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Schuylkill Trail Bum
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Discussion Starter · #1 ·
I'm going to be replacing the brake rotors on my 2007 GTI.

I have 18 inch performance tires, a 6-spd manual, and I drive pretty aggressively, or sportily might be a better word.

So I'm looking at various brake rotors online and I'm going to be choosing between:

- Solid rotors (VW stock, which I have now)

- Slotted rotors

- Slotted and drilled rotors.

I've read the descriptions of each and have a pretty good idea about the engineering behind the different types. What I lack is real world experience.

Have any of you used slotted or slotted and drilled rotors? Pros? Cons?


Thanks
 

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half-fast
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I looked into this for a car I had a while back. The forum I watched at the time said two things.

Don't do it.
Really. Don't.

If the rotors aren't forged, they are going to crack. This is not good.

I think the general consensus was to buy the sport brake pads and don't be a poser raceboy. YMMV, BBQ, etc.

The sport brake pads were a good value for what they added, but the dust was absurd.
 

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I've had various GTI/Jetta GLS from Gen 1-5, currently in a 2008 R32 and I would stay with stock rotors. Any gains you get from slotted/drilled are going to be marginal and as 10ae1203 notes, pads will have a greater bang for your buck. Is it fade or general stopping power you're trying to fix? Different pads will help the former while larger diameter rotors and or different calipers will fix both although at more expense and complication.
 

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Way back when I used to wrench on race cars we would avoid using either slotted and especially cross-drilled rotors unless we needed to solve a specific problem as solid vented rotors always performed better. If the track layout was going to work the brakes in an unusual manner, like a high speed section to a hairpin followed by a long slow section that would heat the brakes and not allow them to cool immediately, usually required slotted or drilled rotors to deal with the pad glazing that would start to form. Reducing the rotor mass from slotting or drilling causes the brakes to heat up more due to the loss of thermal mass, the loss of surface area would lengthen braking enough that the drivers needed to know we put the rotors on. And cross-drilling really increases the chance of cracking. Not fun to have a chunk of a rotor come out when you hit the brakes at 230 mph. Both slotting and cross-drilling will chew-up the brake pads much faster.

I never run slotted or cross-drilled rotors on the street unless I don't have a choice. (Certain German marques only offer slotted rotors for some models.) The same with braided steel brake lines. There is really no need for them, the additional cost is just for the bling and showing those who really know what is going on that you don't.

That said, I did run ATE PremiumOne rotors on my old Mk2 GLI. That car had the worst issue with "wet" brakes of any car I ever owned. It was bad enough that my wife would use my POS car that leaked onto driver whenever it rained. Changing to the mildly slotted rotors solved the wet brake problem. It still remains the only time I'd ever put slotted rotors on a street car, and again it was only to solve a specific problem.

If you are looking to improve your brakes slotted or cross-drilled rotors is taking you the wrong way.
 

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Generally I'd say if the stock pads and rotors worked fine replace with the same. Using different rotors or pads may cause undesirable braking, wear, or noise.
 

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Schuylkill Trail Bum
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Discussion Starter · #6 ·
Thanks all.

That's exactly the advice I was looking for.

I have no problems with the stock rotors and pads under any circumstance I've encountered driving the GTI for 10 years.

The only reason I was thinking about replacing the rotor is that the guy who did my last state inspection said I'd need rotors for the next inspection.
 

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I'm going to be replacing the brake rotors on my 2007 GTI.

I have 18 inch performance tires, a 6-spd manual, and I drive pretty aggressively, or sportily might be a better word.

So I'm looking at various brake rotors online and I'm going to be choosing between:

- Solid rotors (VW stock, which I have now)

- Slotted rotors

- Slotted and drilled rotors.

I've read the descriptions of each and have a pretty good idea about the engineering behind the different types. What I lack is real world experience.

Have any of you used slotted or slotted and drilled rotors? Pros? Cons?


Thanks
I use the cheapest vented rotors I can find in my race car - $8 each from Rock Auto.

That should tell you something.

If you're looking for improved braking performance, replace your pads.


Sent from my iPhone using Tapatalk
 

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Depends on how well the car is spec'd from the factory. On my Nissan, crap rotors came standard and they tend to warp easily (and they did). I ended up going with a oem bbk and drilled and slotted aftermarket rotors. I don't often drive aggressively, but the times that I do, the brakes don't give me any problems. Brakes aren't something I wouldn't cheap out on if I can afford it. And if you plan of upgrading rims/wheels, go with plated rotors if whatever you are leaning towards aren't.

Drilled rotors are usually fine for street use as long as you're not beating on them and they get too hot (like on a track).
 

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I have slotted rotors on my car and they have about 40K miles on them.

Front slotted rotors: Brembo
Rear slotted rotors: Stoptech
Brake Pads: Hawk
 

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Someone above made a nice post. I'll add the only real reason to replace your rotors with lighter ones is to reduce unsprung weight. Maybe if you pickup 2 piece ones that will also help reduce warping. My C63 had slotted drilled fronts, and slotted rears. I tracked my car and never had any issues except needing new pads every year and tires every 6 months :)
 

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I use the cheapest vented rotors I can find in my race car - $8 each from Rock Auto.

That should tell you something.

If you're looking for improved braking performance, replace your pads.


Sent from my iPhone using Tapatalk
I've seen cracked drilled rotors from track use, but don't know about slotted. Have you witnessed cracked rotors from slotted?
 

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The stock rotors on my Ford Focus were mediocre and pitted too easily. I ended up replacing the whole set with a Power Stop Z23 kit. They work very well in wet conditions.
 

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I'm going to be replacing the brake rotors on my 2007 GTI.

I have 18 inch performance tires, a 6-spd manual, and I drive pretty aggressively, or sportily might be a better word.

So I'm looking at various brake rotors online and I'm going to be choosing between:

- Solid rotors (VW stock, which I have now)

- Slotted rotors

- Slotted and drilled rotors.

I've read the descriptions of each and have a pretty good idea about the engineering behind the different types. What I lack is real world experience.

Have any of you used slotted or slotted and drilled rotors? Pros? Cons?


Thanks
Drilled rotors have zero advantage other than looking fancy. They are worse than blank rotors and are liable to crack.

Slotted rotors may have some minor advantage at preventing pad glazing, but such advantage is pretty minimal.

There is little reason to do anything but solid rotors for your replacement. You will never notice a difference between rotors in street driving. Pads make a much bigger difference. Get good pads that are appropriate to your application.

As an aside, "solid rotors" technically refers to unvented rotors. No modern car I'm aware of has unvented rotors. You want smooth vented rotors, like your OEM ones.
 

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Schuylkill Trail Bum
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Discussion Starter · #15 ·
Great responses.

I'm going with stock smooth vented rotors and stock pads.

I have no issues with the stock brakes.

Based on all this good advice, I don't need enhanced rotors. Stock OEM stuff will do.

Thanks all.
 

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Drilled rotors have zero advantage other than looking fancy. They are worse than blank rotors and are liable to crack.

Slotted rotors may have some minor advantage at preventing pad glazing, but such advantage is pretty minimal.

There is little reason to do anything but solid rotors for your replacement. You will never notice a difference between rotors in street driving. Pads make a much bigger difference. Get good pads that are appropriate to your application.

As an aside, "solid rotors" technically refers to unvented rotors. No modern car I'm aware of has unvented rotors. You want smooth vented rotors, like your OEM ones.
I disagree, they do provide value, but at a cost. Drilled rotors are lighter, reducing unsprung weight. However, they also don't last as long and like you said, are prone to cracking. This is fine in the racing environment where you replace the rotors after every race or every few races.

My old car came with drilled and slotted OEM rotors (AMG C63), I believe many high performance cars come with those. It depends on the size and construction. The C63 rotors were the size of most Honda wheels/tires.
 

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Great responses.

I'm going with stock smooth vented rotors and stock pads.

I have no issues with the stock brakes.

Based on all this good advice, I don't need enhanced rotors. Stock OEM stuff will do.

Thanks all.
There are some mildly upgraded brake pads that work extremely well for street use. EBC GreenStuff, Hawk HPS, StopTech Sport. Even European "stock" pads from Jurid or Pagid can make a nice mild street upgrade with longer life than the typical US spec OEM pads. Just be careful, some of these compounds can produce a ton of dust. I personally do not like the current ceramic pads (too touchy) but if you're a very light brake user you might find them okay.

I disagree, they do provide value, but at a cost. Drilled rotors are lighter, reducing unsprung weight. However, they also don't last as long and like you said, are prone to cracking. This is fine in the racing environment where you replace the rotors after every race or every few races.

My old car came with drilled and slotted OEM rotors (AMG C63), I believe many high performance cars come with those. It depends on the size and construction. The C63 rotors were the size of most Honda wheels/tires.
The primary reason cross-drilled and slotted rotors came about is that the old friction compounds would out-gas so severely when hot that you would actually get a layer of gas preventing the friction compound from touching the rotor, resulting in poor braking. Slotting and cross-drilling was done to get the gas out of there. Weight reduction was secondary by a large margin.

On the race cars we would take the cheapest cast rotors we could find, run them thru a couple of heat cycles, then turn them down to just above minimum thickness in order to reduce the unsprung weight. When the team finally moved from production based brakes to purpose built race brakes things got so much easier as the rotors were already heat-cycled and turned to minimum thickness. They were full floating rotors (fixed calipers) so only the rotor was replaced (the hat was reused.) They were actually cheaper and lasted longer than the previous production based!
 

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I disagree, they do provide value, but at a cost. Drilled rotors are lighter, reducing unsprung weight. However, they also don't last as long and like you said, are prone to cracking. This is fine in the racing environment where you replace the rotors after every race or every few races.

My old car came with drilled and slotted OEM rotors (AMG C63), I believe many high performance cars come with those. It depends on the size and construction. The C63 rotors were the size of most Honda wheels/tires.
No, not even at a cost. They do not materially decrease weight in a car rotor. If weight was the issue, you'd be better off with a smaller diameter rotor- which makes a much bigger difference on weight.

Cars like Mercedes have them because it looks fancy. Actual race cars generally don't use them. For reference, this is a Formula 1 rotor:



Cost is emphatically no object in F1, but they are using blank rotors. Drilled rotors are actually a much bigger problem in a race environment because they will see much wider heat cycles and a failure is would be catastrophic. A drilled rotor on the street will likely start showing signs of cracking before it fails.

Part of the reason you see drilled rotors in the first place is that obsolete brake pad technology produced an effect called outgassing, and the holes provided a place for the gasses to go. This is no longer an issue. Holes can also be a material weight savings when you are dealing with a much lighter vehicle like a motorcycle or bicycle where the rotor is under much less stress and the holes can be much larger.
 

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I stand corrected... also, F1 brakes are Carbon Ceramic, can't really compare them to cast rotors.

Call it what you will.. the brakes on the C63 stopped on a dime :)
 

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I stand corrected... also, F1 brakes are Carbon Ceramic, can't really compare them to cast rotors.

Call it what you will.. the brakes on the C63 stopped on a dime :)
If you want to look at race cars with cast rotors, here's a Pirelli world challenge car with just slotted:



One big misconception about brakes is that they are the limiting factor for how a car stops in a street car. Just about any modern car has enough braking power to lock all four wheels. Stopping distance is a function of tires, vehicle weight, and suspension tuning.

Fancy brakes aren't for stopping quick once or twice, they are for continuing to do so after dozens of hard stops in a row on a track.
 
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