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  #11  
Old 03-10-2020, 07:14 PM
PilotjohnS PilotjohnS is offline
 
Join Date: Jan 2016
Location: Southwest
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Default Divide by two

Quote:
Originally Posted by RV8Squaz View Post
Hey Ralph,

FYI, 1" displacement, 36" from the axle gives me 1.59 deg. Someone please check my math.
It should be 1/2 per wheel for the calculation since you want each wheel to the centerline , not to each other.
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  #12  
Old 03-10-2020, 07:17 PM
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tomkk tomkk is online now
 
Join Date: Apr 2014
Location: Port Orange, Fl
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Quote:
Originally Posted by pilotyoung View Post
Jim,

Some people say those tires are much heavier than the original tires. Has that created any problems for you?

Thanks.

John
Yup, mine were heavier. But, I got 265 landings on the original tires, over 900 on the Desser Retread Elites. Undoubtedly at least some of that is more experience with the aircraft but IMHO it was mostly the tires.
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  #13  
Old 03-10-2020, 07:17 PM
swjohnsey swjohnsey is offline
 
Join Date: Nov 2018
Location: Kingsville, TX
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Instead of trying to calculate the toe-in you need you can measure it with this clever little tool.

https://www.ebay.com/itm/Gunson-G400...kAAOSwa9FbBpFV
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  #14  
Old 03-10-2020, 07:32 PM
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tomkk tomkk is online now
 
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Quote:
Originally Posted by swjohnsey View Post
Instead of trying to calculate the toe-in you need you can measure it with this clever little tool.

https://www.ebay.com/itm/Gunson-G400...kAAOSwa9FbBpFV
Interesting. I wonder how it works - it looks like it might depend on the side friction of a tire that isn't rolling exactly straight over the gauge. If that's the case, I wonder how well it would work on or aircraft tires - our tires have such a smaller footprint than auto tires, especially our high camber tires.
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Port Orange, Fl
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RV-12 N121TK ELSA #120845; first flight 06/10/2015; 700 hrs as of 02/2020
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  #15  
Old 03-10-2020, 07:42 PM
swjohnsey swjohnsey is offline
 
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Location: Kingsville, TX
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Quote:
Originally Posted by tomkk View Post
Interesting. I wonder how it works - it looks like it might depend on the side friction of a tire that isn't rolling exactly straight over the gauge. If that's the case, I wonder how well it would work on or aircraft tires - our tires have such a smaller footprint than auto tires, especially our high camber tires.
It measures scrub. There are two platforms separated by rollers so very little friction. There is a pointer attached to the top platform that indicated too much toe in or toe out. I've never tried it on the airplanes but it works well on my Lotus 7 with around 400 lbs/wheel.
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  #16  
Old 03-10-2020, 09:39 PM
DHeal DHeal is online now
 
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If you are looking for a really long straight reference beam to measure toe-in/toe-out consider using two 4'-6' fluorescent light bulbs each placed against the side of each wheel hub or brake rotor. Be careful though -- the bulbs tend to shatter if mishandled.
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  #17  
Old 03-10-2020, 09:45 PM
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Piper J3 Piper J3 is online now
 
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Quote:
Originally Posted by pilotyoung View Post
Jim,

Some people say those tires are much heavier than the original tires. Has that created any problems for you?

Thanks.

John
No problems. Need to shave wheel fairings for 1/2" tire clearance.
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  #18  
Old 03-11-2020, 01:11 PM
Ralph Inkster Ralph Inkster is offline
 
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Location: Calgary, Alberta
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Quote:
Originally Posted by tomkk View Post
That's what I got too. You need about a 5' straight angle, not 3', to get 1" = 1 Deg.
Yep You're all right! Shouldn't trust old guys, or should give them less beer.
The length should be 57.3" to get a 1" sweep to equal 1 degree.

General concept is still simple & easy to do though.
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  #19  
Old 03-11-2020, 01:23 PM
Ralph Inkster Ralph Inkster is offline
 
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Location: Calgary, Alberta
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Quote:
Originally Posted by PilotjohnS View Post
It should be 1/2 per wheel for the calculation since you want each wheel to the centerline , not to each other.
NO, we are not suggesting a 1 degree toe in or out. Was just suggesting a different way to determine each wheel's angle before shimming.
Yes, you would have to add the two results to set your desired overall toe in / out.
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  #20  
Old 03-11-2020, 03:15 PM
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rvbuilder2002 rvbuilder2002 is offline
 
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Remember that the toe value check is relative to the aircraft center line. Not the two wheels to each other.

It is not uncommon for the production tolerance to have one leg with toe in and the other with toe out. If checked in relation to each other, it may look like it is perfect but your airplane will move in a straight line yawed to one side.
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