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09-07-2016, 02:29 PM | #15 | ||
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6 pot, 1.38 inches first piston, 1.12 inches 2nd and 3rd pistons. 4 pot, 1.25 inches on the 4 pot sport kit. Rotor sizing is published on their website but it's just a standard STI rotor. Quote:
Regarding the price point, it's clear to me that using standardised parts is how they achieved the price point they have. Unfortunately, this does mean that things aren't perfect and their front kits DO have a small forward bias shift when used with OEM rears. @JRitt ran the numbers in another thread that I can't be bothered to find right now where he saw around 3% bias shift forward on the 6 pot kits and 5% bias shift forward on the 4 pot kit. He was of the opinion that it was a bit too far forward for their customers who track at the highest levels of HPDE and motorsport but I think it would be perfectly adequate for the remaining 9/10 customers. |
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09-07-2016, 02:52 PM | #16 |
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I mistakenly read this as the Wilwood 4 pot kit for the WRX which was discussed earlier. Haven't checked on the OEM Subaru 4 pots. Previous post from me refers to Wilwood.
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09-07-2016, 03:25 PM | #17 |
One note, and something I've not seen mentioned on this forum (though it's mentioned in the Stoptech white paper linked in the OP's article)....
If you run very high grip tires, then you can potentially generate more forward weight transfer than on OEM tires. Essentially this means that the "ideal" brake bias for a car on hoosiers is not the same as it is for a car on OEM tires (or in the rain). This is not to say that you should increase your front brake bias from OEM when moving to sticky tires. The OEM brake bias has other design considerations beyond just achieving the shortest stopping distance possible and the ABS system complicates things. But a massive shift rearward can suck just as much as a big frontward shift. Small changes in bias can shorten stopping distances slightly and help a driver feel more comfortable with the car, but it's important to think about the complete picture. A rearward shift can also be helpful if you're running aero that's actually effective. - Andrew Last edited by Racecomp Engineering; 09-07-2016 at 04:41 PM. |
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09-07-2016, 07:38 PM | #18 |
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i'm actually confused on the RR. on the one hand they provided that excel bar chart, and noted the friction was the same front and rear. i don't know how any inputs to it were made or measured at all though.
on the other, i got the piston sizes in an e-mail - and it's the standard wilwood 6-piston front - which using the calculator appears to push it almost as forward (12.88 wilwood rotor vs. 12.8 RR) - even if i try to make a better effort at comparing something like effective rotor diameters, the shift forward still ends up being a 4% increase vs. oem instead of 5% just using outer diameter. so it is hard for me to conclude the bar chart is valid and the net change vs. stock is zero. thoughts?
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09-07-2016, 07:50 PM | #19 | |||
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and indeed the same caliper. dark's experience http://www.ft86club.com/forums/showp...97&postcount=6 would seem to jive with it actually moving the bias forward as well. i am having a tough time accepting the bar chart now. Quote:
Quote:
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09-07-2016, 10:10 PM | #20 |
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These calculations are sound and necessary for sanity check. However, a few % difference should not be a major factor to evaluate a kit. The actual bias will never be the same.
- front / rear pad and rotor temperature difference, thus friction difference, throughout a session or even one braking zone. - RPM and gear dependent engine brake on rear. These two factors alone can easily shift over 10%. Moreover, it is hard to say one bias is better than other. Optimum bias changes throughout braking phases. In the initial phase, I want very strong front bias as rear unloads (Wf >>> Wr). In the middle phase, I want mild front bias as rear settles(Wf > Wr). Towards the end phase, I want strong front bias (Wf >> Wr). |
09-07-2016, 10:59 PM | #21 |
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Thanks I worked out the maths WRX 4 pot will move the BIAS a little towards the rear, might actually be a very good combination with stock rears
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09-07-2016, 11:06 PM | #22 | |
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09-08-2016, 11:16 AM | #23 | |
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w I thought the article raised a lot of good questions. I don't have the bandwidth to go through all of the numbers again, but it's great to see people thinking these issues through! Slapping the cheapest kit available on the car always appears to be a reasonable option in the short-term, particularly to someone who is working with incomplete information (which frankly, is most people since we can't all be experts on everything). Since you're going to own your car for a number of years however, it makes a whole lot of sense to carefully choose where you'll invest a couple grand of your hard-earned money.
One of the OP's quote in the article really made me think about the idea that someone may not know what they're really getting until they have it: Quote:
Our Essex Sprint and Endurance Kits are now running on many hundreds of BRZ's, FRS's, and GT86's all over the globe. Our incidence of problems or issues is incredibly low. Most of our customers tell us that our brake kit was the single best modification they've done for track use, and that it has saved them tremendously on their lap times, consumable costs, and wrenching time. Many of those customers have also had their kits on their car for four years now, and are still on the first set of discs! Finally, keep in mind that ALL of those customers are running OEM rear brakes with upgraded pads and lines...NOT a complete rear brake kit. So was it worth a few hundred bucks more initially to get the best front brake system available? We think so, unless you're just looking for those extra 'hard parking points' mentioned in the article which come with a rear BBK. I saw a great quote the other day that I think is extremely applicable to the brake kit market. "Buy the best and you'll only cry once." |
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09-08-2016, 12:10 PM | #24 | |
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Last edited by JRitt; 09-08-2016 at 01:40 PM. |
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09-08-2016, 12:36 PM | #25 | |
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BP 20 + ST45 rear would cause the rear to lock up under braking, so not a good combination either, (had bought the pads to go with the ST43 in the OEM setup, but bought the kit shortly after and never bought ST45 for the RR kit) I just ordered Ferodo 2500 for the kit to match my rear (and stop the excessive squeling from the BP20s) And will report after I try the setup at the track day. |
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09-08-2016, 12:43 PM | #26 | |
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09-08-2016, 12:46 PM | #27 |
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09-08-2016, 01:26 PM | #28 |
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I have the RR 4pot Sport kit and I'm running it with BP10 in front and EBC Yellowstuff in OEM rears right now and I have been very impressed with this combination for daily and intermediate track use. Knowing what I know about the bias of the SP kit now, this makes sense because the BP10s have ~.45 peak friction coefficient and the yellows have ~.55 which I'd guess sets my bias close to OEM.
I do have a set of Yellows for the front kit which I had trouble fitting when I first got them. It could have just been because I was tired at the time but I think they may need a tiny bit of grinding to fit. At this point, I'm just keeping them around as spares for when the BP10s wear out. |
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