Renault Forums :: Independent Renault forum - View Single Post - Rear Brake Pads/ Discs in 59 reg Scenic

View Single Post
post #5 of (permalink) Old 26th January 2014
Diamond member
Join Date: Oct 2013
Posts: 166
Nominated 0 Times in 2 Posts
TOTW/F/M Award(s): 0
Thanks: 3
Thanked 52 Times in 39 Posts
Re: Rear Brake Pads/ Discs in 59 reg Scenic

Originally Posted by Dancingdad View Post
14k does seem a little on the light side for rear pads, best part of 30K on the second set does seem more reasonable.

Discs, personally I reckon discs ought to be good for 100K at least but designers don't seem to agree with me
If memory serves, Renault specify 0.5mm wear per side (1mm overall) as maximum wear.
That's a set of discs every time a set of pads needs replacing

Mechanically there is no need for this limit. The true limit is the maximum travel of the piston minus the full wear of the pads plus a safety factor. Which will work out far more them 0.5mm

There is also the worry about physical strength reducing as discs reduce in thickness and too be fair they have to think of one pad sticking and load being one sided.

Thermally, it's more difficult and is based on heat gained versus cooling area and volume to absorb the heat and again they have to consider worst case.

There is also the case that with every available ounce being saved for fuel economy that discs and many other parts are far skinnier then they used to be.
But I still wonder whether this is a true safety consideration or a money spinner.

I don't know so the only thing I can say is go with the specs but don't have to like em
Its not just Renault who specify this tolerance, most manufacturers specify the same tolerance.

1mm per side if its a vented disk
0.5mm per side if its unvented

if I can remember correctly.

yes unfortunately with modern pads it does mean a new set of discs at almost every set of pads.

but not just about wear thicknesses, usually by the time a disc wears down that much it is also no longer flat... and if you stick a flat pair of pads on an uneven surface disc it takes a long time to wear to the shape of that disc, which means your braking efficiency is significantly reduced in that time, which maybe the difference between running into the back of another vehicle on a motorway or that child that runs out in front of you.. granted the brakes will still work until bedded in, but that 2-3 meter stopping distance deficiency would be the difference between life and death.

That's one reason why springing up more and more now are services selling disc grinding, they stick a machine on the vehicle and grind the disc flat before you install new pads... this solves this problem (but unfortunately most people don't bother with it) it does however create another problem, which is why disc thickness is specified also... cracking, and warping, 1mm might not seem like a lot, but over the entire surface of the disc both sides... that's actually a significant loss of metal.

Discs do however wear out quicker than they used to, its a misconception this is because they aren't as good quality.

vehicles are heavier than they used to be, and safety standards have been raised significantly so manufacturers always want to reduce their vehicles stopping distances because it literally is life of death every 1m you can knock off a stopping distance.

So pads are more abrasive now to grip more... which is good for safety, but not so good for disc wear, its also why discs tend to warp more now, because the heat generated is a lot higher due to the increased grip, brakes in general are more powerful than they used to be.
Currently in Click4's garage:
Click4 is offline  
For the best viewing experience please update your browser to Google Chrome