Brakes: 135i vs 1series M coupè

[adc]

Originally Posted by Trier Germany

Nurburgring not hard on the brakes? Your car must have not been broken in when you did your laps? If you want to do back to back laps and you have to haul 3700lb car down from 150Mph on a couple occassions and from 100Mph triple digit speeds multiple times and you do more than 2 laps oh yah it's hard on the brakes the track is 12 miles long.

My car was fully broken in when I did my laps - the driver on the other hand probably wasn't.

But come visit my local track - the one I go to most often. Main straight allows you to do 150+ mph then you brake for a 35mph right hander, then there is another 110mph to 20mph effort very soon after that. And the whole track is 2 miles long only.

I've noticed that the car only starts having serious brake issues if you go over 130mph on the main straight, it's probably those last 10-20mph that kick the braking system into the teeth.

The recovery times on the Ring for the 150mph brake events are significantly longer than on my local track.

So why spend the extra dough on rotors when Pagid or endless work very good on our factory rotors and increase the braking performance by 50% compared to stock pads and won't melt or delaminate. Just my opinion. I also do multiple track sessions at SPA and Nurburgring GP track and the Pagids RS 19 hold up quite well my friend has endless in his coupe and they last quite a bit longer than the pagids and supply equal stopping power.

I'm perfectly willing to try better pads - and in fact I will next time around. I'm planning on using Cobalt Friction XR1 front with XR3 back (at their recommendation). I'm doing this because it's one of the 2 pad compounds used sucessfully in the GrandAm cars (production based M3 coupes) for sprint races, and because they don't require bedding in. (The other compounds are PFC01 I believe). I might look into Pagid and endless too.

And anyway next time on track I'll probably benefit from my cooling ducts as well.

But I recall another forum member saying that even with full brake cooling ducts (from the GT4), there is still some fade to be experienced on various European tracks (he may have mentioned SPA specifically). He's the one I think who posted instructions for DYI brake cooling ducts on the M3 forum (whose work I've copied for mine).


Anyway, how hard would it be for BMW to offer one or all of these as options:
- standard cooling ducts like they've had for the past 20-30 years
- approved track pads
- upgraded, track-ready brakes

[matt]

Originally Posted by adc

So at the very least, BMW should offer an M-track brake upgrade for $2-3k and probably 50% of buyers would opt for it.
BMW is missing out on opportunities to relive their customers of serious chunks of cash...

THIS!

Originally Posted by adc

Anyway, how hard would it be for BMW to offer one or all of these as options:
- standard cooling ducts like they've had for the past 20-30 years
- approved track pads
- upgraded, track-ready brakes

135i has brake ducts?
at least my 135i has cooling ducts for the brakes...

[adc]

Originally Posted by matt

135i has brake ducts?
at least my 135i has cooling ducts for the brakes...

I meant cooling ducts (from the front bumper/airdam region and opening in the wheel well) - I thought the 135i has them?

My E46 had them, the E36 before that too and even the 1990 325i had them.

[grant]

Originally Posted by KingOfJericho

Let's be honest here... what percentage of M3s do you think actually hit a track? It isn't until the car is 10 years old and becoming an inexpensive dedicated track toy that these things will matter. I bet 90% of them will never see a track in their lifetime.

Whether or not more than 10% of the cars see the track, the car should be able to run repeated laps on a challenging circuit without brake fade. Otherwise, what is the point of calling it ///M (for Motorsport)?

[Robert]

Originally Posted by grant

Whether or not more than 10% of the cars see the track, the car should be able to run repeated laps on a challenging circuit without brake fade. Otherwise, what is the point of calling it ///M (for Motorsport)?

street sport

[grant]

Originally Posted by Robert

street sport

Then that's what they should call it.

[Madozu]

If the 1M will have the M3 brakes, that should be ok for the majority of tracks, because 1M's weight will be considerably less than the current M3's weight. Combined with air ducts from the air intakes on the front to the break discs is a must ... even my 14 years old E36 M3 has it.

Real race-brakes on public roads are usually a loss of comfort and a limited brake performance if the brakes are cold ... as an option that would be ok.

A car like the 1M that is meant to be a "driving machine" should definitely come with excellent brakes that can stand say 5 fast Nürburgring Nordschleife laps without fading. In the Alps where I'm living, it's usual to drive roads that go from 8000 ft altitude down to 1000 ft. That's often hairpin-straight-hairpin style ... and an M-car should be able to do this without even a sign of brake-fading

[adc]

Originally Posted by Madozu

If the 1M will have the M3 brakes, that should be ok for the majority of tracks, because 1M's weight will be considerably less than the current M3's weight.

Well it will apparently be around 250lbs lighter. Is this a lot? I don't know...

The M3 rotors are just 14" diameter, a very small increase from the 135i's 13.7" items. The M3 calipers are downright $hitty compared to the multi-piston setup in the 135i, and the pads are no more than 60% of size of the 135i pads.

It's ok to use the M3 rotors but not the calipers.

In the Alps where I'm living, it's usual to drive roads that go from 8000 ft altitude down to 1000 ft. That's often hairpin-straight-hairpin style ... and an M-car should be able to do this without even a sign of brake-fading

Coming down the Jaufen Pass during my Euro Delivery I played tag with a very well ridden sports bike - I couldn't have done it going up because I was still in the break-in period. But downhill, the game was on. Well roughly 10 hairpins or so later my brakes started to grumble and then fade- and I was NOT pushing it all the way.

Was a little disappointed...

[Quick1 TO BE]

ADC.. ur blue M3 picture, is it turn 3 on Summit main?

Ash

[adc]

Originally Posted by Quick1 TO BE

ADC.. ur blue M3 picture, is it turn 3 on Summit main?

Ash

Hey man, no it's actually from Nurburgring - don't know precisely where on track but judging from the extreme suspension compression it must be Fuchsrohre. That is an incredible section, going flat out downhill through some esses and picking up serious speed, then resisting the urge to lift for the biggest compression you'll ever feel... Epic stuff, the Ring - I'm addicted to it and planning a return there as we speak.

[Madozu]

Originally Posted by adc

Coming down the Jaufen Pass during my Euro Delivery I played tag with a very well ridden sports bike - I couldn't have done it going up because I was still in the break-in period. But downhill, the game was on. Well roughly 10 hairpins or so later my brakes started to grumble and then fade- and I was NOT pushing it all the way.

Was a little disappointed...

Agree, this shouldn't happen ... especially because Jaufen allows the brakes to cool down a bit in the straights between the hairpins I can only imagine that either discs and pads were brand-new or that the rear brakes' effect was too low.

Let's hope they do it better for the 1M!

[Robert]

surprised bmw doesn't offer carbon fiber kit. major margin on that

[grant]

Originally Posted by Madozu

In the Alps where I'm living, it's usual to drive roads that go from 8000 ft altitude down to 1000 ft.

Excellent - the roads near me (Colorado) go from 5,000ft to over 14,000ft (highest paved road in Continental US). It takes a toll on engine and brakes for sure!

[CDR_UK]

Originally Posted by adc

The M3 rotors are just 14" diameter, a very small increase from the 135i's 13.7" items. The M3 calipers are downright $hitty compared to the multi-piston setup in the 135i, and the pads are no more than 60% of size of the 135i pads.

It's ok to use the M3 rotors but not the calipers.

Don't forget the width of the rotors which is very important for performance - do you know the widths of the M3 rotors Vs the paper thin 123i rotors?

[Evice]

Originally Posted by adc

Very much doubt that the holes have a significant cooling effect - that's not the direction of the airflow. The holes help in other areas - immediate elimination of water film in the rain and pad glazing prevention. Oh and looks.

The reasons for the soft feel after hard track use are others:
- completely inadequate brake pad material
- marginally insufficient heat transfer capacity (this could be a combination of insufficient cooling flow and/or system sizing)

Someone mentioned Endless pads - any aftermarket pads you put on will work well on some tracks and not so well on others (due to the second reason above). Nurburgring is not as hard on brakes as some of the other, shorter tracks (not sure if this is an issue with US-designed tracks or if it's true in Europe as well). So throwing $800 or $1000 or however much they cost on a set of pads that may or may not give you satisfaction is a risk.

What it actually takes is for the manufacturer to design the brakes and size them appropriately for track use given the mass & speed of the car. Porsche does this in many of their models. Then it truly becomes a case of swapping for track pads and not having the slightest worry.

Holes have significant effect on cooling as well, and they mainly do it with
1) they increase the the area of the cooling surface, doesn't matter if you pass airflow thru them or not. More area, faster cooling.
2) The holes actually help to take away the gases produced under braking. It gives gases a way to escape from the rotor and pad surface, which results in faster cooling.

In my opinion; downside of x-drilled is that they are more prone to cracking, and when the cracks start to increase in size and merge, you are done with them. It is a balance equation here.

[Madozu]

Originally Posted by grant

Excellent - the roads near me (Colorado) go from 5,000ft to over 14,000ft (highest paved road in Continental US). It takes a toll on engine and brakes for sure!

Looks as if you're talking about the Mount Evans road. I've read about it but unfortunately I've never been in the Denver area and therefore never had the chance to drive that road. I can only imagine how my NA I6 would perform at an altitude of 14k ft

Great area you're living in

[adc]

Originally Posted by CDR_UK

Don't forget the width of the rotors which is very important for performance - do you know the widths of the M3 rotors Vs the paper thin 123i rotors?

You mean the paper-thin 135i rotors? I don't think they are that thin...

But it would be interesting to compare, I agree...

[adc]

Originally Posted by Evice

Holes have significant effect on cooling as well, and they mainly do it with
1) they increase the the area of the cooling surface, doesn't matter if you pass airflow thru them or not. More area, faster cooling.

It's true the area surface increases, but you are also loosing material, thus heat soaking capacity. I'm not sure I've read anything that convinced me that they actually improve cooling.

2) The holes actually help to take away the gases produced under braking. It gives gases a way to escape from the rotor and pad surface, which results in faster cooling.

Out-gassing was a big problem with old pads, but as I understand it it's not a big problem with modern compounds. Especially with sintered pads, which have no "glue" that can evaporate.

And the out-gassing's biggest drawback wasn't cooling, but rather loss of pedal pressure & feel.


I know for sure the biggest advantage of the drilled rotors is with pad abrasion, preventing pad glazing. After a track session they are half-full of pad material (so the cooling benefits, even if present, would be greatly diminished).

[Red Bread]

135i brakes are listed as 338x26 (f) and 324x22 (r) - 13.3x1.0 (f in inches) and 12.8x0.87 (r in inches)

M3 brakes are listed as 360x30 (f) and 350x24 (r) - 14.2x1.2 (f in inches) and 13.8x0.95 (r in inches)

[adc]

Originally Posted by Red Bread

135i brakes are listed as 338x26 (f) and 324x22 (r) - 13.3x1.0 (f in inches) and 12.8x0.87 (r in inches)

M3 brakes are listed as 360x30 (f) and 350x24 (r) - 14.2x1.2 (f in inches) and 13.8x0.95 (r in inches)

Oh wow, I was always under the impression the 135i's front rotors were 13.7"...

Yes, these are significant differences - so hopefully they use the winning combination, M3 rotors with 135i calipers.

[JasonCSU]

Originally Posted by Madozu

Looks as if you're talking about the Mount Evans road. I've read about it but unfortunately I've never been in the Denver area and therefore never had the chance to drive that road. I can only imagine how my NA I6 would perform at an altitude of 14k ft

Great area you're living in

There are a lot of great roads out here, some more so for driving and others for sight seeing like Trail Ridge road. There are some incredible views from Trail Ridge, but there is also a lot of traffic and tourists. I've yet to drive Mt Evans Rd, but need to cross that off the list.

[CDR_UK]

Originally Posted by adc

Yes, these are significant differences - so hopefully they use the winning combination, M3 rotors with 135i calipers.

hopefully they will put proper brembos and not the cheap excuse that is on the 135i...