The International Cessna 170 Association

I realize there's been a long discussion regarding dual puck brakes. We have been flying 29"AKBW with dual puck brakes, mostly on sod. I'm buying a used set of wheels to install 8.50x6 tires for winter flying, if the snow ever gets deep again, off concrete/asphalt, to preserve the big, expensive lovely AKBW tires. Does anyone have experience with dual puck brakes and 8.50 tires on hard surface and sod? Any serious issues? The RA working on these wheels & brakes is concerned that the dual puck brakes might be too much for the smaller tires and "lock up" on sod. Of course we do have the STC for the 29" tires.-Thanks-fred

I've never had any problem with tires "locking up" on sod. They slide.
Concrete/asphalt is a different problem.
I have single-puck Clevelands on 6" tires. While admittedly taxying too fast on concrete I once nearly blew past the taxiway turn-off I intended to make and got on the brakes fairly hard. While the tires never locked up.... they sufficiently slowed the airplane so rapidly as to lift the tail almost to the point of a prop-strike despite my having the elevator held full up/back.
Got my attention.

Fred,

I have double pucks on my 170A with 8.00's. Never had an issue with locking up on grass. I do feel that the double pucks are too much for my airplane and how I operate it. A short grass strip to me is 2500 feet long, a far cry from what you guy's up north are flying out of. With 2500 feet of runway even with 75 foot pines on the end I am down and stopped with little or no use of breaks.

On concrete it’s a different story and I do use the breaks more on concrete but even then its more for making turns and getting stopped on the runway to make an intersection turn off.

Thanks to both Bill and George. I'm afraid I should have clarified that my plane is a 170B w/Avcon Lycoming 180/CS Prop, Horton Stol and VGs and 180 gear conversion. This plane LEAPS off(full tanks/2 adults aboard, @ 2500 density altitude) at less than 450 ft with 20 degrees of flaps and lands in less distance with the 29" AKBW and dual puck brakes. Given these specs, any idea what difference the 8.50x6 tires are likely to produce? I hardly use the brakes with the 29" tires.

I had dual pucks on my '52 C170B and operated with six inch wheels and tried all sizes of applicable tires, (settled on seven inch)
and never had a brake problem on any kind of surface. They had enough poop to keep the tail up to almost a stop on dry pavement, but one does not have to stomp on them that hard all the time. I thought they were great simply because if I needed
absolute maximum braking, they would provide it.
Admittedly, they just about provided overkill with 600 tires, but they provided confidence with 850s.

That sounds very comforting. The plane came with both sets of tires. Air Salvage of Dallas was the only place I could find that had a set of wheels suitable for this plane. It's turning out to be much more complicated than I expected. Thanks for your response, it's what I was hoping to learn.=fred

My first instructor had a saying every time I asked him "how much?". His answer has served me well for 42 years.

His reply was always, "Just enough but not too much". That advice works well with any type of brakes.

You are overthinking this. Double puck brakes are great and required for the Bush Wheels and they run fine on 800 or 850 size tires too. I have run double puck brakes on 800 size tires for years and have had no issues.

Keep in mind the double puck brakes only apply as much brake as you tell them to. I have ran 6.00x6, 8.50x6, 8.50x10, and 31" Bushwheels all with no problem with double puck brakes. Back in the day when field approvals were relatively easy to get many FSDO's required double puck brakes if you were installing the 8.50x6 tires. I wouldn't worry about it, just be conscious of the fact that you don't need to push as hard on the brakes until you get used to it. Good luck.
Shawn

Thanks to all for your responses. The question initially arose from the "RA" (I don't know what that designation is) at Air Salvage of Dallas who is rebuilding the wheels for the 8.50x6 tires so I don't use up the 29"AKBW when the snow is too deep for them. We've found the big tire can easily handle eight to ten inches of soft/new snow. But I don't want to use the big tires up providing tail wheel endorsements on hard surfaces. The input has been reassuring and definitive.-fred

Now you really have me! What do they do at Air Salvage in Dallas to "rebuild " wheels for an 8.50 tire? In my apparent ignorance, I just installed the various size tires interchangeably on my six inch, three bolt, wheels.

femoskol wrote:.............providing tail wheel endorsements on hard surfaces..............-fred

You didn't mention giving dual in your plane at first and the comments were probably all made assuming only you would be flying the plane.

Remember, releasing the brakes is one of the things an instructor cannot do when the student is flying. Be sure and caution the students to apply the brakes "just enough but not too much".

hmmmm....changing wheels with tires attached rather than changing tires with the season is what I'm going to accomplish with the wheels from ASOD...used wheels and dual puck Clevelands that required some refurbishment...only salvage yard I could locate that had used wheels...haven't had any problems with students using too much brake with the 29" tires...some experienced pilots, one primary...focused on landing as slow as possible and not using brakes unless essential, which is rarely is on 2000' sod...thanks for the advice though

I suppose you could always change the brake calipers back to single with the smaller wheels.....

Having once switched to double puck brakes, I'd never go back to singles. The doubles just work so much better.

How many of you guys remember how crappy automobile and pick up truck brakes were before they perfected power brakes?
Would you ever go back?