31" bush tires on cessna 170b

[Francis Cahoon]

Does anybody have any experience with the pros and cons of 31" bush tires. And do you have them on your plane now? Please respond if you have this set up. Thank you.

[N419A]

Only cons I can think of is; price tag, slows you down a little, and might make you land where you shouldn't. Here's a little discussion on this thread.
Paul
http://www.cessna170.org/forums/viewtop ... f=5&t=6562

[hilltop170]

I have flown the 31" Bushwheels on a C-180 in Alaska and they were wonderful! The only operational problems were reduced brake effectiveness and on steep beaches, the tires tended to roll over the bead sideways which is unnerving but caused no real problem with control. A few more psi than recommended helps a bunch if you know you'll be operating on steep side hill terrain. Double puck Clevelands will be needed to give adequate stopping power.

You'll also need a Baby Bushwheel tailwheel to get the most advantage out of them.

They will slow down cruise speed but that will be more than made up for in how much they expand your available landing spots.

Let your pocket book be your guide when you make you decisions on where you land.

I personally prefer the 29" Bushwheels.

[Francis Cahoon]

Richard, why do you prefer the 29" over the31"? Thanks to those that have responded thus far.

[hilltop170]

The 29" don't roll over as bad as the 31" on side hills but still provide adequate floatation for everything else. That being said, the 31" won't roll over as much on a C-170 as on a C-180 because of lighter weight. If you like the 31" better, then get them, you will love them. Just stay off of pavement as much as possible, they will last longer on grass or gravel.

[Francis Cahoon]

Thanks Richard for the info. In your opinion, Do they really help you get off the ground faster?

[hilltop170]

In my opinion, no, not always, but sometimes they do.

They do give the plane a higher angle of attack while on the ground which theoretically would allow it to take off sooner as it gets the lift it needs. But, the plane has to accelerate to the speed required to generate the required lift. More horsepower is the best way to get off shorter because the acceleration is quicker, no matter what the surface is.

The large tires actually have more rolling friction than smaller, higher pressure tires on hard ground because the round profile of the tire has to flatten as it touches the ground. That wads up the tread because you can't flatten out a round shape without deforming it, which takes energy that would be better used for acceleration. Plus the side walls deflect quite a bit due to the low inflation pressure. The belted Bushwheels minimize the deformation but just look at the tracks left by a large tire as it rolls over sand and you can plainly see the stretch and wad marks left by the tire as it deforms.

On soft ground smaller tires dig in more and that increases drag more than the larger tires so the big tires will help you there. So, it is a trade-off and each situation is different, sometimes they help, sometimes they don't.

My reason for using large diameter tires is not to get off shorter but for insurance on rough, soft, or uneven ground. And if you have thoughts of water skiing with large tires, be aware they create very high drag on water and you might have a hard time taking off again. I witnessed a 180hp Super Cub ditch in a lake while skiing because he couldn't overcome the drag from the 30" tires and had to shut down before he hit the cut bank. It flipped over and it turned into a real fiasco before it was over. I also know a guy who totalled a freshly overhauled/restored 180hp C-170 with 31" skiing up a river, he couldn"t get back off the water. Something to think about.

[hilltop170]

Anything above about 35mph groundspeed and you can't push the tire under water, it will ski. But, the larger the tire, the more power required to break it free. Most guys I know who water ski use it to slow down before they roll up on a gravel bar to reduce landing distance. I personally don't need to land that short, ever, especially in a 170. It can already land shorter than it can take off.

[Francis Cahoon]

Thanks again, this type of information is what I joined for. I am probably trying to reinvent the wheel. I am trying to find the right combination of aftermarket products to have a plane that lands and takes off as short as possible. Thanks again.

[Blue4]

Bushwheels are big and heavy, so if its short performance you're looking for there are plenty of other mods you'd be better off pursuing.

On topic, I think 29s are a better fit for the 170 than the 31s. The speed difference between 29s and 31s is negligible, as is the weight and price (all relatively speaking of course). So at the end of the day those sizes are so close you're really cutting a fine margin.

If you're going to run bushwheels, my recommendation (and that of many other more-experienced off-airport operators than me) is to run the baby bushwheel on the tail as well. It will save the airframe from vibration. It will also decrease your angle of attack that your 31s or 29s just gave you -- and thereby increasing your ground run. How much? Not enough to matter except in competition or in trying to go places you probably shouldn't have tried going in the first place.

If you're not going to be a serious off-airport operator, consider the Goodyear 26" tires. They'll give you a better angle (probably as much as the 29s because bushwheels are always aired down), offer more footprint/floatation, much cheaper price, and you can still operate them on really dangerous terrain like pavement.

Good luck!!

[Francis Cahoon]

Does anyone know how or where I could get a copy of an STC or 337 for a Cessna 170B that allows for larger tires, like goodyear 26".

[n2582d]

Alaskan Bushwheel

[Francis Cahoon]

Thanks Gary, does anyone have experience with 4 ply recaps on their plane, such as do they last, are they legal on 170s, do they seem to balance ok, etc.

[jon s blocker]

I have been using 850x6 retreads for years and love them. I get them from Desser. Never had one that was not in good balance, and they wear real well. I have a heavy 170B, so it is a good test for a retread. Jon

[Francis Cahoon]

Thank you jon, I have been learning a lot lately about tires, stuff that I never really paid much attention to before, like I should wait to buy big tires until I know I can legally put them on, Cleveland wheel are not all rated the same, that the stickers that you use to identify them are made out of paper that comes off after awhile. So in closing, maybe my good deals are not that good. Live and learn I guess.