tyre creep

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tyre creep

Postby banwar » 25 Jul 2010, 10:26

We have received a query form one of our pilots relating to the identification of tyre creep on our B737NG aircraft. i checked the manuals and found definition of tyre creep as rotation/movement of the tire in relation to wheel. We have spoken to the wheels/brakes workshop mechanics who advised that on tire/wheel assembly they align the red dot on the tubeless tire (also known as the 'light spot') with the valve. i couldnt find anything in AMM ATA 32-45 concerning any allowable limits to tyre creep. Can anyone advise if there is any tyre creep limit, the question is, when the red dot wears off which I am told it does do quite quickly, how do they identify when the tyre has crept and whether it actually matters.

BRgds
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Re: tyre creep

Postby Dunny » 25 Jul 2010, 15:00

The term "tyre creep" really only applies to tyres with inner tubes, to stop the inflation valve getting ripped out.

It was standard practice to paint a 1 inch white band on the tyre and hub to identify creep.

Boeing do however provide guidance on the subject for tubeless tyres. They recommend the tyres do not slip by more than 20 degrees.This equates to around 4 inches on a 737 mainwheel.
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Re: tyre creep

Postby IFixPlanes » 25 Jul 2010, 19:19

Maybe the SL 737-SL-32-138-A answer your question:

...
New and retreaded tires should have a red dot painted on the sidewall. This dot indicates balance
of the tire and is located at the lightest spot on the tire. The dot should be aligned with the heavy
location on the wheel. If the heavy location on the wheel is not specifically identified, Boeing
recommends that the red spot be aligned with the inflation valve. If the red spot is not visible on
the tire, it is acceptable to install the tire in a random orientation.
...
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Re: tyre creep

Postby Dunny » 26 Jul 2010, 05:18

The red dot indicates the lightest spot on the tyre. It has nothing to do with creep.
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Re: tyre creep

Postby banwar » 26 Jul 2010, 05:36

thanks everyone for your replies. so it seems that the red dot which is the light spot on the tire is not for creep, but rather for aligning the tire with the heavy spot on the wheel during assembly. Dunny, can you please give me the Boeing document reference that contains the guidance for 737 wheel creep so that i can review it.

thnx
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Re: tyre creep

Postby Dunny » 26 Jul 2010, 13:04

737NG-FTD-32-00012
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Re: tyre creep

Postby banwar » 26 Jul 2010, 13:22

thanks Dunny.
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Re: tyre creep

Postby banwar » 27 Jul 2010, 07:32

the Boeing FTD doesnt advise what to do if the witness mark that we add wears off in service. if it wears off, does that mean that we treat the tire/wheel combo as unserviceable and require replacement?
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Re: tyre creep

Postby Dunny » 27 Jul 2010, 14:52

You have to use your experience and common sense.

If the tyre is losing pressure, change it. Otherwise, I wouldn't worry about it.

If it were an issue, the wheel/tyre overhaulers would be painting marks on the tyres and hubs.
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Re: tyre creep

Postby banwar » 28 Jul 2010, 12:11

thnx Dunny, appreciate your coments
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Re: tyre creep

Postby Stefano » 28 Jul 2010, 18:52

Hi everyone!
As far as I know on all aircraft types the red (coloured) dot is on the lightest point of the tyre, aligned with the inflation valve, to identify a tyre sliding on the rim.
The B737 classic does not mention any check, but I suppose that if anything like this happens the tyre would loose pressure.
In any case I would replace the tyre, because it is not normal...
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Re: tyre creep

Postby Dunny » 28 Jul 2010, 23:01

Have you not read any of this thread.

I give up....
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Re: tyre creep

Postby Stefano » 05 Aug 2010, 22:46

...just to spry some alcohol on the fire...
In LIN thre's an old Yak 40 who has marking not aligned with the inflation valve...
P.S.
Tyres are destroyed but there's no sign of slipping :-)
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