# Reducing disk brake drag



## EliteEV (May 6, 2008)

I read long ago that someone had fitted their disk brake pads with springs to keep the pads off the disks and therefore reduce drag. Any ideas out there on where I can get these? I think they would be hard for me to fabricate.

Thanks,

Scott


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## Jimdear2 (Oct 12, 2008)

EliteEV said:


> I read long ago that someone had fitted their disk brake pads with springs to keep the pads off the disks and therefore reduce drag. Any ideas out there on where I can get these? I think they would be hard for me to fabricate.
> 
> Thanks,
> 
> Scott


Scott,

How old is the vehicle?

Most everything built in the last 10 - 12 maybe more years have low drag calipers. 

When clean and properly lubricated a modern caliper and piston will back off "just a touch". Enough to reduce/eliminate drag, but not so much as to create a long brake pedal stroke needed to pump the piston back out. Move that piston back too far with a spring and you will have *NO BRAKES* for the first and maybe second stroke of the pedal.

Sorry if this sounds harsh, but in my opinion, I would say you are looking for a casket or a jail cell if you do something like that.

In other words be *Very Careful* putting any kind of spring or modification into your caliper.


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## EliteEV (May 6, 2008)

Thanks for the reply, Jim. I was wondering about that very thing. My car is a 1974 Lotus (http://www.diyelectriccar.com/garage/cars/123), so it doesn't have the low-drag features you mentioned. I agree it is foolhardy to compromise safety for an amp or two.

Scott


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## Duncan (Dec 8, 2008)

Hi Elite
Are you sure you have drag?
Right from the very first disc braked cars the calipers have been "low drag" in that the design of the seals tends to move the pistons back a smidgen, also the (minimal) movement in the wheel bearings tends to knock back the pistons 

I would suggest you strip, clean and lube your system - then see how much drag you have


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## Jimdear2 (Oct 12, 2008)

EliteEV said:


> Thanks for the reply, Jim. I was wondering about that very thing. My car is a 1974 Lotus (http://www.diyelectriccar.com/garage/cars/123), so it doesn't have the low-drag features you mentioned. I agree it is foolhardy to compromise safety for an amp or two.
> 
> Scott


For older vehicles there are a lot of nice caliper upgrades, look good, lighter, better brakeing performance.

Check online with some of the car brand clubs.

Jim


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## DavidDymaxion (Dec 1, 2008)

After having guide pins seize on my gasser I would always lube the guide pins with high temp grease every time I worked on the brakes. I then found the grease would cook into a hard varnish, so now I also clean off the old grease first. If you can't move the caliper back and forth by hand on the guide pins, they need to be cleaned and regreased.

If the caliper is loose on the pins, the pins, and possibly the caliper, need to be replaced.

I still had rough movement with new pins once. Some really fine sandpaper polished the guide pin bores and guide pins, and then everything slid smoothly.

Also make sure your brake pads are wearing flat. If you get some slop in your guide pins or wheel bearings the pads can wear at an angle, giving a bit of a door stop effect. Another thing that can cause this is age and the brake bracket bending, so look for that and replace if needed.

I believe in the "disk brake quiet" stuff. Your piston is supposed to retract very slightly via its seals, and the "disk brake quiet" stuff is a glue that will help also pull back the pads.

When putting in new pads I check they move smoothly, so they can move in the bracket as they wear. You might need some fine sandpaper polishing.

Check the handbrake cables move freely, so the handbrake fully releases.

If the brake disk is rough, that is another source of brake drag. Turn or replace.

This one is subtle. I had wheels that were tight for a rocking motion, but would telescope in and out a bit (normal for a solid axle car). When I replaced the axles they were a slightly different length, and the brakes rubbed causing rapid wear. I finally fixed that by putting thin spacers under the brake disks. Moral of the story is make sure your wheels are tight as it can affect brakes.

I have read about folks going for the ultimate efficiency making sure the piston is perfectly round, and the caliper piston bore is round.

I wonder if stainless steel disks have less friction than cheapy iron ones?


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## ngrimm (Oct 19, 2007)

Has anyone done a before and after range or amp test to determine the effect reducing disk brake drag? My 71 Toyota EV has drums but my 88 Bronco II ice has disks up front that feel like they turn pretty hard and my gas mileage is poor.


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## lockduke (Dec 25, 2009)

Gentlemen after reading your posts about disk brake drag I thought that I remembered that I had used a different pressure residule valve on my last race wagon. We had a problem with the wagon pulling wheel stand's and locking up the front wheel's and skidding the tires and flat spotting them. After a few round's it became a little disconcerting with the vibration from the flat spot's. The cure was to replace the pressure residual valve. we found that there were several different pressure value's for them two of the most common are 10 and 15 lb. values. At that time we also found a 2lb. valve that turned out to be the one we needed. It completely elevated our problem with locked up wheels and flat spot's. Also it helped our ET's by 3 hundredth's of a second on a steady round after round basis's. Sorry to ramble on' but in reference to your application I think the lightest residual valve would work in this case. And not make you pump the brakes and give you that pucker factor that you get when you hit the brakes and nothing happens. DUKE







I think we got them from JEG'S or SUMMIT RACING


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## jeremyjs (Sep 22, 2010)

DavidDymaxion said:


> I wonder if stainless steel disks have less friction than cheapy iron ones?


Stainless would be a horrible metal to make disks out of. It sheds heat poorly and will warp in no time flat. The only 2 really viable options I know of that would be better are ceramic and carbon fiber. Both are much more expensive and I know ceramic has to be hot to work well.

On the original topic. I have to agree with what others have said about the possible dangers of using springs. Unless the braking system was designed to work with them it's probably a bad idea. I have however seen at least one car that was designed to use small,weak W shaped spring clips to hold the pads slightly back from the disk. I think it was an early 90's ford escort.


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## Ziggythewiz (May 16, 2010)

ngrimm said:


> Has anyone done a before and after range or amp test to determine the effect reducing disk brake drag? My 71 Toyota EV has drums but my 88 Bronco II ice has disks up front that feel like they turn pretty hard and my gas mileage is poor.


I just did this on my '74 bug. The front wheels initially would spin 3/4 of a rev, after adjustment ~20 revs. I didn't see any change in speed or amps pulled, but charge draw changed from my 4.6 kWH usual to 4.56. The brakes had to move much further to engage, but were also much easier to apply as the lever position was now helping instead of resisting.

Next I changed the back brakes, originally got 1/4 rev on a spin. After adjustment still only got 1.5 revs. Now my cruising amps (at 45 MPH) dropped from 80 to 60, but for some inexplicable reason the charge took ~5.5 kWh. Brake performance didn't change.

Next step is to take apart the rear brakes and see what condition the bearings are and if they have any grease left on them. Will likely replace and repack bearings.


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