FYI Beringer dual caliper brakes on a CubCrafters Carbon Cub

[Cactus Charlie]

Whey they chose 29's if beyond me.

Perhaps because it was a compromise between 26 and 31. I would never put 31 inch Bushwheels on my FX-3. I simply don't plan to go anywhere I would need them and there are too many disadvantages.

Perhaps I go to less hostile places than those who chose 31 inch tires. My 26 inch tires with Grove 1.5 inch calipers are a perfect match on my FX-3. I have done nothing to them except top of the reservoirs in over 500 hours. 46% of my nearly 700 FX-3 landings were not on paved runways and I have to land on a paved runway to get back to my hangar.

Not criticizing those who choose 31 or even 35 tires. Just a caution to those who may be deciding on large tires for the wrong reasons.

 

[Neal]

It's off topic but I'll share why I chose 31's. As I'm stuck on on asphalt I wanted max circumference for tire wear. The cost difference is minimal from 29's which CubCrafters now requires for the 83" prop. We all know they used 26's early on. So when it comes to 29 vs 31 and only a few hundred more for seemingly a lot more tread area I chose 31's. Obviously with off airport and ruts, etc. larger is just safety margin. Here in VA where it's a lot or tall grass you can't see the trenches.

 

[Cubonaut875]

I agree 100%, If I'm forced to land in a field, something I'm not planning on, it can mean the difference of joining the flip flop club or not. That's 7% more tread area in a 31", so in theory should last 7 percent longer. I'm not sure if the option for additional rubber is available in the 29's.

 

[Cactus Charlie]

That's 7% more tread area in a 31", so in theory should last 7 percent longer.

The larger the tire the greater the rotational inertia. More rubber will be lost accelerating the larger tire on first runway contact than for a smaller one. That's going to eat up some, perhaps all, of that theoretical advantage.

 

[ve6yeq]

Bleeding the brakes does benefit from having a dedicated Beringer brake bleed kit. Perhaps those that are having problems have not spent the $100.00 to get the right tools to make this easier. Neal told me about this product early on in my adventure.

Great to know - I have ordered the Beringer brake bleed kit, not just the adaptor, for future use.

After studying the problem they decided a solution of a smaller master cylinder, STOL brake pads and even suggested changing the pedal geometry. This solution would give a 30% increase in brake pressure.

Thanks for the investigation report from Beringer France (done before the STOL pads were available) - it does appear that for their EX-1 with 29" ABW, they got the largest improvement from reducing the master cylinder size to increase the hydraulic fluid pressure at the expense of increased travel (which they seem to like). I need to check my master cylinders to see exactly what size they are...

Since with the single caliper system on my plane as it was delivered, I would have to shift my heels up to the top of the brake pedals, push back in my seat just to hold for runup, 30% was not going to cut it.

Interesting, I only have to do that if I attempt a runup above 2000 RPM. I normally set 1850 RPM and then lean closer to 1900 RPM for my run-ups. I wonder if you experienced the extra leverage of the 31" ABWs over my 29" ABW?

If I were you, I probably would go with the STOL pads.

Minds think alike.

Beringer's test was on 29" Bushwheels for some odd reason.

I went with the heavy tread version of the 29" bushwheels, as I do not see myself landing on anything more extreme until I get much more experience - then I will think about a larger set...

I'll include the Beringer study for your information.

Thanks a lot for that report - it was interesting to see all the things that they tried. As it appears that you can get suitable rod ends and rod/tube without too much hassle (e.g. aircraft spruce), I wonder if I should also try replacing the linkage push/pull bars with ones with less play. In flight, there should be tension only in the rods connecting the front and rear pedals. When you apply the brakes, the top rod is in tension, and the lower rod is in compression, so any play in the system should be observable. Next time I am at the airport, I will see if I can feel the play...