Brake performance with larger tires

[MontanaBird]

I will be replacing my existing 7.00-6 tires with 8.00-6 units, and will retain the existing single puck calipers.

For those intrepid 170 aviators who have done such things before, do the single pucks provide enough stopping power for those of us who really need it?

Thnx

MontanaBird

[Showboatsix]

I can lift the tail under heavy braking with mine, the tail wheel scale weight is 160 pounds, so you should be fine.

1956 Cessna 172 with Conventional gear conversion, with 800x6 and Cleveland barakes.

[Paul-WI]

I've been running 8.50 x 6 with the single puck and seems to work just fine.

Paul

[HA]

I wouldn't think it would change anything, the weight of the airplane didn't change so the brakes should still be able to stop it the same

the larger wheels give you the SPACE to add bigger brakes but not the need for them. if my physics are right, anyway!

[GAHorn]

Tire diameter acts as a lever upon the disc. Larger tires (longer levers) increases force upon the disc, which in turn, reduces brake effectiveness. The good thing is that the single Cleveland brake has an abundance of excess capacity for this weight aircraft.

The most likely trouble to be encountered will be taxiing in an exceptionally strong crosswind and finding it difficult to turn downwind. Even double-puck brakes will have difficulty with the manuever but will require less physical foot-pedal effort.

Discussion: Ultimately, tire/surface coefficient-of-friction will be limiting with either. A locked wheel is a locked wheel and that becomes the limit in taxiing. A locked wheel during high-speed operations can lead to disaster and is to be avoided. TO's and Landings are more limited by brake heat dissipation which are improved by double puck or larger single-puck brakes. Showboatsix's comment suggests adequate braking is available at taxi speeds. At higher speeds the tail may be more willing to lift anyways unless full up-elevator (tail-down) is held. I doubt the brakes will lift the tail in that situation without locking the wheels or fading from heat due to lack of capacity. The best situation would provide sufficient capacity to allow the pilot to lock the wheels at gross-wt-landing speeds on dry concrete. (He wouldn't delibrately do so,...he'd use only sufficient brake pressure to allow the brakes to convert kinetic-energy to thermal (heat) energy, but it'd be nice to have the capability.)

[N3243A]

I wouldn't think it would change anything, the weight of the airplane didn't change so the brakes should still be able to stop it the same!

Well single puck brakes are probably fine up to 8:50 tires. But the installation of Gar Aero Tundra tires or Alaska Bushwheels also require installation of double puck brakes by their STC. This is because of the greater rotating weight and diameter (centrifugal force) of the larger tires and/or wheels I believe.

Bruce

[blueldr]

From personal experience, I felt that too much pressure was required on the pedals when equipped with single puck brakes and maximum braking was applied. I found that it was much more effective and comfortable with double puck calipers.

[HA]

well there ya go, I learned a new thing today!