Question on brake bias and Carbotech pad options - LotusTalk - The Lotus Cars Community
 
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post #1 of 15 (permalink) Old 04-19-2016, 06:21 AM Thread Starter
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Question on brake bias and Carbotech pad options

I think it's time to stop using Porterfield R4s and switch to the Carbotech XP series. Hearing so many good things about the Carbotechs, and I like that they come pre-bedded.

The question is: What set-up for front and rear brakes? (And to be clear: This is for track driving, plus the 100+ miles of street driving, to and from the track.)

Sector recommends running the more aggressive pad (XP12) in the front, and the less aggressive pad (XP10) in the rear. I assume the same logic would apply to XP10s in front and XP8s in the rear. This set-up would seem to reinforce the car's leaning to an already pronounced front bias for braking.

Meanwhile, my service tech is having success with the opposite approach, running XP8s on the front and XP10s on the rear. The premise being this balances out a car that comes from the factory with too much front bias.

So what do folks think about the two schools of thought? I'm a competent but not particularly fast driver. I trail-brake appropriate corners, but I'm not interested in a set-up that's too much of a hand-full at the limit. My gut is telling me to go with XP8s or XP10s on all four wheels, yet it seems the staggered approach -- with more aggressive pads at the front -- is the favored approach among very fast drivers.

I have searched the forums and have found only one instance of an Elisetalker (Jasondew) putting the more aggressive pads on the back. Anyone else have experience with this type of set-up? To what degree does this really change driving dynamics? Thanks!

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post #2 of 15 (permalink) Old 04-19-2016, 06:30 AM
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I'm also very interested in this because I'm tinkering with the idea of switching to Carbotechs from my current Pagids, which I've been running for 10 years now.

If I die, my biggest fear is that my wife sells all my toys for the price I told her I bought them for...
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post #3 of 15 (permalink) Old 04-19-2016, 06:52 AM
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It depends on your brakes. I run XP10 front XP8 rear, but I have the 315mm front/330mm rear ap racing BBK. At one point, through a bit of confusion, I ended up with XP12 front and XP8 rear, and the fronts locked up way too quickly and induced ICE mode at the track. Some folks with OEM brakes run the higher compound in the rear and like it quite a bit, but I think those folks tend to have the 1-pot rears.

You could always start with the same compound front and rear and see how you like it and make a change at the track fairly easily. Tell your brake supplier what you're trying to do and they may help you on pricing.
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post #4 of 15 (permalink) Old 04-19-2016, 08:08 AM
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The 2008+ cars come with bigger calipers on the front, that may account for some of the variation you see.

It does seem that most vendors recommend a staggered approach on the cars with 2pot fronts. (12/10, 10/8, etc). I have gone that way, but unfortunately its all I've ever known. For sure putting more bias up front gives you less ability to trail brake.

I have also seen people recommending the more forward bias because they claim it helps/eliminates getting locked out of the rears, which can be an eye opening situation if you haven't experienced it (search ice mode). At some point in time I'm going to try even pads on f/r, but I bought well into the future last time sector had a sale :-)

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post #5 of 15 (permalink) Old 04-19-2016, 08:09 AM
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sorry for OT but how much does a set of pads cost you and how many events do they last?

Quote:
Originally Posted by acslater View Post
It depends on your brakes. I run XP10 front XP8 rear, but I have the 315mm front/330mm rear ap racing BBK. At one point, through a bit of confusion, I ended up with XP12 front and XP8 rear, and the fronts locked up way too quickly and induced ICE mode at the track. Some folks with OEM brakes run the higher compound in the rear and like it quite a bit, but I think those folks tend to have the 1-pot rears.

You could always start with the same compound front and rear and see how you like it and make a change at the track fairly easily. Tell your brake supplier what you're trying to do and they may help you on pricing.

"Give a man a match, and he'll be warm for a minute, but set him on fire, and he'll be warm for the rest of his life."
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post #6 of 15 (permalink) Old 04-19-2016, 08:36 AM
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Quote:
Originally Posted by jds62f View Post
sorry for OT but how much does a set of pads cost you and how many events do they last?
Last time I bought brakes, it was $199 for a pair of XP12, $188 for a pair of XP10, and $175 on the XP8s, all through KNS Brakes. I think 4-6 days is reasonable for me on a set. The fronts go much quicker than the rears...

Also, in my experience ICE mode will happen from locking up the fronts OR the rears too quickly. Keeping the bias balanced and utilitizing good brake modulation prevent it; so unfortunately, it's not a problem that can simply be solved by biasing more to the front.
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post #7 of 15 (permalink) Old 04-19-2016, 01:31 PM Thread Starter
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Quote:
Originally Posted by acslater View Post
Some folks with OEM brakes run the higher compound in the rear and like it quite a bit, but I think those folks tend to have the 1-pot rears.

You could always start with the same compound front and rear and see how you like it and make a change at the track fairly easily. Tell your brake supplier what you're trying to do and they may help you on pricing.
Yeah, I have the stock 1-pot rears. But your idea does make sense. I could put XP10s on all four corners, and give that a few sessions. Then swap out the front pads for XP8s, shifting bias more toward the rear. If the car goes nutso, I'd still have the XP10s to swap back in.

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post #8 of 15 (permalink) Old 04-19-2016, 01:43 PM
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Quote:
Originally Posted by JonOrangeElise View Post
Yeah, I have the stock 1-pot rears. But your idea does make sense. I could put XP10s on all four corners, and give that a few sessions. Then swap out the front pads for XP8s, shifting bias more toward the rear. If the car goes nutso, I'd still have the XP10s to swap back in.
What size rotors do you have on the front?
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post #9 of 15 (permalink) Old 04-19-2016, 01:46 PM Thread Starter
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What size rotors do you have on the front?
Car is 20 miles away, and I can't even remember the last rotors I put in! It's been so long because I took a multi-year hiatus from track days, and only drove the car infrequently (and gently) on city streets. But where are you going with the question? Thanks much.

2005 Chrome Orange Lotus Elise:
  • hard top, touring pack, HIDs, SJ Racing 15x7/16x8 track wheels
  • RTD Brace, Nitron 46mm Race Pro 1-Way, BOE oil pan
  • orange/black Lotus Sport trim shop seats, 6-point Schroth belts, Safety Solutions R3 Head & Neck Restraint System
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post #10 of 15 (permalink) Old 04-19-2016, 01:56 PM
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Quote:
Originally Posted by acslater View Post
It depends on your brakes. I run XP10 front XP8 rear, but I have the 315mm front/330mm rear ap racing BBK. At one point, through a bit of confusion, I ended up with XP12 front and XP8 rear, and the fronts locked up way too quickly and induced ICE mode at the track. Some folks with OEM brakes run the higher compound in the rear and like it quite a bit, but I think those folks tend to have the 1-pot rears.

You could always start with the same compound front and rear and see how you like it and make a change at the track fairly easily. Tell your brake supplier what you're trying to do and they may help you on pricing.
I have the same kit and am running more aggressive pads in the rear than the front. I had the Mintex Extremes on all four corners and the front bias was way too much for my liking.

San

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post #11 of 15 (permalink) Old 04-19-2016, 02:05 PM
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Originally Posted by oldmansan View Post
I have the same kit and am running more aggressive pads in the rear than the front. I had the Mintex Extremes on all four corners and the front bias was way too much for my liking.

San
I honestly hated the Mintex pads, they lasted me 2 track days before I wore through the fronts, and they overheated on me quite a bit - granted, it was 90+ degrees out for the 2 days I used them. The Carbotech feel better and are much more consistent, and I'd say the modulation is better, too - I almost never end up in the ABS with them unless I really want to.
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post #12 of 15 (permalink) Old 04-19-2016, 02:13 PM
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Quote:
Originally Posted by acslater View Post
I honestly hated the Mintex pads, they lasted me 2 track days before I wore through the fronts, and they overheated on me quite a bit - granted, it was 90+ degrees out for the 2 days I used them. The Carbotech feel better and are much more consistent, and I'd say the modulation is better, too - I almost never end up in the ABS with them unless I really want to.
I'm running the Mintex in the rear and the Carbotech Bobcats in the front. No track, just canyons.

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post #13 of 15 (permalink) Old 04-19-2016, 02:16 PM
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Quote:
Originally Posted by JonOrangeElise View Post
Car is 20 miles away, and I can't even remember the last rotors I put in! It's been so long because I took a multi-year hiatus from track days, and only drove the car infrequently (and gently) on city streets. But where are you going with the question? Thanks much.
larger rotor size = more leverage

Don't forget to flush your brake fluid, too - I highly suggest Endless RF-650 or Castrol SRF
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post #14 of 15 (permalink) Old 04-19-2016, 04:13 PM
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Quote:
Originally Posted by JonOrangeElise View Post
Car is 20 miles away, and I can't even remember the last rotors I put in! It's been so long because I took a multi-year hiatus from track days, and only drove the car infrequently (and gently) on city streets. But where are you going with the question? Thanks much.
If you have 288mm front and rear with single pot on the rear, you might like same front and rear pads. If you have 308 front and 288 rear with single pot on the rear, you are going to definitely want more rear pad.

Remember that a single pot caliper loses about 20-40% braking force over a dual pot caliper. The loss is in the friction trying to move the caliper while under braking load.

Later,
Eldon
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post #15 of 15 (permalink) Old 04-19-2016, 04:40 PM
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I'm also in the same boat, car is almost complete sans brakes. I've decided to go with Carbotechs but not sure which size. The rotors will also be switched out to something far lighter.
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