Moar camber! Tire camber is the leaning of the tire, and some people take this way, way too far.
Camber (specifically negative camber, with the wheels tilted inwards) is generally a good thing. However, the “look-at-me!” crowd has taken it way too far. I liken it to fake breasts. You take a good thing, and exaggerate it until it’s entirely too much and no longer functional.
Negative camber keeps the tires flat against the road as the car turns. Camber should be set according to how you drive. Commuter cars that don’t get driven aggressively are better off with almost no camber. Cars that see aggressive cornering can benefit greatly with up to 3 or 4 degrees of negative camber. Too little camber with aggressive cornering produces uneven wear on the front tires. Compare the inside (right side) of one of my front tires to the outside (left side):
…this is due to the car riding exclusively on the outer edge of the tire tread during hard cornering. This gives you less grip, but much more importantly to a cheap bastard like myself, it wears tires out prematurely. This must be fixed.
Some suspension designs (Subaru’s in particular) are really bad at negative camber. In fact, due to the shabby Macpherson strut suspension in my car, the front outside wheel actually gains positive camber while cornering. There are a few ways to fix this, but added caster is the most effective way.
For the geekier among you, you can read this discussion for some insight on why this is. The consensus is that a combination of caster adjustment and tilting the wheel at the steering knuckle is key to getting the flattest tire contact while cornering in a Subaru. I don’t have the spare cash to add caster just yet, so I’ll start with a knuckle-based camber adjustment.
This is generally done with special bolts, aka camber bolts or crash bolts. They look like this:
They work by having an offset lobe that can force the knuckle to tilt in or out. There are two downsides to these: 1) they are necessarily smaller than the bolt they replace, which is less strong, and 2) they cost about $60!
A DIY alternative is to slot the hole the normal bolt goes through so the knuckle can be tilted backwards. Some cars are actually designed to adjust camber like this, but it can be relatively easily added to cars that didn’t come that way.
First of all, the front struts need to come out. They actually come out pretty easily from Imprezas, after the brake line has been freed up. Three small bolts on top free the strut from the body, and then two very big bolts free the bottom from the knuckle.
For some reason, Subaru designed the brake line to pass through the strut. You can see it here, beside the two big strut-to-knuckle bolts.
If you want to drain your brake lines and bleed them later, you can just unbolt the brake line and let the fluid drip out. But who the heck wants to do that if they don’t have to? The answer lies in carefully cutting the brake line free from the strut. Once the little clip is off, very, very carefully cut the strut bracket where the brake line lives. If you hit the brake line accidentally you will definitely regret it. I used a small air grinder with a cutting disc, but a hacksaw or dremel would work too.
I like to stop the cut just short of the end and then wiggle the piece of metal out.
One more thing needs to happen before that strut can fall out. To get the maximum clearance from the knuckle, we need to disconnect the front sway bar. This allows the knuckle to drop a little bit further - just enough to get the strut out. The bar is easily disconnected with one bolt:
Okay, the top of the strut is unbolted, the bottom is unbolted, the brake line has been disconnected, and the sway bar has been disconnected. The strut might be a bit stubborn at the knuckle, but with some coaxing it should come free.
Now we can get to the actual slotting. We want to slot the bottom hole outwards to tilt the top of the knuckle towards the car. You could get the same result by slotting the top hole inwards, but the top hole is special in that it houses the Subaru camber bolt (which itself can be adjusted for about 0.5degrees of camber) and would be much more difficult to slot.
You shouldn’t need much slotting - each millimeter of slot should theoretically add about 1 degree of camber. I aimed for 3 degrees and enlarged the hole by 3mm, but somehow I only ended up with about 1.5 degrees. 3mm of grinding to do!
It was some pretty difficult grinding. It is too tight to get any serious tools into the hole, so I used a power drill and some grinding stones.
Eventually I switched to a rotary file in the drill which worked a bit better. It’s worth the expense for a set of rotary files if you’re going to do this.
I checked progress with a bolt in the hole and verified the distance with my calipers.
With an extra 3mm on all four holes, it’s time to reinstall the struts. They go in just as they came out, but don’t tighten the lower strut-to-knuckle bolts just yet. To get maximum camber, I used used a floor jack and a chunk of scrap wood to put pressure on the brake disc top hat, ensuring that the bolt was pushed all the way to the edge of that new slot. Then the top Subaru camber bolt was adjusted to its maximum position, giving MAX CAMBER!
Those two bolts can now be tightened up to 129 ft/lbs. I went one (optional) step further and welded some washers to the strut in order to hold the lower bolt in its maximum position. This keeps me from having to mess with the floor jack and scrap wood every time I make an adjustment.
The washer needed a little trimming to get it to fit. Note that there’s no additional strength here - that’s just a tack weld to keep the bolt from moving before it has been tightened.
Ensure:
If you measure the distance between a plumb line and the top of the wheel versus the bottom of the wheel, a little trigonometry should give you the tilt of your wheel. My garage floor is nowhere near level enough to do this, but by checking the car nose-in and then back-in at the same point on the floor, I got a rough measurement of about 1.5 degrees negative camber on each side. I’ll have to level the floor eventually and get a real measurement.
You might end up with different values on each side. As long as you were reasonably accurate in your grinding, it shouldn’t vary by much. This can be equalized by adjusting the Subaru camber bolt for about +/-0.5 degrees. Ultimately, it won’t make too much difference if they are a bit unequal. You may get a very slight pull to one side when you brake, but that’s about the worst of it.
You WILL need to adjust your front wheel toe alignment after this modification. Adding more camber will cause the wheels to toe out quite a bit, which WILL chew up your tires quickly. Stay tuned to find out how to adjust your front toe setting.
continue to DIY alignment goodness!
Cost:
free!
Incidental supplies:
grinding stones
sweat
Camber (specifically negative camber, with the wheels tilted inwards) is generally a good thing. However, the “look-at-me!” crowd has taken it way too far. I liken it to fake breasts. You take a good thing, and exaggerate it until it’s entirely too much and no longer functional.
Negative camber keeps the tires flat against the road as the car turns. Camber should be set according to how you drive. Commuter cars that don’t get driven aggressively are better off with almost no camber. Cars that see aggressive cornering can benefit greatly with up to 3 or 4 degrees of negative camber. Too little camber with aggressive cornering produces uneven wear on the front tires. Compare the inside (right side) of one of my front tires to the outside (left side):
…this is due to the car riding exclusively on the outer edge of the tire tread during hard cornering. This gives you less grip, but much more importantly to a cheap bastard like myself, it wears tires out prematurely. This must be fixed.
Some suspension designs (Subaru’s in particular) are really bad at negative camber. In fact, due to the shabby Macpherson strut suspension in my car, the front outside wheel actually gains positive camber while cornering. There are a few ways to fix this, but added caster is the most effective way.
For the geekier among you, you can read this discussion for some insight on why this is. The consensus is that a combination of caster adjustment and tilting the wheel at the steering knuckle is key to getting the flattest tire contact while cornering in a Subaru. I don’t have the spare cash to add caster just yet, so I’ll start with a knuckle-based camber adjustment.
This is generally done with special bolts, aka camber bolts or crash bolts. They look like this:
They work by having an offset lobe that can force the knuckle to tilt in or out. There are two downsides to these: 1) they are necessarily smaller than the bolt they replace, which is less strong, and 2) they cost about $60!
A DIY alternative is to slot the hole the normal bolt goes through so the knuckle can be tilted backwards. Some cars are actually designed to adjust camber like this, but it can be relatively easily added to cars that didn’t come that way.
First of all, the front struts need to come out. They actually come out pretty easily from Imprezas, after the brake line has been freed up. Three small bolts on top free the strut from the body, and then two very big bolts free the bottom from the knuckle.
For some reason, Subaru designed the brake line to pass through the strut. You can see it here, beside the two big strut-to-knuckle bolts.
If you want to drain your brake lines and bleed them later, you can just unbolt the brake line and let the fluid drip out. But who the heck wants to do that if they don’t have to? The answer lies in carefully cutting the brake line free from the strut. Once the little clip is off, very, very carefully cut the strut bracket where the brake line lives. If you hit the brake line accidentally you will definitely regret it. I used a small air grinder with a cutting disc, but a hacksaw or dremel would work too.
I like to stop the cut just short of the end and then wiggle the piece of metal out.
One more thing needs to happen before that strut can fall out. To get the maximum clearance from the knuckle, we need to disconnect the front sway bar. This allows the knuckle to drop a little bit further - just enough to get the strut out. The bar is easily disconnected with one bolt:
Okay, the top of the strut is unbolted, the bottom is unbolted, the brake line has been disconnected, and the sway bar has been disconnected. The strut might be a bit stubborn at the knuckle, but with some coaxing it should come free.
Now we can get to the actual slotting. We want to slot the bottom hole outwards to tilt the top of the knuckle towards the car. You could get the same result by slotting the top hole inwards, but the top hole is special in that it houses the Subaru camber bolt (which itself can be adjusted for about 0.5degrees of camber) and would be much more difficult to slot.
You shouldn’t need much slotting - each millimeter of slot should theoretically add about 1 degree of camber. I aimed for 3 degrees and enlarged the hole by 3mm, but somehow I only ended up with about 1.5 degrees. 3mm of grinding to do!
It was some pretty difficult grinding. It is too tight to get any serious tools into the hole, so I used a power drill and some grinding stones.
Eventually I switched to a rotary file in the drill which worked a bit better. It’s worth the expense for a set of rotary files if you’re going to do this.
I checked progress with a bolt in the hole and verified the distance with my calipers.
With an extra 3mm on all four holes, it’s time to reinstall the struts. They go in just as they came out, but don’t tighten the lower strut-to-knuckle bolts just yet. To get maximum camber, I used used a floor jack and a chunk of scrap wood to put pressure on the brake disc top hat, ensuring that the bolt was pushed all the way to the edge of that new slot. Then the top Subaru camber bolt was adjusted to its maximum position, giving MAX CAMBER!
Those two bolts can now be tightened up to 129 ft/lbs. I went one (optional) step further and welded some washers to the strut in order to hold the lower bolt in its maximum position. This keeps me from having to mess with the floor jack and scrap wood every time I make an adjustment.
The washer needed a little trimming to get it to fit. Note that there’s no additional strength here - that’s just a tack weld to keep the bolt from moving before it has been tightened.
Ensure:
- Strut-to-knuckle bolts are tightened (129ft/lbs - aka “gorilla torque”)
- top strut nuts are tightened (19 ft/lbs)
- sway bar is reconnected (? ft/lbs - tight enough, but not too tight!)
- brake line is reattached with its clip
If you measure the distance between a plumb line and the top of the wheel versus the bottom of the wheel, a little trigonometry should give you the tilt of your wheel. My garage floor is nowhere near level enough to do this, but by checking the car nose-in and then back-in at the same point on the floor, I got a rough measurement of about 1.5 degrees negative camber on each side. I’ll have to level the floor eventually and get a real measurement.
You might end up with different values on each side. As long as you were reasonably accurate in your grinding, it shouldn’t vary by much. This can be equalized by adjusting the Subaru camber bolt for about +/-0.5 degrees. Ultimately, it won’t make too much difference if they are a bit unequal. You may get a very slight pull to one side when you brake, but that’s about the worst of it.
You WILL need to adjust your front wheel toe alignment after this modification. Adding more camber will cause the wheels to toe out quite a bit, which WILL chew up your tires quickly. Stay tuned to find out how to adjust your front toe setting.
continue to DIY alignment goodness!
Cost:
free!
Incidental supplies:
grinding stones
sweat
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