candapack Posted July 15, 2014 Share Posted July 15, 2014 Van went through MOT today, passed, hoorah! The advisory section said both offside and nearside front brakes were "fluctuating, but not excessively". Garage was closed when I picked the van up (with spare key), in the meantime, does anyone know what that means. We're off in it mid August for 6 weeks, abroad. It's a 2007 Boxer, 21,000 miles, if that's of any interest. Link to comment Share on other sites More sharing options...
RogerC Posted July 15, 2014 Share Posted July 15, 2014 I would guess if the MH has been sitting for a while prior to the MoT the brakes might have developed a small degree of rust making them 'grab' in places which would cause the brake performance readout 'fluctuate'.................just a guess. :-) Link to comment Share on other sites More sharing options...
colin Posted July 15, 2014 Share Posted July 15, 2014 With that low a milage I would guess that the disc has raised spots where the pads have been 'shielding' them whilst the rest of disc rusts away, it's can get quite extreme on cars stored for a few years. Link to comment Share on other sites More sharing options...
Tracker Posted July 15, 2014 Share Posted July 15, 2014 I always take the van for a good long warm up thrash before an MOT as a hot engine not only gives the engine a better chance of passing the emissions test, but also several very firm and protracted applications of both foot and handbrake helps to remove or mitigate any deterioration due to lack of use. Every little helps particularly as the X250 handbrake is hardly one of the most efficient. Link to comment Share on other sites More sharing options...
candapack Posted July 15, 2014 Author Share Posted July 15, 2014 Thanks chaps. I did actually take it out on Saturday, did about 60 miles on a mixture of motorway and A and B roads. However, before that it had sat for nearly a month unused. At least it passed. :-D Link to comment Share on other sites More sharing options...
Dave Newell Posted July 16, 2014 Share Posted July 16, 2014 MOT advisories are just that, advice that in the testers opinion there are aspects which may warrant further investigation but not severe enough to fail the test on. If it was me I'd be having the front wheels off to inspect the brakes. It is often the case that discs rust and get pitted while standing and brake pads crumble with age. I change lots of brake pads but honestly can't remember the last set that were actually worn out as opposed to just falling apart. Not inspecting the brakes could be considered as looking into the barrel of Dirty Harry's Magnum, do you feel lucky? Well do ya? D. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted July 16, 2014 Share Posted July 16, 2014 A GOOGLE-search on "front brake fluctuation" will retrieve a fair amount of discussion relating to the MOT test (and mostly relating to motorcycles). The cause of the "fluctuation" is usually given as uneven brake-disc thickness - which would only be curable by replacing the discs. If the thickness unevenness is small, its effect might show up on test equipment but might not be noticed by the driver. Uneven thickness is not the same as the discs being warped, which should be noticeable when the vehicle is braked. As Dave advises, it would be wise to inspect the brakes to confirm the state of the discs (both sides of each disc) that should be well-polished, not badly pitted/rusted and not cracked. Link to comment Share on other sites More sharing options...
candapack Posted July 16, 2014 Author Share Posted July 16, 2014 Thanks Dave and Derek. I am an ignoramus on matters mechanical, but it surprises me that if something shows up on an MOT test that might warrant further inspection, that the tester blithely gives an MOT without doing any inspecting. Especially when it's to do with the brakes. I'll contact the garage today. Link to comment Share on other sites More sharing options...
Tracker Posted July 16, 2014 Share Posted July 16, 2014 The MOT test is just to satisfy the need for the brakes to be working effectively without pulling to either side. What the tester cannot see is the condition of the pads because they are hidden from view. It therefore makes perfect sense to me, as has already been said, to remove the wheels and physically check the condition of the pads and discs once a year once the vehicle is of MOTable age. Link to comment Share on other sites More sharing options...
colin Posted July 16, 2014 Share Posted July 16, 2014 If your van technically pass's the test then the tester should issue a cert, but he can also give you guidance on matters that are a pass but he feels might bear further inspection. Link to comment Share on other sites More sharing options...
candapack Posted July 16, 2014 Author Share Posted July 16, 2014 Spoke to garage. His bill is in the post, explaining that after the test, he did in fact strip the front brakes, and check and clean all components. It was indeed a rust build up caused by lack of use. Thanks again to all. Link to comment Share on other sites More sharing options...
EMS Posted July 17, 2014 Share Posted July 17, 2014 Perhaps Dave can explain why pitted discs are a failure point for MOT, when high performance discs are often cross drilled to permit the brake pad out gassing to escape? So being simple I would have thought that this pitting should aid heavy breaking for a heavy motorhome. Any ideas? (Sorry slightly off subject.) Link to comment Share on other sites More sharing options...
Billggski Posted July 17, 2014 Share Posted July 17, 2014 MOT's are a test of what the vehicle is like at that point in time, if the tester thinks that something needs doing before the next test it will be noted. I try to have a service and MOT at the same time, but with modern vehicles the servicing is computer timed, but this doesn't give me a picture of how things like brake discs, pads or tyres are wearing. There was a thread recently about brake pads crumbling that a visual inspection didn't pick up. Link to comment Share on other sites More sharing options...
Guest Peter James Posted July 17, 2014 Share Posted July 17, 2014 Tracker - 2014-07-15 8:32 PM the X250 handbrake is hardly one of the most efficient. That may be because the cables are incorrectly adjusted - it isn't just a matter of taking up the slack in the cables from any adjustment point. There is more than one adjustment point so that the levers and cables are pulling at the right angle to give maximum leverage. Since they banned asbestos the brake material they use now needs a lot of pressure to work. Link to comment Share on other sites More sharing options...
Guest Peter James Posted July 17, 2014 Share Posted July 17, 2014 EMS - 2014-07-17 2:36 PM why pitted discs are a failure point for MOT, when high performance discs are often cross drilled to permit the brake pad out gassing to escape? So being simple I would have thought that this pitting should aid heavy breaking for a heavy motorhome. Any ideas? (Sorry slightly off subject.) If the pitting was evenly spread around the disc, without weakening the disc, perhaps it would aid braking. But the pitting tends to form in one patch, causing snatching at that point. When I had that problem I took the wheel off and ran the engine in top gear so I could sand the disc smooth. Worked Ok for a few weeks, but then the pitting returned - it must have still been in the metal. In the end I still had to open my wallet and buy new discs 8-) Link to comment Share on other sites More sharing options...
Dave Newell Posted July 17, 2014 Share Posted July 17, 2014 EMS - 2014-07-17 2:36 PM Perhaps Dave can explain why pitted discs are a failure point for MOT, when high performance discs are often cross drilled to permit the brake pad out gassing to escape? So being simple I would have thought that this pitting should aid heavy breaking for a heavy motorhome. Any ideas? (Sorry slightly off subject.) Certainly. Performance discs are cross drilled and or grooved to allow more surface area to contact the cooling air around the disc, (brakes simply convert kinetic energy into heat though friction, that heat has to be dissipated from the disc or it will build up to a point where the friction material overheats and then stops generating friction). The difference between pitting and cross drilling/grooving is that the pitting is random and will leave a rough surface on the disc which will drastically reduce the surface area contacting the friction material. The cross drilling/grooving is done by machines and has countersinking/tapered edges to avoid excessive abrasion of the friction material while increasing air flow over/through the disc to aid cooling. In essence a badly pitted disc may have only ten per cent of its surface area left to contact the friction material while the cross drilling/grooving of performance discs is likely to be less than ten per cent of surface area. Porshe brake discs for example are not only ventilated but handed, the vents in the centre of the disc are shaped (like a wter pump impeller) to draw air into the centre of the disc structure during normal forward motion, fit them on the wrong sides and they're likely to overheat in hard use because they will repel the air flow through the disc. D. Link to comment Share on other sites More sharing options...
EMS Posted July 17, 2014 Share Posted July 17, 2014 Thanks for the reply, I have had to replace discs when the vehicles do not get enough use (this was when I cycled to work every day) now it is just the motorhome that gets less use. A sign of old age and retirement I suppose! Link to comment Share on other sites More sharing options...
candapack Posted July 17, 2014 Author Share Posted July 17, 2014 EMS - 2014-07-17 9:20 PM Thanks for the reply, I have had to replace discs when the vehicles do not get enough use (this was when I cycled to work every day) now it is just the motorhome that gets less use. A sign of old age and retirement I suppose! If you're retired, shouldn't the motorhome be getting more use? That's what I thought when first me, then my wife, retired. But it doesn't seem to work that way, does it? Maybe something for its own thread - what keeps you from travelling when, in theory, you've got all the time in the world? Link to comment Share on other sites More sharing options...
Guest pelmetman Posted July 17, 2014 Share Posted July 17, 2014 candapack - 2014-07-17 9:58 PM Maybe something for its own thread - what keeps you from travelling when, in theory, you've got all the time in the world? Retirement is a serious business ;-)....................it takes years of practice to get right...............so the sooner you can start the better :D................... Link to comment Share on other sites More sharing options...
Derek Uzzell Posted July 18, 2014 Share Posted July 18, 2014 These links may be of interest http://mottester.wordpress.com/2011/02/19/pitted-brake-discs-again/ http://www.lakesidegarageservices.co.uk/lakeside-news/some-information-about-brake-discs-and-pads Link to comment Share on other sites More sharing options...
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