Porsche brakes
- Thread starter goon
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By the seaside...
gaffer1986
Member
I think this video was a good experiment:
https://www.youtube.com/watch?v=qkIowmqOFRg
https://www.youtube.com/watch?v=qkIowmqOFRg
BMWZ4MC said:
That's interesting, I had no idea. I do get some movement (more than the current state of the disks would suggest or the fact the balance is too strong at the rear running both Pagid RS29 front AND rear) and I do come off abruptly. Very interesting, I let the car settle first. There goes that saying "slow in fast out"! It'll help not cook my road tyres so much either.
Nice one dude!
Holy cow Exdos got a calculation wrong
That is a juicy thread. And how rude was that Smarguy gaffer1986 said:
Thought about this exact one when I saw the tread. When you look at the stopping distances it exactly shows that BBK not equal shorter distance but endurance.
I couldn't be bothered responding to a pig-ignorant troll who registered just to be abusive to me. :thumbsdown:ChawenHalo said:Holy cow Exdos got a calculation wrong
If he knew anything he would realise that the OEM single piston actually pushes against an equal and opposite force on the opposing side of the calliper, which effectively doubles the area of the single piston, otherwise the brakes wouldn't work!
exdos said:I couldn't be bothered responding to a pig-ignorant troll who registered just to be abusive to me. :thumbsdown:ChawenHalo said:Holy cow Exdos got a calculation wrong
If he knew anything he would realise that the OEM single piston actually pushes against an equal and opposite force on the opposing side of the calliper, which effectively doubles the area of the single piston, otherwise the brakes wouldn't work!
Makes sense. I remember reading years ago the advantages of single piston applications but for the life of me can't get hold of it. From memory it included weight, heat dissipation. Any ideas Exdos?
ChawenHalo said:
The advantage of the single piston calliper is that the design is simple and there is only one piston so only one seal, which provides greater reliability and less likely to leak. Most of the major manufacturers use them for this reason. Also the opposing side of the calliper bracket only needs to be rigid to support the opposing pad, so does't have the added weight of having to house a piston. Does that explain?
pokeybritches
Member
^WHS. If a single piston was better, it would be standard equipment on exotics, and there would be upgrade options utilizing a single piston.
It's a single piston due to cost.
It's a single piston due to cost.
If you have a small pad in a small a single piston caliper it'ss not that bad. The piston covers most of the pad.
But increasing pad size increases stamina, you can use different pad materials, and regulating the clamping force becomes easier/more precise under heavy load: so the point between the pad locking the brake and still rotating.
That last point is important because in the transition between locking and unlocking friction is very poor and unprecise. You can test that with for example a book that you want to drag across a desk on an elastic rope. The book stays stationary for a while (friction is high), but suddenly shoots along the elastic rope (at that time friction is low), until it is dragged on a constant speed and friction increases again. That also happens at braking.
So if you want larger pads, you want to spread the clamping force (otherwise the will bend a bit and load is only appied in the center).
Thats why supercars have big multipiston calipers (cost is less of an object and performance is a selling point)
The piston area an sich is not important at all, unless the braking pedal becomes so heavy that you cant apply enough force to block the front brakes. But that hardly happens at all with boosted brakes (unless you're very weak/old). The only thing to look out for is brake bias if you change piston diameter (or pad size or disc size for that matter). But you can also play with that using different pads front and rear. The main thing you dont want is the rear locking up before the fronts, but you can easily test that on a quiet piece of road.
So saying that a smaller total piston diameter in a multipiston caliper is worse than a larger (area) single piston caliper makes no sense. I mean: does the larger pad have to have the same clamping force? etc etc. In the end it comes down to having enough pressure to be able to lock the brakes (no problem) and the brake bias itself (which is a combination of pad material, pad size pad pressure disc size and disc construction, so something which is tested in practice and also varies greatly with surrounding circumstances. Thats why with real racecars the driver can adjust the brake bias while he's driving to adapt to the surroundings (heat, wear etc etc) )
How reliable something is (in the braking area) is probably more dependant on how hot, how dirty and how wet it gets plus the useage (and of course materials used etc). I think sticking calipers are the main source of caliper problems in these parts. Not leakeage.
Also regarding the weight an aluminium mulitpiston caliper is usually just as heavy as a steel single piston (much smaller) caliper like bmw stock uses. Wether a bmw needs better/larger/different brakes is a matter of opinion though (and how/where you drive).
But increasing pad size increases stamina, you can use different pad materials, and regulating the clamping force becomes easier/more precise under heavy load: so the point between the pad locking the brake and still rotating.
That last point is important because in the transition between locking and unlocking friction is very poor and unprecise. You can test that with for example a book that you want to drag across a desk on an elastic rope. The book stays stationary for a while (friction is high), but suddenly shoots along the elastic rope (at that time friction is low), until it is dragged on a constant speed and friction increases again. That also happens at braking.
So if you want larger pads, you want to spread the clamping force (otherwise the will bend a bit and load is only appied in the center).
Thats why supercars have big multipiston calipers (cost is less of an object and performance is a selling point)
The piston area an sich is not important at all, unless the braking pedal becomes so heavy that you cant apply enough force to block the front brakes. But that hardly happens at all with boosted brakes (unless you're very weak/old). The only thing to look out for is brake bias if you change piston diameter (or pad size or disc size for that matter). But you can also play with that using different pads front and rear. The main thing you dont want is the rear locking up before the fronts, but you can easily test that on a quiet piece of road.
So saying that a smaller total piston diameter in a multipiston caliper is worse than a larger (area) single piston caliper makes no sense. I mean: does the larger pad have to have the same clamping force? etc etc. In the end it comes down to having enough pressure to be able to lock the brakes (no problem) and the brake bias itself (which is a combination of pad material, pad size pad pressure disc size and disc construction, so something which is tested in practice and also varies greatly with surrounding circumstances. Thats why with real racecars the driver can adjust the brake bias while he's driving to adapt to the surroundings (heat, wear etc etc) )
How reliable something is (in the braking area) is probably more dependant on how hot, how dirty and how wet it gets plus the useage (and of course materials used etc). I think sticking calipers are the main source of caliper problems in these parts. Not leakeage.
Also regarding the weight an aluminium mulitpiston caliper is usually just as heavy as a steel single piston (much smaller) caliper like bmw stock uses. Wether a bmw needs better/larger/different brakes is a matter of opinion though (and how/where you drive).
At the end of the day, BMW manufactured the E85/86 ///M platform to sell at a specific price point, so had to build performance at a price at which it can also make a profit. It is not an "exotic" built for the super-rich, so that means compromises in features. I guess most owners don't do track-days, so the OEM brakes will be plenty good enough for most situations. I've found that with a few relatively cheap mods (brake cooling ducts, Yellowstuff pads, solid brake bushings and DOT5.1 fluid) the OEM brakes perform faultlessly time and again around The Ring, doing sessions throughout the day of 3 complete uninterrupted laps at a time (10+ sessions per day on 2 consecutive days, totalling around 750 miles) and 20-minute sessions (170 miles, or so, in total) around shorter tracks. I'm not saying that the OEM brakes are the best, but in practice, they're good.
Of course it's all about money.
I also was always amaized that bmw didnt sell brake upgrades for many years. Now, since 5 years or so (I think first started on the e82 135i and e92 m3) they also have BBK style brakes (brembo multipiston calipers) as an option (and maybe on some as standard (m6?)).
Audi (S/RS), mercedes (AMG) etc (and even a nissan 350z or a subaru impreza) have had bigger brake options for years (some even in the 90's). So it's not just for the super-rich exotics. BMW clearly had a backlog in that area.
Customers are prepared to pay for those, so if you dont sell them...... you're missing out.
Porsche has been selling carbon ceramic bbk's for years at huge prices (15k option or so, as a fairly unique selling point in that range), and finally now bmw also sells that option on the new m3/4.
/Drive (on youtube) did a test once on braking where the outcome was that the imporvement you get from racing pads/fluids you can get again from installing a front&rear BBK. So for instance if your normal stopping distance is 40m, and with a racing pad&fluid is 35m, a front/rear BBK would stop in 30m. That was a test they did on the same car with some bedding in as they upgraded. So there definatley is a lot to gain. And that was on sheer 50-0 stopping distance, real heat dissipation (like on a track, high speed braking on the autobahn or in the mountains) the difference will be significant (that's the main purpose of a bbk), but that also depends on track and car weight.
But racepads are obviously the cheapest upgrade.
I also was always amaized that bmw didnt sell brake upgrades for many years. Now, since 5 years or so (I think first started on the e82 135i and e92 m3) they also have BBK style brakes (brembo multipiston calipers) as an option (and maybe on some as standard (m6?)).
Audi (S/RS), mercedes (AMG) etc (and even a nissan 350z or a subaru impreza) have had bigger brake options for years (some even in the 90's). So it's not just for the super-rich exotics. BMW clearly had a backlog in that area.
Customers are prepared to pay for those, so if you dont sell them...... you're missing out.
Porsche has been selling carbon ceramic bbk's for years at huge prices (15k option or so, as a fairly unique selling point in that range), and finally now bmw also sells that option on the new m3/4.
/Drive (on youtube) did a test once on braking where the outcome was that the imporvement you get from racing pads/fluids you can get again from installing a front&rear BBK. So for instance if your normal stopping distance is 40m, and with a racing pad&fluid is 35m, a front/rear BBK would stop in 30m. That was a test they did on the same car with some bedding in as they upgraded. So there definatley is a lot to gain. And that was on sheer 50-0 stopping distance, real heat dissipation (like on a track, high speed braking on the autobahn or in the mountains) the difference will be significant (that's the main purpose of a bbk), but that also depends on track and car weight.
But racepads are obviously the cheapest upgrade.
I'll add to that Goodridge braided lines. Depending what your level is on track you brake less anyway as your better able to measure your speed into corners and hold speed in the corner. I know I've certainly progressed in that matter and my set up has held up v.well. I wonder how much these large brake kits on modern performance cars are about fashion and taking more money from you. Saying that cars nowadays are just so heavy