Front end shimmy with 37s, NOT DW

[FLYINHIE]

I took the Bronc on a shake down run. Refer to my build page.

I've gotten rid of the Death Wobble. I do not have the violent shaking anymore. I do get a bump induced shimmy though. Especially on those old paved bumpy county roads. The Front end is TIGHT. Remember everything is new and solid.
I've taken it to the alignment shop and the toe in is dialed in and my caster/castor is right at 9 degrees. I'm running 37s with beads inside for balancing. I'm wondering if I need to either take out some castor or install a steering dampener or both. Has anyone else had this type of issue. It feels like a shimmy you get when your steering is out of alignment but it is initiated by certain bumps in the road that causes everything to get out of balance so to speak. For the most part it would settle itself back into sync but a couple times I had to tap the breaks to break the ocilation. ANy ideas?

Update. Just got off phone with WH and they suspect what I suspected. Possibly too much castor. I'm going to reverse some of the castor with
C-Bush and see what happens. Any other thoughts, I'm open.

[SonicDonkey]

Re: Front end shimmy with 37s, NOT DW

Definatly too much caster, shoot for 5-6 degrees IMO.

J

[DirtDonk]

Re: Front end shimmy with 37s, NOT DW

Anything new to report?
If you haven't gone to the trouble yet, before you put the new C-bushings in maybe you can run one or both of the front tires to the back to see if the frequency or severity of the shimmy changes?

Just playing devil's advocate here and thinking it could still be a tire issue. Maybe even the bead-type balancer method could contribute? Long shot, as I've never heard of that before, but just a thought.

I would think that a stabilizer, at least temporarily, could let you see if that's going to help. Any way to borrow one, rather than buy a new one as an experiment?

In fact, to me it sounds almost like a Death Wobble that can't quite make it. It wants to, but because you have so much new tight stuff up front, and possibly because you have so much caster, it can't quite make the transition.
Just the fact that you said once in awhile you have to tap the brakes to get it to settle down says that it's trying to become a DW.

That's just speculation of course. I don't remember your DW thread here, so I'll go looking for it and read just what's been done.
Are the tires the same ones you had before?

It's not that the extra caster might not be at fault of course. It's just that it's probably quicker to rotate the tires than it is to change C-bushings.

A steering stabilizer, while more of a Band-Aid kind of thing, might still be just enough to keep it from bugging you.

Good luck.

Paul

[FLYINHIE]

Re: Front end shimmy with 37s, NOT DW

Tires are new.
Changed C-bush and took out 4* of castor which brought my castor down to 5* overall. The problem seems fixed. I haven't been able to drive it too much but prelims suggest that the castor was too much. I am still getting some tire wander but I attribute that to the large tires. Perhaps a stabilizer would help that. At this point I'm considering it to be a non issue. In the course of switching C-Bush, I found out that my pitman arm wasn't seating well on the sector shaft and was somewhat loose, so I switched out pitman arms and that solved that problem.
Thanks for the inquiry though.

[DirtDonk]

Re: Front end shimmy with 37s, NOT DW

Sounds like you're good to go then! Glad to hear it.
You headin' out on the trail this week?

Paul

[FLYINHIE]

Re: Front end shimmy with 37s, NOT DW

Sounds like you're good to go then! Glad to hear it.
You headin' out on the trail this week?

Paul

Not really. I have family coming in from out of state tomorrow. Going to be at Loon Lake during staging but just camping. Taking my little nephew camping with my sister and her husband. I'm gonna bring the Bronco up and will probably head into the trail for a short distance just to give the little guy a taste of the rocks but all in all just camping for one night then home. Next run though. If nothing gets in the way.

[FLYINHIE]

Re: Front end shimmy with 37s, NOT DW

Drove to work today down Latrobe road. Latrobe is somewhat curvy and bumpy. Bronco is all over the road. I'm really tired of tweaking this front end to get it to handle well on the road. Wants to dive into the corners, at least that's what it feels like. I'm wondering if I took too much castor out and should bump it back another 2*. That would put it right about 7* total castor. Or I wonder if something else is going on. FRUSTRATING!!!!

[jamesroney]

Re: Front end shimmy with 37s, NOT DW

Drove to work today down Latrobe road. Latrobe is somewhat curvy and bumpy. Bronco is all over the road. I'm really tired of tweaking this front end to get it to handle well on the road. Wants to dive into the corners, at least that's what it feels like. I'm wondering if I took too much castor out and should bump it back another 2*. That would put it right about 7* total castor. Or I wonder if something else is going on. FRUSTRATING!!!!

What is the brand and type of tire, and what are these "balancing beads?"

I will let you borrow my 35 inch BFG's. At 7 degrees of positive caster and 1/8 inch of toe...I'll bet your Bronco will track straight as a string.

I drive mine with only my knee on the wheel to hold it mostly straight.

[FLYINHIE]

Re: Front end shimmy with 37s, NOT DW

Tires are BFG.
http://www.counteractbalancing.com/c...echnology.html

It's not the tires. I'm going to go through again and check my front end. There is one thing that might be causing the problem but I was waiting until the last resort to change it because it envolves taking my radius arms apart and re-working them. I think I've reached my last resort.

[CityHick]

Re: Front end shimmy with 37s, NOT DW

Wants to dive into the corners, at least that's what it feels like. I'm wondering if I took too much castor out and should bump it back another 2*. That would put it right about 7* total castor. Or I wonder if something else is going on. FRUSTRATING!!!!

Mine behaved a lot like that - diving into corners a scary amount during my first summer on the road, worse on bumpy roads. Mine's sitting at about 5* castor and always has been. My problem was a combination of too much toe-in and shocks that were not up to the task. Perhaps I missed it but what shocks are you running? I started out with pro-comp explorers and the vendors were telling me I needed double shocks. I went with single Rancho reservoir shocks (adjustable ones) which helped, but when the alignment shop backed out the toe, my problems were solved. I will have to dig out the alignment shop's computer printout to find my exact settings for you.

[DirtDonk]

Re: Front end shimmy with 37s, NOT DW

Too much toe-in, bad tires, roll-steer (same as bump-steer only different), and probably other things can cause the diving into a corner.
Never heard of too much or too little caster doing that though. And even though "every Broncos is different", mine never had that issue even at 2 degrees of caster.

A loose rear end can cause that front-dive feeling too, so even though your rear end components are probably fine, don't overlook that area either.
Maybe everything just needs a good re-torque now that you've been driving it for a bit?
How many miles have you put on it since the build-up?

Paul

[FLYINHIE]

Re: Front end shimmy with 37s, NOT DW

How many miles have you put on it since the build-up?

Paul

Few hundred

[FLYINHIE]

Re: Front end shimmy with 37s, NOT DW

I went with single Rancho reservoir shocks (adjustable ones) which helped, but when the alignment shop backed out the toe, my problems were solved. I will have to dig out the alignment shop's computer printout to find my exact settings for you.

I moved some front end geometry around and it seems to have helped quite a bit. I moved my tie rod up TRO, shortened my drag link. Now my drag link and trac bar are super close in angle and only a few inches different in length. Think I was getting some bump steer which was exagerated on twisty roads.

I'm using single Bilsteins. Mine would basicly want to continue steering into the corner instead of wanting to return back to nuetral(center) when turning. Now that I've changed my front end geometry it is much better but not perfect and I'm wondering if a little more toe out would help even more. If you get a chance can you see what your alignment shop did, if it's not too much trouble to dig it out. I did back mine out just a bit. Not sure what is too much and what is not enough.

[DirtDonk]

Re: Front end shimmy with 37s, NOT DW

Hopefully it's listed in inches. Otherwise you gotta break out the old slide-rule to figure out degrees vs actual tire size or whatever it takes to convert.
You're good with numbers though, right? Maybe someone can put together a nice little spreadsheet/calculator showing the conversion of degrees of toe-in to inches for a given tire size.
Kind of like the gear ratio vs tire size vs speed vs rpm.

That'd be cool!

Paul

[CityHick]

Re: Front end shimmy with 37s, NOT DW

I can't seem to find that printout with the alignment specs... got a few more places to check where it might be but so far no luck. I'll let you know.