Who's running 2 pot calipers front and rear? - LotusTalk - The Lotus Cars Community
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post #1 of 178 (permalink) Old 09-20-2017, 06:49 AM Thread Starter
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Who's running 2 pot calipers front and rear?

Hi,

I'm curious who's running the AP 2pot calipers in the front AND rear, and what the noticed changes are. I'm considering running the same caliper front and rear, likely XP 12/10 or 10/8, with no other changes (stock abs, stock brake booster). I wouldn't say I'm disappointed with the braking I have, but I'm curious to explore improvements, and I will be messing with the front calipers anyway... so I'm contemplating "while you're at it" possibilities.

1. What pads do you run front/rear?
2. Any brake drag experienced, and if so what did you do about it?
3. Any change in pedal travel?
4. Are you running the stock brake booster?
5. Are you running ABS?
6. Any negative surprises?
7. Largest benefits observed?

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post #2 of 178 (permalink) Old 09-20-2017, 07:18 AM
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I'm doing it and it's awesome.

1) CL8 front, CL6 rear
2) No drag
3) Yes, the pedal is a little longer but has more resolution... more accurate braking force
4) Yes
5) Yes
6) No... just that there is no e-brake if you don't make provisions for it. I used the EP Ultimate uprights. PS: I have 16mm EP dropped uprights that have the capability of having the 2 pots bolted to the front and the stock single pots on the rear that will allow you to keep your e-brake. I will sell them if there is interest.
7) Less ice-mode when driving aggressively (auto-x) and more resolution on the pedal for more controllable braking. It's rad.
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post #3 of 178 (permalink) Old 09-20-2017, 08:40 AM
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This topic is right on time as I am strongly considering adding a set of front calipers to the rear of my car. I've been worried about messing with the brake bias, not having much adjustment, and regretting the change. It seems pretty much everyone staggers the pads, so I am planning that as part of the upgrade. BOE's brake bias cage looks like it would solve the dilemma but $$$.

@glagola1 , would you comment on your brake bias observations?

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post #4 of 178 (permalink) Old 09-20-2017, 08:52 AM
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Matt is right with everything he said and suggested. Except 5, god no ABS EW. Also I gained 20 meters shorter stopping into 12 at COTA.

you do NEED more pad in the front IMO or this happens if you get aggressive:


I have the bias bar on now, will report back after the weekend.

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Last edited by kfennell; 09-20-2017 at 09:02 AM.
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post #5 of 178 (permalink) Old 09-20-2017, 09:48 AM
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Quote:
Originally Posted by Parko View Post
This topic is right on time as I am strongly considering adding a set of front calipers to the rear of my car. I've been worried about messing with the brake bias, not having much adjustment, and regretting the change. It seems pretty much everyone staggers the pads, so I am planning that as part of the upgrade. BOE's brake bias cage looks like it would solve the dilemma but $$$.

@glagola1 , would you comment on your brake bias observations?
Brake bias seems to be perfect with the pads I'm running. I wouldn't change it. CL8 might be a bit too aggressive on the street though. Works for what I do:

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post #6 of 178 (permalink) Old 09-20-2017, 10:24 AM
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Timely: https://www.lotustalk.com/forums/f232...raking-427602/

You won't regret ditching the stock rear sliders. The WORST braking I've head of is from BBK cars (Wilwood setup) and stock Lotus 4 pot fronts with stock rear sliders like on the 240 and up cars...

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post #7 of 178 (permalink) Old 09-20-2017, 12:52 PM Thread Starter
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Hi Phil, thanks for chiming in, I've already been out there. Did have one question for you though - is there ever a situation that makes sense to have radical up front, stock 2pot in back, but keep the stock brake booster? I'm guessing the stock brake booster probably doesn't configure well with brake changes on both ends but maybe some loonatic has already tried that and discovered otherwise. I understand the benefits of no boost on track, but I also want to be able to walk after my spouse and I do one of our road trips... so at this time looking to keep the stock booster.

On facebook I read a post from someone complaining about brake drag after this change- didn't seem it was an issue for all, but I do wonder what can be done if I put 2pot on the rear and was one of the "lucky" ones.

Quote:
Originally Posted by turbophil View Post
Timely: https://www.lotustalk.com/forums/f232...raking-427602/

You won't regret ditching the stock rear sliders. The WORST braking I've head of is from BBK cars (Wilwood setup) and stock Lotus 4 pot fronts with stock rear sliders like on the 240 and up cars...

-Phil

"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 #8 of 178 (permalink) Old 09-20-2017, 01:13 PM
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Originally Posted by jds62f View Post
Hi Phil, thanks for chiming in, I've already been out there. Did have one question for you though - is there ever a situation that makes sense to have radical up front, stock 2pot in back, but keep the stock brake booster? I'm guessing the stock brake booster probably doesn't configure well with brake changes on both ends but maybe some loonatic has already tried that and discovered otherwise. I understand the benefits of no boost on track, but I also want to be able to walk after my spouse and I do one of our road trips... so at this time looking to keep the stock booster.

On facebook I read a post from someone complaining about brake drag after this change- didn't seem it was an issue for all, but I do wonder what can be done if I put 2pot on the rear and was one of the "lucky" ones.
Theres nothing inherent that would lead to any drag with this system? Maybe their rear pads are hitting the hubs of a rear 2 piece rotor? They will not clear if you dont modify them.

Can you get difderent sized masters i wonder if its a big concern? Also mine is a little better in terms of pressure after a better bleed and getting the pressure a little higher in front.

2007 Exige S with almost every track mod...
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post #9 of 178 (permalink) Old 09-20-2017, 01:48 PM Thread Starter
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Can't speak to the FB post, although it did seem Phil had some knowledge of it. As far as different BMC goes, yes you can get different ones... I just want to minimize R&D time and maximize drive time. My overall goal is to focus far more on improving the nut behind- For "system components" I'm only interested in what works, not figuring out what works.


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Originally Posted by kfennell View Post
Theres nothing inherent that would lead to any drag with this system? Maybe their rear pads are hitting the hubs of a rear 2 piece rotor? They will not clear if you dont modify them.

Can you get difderent sized masters i wonder if its a big concern? Also mine is a little better in terms of pressure after a better bleed and getting the pressure a little higher in front.

"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 #10 of 178 (permalink) Old 09-20-2017, 01:51 PM
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Quote:
Originally Posted by kfennell View Post
Theres nothing inherent that would lead to any drag with this system? Maybe their rear pads are hitting the hubs of a rear 2 piece rotor? They will not clear if you dont modify them.

Can you get difderent sized masters i wonder if its a big concern? Also mine is a little better in terms of pressure after a better bleed and getting the pressure a little higher in front.
I'm also thinking about doing this over the winter. I do not have 2 piece rotors yet but will likely once my rotors need replaced. Seems odd to me that you need to modify the pads to clear in the rear as this is sold with a bracket made to fit. What 2 piece rotors are you using and are they a different size than the stock rotor in the rear?
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post #11 of 178 (permalink) Old 09-20-2017, 03:36 PM
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I'm also thinking about doing this over the winter. I do not have 2 piece rotors yet but will likely once my rotors need replaced. Seems odd to me that you need to modify the pads to clear in the rear as this is sold with a bracket made to fit. What 2 piece rotors are you using and are they a different size than the stock rotor in the rear?

Blackwatch's old 2 piece. They are different then stock the hub is larger and the ring smaller as the stock pads don't touch the first 1/8 of the rotor or so from the center so they got rd of it.

2007 Exige S with almost every track mod...
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post #12 of 178 (permalink) Old 12-01-2017, 11:39 AM Thread Starter
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One last bump, and question.

When implementing this solution, the brake calipers are mounted backward compared to how they mount in the front. Has this caused issue for anyone? (Such as getting bent slider pins)

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Last edited by jds62f; 12-01-2017 at 11:57 AM.
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post #13 of 178 (permalink) Old 12-01-2017, 11:48 AM
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You have to mount them on the opposite side so the bleed port is still up in case that isn't obvious...

2007 Exige S with almost every track mod...
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post #14 of 178 (permalink) Old 12-01-2017, 01:25 PM
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Anyone know how difficult it is to do this mod but retain the e-brake?

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post #15 of 178 (permalink) Old 12-01-2017, 01:44 PM
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Anyone know how difficult it is to do this mod but retain the e-brake?
If you don't mind the weight you can just leave the old e brakes attached only by the cable. In that case it is 100% easy.

Otherwise there are some lightweight e brakes you can buy that work with the existing cables easily.
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post #16 of 178 (permalink) Old 12-01-2017, 02:14 PM Thread Starter
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Originally Posted by kfennell View Post
You have to mount them on the opposite side so the bleed port is still up in case that isn't obvious...
I think that is what I'm assuming. Here is a picture from the BOE website, with the OEM rear caliper removed, and the arrow indicating the direction of the rotor. When the brakes are applied, the pads will want to slide in the same direction the rotor is going, which is opposite compared to how things operate on the front.



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post #17 of 178 (permalink) Old 12-01-2017, 02:24 PM
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Originally Posted by jds62f View Post
I think that is what I'm assuming. Here is a picture from the BOE website, with the OEM rear caliper removed, and the arrow indicating the direction of the rotor. When the brakes are applied, the pads will want to slide in the same direction the rotor is going, which is opposite compared to how things operate on the front.


Good observation, but they are symetrically designed so it doesn't matter

2007 Exige S with almost every track mod...
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post #18 of 178 (permalink) Old 12-01-2017, 02:56 PM
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I am doing the AP 2pot front and back...Seems to me to be the best bang for the buck
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post #19 of 178 (permalink) Old 12-01-2017, 03:45 PM
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I'm doing this modification this winter as well. I dropped off the 2 POT Calipers at BOE this week. I plan to run XP10 front and XP8 rear on the track and keep the emergency brake. I'll have to fill the hydraulic line with a bleed screw on the stock rear slide caliper. I've been running XP12 front and rear with the stock setup and it is not good on my short home track. (The brakes are basically analog.) This thread is making me wonder if I could run XP8 front and XP6 rear?

Andrew at BOE gave me a nice bit of advice, "use less brake";}
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post #20 of 178 (permalink) Old 12-01-2017, 03:47 PM
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Originally Posted by kfennell View Post
If you don't mind the weight you can just leave the old e brakes attached only by the cable. In that case it is 100% easy.
Thanks for the info, I think I'll do it that way. I want to try to keep it as close to stock as I can. I believe that, had Lotus known that the original rears were a bad idea with the 4-pot Cup BBK's, they would have probably moved the front to the rear and done something similar.

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