35" bushwheels

[Narwhal747]

Hello,

TLDR questions:
Are 35's a good idea for hard off airport on an FX?
1.75" vs 1.5" brakes on 35's and 31's?
Any other options that are a good idea with 31's/35's?
BBW + Acme stinger a good idea to offset weight with 35's, or overkill?

I talked to the sales team a little bit about this but I was wondering if I could get feedback from other owners or more input from the staff. I have an FX3 slot for next year.

I understand that 35"s are not a factory option for the FX series for engineering reasons.

I am probably going to take delivery on 8.50's because I need the 8.50's for my summit wheel penetration skis. However, I am planning to keep a separate set of wheels with tires mounted for summer use. I am trying to decide between 31's and 35's for this. I could feasibly take delivery on 31's and get the 8.50's later, but I figured it would be more economical to take the 8.50's from the factory. With the 2000 lb max gross weight of FX3, it seems like 35's are not prohibitively heavy and provide a substantial margin of safety/capability in rough takeoff & landing spots, or on sand/tundra (which are indeed surface I do plan to land on).

Are there any landing gear options that could serve to mitigate any potential risk to running 35's?

I am definitely getting safety cables. I do plan on taking the airplane off-airport quite, at least once I get some experience. I am based at an airport with a gravel runway, however it is a 1/2 mile pavement taxi to get to it (wear consideration). I also need to decide if the 1.75" brakes are necessary instead of 1.5"s and whether I should go with the Acme stinger + baby bushwheel. I feel the beefier tailwheel setup could have center of gravity benefits especially were I to run 35's. Main landing gear suspension will be some form of Acme's latest offerings.

Thanks in advance. Locked in a hotel with nothing else to think about.

[aeroaddict]

Yup, board to death in a hotel room, been there done that. No fun.

I cannot directly answer your question, but will say my 26" bush tires have gotten me anywhere I wanted to land. It seems that the weight of the large tires are almost prohibitive for me, uses up a lot of weight (EX-2).

Anyhow, I'm sure you know of SuperCub.org, it's a great resource and I believe tire size has been discussed to death. Might find some info over there if someone does not chime in here.

[Andy]

Seems to me that 35 inch tires are perfect for those that:

1. Want to reduce the aircraft useful load
2. Think the FX-3 is too fast and needs more drag
3. Don't want to see anything over the nose in 3 point attitude

Based on some very experienced pilot input in discussions on SuperCub.org there are very few people who go places that 35 inch tires are needed. I'm happy on 26 inch BushWheels but I don't go to places no airplane has ever been before. (Did enough of that with glider land-outs)

I think the brake choice depends more on whether you want to be able to do full power static run-ups rather than stopping performance for landing roll.

Takeoff tire wear on a paved runway must be almost zero. Makes no sense to taxi half a mile to gravel if the paved runway is closer.

I need the mod that allows me to dial in a lower density altitude. It's getting hot in Arizona.

[Narwhal747]

Thanks fellas, I do like to land in places that no other airplanes have. I figured having the set of 8.50’s and a set of bigger tires for quick swaps would give me the best of both worlds - long trip with just flights between airports - put on the 8.50’s and enjoy the 135 mph TAS. Local adventuring within a few hundred miles of home? 31/35’s.

I know I’m no Greg Miller (Mauleguy of big rocks long props fame), but he advocates pretty strongly for 35’s as a safety feature for those landing off airport, claiming the risk of damage from inadvertent rocks and potholes is greatly reduced. Additionally, the floatation on soft surfaces such as tundra and sand appears to be a big benefit. I realize they’re a +30 lb payload hit over the the 31’s, but that’s the beauty of an 850 lb payload in a 2 seater. I have flown a PA18 on 35’s and found it to be great fun, and visibility wasn’t much worse than my spirit of St. Louis esque 182 with an 8.50 nose wheel.

Maybe I will stick with the 31’s though. I feel compelled to respect the manufacturers recommendations, even if EAB allows me not to. Anyhow, just having some fun thinking about this stuff. This is the fun part!

[Andy]

I know I’m no Greg Miller (Mauleguy of big rocks long props fame), but he advocates pretty strongly for 35’s as a safety feature for those landing off airport, claiming the risk of damage from inadvertent rocks and potholes is greatly reduced.

Relative to what though? How do you objectively compare the advantages of 35 inch tires with all their disadvantages. What do you compare those advantages with - 26, 29 , or 31?

Sounds like you have far more off airport experience than me so I'll be interested to hear what you decide.

I couldn't stand to watch the linked video again and don't remember what he uses on the Kit Fox. Isn't it 26 inch?

[Narwhal747]

Relative to what though? How do you objectively compare the advantages of 35 inch tires with all their disadvantages. What do you compare those advantages with - 26, 29 , or 31?

Sounds like you have far more off airport experience than me so I'll be interested to hear what you decide.

I couldn't stand to watch the linked video again and don't remember what he uses on the Kit Fox. Isn't it 26 inch?

I think you might need an accelerometer like @turbopilot has in his dynon avionics package to scientifically and objectively quantify the advantages of 35’s. Breaking things on rough fields is a legitimate concern, for instance I had a mixture adjustment screw black out on landing in the 182 a few weeks ago, causing this:



There is gulley/ditch in the strip that I hit at about the 00:24 mark that is very difficult to see from the air. Yes, iit just came out of a carb overhaul so possible maintenance reinstallation issue, but this was on 8.50’s all around with an airglas heavy duty nose fork on what passes for a “strip”. Apologies for the poor video quality, friend filming from the right seat. I have read a few issues with light speed ignition wire connectors coming loose on our cubs, I would hate to have that happen in a remote place due to insufficient shock absorption.

[Andy]

Breaking things on rough fields is a legitimate concern, for instance I had a mixture adjustment screw black out on landing in the 182 a few weeks ago,

Straying a bit from the tire topic but I question your analysis.

The mixture screw only controls the idle mixture. The mixture screw could have progressively backed out during the entire time the engine was running. It would have not have been detectable until the throttle was reduced to idle and the airspeed was too low to keep the prop turning.

In my opinion it is far more likely that the mixture screw adjustment change was the result of engine vibration rather than anything that happened on landing rollout.

Edited to add - Do you know for certain that the mixture screw had moved? I seldom have the throttle on the idle stop any time between start and takeoff. I prefer to keep the rpm up to avoid plug fouling.

[Springloaded]

Hawgdrvr made a good point. I would highly recommend the 83” prop. So you might want to think about that with your tire decision.
‘Chuck

[Andy]

Hawgdrvr made a good point. I would highly recommend the 83” prop. So you might want to think about that with your tire decision.
‘Chuck

What data do you have to compare 80 and 83 inch props? Static thrust, takeoff distance, cruise performance, vibration - anything else? Genuine question and not attempting to be argumentative.

I know not many go with 80 inch prop but I have never regretted that choice.

Just as an FYI - I flew the FX-3 demo on skis with 8.50 and 83 inch prop. Nothing bad happened and I had only 1 hour on type before that flight.

[Springloaded]

What data do you have to compare 80 and 83 inch props? Static thrust, takeoff distance, cruise performance, vibration - anything else? Genuine question and not attempting to be argumentative.

I know not many go with 80 inch prop but I have never regretted that choice.

Just as an FYI - I flew the FX-3 demo on skis with 8.50 and 83 inch prop. Nothing bad happened and I had only 1 hour on type before that flight.

No data at all just what I felt when I flew it. Could t figure out why it seemed sluggish. I have no idea what cruise performance was,didn’t fly it long enough. Didn’t notice any vibration they both are pretty smooth. I commented when I landed and that’s when I learned it had a 80” prop. I’ve flown 2 of them now. It’s not the end of the world and It works fine I just prefer to 83. With hundreds of hrs in FX3 with a 83,i noticed instantly something was different.
Chuck