05-12-2017, 04:59 PM | #1 |
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Mixed compound vs same compound track pads
I'm running mixed compound track pads with a more aggressive pad in front than in the rear. In my case Carbotech XP10 in front and XP8 in the back. Seems as though having the front more aggressive isn't right for the M2 and they should actually be the same front and back. My fronts are wearing much faster and it feels like the fronts are doing all the work. For many other cars, having a more aggressive front compound than in the back works best and is recommended. Can anyone share their M2 experience on mixed vs same compound?
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05-16-2017, 08:47 PM | #2 |
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No one???
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05-16-2017, 08:59 PM | #3 |
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I don't think running a different compound is ever recommended. And of course the fronts wear faster, they do most of the work as that's where the weight of the car is under braking. I've not run anything drastically different. I currently have DSUNO in the rear and DS1.11 in the front. That's only because I switched to the DS1.11 and wanted to finish off the tears rather than waste them. That said, those pads are very similar.
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05-16-2017, 09:10 PM | #4 | |
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05-16-2017, 10:18 PM | #5 | |
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05-16-2017, 10:20 PM | #6 |
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I've been to a lot of track days and talked to a lot of people and I've not once run across someone who intentionally wanted a brake bias and accomplished that with different pads. Race cars don't do it as best I'm aware. I'm not saying it doesn't happen, but I don't think it's common.
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05-16-2017, 11:45 PM | #8 | |
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05-17-2017, 12:07 AM | #9 |
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I thought this might be interesting to explain brake bias:
Info from Iracing: Brake Bias This is an adjustment of the relative amount of hydraulic pressure applied to the front verses the rear brake calipers and pads. This is needed to optimize the braking power, as a car decelerates, load transfers to the front tires, which generally improves their grip, while decreasing the grip at the rear of the car. In addition, the size of the front and rear brake rotors, pads, and piston area is often different requiring different amounts of pressure for the same braking power. The goal is to adjust the proportion of the braking forces between front and rear (brake bias) in order to maximize overall braking efficiency. If the brakes are still applied as the car turns into the corner, the brake‐bias setting will also have an effect on the car’s turn‐in balance. Tuning advice: Maximum braking performance occurs just before brake lockup, as a sliding tire has less grip than a rolling tire, thus tuning brake balance is all about controlling when the brakes lockup. As max performance obviously will occur when all 4 tires (& associated brakes) are doing the maximum work, an ideal brake bias is one that locks the front and rear brakes at the same time. In practice however, locking the rear tires typically result in a rapid spin, and locking all 4 wheels results in a slower spin, especially if the car is trail braking. For this reason, some “extra” front bias is normally used [already built-in from the factory - RR], because when the front brakes lockup the car remains stable (but you lose the ability to steer the car – it just goes straight - UNDERsteer) and this allows the driver time to recognize the brake lockup and reduce brake pressure to regain max braking performance and control. To tune the brake bias, pay particular attention to what happens during the braking phase and corner entry. Sudden spins in this zone often indicate rear brake lockup, while a bad push may indicate front brake lockup. Video replays or data acquisition systems can be useful in identifying this, but remember the inner (unloaded) tire will be the first to lock. Increasing Front bias: Increasing brake bias to the front will put more braking force into the front tires. This will stabilize the car in braking zones and increase understeer at corner entry. The compromise is that with too much front bias the rear tires are being under‐utilized and overall braking efficiency will suffer. This can also cause rapid front tire wear due to front tire lockup, especially of the inside tire which is the first to lock up. Reducing Front bias: This puts more braking on the rear tires, which, within limits, improves braking efficiency. Too much rear brake bias, though, hurts performance in two ways. First, it reduces overall braking efficiency. More seriously, too much rear brake bias, particularly if the driver is not braking in a straight line or has weak footwork on downshifts, can cause the rear tires to lock up, which puts the car in a dynamically unstable condition that can easily result in loss of vehicle control. Note that with a moderate amount of rear‐brake bias, the car will have a tendency to rotate (OVERsteer) at corner entry upon brake release. |
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05-17-2017, 06:35 AM | #10 | ||
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05-17-2017, 06:47 AM | #11 |
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I agree with the assessment that the brake balance in general is set too much to the front on the M2, and by running a more aggressive pad on the fronts simply underlines this. I think that the car is quite tricky under hard braking, and even though I'm running the M Performance chassis I think the front needs to be stiffer to make it a bit more stable under braking.
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05-17-2017, 07:00 AM | #12 |
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I run more aggressive pads in the front for fwd and awd cars because they tend to be nose heavy and under steer prone. Before I picked my pad setup for my M2 (all PFC 08), I checked with a few folks that race them. Everyone was running same, or nearly the same compound front and back. Seems to be working for me, although I will say that it's easy to trigger ABS at lower speeds on track with good pads and street tires.
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05-17-2017, 10:59 AM | #13 |
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I'll add that the M2 continues to act like my E36 - specifically that the front wear rate on pads is 2-3X greater in the front than the rears.
So far, the rear pads look like they'll last forvever - just like my E36 I don't think that splitting the pad compound would change that significantly |
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05-17-2017, 11:18 PM | #14 | |
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05-18-2017, 10:54 AM | #16 |
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I'd like to add for those of you having trouble, did you try running the same compound front and rear first? I've got AP front rotors and run the same compound front and rear. The brakes feel fantastic. On track, I'm able to trail brake and rotate the car easily.
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