[Cloud9...68]

[quote name='flash' timestamp='1341670066' post='128982']

the other issue is that big reds are insanely heavy.

[/quote]



Interesting how this thread has turned into a discussion about brakes. Not too far off topic, I guess, as the very capable brakes are part of what make this car great.



But Flash's comment about the weight of big reds caught my eye. The previous owner put a set of 1989 951 Turbo S calipers on my car, with Zimmerman cross-drilled rotors all around (don't know the diameter offhand, and they're at the machine shop at the moment). The calipers, which are stamped with the Brembo brand, are indeed huge, and red (does that automatically make them "big reds"?). Given Flash's comment about their weight, I assumed they were made of steel (shows you how much I know about brakes), so I took a magnet to them, and found that in fact the calipers, along with the adapter block needed to fit them to my non-M030 spindles, are made of aluminum. So my question is, how is it possible to get a lighter caliper, and maintain the large pad surface area these calipers provide? Or are "big reds" (whatever that technically means...) heavier than the 1989 Turbo S calipers that are on my car?

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[craigawoodman]

Cloud,



Near calipers are better designed. The calipers purpose is to apply a clamping force to the brake rotor to induce friction and hence slow the wheel down. One of the biggest issues is flexing of the caliper and heat transfer to it as well. With computer aided simulations, they can now make calipers lighter that disperse heat better, clamp more evenly, etc. We are not talking massive weight savings for calipers however. The biggest weight saving is going to a floating rotor (aluminium hub and cast iron/steel rotor - don' ask me what materials they use now - or even ceramic). The aluminium hub, removes the centre section of the brake rotor with an aluminium section - so a lot of mass is reduced. The ceramic brake rotor, does the same for the actual rotor - lessens the mass.



Like Flash has alluded to, reducing rotating mass and unsprung mass can have massive benefits in handling (as there is not as much rotational interia to accelerate, and less mass to have to dampen with springs and shocks, etc).



So, the best option is a total brake upgrade - but very expensive. The caliper, pad and rotor all have to work together to give the best outcome.

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[Cloud9...68]

So, as far as calipers go, while I may not have the latest and greatest design on my car, there isn't a whole lot of advantage from a weight savings standpoint of going with something more modern (which would be a VERY expensive undertaking). It seems like for my purposes, the most cost effective thing I can do as far as my brake set-up is to go with some racing pads, and add ducting (I'm working on replacing the pop-up headlights with fixed headights, which will free up a lot of space to run ducting). I already have a Turbo (can't remember the model - it was one Pete recommended years ago) proportioning valve. But, given that my near-term plans (besides getting the car running, of course) involve highly technical tracks where braking isn't as critical, any further mods to my brakes are a pretty low priority at the moment.

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[White968]

Not doing any high speed driving, just alot of stop and go. I live in a very populated Metro area with hills. One of the first things I noticed before I purchased my 968 was the large rotors and thought they would do a fine job. Maybe there is something wrong with my brakes. I will have my mechanic take a look at them. Flash, I dont want to go the "Big Red" route..doesn't warrant it.

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[AJG]

[quote name='White968' timestamp='1341726205' post='128994']

Not doing any high speed driving, just alot of stop and go. I live in a very populated Metro area with hills. One of the first things I noticed before I purchased my 968 was the large rotors and thought they would do a fine job. Maybe there is something wrong with my brakes. I will have my mechanic take a look at them. Flash, I dont want to go the "Big Red" route..doesn't warrant it.

[/quote]

I had brake problems recently, I had sticky front pistons. Required new rotors and a caliper strip down. A quick and easy check for sticky calipers is to sit on a gentle slope, release the handbrake and then the car should want to move immediately down the slope. If it doesn't you may have a sticky caliper or problems with the handbrake shoes! You might try R S Barn cobalt brake pads, there very good but be warned apply a liquid polish to your rims to give them a barrier against the brake dust which can bind on viciously to them, then recoat every so often to maintain that barrier. Have to say it again the white 968 is absolutely spiffing old boy, considering I'm sick of the sight of white Audi A5 coupes in Aberdeen its very refreshing.

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[craigawoodman]

Big brakes don't squeal, the brake pads are what normally causes brake squeal (unless the rotor is seriously glazed). Racing pads require heat to work at their best (whereas normal pads will overheat and release gas - hence fade). The pads have to suit the application and the environment. Backing plates for the pads can also help distribute force into the pads more evenly.

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[White968]

I will put it to the test AJG

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[Dubai944]

Big Brakes is always an interesting and misunderstood subject.



Braking is ultimately limited by tires. Bigger brakes won't reduce your stopping distances if your current brakes are already capable of reaching the limit of your tire grip. If you can already lock your tires or push them into ABS bigger rotors and calipers won't do squat. Chances are the larger rotational mass of big rotors and possible increase in unsprung weight from bigger calipers and rotors will increase your stopping distances. For a standard car with big enough front brakes to easily lock the front tires, the only improvement you can really make in terns of stopping distances is a bit more bias to the rear to push the rear tire grip closer to the limit when braking, because the factory bias is designed to keep you well away from the chance of locking rear brakes so they leave some rear braking grip on the table. You can do that easily with a bias valve change or with more agressive rear pads.



When you increase tire grip dramatically you then may need bigger brakes with the retarding force to tak the tire to its grip limit when braking, but the factory brakes are more than capable even with standard size slicks. The other, and much more important, justification for bigger brakes is heat management. Once you start limit braking from high speeds and or repeatedly limit braking over and over again you start to put so much heat into the system it can't get out and then you get pad or fluid fade. Often you can stem that off without bigger brakes just by running better pads and higher temp brake fluid and possibly some brake ducting. Probably all you will ever need for an occasionally track driven road car. Better pads can also change how the brakes feel with better intial bite and modulation control.



For race cars with wide sticky tires, much higher speeds and much more frequent limit braking bigger brakes finally start to make sense. But you still only want just big enough brakes to match the grip of your tires and avoid any pad or fluid fade for the period of time you are racing. Any more than that is just extra weight.

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[Cloud9...68]

Very well put, Dubai. The money people waste on expensive brake upgrades (not just on this car) never ceases to amaze me, when, as you say, it only becomes necessary under extreme conditions. This applies to the previous owner of my car with the big calipers/large disks he installed - you're right, the extra mass is probably slowing my car down more than the marginal improvement in extreme-condition stopping power is helping. Oh, well, at least they look cool, and as I progress to higher-speed tracks and stickier tires, hopefully I'll be able to realize their potential sometime down the line. In the meantime, you have me wondering whether I should go back to stock brakes...

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[flash]

unfortunately, until you increase the physical size of the rear brakes, thereby increasing the heat dissipating capabilities, you'll likely never get there. a bias valve alone just won't do it. it'll be fine on the street, but on the track, where you will now start cooking the smaller rear brakes long before the front ones, you'll only lose braking ability.

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[Cloud9...68]

The <acronym title='previous owner'>PO</acronym> of my car installed larger brakes at both the front and the rear. But as I said, I'm now wondering if this has done more harm than good. But at my level of driving, running with the oversized brakes I have, vs. stock brakes all around, probably wouldn't make a measurable difference either way. It's amazing how much larger the pads on my car are then stock, though. I once ordered a set of stock pads by mistake, and they looked like they belong on a toy car compared to the monsters I have.

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[AJG]

[quote name='flash' timestamp='1341843296' post='129029']

unfortunately, until you increase the physical size of the rear brakes, thereby increasing the heat dissipating capabilities, you'll likely never get there. a bias valve alone just won't do it. it'll be fine on the street, but on the track, where you will now start cooking the smaller rear brakes long before the front ones, you'll only lose braking ability.

[/quote]

Ah Bob, Bob, even when he pisses on our parade its like music to our ears( tinkling sounds?). Keeping us on the straight and narrow I give you Booooob!

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[flash]

interesting - what did he put on the rear? i've often wondered what would end up balancing with big red fronts.



AJG - lol - brakes are a bit of a hot button for me. i've been working on a project on and off for about 8 years now. i've fiddled with a few different things, and driven a couple of Big Red front cars. every time though i come back to the OEM setup being the best, but only improving pads, lines, fluid, and changing the rear bias valve.

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[AJG]

There's a lesson for us all, throwng money at things is not always a winner, a bit of honest thought about what's best is always conducive. And saves money for fuel ha ha. I love it when threads string together. Push the button Max!

PS, are there other materials besides cast iron and ceramic of course that rotors can be usefully made from?

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[AJG]

PPS, I've noticed that massive chains are great at slowing down ships being launched. Perhaps we're missing an obvious solution? It even works when their sideways! Great for the track!

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[AJG]

[quote name='Cloud9...68' timestamp='1341851809' post='129038']

The <acronym title='previous owner'>PO</acronym> of my car installed larger brakes at both the front and the rear. But as I said, I'm now wondering if this has done more harm than good. But at my level of driving, running with the oversized brakes I have, vs. stock brakes all around, probably wouldn't make a measurable difference either way. It's amazing how much larger the pads on my car are then stock, though. I once ordered a set of stock pads by mistake, and they looked like they belong on a toy car compared to the monsters I have.

[/quote]

Right getting serious momentarily, bigger pad area times the force applied per square inch will not give a straightforward percentage incease in stopping power per extra percentage of pad area. IE 50% more pad area doesn't mean that amount extra stopping power. Or does it? No it doesn't because the available pressure is spread over a bigger area reducing psi/sq inch. It's like lying on a bed of nails....or just one! Ouch!

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[Cloud9...68]

[quote name='flash' timestamp='1341853685' post='129043']

interesting - what did he put on the rear? i've often wondered what would end up balancing with big red fronts.

[/quote]

Not sure - I can measure the caliper dimensions and rotor diameters, and post a pic, when I get home. I assumed they were off the back of an '89 Turbo S, but I'm not 100% sure. They look big (and heavy), whatever they are. I've just never paid much attention to brakes, recalling the answer the great Fangio gave when a reporter once asked him the secret to his racing success, "More gas, less brake..."

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[Dubai944]

The main advantage of bigger pads is simply that they last longer between changes. Important in endurance racing when you want to avoid unnecessary pad changes during a race.



You can run bigger fronts with stock rears, but it is about matching the piston area to keep balance. I have Stoptech six piston ST60 calipers and 355mm floating rotors on the front. Total piston area of the six pot Stoptech calipers is almost identical to that of the original M030 S4 4 pot fronts. With a 5/33 bias valve the balance is great with the original M030 rears.

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[flash]

that's fine for pressure matching, but does not address cooling. cooling is purely a function of the size of the rotor. if you are grabbing nearly equally, with only a minor front bias, which is the goal in any performance car, then the heat is pretty even across all 4 rotors. that means you need larger rear rotors to handle and dissipate that heat. they don't usually need to be quite as large as the front, but they do need to get bigger if you go much bigger on the front.

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[Dubai944]

I don't disagree with that in theory. In practical terms the M030 rear calipers and rotors seem to have more than enough cooling capacity with brake ducting to the rear, and the advantage of better heat control on the fronts has vastly improved my braking consistency in long races. So although not perfect the net result is a better braking system.



I can brake like this for hours on end wth no hint of degradation <img src="/forum/images/smilies/968/smile.png" class="smilie" alt="" />

[media]http://vimeo.com/32864934[/media]

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