brake ducting advice needed
Discussion
Has anyone significantly increased their brakes by ducting air to them? My brakes are great on the road but on track days I get brake fade very swiftly.
I was thinking about removing the fog lamps and ducting air from that area to the brakes.
The car is a modified CLK55 AMG
Ideas welcomed.
I was thinking about removing the fog lamps and ducting air from that area to the brakes.
The car is a modified CLK55 AMG
Ideas welcomed.
Thanks Pilky. I haven't upgraded pads or fluid because tougher pads will mean more frequent disk changes (won't it because of greater abrasion?) 2skiddy thought this was a very cost effective option. I may change my brake fluid but when researching the pros and cons of going to dot 5.1 were not so clear cut. 
petermansell said:
Thanks Pilky. I haven't upgraded pads or fluid because tougher pads will mean more frequent disk changes (won't it because of greater abrasion?) 2skiddy thought this was a very cost effective option. I may change my brake fluid but when researching the pros and cons of going to dot 5.1 were not so clear cut.
A change in fluid on its own now wont realy help the fade issue. If you were getting a long pedal due to boiling the fluid then yes it would be a certainty.
If your getting fade ie same pedal travel but not stopping then its a pad issue and theres not realy much you can do except go for a better pad. Everyone has their own favourate recomendations, mine being Ferrodo DS 3000 (race pad) or 2500 (more a rally/ track day/ hard road use). Also Padgid blues and Mintex F4 or 6's.
Depending on how aggressive the pad and what its made from will have a bearing on disc wear. Your going to have to face facts that stopping a big old Merc from warp speed time and again means frequent disc changes. You may also consider a larger disc/caliper conversion that may save money in the long run....
There are several things that can contribute to brake fade, you would probably be best simply working through them until you solve the problems or run out of options.
If the fluid is overheating in the caliper it gradually breaks down and becomes spongey, even if it doesn't actually boil. It goes much darker when this happens, so when you replace the pads and flush the brake fluid after your track day see what state the first bit of fluid is in. When you replace the fluid make sure you use fluid with a high boiling point. The DOT5.1 standard (the '.1' is important) is usually what you should aim for, but there are some DOT4 fluids which have an even higher temperature rating. Ordinary common or garden DOT4 is no good for you though. I suggest you stay away from DOT5 and other exotic fluids.
It's normal for pads to generate gases at the contact surface when they get hot. These gases tend to lift the pads off the rotor and reduce the available friction. Grooved discs are an effective way to disperse the gases. Don't go over the top - you only need half a dozen grooves per side and definitely do NOT go for drilled discs.
The pads themselves have a maximum operating temperature above which the pads themselves start to fade. In my experience this usually also results in mechanical damage to the pads so if your pads come out with visible cracks or appear to have had the corners nibbled off and started to crumble, I would take this as a sign that the pads may be overheating. There are various pad compounds available including some that will keep working far beyond what you need. However, the pads with very high temperature ratings tend not to work at all well at lower temperatures so are not suitable for a road car. The ones to go for are usually called 'fast road' pads. DS2500 are my current favorites but there are plenty of alternatives out there.
Depending what calipers you have, you may find the calipers themselves are distorting under load. This is particularly likely to be an issue if you have single pot sliding calipers. One of the symptoms of this is uneven pad wear, so if you find the inner and outer pads wearing at different rates or any pads wearing at an angle, you have a caliper problem. If they're all wearing flat and at the same speed, you know this is OK.
Ducting cold air over the brakes can help but in my experience only a little bit and only on very high speed circuits. You can give it a try but if the problem is as severe as you suggest I don't hold out much hope.
The single simplest cure to all these problems is to fit bigger rotors and calipers. Unfortunately this is also the most expensive.
If the fluid is overheating in the caliper it gradually breaks down and becomes spongey, even if it doesn't actually boil. It goes much darker when this happens, so when you replace the pads and flush the brake fluid after your track day see what state the first bit of fluid is in. When you replace the fluid make sure you use fluid with a high boiling point. The DOT5.1 standard (the '.1' is important) is usually what you should aim for, but there are some DOT4 fluids which have an even higher temperature rating. Ordinary common or garden DOT4 is no good for you though. I suggest you stay away from DOT5 and other exotic fluids.
It's normal for pads to generate gases at the contact surface when they get hot. These gases tend to lift the pads off the rotor and reduce the available friction. Grooved discs are an effective way to disperse the gases. Don't go over the top - you only need half a dozen grooves per side and definitely do NOT go for drilled discs.
The pads themselves have a maximum operating temperature above which the pads themselves start to fade. In my experience this usually also results in mechanical damage to the pads so if your pads come out with visible cracks or appear to have had the corners nibbled off and started to crumble, I would take this as a sign that the pads may be overheating. There are various pad compounds available including some that will keep working far beyond what you need. However, the pads with very high temperature ratings tend not to work at all well at lower temperatures so are not suitable for a road car. The ones to go for are usually called 'fast road' pads. DS2500 are my current favorites but there are plenty of alternatives out there.
Depending what calipers you have, you may find the calipers themselves are distorting under load. This is particularly likely to be an issue if you have single pot sliding calipers. One of the symptoms of this is uneven pad wear, so if you find the inner and outer pads wearing at different rates or any pads wearing at an angle, you have a caliper problem. If they're all wearing flat and at the same speed, you know this is OK.
Ducting cold air over the brakes can help but in my experience only a little bit and only on very high speed circuits. You can give it a try but if the problem is as severe as you suggest I don't hold out much hope.
The single simplest cure to all these problems is to fit bigger rotors and calipers. Unfortunately this is also the most expensive.
This has pretty much been said above but I popsted this on another forum earlier this week;
I think important to note that fade and fluid boiling are too different concepts (but both caused by too much heat!). Fluid boiling is just that, the fluid fails because it gets too hot (or more likely that there is moisture in it which brings down the boiling point significantly). Once it has boiled once it needs changing. Better/new fluid and extra cooling/ducting (and possibly bigger discs) will help this.
Pad fade is when the pads overheat, and the gases that are given off cause the pad to aquaplane accross the surface of the disc, hence why some discs have dimples/grooves/holes in them to expell the gases (as well as have some cooling effect). Prob need some higher spec pads in this case, or bigger discs/extra cooling/ducting which will help remove some of the unwanted heat in the system.
I would also try to get rid of any braking problems without increasing the size of the disc - do this as a last resort, since it increases unsprung weight dramatically, unless of course the bigger dia. discs are fancy alloy belled jobs
Jonny
I think important to note that fade and fluid boiling are too different concepts (but both caused by too much heat!). Fluid boiling is just that, the fluid fails because it gets too hot (or more likely that there is moisture in it which brings down the boiling point significantly). Once it has boiled once it needs changing. Better/new fluid and extra cooling/ducting (and possibly bigger discs) will help this.
Pad fade is when the pads overheat, and the gases that are given off cause the pad to aquaplane accross the surface of the disc, hence why some discs have dimples/grooves/holes in them to expell the gases (as well as have some cooling effect). Prob need some higher spec pads in this case, or bigger discs/extra cooling/ducting which will help remove some of the unwanted heat in the system.
I would also try to get rid of any braking problems without increasing the size of the disc - do this as a last resort, since it increases unsprung weight dramatically, unless of course the bigger dia. discs are fancy alloy belled jobs
Jonny
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