Pads for high speed track use on sticky tires - LotusTalk - The Lotus Cars Community
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post #1 of 24 (permalink) Old 03-02-2016, 06:02 AM Thread Starter
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Pads for high speed track use on sticky tires

So I am getting to the point where even on my small local track braking from 105-60 I am getting some brake fade on CL5+/6 pads. I am scheduled to run at COTA where I need to brake from 140-60 roughly so I would like to be more confident. What is a good pad for this application using the DBA4000 rotors and stock calipers with Motul RBF600 fluid. I am thinking XP12/10, but can I go to an even higher model or is the initial bite too hard? I will only be using these pads at track days on the higher speed tracks.

I just started running P Zero Trofeo R in 225/50/15 and 255/40/17 and since I changed tires I have felt that the brakes are no longer strong enough and are fading fast.
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post #2 of 24 (permalink) Old 03-02-2016, 06:18 AM
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turning it to 11 would be raybestos st45/st47 or xp10/12
you might try rc6 front rc8 rear

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post #3 of 24 (permalink) Old 03-02-2016, 07:08 AM Thread Starter
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Why more braking in the back I also didnt mention but I have the ABS off at my normal track because it is so bumpy, I was thinking I needed less in the back as I am more often locking the rears then the front currently.
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post #4 of 24 (permalink) Old 03-02-2016, 07:20 AM
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What do you have as far as rotors and calipers? If you have 308mm fronts and 288mm rears, the car has too much front bias. That is why Dallas suggested RC6 fronts and RC8 rears.
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post #5 of 24 (permalink) Old 03-02-2016, 07:55 AM Thread Starter
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Quote:
Originally Posted by eldonz View Post
What do you have as far as rotors and calipers? If you have 308mm fronts and 288mm rears, the car has too much front bias. That is why Dallas suggested RC6 fronts and RC8 rears.
All exige stock
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post #6 of 24 (permalink) Old 03-02-2016, 08:13 AM
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Why more braking in the back I also didnt mention but I have the ABS off at my normal track because it is so bumpy, I was thinking I needed less in the back as I am more often locking the rears then the front currently.
YMMV My experience is the car needs more rear bias. I run ST43 front ST45 rear with the ABS on and everything works great, no ice mode. I do substantially more autox than track but do participate in both.

I am going to try rc6 front st45 rear at some point as I think the rc6 are pretty much the same deal friction wise as the ST43 without bedding needed and possibly less rotor wear.

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post #7 of 24 (permalink) Old 03-02-2016, 08:20 AM
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So, I am going to assume that you have 308mm fronts and 288mm rears and that you have 4pot APs front calipers and single pot rear calipers. The only time I have had brake fade with CLs is when they were getting low on pad and transferring too much heat to the brake fluid. On the race car, I will switch the pads out once they get to about half the material left for this reason. I was using XP10s last weekend at Road Atlanta and on the back straight you get to over 140MPH and have to brake for a 3rd gear corner. I ran one session for about 45+ mins and felt that a little more aggressive pad would have been nice. It was taking some pedal pressure to slow the car down. Now the pads never faded but I think for a long session like this I might have been nearing the upper temp limit of the pad. If you switch to CL8s, I believe that you will find that you will not have any pad fade. I believe the problem is that nobody stocks CL8s for the 4pot AP calipers.

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post #8 of 24 (permalink) Old 03-02-2016, 08:47 PM
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Speaking of the Carbotech pads: Is this correct> it is better to have a higher grade pad in the front and lower in the rear? e.g. XP12 front and XP 10 or 8 rear. Is the reasoning that the rear will warm up faster and provide more bite and thus reduce front bias?

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post #9 of 24 (permalink) Old 03-02-2016, 09:54 PM
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Quote:
Originally Posted by kfennell View Post
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That doesn't mean anything since things changed since 2008 and on.
2008+ ones have 308mm AP fronts while the 06/07 Exige had the same brake setup as Elise.

So, what brakes do you have?

With that said, I have XP12 fronts and I like them. I'll be installing XP10 in the rear as well soon since my rears are worn.

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post #10 of 24 (permalink) Old 03-03-2016, 05:05 AM
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Put the pads with higher friction coefficient in the rear if you want more rear bias. From the factory they are a bit overkill on the front bias.
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post #11 of 24 (permalink) Old 03-03-2016, 12:21 PM
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Do the XP10s have the higher friction coefficient over the XP12s?

If so then a more streetable setup would be XP10 front and XP8 rear correct?

Is it true that the stock Exige S240 AP racing calipers (2008+)
use a Pagid RS14 "black"? If so what other pad is similar only with
a higher fade resistant rating?

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post #12 of 24 (permalink) Old 03-03-2016, 12:34 PM
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Don't know never used them
I would expect the higher number is the higher friction but that might also make too much sense LOL

I am thinking at the least Hawk and Porterfield/Raybestos/Wilwood have charts online that show friction at various temperatures.

The wilwood compounds are the same as raybestos but under a different name. I can't remember off hand what = what for sure but if I had to guess of the top of my head ST47 is the same deal as compound A, ST45=H, etc. . anyway heres an example:

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post #13 of 24 (permalink) Old 06-28-2016, 04:36 PM
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Maybe I should add an update.
I have stock setup, AP 308mm fronts with R888.
I went from XP12 fronts with stock rear pads to XP12 fronts with XP10 rear pads, and I've been hitting ice mode more often than I used to(which was rare). I think I'll tone the rears down to XP8 or just go back to stock rears as I still had half of its life left.

The bite is supreme and the stopping force is impressive, but I feel too much isn't always the answer.

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post #14 of 24 (permalink) Old 06-28-2016, 05:49 PM Thread Starter
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Quote:
Originally Posted by forkmeupscotty View Post
Maybe I should add an update.
I have stock setup, AP 308mm fronts with R888.
I went from XP12 fronts with stock rear pads to XP12 fronts with XP10 rear pads, and I've been hitting ice mode more often than I used to(which was rare). I think I'll tone the rears down to XP8 or just go back to stock rears as I still had half of its life left.

The bite is supreme and the stopping force is impressive, but I feel too much isn't always the answer.

I ran CL6 all around with R7's at COTA last time out and brakes did not seem to be an issue, not sure what changed there apart from maybe the large brake zones are further apart on that track? But I did not encounter much fade. I am going to run 6 front 8 rear next time out in sept just because...
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post #15 of 24 (permalink) Old 06-28-2016, 10:45 PM
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As others have said the bias is all wrong.

Lotus marketing got the better of the engineering with those big brakes.

The bias was already too forward with the stock 2 front and 1 rear pot with equal size rotors. It wasn't terrible, but not great. Then marketing put 4 pot AND bigger rotors up front. So now you're like 80/20 brake bias. Not cool. People brag about that car stopping good... I guess. They stop really good, slowly. Junk for the track, in my view.

Move some 44mm 2 pots to the rear and the world will start making sense again for the cup and BBK guys.

Short of a new/correct caliper configuration, the "fastest" brakes lotus made were the "standard" calipers with equal rotor sizes on all 4s with the correct pads for the application, ft and rr...

Want to make improvements after that, better measure twice and buy once if you really hope to make an improvement...

More than likely using too much brake due to small balls (confidence issues), lack of aero, lack of tire, bad setup, or some combination of the above...

-Phil
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post #16 of 24 (permalink) Old 06-29-2016, 06:36 AM
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Quote:
Originally Posted by kfennell View Post
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We ran XP12 front XP10 rear is SCCA & Lotus Cup racing with stock sized brakes. This is a great set-up for several reasons: great bite, excellent trail braking, great feel and easy on the rotors. The CL pads have great bite but do eat up the rotors. Unless you are running a lot more power than stock, I would be surprised if you really needed more aggressive pads than XP12/10. Remember to keep your fluid fresh and bled.

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post #17 of 24 (permalink) Old 06-30-2016, 06:06 AM
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What would you suggest if you ARE pushing more power, like big SC power? Change rear brakes to what? What pads?
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post #18 of 24 (permalink) Old 06-30-2016, 07:45 AM
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Quote:
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What would you suggest if you ARE pushing more power, like big SC power? Change rear brakes to what? What pads?
The real problem is trying to get the balance correct. Once this is achieved then it is a matter of matching the pads to the braking style of the driver. If the driver over-brakes for corners because of lack of confidence in the cornering capability of the car then you are going to need a higher heat range pad. If the track has long straights followed by tight corners then higher heat range pads are needed. It is common to change pad types based on track and driver preferences.

So, what I am saying is that nobody is going to be able to answer your question based on the little bit of information that you have provided.

Later,
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post #19 of 24 (permalink) Old 06-30-2016, 08:27 AM
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For standard brakes and for the track, you run your favorite pad on all 4 corners. CL RC6 is a nice pad, as are others that are in the middle of their respective range, DTC60, etc...

The real deal is this and it's one of those "if you have to ask" things. When the driving expertise gets to the point where you're very aware of your trail brake and so forth, you start playing with pads...

But start in a place where you can pad up or pad down on either end of the car as your braking style changes.

Generally, the standard brakes are the fastest brakes and have the best balance. They're basically 60/40. Something close to 55/45 or even 50/50 depending on the car setup is really nice for an experienced driver...

The 240/cup and BBK cars are really tough with 70/30 or worse natural bias to the front. So those tend to do better with stronger/grippier pads in the rear for sure to help bring that bias closer to something that could be fast. An RC6 front and RC8 rear would help... Could probably even run an Rc5 in the front on those cars! lol. You really just need to play with it until you find your comfort zone and where you get the best laptimes and most controllable braking car. You want to err on the side of front bias regardless. The more front bias, the "safer" or easier the car is to drive, but it's also a slower car into corners...

-Phil


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Last edited by turbophil; 06-30-2016 at 09:48 AM.
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post #20 of 24 (permalink) Old 06-30-2016, 02:54 PM
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For disclosure, I've got several years on track experience with M3s across two generations, and run bmwcca advanced group. I'm getting into a Lotus for the first time, and it's one that Phil built, so it's got some power, but I believe the brakes are stock. In my experience with other track forum sections from other makes there are usually a few 'known good' combos of pads or pad/rotor upgrades on the market, so I was just looking for some experience. Saying "it depends", while of course it does, isn't terrifically helpful to someone new to the platform.
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