Mailing List lml@lancaironline.net Message #31753
From: <Sky2high@aol.com>
Sender: <marv@lancaironline.net>
Subject: Re: [LML] Re: Tire pressures
Date: Thu, 08 Sep 2005 09:32:36 -0400
To: <lml@lancaironline.net>
In a message dated 9/7/2005 1:45:29 P.M. Central Standard Time, MikeEasley@aol.com writes:
My ES manual says in the Handling, Service, and Maintenance section, IV-12...
 
Nosewheel 32-35 psig, Main tires 55-65 psig.
 
 
Interesting thing is Lancair recommends 6 ply tires for the mains, but the 6 ply tires are supposed to be inflated to 44 psi.  Should we be using an 8 ply tire for the mains?
 
So the book pressures for Flight Custom III's are 44 on the mains 52 on the nosewheel.
 
Is the nosewheel "safe" as far as speed rating, temperatures, weight carrying, etc. at 32-35 psi?
 
This gets more interesting the more I look at it.
Mike,
 
Yeah, more interesting all the time.  From the Aero Crafters catalog:
>>>>>>>
Item#TR-5-8PLY

Tire, 5" 8-Ply 11.40 X 5

Replacement nose tires used on the Lancair 235, 320/360 & the Legacy 2000 plane. The 5" 8-ply is standard.

QTY  EA  @ $16.00 

>>>>>>>>>

Except these are the MAIN tires on the 235/320/360 also.  Wee things that they are, I set my mains to 42 psi and the nose to 32 psi while the tire is rated for 70 psi.   These are the famous "CHIN" tires - clearly marked "Not for Highway Use" - meaning we cannot land on roads although a 60 to 70 Kt touchdown on a rotten runway is no problem (NP for short).

I believe the proper pressure could be calculated - how many square inches of tire support  the weight - let's say at some gross weight my nose wheel is supporting 480 pounds.  At 30 psi there is probably 16 sq in of tire (4 x 4) sitting on the ground. 

All I look for over time is even wear of the tire although I expect more wear towards the center because of the spin up at landing (at least one squeak, but less than three on the mains means NP).  The Chin tires are NP, but the tubes can be -- if not enough talc and air pressure are used, tire sidewall flex can wear the side of the tube to the point that AIR can leak out resulting in a FLAT, nose wheel shimmy notwithstanding.

Luckily, you ES types get to use larger, more expensive (more than $16) certified tires, guaranteed to keep you rolling regardless of runway, grass or highway.  Oh, that's right, you don't have to stick those large wheels inside of a thin performance wing, NP.

Anybody filling their tubes with Nitrogen?  If not, why not?

Scott Krueger AKA Grayhawk
Lancair N92EX IO320 SB 89/96
Aurora, IL (KARR)



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