Turning rotors leads to warping?

[Riley]

I searched but could not find a suitable thread to address this in any detail.

Here's the deal. I need to replace my 80 series front pads again (it's likely time). The rotors were replaced by the PO just before I bought the truck. Let's call it 20K miles ago.

I'd really like to install the 100 series pads but not at the cost of my rotors. I know they either need to be turned or new (because the surface area of the 100 series pad is larger).

Questions are:

1) Does most of the gang think that turning the rotors will cause them to warp?
OR increase the chances?

2) I know a pretty good brake shop I trust, I would get them to turn them. I know I should ask them but are they turned while still attached to the hub assembly?

I really want better braking but I don't want to buy new rotors OR have warped rotors, that would really piss me off.

Thanks

Riley

 

[NorCalDoug]

I think it does. Got no proof. Except that the last time I had them turned they warped and I had to install a new set of rotors...front and rear.

Good thread topic though...I'm interested in reading what others have to say too...

 

[nyk438]

I've heard of it happening. Only thing that has warped my calipers is mud pits.

 

[spressomon]

My old Saab 9000 had undersized rotors. Living around Tahoe made it pretty easy to overheat them. I did prove to myself that turning those rotors was a waste of time and money (since less metal is left effectively it reduces the surface area for heat release). I finally bought some good high qual German rotors for it made from good metal...problem solved. Plus the braking power was enhanced too. When it comes time to rotor my '99 I am using Brembos or something similar...it's just not worth the effort/cost to turn them down IMO.

 

[Rich]

A proper job of turning the rotors is not going to cause them to warp. It won't materially affect the rotors ability to dissipate heat, the reduction is surface area is infinitesimal. A proper job of machining requires both a quality lathe in well maintained condition that is properly operated by an appropriately trained and qualified tech or machinist. An improper job of machining can leave the rotors in worse condition than they started.

The latest development in brake lathes machines the rotor while the rotor/hub is on the axle. The advantage of this approach is that run out in the entire rotor / hub assembly is minimized.

That being said, I would not go to the trouble of squeezing in 100 series pads, particularly if it required machining rotors that otherwise would not require machining.

 

[offroadkid]

I don't believe in machining rotors. Machining=less surface material=less heat dissapation (sp?) causing warping. At my work we machine rotors when doing a brake job. For the big Dodge trucks, we have an on-the-car brake lathe which allows you to machine the rotors while still on the car.

On my personal vehicles, they get a "pad slap." Well, actually only the Cruiser. The wife's Corolla doesn't need brakes yet, (going on 38K!!) Just my .02

 

[Radd Cruisers]

Do a google search, cannot remember for the life of me were I read this article on brakes.

Short and sweet, a race car driver claimed that he rarely if ever had seen a true warped brake rotor.

What happens is during break in mperiod the brake pad material adhears to the rotor and creates a lump which is harder than the pad and rotor. This in part creates the pulse you feel.

He claims that during break in you do not want to fully hold the brake while stopped for more than a few seconds, during this time that is when the heat and the pad create this lump on the rotor.

I always break in my customers new brakes prior to giving them the vehicle.

 

[Rich]

Josh, what do you think the surface area of the front disk is? What do you think the reduction is surface area is if you take a brand new disk and turn it to minimum thickness?

The answer to the second question is in the ball park of around an 1 percent or 2 max. That is not going to make a material difference to the heat dissipation capacity of the rotor.

 

[No power]

If the rotors are not that bad then
just pad slap it.
You'll be doing brakes in another
12k-15k anyways.
Get what you can out of the current
rotors and buy new ones when they
wear out .
JUST MY 2 CENTS

 

[Riley]

For sure if i just wanted to put 80 series pads back in then I'd not bother to turn them (that's not the question). The rotors are fine but I want to install 100 series pads. I figure it's going to be about another 10 years before the rotors need replacing. I'd like better braking now.

When running 33" tires, a little more brake is nice to have when your family is along for the ride.

I guess it's all down to Rich's point of finding an excellent shop that knows what they are doing. I'm not sure I have the solution to that issue.

 

[No power]

Sorry I'm a little slow
Good luck to ya

 

[Riley]

Sorry I'm a little slow

Guess that's what happens with No Power.... JK

 

[Rich]

The other part of the equation is that I am dubious about how much benefit is derived from slightly upping the surface area of the pads. The total force applied to the disk is determined by the master cylinder & calipers, not the size of the pad.

All else being equal, I would expect a larger pad to have proportionally better fade resistance. But having operated extensively in very steep western mountains, with the truck loaded to max (or beyond) gross weight, I have not had any issues with brake fad using presumably stock Toyota 80 series pads.

Now if the 80 & 100 series pads are made of different material, I would expect that could make a larger difference in performance. But if I was going to swap pad composition, I would think a better approach would be to research the alternatives that are sized to properly fit an 80 series.

 

[Kalawang]

I've had my rotors re-surfaced. It was cheap, quick, came out perfectly smooth and was a waste of money and time as a month or so down the road my rotors developed ridges or waves. I've since replaced them all.


Kalawang

 

[sixsracing]

Put the 100 series pads in without machining the rotors.

Best case scenario the pad takes whatever surface rust there is off the rotor and seat in.

Worst case scenario the rotor eats the small portion of pad that is hitting said rust and you have the equivalent of 80 series pads.

I don't believe it's really an issue. Where is the size difference between the pads? If it's length then no problem. If it's height then the pad will machine itself or the rotor.

Has anyone done any tests say from 60-0 MPH with new 80 series pads and then performed the same test with 100 series pads on the same truck?

I know this is a popular conversion I'm just wondering what kind of brake improvement we are actually talking about.

 

[miked]

Do a google search, cannot remember for the life of me were I read this article on brakes.

Short and sweet, a race car driver claimed that he rarely if ever had seen a true warped brake rotor.

What happens is during break in mperiod the brake pad material adhears to the rotor and creates a lump which is harder than the pad and rotor. This in part creates the pulse you feel.

He claims that during break in you do not want to fully hold the brake while stopped for more than a few seconds, during this time that is when the heat and the pad create this lump on the rotor.

I always break in my customers new brakes prior to giving them the vehicle.

i found this just the other day as i was doing a related search about brakes and pulsing. i think it is the article you are talking about. interesting read.
http://www.stoptech.com/whitepapers/warped_rotors_myth.htm

i once bought a set of drums made in <insert third world contry name here>. i had to return them because out of the box they were sooo warped, they hung on the shoes! when we tried to turn them in my dad's shop, the metal was so soft, it spiraled off the bit like we were peeling a potato. shop guys had a good laugh over that one.

 

[Bruneti]

I suggest going here: http://www.stoptech.com/technical/
and read up on this: http://www.stoptech.com/whitepapers/warped_rotors_myth.htm
this: http://www.stoptech.com/whitepapers/warpaway.htm
and this: http://www.stoptech.com/whitepapers/bedincontents.htm

This seems to be well written information for those of us who are not brake specialists (myself included).
With the weight of the LC, an aggressive downhill stop from high speed would likely be enough to start uneven pad transfer if you hold the brakes on after the stop. This condition will worsen until it drives you nuts. Many who report of warped rotors soon after they were turned are probably not aware of how to perform a proper "bed-in" of the pad and rotor. They would seem to be more likely to have uneven pad transfer because of this.

Since you know the age of the rotor, and assuming oem rotors or better (not midas or other of questionable quality), I would have your trusted brake shop turn them to get an even wear surface for the larger 100 series pads. Then install the pads, and follow the bed-in procedure to prepare the pad and transfer an even layer of pad material onto the rotor. If you don't know the quality of rotor, I would buy new oem rotors with the 100 series pads and bed them in.

 

[Riley]

Thanks everyone.

- The rotors were installed by the PO at the dealer, I would assume OEM.
- I'll read the above links later (at work). I've learned from this board about bedding of brakes. Good point.
- Rich (as usual) has some good points. It's hard to get a data point on the improvement of the 100 pads (maybe they are different material). Most guys I know that have done the upgrade have changed multiple things at once:

- board member A - changed the calipers and the rotors and installled 100 pads. Much improved braking but that's a lot of variables.
- board member B - changed fluid to synth (probably no effect), installed SS brake lines and 100 pads. I don't recall but would assume the rotors were turned. Again much improved braking.

Maybe I'm a good canidate to just change one thing and that's a rotor turn and 100 pads. I'll think about it, I've got a few days until the parts guy is back.

I'll need to calibrate my foot before making this change if that's the route I go.

PS. I wish I could fix my spelling error in the title. Maybe one of the mods could do that if they read this.

 

[miked]

having a sport bike that can reach 160mph educated me about the importance of proper bedding. first time i took it up that fast, sure enough, i had to scrub off all but 76mph as fast as i could. when the officer asked if i knew how fast i was going, i wanted to ask him at what mile marker he was talking about. anyways, i was not impressed with the braking performance so i looked into it. re-bedded the pads and tried it again. wow. really though, proper bedding shows more effect in prolonged twisties than a single high speed halt.

 

[ryanjl]

Based on my expeirience, I had my rotors 'turned' when I did my birf job a few years back, and ended up replacing them with new OEM ones within about 6 months because the turned ones had warped.

They were not turned beyond Toyota specs, so you can rule that factor out.


My theory on the 100 series pads, which I did install when I put new OEM rotors in, is this:

Yes, standard mathematical calculation would say that increasing the surface area of the pad would not increase braking performance without an increase in the pressure being applied to the pad, therefore negating any real difference between, in our case, an 80 series and 100 series pad.

My thinking, however, is that there are always some variables associated with friction. One area of a pad might not offer the same resistance as another due to minute variations in the material composition, etc. Increasing the friction area (i.e. using 100 series pads) decreases the likelihood of these variances influencing the total braking force.

But, a more quantifiable benefit to running 100 series pads is that they wear longer than 80 series ones.