Piecha/Sprint Booster-like device for brakes? Brake tuning? - Mercedes Benz SLK Forum

Performance MODS for the R171 Tuning and Performance modifications for your SLK

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#1 Old 10-17-2015
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Unhappy Piecha/Sprint Booster-like device for brakes? Brake tuning?

Two things that bother me about the SLK is its slow response to accelerator and brake pedals. There is a fix for the accelerator, is there a similar fix for the brakes? When I hit the brakes I want them to start braking NOW, not after I've pushed them half way to the floor. Pads are fairly new, as is brake fluid. It's not that they don't start engaging right away, it's that they don't engage enough. I want them "grabbier".

Any suggestions? Adjustments? After market products other than brake upgrades?
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#2 Old 10-17-2015
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The accelerator pedal is connected with the ECU with a wire. The "fix" for the slow response is a device that amplifies this signal, thus fooling the ECU by letting it think you pushed in the pedal more. Same result btw can be achieved by just doing that, pushing in the pedal more, but let's not start that discussion again.
Brakes are a whole different story as you can imagine. There is no easy or cheap fix for this afaik. If you're not satisfied with the brakes as they are than the only remedy is a brake upgrade with kits from Brembo or Stopptech i.e.
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#3 Old 10-17-2015
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As noted, the only solution for brakes is to upgrade components. But you already have "drilled" rotors (actually cast in place on M-B parts) and four-piston calipers up front, if I'm not mistaken. That's a pretty good foundation. Mercedes OE pads are quite soft, and so have good initial bite but create a lot of dust. Aftermarket pads like Akebono or Green/Yellow/Red stuff typically don't bite as fast but are better able to tolerate high temperatures such as that seen in track use. So your solution may not actually lie with the brakes...it may be tires instead. What are you running now? Unless it is something like the Michelin Sport Cup, there is always a softer, grippier, shorter-wearing tire out there as an option.
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#4 Old 10-17-2015
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I volunteer that you may well have something wrong with your brakes - air in the system, faulty servo or poor friction pads.

If as you say, the brakes only engage after pedal is half depressed, sounds very like some air in there.

The SLK brakes are no worse than any other car of its type in that it is classed as a small sports car where the feel of driving is inbuilt. Be careful with larger brake kits, they are not the panacea to everything and lead to brake grabbing and can suffer from brake squeel if they are too big for the car.
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#5 Old 10-18-2015
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I realize that the gas pedal is electronic and by wire and I did not believe there was an electronic fix for the brakes but hoped that possibly some company made some kind of mod like a booster, or something. I'm not racing the car and am not concerned with absolute stopping power. I'm concerned about the brakes engaging more fully once the pedal is depressed. I'm guessing that M-B didn't want that for the average customer, just as it didn't want a quick gas pedal response. If M-B pads are grabbier then replacing them with something else will only make the matter worse. I don't believe that there is any inherent adjustability or my excellent mechanic would have done so. I guess it's something that I'll have to live with.

Thanks for the responses
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#6 Old 10-22-2015
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I swapped out the brakelines with the steelbraided kind. The brakes are not as mushy and I get better brake feel. And like someone said above use higher temp rated brake fluid to help eliminate brake fading.
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#7 Old 10-23-2015
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I swapped out the brakelines with the steelbraided kind. The brakes are not as mushy and I get better brake feel. And like someone said above use higher temp rated brake fluid to help eliminate brake fading.
As already noted, the pad material can make a difference in how the brakes feel and how quickly the pads start to slow the movement of the car. Stock OEM pads are typically the softest and most responsive. There is a huge aftermarket of pads with all kinds of pad composition. Many aftermarket pads that are designed to give long life will be much harder than stock pads and will be less responsive to initial brake application.

Replacement of the stock rubber brake lines can make a noticeable difference in the feel of the brakes. Old rubber lines can swell as the hydraulic pressure increases as the pedal is depressed. Other than different pads and stainless steel braided brake lines, there is little that can be done. Remember, that the movement of the brake pedal equates to a relatively small movement at the calipers. There is a lot of leverage between the brake pedal and the caliper. Brake pads only move a fraction of a millimeter from disengaged to fully engaged. If the amount of pedal movement is decreased, you would likely risk the pads not fully disengaging when the pedal is released.

For any brake system the brake fluid has to be fresh, the steel and rubber brake lines can not be compromised, rotors can't be glazed, floating calipers must move freely, pads must move freely, and the caliper piston(s) can not be restricted in it's movement. That's a lot of variables and any or a combination that are not functioning properly can greatly impact the effectiveness of the brakes.

Hope that helps.
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#8 Old 10-23-2015
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For daily driving or track use?

A downside of steel brake lines is that they can corrode in areas with salt (in air or on roads). I put them on my Caterham Super Seven and it did make a big difference.
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#9 Old 10-23-2015
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For daily driving or track use?

A downside of steel brake lines is that they can corrode in areas with salt (in air or on roads). I put them on my Caterham Super Seven and it did make a big difference.
Daily driving with some track use. I haven't noticed corrosion yet but I live in L.A. and the car is parked in the garage mostly. I do have them on my motorcycles as well and have not noticed corrosion on them either.
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#10 Old 10-23-2015
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I had braided stainless lines on my old 190E 16v and they did improve brake feel. I'm thinking about them for Sunhilde, too (any suggestions for possible vendors?). The inside of the lines are teflon, so that certainly won't corrode. The stainless won't either, unless you're driving all winter where they dump a lot of salt on the roads (and I hope you don't drive your SLK in those conditions).
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#11 Old 10-24-2015
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I had braided stainless lines on my old 190E 16v and they did improve brake feel. I'm thinking about them for Sunhilde, too (any suggestions for possible vendors?). The inside of the lines are teflon, so that certainly won't corrode. The stainless won't either, unless you're driving all winter where they dump a lot of salt on the roads (and I hope you don't drive your SLK in those conditions).
Vividracing.com they are in Arizona. Great customer service.
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#12 Old 10-24-2015
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StopTech has a set and it looks like that is what Vivid Racing carries.
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