus making me spend unnecessary money on work and retests.

Any thoughts or experiences on this?

David

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white exec
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Re: Xantia rear brake MoT failure - untrue!

Post by white exec » 15 Oct 2019, 14:07

Sit the Tester in the boot, next time.
Seriously, though, it is an issue, and difficult to believe it is up to the driver/presenter to load up the car.

Would a full tank of fuel (petrol ≅ 0.74kg/L, diesel ≅ 0.83) do the trick?

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Re: Xantia rear brake MoT failure - untrue!

Post by Hell Razor5543 » 15 Oct 2019, 14:16

I had an occasion when one of my Xantias failed for the same reason. However, I KNEW the brakes were in good order (having had to overcome the slate hard corrosion), and the MoT centre was quiet. I asked the tester to do it again, but this time with two colleagues sitting in the back. He was sceptical at first, but was amazed when she passed the same brake test. I explained that the rear brakes were, in part, fed from the rear suspension, and if there was no weight in back the brakes were not really needed (and I also explained that this was why Xantias almost never wore out their rear tyres). All three testers said they would try to remember this in the future (but explained that as they had to deal with a lot of vehicles they could not rely on memory to cover all eventualities).

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Skull
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Re: Xantia rear brake MoT failure - untrue!

Post by Skull » 16 Oct 2019, 09:57

I see this loaded/unloaded brake test debate is back maybe we could have a poll of opinions......

I've had Xantia's for 12 years now most diesel's 1.9TD Estate / 2.1TD Hatch /2.0 HDi Hatch and lately an Activa 2.0 tct. Wether my variations are relevant is probably unlikely.

I've never had to load the boot for MoT testing purposes.

I did take various advice to load the boot for bleeding rear brakes and it did seem to help especially when initially cracking stubborn rear spheres off.

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Re: Xantia rear brake MoT failure - untrue!

Post by myglaren » 16 Oct 2019, 11:18

It certainly made a difference with the GS- rear brakes never worked unless it was loaded - as I discovered on the first longish trip with all the kids in the back seat - one of the rear discs sheared off, corroded to buggery.
Since I replaced the rear discs on it I regularly loaded it up with paving stones and ran it around for a couple of days, no further problems but did load it for the MOT.
Just because of that I continued to load up with the BX and the Xantia. The C5s are more often loaded with crap than not and have always been OK on MOTs.

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Re: Xantia rear brake MoT failure - untrue!

Post by white exec » 16 Oct 2019, 12:12

Skull wrote:
16 Oct 2019, 09:57
I did take various advice to load the boot for bleeding rear brakes and it did seem to help especially when initially cracking stubborn rear spheres off.
Citroen advice is to put (XM and Xantia) suspension on Highest when bleeding (rear) brakes.
This has the same effect as heavily loading the boot - it creates maximum pressure in the rear suspension (i.e. the brakes, when kept lightly applied to bleed).

Highest is also the advice for cracking off rear corner spheres, as it firmly clamps the rams, preventing them from turning and damaging the pipework.

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Re: Xantia rear brake MoT failure - untrue!

Post by Skull » 16 Oct 2019, 13:42

Yes indeed Chris we've discussed this on various threads - just saying that the debate about loaded boot for MoT Test has raised it's head again ... I digressed a bit :wink:

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Re: Xantia rear brake MoT failure - untrue!

Post by GiveMeABreak » 16 Oct 2019, 13:45

white exec wrote:
16 Oct 2019, 12:12
Skull wrote:
16 Oct 2019, 09:57
I did take various advice to load the boot for bleeding rear brakes and it did seem to help especially when initially cracking stubborn rear spheres off.
Citroen advice is to put (XM and Xantia) suspension on Highest when bleeding (rear) brakes.
This has the same effect as heavily loading the boot - it creates maximum pressure in the rear suspension (i.e. the brakes, when kept lightly applied to bleed).

Highest is also the advice for cracking off rear corner spheres, as it firmly clamps the rams, preventing them from turning and damaging the pipework.
I always needed to do that on my XMs when replacing brake pads - and pumping the foot - controlled hand brake.

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Re: Xantia rear brake MoT failure - untrue!

Post by grizzlycx » 17 Oct 2019, 17:48

Hi guys

Just had the 'definitive' answer from DVSA which is attached below. In my opinion it says nothing but the most interesting part is that 'there is no evidence of the problem'. This is just the first contact, I will appeal the test anyway.

quote

Please see the below response from our vehicle testing and roadworthiness team.

Most modern vehicles are designed to do a high proportion of the braking with the front wheels and very little at the rear. This is primarily because there is very little weight at the rear of the vehicle and increased rear brake bias could cause the rear wheels to lock and make the vehicle unstable, although this is not so much an issue with anti-lock braking systems it is still undesirable.

In respect of testing brake efficiency, the vehicle is required to be maintained so as to meet the legal minimum brake effort defined by regulation at all times. Unfortunately, brake efficiency testing is not an exact science, with different methods of testing and numerous variables that can affect the result.

There are three approved methods of brake testing for MOT test purposes. The most commonly used method is a roller brake test, whilst some garages use a plate brake tester. There is also a decelerometer which needs to be used on vehicles that are unsuitable for roller brake testing, usually because they are four wheel drive. All three methods have advantages and disadvantages, but a vehicle with a well maintained braking system should pass the test without difficulty regardless of the test equipment used.

In this case, a roller brake tester was used and the vehicles service brake performance only achieved 44% which is below the 50% minimum requirement. The rear brake efforts were particularly low at 50kg/f and 45kg/f, but this is not uncommon on some vehicle types. The front wheels locked up on the rollers with readings of 310kg/f and 350kg/f. This left the vehicle 85kg/f short of meeting the minimum efficiency requirement.

Clearly we are unaware of the way the test was conducted and the conditions present at the time of test. However, the variables that can affect the result include:

Brake applied too quickly when testing the front brakes resulting in ‘lock-up’ when a higher figure could have been achieved
Brake rollers worn so a reduced coefficient of friction allowed the front wheels to lock prematurely
Wet weather reducing the coefficient of friction between the tyres and the rollers causing the front wheels to lock prematurely

Ultimately, we have no evidence that vehicles with correctly maintained braking systems are failing the MOT test. The test equipment and test methods used are the same throughout the EU and comply with the requirements of the European Roadworthiness Directive.

If a vehicle fails an MOT test for any reason, there is a statutory right of appeal if the owner disagrees with the test result.

I hope this information has assisted you with your enquiry, but if you have any further questions please do not hesitate to contact us again.

unquote

Perhaps this is something for the CCC to take up, or is it too old or infrequent?

Thanks for the info Skull, and this is my first failure on brakes ever - from DS to Xantia and all models in between. And the car is six years with me so far and tested at the same MoT station.

Watch this space.

David

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Re: Xantia rear brake MoT failure - untrue!

Post by Hell Razor5543 » 17 Oct 2019, 18:05

I have, I believe, a reasonable suggestion (if it is acceptable to the Moderators and will not compromise the security of members' cars).

For the next few months (time dependant on those who are interested) Xantia owners take their cars to be MoT'ed without any extra weight in the boot. This means they probably will fail (with an appropriate failure number). Try, if you can, to see the method used for testing the brakes. Then take it back with sufficient weight in the boot for the rear brakes to work (normally you get a 14 day free retest, provided certain conditions are met). Next, post up the failure notice number here. After an agreed period of time we could then contact the DVSA with the details of each failure (and, if available, how they were tested) so they can have something more concrete to work with.

OK, this may not help, as the number of Xantias is falling, but what about other cars with a similar system that may be receiving incorrect failure results?

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Re: Xantia rear brake MoT failure - untrue!

Post by andy5 » 17 Oct 2019, 19:02

Mine has never failed with this problem.

Apart from trolley jack (for trailer), jump leads and other tools, even the fuel tank contents can weigh up to 50 kg.

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Re: Xantia rear brake MoT failure - untrue!

Post by momag46 » 20 Oct 2019, 10:59

Same here, v6, never loaded boot and never had a mot failure on brakes.

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Re: Xantia rear brake MoT failure - untrue!

Post by grizzlycx » 20 Oct 2019, 11:03

Good suggestion James.

And regarding andy5's remarks I know the fuel was low on this last test and probably full on previous ones. Normally I carry very little in the boot.

Rugby semi-finals - how fab!

David

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Re: Xantia rear brake MoT failure - untrue!

Post by grizzlycx » 07 Nov 2019, 14:17

Have heard back from DVSA, and am now appealing the failure informally.

It does seem that a tankful is / was the answer but my argument is that if you must 'prep' a vehicle out of the ordinary then the test must be inaccurate.

Rugby finals - how sad!

David