Taco Bump Steer? Where to Start?

Hey guys,

So I know there's a thousand steering threads on here but I couldn't find one that answers my question. I bought my taco used with 85k miles and I love it. Only thing is I have a sort of bump steer which I know should be impossible with IFS. Its not horrible but noticeable when I go over bumps the wheel will shift violently to the left or right. I've thoroughly researched the forum and found all of the possible causes i.e. ball joints, control arm bushings, tie rod ends (inner & outer) and steering rack bushings. I can not figure out which of these problems it is. I just had an alignment and the problem persists. I am a pretty capable garage mechanic and now have lifetime alignment on my truck so I'm ready to start replacing parts. My question is what would you experts start with in replacing things? I'm thinking rack bushings>TRE>Ball Joints> Control arm bushings. Is there a sure fired way to figure where this is coming from. No clunks when turning. No obvious play when sitting still and turning the wheel and not a ton of play in general. Just the bump steer.

Thanks in advance and please don't put me on blast if this is a dumb question or has been answered here. Just looking to be pointed in the right direction.

Thanks,
-Cole

 

Also, what rack bushings would you guys recommend and where can I get them from if that's the #1 cause.

 

Should've mentioned. I already checked the tire pressure. Steering fluid etc

 

I've got 285/70R17s on, no lift, lots of trimming and the CBC and no rubbing ha. PSI up front is 34 and rear is 32.

 

u want more pressure in the rear. what ply r u tires?

 

Your caster #'s might be too low, which would cause bump steer also.

 

I'll post up a pic of the alignment numbers when I get out of work. I just had the alignment like 10 minutes ago

 

"In order to accomplish zero bump the tie rod must fall between an imaginary line that runs from the upper ball joint through the lower ball joint and an imaginary line that runs through the upper a-arm pivot and the lower control arm pivot."

http://www.longacreracing.com/technical-articles.aspx?item=8162

 

I always thought more in front less in rear since more weight is up there they're BFG KOs so whatever ply those are. It did this with the stock Dunlop 265s too though.

 

You don't need to post a pic. What were your caster #'s?

 

Hmm so I do have an allpro front bumper adding about 100 lbs to the front. I've also got bilstein 5100s up front. Do you think if I set them at the .85 or next setting it would help with this?

 

Here you go

 

I would say that your low caster #'s are your main culprit. Your truck probably wanders when you hit little bumps on the freeway and stuff.

 

Yeah it does. So how would I fix that? Its sitting at stock height or maybe lower due to the bumper.

 

Thanks for the help BTW

 

If your truck is at stock height, the alignment guys should be able to get your caster #'s to the upper end of the 2.7 degrees, unless your alignment bolts are seized/frozen and they didn't tell you.

 

Nope the bolts are siezed or frozen, good thing I got the lifetime alignment ha. Now they have to do it until they get it right. Why wouldn't they set this for me the first time around?

 

Well, your numbers are actually within the allowable limits, but that doesn't mean the truck will drive good. You could ask them to try and increase your caster and see if that solves the wandering. At least if you do that, you can check that off of the list of things it could be.

 

Okay I'm going to bring it back to them and have them do that. Thanks for the help. I'll follow up and post whether this fixes my problem or not.

 

My truck used to wander all over the freeway when my caster was at 1.6. You'll get more resistance, with higher ca when trying to steer but the truck will hold itself in a straight line better at speed.

Another thing that tightened my steering up was this: https://www.tacomaworld.com/threads/steering-column-fix.88077/
I had less than a mm of play but doing this made my steering feel a lot more solid.