Brake fade - how to combat it?

[custardtart]

EBC yellow is pad of choice for westfield series having won it the last two years. I switched to them this year and they are a great pad for this application, lots of feel and bit and no fade at all. Much better than the Mintex 1144 or EBC Green I've used previously. I guess it depends on the application.

However, in repsonse to the OP, check you are using the right DOT rating, change the fluid, change the pads and bed em in, change the discs and bed em in. Have an honest look at your braking technique, do you linger slightly on the brake pedal prior to full application, if you're braking early and spending more time on the brakes this is worse for heat build up than braking harder but for less time.

[RobM77]

I've never experienced brake fade in a racing car I'd echo what others have said - ensure you're using a decent racing brake fluid, look at some decent racing pads and I'd also add to that make sure the brake ducting and cooling is as per manufacturer and regulations specify.

My Caterham ran on some carbon metallic pads of some description (can't remember their exact name), I don't know what my current race car, a FRenault, runs on (arrive and drive so I never fiddle mechanically). With my Metro, I experimented a bit with various pads: sent through Pagids like hot dinners so my wallet needed a break from those, but found Ferodo DS3000s worked for me. I'd ask around other guys in your championship and experiment a bit.

HTH

[h_____]

To be fair the OP runs decent fluid, I think fluid has been ruled out. Sounds like a pad issue. Ditching EBC sounds like a starting point. Query is does he go hotter or colder pads, or just different brand.

[RobM77]

[quote=h_]To be fair the OP runs decent fluid, I think fluid has been ruled out. Sounds like a pad issue. Ditching EBC sounds like a starting point. Query is does he go hotter or colder pads, or just different brand.
[/quote] Sorry, just some general advice there.

[andygo]

Are you sure you are not getting 'pad knockoff', where the disc is flexing (generally because of a slightly loose wheel bearing) causing the pads to move away from the disc. This causes increased pedal travel which could be confused with brake fade.

I suggest this because of the rapid way in which your brakes recover their feel.

Try gently left foot braking before the problem corners.

Brake fade generally presents itself as a 'long' squishy pedal which gets worse the longer you are braking.
Pad knockoff generally presents itself as an instantly long pedal after a long, fast, high load corner.

Both the corners you describe(assuming you are not using the GP versions of the track) come fairly soon after a fast corner beforehand where brakes would not have been a major factor.

As a lat comment, what colour are your discs after a race/ If they are very 'blued' then brake temps are an issue, if not, refer back to caliper/disc/wheel bearing flex as above.

Edited by andygo on Sunday 12th July 21:48

[RobbieL]

Bit of an udate - upgraded the pads for Oulton Park last weekend to Ferodo's and my gosh they make a difference. Braking distances were greatly reduced and I had a lot more confidence inmy braking capabilities - however, this problem still reared it's ugly head once or twice.

As has been suggested above, i think I may be getting pad knock off as I experienced the problem after going past lakeside into Shell Oils and at the top of Clay Hill into Druids. Both quick, high load corners and both where there was a lot more pedal travel before I got a bite.

I know it has been suggested that a loose wheel bearing may be the culprit however is there anything else I should look for? Could this problem be warped discs also?

[fergus]

Robbie, could it be that the stub axle isn't up to the job under high cornering loads. I had the same problem at the Ring with my caterham. The cornering loads were high enough to put a lot of stress on the front hubs/stub axles which meant that I had to pump the brakes for the next corner.

Checked m/c seals, caliper seals, went up to the next spring rate for the springs behind the pistons. Eventually replaced the hubs and stub axles for bigger items, and the problem has gone away.

What are the hubs/uprights from on your S2000?

[clubracing]

Pad knock off is also caused by vibrations from riding over the kerbs. You could be getting pad knock off from the kerbs at Hislops going into Druids. Could possibly be the same at Shell if your taking lots of kerb on the exit of Cascades and not braking at Island.

[fergus]

clubracing said:

Pad knock off is also caused by vibrations from riding over the kerbs. You could be getting pad knock off from the kerbs at Hislops going into Druids. Could possibly be the same at Shell if your taking lots of kerb on the exit of Cascades and not braking at Island.

If that's the case, you may want to run preload springs behind your pistons? AP do these in 3 sizes/weights: 2, 4 and 7 lbs.

[andygo]

After a 'big' corner, just try pumping the brake pedal gently with your left foot. All you are trying to do is get the pads close to the disc. You will only need to press once or twice just to move the pads back - no need to actually slow the car.

If when you actually do the braking for the corner the pedal is firm and at the top, then you know knockoff is your problem rather than fade.

As a matter of interest, what do your fellow racers have to say on the matter? (Beware of bull though, lol)

[peter.brown]

doing track days in a road car had ahard pedal but no stopping power pads were expanding to much and stiking in the callipers

[fergus]

peter.brown said:

doing track days in a road car had ahard pedal but no stopping power pads were expanding to much and stiking in the callipers

Probably "green fade". Usually a function of the pad material having no friction at the temp they're being asked to work at. If your pads were 'expanding' to the extent that they weren't moving in your calipers, I'd swap to *any* pad from any of the well known pad manufacturers, or go back to OEM, as I've never heard of this before.

For this to happen enough to jam the caliper, I think you'd need to have caliper temps of over 1000 degrees C. Given that most race calipers (not discs) run around 250 C (max), I think there's an element of misunderstanding here.....

[Dave Brand]

fergus said:

Probably "green fade". Usually a function of the pad material having no friction at the temp they're being asked to work at.

Green fade is a phenomenon which will only be experienced with new pads. It occurs the first time (or few times) the pads are brought up to normal operating temperature which. The working face of the pad becomes resin-rich as the curing process is completed - curing temperatures used in the production process are generally lower than those which will be seen in service. Green fade should not be experienced with road pads as the working face should be 'scorched' (i.e. bought up to working temperature) as part of the manufacturing process.

[fergus]

Dave Brand said:

fergus said:

Probably "green fade". Usually a function of the pad material having no friction at the temp they're being asked to work at.

Green fade is a phenomenon which will only be experienced with new pads. It occurs the first time (or few times) the pads are brought up to normal operating temperature which. The working face of the pad becomes resin-rich as the curing process is completed - curing temperatures used in the production process are generally lower than those which will be seen in service. Green fade should not be experienced with road pads as the working face should be 'scorched' (i.e. bought up to working temperature) as part of the manufacturing process.

OK what do you call the phenomenon where the pad material gets too hot and the friction coefficient tails right off, giving you a hard pedal, but no retardation?

[tristancliffe]

I mentioned the three types of fade in an earlier post. I understand it is a pain reading previous replies.

1. Green Fade - As above
2. Pad Fade - Pad working temperature exceeded
3. Fluid Fade - Fluid working temperature exceeded (may not be the temperature on the bottle due to hygroscopic action and the boiling point of water).

[S1MMA]

fergus said:

peter.brown said:

doing track days in a road car had ahard pedal but no stopping power pads were expanding to much and stiking in the callipers

Probably "green fade". Usually a function of the pad material having no friction at the temp they're being asked to work at. If your pads were 'expanding' to the extent that they weren't moving in your calipers, I'd swap to *any* pad from any of the well known pad manufacturers, or go back to OEM, as I've never heard of this before.

For this to happen enough to jam the caliper, I think you'd need to have caliper temps of over 1000 degrees C. Given that most race calipers (not discs) run around 250 C (max), I think there's an element of misunderstanding here.....

Thread resurrection - but I just wanted to pick up on this:

With new or nearly new/low mileage multi piston calipers you shouldn't have a problem with pads binding unless very hot temps are reached as per above, but with older calipers which have seen a fair bit of action and rain/salt roads, you can see corrosion and oxidation in the area where the pads are seated in the caliper. On some brembos and simiar calipers which utilise metallic pad guides (which sit inside the caliper, sometimes clipped on, sometimes screwed in), you can get quite severe oxidation beneath the guides which then compresses the space the pads have to work in. This can result in pads that just fit when cold, but don't require much heat to expand ever so slightly and bind.

In this case you really need to get in your caliper and get rid of the oxidation, or have them fully refurbished if they have had a hard life. Understanding the condition of your caliper is key in an older track car IMO, pistons should all move freely and you should be aware of the condition of your dust guards etc. In a road car I can understand if you don't pay much attention to your calipers, but in a track car I'd recommend always changing the brakes yourself so you know yourself what condition everything is in. A mechanic is not going to care as much as you are no matter how good or reputable they are. Just my 2p.

[PhillipM]

andygo said:

Are you sure you are not getting 'pad knockoff', where the disc is flexing (generally because of a slightly loose wheel bearing) causing the pads to move away from the disc. This causes increased pedal travel which could be confused with brake fade.

I suggest this because of the rapid way in which your brakes recover their feel.

This, for both the OP and the poster with poor brakes and floating discs over certain speeds - it's symptomatic of pad knockback, check the caliper pistons all move freely, there's no play in the wheelbearings or excessive float in your bell/disc setup, and if all else fails, try some anti-knockback caliper springs.