Rainy day rotors
 

Do drilled or slotted rotors help with wet weather braking? I usually ride my brakes prior to hard braking and every once in a while just cruising along as is. It's a little distracting but beats mashing the brakes and having nothing happen for a few seconds. Most of my road going play time in the summer varies between damp and wet roads.

What are you doing where nothing happens for a few seconds? I don’t think rotors will help you, but you need to make sure your brake fluid is in good condition and your brakes are bled properly. If you need improved braking performance try better brake pad compounds.

What brake pads are you using right now?

Vacuum mode to the seat engages when nothing happens...lol. I mash the brakes harder until they grab. Usually I pre-emptively ride them to dry them off. Only happens in certain spots where road is covered in standing water or pooled up in the frost heaves. Pads are stock performance package. Brakes are amazing to me when its dry out.

You could be hydroplaning a bit, what tires are you driving in pools of water?

Definitely can be improved by better pads and also potentially better tires. Leonardo might be onto something with the hydroplaning aspect. Is anything else affected in the wet, or just braking? What tires do you have

i've never noticed any significant difference in braking application from dry to wet--still running the oem solid rotors/pads currently. for my use, the only reason i want to upgrade is aesthetics.

there's some theory that slotted rotors wipe the pad for a constantly fresh pad material, and many people use this for more consistent braking performance contrasted to solid rotors that can glaze the pad. but if the pad is saturated with water, a new, but still wet part of the pad isn't going to make it any different.

but drilled rotors are a waste of money in all but the most tangential extreme circumstances. the theory when the pads/rotors are super heated, gases are created between the pad and rotor, and it can prevent the pad from making contact with the rotor. the theory is that the drilled holes allow those gasses to escape, allowing the pad to make contact and stop the car. the reality of this is the gases are only created at temperatures that would boil oem-spec brake fluid, so by that point, you've already at least upgraded to better quality pads and fluids, but realistically, would understand the more extreme braking requirements of the situation would require an entire braking system upgrade with larger calipers, rotors, stainless lines, different fluid, etc..

The best solution would be to have a set of wet weather rotors and dry weather rotors.

i prefer to have a wet weather car, and a dry weather car.

i'm hoping to progress to one car per day, with some extra allotments for wet/dry days.

Seriously*, if you are going to that much trouble, you really should have a cloudy day car too.






*I'm not sure if that is irony or not.

It hydroplanes in a few spots. I'm pretty used to that. Definately the brakes, not tires. 90% tread, pilot sport as3+. I have a similar issue right after leaving a car wash. I have a good habit of tapping/ riding brakes so I suppose I'll just keep doing that.

I'll send another email to my parts supplier and see if they get back to me this time. Pads...Mmmmk. Thanks folks.

This thread has me going :iono:

Drilled and slotted rotors are unnecessary. Wet or dry you have more braking power then traction. Never a reason to ride your brakes.

Drill slotted rotors do the same exact function as a solid rotor. Only slightly less surface area.

In wet conditions it's null. Due to simple centrifugal force.

Like others said, get better pads

You guys are great! Thank you all!

Based on responses here, I'm going to give drilled rotors a try. Ill log data brake pressure vs wheel speed before and after rotor install if anyone is interested. Thanks again!

stock wet
 

time brake psi wheel slip wheel speeds

6.316 0 159.5 255 22.6 0.62 22.4 22.5 22.6 22.6
6.349 0 159.5 255 22.4 -0.16 22.4 22.5 22.6 22.6
6.379 0 188.5 255 22.4 -0.16 22.3 22.3 22.3 22.3
6.41 0 232.1 255 22.4 0.7 22.2 22.2 22.3 22.4
6.441 0 232.1 255 22.4 0.63 22.2 22.2 22.3 22.4
6.475 0 304.6 255 22.2 0.63 22 22 22.2 22.1
6.505 0 362.6 255 22.2 0.48 21.7 21.7 21.8 21.8
6.536 0 362.6 255 21.7 0.89 21.7 21.7 21.8 21.8
6.565 0 406.1 255 21.7 0.89 21.6 21.3 21.7 21.6
6.596 0 406.1 255 21.7 1.22 21.6 21.3 21.7 21.6
6.627 0 449.6 255 21.3 1.22 21.4 21 21.5 21.4
6.656 0 507.6 255 21.3 1.41 21 20.4 21 21
6.689 0 507.6 255 20.9 0.17 21 20.4 21 21
6.72 0 536.6 255 20.9 0.17 20.6 20.4 20.5 20.6
6.755 0 536.6 255 20.5 0 20.6 20.4 20.5 20.6
6.785 0 551.1 255 20.5 0.52 20.4 20.2 20.3 20.3
6.816 0 580.2 255 20.1 0.52 20.1 19.8 20 20
6.849 0 580.2 255 20.1 0.89 20.1 19.8 20 20
6.882 0 580.2 255 19.5 0.89 19.5 19.2 19.5 19.5
6.914 0 594.7 255 19.5 1.01 18.9 18.7 19.1 18.9
6.947 0 594.7 255 18.9 1.58 18.9 18.7 19.1 18.9
6.979 0 609.2 255 18.9 1.58 18.5 18.3 18.7 18.6
7.011 0 623.7 255 18.5 1.23 18.2 18.2 18.4 18.4
7.043 0 623.7 255 18.5 1.07 18.2 18.2 18.4 18.4
7.076 0 638.2 255 17.9 1.07 17.8 17.5 17.9 17.8
7.106 0 638.2 255 17.9 1.01 17.1 17 17.3 17.2
7.138 0 638.2 255 17.3 1.04 17.1 17 17.3 17.2
7.169 0 638.2 255 17.3 1.04 16.7 16.6 16.9 16.8
7.201 0 638.2 255 16.5 0.74 16.7 16.6 16.9 16.8
7.234 0 638.2 255 16.5 0.33 16.3 16.3 16.5 16.4
7.264 0 638.2 255 15.9 0.33 15.9 15.7 16 15.7
7.297 0 638.2 255 15.9 0.34 15.9 15.7 16 15.7
7.327 0 652.7 255 15.3 0.34 15.4 15 15.4 15.2
7.357 0 652.7 255 15.3 1.17 14.9 14.6 15 14.8
7.386 0 652.7 255 14.8 0.6 14.9 14.6 15 14.8
7.415 0 652.7 255 14.8 0.6 14.5 14.5 14.6 14.5
7.445 0 652.7 255 14.2 0.25 14.5 14.5 14.6 14.5
7.476 0 667.2 255 14.2 0.25 14 13.8 14 13.9
7.505 0 667.2 255 13.4 0.13 13.4 13.3 13.4 13.3
7.536 0 667.2 255 13.4 1.74 13.4 13.3 13.4 13.3
7.565 0 667.2 255 12.8 1.74 12.8 12.8 13.1 12.9
7.597 0 667.2 255 12.8 1.53 12.8 12.8 13.1 12.9
7.626 0 667.2 255 12.1 1.53 12.4 12.3 12.6 12.5
7.659 0 667.2 255 12.1 0 11.9 11.9 12 11.8
7.689 0 667.2 255 11.5 -0.77 11.9 11.9 12 11.8
7.719 0 667.2 255 11.5 -0.77 11.4 11.3 11.4 11.1
7.748 0 667.2 255 11.5 0.32 11.4 11.3 11.4 11.1
7.779 0 667.2 255 10.9 0.32 10.9 10.8 11 10.8
7.809 0 667.2 255 10.9 0.5 10.5 10.4 10.6 10.4
7.841 0 667.2 255 10.1 -3.93 10.5 10.4 10.6 10.4
7.876 0 652.7 255 10.1 -3.93 10.2 10.2 9.8 9.8
7.905 0 652.7 255 9.5 0.37 9.3 9.2 9.4 9.2
7.935 0 652.7 255 9.5 1.96 9.3 9.2 9.4 9.2
7.967 0 652.7 255 8.9 1.96 8.7 8.7 9 8.8
7.999 0 652.7 255 8.9 3.12 8.7 8.7 9 8.8
8.029 0 638.2 255 8.2 3.12 8.1 8.1 8.4 8.3
8.058 0 638.2 255 8.2 6.65 7.2 7 7.7 7.5
8.087 0 638.2 255 7.4 0.25 7.2 7 7.7 7.5
8.119 0 623.7 255 7.4 0.25 7 6.9 7.1 6.9
8.149 0 623.7 255 6.6 -0.79 7 6.9 7.1 6.9
8.18 0 623.7 255 6.6 -0.79 6.7 6.6 6.6 6.5

stock dry
 

time brake psi slip wheel speeds




17.714 0 0 255 21.8 0.56 21.6 21.6 21.9 21.9
17.745 0 87 255 21.8 0.56 21.6 21.7 21.7 21.8
17.776 0 116 255 21.4 0.48 21.4 21.6 21.6 21.6
17.81 0 116 255 21.4 0.9 21.4 21.6 21.6 21.6
17.841 0 217.6 255 21.4 0.9 21.1 21 21.2 21.2
17.87 0 304.6 255 21 2.36 20.2 20.2 20.8 20.6
17.9 0 304.6 255 21 2.71 20.2 20.2 20.8 20.6
17.93 0 420.6 255 20.3 2.71 19.4 19.3 19.9 19.9
17.962 0 420.6 255 20.3 2.17 19.4 19.3 19.9 19.9
17.994 0 449.6 255 19.3 2.17 19 18.8 19.4 19.2
18.026 0 507.6 255 19.3 1.68 18.5 18.2 18.8 18.5
18.059 0 507.6 255 18.1 2.26 18.5 18.2 18.8 18.5
18.091 0 536.6 255 18.1 2.26 17.6 17 17.9 17.6
18.121 0 580.2 255 17 3.46 16.3 15.8 16.8 16.4
18.153 0 580.2 255 17 5.63 16.3 15.8 16.8 16.4
18.186 0 609.2 255 15.8 5.63 15.1 14.7 16 15.6
18.219 0 609.2 255 15.8 12.46 15.1 14.7 16 15.6
18.251 0 623.7 255 14.7 12.07 13.8 12.9 15.5 15
18.281 0 652.7 255 14.7 12.07 13 10.9 14.4 12.7
18.314 0 652.7 255 13.2 5.66 13 10.9 14.4 12.7
18.348 0 696.2 255 13.2 5.66 11.3 13.7 13.2 13.2
18.379 0 681.7 255 12.7 17.66 7.9 12.9 12.4 12.9
18.411 0 681.7 255 12.7 23.31 7.9 12.9 12.4 12.9
18.444 0 638.2 255 11.9 23.31 8.1 10.6 12.3 12.1
18.474 0 652.7 255 11.9 -4.42 11.7 11.2 11.5 10.4
18.507 0 652.7 255 11 2.68 11.7 11.2 11.5 10.4
18.538 0 609.2 255 11 2.68 9.7 10.5 10.6 10.2
18.57 0 580.2 255 10.1 9.96 8.5 9.1 10.1 9.5
18.602 0 580.2 255 10.1 0 8.5 9.1 10.1 9.5
18.632 0 594.7 255 8.8 0 9.6 8.6 9.3 8.9
18.66 0 594.7 255 8.8 5.57 9.6 8.6 9.3 8.9
18.691 0 580.2 255 7.9 5.57 8.1 7.2 8.5 7.8
18.721 0 507.6 255 7.9 13.9 7.1 6 7.9 7.4
18.754 0 507.6 255 7.5 2.39 7.1 6 7.9 7.4
18.784 0 435.1 255 7.5 2.39 7 7.3 7.4 7.2
18.816 0 435.1 255 7 2 7 7.3 7.4 7.2
18.85 0 348.1 255 7 0.27 6.8 6.9 7 7
18.882 0 232.1 255 6.5 0.27 6.4 6.5 6.5 6.5
18.913 0 232.1 255 6.5 1.15 6.4 6.5 6.5 6.5
18.945 0 174 255 6.1 1.15 6 6 6.1 6.1

More or less proves nothing. Especially with ABS doing work for you.Your limiting factor is always going to be the available traction of your tires.

Abs wasn't coming on. I'm not trying to prove a thing to you folks. Data is data. We'll see if it changes after new rotors. All of your answers convinced me drilled rotors weren't a bad idea. I hate the way they look but who cares if they help out.

They actually are not a good idea and previous comments look like trolling to me. There is no benefit and they are prone to cracking under very hard use.

If friction of brakes is sufficient to lock brakes, it's always traction of tires that will change braking distance. And do you trust yourself being that consistent of a driver to always tresholdbrake to exact same extent/friction and press brake at exact same rate for that to not to not be variable affecting results? I'd probably would trust ABS assisted locked brakes to be more consistent/repeatable then that of braking legwork of most drivers (of course if other variables are taken care of as much as possible too, eg. ambient temps, brake temps, tire temps & wear and so on ..).
+1 to no for drilled rotors for heavy use.

I'm not trolling. I got the feeling you folks just had no idea what I'm talking about. I didn't see anyone with a similar issue. If I apply light brake pressure, brakes won't respond when soaked for a few seconds. I apply more pressure they work but not nearly as responsive as warmed up dry brakes. I'm not hard enough on my brakes to crack them. I agree that drilled rotors aren't ideal for normal use, less surface area for pads to bite on. I ended up doing some more research on some other forums and using drilled rotors isn't uncommon for wet conditions. Neither is tapping them every once in a while to keep them dry. Brembo's website specifically lists use of drilled rotors for better wet weather performance. Same with porsche and some other ones. They can't all be wrong. I figured since the performance package has larger pads and rotors, that's less psi on the disk per an amount of braking compared to non pp brakes. Sorry to anyone who got offended in internet land. I'm done with this thread so don't worry bout it.

I am referring to other people trolling you.

I've never noticed a change in braking due to weather conditions, even on track. You'd have to splash the brakes with water pretty hard to have to deal with what you are describing.

Sent from my Moto E (4) Plus using Tapatalk

I want a rainy day woman.

I would replace my pads with something fit for purpose temp and conditions wise, by conditions I mean street or track, and good tyres.

I had drilled rotors on a Skyline I purchased, they cracked up after a few track days.

Drilled rotors are more about weight saving IMO.

Solids are fine, I'm still out on wiper slots, I understand their principle but have never noticed a difference.

I need to tap dat ass every once in a while.

Why don't you just brake hard enough to slow down to the desired speed?

:slap: now, that is just waaaay too simple!

:D


humfrz

Oh, please don't go away mad.

I always tap (pump) my brakes before I apply steady pressure.

Why?

Because, back in the day, with single cylinder brake cylinders, I got used to "pumping" the brakes to get the pressure up and to make sure they still worked.

Old habits and all that. Now, about when we had mechanical brakes, :slap: shut up, humfrz, nobody wants to hear about that - :rolleyes:


humfrz

Drilled rotors mostly were thing of past, when used brake pad compounds of back then released lot of gas when overheated, which needed to escape. Drilled holes do minimal to enhancing cooling, but they do make rotors more susceptible to cracking. On track, braking you can rely on, is must. Hence i'd run from using drilled ones, which imho belong only for show cars or at most for street, with light braking. In terms of reliability, blanks > slotted > drilled > slotted and drilled. About the only change that one may find positive from non blanks, a bit different pad bite due more leading edge on rotor surface. Not much weight to be saved, not much cooling to be gained. At least not enough to justify reduction to reliability. I'd probably won't go futher then using quality slotted rotors.
As for wet trackdays in rain .. been at such too, see it no way as justifying reason for rotor swap to drilled ones. Braking was fine everywhere. If any water splashes .. never felt any impact from that, probably because water evaporates almost right away from hot brakes. Only (short/initial braking) time i felt a bit impact from water on braking was when i pressure washed car, including wheels/brakes to clean of brake dust, and slowly drove off. Again few sec with pressed brakes while driving, "fixed that". If anything, imho splashed water on gloving hot drilled rotors, may potentially even further increase chance for them to crack, due quick thermal expansion/shrinking.

Back several years I was doing telemetry for a turn left team. Much testing for best rotor and pads. Nothing to show advantage of either slots or holes.
That said the op had to be talking about street use. Testing for street is usually seat of the pants, No way to replicate all conditions, so anything is possible. Or it is in a lab by some manufacturer, ie slanted.
Humfrz I too have the old habit on the street, just incase we had nothing there. I also think it may be related to old drum brakes with out auto adjusters. A long push to get them to grab, too lazy to get under to adjust them in the rain.

I ended up ordering a set of DBA rotors. I've steered clear of any rotors with holes or slots for years for same reasons as you are advising against them. Less surface area, chance of cracking, and because they look like a ricey gimmick (no offense if you have em.) I'm not racing on these brakes, just enjoying my local roads. When I say they don't respond when its wet, I really mean it. Sometimes its not multiple seconds but depending on the situation, even a 1/2 second can scare the crap out of me. Enough so that I tap them every once in a while when its raining out as a pre-emptive measure or start braking early to dry them off. If it was just corners or stop signs to worry about, I would leave them as-is. Wildlife is my major concern. I've seen bears, a few deer, 1 moose (basically a big-foot sighting where I'm at.) But the worst for me are porcupines both dead and alive. I want my brakes to work immediately when I need them. There's more rain than sun here. There's not many spots of large areas of standing water but tons of little pools from frost heaves, potholes, and the lengthwise "ruts" from other cars. I hope they work. I doubt that having holes to allow steam to escape or a non-flat surface that should break up the water film will hurt performance too much.

New pads and turned or new rotors.

Bed them in correctly.

Flush brake fluid too.

I've tapped my brakes just before my braking point, just prior to T1 at Eastern Creek, fastest corner at the track, I went through one time and when I hit the brakes, nothing happened, I almost crashed bad, from that little trip I always make sure I have pedal before I really, really need it.

My theory:
It's the PP Brembos… They're great, but the the fixed caliper holds the pads nearly perfectly parallel with rotors at all times. When there's a lot of water, there becomes a thin uniform film between pads and rotors that isn't easily displaced with pressure. You press on the brake pedal and get very little response for a very short but very noticeable amount of time.

Sliding calipers will have the pads a bit cocked relative to the rotors, so there's a wedge of water that is easily immediately squeezed out with pressure applied.

I got this phenomenon in a big way on my FD with ST40 Stoptechs. And now I get it with my BRZ PP. Particularly when exiting the carwash! Rotors have to be "cleared" of water before the brakes operate normally.

Very noticeable, very real phenomenon.

Whew..So I'm not the only one. Thanks Zdan.

I'm not sure why you insisted on ignoring my excellent advice which directly addressed your question. I wasn't trolling. You should investigate different pad compounds. The pad compound that came with your PP Brembos may not be adequate for your purposes. Simple as that. For a primarily street driven car you might start looking at something like the Carbotech 1521 or the EBC RedStuff. There's a large breadth of different compounds which are more aggressive but streetable you could try.

I'm not convinced that a different compound would clear the water off any faster. The brakes are outstanding when dry. I may eventually do pads as well but I'm pretty convinced that drilled rotors will make more of a difference. Thank you for your input.

For a street-driven car, the factory pads are fine. Any pad would exhibit the same behavior, as I'm pretty sure it's down a thin uniform layer of water between pads and rotor. Pad compound shouldn't matter at all in that case.

I bought it new. 5800 miles on it.