8.50 x 6 tires

6319 · Post by **6319** » Sun Feb 28, 2021 11:19 am

I am wondering if any members are using 8.50 x 6 tires on a C-85 powered Cessna 120/140. If so, how is the performance?

8434 · Post by **8434** » Mon Mar 01, 2021 7:00 pm

I have a C-90 and didn't notice much change in cruise speed however the off airport performance is much better. I put on the Aero Classic Smooth tundra tires. They are a few pounds heavier than 6x6s but much softer and absorb bumps and rocks nicely. I've been running them at 15psi but I will probably experiment with 10psi this summer.

Marshall

6319 · Post by **6319** » Tue Mar 02, 2021 9:25 am

Thanks , were there any problems with the installation? Brake calipers, brake lines etc. Is there a need for solid axles?

8434 · Post by **8434** » Tue Mar 02, 2021 12:07 pm

The brake calipers are close to the sidewall, I have to slide the brake pad in behind the rotor and wiggle it into position to get the bolts started. Once its tightened up I have about 1/4" of clearance.

I have hollow steel axles. Bigger tires won't change the forces on the axle since the wheel assembly is the same. There is an STC for 26" tires. In hindsight I would have just gone that big.

phil123 · Post by **phil123** » Sat Mar 06, 2021 3:22 pm

You will loose about 3-5 mph with the 8.50 x 6.

a64pilot · Post by **a64pilot** » Sat Mar 06, 2021 5:27 pm

You’ll also lose rate climb, and oil temp will run higher

klyde sessna · Post by **klyde sessna** » Sat Mar 06, 2021 7:04 pm

I'd bet the speed, rate of climb and oil temp changes advertised here would depend on what tire you are using now.

8434 · Post by **8434** » Sun Mar 07, 2021 10:58 am

I haven't noticed an oil temp change here in Canada, it's more of a matter of keeping it warm most of the year. Rate of climb or angle of climb also hasn't changed much as far as I can tell. I usually pull it off the ground at 45-50 accelerated to 65 then pull back to maintain 65. I've gotten out of a rough strip that's 1500ft long with trees at 4500ft.
I'm usually below 1200lbs, I would change my procedure if I was at gross.

It's all about purpose, if you want to play on rough and short fields 8.50 are an easy choice. 3mph at cruise isn't even noticable if you're playing 50 miles from home.
If you're commuting to work 200 miles away to a grass airstrip then the choice is a different one.

8170 · Post by **8170** » Mon Mar 15, 2021 6:16 pm

I have 850s and a c85 and I haven't noticed much of an issue in performance. The airplane is no rocketship and I cruise around at 85-90 anyway

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8.50 x 6 tires

8.50 x 6 tires

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