SO what causes that wheel shimmy/bumpsteer after installing bigger tires?

thats exactly my point. What is “designed” into a truck that makes it drive with larger tires. The only thing I have read that makes sense to me is the scrub idea. Wider tires scrub more. So I would assume a new alignment spec, not necessarily the factory spec would maintain a certain amount of scrub to keep shimmy down. Cheers to that @splitbolt

I might have to take it to an offroad shop and have them really mess with alignment setting and ignore "factory spec" and really experiment.

 

Weight. I thought I made that clear?

You want a good example? Throw some 425/65r22.5s on the steers of your work truck and see how it drives. Then go drive a truck that comes stock with the 425s

 

I understand adding larger/heavier tires makes the ride worse. Im just trying to figure out exactly why it causes it to drive worse. If I can figure out exactly what it is I can fix it. I would like to see if a f150 with 35's drives the same as a raptor. Obviously it doesn't. But did ford beef up actual steering rack for raptor? or did adding some fox coilovers compensate for tires. Or are the alignment specs different for f150 vs raptor.

 

Just to be more precice, it's not really bumpsteer. Bumpsteer is change of toe as the suspension cycles. This is more of a steering feedback/tramiling thing.

If you've not ever had an alignment, start there. Your factory caster is probably +1.8 or so. Getting that number up will do the most to improve the feel.

 

The steering rack is a little baby hydraulic piston right? Would it lift up a dump truck bed? You are asking it to move more mass than it was engineered for. That YouTube guy has replaced his twice.

Yes, Toyota knows every ahole that buys a Tacoma puts heavy ass KO2s on it. Maybe they should have put a beefier rack in it. But that adds weight and adding weight lowers fuel economy and fuel economy trumped just about every design decision that went into this truck.

I suspect if there isn't already there will eventually be an aftermarket HD rack. Maybe the stock pump has the displacement to handle a larger one or maybe it will need to be upgraded as well.

 

Now we are cooking. I’ll look into the alignment and call up some local off-road shops and see what they do for upgrading the steering.

 

You may want to hit up @BigMike on the steering rack.
Solo Motorsports has some stuff too.

 

To be honest, he had to replace it twice because he didn't do it right the first time.

Good luck. Too many factors and a lot of people with rudimentary knowledge = a crapton of useless, non-specific answers. It is best to take it to a professional.

 

I was gonna take it to solo to get aligned anyways haha.