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ZUKIWORLD Discussion Forum => Technical Discussion - Performance / Modify => Topic started by: GO_OUTSIDE! on September 14, 2012, 06:47:19 AM

Title: Why is my sammy fishtailing on gravel?
Post by: GO_OUTSIDE! on September 14, 2012, 06:47:19 AM
I am at the end of my build and am having some handling issues. I have a SPOA on stock springs, new Gabriel shocks on relocated lower mounts, an OTT steering kit from Lowrange and new 31" AT's. The steering damper is old but still dampens.

On pavement the truck doesnt want to return the steering wheel to center after a turn and need constant attention to keep it straight. It seems to want to grab and go in the direction of the side of the truck that is weight loaded, either from a steering input or change in road camber. I have been working with the toe in angle on the front end trying to correct this. As I apply more Toe in the on road manners get better but the offroad handling get worse. Currently it is acceptable on pavement and scarey on gravel.

I have adjusted the play out of the steering box but it still drives as if something is loose in the front end.
Title: Re: Why is my sammy fishtailing on gravel?
Post by: fordem on September 14, 2012, 10:31:19 AM
What are your caster angles like?

Chances are with SPOA you have rotated the front axle "top to front" to get a reasonable drive shaft angle, this causes the caster to become more negative (or less positive) and this directly affects the "return-ability" of your steering.
Title: Re: Why is my sammy fishtailing on gravel?
Post by: bentparts on September 15, 2012, 04:07:21 AM
You stated " you adjusted the play out of the steering box " and that imo, is why your steering will not return to center. Most of the slop in our steering systems can be attributed to loose and worn linkage, NOT steering box " play." If the steering box gears are too tight the steering will not self center and they can also bind and be damaged. Try loosening the steering box adjustment back to it's stock adjustment. The best way is to jack up the front, loosen the adjuster while someone else turns the steering wheel back and forth. Then check all your links for play and replace as necessary.
Title: Re: Why is my sammy fishtailing on gravel?
Post by: GO_OUTSIDE! on September 19, 2012, 10:09:44 PM
I put in a new ott kit and only adjusted the play out of the box. I didn't use the spring scale to set it per the manual, but I am pretty certain it is not overly tight. I'm out of town and will double check next week.
Title: Re: Why is my sammy fishtailing on gravel?
Post by: tombstone on September 25, 2012, 06:31:13 PM
OK,how fast are you trying to drive on that gravel??40mph-50m mph or more??Anything over about 15-20 and it could be the road surface!
Title: Re: Why is my sammy fishtailing on gravel?
Post by: bentparts on September 26, 2012, 04:38:29 AM
I put in a new ott kit and only adjusted the play out of the box. I didn't use the spring scale to set it per the manual, but I am pretty certain it is not overly tight. I'm out of town and will double check next week.

Well, if you know about the spring scale, you probably didn't overtighten the box adjustment, and it's just a by product of your lift?
Title: Re: Why is my sammy fishtailing on gravel?
Post by: GO_OUTSIDE! on September 26, 2012, 06:27:40 AM
At around 50mph it starts to give me trouble. My Tacoma doesnt give me any trouble at all and I run the same road at 70mph when Im late for work.

Bentparts, do you think if I fab'd up a panhard bar it would help? Today it fely as if the front right wheel caught an invisible  groove and pulled it quickly to the right.
Another symptom is the wheel wants to pull to the right for a few miles and then returns to normal. I am suspecting a sticking front caliper but havent had a moment to check.
Title: Re: Why is my sammy fishtailing on gravel?
Post by: FBJR on September 26, 2012, 08:28:22 PM
You have a short wheelbase solid axle (50 year old design) vs an IFS with rack and pinion longer wheelbase vehicle.   

Even taking the slop out of the gearbox, you normally back it off a little.

A Tocoma and lifted Sammi will not drive the same. Not surprised it fishtails a little at 50mph! regardless.
 

Title: Re: Why is my sammy fishtailing on gravel?
Post by: bentparts on September 26, 2012, 09:11:17 PM
I'd check the front caliper first, but I'd have to agree with FBJR, might just be a short wheelbase issue. I don't have any real experience with modified sammy suspension, maybe someone who does will chime in. Check your tire pressures too.
Title: Re: Why is my sammy fishtailing on gravel?
Post by: Pest! on September 30, 2012, 08:29:54 AM
Your Sammy is very light and has a very short wheel base so it will be quick to swap ends in the rain and on gravel roads and a sticky caliper would only make it worse. The reason several company's have made reversed front springs is that having leaf springs shackled at opposite ends makes for a vehicle that will change directions when the suspension moves.  When you compress a spring it moves the axle away from its fixed attachment to the frame steering the Zuki away from that side. on uneven roads it will squirm and even worse under braking.  Also if your front axle was tilted even a few degrees in the process of lifting it your caster will be off and not return the wheel to center as others have said. 
Title: Re: Why is my sammy fishtailing on gravel?
Post by: GO_OUTSIDE! on October 02, 2012, 06:21:52 AM
I really need to slap a protractor on the kingpin and check my camber.
I had a wrangler for years that I used to wheel as much as possible. It didnt squirm like this. Same technology.
I lowered my tire pressure from 36psi to 30 psi and have noticed an improvement.
Title: Re: Why is my sammy fishtailing on gravel?
Post by: crewcabrob on October 02, 2012, 06:38:01 AM
From what I understand so far, tire pressure could make a huge difference in the manners of your Samurai.  Here is a recent discussion about tire pressure:

http://www.zukikrawlers.com/showthread.php?t=49075 (http://www.zukikrawlers.com/showthread.php?t=49075)

Rob
Title: Re: Why is my sammy fishtailing on gravel?
Post by: GO_OUTSIDE! on October 02, 2012, 02:05:48 PM
Thanks Rob,
That is a very helpful thread. I was beginning to wonder how low i could run the tire pressure on the street. I would not have gone below 28psi for extended travel without seeing that.
Title: Re: Why is my sammy fishtailing on gravel?
Post by: bentparts on October 02, 2012, 03:53:26 PM
Good lord man, 36 lbs! I'm surprised that thing didn't bounce into low earth orbit first big bump!
Title: Re: Why is my sammy fishtailing on gravel?
Post by: crewcabrob on October 02, 2012, 06:03:33 PM
Thanks Rob,
That is a very helpful thread. I was beginning to wonder how low i could run the tire pressure on the street. I would not have gone below 28psi for extended travel without seeing that.

Not a problem.  It was a crazy discussion that I thought you might appreciate.

I'm going to try low pressure, something around 20psi and see what happens.

Rob
Title: Re: Why is my sammy fishtailing on gravel?
Post by: Bigzook on October 02, 2012, 06:29:33 PM
My 4 door kick started "floating" on the gravel roads at about 80-85M.P.H this last weekend. Scared my wife when the car drifted to the right at 90. I imagine a sammy could experiance this at lower speeds with the shorter wheelbase.
Title: Re: Why is my sammy fishtailing on gravel?
Post by: crewcabrob on October 02, 2012, 07:06:23 PM
My 4 door kick started "floating" on the gravel roads at about 80-85M.P.H this last weekend. Scared my wife when the car drifted to the right at 90. I imagine a sammy could experiance this at lower speeds with the shorter wheelbase.

Sign up for the next rally in your area.  80 - 90mph on gravel?  You're crazier than I ant to be.  :)

Rob
Title: Re: Why is my sammy fishtailing on gravel?
Post by: GO_OUTSIDE! on October 03, 2012, 04:06:07 AM
Good lord man, 36 lbs! I'm surprised that thing didn't bounce into low earth orbit first big bump!

It tried, the tire shop sent me out with 42psi! Needless to say I was very disappointed in my first ride in a samurai. Things are definitely improving.
Title: Re: Why is my sammy fishtailing on gravel?
Post by: bentparts on October 03, 2012, 05:25:17 AM
I know my Tracker is heavier than a Sammy, but for reference I've found that with BFG 32X11.50 AT KO's To get a good compromise between handling and ride quality I ended up with 23/24 front and 19 rear for tire pressures. If I'm doing some serious off roading that requires climbing rocks or a traction sucking surface I go as low as 15/12.  When I drove out west I bumped that up to 32 and 27 to get better fuel economy but it rode like a wheelbarrow. 
Title: Re: Why is my sammy fishtailing on gravel?
Post by: GO_OUTSIDE! on October 05, 2012, 05:45:50 AM
And the winner is... Tire pressure! Doing nothing other than reducing tire pressure from 36 to 27psi has transformed the samurai from a dangerous swerving mess into a stable vehicle. Thanks to all!
Title: Re: Why is my sammy fishtailing on gravel?
Post by: crewcabrob on October 05, 2012, 06:37:33 AM
Glad to hear it was a simple fix.

Rob
Title: Re: Why is my sammy fishtailing on gravel?
Post by: bentparts on October 06, 2012, 04:27:50 AM
A few seconds of psssssssssssst, is one Cheap fix!  Good for you!