Wheel/ Brake drags intermittently.

timotb · Post by **timotb** » Sun Mar 22, 2015 2:47 pm

This is a case of a newer (90 hrs air frame) RV7a with a left wheel or brake that intermittently drags/ binds.

Have to use excessive power to taxi off the runway after one takeoff. This has happened more than once. Park the aircraft and wait 5-10 minutes then the problem is gone. You can push or pull the aircraft with no issue.

Removed the wheel faring and find no visible issues. These are Cleveland wheel and brakes. The main gear wheels are sealed bearings.

My theory is either the wheel bearing or brake is heating up excessively, causing expanding and thus momentary bindings/dragging. These are my second pads and they should be sufficiently broken in.

Thoughts or comments?

captain_john · Post by **captain_john** » Sun Mar 22, 2015 7:22 pm

...or the pedal is not lined up correctly and holding pressure on the master cylinder?

Possible???

You asked for an idea. I am just throwing it out there.

CJ

timotb · Post by **timotb** » Sun Mar 22, 2015 7:28 pm

I appreciate it. That is a real possibility.

bruceh · Post by **bruceh** » Sun Mar 22, 2015 10:56 pm

Do you have the return springs added on the pedals?
It is an option to add these so that the pedals return to the fully open position automatically. Here is a picture of my installation of the springs on the brake cylinder shafts.

Just get some springs, a shaft collar and some nylon washers.

timotb · Post by **timotb** » Mon Mar 23, 2015 7:24 am

I built them according to the drawings. Don't remember seeing any springs in the plans, so no. I need to add them. Looks like regular hardware bought material, trial and error installation, no retrofit kits? Where did you get the springs and collars?

Attachment hardware looks like standard AN3 bolts washers with castle nuts and cotter pins. This I used according to the plans.

Post by **bullojm1** » Mon Mar 23, 2015 9:22 am

I installed the brake return springs on my master cylinders. In 4 years and 300 hours, I just changed my pads for the first time. They wore nearly perfectly evenly.

Here is the parts list from McMaster:

(1) Pkg 6389K625
Nylon Bearing Flanged, for 3/8" Shaft Dia, 1/2" Od,
3/8" Length, Packs of 5 $1.97 Pkg

(1) Pkg 9657K115
Steel Compression Spring Zinc-Plated Spring-Tempered, 3"
L, 1/2" Od, .047" Dia, Packs of 12 $5.29 Pkg

(4) Ea. 9946K13
Aluminum Set Screw Shaft Collar 3/8" Bore, 3/4"
Outside Diameter, 3/8" Width $1.82 EA.

bruceh · Post by **bruceh** » Mon Mar 23, 2015 1:22 pm

I was able to find all of these parts at my local hardware store.

One other common change is to swap out the 2 short bolts that the pedals hinge on, and instead put in a single long bolt through both hinge holes. The really long AN bolts are expensive, so I bought some stainless drill rod in the same diameter, cut it to length and then used a die to make threads on each end. I also drilled a hole in the ends for cotter pins.

Vlad · Post by **Vlad** » Mon Mar 23, 2015 6:21 pm

One more vote for the springs. I had them from day 1.

hydroguy2 · Post by **hydroguy2** » Mon Mar 23, 2015 11:10 pm

No drag and no springs.

290hrs on the original pads. Just ordered new pads and will change them next month. I'm on my first set of tires too, I'm guessing they will last another 290 hrs. I don't use the brakes much.

timotb · Post by **timotb** » Wed Mar 25, 2015 4:13 pm

Thanks for all the input. I'm going to try the springs.