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Bedding-in brakes: How long



  Clio 197


How many miles does one "bed-in" brakes for?

I can see that the pads still arent 100% in contact with the discs yet...

I know I know... how long is a piece of string?





But seriously... I dont want to go hard on them too early.
 
R

rich[182]



dont know what you should do, only say what ive done

had disks n pads (std) on front last friday, drove slowish over weekend and braked lightly, braking more normal now but wont be braking harder and driving normal til this weekend when ive done 300+ miles on them, did same from new too

ps got 24.3k out of original disks and pads and they were still ok so it cant have done any harm lol


[Edited by rich172 on 23 August 2005 at 1:18pm]
 
  Ziel Nurburgring


About 10 laps of Oulton Park and then back up to full speed. :oops:

A few hundred miles should do it, and youll get that done in a day or so wouldnt you Oms?
 
  Clio 197


True...

I did Taunton to reading last nite, and only braked as I was turning into Arbor lane...

NO traffic at all.



Can we do a brake-christening run today?
 


Bed them in about 10 mins is the way I do it.

Get up to around 60-70mph and brake hard down to around 10mph around 3-4 times until just on the point of fade.

Then drive at around 40-50mph for around 2-3 mins without touching the brakes to let them cool and thats it. Job done.
 
  The Jinx


" I spoke to MSW who sold me my Mintex, also read a few articles including one by a Ferodo engineer about pads & bedding-in.

OK so we all know that your common or garden car brake works by pads in a hydraulic caliper gripping a rotating disc. But within that there are actually 2 types of friction at work: abrasive & adhesive.

Abrasive friction is what youd commonly think - pads gripping i.e. rubbing the disc. This happens at start and low temperatures. The pads need to have a decent amount of physical friction to grip a disc when theyre cold, something ultra-hard high temp race pads may not Shock

A new set of pads will need to be run-in to allow bits to compress and physical interface with the disc surface (any rut and pits) to marry. So you run them medium gently for the first 75 miles (150 if new discs as well), avoiding emergency stops if possible. This should press the pad together and "break in" the surface of the pads with the disc..

Then theres adhesive friction. This is the one that youre using when the brakes are up and running temp. By depositing a layer of friction pad material onto the disc, when its hot the brake pad surfaces are making and breaking bonds to the pad material stuck on the disc. Result, even stronger braking Cool This is where temperature by-product is being used to an advantage, and unlike abrasive shouldnt wear your disc down much - worn F1 & race discs can be as thick or even thicker than when put on! Crazy as the pads have deposited their guts onto the disc.

So to complete the bedding process, you need to bed your pads & discs in for the second kind of friction as well.

In plenty of space or on your private airfield accelerate to 60mph, then brake at 80% effort down to 10mph. Take it back up to 60, down to 10mph. Do 8 such stops but avoid coming to a complete halt! At first the braking feel and distance should steadily improve. But note that halfway through the stops you may get a soft pedal, cooked brake smell, even burning! Dont panic, this is called "Green Fade" and is simply solvents and chemicals used in the pad manufacture burning off & consolidating.. Stick with it. Incidentally, full-on race pads get little or no "green fade" so its all about getting those up to temperature.

Once the above stops are done, take a 15 minute cooling run at motorway speed and avoiding complete stops with the brakes applied. Try the brakes, should feel good. If not let them cool off & repeat above procedure.

Thumbs up

Note about glazing: Yes pads that have exceeded their working temperature may glaze over..this is more common with new discs at same time as pads, but basically be careful what temperature youre putting into them. The 6 is not that heavy a car and on the road doing the above stops should not overheat our pads, but it may take longer to get a decent "abrasive" surface before stop runs can be done"

Copied from elsewhere.
 


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