Brake pad wear: Front Vs Rear

[Bobby Dazzler]

Our ML seems to like having it's brakes overhauled in July-ish every other year, and it seems this year is no exception...

...a matter of hours before we set off on our 1,000 mile round trip caravan holiday - towing a heavy twin axle - the brake wear warning light lit up!!

Whilst towing is heavy on the brakes fortunately much of the distance covered was motorway driving and so the affect of towing should have been neutralised.

It had new pads all round just before it's second birthday, which I fitted with a little help from Snr Dazzler.

Two years and 24,000 miles later the disks and pads were replaced by the dealer under the Service Plus scheme.

Now - another two years and another 24,000 miles later - and it needs another set of pads at least.

I'm confident that the disks are fine, and it will just need pads, but I'm wondering whether the rears really need to be changed.

What's the combined wisdom, if I change the fronts will the current rears last until the fronts are due again?

My thinking is that the front axle does most of the braking, say 70:30, and tyres on a non-driven axle usually last at least twice as long as tyres on the driven axle, I'm thinking I could apply the same theory to pads.

 

[A210AMG]

Hello

As its just the pads I guess its not 'too' expensive especially if your doing it yourself. I would be tempted to change them so they are all new at the same time.

You could have a better look with the wheel removed when you do the fronts. If they look ok, wheel back on and grab a cupa tea

 

[Bobby Dazzler]

A friend of a friend has a garage and an ML and I'm hoping he'll swap them at a reasonable price for convernience (we're off again for 10 days in 10 days time).

If not, I'll do them myself.

Time permitting I'm picking up the parts tonight for the dealer for both axles, to be on the safe side.

 

[grober]

The reason you need to change the rears as well as the front is that the vehicle stability control and 4wd 4MATIC/ ETS system on the ML makes extensive use of each disc/pads on individual wheels. http://www.whnet.com/4x4/ets.html They act in a similar way as locking differentials to give you 4WD. That's why the the rears wear out in a similar fashion to the fronts. If it were me I would renew the rears before you go.

 

[BlackC55]

ML's always wear rear pads faster for some reason.

 

[Bobby Dazzler]

I ordered new pads for both axles as soon as Mrs D spotted the warning light, and picked them up today.

New pads (both axles), four sensor wires, four sachets of paste, for £129 from the dealer. Fairly reasonable.

Just got to fit 'em now!!

If I remember I'll get some photos to compare wear rate of Front Vs Rear.

PS I'm aware that one of the reasons MLs tend to be heavy consumers of brake pads is ETS, although given that we don't drive it hard I doubt it has to intervene that much. Maybe towing increases that a touch as the stability control perhaps works a little harder, as well as brakes having to work harder due to increased mass. Will soon find out when they're replaced!!

 

[grober]

The background to my theory as to why the rear brakes wear more is detailed here. Wolfgang's MB Page: ESP, ESC stability control Given that most modern cars/SUV's are set up to understeer vehicle dynamics will dictate the ESP system will be preferentially braking the rear inside wheel in corners on alternate wheels [depending on the direction of the corner] to maintain stability leading to increased rear pad wear. Well that's my guess anyway.

 

[Bobby Dazzler]

True enough, it was the rears that had triggered the sensor, despite having had new discs and pads fitted at the same dealer at the main dealer.

Very little friction material left on the rears. I didn't measure, but I would estimate close to 10mm of friction material left on the fronts. I didn't look at the new ones to see how much they come with but that seems like quite a lot to me!!

I didn't fit them in the end as it's getting very close to our next holiday (Friday) and didn't fancy risking another 1000 miles towing on the old pads. A local garage fitted them for me today.

Parts cost £129 from the main dealer - which works out at 33% discount I believe.

Fitting cost £40 but I gave him a £20 tip - so £60 fitting.

Total cost £169 (or £189 including tip) for fitting them with zero notice using MB parts.

So pleased I've now booked it in for it's MOT in September rather than go to the dealer which is what I normally do.

Incidentally the mechanic is a bit of an MB fan - ML in particular - and rates it as a towcar. He's had a W163 ML for 5 years now, and just recently bought a W164 ML320 CDi. How greedy is that?

In that time he's covered 60,000 miles and has never once had to change even the pads never mind the discs. He also said being a mechanic, finding time to service his own car is a last resort, and despite this hasn't had to repair it!!

 

[Bobby Dazzler]

It seems ou ML likes new pads every 2 years and 24,000 miles, but to my surprise the latest have lasted almost 5 months longer. Precisely 24,000 miles though!

My guess is they lasted longer because the last set were fitted after the summer holiday season of 2009 rather than part way through, typically when our monthly mileage spikes dramatically and we're towing long distances with the caravan along for the ride. I reckon the pads see as much action in August as September to December combined.

Dealer prices have gone up dramatically in 2 years. My usual dealer parts counter quoted me £180 for pads and sensors, and a different dealer quoted £240 having made me wait 30 minutes.

ECP supplied Pagid pads next day for £77 including sensors, and the same chap could also fit them next day for £50, plus a tip. A good result.

I reckon I'll be updating this thread in April or May 2014 with another 24,000 miles under the wheels, unless tese Pagids wear quicker.

 

[renault12ts]

Surely its the mileage which is important...not the time. They have lasted 24,000 as usual.

 

[Bobby Dazzler]

Yes same 24,000 miles but it just took longer to cover that mileage as they missed the summer spike when the car covers more mileage.