Cooling the Brakes

[cantfindausername]

This is something that I'd like to do to prolong the life of my brakes on track and road trips.

I have a plan to get some spare dust shields that are mounted at the back of the discs. On here I plan to weld some tubing that I can connect a feed pipe from an air duct too.

My question relates to where is it best to feed the cold air? To the caliper? Or to the center of the disc? The discs are vents front and rear.

Thanks for any advice on this subject.
Ant

[Evodelta]

Ant,

The usual place on a braking system to cool is the disc, the place on the disc which you would aim the cooling air is the centre.
What happens is the air is sucked into the centre (by the helical veins) and thrown out of the perimeter.

Are your brake calipers trailing or leading edge? If they are trailing you may be in luck.... ;-)

You can also cool the calipers, it is dificult though and inefficient cooling can cause warping etc (as it can be by blowing onto one side of a disc). If the car boils top of the range fluids then you can consider a fluid circulator.

Martin.

[cantfindausername]

Hi Martin, this is the car in question... can you explain wether they are leading or trailing calipers please?



I think I would rather cool the disc than the caliper. I would ideally like to get a feed to both sets of brakes (front and rear). So far I've not boiled brake fluid so hopefully wont need to get too extreme. A little bit of cooling will hopefully give me what I need.

Thanks,
Ant

[Evodelta]

Ant,

Perfect, your fronts are trailing edge and your rears are leading edge. It's easy really, it refers to whether the calipers are mounted on the trailing or leading edge of the disc. :-)

I'll PM an idea over later as it is in breach of forum rules.

Martin.

[smckeown]

I've always been advised to fit thicker disks to prevent warping. Never had fade therefoire a need to cool

[cantfindausername]

Thanks Martin.

Sean, I'd love to fit bigger brakes, but until I have the spare £2.5k to get the set I want, an upgrade to pads, lines and fluid will have to suffice, thats why I'm trying to reduce the heat in them to help prolong the life of them.

The road trip I'm planning for 2009 will take in some very steep hills, we're visiting Stelvio and on our trip and this year 4 out of 4 cars cooked their brakes. So we're all taking further precautions next time round. (my car wasn't there this time).

[TR-Spider]

Feeding the cooling air into the center of an vented disk is advicable.
I would focus on the front fist.
Take care to use a decent tube diameter (lets say larger than 60mm) and to have a nice inlet in your front spoiler to collect the air into the tube.

Thomas

[cantfindausername]

Thomas thats the idea. Although I hadn't thought too much about pipe diameter.

I was speaking to Phill yesterday and he's given me the idea of spacing the calipers out and fitting larger discs. This is something that i'm going to look into as it would probaly be the cheapest & easiest option. The brakes are fully capable so it could be a winner.

Ant

[cantfindausername]

Just been looking around for ideas and if possible I'd like to reduce the unsprung weight. So, was thinking of running a set of discs with the aluminium top-hats/bells.

Am I right in thinking I'd just need to get something that would be the right center bore diameter (60.1) and PCD (5x114.3), mount this on the hub and then get a spacer mount for the caliper?

Ant

[TR-Spider]

Am I right in thinking I'd just need to get something that would be the right center bore diameter (60.1) and PCD (5x114.3), mount this on the hub and then get a spacer mount for the caliper?

Dont forget the offset between disk and mounting durface. Disk must match caliper and clear suspension etc.

Just been looking around for ideas and if possible I'd like to reduce the unsprung weight

When you increase disk diameter, you most likely do the opposite...

I did not fully understand your motivation with the brakes.
The cooling will be helpfull in any case, because you can brake hard more often (trackday) without overheating the brakes.

Are your standard brakes insufficient?
Did you already try different brake pads? Better brake pads have higher friction rates and a more constant friction rate over temperature. Same goes for the stdt size disk, there are certainly different materials available.

I suppose your car has ABS (antilock brakes). When you really brake hard, can you get the ABS goeing in at all speeds? If thats the case, your brakes can lock the wheels, i.e. the momentum is high enough -->no need for bigger disk.
If you start changing disk size, how about the front rear ratio and will the ABS still work?

Thomas

[cantfindausername]

No ABS fitted to the car, so thats something that can be knocked off the list.

If I could get some ally bells/top hats and discs, I don't think the weight difference would be that great. Albeit more or less. To be honest I've never felt the weight of a ally bell/floating disc set up compared to a single piece disc.

My thoughts behind a bigger disc is the ability to hold and dispense of heat more than a smaller disc, and that you would get a more progressive pedal. I could be wrong though. Either way I'd be looking to cool whatever set up I go with. Obviously I'm looking to learn about this subject so am always open to be corrected and informed by others.

I've got the specs of the standard discs that are on the MR2:
Front:
Diameter: 275mm
Hub Hole: 62mm
OVerall Height: 48mm
Thickness: 30mm

Rear:
Diameter: 282mm
Hub Hole: 62mm
OVerall Height: 47mm
Thickness: 22mm

IF I decide to go for a bigger size, what would be a good size to go up to?

Bigger brakes aren't the be all and end all, its mearly an option that I'm looking into. Cooling the stock brakes and running with my uprated lines & pads on new discs is going to come first, but this will probaly run as a side project.

Ant

[Guy Croft]

Ant, hi

I would suggest, given the level of prep on your car, that you look into a complete revamp of the braking rather than just the wheel end. Check out balance beam braking. This will require removal of the pedal box and rebuild to allow adjustable bias with dual master cylinders or even a comp pedal box, but the results are well worth the effort. I know from exp that simply adding bigger brakes, pers se, can cause problems with OE master cylinder capacity and size.

Have a look at AP Racing's site: http://www.apracing.com/info/index.asp? ... +Boxes_982

GC

[cantfindausername]

Thank Guy.

I think I have a lot of information to take forward and look at over the coming months.

In the mean time I think I shall concentrate on cooling the "stock" sized brakes.

The set up I'll be running is Goodridge Braided Line, Stock vented discs, Mintex uprated pads and new 5.1 fluid.

I am getting a second set of dust shields that sit behind the brake discs and I am looking to welding on some hose adapters so I can duct cold air into the center of the discs. There was a size of "larger than 60mm" mentioned earlier in this thread, however, due to potential space limitations I've been thinking that 2 x 30mm (?) air feeds per disc might be an idea. Would there be any down sides to running 2 air feeds? I feel that the smalled ducting would be easier to feed into the center of the disc.

Thanks,
Ant

[Rich Ellingham]

Hi Ant just from my experience I can tell you my set up.

I have 284mm brembo dics one drilled pair and one solid (no drill holes) they are aonly about 22mm wide and vented. THe calipers are an all iron sliding caliper from a Fiat coupe 16v Turboe. Pads are ferodo DS3000, fluid is willwood high temp. Std master cylinder with Tilton bias valve to the rear. I would say their functioning was OK, but as I improved on track I soon out grew my braking ability. In the last few races I added cooling hoses to the rear of the discs. Either way I had to regrind the discs after each qualifying and race hence have 2 sets, and a track day would require the same. The cooling maybe helped on track but after a cooling cycle the discs would be warped making trail braking very difficult 9and the servo doesnt help that). The narrow 1 piece disc is not a good item for the track unless it happens to be very wide, I think off the track the wheels would have needed to keep rotating to stop the hot spot cause by the pads insulating the disc.

I don't know you background but I think your car is going to be very powerful, my esitmation on the track that maybe you will have to get used to a lot, and your braking abiltiy will need skill to create the requirement for a major upgrade. Thus in the short term I would not waste any time with playing with what you have apart from pads and fluid. I would take Guy's advice and look to the longer term plan of a full braking system, 4 pot calipers, 2 part discs (less like to warp and also available with wide vanes) and the pedal box loosing the servo. If I was to continue racing this is 100% my first priority (plus weight saving as that is beneficial to braking) for development. In my last race being out braked cost me many places as that when the places were taken and I was hard on the brakes.

rich

[TR-Spider]

Ant

2*30 mm probably wont do it.
So 2*30 is just 50% of the open area of 1*60. 2*42 mm would be equal open area.
Because you are depending on "natural" flow you should try to keep the pressure loss in the piping low.
Twin tubes with the same open area as a single tube will give higher loss due to larger wall area (especially if flex tubes).
The air mass flow will be proportional to the open area of the tube, so keep it as as big as possible.

In that respect bigger = better.

As an inspiration a typical McPherson Type arrangement:

Größenänderung IMG_1096 brakes.jpg (58.33 KiB) Viewed 10704 times

It would help if you could post some pictures to show how it looks on your MR2.

Thomas