Front Tire Wobble

[Hec In Omaha]

Howdy All,

Just installed my motor on my Azuza Side car build. The build is getting close to being completed. I rigged a wire to the throttle and gave it a go! Brakes a la Fred Flinstone:thumbsup: The bike handles good but at higher speed the front end starts to wobble back and forth. I don't know if it will do it with the cart off. The Azuza forks were replaced with Yamaha PW50 units along with a Yamaha head tube. Any suggestions or things to check?

As always thanks in advance.

Hec

 

[manchester1]

Those wheels don't really run that true. If your bearings are new and your spacers are correct try this. I had the same problem with those new wheels. Take the wheels apart and try the halfs in different positions. Each time you try the different positions, spin the wheel. It worked pretty good for me. I hope you understand what I mean.:laugh:

 

[OND]

I understand Karen..:thumbsup:.and thats some good advice.

 

[Hec In Omaha]

Karen,

I noticed that the tire itself is out of round. If I spin it on the axle you can see that the tire itself is not very true. The tires I bought were cheapie Chinese units I found on Ebay. If I understand your procedure correctly, I am basically just re-clocking the rim halves? I'll give it a try!

thanks

Hec

 

[Havasu Dave]

In addition to your wheel half and tire round checks, you might want to revisit a post I made on this very project in January.

 

[Hec In Omaha]

Those wheels don't really run that true. If your bearings are new and your spacers are correct try this. I had the same problem with those new wheels. Take the wheels apart and try the halfs in different positions. Each time you try the different positions, spin the wheel. It worked pretty good for me. I hope you understand what I mean.:laugh:

Karen,

I don't think I can re-clock the rim halves. If I do the hole for the valve stem would need to be re-drilled. Every one of those cheap Chinese Tires have a wobble. I can spin them on their axles and watch the side walls move in and out and watch the tread move in and out. I am thinking of using Michelin S83 tires. They are 60 MPH Rated. What do you think?

Hec

 

[Roadmaster75]

Interesting issue…..
I am NOT a side car expert, but I have built and messed with enough hot rods and race cars to appreciate the
concepts of caster, camber, and toe-in. Once you have more than 2 wheels in a straight line you introduce the effects of wheel alignment.
Looking at your set up I suspect that
caster on the sidecar is irrelevant; but, it could be that camber or toe-out is providing a
lateral "push" to the front wheel. I'll bet that the bike runs straight and true with out the sidecar attached?

If so, perhaps a little negative camber (like a dirt track stock car) on the sidecar would help stabilize the
whole set up. Ensuring a bit of toe-in ( as opposed to "tow-out") might also help.

It's amazing how just a couple of degrees one way or the other affects how a car steers and stays on a straight line.
I suspect something similar is afoot here …
Let us know what you observe!

 

[Havasu Dave]

Interesting issue…..
I am NOT a side car expert, but I have built and messed with enough hot rods and race cars to appreciate the
concepts of caster, camber, and toe-in. Once you have more than 2 wheels in a straight line you introduce the effects of wheel alignment.
Looking at your set up I suspect that
caster on the sidecar is irrelevant; but, it could be that camber or toe-out is providing a
lateral "push" to the front wheel. I'll bet that the bike runs straight and true with out the sidecar attached?

If so, perhaps a little negative camber (like a dirt track stock car) on the sidecar would help stabilize the
whole set up. Ensuring a bit of toe-in ( as opposed to "tow-out") might also help.

It's amazing how just a couple of degrees one way or the other affects how a car steers and stays on a straight line.
I suspect something similar is afoot here …
Let us know what you observe!

I've mentioned trail to him three times now. I guess he isn't interested. It's a big deal when you swap forks. Nothing to do with the side car. If he's running zero or positive trail on the forks, he will have wobble. Period.

 

[Hec In Omaha]

Havasu Dave,


I took your recommendations seriously. The fork angle is 30 Degrees which is exactly as what was installed on the Azuza frame from the factory. I figured that fork rake would work. Please look at the attached and see what you think? Am I missing something?

Hec

 

[Hec In Omaha]

Roadmaster75,

All three wheels are just about perfectly parallel to each other. The Side Car wheel does have 1/32" of toe in. If I push the bike with the side car attached, it has a slight tendency to pull to the left. I think that is what you want with a side car. This will counteract the tendency of the bike to turn tight under acceleration.
I can add more toe in by inserting washers in-between where the side car and mini bike frames come together. I'll add a couple of washers and see what it does and report back.

Thanks

Hec

 

[Havasu Dave]

Havasu Dave,


I took your recommendations seriously. The fork angle is 30 Degrees which is exactly as what was installed on the Azuza frame from the factory. I figured that fork rake would work. Please look at the attached and see what you think? Am I missing something?

Hec
View attachment 72832

It's hard to tell from the photo, but it looks like you're pushing the front, not pulling it. Where those lines intersect on the ground tells the trail. Length of the forks if different from stock will affect trail, even if the neck angle is identical, (rake) and the trees maintain the same angle as original. I'd check it with a straight edge for the neck angle, and a plumb bob for the axle. Use a bit of tape and see where they intersect. Axle location (plumb bob) should behind the location derived from the neck angle and carried out to the ground. If so, decreased neck angle would fix it.