Question about ride heights and alignment

[sperry]

So, I swapped my snow tires onto the wagon earlier this week. Turns out that the slightly larger diameter of the snows is just enough that I rub up front entering/exiting driveways, etc. Plus, the coilovers seem to have settled a bit since I installed them, leaving the car just a touch too low in general.

So I think I'm going to have to raise the car up probably 3/4" to an inch. The question is, how much does that affect the existing alignment? The car is already maxed out on camber and caster front and rear, so really that's just going to be wherever it ends up. What I'm actually concerned about is the toe. Which direction does the toe change when raising the car? If it's a tiny bit of toe-in, I'm probably fine to raise the car and not bother to re-align it. But if it's toe-out or if the change is excessive, I'm gonna need Cory or Bob to get it back on the rack.

Theoretically, the toe shouldn't change much with ride height changes... otherwise the car would exhibit bump/roll steer. But with the shitty Subaru geometry, I wouldn't be surprised if raising the car an inch results in 2 deg of toe-out.

[Dean]

Be sneaky. Put a 4' level or straight edge on it and drop a plumb line and then put a jack under the front jack point and jack it up 3/4" and put the straight edge/plumb line on again. Both sides to make sure. Measure and do some math/geometry if needed.

You can do the multiple layers of trash bag trick if you want more accuracy.

[100_Percent_Juice]

What are you rubbing on?

[sperry]

Originally Posted by 100_Percent_Juice

What are you rubbing on?

The plastic fender liners. I'm nowhere near the fender lip or the struts or anything... I'm just too low for the oversized diameter of my 235/55/17 snow tires.

[sperry]

Originally Posted by Dean

Be sneaky. Put a 4' level or straight edge on it and drop a plumb line and then put a jack under the front jack point and jack it up 3/4" and put the straight edge/plumb line on again. Both sides to make sure. Measure and do some math/geometry if needed.

You can do the multiple layers of trash bag trick if you want more accuracy.

I'd have to raise both sides of the car evenly for that to work, otherwise the swaybar and roll-steer will skew the result.

Besides, I'm already not looking forward to the simple process of taking all the wheels off and raising the car, nevermind going all home-alignment on the thing. I'd rather KSpeed do the work while I pester Bob and Cory and eat Tacos.

[100_Percent_Juice]

What if you got a set of really skinny spacers that you would only run with your winter wheels?

[AtomicLabMonkey]

Hard to say how much it will change unless you have a working kinematics model of the suspension & steering laid out in CAD. Just raise it up and then go eat tacos.

[AtomicLabMonkey]

Oh, and unless you have adjusted the rack or tie rod pivot locations it does have bump/roll understeer built into it, so the toe does change with bump/rebound. Every production car does as far as I know. It's just a question of how much. Normally it's set up so that as a front wheel moves up in bump, it also toes out. This is understeer behavior. It might or might not toe in, in rebound. Depends on what the curve looks like. Rear axle would be the opposite, you want it to toe in, in bump.

[sperry]

Originally Posted by 100_Percent_Juice

What if you got a set of really skinny spacers that you would only run with your winter wheels?

Um, then it would rub on the fender liner *and* the fender?

Like I said, my problem isn't with the fender... it's just that my car is too low. The tire is literally tucked up into the wheel well so far it's hitting the plastic splash guard fender liner thing if I hit a bump while turning.

[sperry]

Originally Posted by AtomicLabMonkey

Oh, and unless you have adjusted the rack or tie rod pivot locations it does have bump/roll understeer built into it, so the toe does change with bump/rebound. Every production car does as far as I know. It's just a question of how much. Normally it's set up so that as a front wheel moves up in bump, it also toes out. This is understeer behavior. It might or might not toe in, in rebound. Depends on what the curve looks like. Rear axle would be the opposite, you want it to toe in, in bump.

That makes sense. I was really hoping that someone would have recently messed with ride heights on a Legacy and just knew how much toe they had to adjust afterwards.

[100_Percent_Juice]

I assumed that it was hitting on the inside of the tire when you turned in. Just drive really fast in a circle and the problem will fix itself.

[A1337STI]

I've done a few last minute ride height adjustments (impreza GC)

raising the car, i think tows it out .. i have tow plates (for measuring) you could borrow... I need to hunt them down first though. wow those are big tires. i have 215/55/17s on my STI for snows, and they also run the fender liner slightly (during hard turning) you have 235/55/17s? wow ...

I think you'll get at least a 1/16th adjustment if you raise up your car almost an inch. (toe out) but I'm not exactly sure ... I've gotten so many alignments on my rally car , and i recently started throwing out a lot of the old spec print outs...

[Kevin M]

Originally Posted by A1337STI

wow those are big tires. i have 215/55/17s on my STI for snows, and they also run the fender liner slightly (during hard turning) you have 235/55/17s? wow ...

The Outback has tires 1" taller than Imprezas. Those are a little taller than stock, but not a huge amount. I run 225/55R17s on the Forester (same OE sizing as the Outback) because they're just a touch taller than stock, but in that size you have fewer options.

[sperry]

I run 245/45/18s in the summer. Those are monster truck tires!

[A1337STI]

Oh that's right. Tom was showing me how subaru raised the Outback. sub frame spacers (mostly) I think there was a few other things they did. I think the rear subframe is slightly different. but that keeps the same geometry (instead of angling down the A-arms extra .. like what happens on my car if i raise it up to outback height)

245/45/18s ? damn ... you must have some good ground clearance.

[sperry]

Originally Posted by A1337STI

Oh that's right. Tom was showing me how subaru raised the Outback. sub frame spacers (mostly) I think there was a few other things they did. I think the rear subframe is slightly different. but that keeps the same geometry (instead of angling down the A-arms extra .. like what happens on my car if i raise it up to outback height)

245/45/18s ? damn ... you must have some good ground clearance.

The body spacers are good for about 1 inch IIRC. The other 3.8 inches of added clearance over the Legacy (or whatever it is) comes from longer struts/springs.

On the 245's (before I raised the car up an extra inch) the front bumper just cleared a normal height curb when parking.



The snow tires are actually taller than the 18's, plus I just raised the car about 3/4", so it's probably got around the same clearance as a stock legacy (while still looking lowered ), which is nowhere near the clearance of a stock outback. Those things are monster trucks.