Being a cynic and having experience of car mechanics over many years (mostly good), I was not totally surprised when I was told I needed new discs as well as pads.
I can see some superficial scoring and they seem to have worn a bit over the years but appear to me to be in OK condition. What I have been told though is that if just the pads are replaced there is a danger of the discs 'shattering' under braking.
I know anything's possible in life, but does this sound feasible or is it a scam to extort more money from me (I said I am a cynic)?
Thanks,

Brian

 

Shattering? Um...I don't think so.

Yeah, I guess anything is possible but brake disc shattering is anything I've ever heard of, personally.

Brake "shuddering" is very common, though, and can come from the brake discs.

Ideally brake discs are resurfaced or replaced when new pads are installed. In actual practice, though, if the surface has only minor wear/scoring, many people just install new pads and go merrily down the road.

Discs have a specified thickness, easily measured. If they are below spec, or resurfacing them will put them below spec, they shouldn't be used. This is a legitimate safety issue.

Often new rotors can be sourced at very reasonable prices which makes resurfacing old rotors less attractive.

Cheers
DD

 

Thanks Doug for that very comprehensive reply - much appreciated.
A couple or so more more questions please. How do I ascertain what is the correct width of these discs and what tolerance is allowable below that (if any)?
Finally how can I measure this accurately? I don't have a micrometer and using a tape rule seems a bit unreliable.
Thanks again.

 

You were correct to be cynical. Routine replacing of rotors or blindly resurfacing them without cause is classic upselling by garages or parts suppliers. New pads need to bed into the rotors irrespective of the condition of the latter. A freshly machined surface or new rotor still requires this procedure to ensure optimum stopping power.

 

The specs are ofen stamped into the rotor. Or look in the service manual.

Can't measure them without a mike.

Cheers
DD

 

I have seen on most vehicles made today that the discs are already made at the design limit,so that they will be beyond repair limit when resurfaced. Usually when the discs get thin they have a tendency to crack.

 

In the good old days rotors had tons of "meat" and they could usually be resurfaced at least a couple times before reaching the legal limit or otherwise getting thin enough to cause problems.

<sigh>

OTOH they're generally fairly inexpensive to replace.....

Cheers
DD

 

Thanks again to all.