Why cross-drilled rotors are stupid on an 80 (1 Viewer)

[Qball]

That's a great article. However, based on my experience, that's the difference between theory and reality. In theory, since I am using crossdrilled rotors, my braking should not be as good, but inreality, my brakes are better than they have ever been with the stock solid rotors. Now maybe it's the rotor material that's better and my crossdrilled pattern is not contributing to that. Regardless, I am enjoying my enhanced braking ability.

When people change out the rotor they usually change out the pads, bleed the brakes and maybe other things too.

Did you change ONLY the rotor and felt significant performance improvement from just the rotors?

 

[PurpleFJ62]

Side by side OEM rotors are way better than anything from the local parts store, but they do cost more. As they say you get what you pay for. Compare the non machined surfaces of the rotors, like in the cooling vanes. You will see a huge difference!

Maybe the 80 series crowd needs to get together and design a different front knuckle to accept a bigger brake package?

 

[Bambusiero]

The only reason cross drilled and/or slotted rotors were invented is to vent away high temperature brake pad out-gassing, which is one of the main causes of brake fade under repeated hard braking conditions. The out-gassing can create a gas bearing between the pad and rotor. They often put a slot in the pad for the same reason. Whether that happens or not, depends on the pad material content, it's thermal history, etc., etc.

But, as has been pointed out, it creates structural and thermal problems - disadvantages.

If that out-gassing is not happening, then cross drilled / slotted is all disadvantage, no benefit.
Which factor outweighs the other? Hard to say. Much testing required.
The "Truth about High Performance Brakes" article dismisses the out-gassing as no longer relevant. "But modern brake pads exhibit virtually none of this outgassing." Maybe, maybe not. I dunno. Also, sort of mis-describes it as "glazing" in one section. Glazing or burnishing could happen too, but that's something else - a full-time degradation, not fading.

Or - you just choose one, put it it on, and accept what you get.

"What? Me worry?"
Alfred E. Neuman

 

[Bambusiero]

Side by side OEM rotors are way better than anything from the local parts store. but they do cost more...

BTW. Does anyone have close-up photos of the OEM rotors? Not sure what they look like.
And how much are they?

 

[Bambusiero]

Like I said I'm no scientist or engineer but...

Everything you said sounds right to me.
signed - An Engineer

 

[TXBruiser]

We need a real world test were someone does a stopping test and measures speeds and distances with their non-drilled/slotted vs drilled and slotted vs just slotted

one of my 80s has slotted and drilled (purchased that way) and my other has standard non slotted/non-drilled. Only problem is the 1500lb difference between the 2 trucks creates too much of a variable.

 

[sunrk]

It's not about stopping distances though - it's about safety of the components when we're discussing drilled vs non-drilled or slotted vs non-slotted rotors.

The only way to do proper semi-scientific tests of braking benefits would be to take what could be considered a 'standard' 80 (by 'standard' that doesn't mean 'factory fresh' but your 'average street-level vehicle') remembering 80's stopped being made quite some years ago, and do multiple controlled tests with brake component combinations that can sufficiently identify valid results and scientifically reduce inconsistences and errors. That's hard to do.

I believe that the reason drilled rotors exist is because somebody thought it is another way to 'relieve' the effect of the hot gas layer between pad and rotor surfaces due to friction heating. That works only because the rotors have a 'hollow space' which gives somewhere for the hot gas layer to 'depressurise' into.

Slotted rotors came about basically for the same reason - the slots give a way to 'sweep' the hot gas layer.

The difference is that slots really do not provide anywhere near as significant an amount of 'weakening' of the casting in a way that can lead to catastrophic crack propagation under extreme braking loads (meaning extreme energy conversion/transfer) as drilled holes however do. The outer opening of every single hole in a drilled rotor is a potential failure trigger.

That said I don't believe drilled rotors reduce the heat transfer in any appreciable way that really matters in a non-racing situation. You can have the biggest, phattest, sexiest brakes possible and if the components can't dissipate the heat, they won't work any better. ie. no additional deceleration of the mass of the vehicle can be obtained.

On a related note this is why using 105 series pads with 80 series later front calipers does work, but only up to a point. Bigger contact area produces more heat for the same amount of pedal force, so under heavy sustained braking conditions there's not much tangible benefit as the extra heat still has to transfer out through the same amount of brake rotor metal, hub/spindle metal, CV joint, driveshaft, axle housing, etc.

Drilled rotors are basically a compromise of maybe slightly improved hard braking at the expense of higher risk of failure. Otherwise Toyota would have been fitting drilled rotors to their larger vehicles straight from the factory quite aside from the fact that drilled rotors probably are a lot more expensive to produce with an acceptable enough defect rate because of the drilling requirements.

Note all of this is my personal opinion.

 

[MoJ]

It’s a proven fact that cross drilled rotors will result in a significant 27% reduction in stopping distance. However, in order to achieve this level of improvement, it’s critical that you also have nearly pure nitrogen in the tires.

I’ll guess an appreciable portion of those noticing an improvement when switching to cross drilled rotors also serviced the rest of their braking system when they installed the rotors.

 

[greentruck]

Saw this thread revival after I got my new Tire Rack catalog in the mail yesterday. They carry the DBA "4x4 Survival Series T3" rotors, which have merited some positive comments here. That DBA stands for "Disc Brake Australia" so I suspect they have some experience with fitting Land Cruisers used under tough conditions. I just redid things up front with NAPA, so won't be needing more anytime soon (knock on wood), but these seem to be worthy of consideration. Not cheap, as was mentioned, but the quality seems to be there.

 

[sunrk]

It’s a proven fact that cross drilled rotors will result in a significant 27% reduction in stopping distance. However, in order to achieve this level of improvement, it’s critical that you also have nearly pure nitrogen in the tires.

Ah the pure peddlement of snake-oil! A 'proven fact'? Where is the actual scientific data? Pure nitrogen in tyres? Air is already 80 percent nitrogen, so how does 'deleting' the 20 pct oxygen and minimal portion of other gases make any difference?

 

[sunrk]

That DBA stands for "Disc Brake Australia"

DBA are the 'cheap' brand of Chinese made brake rotor castings. RDA is better (RDA is associated with EBC that makes brake pads). I don't know if Brembo (better quality again) make brake rotors for landcruisers. Toyota OEM rotors (sorry they're not drilled or slotted for 80's) are better again quality-wise.

 

[Red Merle]

Interesting discussion. I put the PowerStops on when I re-did the entire braking system and I have no issues to report in 17,000 miles. My pads still look fine on all four corners. I did delete the LSPV and the ABS and I also drive like an old duffer and just sort tool around my mostly rural area. Not a lot of serious braking going on here, but they have held up fine so far. The truck seems to have excellent braking, but again, I don't stress test it all that much.

Hopefully these and my Napa Eclipse calipers hold up as well as I was hoping before both started having reported issues. Other than the lines, my stuff is all aftermarket now when it comes to brake components and I think just redoing everything probably helped me avoid some of the other issues people are having.

Just my two cents, for reference.

EDIT: I do still have the original rear rotors that the truck came with. Pretty sure they are OEM. Forgot about that, but there hasn't been a reason to install new ones yet.

 

[george_tlc]

Ah the pure peddlement of snake-oil! A 'proven fact'? Where is the actual scientific data? Pure nitrogen in tyres? Air is already 80 percent nitrogen, so how does 'deleting' the 20 pct oxygen and minimal portion of other gases make any difference?

You're from oz and can't tell when someone is making a joke. Please don't embarrass me...



cheers,
george.

 

[retrofive]

deleted

 

[Corbet]

Tracking number on public forum?

Oops. Wrong thread. Posting from phone sucks. Please delete post above.

 

[retrofive]

Oops. Wrong thread. Posting from phone sucks. Please delete post above.

Thought may have been a booboo

 

[Jim_Chow]

When people change out the rotor they usually change out the pads, bleed the brakes and maybe other things too.

Did you change ONLY the rotor and felt significant performance improvement from just the rotors?

FWIW, I replaced the OEM rotors/pads in my LS430 with Stoptech cross-drilled/slotted in front and slotted in rear along with Porterfield R4s street perf carbon/kevlar pads, properly bedded and cooled them. The OEM braking was already very good, but now they are phenomenal, far better than OEM. A month later, I installed SS stoptech hoses and flushed the brake fluid (didn’t notice any difference other than pedal feel is a bit firmer). The front rotors and caliper are much larger than on the LX (also running R4s pads) with slotted rotors….debating about changing the rotors to Stoptech drilled/slotted in front but they have a lot of life left (cryo frozen) even after 160k miles over 18 yrs. Plus the 100 series rotors are kind of small (used to the 380mm brembos on my RCF)…would most likely go slots again