This has just got worse over the last few days.

On braking, I get a mild "lumpy" vibration and a "duhm duhm duhm duhm" sound as I come to a stop. Seems to be coming from the front passenger side.

Discs and pads all "look" OK. Not all that old (new on July 2010 with Mintex pads)

http://www.fullfatrr.com/forum/post21560.html#21560

Braking efficiency not affected, but taking it easy.... .

So warped disc? or caliper problems? .
Experience is the only genuine knowledge, but as time passes, I have forgotten more than I can remember
Volvo V70 P2 2006 2.4 Petrol 170bhp Estate SE
MG Midget Mk1 1962

Previous: L322 Range Rover TDV8 3.6 2008; L322 Range Rover TD6 3.0 2002; P38A Range Rover V8 1999

Last edited by Joe90 on 24th Mar 2012 4:11pm. Edited 1 time in total

food for thought:

Several years ago I read a paper written by a disc brake expert who claims that warped discs are a myth and can always be explained by a layer of brake pad material distributed unevenly on the surface of the discs. Since then, I have solved virtually all brake driveability problems on cars and trucks by following the recommended break-in procedures outlined in the "white page" article on the website stoptech.com. I'll have to admit that I too have the problem of rear disc brake squeal that is common on these bikes, but still haven't broken them in as I have on cars. I'm not really anxious to heat my bike's discs up until they discolor just to stop a little bit of squealing.

Without further ado, here is the link to the article: Warped rotor myth Just to reinforce the claims made by the engineer, and now me, that disc brake warping is a myth and can be corrected by breaking the pads and discs in correctly please read the rest of this post.

I came upon this article after I bought my 1997 Lincoln Mark VIII. I found a car club online (lincolnsofdistinction.com) where it was considered universally that these cars were notorious for warping disc brakes. I began researching and found stoptech.com. After much debate, I asked one of the fellow owners to send me a set of his expensive, drilled rotors that he had just removed and replaced for me to evaluate. As a machinist, I inspected them thoroughly and found that they were not warped (less than 0.001" runout on either side) and the two sides were parallel within 0.0005". I mounted them on my car and went for a drive. Sure enough, they seemed to be warped and caused the car to surge rhythmically upon braking. I went through the break-in procedure as describe on the stoptech article and voila- no more warped feeling. I drove with that same set of rotors for another trouble free 5000 miles until I sold the car and bought my 1998 Collector's Edition. Naturally, I reported back to the original owner of the discs that I found the problem the first day I received them, but he refused to want the discs back stating that he had "moved on".

I have subsequently solved the "warped disc" phenomenon in every case where I could convince the complainant of the break-in procedure. I have not had a set of discs "turned" or replaced since at least 1999.

When I came to realize that even if the discs warped (wavy shaped like a potato chip) they would have no effect on the radial motion of the wheel, I knew that the stoptech engineer was right. The only thing that would affect the smooth stop was uneven friction or unparallel disc surfaces. Barring the uneven collapse of the disc due to poor casting or cracks of ventilated discs, there's no reason for a disc to pulse radially when applied. Even if the disc surfaces were miss-machined and not perpendicular to the wheel axis they would have to move the caliper to the limits of clearance for the side-to-side motion to be felt by the driver and that is unlikely to change with usage.

http://www.1130cc.com/forums/showthread.php?t=122885
more
http://www.stoptech.com/technical-support/...ther-myths
http://www.mossmotors.com/SiteGraphics/Pages/brake_discs.html
and much more if you google warped+rotor+myth

If you do give the bed in procedure a try, let us know if this helped. I am very curious.
Back when I was a tech, we replaced rotors in cases like this. 
RRC 2Dr, RRC 4Dr,
P38, and 2 L322s
(wife thinks I'm nuts - prob right, too)

This works to a certain degree and was shown on the FCCUK forum a long long time ago and seemed to work well for me, i had dimpled and grooved discs with Pagid Blue/grey pads  FFRR MY06 facelift With TDV8 Alloys Zeros/ATR's
Mantec Sump Guard, Rigid Load liner, MY10 BT upgrade.

Hi,

This could be a seized calliper, get it looked at straight away, and rescue ur discs

Sal RANGE ROVER OVERFINCHED 4.2 S/C
FRONT BUMPER O/F
REAR BUMPER. O/F
BOOT SPOILER O/F
22" ALLOYS. O/F
STAINLESS STEEL EXHAUST O/F
CARBON FIBRE WING MIRRORS & A PILLARS & CENTRE CONSOLE

Check the wheel hubs for heat after you have driven the vehicle, if one is warmer than the rest then you may have a seized caliper on that corner 56 TDV8 Vogue SE
9 Freelanders, 2x 2002 TD4ES, 2001 TD4, 2002 1.8GS, 2000 XEDI, 2x 2000 1.8ES, 2004 1.8 & 2000 1.8 GS (rolled)
91 Lotus Carlton (sold)
90 Lotus Elan (BRG)

Will check for heat, and give the bedding in process a go, and report back. Thanks for all the info, especially SteveMfr - interesting read  .
Experience is the only genuine knowledge, but as time passes, I have forgotten more than I can remember
Volvo V70 P2 2006 2.4 Petrol 170bhp Estate SE
MG Midget Mk1 1962

Previous: L322 Range Rover TDV8 3.6 2008; L322 Range Rover TD6 3.0 2002; P38A Range Rover V8 1999

NO excessive heat on any of the hubs.

Had a go at "bedding in" this morning on the way to work, but could only do x4 "60 -5 mph" brakings. No big difference, but appears slightly better. Will find a quiet road late at night for this I think. .
Experience is the only genuine knowledge, but as time passes, I have forgotten more than I can remember
Volvo V70 P2 2006 2.4 Petrol 170bhp Estate SE
MG Midget Mk1 1962

Previous: L322 Range Rover TDV8 3.6 2008; L322 Range Rover TD6 3.0 2002; P38A Range Rover V8 1999

It is interesting - tho since reading this article the first time several years ago I've not had the 'good' fortune of having a 'warped disc' problem on any car I've had to deal with. (and I've not bothered with bedding my pads on anything but on a track car)

While the writer of the item I posted above does suggest that you can fix a pulsing pedal by re-bedding, the original article by stop-tech suggests running a semi metallic pad or sanding the disc to remove uneven deposits.

I am still very curious if this will work. I remember back about 20 years ago ( I'm old) an acquaintance had a brand new Jag that was back at the dealer every couple of weeks for 'warped rotors'. I think the issue was never completely resolved.

I am now running cheapo pads and rotors on our ff and do quite a bit of driving on German autobahns. Hard breaking from 100+mph to ~25-30mph is, well commonplace is too much but not unheard of. No probs (knock on wood). 
RRC 2Dr, RRC 4Dr,
P38, and 2 L322s
(wife thinks I'm nuts - prob right, too)

That is very interesting reading.

I had a sticky caliper on a toyota emina import once, and it's really noticeable, not so much brake lumpiness, but just pulling one side & a groaning noise whilst it's binding! The heat off the wheel was incredible, so if you ever get one you will know just from the heat.

I also had problems on another toytota previa (uk model) with so say warped discs. Apparantly the toyota dealer had so many recalls, not only on their own make but other vehicles they sold they had invested in a disc skimming machine !
I'm guessing they never heard of the cure or maybe it was quicker & cheaper to simply skim the discs & replace the pads each time. The sales guy reckons they did them weekly.,....

Problem is where do you find a quiet road to do the fast stops in succesion these days ?

Simple,

industrial estates in the middle of the night or some old dead end roads

Googly maps is your friend Even doing it off motorway slip roads coming off the motorway can help a bit but not as good as successive runs  FFRR MY06 facelift With TDV8 Alloys Zeros/ATR's
Mantec Sump Guard, Rigid Load liner, MY10 BT upgrade.

hmmm not heat.

May be worth taking the caliper off, and cleaning up the caliper sliding pins, and the pad sliding surfaces on the barake carrier. i would als check the caliper piston for corrosion behind the dust seals 56 TDV8 Vogue SE
9 Freelanders, 2x 2002 TD4ES, 2001 TD4, 2002 1.8GS, 2000 XEDI, 2x 2000 1.8ES, 2004 1.8 & 2000 1.8 GS (rolled)
91 Lotus Carlton (sold)
90 Lotus Elan (BRG)

It got worse, but then became evident it was coming from the passenger side rear.

Dismantled brakes this afternoon, gave it all a good clean up, and this seems to have improved matters significantly.

Once I got the disc off (having released the handbrake lol) but with usual fight of leather mallet and large levers, it was full of muck inside.

The caliper was not seized.

The disc has a rusty depression all the way across @ 3mm wide, surrounded by what looks like heat damage. I gave the disc a good clean and used a rotary flapwheel sander on my drill.

The pads were in good nick aside from the inner edge, where it seems they are acting on the inner edge of the disc where there is a ridge.

So cleaned everything up, a bit of copper ease on the guides and the face of the drum to stop the wheel sticking, and all back together. Took for a test drive, and although there is a faint rumble, nothing like the noise and vibration i was getting before. The whole lot really needs replacing, a job for later in the year.

Photos here:

http://www.fullfatrr.com/gallery/thumbnails.php?album=454 .
Experience is the only genuine knowledge, but as time passes, I have forgotten more than I can remember
Volvo V70 P2 2006 2.4 Petrol 170bhp Estate SE
MG Midget Mk1 1962

Previous: L322 Range Rover TDV8 3.6 2008; L322 Range Rover TD6 3.0 2002; P38A Range Rover V8 1999

Pleased to report that replacing with new discs, pads and shoes at the rear has solved the vibration. Looking at the new discs made me realise what a shocking state the old ones were in!

Even with the adjuster right off, the new disc takes a bit of a bash with the hide hammer to get past the new brake shoes.

I followed the bedding in process as indicated by Steve MFr earlier in the post as well, on returning home and parking up there was a lovely smell of hot linings

Will run for a week or two then re-adjust the handbrake.

Tip: When you have the disc off, make a mark on the disc guard to indicate the location of the adjuster cog, it is off centre from the vertical and may depend on which way round you put it on (or is fitted). I have both cogs to the rear of the adjuster.

Photos here:
http://www.fullfatrr.com/gallery/thumbnails.php?album=454
-
- .
Experience is the only genuine knowledge, but as time passes, I have forgotten more than I can remember
Volvo V70 P2 2006 2.4 Petrol 170bhp Estate SE
MG Midget Mk1 1962

Previous: L322 Range Rover TDV8 3.6 2008; L322 Range Rover TD6 3.0 2002; P38A Range Rover V8 1999