Sudden Bump Steer

Well, after the new wheels/tires . . . no problems.

Well, after the complete suspension overhaul and subsequent alignment . . . no problems.

Now, this past week, I suddenly have severe bump steer primarily to the left as I am rolling to a stop. If you are not gripping the wheel tightly, it will slip out of your hand and turn completely to the limit.

Nothing obviously wrong from visual inspection. Tire pressures are all good. Everything with the suspension mod appears fine and I re-torqued everything to make sure nothing had come loose. There actually were several of the nuts/bolts that were not quite to spec after all this time but after tightening everything the bump steer problem is still there. Truck drives straight as an arrow at speed.

Was going to go get an alignment check but places here now charge the same for "an actual alignment" as they do for "an alignment check". I guess the setup is the same so even if they don't have to modify anything it is the same price for if they do.

So, before I do that, just thought I would flash a feeler here to see if there is something else to consider?

thanks as usual,

 

I'm sorry I don't really know but I'd check the control arms and tie rods, carefully. Good luck and subbed for cause.. I'm thinking tie rods.

 

Describe, in detail, your 'complete suspension overhaul' and the reason for it. That might help.

 

If your align shop did all the work (or just the align),,give them a call and explain your sudden,,and dangerous,,problem. They should get you right in. How many miles since?.

Expendable income,,once you modify suspension. They will ding you for rack time and parts either way. It's gotta be set good.

Would like to hear your suspension mods also.

You might have something a bit to tight for the implied torque spec.

 

Never heard of bump steer on an IFS. Pretty unusual.
Could be a front brake issue. One caliper might be bad.

 

This ^^^

I too suspect it is a brake issue. It could be a front caliper but It could also be a rear brake issue.

FWIW, the definition of "bump steer" describes when your front wheels steer the vehicle without turning the steering wheel.

"Bump Steer is when your wheels steer themselves without input from the steering wheel. The undesirable steering is caused by bumps in the track interacting with improper length or angle of your suspension and steering linkages."

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

 

https://www.tacomaworld.com/threads/suspension-upgrades-no-lift-wanted.361845/page-3

Starts at post 44 . . .

Boss COs, Deaver J59s, Bilstein 5125s

Done a year ago. Immediate alignment afterwards. So, alignment is a year old and long past any warranty there.

Though it could well be a brake issue, the brakes are usually applied when you are slowing to a stop but it does not actually take application of brakes to make it happen.

The reason I said "bump steer" is because "a bump" as I am coming to a stop is usually what sets it off. Then as it takes the steering to the left, if you aren't grabbing a hold tightly it will take the wheel clear to the limit. Obviously, it is not good practice to let go of the steering wheel as you come to a stop [duh] but doing landscape work etc. sometimes you get in a hurry pulling into the job site.

All said, I do understand it is not the traditional bump steer definition.

Truck only has 63K miles now. Steering rod assembly all still looks pretty good, frankly.

 

You might not have to be on the brake pedal to get that,,if a caliper is dragging a bit. Make sure all of that is behaving as designed. Easy and a good one to check. A slim majority are all thinking smoking brake pads and trashed rotors after that statement. That's not always the case. Sometimes,,but not always.

It might be time for another lap on the rack to check those angles,,after a year of testing your new setup. Just to eliminate the idea. I doubled up on that I know, but they can put it on there turntables and check shit under load alot better than we can do in the back yard. They will have a different view of the underside,,than we get laying on the ground per say. They might spot those worn out steering rack bushings,,as an example.

Subbed, because I want to know what is causing this. Don't let this hang,,do us a favor and report back when it is cured.

 

Well, everything has checked out so I got to wondering about the fact that [because of my particular Tacoma Lean problem] I have been running my DS Boss CO about 5/8" up with the PS all the way down to level the truck out. For some reason, this appears to be causing my bump steer problem. Literally just for grins, I screwed the DS all the way down and now I cannot duplicate the problem.

So, I've got one CO no doubt more stiff than the other since it is screwed up 5/8" to level out the truck and one side of the front suspension takes the bump more severely than the other, starts the wheels to the left, and then perhaps just still forward momentum vectoring side pressure against the now turned wheels just takes them all the way to the limit? Make sense to anyone?

A little early yet to know for SURE that this is it but I am going to run it this way for a week or two to see for sure . . .??

Weird . . .

 

A once big unknown piece of the puzzle,,and congrats. You might check part numbers on your coil springs,,make sure they are matched. That was another idea that was floating. Eilbach and the other included have been known to misbox shit. If you have a rockstar lean going on,,one has to dig a bit deeper sometimes.

 

worn steering rack bushings caused bump steer on mine , when wiggling the tire and rim left and right you could see the steering rack move up and down in the casing, left front wheel was free to flop independent of the steering control so it did some steering for me.
and steering angle can contribute IMO
more rake causes easier unstable steering
less rake causes understeering
anyone who has hooked up to a heavier trailer than the truck is designed for, or jacked the back springs way up has felt it

I have been wondering lately if the rear axle walking can contribute this ( if any mods or flaws set it off) , the rear spring hanging sytem is not very tight on these tinkertrucks, seems like the rear end can just wobble left or right in there as pitch changes

 

Still a little too early to know for sure but problem still seems solved NOT using the COs to take the lean out of the truck.

Question: Why did it take 7-8 months running this way to become a problem? Probably need to check my shock pressure . . . as soon as I figure out how?

 

Fresh parts will run that way. Once you put a bunch of miles running it that way,,then you get your 5/8" wear on the opposing.

Contact the Shock tech line. See what they say about your situation and the charge needed on those shocks. We run 75psi tank on our Eibach Penske setup. They get rebuilt and dyno tuned/graphed every year,,to make sure they match perfectly. You don't need them perfect,,but better than they are it seems. Matching those pressures is a good start,,if you can do it in house. They also might want to take a look at those FOC-ish after you explain.

 

how "immediate" is the jolt? if it's as soon as you press on the brakes or within 7 or so % of braking, it most likely is a brake issue. air in 1 caliper, inefficient caliper, bad fluid, big grooves in 1 rotor causing more surface contact on 1 tire. if it happens when you apply the brakes at a certain point, (when you stop so suddenly that the weight of the truck shifts a ball joint/bushing forward or back, causing the jolt) then it's something in your linkage.

 

Well, on Boss COs, Toytec said there is no "checking the pressure". You have to take the shocks off and see "how they feel compared to each other"?

Seriously?

 

They are not rebuildable or revailve able either. There is reason why they cost a lot lest than a King or Fox or ADS.

 

I was told the shock and/or the spring were replaceable when I bought them. Are you saying you just cannot rebuild the shock itself?

 

Yes. A rebuild involves disassembly of the shocks internals. Replacing the oil and seals an possibly tuning the performance with internal shims, referred to as revalving, either the compression or the rebound or both.

 

Caliper might be dragging

 

Nope, something else is going on. Was merely exacerbated by the DS coil over screwed up higher to get rid of my "lean" problem. Happened twice today. DS and PS brakes and wheels feel [and sound] the same. Rechecked the Deavers out back to make sure something hasn't moved or come loose that might be projecting forward when I hit a bump coming to a stop. No problems there.

Has to be something going on in the steering assembly [??].