# Power brakes needed?



## dtbaker (Jan 5, 2008)

tido said:


> Are the power brakes needed?
> 
> I am going to convert a miata and keep it very light (not more than 100lbs heavier than original).
> Has anyone done it?



well, un-hook the vacuum assist and see how you like it. My guess is that it will be a bit stiffer than you are going to feel good about to make a hard panic stop if you need to.

I am exploring alternatives myself for (my second) Suzuki Swift. Trying to find the stickiest brake pads I can to see if that will be enough.... and/or considering switching the brake master cyl to a smaller bore; BUT this won't be much less expensive than going to usual vacuum pump and switch route.


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## bruceme (Dec 10, 2008)

I've often wondered why cars have brake boost at all. I can stop a 6,000 lbs. aircraft from 100mph to zero in 1,500' using my tippy-toes alone and hydraulic leverage.

-Bruce


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## dtbaker (Jan 5, 2008)

bruceme said:


> I've often wondered why cars have brake boost at all. I can stop a 6,000 lbs. aircraft from 100mph to zero in 1,500' using my tippy-toes alone and hydraulic leverage.
> 
> -Bruce



most people want to stop a car in less than 1500' . 

seriously.... with drum brakes, which are somewhat 'self-energizing', it takes less effort for the same stopping power, BUT repeat use creates heat that doesn't dissapate well, giving brake 'fade'. Disc brakes are less prone to fade, but require more force (or same force and more travel of pedal to move same hydraulic fluid).... very delicate balance between performance and acceptable 'feel' and force required. Then you have to consider your driver; a conditioned male athlete, or a 15 yr old girl.... etc.


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## tido (Sep 20, 2011)

Thanks for the replies!

I guess I will try to find a not so expensive pump


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## dtbaker (Jan 5, 2008)

tido said:


> Thanks for the replies!
> 
> I guess I will try to find a not so expensive pump



unfortunately, the vacuum pump and switch is not a place you want to scrimp if you want reliability. The Gast pump and square D switch have proven effective, but are a bit expensive and takes a couple extra hours to pump all that in that would be nice to avoid.


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## tido (Sep 20, 2011)

dtbaker said:


> unfortunately, the vacuum pump and switch is not a place you want to scrimp if you want reliability. The Gast pump and square D switch have proven effective, but are a bit expensive and takes a couple extra hours to pump all that in that would be nice to avoid.


Of course but I got a quote for a pump: 468$CA... I think I could find a better deal...


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## dtbaker (Jan 5, 2008)

the vacuum kits do get expensive... $300-400 for all the stuff. This is why I am exploring the possibility of a smaller bore master cyl that will run closer to $100-150, but I am having a hard time finding one that won't require some significant brakeline re-working as the outlet ports are in different locations.


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## tido (Sep 20, 2011)

I have found a brake system that would cost about 5$. I only need to extract it from the original vehicule:

http://image.made-in-china.com/2f0j00fvnamZHRZibL/3-Ski-Snow-Bike-LW06-.jpg


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## PTCruisin (Nov 19, 2009)

tido said:


> Of course but I got a quote for a pump: 468$CA... I think I could find a better deal...



I was fortunate to find a Volvo vacuum pump for $100 and a vacuum switch for $35. I added a $4 12V relay and used the original vacuum hose and check valve. I also bought a $25 vacuum gauge to set the switch and ended up leaving it plumbed in. The system has worked flawlessly for over 3000 miles. The pump runs about 5 seconds when I press the brakes.

I drove the car without vacuum assist brakes for about 6 months and just got tired of having to stand on the brake pedal to stop the car. It actually brakes better now then when it was an ICE vehicle.

Shop around. You can find better deals. Look at Cloud Electric for the $35 vacuum switch. I bought the pump from Dimitri at Clean Power Auto. but I think it was the last one he had in inventory.


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## tido (Sep 20, 2011)

PTCruisin said:


> I was fortunate to find a Volvo vacuum pump for $100 and a vacuum switch for $35. I added a $4 12V relay and used the original vacuum hose and check valve. I also bought a $25 vacuum gauge to set the switch and ended up leaving it plumbed in. The system has worked flawlessly for over 3000 miles. The pump runs about 5 seconds when I press the brakes.
> 
> I drove the car without vacuum assist brakes for about 6 months and just got tired of having to stand on the brake pedal to stop the car. It actually brakes better now then when it was an ICE vehicle.
> 
> Shop around. You can find better deals. Look at Cloud Electric for the $35 vacuum switch. I bought the pump from Dimitri at Clean Power Auto. but I think it was the last one he had in inventory.


Are there vacuum pumps made for conventional cars? I mean are there some cars that uses this as you specified you have a volvo pump... If so I would check the scrapyard...


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## dtbaker (Jan 5, 2008)

PTCruisin said:


> I was fortunate to find a Volvo vacuum pump for $100



hhhmmm, do you have year/model it came from? I wonder if rockAuto.com or other auto parts vendor has them for cheap?


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## PTCruisin (Nov 19, 2009)

I'll try to get a picture and model number for the pump posted tomorrow. I'm heading for bed now.

Ralph


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## aeroscott (Jan 5, 2008)

Mercedes E class , maybe all models have a vacuum pump since about 1986 on to run the door locks . located in a foam box under the rear passenger seat .


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## favguy (May 2, 2008)

Lots of newer cars use electric vacuum pumps for the oem brakes, these are a good option as they usually run very quietly.

However, do not consider using a central door locking pump under any circumstances for brakes, they are not designed to pull and hold a vacuum as needed for a brake servo and will fail in short order, even if you can get one to work at all in this application


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## Yabert (Feb 7, 2010)

In my Smart fortwo (-900kg), I has try to use the brake without vacuum help and the result was not really adequate. It was hard for me to stop the car and definitely too hard for my girlfriend.

I flirt with the idea to use a vacuum door lock pump from my old Mercedes 190 1986, but I finaly try this (that will interest you dtbaker):

I did another hole on the brake arm to increase my leg torque (force to the cylinder). Just 1/2" from the center of the original hole. Theorically that give me 25% more level and that seem just enough to confortably feel when the brake is use.


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## tido (Sep 20, 2011)

Yabert said:


> In my Smart fortwo (-900kg), I has try to use the brake without vacuum help and the result was not really adequate. It was hard for me to stop the car and definitely too hard for my girlfriend.
> 
> I flirt with the idea to use a vacuum door lock pump from my old Mercedes 190 1986, but I finaly try this (that will interest you dtbaker):
> 
> I did another hole on the brake arm to increase my leg torque (force to the cylinder). Just 1/2" from the center of the original hole. Theorically that give me 25% more level and that seem just enough to confortably feel when the brake is use.




Interesting.... How does your girlfriend feel about your braking system when using it? (sounds almost right)


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## Yabert (Feb 7, 2010)

tido said:


> Interesting.... How does your girlfriend feel about your braking system when using it? (sounds almost right)


Enough comfortable to don't cause any trouble even if she drove in sandal.
But she tell me than the brake is harder to apply compare to his car (with power brake).


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## tido (Sep 20, 2011)

Yabert said:


> Enough comfortable to don't cause any trouble even if she drove in sandal.
> But she tell me than the brake is harder to apply compare to his car (with power brake).


I just sent you an pm (not related to this topic)

but I will probably try to do the same as you did and see how it goes.

Would this kind of modification (not using power brake) pass a SAAQ test?


Edit:
Oops I just realised that wasn't a pm I sent you but I wrote this on your profile "wall"


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## dtbaker (Jan 5, 2008)

I don't see a way to move the pushrod hole without changing the angle of the pushrod significantly... I am afraid it would bind/wear quickly that far off original center. you have no issues with smooth travel?


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## Yabert (Feb 7, 2010)

In my case, the pushrod is long and move his extremity by 1/2" don't change significatively his angle.


Hum! I'm not sure about my 25% increasing force....
How can you calculate 10 lbs force on the pedale will give 42.5 lbs at the original hole and 57 lbs at the modify hole.


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## dtbaker (Jan 5, 2008)

Yabert said:


> In my case, the pushrod is long and move his extremity by 1/2" don't change significatively his angle.
> 
> 
> Hum! I'm not sure about my 25% increasing force....
> How can you calculate 10 lbs force on the pedale will give 42.5 lbs at the original hole and 57 lbs at the modify hole.


are you asking how to calculate the difference you can expect?

what I would suggest is measuring the original lever arm lengths to the pivot center, which could be expressed like this with a 'target' pedal force of 40# on the original:

40/pedal_L=PushForce_orig/pushL_orig
(pushL_orig*40)/pedal_L = PushForce_orig

then figure what your PushForce would be using the NEW pushrod lever length and the same pedal force:

(pushL_new*40)/pedal_L = PushForce_new

then you can see the % increase would be:

(( PushForce_new - PushForce_orig ) / PushForce_orig ) *100

...but a possible problem is that you might not have enough travel to fully depress pedal if one of the brakelines fails and you have to 'take up the slack' in the tandem cylinder to generate pressure in the second brake circuit. This could be tested by loosening one wheel bleeder, and seeing if you can generate pressure on the second circuit before the pedal bottoms out.


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## Yabert (Feb 7, 2010)

dtbaker said:


> then you can see the % increase would be:
> (( PushForce_new - PushForce_orig ) / PushForce_orig ) *100


Yes, it's the formula I talking about.


So, ((57-42.5)/42.5)x100 = 34% of increasing force.


About the travel, I think I'm lucky because in the Smart, the pedale is build like I can do 2.5x to 3x the original travel before hit any interferences. In fact, the booster and the cylinder are under the drivers legs under the floor.
It's probably not the case of many car.


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## EV-propulsion.com (Jun 1, 2009)

Actually this is (or was when manual brakes were very common (70's)) the way GM had their brake pedal designed- two holes in it (just like Yabert) and they used the correct hole upon assembly. If they were swapped the brakes were either very touchy or very poor...
_*EDIT* although the above is correct, below is not. Power brakes were standard, power steering was optional in the earlier years. Sorry Tido, and thanks for the correction dladd_
But going back to the OP's question, since he is converting a miata, many of them were produced with non-power brakes, maybe half of them and they stopped well. So if I read his question right, I would say he doesn't need power brakes, and if his car has them and he chooses to swap to non-power to avoid using a vacuum pump, parts are abundant for those cars so he could just install the non-power parts relatively cheap. Keeping it simple....
Mike
www.EV-propulsion.com


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## tido (Sep 20, 2011)

EV-propulsion.com said:


> Actually this is (or was when manual brakes were very common (70's)) the way GM had their brake pedal designed- two holes in it (just like Yabert) and they used the correct hole upon assembly. If they were swapped the brakes were either very touchy or very poor...
> But going back to the OP's question, since he is converting a miata, many of them were produced with non-power brakes, maybe half of them and they stopped well. So if I read his question right, I would say he doesn't need power brakes, and if his car has them and he chooses to swap to non-power to avoid using a vacuum pump, parts are abundant for those cars so he could just install the non-power parts relatively cheap. Keeping it simple....
> Mike
> www.EV-propulsion.com


Really? they have miata without power brakes? great news, I will search for what years these models were designed.


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## dladd (Jun 1, 2011)

EV-propulsion.com said:


> But going back to the OP's question, since he is converting a miata, many of them were produced with non-power brakes, maybe half of them and they stopped well.


i don't think this is correct. You may be thinking of power steering.


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## azdeltawye (Dec 30, 2008)

tido said:


> Are there vacuum pumps made for conventional cars? ....


Late model VW and Audi gasoline vehicles with the turbo option AND automatic transmission have a factory installed electric vacuum pump for the brakes. Check the thread below for more info. I got one for my EJetta from http://www.car-part.com/ for less than $75. It has performed flawlessly since I put my conversion on the road 1.5 yrs and 15,000 miles ago.

http://www.diyelectriccar.com/forums...highlight=audi


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## EV-propulsion.com (Jun 1, 2009)

Ooops , yes you are right. What exactly WAS I thinking? My apologies for sending the OP down the wrong path. I will edit my post.
Mike


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## tido (Sep 20, 2011)

EV-propulsion.com said:


> Ooops , yes you are right. What exactly WAS I thinking? My apologies for sending the OP down the wrong path. I will edit my post.
> Mike


haha ok thanks anyways


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## tido (Sep 20, 2011)

azdeltawye said:


> Late model VW and Audi gasoline vehicles with the turbo option AND automatic transmission have a factory installed electric vacuum pump for the brakes. Check the thread below for more info. I got one for my EJetta from http://www.car-part.com/ for less than $75. It has performed flawlessly since I put my conversion on the road 1.5 yrs and 15,000 miles ago.
> 
> http://www.diyelectriccar.com/forums...highlight=audi


Very good, I'll take a look at this


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## bruceme (Dec 10, 2008)

The same effect can be done using a smaller diameter master cylinder. This is what I was talking about with airplanes. The foot controls on an aircraft are split. heal left/right moves the rudder and steers the nose/tail wheel on the ground. The toe left/right engages the brakes on either wheel (differential). This helps us turn corners in tight spaces (no reverse).

We can generate a pretty impressive brake effort with just tippie toes.

-Bruce


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## PTCruisin (Nov 19, 2009)

Here is the vacuum pump I am using. I bought this from Dimitri at Clean Power Auto for $100. Works great!


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## tido (Sep 20, 2011)

I don't know how brake pumps work exactly, would any1 mind explaning?

I mean some people talk about a switch. What is that switch and what is it connected to? any picture?

Where do I find the switch (if that's all missing to have it all working)

thanks


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## dtbaker (Jan 5, 2008)

tido said:


> I don't know how brake pumps work exactly, would any1 mind explaning?



vacuum boosters need vacuum to assist your pedal force in applying pressure to the master cylinder piston. you have to generate a vacuum (vacuum pump), turn the electric vacuum pump on and off depending on the vacuum remaining in the system (switch), prevent it from leaking back out (check valve) and have an empty volume that acts as a 'spring' for the vacuum as it is used and released by the booster (reservoir). Without a proper size reservoir the vacuum pump may not be able to provide enough vacuum when the pedal is depressed several times in a brief period.

see this section of my build to see a typical install....
http://www.envirokarma.org/ev/06.VacuumSystem.shtml

note however that the original install location of the pump turned out to NOT be good for long. When the pump is not mounted with the feet 'down' with the provided screws, the weight and vibration of the pump will fatigue and shear the (too small) mounting screws. I ended up moving the pump and using a different method to fasten more securely.


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## dtbaker (Jan 5, 2008)

has anyone USED the ones made for ford f250 (and other ford products) like:
http://cgi.ebay.com/ebaymotors/CARD...essories&fits=Model:F-250&hash=item5ae03e8e89

this one catches my eye because it looks like it has the resevoir built in... simplifying plumbing, and all for less than $100!

looking for someone who has one? comments?!


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## tido (Sep 20, 2011)

I have made some research and a diesel pump uses the fuel it is pumping in order to cool itself, how can it acheive this? How can the pump pump air without damaging itself?


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## dtbaker (Jan 5, 2008)

tido said:


> I have made some research and a diesel pump uses the fuel it is pumping in order to cool itself, how can it acheive this? How can the pump pump air without damaging itself?


I don't know what you were researching Tido.... these pumps are designed to pull a vacuum into an (empty) reservoir, not pump diesel fuel. My question is whether this particular unit, which is USED on a diesel f250 among other vehicles is what the volume of the resevoir is, and how much vacuum is pulled, so I can tell whether it will be suitable to consider for transplanting into an EV.


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## Anaerin (Feb 4, 2009)

tido said:


> I have made some research and a diesel pump uses the fuel it is pumping in order to cool itself, how can it acheive this? How can the pump pump air without damaging itself?


A diesel fuel pump only runs for a very short period without fuel inside it, so the temperature build isn't too massive. The heating of the diesel also works in the ICE's advantage, as at low temperatures (10c or lower) diesel fuel can "gel".

However, fuel pumps are quite different to vacuum pumps. Vacuum pumps are (typically) rotary vane pumps, or more cheaply, piston pumps, as they have to remain airtight while pumping and be able to cope with very low pressures, whereas fuel pumps tend to be gear pumps.


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## tido (Sep 20, 2011)

Thanks for the replies!

I actually don't know much about those things but I sent an email to the SAAQ (to see if they would approve my conversion) and I posted back their questions regarding the materians I want to use. I will now use your answers to reply to him


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## ndplume (May 31, 2010)

PT,
On that Volvo UP28 Pump, did it have an integrated pressure switch?
Or did you run a separate switch?
Thanks


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## bruceme (Dec 10, 2008)

So this thread was supposed to be about how to a simple hydrolic non-assist brake system... so how did it turn into a discussion on pumps?


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## PTCruisin (Nov 19, 2009)

ndplume said:


> PT,
> On that Volvo UP28 Pump, did it have an integrated pressure switch?
> Or did you run a separate switch?
> Thanks


I connected a separate switch in series with the coil of 12V automotive relay which controls vacuum pump. I am using an inexpensive vacuum switch from Cloud Electric http://www.cloudelectric.com/category-s/49.htm although they don't seem to show it in their inventory anymore. You might message them to see if it is still available.

Ralph


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