Nose Gear Tire Pressure CH 750 STOL

Little bit of tire rubbing on pilot side of nose gear when we towed the aircraft for the first time today. Rubbing is slight and against about 1/2-2/3 if tire wall.
Ideas:
1. Pressure of tire: 15 lbs PSI - is this correct?2. Nose wheel tire slightly out of round due to sitting or manufacturing tolerances? A local 701 owner suggested this when I showed it to him at 2W6 today.
3. Tire rubbing issue appears that it would be resolved by shortening the copilot side wheel spacer 3/32" while lengthening the pilotvside spacer.

We are 5-7 hours from completion after moving to 2W6 from the garage and re-assembling (left to do: gelcoat the cowling and reinstall it, renstall seats, rivet rear windows in, rivet inboard top wing panels in place, re-install prop.)

Lots of folks loved the plane at the airport open house today. Lots of interest in experimental aviation, Zenith and our Viking 130 (which runs like a dream!).

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Permalink Reply by Loren Warner on October 8, 2017 at 10:48am

By the way, while you did install the four fork mounting bolt per the plans, you might consider turning them nuts up as Wayne Tyson mentioned.

Permalink Reply by William C Cooper II on October 8, 2017 at 6:06pm

Since the tire rubs mostly on 1/2-2/3 of the tire, I am leaning towards a mis-shapen/bulging tire...  I have the tires set at 15 PSI.  Lowering the pressure to 12 PSI did not stop the rubbing.  I can't imagine that increasing the tire pressure would do anything but make the rubbing worse by making the tire bigger...

The spacers are the correct ones and on the correct sides...(longer spacer on co-pilot/passenger's side.) At this point, I think I will get another tire and see if it is more uniform and does not rub.  I will save the current nose wheel tire as a spare for the mains, where fitting inside a fork isn't an issue!

Permalink Reply by Wayne Tyson on October 8, 2017 at 2:47pm

Wow! And I thought mine was close! But you seem to be clearing the bolts, which mine wasn't. My A&P buddy says that the three threads rule isn't set in stone, but one should dab some orange marker paint on and add checking it for movement on the exterior check list.

I'd like to know how much flexing the tire body does in use. I'd like to lower the pressure for off-pavement stuff and increase it for paved surfaces. Next time I'm at the hangar, I'm going to check, but I thought there was a range of pressures allowed.

Thanks for bringing this issue up--I'm learning (no fake news or alternative truths, I hope).

WT

Permalink Reply by Joe Hopwood on October 8, 2017 at 4:17pm

I believe the rule is 1 to 3.  Looks maybe like a shorter bolt would be good here.

Permalink Reply by Loren Warner on October 8, 2017 at 6:10pm

If you google the Carlise web site, you'll see these are golf cart tires and there is only a maximum pressure.   It's your aircraft and you can set it to whatever pressure you want, but for me, knowing it's the pressure that seals them, I'm setting to maximum pressure.  

As for Nylocs, 2 threads is standard per Zenair construction standard (attached), which is from FAA AC No: 43.13-2B for certified aircraft.  As a QA inspector in submarines it was only one thread. Go figure.  In Experimental, it's really whatever you want, but anything less than flush is asking for failure.  

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Permalink Reply by Samuel Warner on October 9, 2017 at 12:31am

This is what ours looks like https://youtu.be/0GQlvZc2ikg


Permalink Reply by William C Cooper II on October 21, 2017 at 5:37pm

Update!  We ordered a new tire (WalMart $52.41 - free delivery to the house).  We put it on today and all is well.  The original tire was misshapen/bulging on one side.  

Permalink Reply by Loren Warner on October 21, 2017 at 5:43pm

Glad you got it resolved.  Zenith is really good replacing bad parts.  Maybe you should ask them to send you a new tire for spare.

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