Ride Height Question

[DaveNY]

I have an ongoing problem with wandering. I have just installed new tires and still have the same problem and am determined to find it. Last set of tires wore perfectly,no play or loose joints. Checked ride height and it was in spec. Then realized that I am no longer riding on 245's but last set and new ones are 265's. Question is sould the difference in tire height be included in the ride height spec.

[DmaxMaverick]

There's a lot of "science" involved when we change any part of the suspension. Most of the time, the science doesn't care, and things go on as before. If you are setting your ride height at a specific value (like the Z height set at the factory) after installing taller tires, it can certainly effect suspension performance. Another thing in the equation is airflow. Raising the truck as little as 1 inch can change the aerodynamic characteristics enough to effect the ride feeling. Usually, just changing tire size, like 245 to 265, will have little to no effect. If you "compensated" for anything, it can be exponential. Or, it could be coincidental with component wear that just happened to decide to change the same time you changed tires. Guessing is part of the diagnostic process with this stuff.....

I do a LOT of mountain road driving (I live in it, and can't go anywhere near home on a straight road). Because of this, I have all my vehicles aligned with a little less positive camber (about 50% of spec). This, I've found over the years, lends to better tire wear and control on the winding roads (and less "bump steer" on our fine pavement). Unfortunately, a side effect is a little less stability (wandering) on the straight roads. I don't notice it now, but I can instantly tell if I drive another vehicle that hasn't been "compensated".

[DaveNY]

I have been told by quite afew people that this fairly common with this front end, some have conquered it with alignment but it seems that this set up is inherently sloppy. My complaint is that you can never stop driving the truck, a quick look at a bill board and the damn thing takes off on you. Yet I can leave go of the wheel and it goes die straight for 500 feet on local roads. I read a post on some one eliminating the problem with a ride height adjustment. I checked mine and the Z height is right on. I am not familiar with the caster adjustment proceedure but I have made an appointment with a good 4x4 alignment guy here in town and see what if any thing is amiss.Maybe add a little caster if possible.

Thanks for you reply I will post if any thing turns up
Dave

[DmaxMaverick]

If you've changed tire size from OEM and the Z height is correct, the suspension has been compensated. It needs an alignment. As far as IFS being "sloppy", I dunno. A lot less sloppy than most SFA's, in my experience. This is assuming no worn out parts. Road crown can have a significant effect on how it handles, and the crowns are different depending on the road maintenance departments. Our crowns are substantially more profound and less consistent in rural areas compared to the interstate.

[crashz]

A good alignment will get it back for you. I have a re-occuring alignment problem with my 04, and I need to have it aligned at least every 6 months or so with these awful road here.

Hard right turns (on ramps, off ramps and my steep driveway) seem to add negative camber to my drivers side tire and neutral camber to the passenger side. Its very slight, but make my truck wander like crazy. Once this is back inline the truck is good. I should mention I have jumped from a 265 (stock) to 285 tire and the Z height is adjusted to provide clearance and support for my snowplow.

[DaveNY]

Well I guess that returns me to my origional question as to the Z height. The Z height is actually a constant in that if all angles are right the Z height is correct so a larger tire should not affect the Z measurement nor the caster as to all tires raised the vehicle equally on all corners. Under this assumption I did the height measurement as follows. I measured the hight of the center of the bolt to the ground. Imeasured the bottom of A arm to the ground. Subtracted A arm Height from Bolt Height and the remainder would be the Z Height measurement? Kind of cheating but I believe the results are the same as The factory procedure, unless I'm missing something?