Hi,

When weather conditions like this are bad, it's good to gently apply the brakes every so often to remove the moisture and keep the brakes 'warmer'. The advice of the same is given if your car goes through some standing water or a minor flood you need to drive through, get to a suitable distance on and apply your brakes. With constant water coming in with a lot of heavy rain, every minute or so gently apply and you'll find that in case of having to stop quicker, you won't have that feeling of nothing that you recently had.

Cheers, Dennis!

 

I'm shying away from drilled & slotted as I don't need track performance braking,

Dont assume slots plus holes = track performance

info from a guy I trust:

How to Select Brake rotors - Plain, Slotted, Drilled, Slotted & Drilled, 2-Piece Floating

I run slotted front and rear

 

Don't E39's have the rotor drying feature? I can't remember. But as others said, a good practice would be to tap the brakes every so often.

A bit more info here Brake drying feature only activates on high speed, not with rain sensor - Bimmerfest - BMW Forums

 

Don't forget to test/dry the brakes after a simple car washing. The first application will have scary poor braking distance results.

 

We don't have that on our e39's

 

+1

 

I do drilled and slotted for looks. I know it probably doesn't help braking but it looks cool


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I do drilled and slotted for looks. I know it probably doesn't help braking but it looks cool

]

Unless you are car guy..and you know the truth, then you know it isnt..

 

slots/drills explained, with water I guess it works just the same https://www.youtube.com/watch?v=3IyLVFCm1fQ

 

What sort of tires are you running? Quality tires appropriate for the driving conditions > slotted/drilled rotors IMO.

 

Thank you for the link ARD. That's exactly the info I'm looking for:

Drilled rotorsoffer slightly more bite and friction than slotted rotors. As with slotted rotors, pad coefficient of friction remains consistent over their lifetime. Wet bite is improved over plain and slotted rotors, so these may be the best choice for areas with heavy rainfall, like Seattle or Singapore. Weight is reduced by about 0.2 pounds per rotor, depending on size and drill pattern. Disadvantages include possible uneven rotor wear, typically concentric groove formation, although this is mostly an aesthetic concern. A major disadvantage is accelerated formation and spreading of cracks under racing conditions. For this reason, drilled rotors should be avoided for track cars, unless required by the rules. A common piece of misinformation is that they have lower performance than smooth rotors, due to reduced surface area and are for looks only. This is false.

 

The holes make very little difference, as do the slots. The pad you choose will make the most difference once it scrapes the rotor clean. Also, having dust shields makes a monumental difference in the wet.

I tell you this from personal experience in experimenting with this theory.

 

Mike, I assume you mean "not having" dust shields makes a monumental difference in the wet?

 

I was driving through an ice/snow storm on the PA Turnpike in my M5 with blank rotors and had to keep using my brakes every few miles because trying to stop was scary. I've put slotted rotors on my Honda Odyssey and old Honda Accord and they both made a VERY big difference in initial bite in the wet.

I will put slotted rotors on when I am ready for brakes, I just haven't needed front brakes yet since getting my M5. I like the look of cross drilled best, but don't want to worry about potential cracking if I ever take my car to the track. Zeckhausen told me not to get cross drilled if I EVER planned to take my car on a track.

 

Cross drilled rotors were initially used to allow for outgassing from race pads. It actually makes very little sense in everyday applications as you really want to maximize the braking surface. Really, xdrilled rotors are just for looks.

Slotted rotors are still mainly bling for the street and have very limited track advantages (e.g., for casual track days, HPDE), but they do allow for some channelling and minor outgassing. It's a good compromise between looks and practicality. But if you're all about braking, blanks are the way to go.

 

I was surprised by Dave Z.s content.

Id never run drilled rotors unless the car was designed with them. The theoretic advantage is far outweighed by the negatives.

But people like the look and any shred of info that supports the decision will likely be used as justification. OP likes the look and will find what he needs to justify this- despite thousands and thousands of E39 owners running plain rotors in heavy rain the world over.....

(Full disclosure- my 996TT has stock drilled rotors)

 

I was surprised by Dave Z.s content.

Id never run drilled rotors unless the car was designed with them. The theoretic advantage is far outweighed by the negatives.

But people like the look and any shred of info that supports the decision will likely be used as justification. OP likes the look and will find what he needs to justify this- despite thousands and thousands of E39 owners running plain rotors in heavy rain the world over.....

(Full disclosure- my 996TT has stock drilled rotors)

Woe. Hold on there big man. Just to clarify, I could care less about the looks. I don't want to invest 500+ in rotors if I they aren't going to do anything to improve wet weather permformance, hence asking you guys for your experience and opinion.

 

I thought brake dust shields were just excess weight :dunno:




PLEASE NOTE THAT I DO NOT OWN AN M5 AND THIS POST IS NOT INTENDED TO BE ARROGANT. PLEASE READ THE IMPORTANT REVISED DISCLAIMER THAT APPLIES TO THIS POST

 

You do, IIRC. Or just use the hard motorsport plates that bolt in w/o having to remove the entire hub

 

slotted drilled brake threads are like oil threads.....

 

:hihi::hihi:

...and in the meantime, if anyone wants full-floating (and drilled) rear rotors for their M5, don't miss the fact that the competition package E46 rear rotors from the 2005-2006 M3 fit perfectly (since the regular, one piece rear rotors are identical parts between the two cars). :checkeredflag: