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New rotors?
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Comments
On most rotors the minimum safe thickness is cast into the rotor itself. Measure the rotor, subtract the amount of material that will be removed by turning them, and you have a number that will tell you whether you should replace them or just have them turned.
Of course, if the rotor is cracked or shows any kind of damage, they should be replaced. For most cars new rotors are cheap so most folks just replace them and don't worry about it.
Too bad that most new rotors (OEM) are such junk that they almost always have to be replaced. Either because of warpage or the pads go right through them.
I think rotor turning is sometimes wasteful for the consumer but a nice little moneymaker for shops.
Of course, I would not do this with any rotor that is heavily scored or warped. But on a car that has been braking smoothly and only needs new pads, I wouldn't turn light scoring, no.
Every time a layer of metal is taken off that rotor or drum can't deal with heat as well.
The cleaner and smoother the surface, the less likely you will have undesirable noise.
Harry
"I may be a bit more liberal than you, in that I don't feel the rotor needs to be turned or discarded for "any bit of damage". A few light grooves I don't think appreciably hurts braking performance...but I do mean 'light' grooves. "
However, the pads will form to the configuration of the rotors. The key thing to look for is straightness of the rotor. A warped rotor will indeed provide premature wear of the pads.
"Hasn't been my experience, namfflow. With light scoring, I have inserted new pads and had no problems whatsoever, and I've done this on any number of vehicles. {lucky thus far} What happens is that the pads bed into the light grooves after a short time....in fact, if you think about it, with grooves you actually get a slight improvement in surface area.
I think rotor turning is sometimes wasteful for the consumer but a nice little moneymaker for shops. "
For five bucks a rotor, it is worth it.
"I think it might be appropriate to use emery cloth or sand paper to take of the glazing existent on the rotor the effect of glazing on a rotor is similar to a tire that is hydroplaning the pads never really grip the rotor that well there is always a light barrier that could impede breaking efficency "
Sand the pads to a roughness turn the rotors to a straightness to provide a uniform contact and avoid future problems.
Routinely replacing rotors with pads??? That's a new one on me...am I being scammed??
Does anyone have the Passat rotor specs??
However there has no been a paradigm shift, with regards to wear in that the rear brake pads can wear out quicker or just as fast as the front reason being that the rear brake pads material is organic and susceptible to faster wear rates in part due to the softer compound whereas the front brakes are now semi-metallic or ceramic or kevlar or carbon materials, yet in most cases just using sandpaper or emery cloth to take out the glazing is sufficent and not more attention needs to be given barring of course you didn't deeply score them
Long before the rotors are worn out they are out of spec [runout] thus the need for periodic refinishing [trueing] of surfaces.
The major problem occurs when people buy used as they have no new reference.
Typically the rotor wear spec is 1 mm per side to replacement and the pads have a 3-4 mm to midpoint thickness.
Most rotors on even very heavy luxury cars should last at least 40,000 miles before replacement some can double this life, not true with SUV.
I can live with a few grooves at those prices.
This takes 15 minutes per rotor additional.
We charge $40 per rotor for trueing plus another $25 for this precision alignment on Q45, after much work we can usually get below 0.0028" installed with lugs tightened to torque against rotor.
Less than 1 in 500 owners are willing to pay for a perfect brake job they perfer to save $80-$150 and put up with the vibrations [and rear rotor skipping] when stopping from 70 mph.
A perfect spec rotor can be way out when mounted to a dirty warped hub [which must be held to 0.001" or better].
http://www.brakealign.com/
For brake runout correction plates
http://www.hunter.com/pub/product/lathe/3947T/3947t-10.htm
I might add that this was never a problem until a local independent shop turned the rotors off the car and used Bendix pads. I now use OEM pads and don't bother turning the rotors unless the pulsation has returned.
That's odd! I've used ol Bendix on my stroller when I was six months old. I never had any problems with bendix. I use them today.
I must mention that if you use the same pads, use a piece of sand paper on a wooden block to rough em up a bit and to get them flat. After a rotor turn, you need to (excuse the pun) re-brake em in.
The proper way is to use hub compensation plates [between hubs and rotors] [or replace out of spec hubs] and index rotors to better than factory runout specs.
Some cars are very sensitive to runout errors some are not. Any [steering wheel] vibration when brakes are applied at 60-70 mph indicates rotor runout problems!
Harry
thank you,
Mr. Shiftright
Host
I also know what new rotors for this car cost. I just have not figured out how to remove the old ones. They are bolted on with 4 bolts and also appear to be pressed on the hub.
I am open to suggestions for the next brake job.
90% of Cheap rotors don't meet OEM specs for runout out of the box, plus what metal there is is usually less dense [poorer quality than OEM].