Nose wheel shimmy

[Bill3558]

My CTLSi is developing a wheel shimmy when landing. Any suggestions on how to fix that? 
Many thanks. 

[Anticept]

Keep the nose wheel off the ground until it won't let you.

Land and take off with 15 degrees or greater flaps.

There is a pin in the nose strut that wears down. Have a look at that too.

[Roger Lee]

The minimum is to replace the front strut pin and maybe the red polyurethane spacers. The longer this goes on the worse it will get and it will cause more damage.

Push the tail down and see if the front wheel wobbles left and right.

[Tom Baker]

I had a customer have one develop a shimmy just a few hours after its first condition inspection, with less than 100 hours total time. We had changed the nose tire and tube due to the cheap Midas factory tire having a leak. The new Aero Classic 4.00x6 tire developed a belt separation causing the issue. That is a common issue with these tires. It will cause them to go out of balance, vibrate, and shake. The tell tale sign is it develops a lump causing a strange wear pattern, and I have even seen splits in the sidewall of the tire.

[Roger Lee]

p.s.

All aircraft tires should be balanced. I have never seen one in balance and some have been so bad I tried 20 weights and they were  still off. Those go back to the factory.  Lifting the nose wheel and trying to move it left or right will tell you if the front suspension pin needs to be replaced. If it wiggles 1/4” or more replace it.

[Anticept]

If you order from desser, ask them to balance the tires before shipment. They will put patches inside to balance them. Then it will make it easier to balance on the axle.

[Tom Baker]

1 minute ago, Anticept said:

If you order from desser, ask them to balance the tires before shipment. They will put patches inside to balance them. Then it will make it easier to balance on the axle.

Is that for the 4.00x6 tires?

[Tom Baker]

Not that it will effect shimmy, but also check for up and down movement in the strut. If you have any plan on replacing the elastomeric suspension bushings.

[Anticept]

Don't think they balance 4.00x6 because they're so small and lightweight. I always just ordered a bunch of various tires and asked for balancing.

[Towner]

All 3 of my tires were way out of balance when I bought the plane. Only noticed a little on the ground, but shook enough on rotation to really get my attention.

Using Tom’s advice, I balanced the mains while still on the axle on the plane. Worked great.

[Tom Baker]

Here are a couple bad tire pictures.

[CT_MATT]

Tom, I have seen this strange “wear” for years and thought it was my application of brakes until my nose wheel had enough hours that they look just like the pictures you shared. I balance all 3 and am typically very careful with brake application but, I guess these are just not high quality 

[Tom Baker]

33 minutes ago, CT_MATT said:

Tom, I have seen this strange “wear” for years and thought it was my application of brakes until my nose wheel had enough hours that they look just like the pictures you shared. I balance all 3 and am typically very careful with brake application but, I guess these are just not high quality 

It is definitely a tire issue. It is caused by a belt separation in the tire, and it happens far to often. I have replaced more tires due to this issue, than those that were wore out. The sad thing is that these are out best option for the small tire that I am aware of.

[Tip]

We recently had a 2014 Si with all of the suspension pucks smashed out. There was at least 2” of travel up and down. The plane had around 300 hours.

[FlyingMonkey]

I always balance my 4.00x6 tires...they sometimes take a lot of weight because they don't factory balance them like the 6.00x6 tires.  If you don't balance them you'll feel them shake on the takeoff roll.

I had one 4.00x6 tire go bad with a bulging sidewall, otherwise I have not had too much trouble with them.  The QA on them does seem a little less rigorous than on the 6.00x6 tires.  They make up for that by being WAY easier to get the tires on & off the wheels.

[Bill3558]

Finally had some time to work on the plane today. Got some cement blocks and pulled the tail down. Play was about 1/4 inch. But a good look at the tire revealed the problem . Had plenty of tread but it was badly cupped and had flat spots. 
Replaced the tire and did some pattern work this evening. No more shimmy.
Thanks for the help and suggestions.