Last post on Oct 20, 2013 at 11:13 AM
You are in the Maintenance & Repair
What is this discussion about?
#1994 of 2028 Re: Why is is...? [jipster]
by MrShift@Edmunds HOST
Dec 06, 2010 (9:16 am)
Probably the only real advantage of not turning rotors is that, if you are a hard driver, a thinner rotor would probably warp more easily---let's say if you were coming down a long hill and then hit a puddle of water at the bottom.
It seems that many modern cars, especially entry-level types, are plagued with rotors that warp as easily as the tinfoil in an Italian TV dinner tray.
#1995 of 2028 Re: Why is is...? [jipster]
Dec 06, 2010 (9:25 am)
Sorry guys, the fact is, the thinner the rotor, the lower the thermal mass of said rotor; the lower the thermal mass, the higher the rotor will heat up with the application of any given amount of heat; the higher the heat the lesser the effective braking power. Is it significant? I believe it is and have read plenty of studies published in the SAE archives that back that up with hard numbers.
That said, you shouldn't believe some dumb schmuck on the internet; if you're interested in this kind of stuff you should do your own research. I've done mine and I change rotors at every brake job. That's my story and I'm sticking to it.
#1996 of 2028 Re: Why is is...? [shipo]
Dec 06, 2010 (2:03 pm)
Yes, the temperature rise is directly related to the mass of the rotor. The lighter the rotor, the more the temperature rise for the same amount of energy (heat) input.
That said, what kind of difference in temperature rise are we talking about for a machined vs a non-machined rotor? Well, we need an estimate of the before and after machining weight of the rotor.
Assume a stock rotor weighs 15 lbs. Further assume that after using up one set of brake pads (which wear the rotor) and then machining said rotor, it's weight it 14.5 lbs (0.5 lb metal loss seems high to me, but this will give us a worst case estimate or temperature rise).
Now, assume a braking scenario that raises the temperature of the stock 15.0 lb rotor 100 deg C. Then that same braking scenario, applied to the used, machined 14.5 lb rotor would raise its temperature 103.45 deg C, a 3.45 deg C increase.
So yes, the used, machined rotor does run hotter, but does the 3.45 deg C increase make that much difference?
If the rotor was half as heavy as the one I postulated (7.5 lbs from the factory), and the braking scenario twice as hard, the temperature difference between the two rotors would still only be 24.29 deg C.
I do not know if a 24.29 deg C difference in rotor temperature is significant or not. For the average driver who maybe needs to do 1 full blown panic stop from highway speeds a year, probably not. For those who like to push the envelope coming down a mountain, .
#1997 of 2028 All interesting...but
Dec 06, 2010 (5:50 pm)
The main reason for NOT turning modern rotors is because many are HARD SURFACED.... not because of loss of braking charictoristics. There is a min. number embossed on the casting to tell you what is safe. Turning them removes the all-important hardend surface whence the pads create friction.
Todays modern brake-rotor may be made up of several different materials.
- The hard-surfacing for the pads to bite into.
- softer material which conducts heat away.
- tougher material which resists warping near the bolt-holes
You may not be able to visually *see* these differences. Modern meterallgy tecniques like flame-hardening can make one cast peice have very different charactoristics.
Of course, you can always buy cheep rotors that will warp the 1st time you do a panic-stop.
Heck - the brake rotors on my motorcycle are aluminium inner section with fully-floating StainlessSteel outer area for the pads to bite into. (Just like race-cars use.)
Jan 03, 2011 (6:05 pm)
The brakes on my 2006 Toyota Avalon (46K miles) started to make a grinding noise. Pads were worn to the center groove but still has ~3/16" of friction material. Changed them any way, but the noise is still there. Rotors are smooth and brakes are steady.
#1999 of 2028 Re: brake noise [tedbart]
Jan 04, 2011 (3:17 am)
1. Is the grinding noise present all the time, or only when you are applying the brakes?
2. Can you isolate the noise to the front or rear?
3. Does the noise change if the wheels are being turned?
4. Maybe the water splash shield is bent and rubbing on the rotor.
#2001 of 2028 Re: brake noise [tedbart]
Feb 16, 2011 (11:25 am)
Are you using Toyota pads or aftermarket pads? I had my mechanic change the brakes on my 2006 Camry. Used napa Gold pads like he always uses on any brake job. Brakes started grinding. Replaced pads again and turned the rotors. Still grinding. Finally he just used Toyota pads and rotors. problem solved.
A cheaper solution would have been to replace the rotors with Napa brand but we both were so frustrated that he just used Toyota parts.
#2002 of 2028 Re: brake noise [dtownfb]
Feb 17, 2011 (3:42 pm)
Lets be realistic here. Noisy brakes may be an annoyance... but it is is not a "problem".
#2003 of 2028 Re: Brake fluid [jipster]
Feb 20, 2011 (2:26 pm)
Check these out... Phoenix Systems brake fluid test strips
measures the level of copper present in the brake fluid. Just tried these out as I had dealers for both my cars push brake fluid changes at 36K miles which seemed very early. Seem to work well and easy to use.