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  #1  
Old 08-14-2022, 10:41 PM
hangar7racing@gmail.com hangar7racing@gmail.com is offline
 
Join Date: Mar 2020
Location: memphis, tn
Posts: 38
Default Brakes

Finally getting to taxi test on a RV3 I purchased.

Iíve put new APS Black Steel rotors and pads and cleaned andvrepacked the Cleveland master cylinders.

Brakeing is very weak. I am thinking the master cylinders are not putting enough pressure to the disc. I am considering replacing the Cleveland master cylinders with Matco and plumbing a reservoir to them.

Has anyone had any experience with increasing the brake efficiency?
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  #2  
Old 08-14-2022, 11:56 PM
JDeanda JDeanda is offline
 
Join Date: Apr 2013
Location: Ventura, CA
Posts: 338
Default Some Thots

We had perfectly good brakes on our RV-6 using Cleveland master cylinders and brakes. When the Cleveland master cylinders needed parts, sticker shock led me to just buy new Matco cylinders. The Matcos' bores are just a bit bigger diameter than the Clevelands, which reduces hydraulic advantage. The airplane still stops OK but requires quite a bit more pedal effort, which in turn, loads the floor/belly structure and loosens rivets down there because we still have the prehistoric floor-mounted rudder pedals, and so I've had to repair the belly stringers. I'll bite the bullet and buy parts for the Clevelands and put them back. Bottom line, you COULD use smaller diameter master cylinders to get more brake pressure for a given amount of push at the rudder pedals. Assuming that's your problem, then smaller diameter brake master cylinders should help, assuming of course, that you'll be left with adequate fluid volume and you do a good job of bleeding air out of the system. Before you go to all that trouble, take a look at the linings and discs. If the linings look glazed, new linings might be all you need. I've been known to sand brake discs with 180 grit paper to remove light scoring and increase the friction a bit. A fluid leak can cause trouble, too, but it seems unlikely both would leak the same.
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  #3  
Old 08-15-2022, 06:04 AM
swjohnsey swjohnsey is offline
 
Join Date: Nov 2018
Location: Kingsville, TX
Posts: 495
Default

I had experience with weak brakes on a RV-3. I didn't get it fixed but the next owner did. The problem was with the mechanical advantage to the master cylinders.
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  #4  
Old 08-15-2022, 07:22 AM
lr172 lr172 is offline
 
Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 7,466
Default

With new pads and rotors, it will require some break in before they reach their full potential. As long as they stop well enough to be safe, I would do some searching for break in recommendations or do at least 25 aggressive stops before you decide they are not adequate.

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  #5  
Old 08-16-2022, 09:51 AM
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BruceMe BruceMe is offline
 
Join Date: Feb 2005
Location: Shawnee, Kansas
Posts: 840
Default Tailwheel brakes

The last thing you want on a tailwheel are good brakes
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  #6  
Old 08-16-2022, 12:42 PM
swjohnsey swjohnsey is offline
 
Join Date: Nov 2018
Location: Kingsville, TX
Posts: 495
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Not true. You need to know how and when to use good brakes. My RV-3 brakes wouldn't hold 1700 run-up.
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  #7  
Old 09-06-2022, 08:06 AM
Mach86 Mach86 is offline
 
Join Date: May 2021
Location: Georgia Dahlonega
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I run up at 1800 and it won't hold
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  #8  
Old 09-06-2022, 09:33 AM
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Pat Hatch Pat Hatch is offline
 
Join Date: Jun 2006
Location: Vero Beach, FL
Posts: 925
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Matco has what they call intensifier kits. Basically a sleeve and smaller piston to replace what's in the master cylinders now. They claim it increases brake pressure by 60%. I got them on my Matco brakes and they do help a lot if you have marginal braking now. Of course, you will get slightly more pedal travel, but it wasn't noticeable to me.
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Last edited by Pat Hatch : 09-06-2022 at 05:07 PM. Reason: Typo
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  #9  
Old 09-07-2022, 02:19 PM
abuura abuura is offline
 
Join Date: Jan 2006
Posts: 134
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Bone stock brakes/disk from 2006, replace the pads annually, and condition new ones by taxiing 1500ft at 1700rpm with enough pedal force to yield 5-10mph - one time. Let them cool, they hold the plane to 1800rpm, at least. I've braked hard a few times and they did great.
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  #10  
Old 09-07-2022, 04:06 PM
D-Dubya D-Dubya is offline
 
Join Date: May 2009
Location: Beaumont, Texas
Posts: 197
Default

I don't know about all the brake manufacturers, but Cleveland has conditioning procedures "...to create a thin layer of glazed material at the lining friction surface." And yes, those are their words, not mine. I followed those procedures during my first taxi test and my brakes work just fine, thank-you. They'll easily hold the plane at run-up RPM--and higher. And those are all stock components straight from Van's.

I'll occasionally get on the brakes kinda hard to make a turn-off, but I've never braked so hard that i felt the tail would lift. Not a fan of doing any STOL competitions in an RV, you know.

Getting back to the OP, you absolutely may be able to get better results with different master cylinders, but check the cheap & easy stuff as well. If the pads aren't conditioned properly, the procedures referenced above basically say to do 'em all over again. Also make sure that the brake pedals aren't binding on their pivot bolts. I remember this being an issue for some people many years ago. The solution was to use one long bolt as a pivot rod instead of two smaller bolts. I want to say it's something like an AN3-42. The RV-3 may be different than the RV-7 I built, but I would assume they're somewhat similar in design and function.
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