# any ideas on evaluating brake performance?



## dladd (Jun 1, 2011)

well, there are only two important parameters. Braking distance and feel. Braking distance would be fairly easy to test, just takes a little time and an empty stretch of road. Do a few repeated hard stops from 30 and 60 with and without boost, then again after seating the new pads.

Feel is even easier. Just drive for a while and see what you think.


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## DavidDymaxion (Dec 1, 2008)

Maybe a ruler and a video camera? Measure how far the pedal goes, video the speedo, and you could plot pedal distance traveled vs. stopping deceleration.

The fancy way to do it would be to put a load cell under your foot and directly measure pedal force.

How about an air cylinder that gets filled with various PSI of pressure, and measure the deceleration for the different pressures?



dtbaker said:


> I am trying to think how best to gather a little objective performance information on braking performance and effort without special equipment. I have ordered some 'sticky' high performance brake pads in hopes that I can get original performance WITHOUT vacuum.
> 
> I plan to compare current performance (with vacuum pump) and OEM pads, then change pads and turn off my vacuum pump and see how it feels.... but that is purely subjective. I can't really think of a way to 'measure' pedal effort other than by feel....


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## DavidDymaxion (Dec 1, 2008)

An objective binary measure would be if you can press hard enough to engage the antilock brakes (or skid the wheels) in both cases. On my gasser I could not engage the antilocks on dry pavement no matter how hard I pushed. With the Hawk HPS pads I can do it, so that proves I'm getting more braking force for less pedal force.


DavidDymaxion said:


> Maybe a ruler and a video camera? Measure how far the pedal goes, video the speedo, and you could plot pedal distance traveled vs. stopping deceleration.
> 
> The fancy way to do it would be to put a load cell under your foot and directly measure pedal force.
> 
> How about an air cylinder that gets filled with various PSI of pressure, and measure the deceleration for the different pressures?


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## GerhardRP (Nov 17, 2009)

dladd said:


> well, there are only two important parameters. Braking distance and feel. Braking distance would be fairly easy to test, just takes a little time and an empty stretch of road. Do a few repeated hard stops from 30 and 60 with and without boost, then again after seating the new pads.
> 
> Feel is even easier. Just drive for a while and see what you think.


If you have a GPS with logging capability, you can get pretty good deceleration numbers from that. Set it for maximum update rate.
I have a long hill steep nearby ... you could get a good feel for the brake system going down such a slope.
Gerhard


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## piotrsko (Dec 9, 2007)

throw a "t" in the system, drop a gauge on it and film it during the stops. you should need to have at least 1500 psi gauge.


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## Duncan (Dec 8, 2008)

Hi dtbaker

Here and in the UK every garage that does the annual (or biannual) inspection has rolling road brake testers,
My local guy will let me put my car on the rollers so that I can do some front/rear brake balance testing

If it is not part of the inspection don't you have a local brake shop that could do the same tests?


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## EVfun (Mar 14, 2010)

You're assuming we have inspections. In most states the only inspection a vehicle will have is a smog test every few years for the first 15 to 25 years of its life. Vehicle equipment failures are rarely the cause of accidents, it's almost always driver failure. 



Duncan said:


> Hi dtbaker
> 
> Here and in the UK every garage that does the annual (or biannual) inspection has rolling road brake testers,
> My local guy will let me put my car on the rollers so that I can do some front/rear brake balance testing
> ...


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## dtbaker (Jan 5, 2008)

Duncan said:


> Hi dtbaker
> 
> Here and in the UK every garage that does the annual (or biannual) inspection has rolling road brake testers,
> My local guy will let me put my car on the rollers so that I can do some front/rear brake balance testing
> ...



I don't think I've ever seen rolling brake test equipment to check balance.... the state I live in doesn't have ANY inspections of any kind. They check emissions in the biggest county in the state, but not the others.... I was really surprised when I re-registered my EV as electric they had NO visual inspection or safety guidelines.


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## hans j (Mar 31, 2008)

He is referring to a brake plate tester, http://www.platetronic.com/about.html. A local community college automotive program might have one?

Technically speaking, a manual brake master cylinder will have a larger bore to move more fluid with less effort. Power brake master cylinders have smaller bores due to the vacuum assist. Your brakes are going to feel hard no matter what pads you put in, even though they might stop.

If you can find a different application brake master cylinder with a larger bore it would be much easier. You might also be able to modify your brake pedal linkage to give it more leverage with the power brake master cylinder.

On my car, I was able to backdate to a manual master cylinder and also am using some old Hawk HPS pads I had laying around. I plan on putting on newer vented front rotors and a brake compound better suited for my weight and brake setup from Carbotech (they can custom make pads).


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## dtbaker (Jan 5, 2008)

hans j said:


> Technically speaking, a manual brake master cylinder will have a larger bore to move more fluid with less effort. Power brake master cylinders have smaller bores due to the vacuum assist.


the opposite is true.
smaller bore gives higher psi with same effort, but requires slightly longer stroke.

There are aftermarket masters with smaller 7/8" bores that might do the job (13/16" is stock in my Swift). but I haven't found any that have the three outlets positioned the same, which would mean significant work on brakeline re-routing. New brake masters are also pretty close to the cost of a typical vacuum pump+switch, which is what I would like to avoid in my next build if possible. I'd consider using a salvage master, but can't find any reasonably new vehicle with tandem master with 7/8" bore, nobody goes boosterless any more apparently.



hans j said:


> You might also be able to modify your brake pedal linkage to give it more leverage with the power brake master cylinder.


the Suzuki Swift pedals really don't have any extra meat on them to drill a higher hole for the pushrod for better leverage. Very little room even to weld on a tab because of the way the pedals are configured around the steering it would be a bitch of a job to pull the pedal assembly and even try this...



hans j said:


> On my car, I was able to backdate to a manual master cylinder and also am using some old Hawk HPS pads I had laying around. I plan on putting on newer vented front rotors and a brake compound better suited for my weight and brake setup from Carbotech (they can custom make pads).


I looked all the way back in previous years, and then different models and could not find a boosterless version for the Swift. I HAVE ordered Carbotech pads with AX6 compound to try.... thats what this test is all about.


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## hans j (Mar 31, 2008)

dtbaker said:


> the opposite is true.
> smaller bore gives higher psi with same effort, but requires slightly longer stroke.
> 
> There are aftermarket masters with smaller 7/8" bores that might do the job (13/16" is stock in my Swift). but I haven't found any that have the three outlets positioned the same, which would mean significant work on brakeline re-routing. New brake masters are also pretty close to the cost of a typical vacuum pump+switch, which is what I would like to avoid in my next build if possible. I'd consider using a salvage master, but can't find any reasonably new vehicle with tandem master with 7/8" bore, nobody goes boosterless any more apparently.


Oh yeah you are right, it's been a while since I looked it up. My manual brake setup uses 17mm and power brakes use 20mm. I still have my electric vacuum pump from my car if you need one. I pulled it out because the seal between the power booster and master cylinder was leaking so the pump ran all the time. And I could switch to manual brakes easy and save a little weight while I was at it.


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## tomofreno (Mar 3, 2009)

> throw a "t" in the system, drop a gauge on it and film it during the stops. you should need to have at least 1500 psi gauge.


 You could get real time feedback by mounting a webcam to view the gauge and watch the output on a laptop in the cab as you press the brake pedal to ensure you apply about the same pressure in the two tests.


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## dtbaker (Jan 5, 2008)

tomofreno said:


> You could get real time feedback by mounting a webcam to view the gauge and watch the output on a laptop in the cab as you press the brake pedal to ensure you apply about the same pressure in the two tests.



i *COULD*
but realistically... I'm unlikely to do more than change the pads and go by 'feel'. 


d


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## hans j (Mar 31, 2008)

I checked my boxes from Carbotech and I am running the AX6 compound on my track duty rabbit. Fantastic pad for me. Great cold performance, been really quiet and stops like crazy when warmed up!


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## Ziggythewiz (May 16, 2010)

Are these drum or disc brakes we're talking about?

I just upgraded my bug to disc and compared to before the stopping power is rediculous. I just hope whoever's behind me can stop on a dime as well.


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