twitchy steering

[goldwing-ghia]

I am building a reverse trike with a 1982 Goldwing and a 1970"s vw beetle front torsion bar suspension. It's all coming out fine except the steering is twichy at any speed over 15mph. When I built it, I squared up the bike on my bench and ran a center line front to back and set the front end to that so I know everything is square. I lightened the suspension by removing the smaller leafs to compensate for the lighter front end and the spring rate is comfortable. Everything has been rebuilt in the front end so all is tight.

As far as alignment goes, I lined up the front rims parallel to the rear wheel as my research indicated. I am running about 4 degrees of castor, 0 degrees camber and 1/4" overall toe in over 24". I also installed a 3/4" sway bar which makes the front end stiffer side to side so it doesn't lean very much. I am running my tires at 20 lbs, down from the 30 or so when I had them mounted. I have readjusted this front end many times but can't reduce the slight side to side wander instability to a comfortable point. I am at wits end on this. Any ideas are appreciated.

Thanks, Bob

 

[rhino 2]

Bob ..Welcome to Trike Talk

 

[Sidecarbill]

Caster is positive yes? Don't know what you mean by 24" toe in. Toe is measured tire to tire. Make sure the steering box is adjusted correctly.

 

[Gorilla]

Welcome Bob. With a self built system like you made your going to have to experiment with adjustments until you get something to work. Maybe even a different tire size might help. More rubber on the ground to give more resistance??? Steering damper???? more toe in?????

 

[goldwing-ghia]

Caster is positive yes? Don't know what you mean by 24" toe in. Toe is measured tire to tire. Make sure the steering box is adjusted correctly.

toe in is measured at 12" from wheel center front & back so there is 1/4" of toe in overall at 24" apart. my tires are 21" diameter. There is no actual steering box. It is a shaft & pitman arm only like an ATV.

Thanks for your response.

Bob

- - - Updated - - -

Welcome Bob. With a self built system like you made your going to have to experiment with adjustments until you get something to work. Maybe even a different tire size might help. More rubber on the ground to give more resistance??? Steering damper???? more toe in?????

The tires are 165/50/15 so the tire is wide enough. I was thinking steering damper although the problem is wander and not shimmy, so I am not sure. I might try more castor and possibly more toe in.

Thanks,

Bob

 

[Jack Klarich]

Welcome to Trike Talk Bob, if your caster is adjustable try a bit more. Do it in small increments and test rides. This should give you more stability with out having to fight the steering. TOO much of a good thing is bad, so go slow on the adjustment. You may also want to shoot for a bit less toe. This can help with the scrub radius of the tires

 

[LarryA]

Going on the assumption that your steering is not returning to center is what you call twitchy ... could it be that your front end is too light, kingpin inclination and front end weight are the main players to get the steering to self center...Only other thought is binding somewhere is the linkages? Agree with Jack about the caster and toe.

 

[goldwing-ghia]

Going on the assumption that your steering is not returning to center is what you call twitchy ... could it be that your front end is too light, kingpin inclination and front end weight are the main players to get the steering to self center...Only other thought is binding somewhere is the linkages? Agree with Jack about the caster and toe.

It steers and turns fine, it just constantly goes slightly left to right so I have to constantly compensate with very slight counter steer. It's like a very slight zig zag. The handle bar triple clamps go to their stops left & right and the wheels are at their max as well so the steering capacity is at its maximum. I am going to shim out the bottom of the beam some more to give me more positive caster, reset toe in again and see what happens. I will keep you posted.

Thanks Guys

Bob

 

[LarryA]

just one more thought...is the rear swing arm mounting tight? if loose the rear of the trike could be steering the front. Hopefully more positive caster will help.

 

[Sidecarbill]

I don't know what this set up looks like. But depending on where your linkage is pivoting and heights perhaps you're experiencing bump steer. Any binding in the front end can also cause this. Seized ball joints or king pins can create the problem you describe.

 

[Lee H. Mann]

It steers and turns fine, it just constantly goes slightly left to right so I have to constantly compensate with very slight counter steer. It's like a very slight zig zag. The handle bar triple clamps go to their stops left & right and the wheels are at their max as well so the steering capacity is at its maximum. I am going to shim out the bottom of the beam some more to give me more positive caster, reset toe in again and see what happens. I will keep you posted.

Thanks Guys

Bob

I would imagine you set the toe while the trike was unladen.

Check for toe changes when weight is applied.

It sounds like a toe adjustment problem.:Shrug:

Darting is caused by too much toe-in.

Your steering geometry is going to be way off because of the shortened wheelbase.

Do like the stock car guys used to do.

Roll the front wheels through water and see what kind of scrub you have.

Also roll it backwards and see if the front wheels follow the same track.:Shrug:

 

[Jack Klarich]

I would imagine you set the toe while the trike was unladen.

Check for toe changes when weight is applied.

It sounds like a toe adjustment problem.:Shrug:

Darting is caused by too much toe-in.

Your steering geometry is going to be way off because of the shortened wheelbase.

Do like the stock car guys used to do.

Roll the front wheels through water and see what kind of scrub you have.

Also roll it backwards and see if the front wheels follow the same track.:Shrug:

Adding weight to the vehicle is a big plus, it helps to reproduce actual normal driving conditions.