Front brake discs at 1.4 mil,should i change?

[moresquirt]

The pads appear to be lasting approx 50000 kilometers per,I have already purchased the porsche pads but not rotors ,there is definately no warpage at hwy speed and no hairline cracks near the holes.Based on the spec info i have given how much more wear will the rotors see before the next set of pads is toast,don,t have a problem changing the rotors out but not if i think i may be able to wear another set off pads on them.If my pads last 50000 kilometers that means i will have approx 90000 miles on the rotors,is that possible.

[shadrach74]

Originally Posted by moresquirt

The pads appear to be lasting approx 50000 kilometers per,I have already purchased the porsche pads but not rotors ,there is definately no warpage at hwy speed and no hairline cracks near the holes.Based on the spec info i have given how much more wear will the rotors see before the next set of pads is toast,don,t have a problem changing the rotors out but not if i think i may be able to wear another set off pads on them.If my pads last 50000 kilometers that means i will have approx 90000 miles on the rotors,is that possible.

It all depends on driving style. I can drive the 9 mile back road I live on with out braking at all if not forced to by obstacles or other motorists. If you're gentle, rotors could certainly last through 2 sets of pads. Do you know the history of the car?

Don't take too seriously the barking about reusing rotors that are in spec. A lot of folks derive pleasure from buying new parts and throwing perfectly serviceable parts away. The only real utility in it is that it makes them feel good, it does little to nothing for performance unless you're operating on the ragged edge.

If you do decide to replace the rotors, go with a reputable manufacturer and don't skimp on replacement parts quality. The parts market these days is hard to understand, sometimes I get more for less and often times it's the other way around.

[kk2002s]

I am in total agreement with re-using safe(within spec, no cracks, etc.) rotors with new pads. Even unturned, in-spec rotors should do no more than wear the pads a bit faster.
But - We live in a liability paranoid world so if I were a shop, new pads, new rotors would be the standard job.
I don't even think a customer signing a release (Old rotors, in spec, legal jargon, Blah, Blah, Blah) would release a shop from liability if there were an accident that could be some how traced back to stopping the car

So if your car is pure shop repaired, pads & rotors would be expected
DIY - its your call and your responsibility to keep it safe

[thstone]

Originally Posted by moresquirt

The pads appear to be lasting approx 50000 kilometers per,I have already purchased the porsche pads but not rotors ,there is definately no warpage at hwy speed and no hairline cracks near the holes.Based on the spec info i have given how much more wear will the rotors see before the next set of pads is toast,don,t have a problem changing the rotors out but not if i think i may be able to wear another set off pads on them.If my pads last 50000 kilometers that means i will have approx 90000 miles on the rotors,is that possible.

Well, at the rate of wear thus far, the next (3rd) set of pads would wear the rotors half the amount of the total wear or 28-26.6 = 1.4, then 1.4/2= ~0.7mm. Taking 26.6-0.7 = 25.9mm and the rotors will just be shy of being in spec at the end of the next set of pads.

Of course, rotor wear is a lot like the stock market in that previous performance is not necessarily a good indicator of future performance (but its all we have to go on).

[woodsman]

and so what's going to happen if your rotors are 0.10- 0.20" too thin when your new pads are worn out? NOTHING! They won't be able to absorb extreme heat (only found on the track) as well as new rotors would but only a driver who's driven MANY track miles could tell the difference. There are mechanics out there who insist that whenever they install new pads they MUST install new rotors as well!- forget machining they'll tell you, and why? Money.

[moresquirt]

Thx everyone for your input especially the mathmatic algebra lesson,(im weak in that area) but based on that info i feel pretty safe on making that 3rd set off pads with original rotors go the distance,and as mentioned i do not track and never will,i do occasionally drive hard but don,t do brake power slides ect.For those interested at now almost 93000 kilometers (55000 miles) i am still on the original drive belt which looks like new (have a new spare ready to go if needed) original water pump with no play in the bearing,its tight ,smooth and quiet,just changed my plugs,because, and probably dident need to as they looked perfect,no metal in the oil filter either (IMSB OK) , have to say this car has been pretty reliable so far in the 30000 kilometers i have owned it! Thx again

[Bigsmoothlee]

Originally Posted by woodsman

and so what's going to happen if your rotors are 0.10- 0.20" too thin when your new pads are worn out? NOTHING! They won't be able to absorb extreme heat (only found on the track) as well as new rotors would but only a driver who's driven MANY track miles could tell the difference. There are mechanics out there who insist that whenever they install new pads they MUST install new rotors as well!- forget machining they'll tell you, and why? Money.

I know this is late, but that is the stupidest thing ive read on this forum. Please do not give out ANY advice if you dont know what youre talking about. I dont know of any reputable shops that will slap new pads on unresurfaced rotors. You either replace the rotor, or you resurface it if it has enough material.

[stephen wilson]

Not debating min. thickness, but here's nothing wrong with new pads on an unresurfaced rotor, as long as it's worn evenly, and isn't grooved. I've done it for 20 years on multiple vehicles, including a race car. After normal bedding in, they're as good as new. I've never found someone who would skim cut a rotor, they always take too much material.

[Topless]

Originally Posted by stephen wilson

Not debating min. thickness, but here's nothing wrong with new pads on an unresurfaced rotor, as long as it's worn evenly, and isn't grooved. I've done it for 20 years on multiple vehicles, including a race car. After normal bedding in, they're as good as new. I've never found someone who would skim cut a rotor, they always take too much material.

+1

Fear of reusing a serviceable rotor without resurfacing is pretty unfounded. It happens 50 times a day at racetracks around the world without incident. It won't have that "perfectly smooth, all new components feel" but it stops the car just fine.

[woodsman]

Originally Posted by Bigsmoothlee

I know this is late, but that is the stupidest thing ive read on this forum. Please do not give out ANY advice if you dont know what youre talking about. I dont know of any reputable shops that will slap new pads on unresurfaced rotors. You either replace the rotor, or you resurface it if it has enough material.

I'm a machinist who's raced cars. Learn how to disagree without condemnation. This is a FORUM.

[Bigsmoothlee]

Originally Posted by woodsman

I'm a machinist who's raced cars. Learn how to disagree without condemnation. This is a FORUM.

As a shop owner, I personally took offense to your claim of "dishonesty" . I am straight forward with my clients, and I never use scare tactics to get people to do their maintenance in my facility.

In my experience, whenever I put a used rotor on the lathe, its usually worn unevenly or warped. This causes vibration and causes the pads to become noisy. The groves in the rotor overheat the pad ( since maybe 40% or 50% of the pad is making contact with the rotor until it breaks in ).

Can you get by if you slap new pads on an old rotor? Probably. Will you get cancer watching your food rotate in your microwave from the radiation coming out of it? Maybe, maybe not. Should you accuse a shop of being money hungry because they want their client to do the job correctly? Absolutely not.

[woodsman]

Originally Posted by Bigsmoothlee

As a shop owner, I personally took offense to your claim of "dishonesty" . I am straight forward with my clients, and I never use scare tactics to get people to do their maintenance in my facility.

In my experience, whenever I put a used rotor on the lathe, its usually worn unevenly or warped. This causes vibration and causes the pads to become noisy. The groves in the rotor overheat the pad ( since maybe 40% or 50% of the pad is making contact with the rotor until it breaks in ).

Can you get by if you slap new pads on an old rotor? Probably. Will you get cancer watching your food rotate in your microwave from the radiation coming out of it? Maybe, maybe not. Should you accuse a shop of being money hungry because they want their client to do the job correctly? Absolutely not.

I think clients would appreciate the OPPORTUNITY to gamble on their old rotors (turned or not) before they fork out for new ones. I know radial run-out can be a persistent problem but so can over-cautiousness or a lack of sufficient funds.