Alignment Specs for Lowered & Larger size tires

[ar0ck]

On my new Wheel & Tire combo I am running 275/35/18 in the front & a 295/35/18 in the rear. Getting the tires mounted & balanced right isn't a problem but the car is also lowered about 1.5". How do I go about getting the car aligned close to whatever stock specs are? I bought some pretty good tires that I hope I could get some good miles out of and I don't want to see them disintegrate.

I have read and looked into it a little bit, and what I think happens is that a tire place could work the stock specs into some math formula to adjust to whatever it is I have done. Does anyone know of any specialty places to do this kind of stuff? I have a few suspension pieces done as well but they aren't adjustable.

I need help! I want this done right! Last time I had this done with my 17x9.5 & 17x11's the mechanic said he couldn't do an alignment on the wheels because the rears were so wide, and over the years I learned that its BS, and it is possible because there are factory cars out there with staggered width sizes.

[NJSPEEDER]

the recomended specs for caster, camber, and toe do not need to be changed for your new ride height. they can just hook up the laser alignment system and adjust everything until it is where it belongs.

[Ian]

if you can find out what the specs are supposed to be you can take it to a shop and have them set it at whatever it is you want it to be. and make sure to ask for a printout of the before and after measurements.

[SupermanX24]

Actually it's almost impossible to get the car aligned correctly with the tires not being factory spec. The best they can do is come "close."

[BonzoHansen]

Originally Posted by SupermanX24

Actually it's almost impossible to get the car aligned correctly with the tires not being factory spec. The best they can do is come "close."

Please expand on that.

[ins0mnia24]

If you need the factory alignment spec's let me know because I have the Gm factory manuals.
Any good shop that does alignments should also have a Gm book that displays the correct alignment spec's along with the +/- factory Tolerance's for each model vehicle.
The spec's in that book are no different than the book the dealers get
A friend of my family owns a shop and did my alignment about 15 months ago you would be suprised in the difference it makes depending on what the factory set your spec's at.
It would also depend on where you take it and if they decide to spend time with it to get it perfect or not
Or if it can even be done to the correct spec's.

[SupermanX24]

Originally Posted by BonzoHansen

Please expand on that.

The alignment machine computers only have factory specs. Therefore when you go to adjust caster, camber, or toe, you'd be adjusting them wrong. Therefore they pretty much have to estimate with the aftermarket features on the vehicle. It CAN be aligned, but it's not gonna be perfect.

[Ian]

Originally Posted by SupermanX24

The alignment machine computers only have factory specs. Therefore when you go to adjust caster, camber, or toe, you'd be adjusting them wrong. Therefore they pretty much have to estimate with the aftermarket features on the vehicle. It CAN be aligned, but it's not gonna be perfect.

I dont understand how different rims would affect the alignment if the sensors are mounted to the rims. the sensors get calibrated to the rim before the alignment starts.

[BonzoHansen]

I still need this explained to me. Wheels & tires don't make a car unalignable to factory specs. Camber is camber, toe is toe, caster is caster.

My alignment machines know the factory settings (no ned for manuals) and tell me when I hit them. Plus the actual measurements, so I know if I want to change them, I can use my own targets. I often did.

[Injuneer]

Running 275/40-17's in front and 315/35-17's in the back, front end dropped 1.8", back end down 1.0". They (STS on Rt 18 E. Brunswick) had no problem aligning the front end to my specs. Most other shops wouldn't even touch a lowered car. I had it aligned to a set of specs a buddy of mine recommended based on road racing experience:

Caster: +4.0*
Camber: -1.0*
Toe: 0.1

Car handled well, and had no unusual tire wear.

There's also factory and "lowered" specs in the 4th Gen FAQ:

http://www.f-body.org/faq/4/4_5.htm#ch4_5c

[BonzoHansen]

Is that all the caster they could get out of it, or is that factory spec?

Edit: just caught the road race comment. Makes sense for that perspective. I'd want more caster on the street, and less toe, but for road race/auto x, makes lots of sense.

[SupermanX24]

Originally Posted by BonzoHansen

I still need this explained to me. Wheels & tires don't make a car unalignable to factory specs. Camber is camber, toe is toe, caster is caster.

My alignment machines know the factory settings (no ned for manuals) and tell me when I hit them. Plus the actual measurements, so I know if I want to change them, I can use my own targets. I often did.

How do you hit factory settings if you don't have the original curb height and/or rims on the vehicle?

[Ian]

an alignment only measures the angle of the outter face of the rim. ride height and rim size dont matter. and caster is measured because the sensor is locked at a 90* angle from the ground. caster sweeps are unaffected by ride height and tire size as well.

*edit*

and now that I think about it, the only thing tire size affects is scrub radius and bump steer ( I think ). lowering the car does change the steering angles, but when you're doing an alignment, most of the time the car is out of spec anyway, so that wouldnt matter.

[SupermanX24]

eh, i'm still a rookie at this s*** so I tried to put up an argument and see what I learn. lol

[BonzoHansen]

Originally Posted by SupermanX24

eh, i'm still a rookie at this s*** so I tried to put up an argument and see what I learn. lol

Then ask questions, don't make statements.