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Discussion Starter #1
I find the initial bite and sensitivity of the stock NA Elise/Exige brakes too sharp for ease of modulation on track so I disconnect the booster (see pic).

I am using PFC11 in front and PFC08, stock AP 2-pots in the front (2006) and stock Brembo combos in the rear.

Does anyone else do this routinely?

Thanks!
1259497
 

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I'd be curious to know what tires you're on and what your peak longitudinal g's are with this method.
 

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Discussion Starter #5
Does this also reduce the travel of the brake pedal before it bites hard?
This certainly makes the brake travel seem shorter, but I think this is an illusion, because nothing else is changed in the braking system. I imagine that when I am fully on the brakes the travel is the same, but I am not 100% sure. You do lose that "snatch" of the pedal from your foot that the booster does. You can get on the brakes more progressively and get off more smoothly. Rotation is still pretty gentle under trail-braking given the strong front-brake bias.

I'd be curious to know what tires you're on and what your peak longitudinal g's are with this method.
I was using R888Rs (stock sizes and stock LSS wheels) and, sorry, I do not have logs of deceleration g's yet. I can however engage the ABS, and that is likely all you need to know. I did not try without ABS but I expect to be able to lock 'em up.

Important note: the brakes are much less effective when they are cold, so I do not do this on the street (I actually apply the brakes for 20m or so while still on throttle in the pit-lane to pre-heat).

Also notable: I find heel-and-toe rev matching much more precise with these brakes because I am not having to baby the brake pedal.
 

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I was wondering if this could be done. Any safety concerns, other than the increased leg pressure needed to get to the same braking effort?
 

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Discussion Starter #7
I don't believe there are safety issues on track. I would not recommend for use on the street given that the pads need to be hot to really work, although maybe with street pads it would be just fine. There seems to me to be no real advantage for street driving. It does take more time to get to max brake pressure.

I can lock the wheels without the booster, so I can get max stopping for the tires, just like for the boosted brakes.
 

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Hey thebuzzard,

I finally got around to trying this, and I'm very happy with the pedal feel. Your disclaimer is a very good idea, as different pads will yield different results.

I've got DBA XP650 pads, a pretty aggressive street/track compound, and with dead cold pads there is no issue whatsoever with stopping power. The absolute best thing about doing this is that it eliminates the initial touchiness/grab of the pads, the "snatch" you mentioned. Honestly, I don't think the pedal effort is any higher; it just yields a more linear, honest response. Better control harmony overall...much more consistent with the steering & shifter.
 

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Discussion Starter #9
@rightrudder Many thanks for the report-back on your experience. It is nice to get some confirmation that I am not missing something fundamental.

Your statement: "Better control harmony overall...much more consistent with the steering & shifter." is exactly what I found; it is likely not immediately obvious that this would be a "side-effect" but I found I could brake all the way to the apex if needed.
 

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I'm curious if this would also reduce the tendency for "ice mode" (a misnomer that just means the ABS detects a higher-than-expected rate of slip and pulls out all braking pressure).

I love the pedal feel without the booster, but I run EBC yellows. I do a bit of mountain driving, so a cooler-biting pad is good to have. On track they warm up really nicely and the bite is very good hot, so it may definitely be worth a [careful] try.
 

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Discussion Starter #11
The best place to try is for sure the track. I use a couple of rubber caps to disconnect the booster on track, and then I reconnect for the street. I do feel the ABS kick in without the booster and it is much easier to feel the buzz at the pedal.

I subscribe to your description of ice-mode (but I'm not sure everyone does). I've felt it when testing a friend's 15/17 setup with Hoosiers on a totally stock S2. It feels a lot like the booster is gone too. This has to be an ABS-related phenomenon, so I expect it may still occur. I don't know.

I wonder if anyone has tried a Bosch Motorsports ABS unit?

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The best place to try is for sure the track. I use a couple of rubber caps to disconnect the booster on track, and then I reconnect for the street. I do feel the ABS kick in without the booster and it is much easier to feel the buzz at the pedal.

I subscribe to your description of ice-mode (but I'm not sure everyone does). I've felt it when testing a friend's 15/17 setup with Hoosiers on a totally stock S2. It feels a lot like the booster is gone too. This has to be an ABS-related phenomenon, so I expect it may still occur. I don't know.

I wonder if anyone has tried a Bosch Motorsports ABS unit?

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There are a couple of us that have the Bosch Motorsports ABS on our cars. Since the virus has hit, I have not had a chance to try mine.

Later,
Eldon
 

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I wonder if anyone has tried a Bosch Motorsports ABS unit?
I calibrated the Bosch unit for some World Challenge teams shortly before I left Bosch several years ago. I'd give my left nut for one. At least the Bosch units (and my extension I am assuming the Lotus one) use both slip and rate of slip in the logic, so anything that changes rate of slip (more aggressive pads, more brake boost, tire grip/weight, wheel weight, rolling diameter, etc) can really screw with how well the ABS is able to hold the tire on just the right threshold of slip. Sometimes though, you get a "negative times a negative is a positive" scenario, that's where I'm curious if less boost could help with an otherwise aggressive setup. I saw some weird things when teams played with brake booster, but race ABS is trying to thread through a much finer needle.
 

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Discussion Starter #14
I calibrated the Bosch unit for some World Challenge teams shortly before I left Bosch several years ago. I'd give my left nut for one. At least the Bosch units (and my extension I am assuming the Lotus one) use both slip and rate of slip in the logic, so anything that changes rate of slip (more aggressive pads, more brake boost, tire grip/weight, wheel weight, rolling diameter, etc) can really screw with how well the ABS is able to hold the tire on just the right threshold of slip. Sometimes though, you get a "negative times a negative is a positive" scenario, that's where I'm curious if less boost could help with an otherwise aggressive setup. I saw some weird things when teams played with brake booster, but race ABS is trying to thread through a much finer needle.
@cyow5 so you really know these ABS units. :) I am an amateur.

Does the braking go to zero in ice-mode until released and reapplied?

Thanks for the info!

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@cyow5 so you really know these ABS units. :) I am an amateur.

Does the braking go to zero in ice-mode until released and reapplied?

Thanks for the info!

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I’m far from an expert in the Lotus unit since I just have to draw assumptions from the M4. I know the general theory very well though

ice mode isn’t completely zero, just massively diminished. Having experienced it myself, I still stopped but that just happened in the middle of the intersection, haha. I do think that letting off would reset it, but I didn’t try. Instead, I avoid driving on old R888s around freezing

The idea is that locked tires can’t steer - it is safer to pick your target instead of just hitting something or someone randomly.
 

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Discussion Starter #16 (Edited)
I’m far from an expert in the Lotus unit since I just have to draw assumptions from the M4. I know the general theory very well though

ice mode isn’t completely zero, just massively diminished. Having experienced it myself, I still stopped but that just happened in the middle of the intersection, haha. I do think that letting off would reset it, but I didn’t try. Instead, I avoid driving on old R888s around freezing

The idea is that locked tires can’t steer - it is safer to pick your target instead of just hitting something or someone randomly.
Yeeea, that is what I felt for ice-mode on track at MSR in TX. I did release and reapply and got my brakes back (the weight transfer I guess just pushed it over the edge). I would have been in proper trouble if I had not done that. ?

Whew on what seems to have been a nasty experience at that intersection (we could start a whole thread on near misses I bet). I am glad you and you Lotus are well!

I bet your experience with the M4 is very relevant given that a few have pitched-in that they are running or will run the Bosch Motorsport ABS and that is seems you have seen the code/know the algos most ABS are using.

I just stick with no-ABS on the race car; it keeps me honest, conservative, WIDE-awake and humbles me every track/race day ;)
 

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I've had Ice Mode on track and the street. On track, I can tell you that you have to let up on the pedal a little bit then the pedal will come back to normal. I removed the ABS on the S260 because if you don't, you have to learn to drive around it and that creates bad habits. Also, on the street, I almost hit a car that pulled out in front of me because I triggered Ice Mode.

Later,
Eldon
 

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Looks like I'm going to try two things (ABS disconnect and vacuum disconnect). Noice.
 

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This may have been covered before, but what's the easiest way to disconnect the ABS on my 2006 Elise?
I too have had the joy of ICE mode, would like to avoid those hair rising moments.?
 
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