MG Sports Cars

I have collected a 5.0 motor and T5 tranny and continue to update my 80 B for its V8 transplant. I am going through the brakes. I added EBC Green ceramic TR8 brake pads to the front. Noticed that one rotor is a little grooved. Rather than turning it, I thought might just upgrade to slotted rotors. then I began to see comments that they are just for show and weaken the rotor as well as drastically reduce pad life.

would love to get some opinions from those running them and those that decided not to.

From my experience the only advantage to cross drilled rotors is appearance.
In use they are noisy and if carelessly done will actually whine like a siren.
They also tend to crack around the holes after several heavy heat cycles.
Some customers have also complained of increased pedal effort.
I can't say that I have noticed that, but then I don't run them on my personal cars.
Slotted rotors have the same pseudo racer look along with a slight braking advantage.
On the down side they wear the pads at a significantly higher rate.
And over here on the wet coast the slots tend to rust up to the point of protruding from the rotor surface and cause very rapid pad wear.
For my own vehicles I use a good quality conventional vented rotor. Size them according to the vehicle and it's use. (bigger is not necessarily better and is often slower) and live happily ever after.
Cheers
Fred

When I first built my car, I put great care into drilling a nice precise pattern into a new set of rotors. My motorcycle had drilled rotors. It seemed like a nifty idea, and it didn't cost me anything but time. As I recall I used three different sized holes - probably 1/4", 5/16", and 3/8" - in a three ring pattern, with all of the holes lightly chamfered. It was literally years before they started cracking. Over ten years. The cracks were very small when I spotted them. I put regular (undrilled) MGB rotors on, and was surprised just how much quieter they were. I don't think braking effect changed significantly.

But now I've upgraded to a Wilwood big brake kit.

My T-Bucket had Wilwood drilled rotors on the back, they whistled a bit but the exhaust was so loud I rarely noticed, but in a MG I think it would be noticeable. I didn't notice any appreciable breaking difference, but I do like the Wilwood big brake setup.


Paul

On my TR6, I have dotted and slotted (not drilled) discs/rotors. Didn't notice any change in noise, or braking, and the pads haven't been in there long enough to assess wear.

The purpose of drilling/dotting/slotting is to break the gas pad that can develop between the disc and the pad due to the binding agent in the pad melting and subliming off. This is what causes 'brake fade'. The spiral slots are also a cooling aid.

In everyday driving, one is unlikely to encounter brake fade. Track days, or Pikes Peak, that's another matter. But for normal road use, I would have to agree it's probably more a matter of cosmetics.

The main problem I've had with brakes is modern asbestos-free materials that just don't grip.

Ivor

Lots of myths about drill rotors.
Never drill your own, there is a process that goes into drill rotors at the manufacturer to avoid cracking.

The holes in the rotor are to help gasses escape, for quicker cooling and also to reduce unsprung weight in the front suspension.

Groove rotors are also an alternative or both. Yes they will make noise due to air escaping with is a good sign that they are doing what they suppose to do.

Many factory performance cars come with drill rotors such a Corvette Z-51 package which includes calipers and suspension mods.
Ferrari, Lamborghini, Alfa, Camero, with optional package, Mustangs with optional package and many more.
There is also carbon rotors which are cross drill. Corvette ZR 1 uses carbon rotors.

Now for looks, looks are copied when they see a race car with cross drill rotors and put them on just for looks on their street car without knowing what they original intended purpose of the cross drill rotor really is.
So...the expression was born, "They are just for looks" but not really.

Bottom line, they will help prevent brake fade.

True, myths about brake rotors are myriad.
If you feel that you must have a cross drilled rotor. Then get ones that are as cast, with the holes in place.
Actual cross drilled rotors WILL fail. It's just a matter of time.
Normal street driving probably won't harm a good set but some time on the track will.
I fill my scrap metal bins regularly with cracked and warped rotors.
If you poll the OEM's they will tell you that their holed rotors are supplied due to public demand. They have no performance advantage. Ferrari, in particular, has stated that it's an "image issue".
From an engineering standpoint cross drilling or slotting lessens the brakepad contact area.
This reduces braking ability unless the size of the contact patch is increased.
This reduced contact area also has a more insidious result.
The only avenue that the pad has available for cooling is through contact with the rotor, and to a lesser degree through the caliper piston/s.
Drilling or slotting reduces heat transfer from the pad and causes the pad to over heat much sooner.
It's actually the pad over heating and mechanically breaking down that causes dynamic brake fade.
Not the rotor getting too hot.
The rotor will sustain a much more severe heat load than the pad ever will.
The overheated brake pad will also transfer some heat into the caliper causing the brake fluid to boil.
This compounds the fade problem with a hydraulic failure or a fluid vapor lock.
This is why you're starting to see cooling fins making a comeback on high end OEM brake pads these days.
Off gassing of the pads also gets brought up often.
This hasn't been an issue since the sixties.
Well cured quality brake pads don't give off gasses under their designed use parameters.
Badly overheated pads will of course give off gasses because they are on fire, and once scorched, they are just junk.
Pad selection and brake sizing for the intended use is a much more effective route to better braking.
Braking is the most important function that your car possesses.
So make it the most high performance aspect of your vehicle.
You can always go fast, you don't get that many opportunities to stop.
Cheers
Fred

Quote:

From an engineering standpoint cross drilling or slotting lessens the brakepad contact area.
This reduces braking ability unless the size of the contact patch is increased.

Thanks, Fred. That is the point I wanted to bring up. Most don't even consider this one.

I appreciated the comment about transferring heat into the pistons. This gets very little attention. Anyway my opinion is that the more heat you can take away from the rotors and the faster you can do it, the longer your brakes will last in general. May mean bigger brakes, but these days you can go bigger and lighter at the same time, and for not much more than a quality brake rebuild with the best pads, to me a win/win.

Jim

Yes, the holes take away contact area, reason why larger rotors are used.
Every change is a domino effect.

Mmmmm new Ferraris still have drill rotors same with Lambos and Corvettes, I guess is all cosmetic stuff.

This subject can go on for ever and everyone will be right LOL

Just put what you like, if you keep reading this stuff in the end you will be confuse.

I was talking to a Wilwood engineer just about the same subject, he just laugh and said YES everyone has his own believes.

On both forums there is a negativity about aftermarket brakes why?? who knows.
Sanction race classes such as the new Pirelli series allow and suggest to change front brakes, shocks, springs, wheel and tires, with a seal engine. Honda Civic si, Mazda and others.
I just wonder why the front brakes Mmmmm.
Everyone has their won believes and that is ok.

I put big brakes on my car. Not only do I stop better, I smell better, women find me more attractive, and for the first time in years, I can solve complex calculus problems. That's what I believe, anyway.

After I put big brakes on my MGB I began having very pleasant erotic dreams. Who knew?

Jim

I'm just wondering how I managed to get by on stone-stock brakes & 20 year old pads all these years!

Carl,

I too, have lived with smaller brakes for years.
They aren't as small as some, but apparently not as big as others that I have seen in magazines.
But with the continued support of the lovely Lynne and some professional help.
I am able to live a productive life.

Cheers
Fred

Carl, slow car!!!! LOL

Dan, you stop better??? You have big shoes ??? you mean the GT stops better. :-)

Fred, most would agree that I need professional help, too. I have been certifiable for many, many years. ;)

Did Bill actually say s-l-o-w? Good thing he's so far from East TN. :)

Not trying to argue the point, everyone has their own....believes right?

Brakes to me it is like car insurance, you pick what you think is the best for you, never collect from them until the day you need them.
Here again some just get enough insurance to meet the state requirements like in Ca. and it is adequate, until the day you needed and wish you had better insurance, but it was adequate at the time.

I do not like adequate, as mention before, changes bring a domino effect so I move forward accordingly.

I am not saying that stock MGB brakes are bad, not at all.
What is amazing to me is the talk about high tech engine in the B, king pin suspension is old, FI is the only way to go, V8 is the only way to go etc....and then old design brakes are ok and new brake technology (design) is for show only. New calipers are good looking, but the also work.
Granted that drill rotors and groove rotors and new calipers may be a bit much for the street, but if track days are done with the same street car, you have a problem with the stock brakes, now you are going faster than the 4 banger could, then the stock brakes are adequate.
How about panic stops? shorter braking distances, here again some use just adequate tires, see the picture.
It is like some who spend lots of $$$$ in a restoration and never clean the tank, yes it is adequate.

I am not saying that what you have is not good, it is just adequate.

Bill,

Nobody said that you shouldn't improve your brake system.
Quite the opposite.
Braking is a critical component and should not be ignored.
The argument is about drilling and slotting rotors.
This has become vintage technology. Much better remedies for inadequate braking are available these days.
Sizing braking systems correctly and using quality parts is what it's all about.
Lightweight multi piston calipers, bigger rotors, high tech pads, improved flex lines etc. All add up to an improved system with good looks to boot.
Every vehicle has unique requirements so a blanket statement that the biggest baddest brakes that will fit, just won't fly.
Brakes can be made too big for the vehicle.
Centrifugal force and the increased drag from an oversized rotor will slow an otherwise good car down.
Excessively oversized brakes can overload the suspension with unsprung weight.
And make the vehicle much more difficult to stop because you have now overpowered the tire.
Brake pedal modulation becomes impossible because the brakes no longer produce enough heat to work properly.
It all looks cool but it's not really drive-able.
I enjoy all the new technology and utilize what works at every opportunity.
However, following the herd mindlessly is just not something that I do well.

Cheers
Fred

Thanks for your posts Bill. I've only been doing this, designing brake systems and racing, for 40 years but you're 100% correct on all points.
Whoever posted "If you poll the OEM's they will tell you that their holed rotors are supplied due to public demand. They have no performance advantage." Thanks for the laugh. I almost blew my evening cocktail out my nose. Seriously, post only about things that you know about. Thanks.

Me neither Fred, I do not follow anyone.
Yes you are correct, could not agree more with you. The big problem with the tech brake of today is not producing enough heat because they are to big, so....true

The news of today is smaller and thicker and the new liquid cool calipers, not for the street of course.

Just like putting the biggest tires that will fit in the a small car and run to temperature, that does not fly either.

I have a neighbor who is an engineer for a F 1 team here in town, the name of the team is a secret.
He gave me this rotor which is about 5 year old tech. It is super light and hard, the wheel is design to push air to the rotor, reason why the cooling holes are at an angle. I do pick his brain when possible.

I think we both are in agreement, I perhaps misread/misunderstood what was writing. Every component has its place.
I love my 12.19"rotors with uneven piston sizes and AAA tires I can stop and apply as much pedal as needed, it is an awesome feeling.

Excellent brakes with a good suspension set up, it is the best feeling. In the street the best insurance when combine with good defensive driving. I like my big brakes.

Carl still slow with the that Buick LOL





Edited 1 time(s). Last edit at 03/04/2014 09:30PM by classic conversions.