xtcnrice

Sorry for the terrible thread name... but the question/concern is pretty stupid to begin with

My car is lowered, and after my alignment was done I'm still sitting at -3 degrees of camber on the rear left, and -3.5 degrees of camber on the rear right. I expected the alignment to not be able to correct the camber much since I've lowered it quite a bit without a camber kit.

So my question is, if I install a rear camber kit and restore the negative camber to say, -0.5 degrees on each side, that should theoretically push the top of the wheels outwards, and the bottom of the wheels inwards, effectively lowering the offset of my rear wheels right? How much offset does this translate to approximately?

I'm guessing no one really knows cuz it's sort of a dumb question as that's not really the point of a rear camber kit, but I'm just curious because I don't wanna waste money on spacers if I do end up getting the rear camber kit and find out I don't need the spacers anymore.

EDIT:
I know I could just get the rear camber kit, get it installed and realigned, and go from there to see if I need spacers or not. But I'm still interested in knowing the answer to the question.

dakneep

Well, dude think about it your wheel was a certain offset before you lowered it, and is still the same offset after you lowered it with added camber. Now if you use a camber kit to correct the negative camber your offset is still the same... catch my drift?

iCrap

42

xtcnrice

I understand, and you're likely correct.

However my question is more related to the effective offset difference between with and without a rear camber kit while the car is low. For example... thinking solely about flushness with the fender, if I put on a rear camber kit now and aligned it, would this be equivalent to not installing a rear camber kit and putting on the same set of wheels but with say 5mm less offset? I'm thinking solely in terms of flushness with the fender here.

Also, I lowered the car AND installed the new wheels all at once. I never got to see the wheels on without the coilovers because I thought it'd look hideous (just my opinion). Although it may have been a good idea to do this as I'd get to see how close to the fenders the wheels would've been and imagined the car lowered without the effect of negative camber.

Thanks for chiming in, appreciate the input. Just not the sorta answer I was looking for

EDIT:
For example: http://my350z.com/forum/brakes-and-s...amber-kit.html

This dude is asking the same question.. but there are conflicting answers. Post #8 is saying 1 degree in the positive direction (i.e., from -2 to -1 degree) is equivalent to 20mm of movement closer to the fender from the top outer part of the tire. I don't think this is accurate... this sounds like way too much. Like right now I have +45 offset wheels on -3 deg camber. If I correct to -2, it's like I have +25 offset wheels on -3 deg camber? I think this difference is way too much. I'm looking for an accurate answer to this number.

Post #13 disagrees with 20mm per +1 degree as well.

xtcnrice

bump... guess no one knows?

Puppetmaster

I think I know where you're going with this, and the answer is it probably varies by car. The way I think about it, my car has -3 camber and if I got a camber kit, more positive camber pushes the top of the wheel back out, closer to the fender. In a way, this is sort of like an offset effect, but only for the top part of the wheel. The position of the bottom of the wheel would not change of course. Is this what you're referring to?

xtcnrice

Yes sir. Thank you for clarifying what I mean! The bolded part is the part I forgot to explain, which was what I was referring to as "effective offset". Doh.

Puppetmaster

I understood only because I was thinking about the exact same thing the other day. Even with 8.5 wides and +30 offset, my rears rears look sunken from certain angles, because of the negative camber. My fenders are already rolled, so I probably would be fine going to more neutral camber, but I'm too lazy (and cheap) to go through all that effort. My toe is adjusted to a slight toe in set up so tire wear isn't bad for having -3 degs of camber, plus the car handles almost perfectly now, so I'm not that motivated to get a rear kit other than to fix a very subtle looks issue. Not yet.

xtcnrice

Yeah I don't know how much the camber kit would bring the top of the tire closer to the fender, but I'm thinking with yours specs you'll need at least 10-15mm worth, depending on the amount of stretch on your tires.

nzitr

I had been interested in this topic so I took a look at my car then did some calcs.

Re the effect of camber I used a trig calculator and I got 11mm change per degree (using 630mm as the tire height)

http://www.pagetutor.com/trigcalc/trig.html

Some of this will be outwards at the top and some will be inwards at the bottom, it all depends on the pivot point.

Looking at the CU2 I think the pivot point is at the bottom of the hub which is almost perfectly halfway between the hub center and the ground. This indicates to me that the effect at the top of the tire is three times that of the bottom.

Using this info I calculate that for every degree camber correction (or 11mm):

Top of the tire moves outwards 8.25mm
Hub center moves outwards 2.75mm
Bottom of the tire moves inwards 2.75mm

I expect that there will be some other factors going on like toe effect and potential setback changes but I think it would be very hard to calculate those.

I suggest you review how I calculated this info and decide if you want to use the info.

regards

xtcnrice

I'm not very interested in the whole cambergang look, and these numbers make it more attractive for me in getting a rear camber kit as I'd like my rears to be a tad more flush anyhow.

Thanks a lot for the awesome response!

Puppetmaster

No stretch going on here. 245/40/18, perfect fit.

Puppetmaster

Great information and very clever calculation. Thanks for posting that.

PS - I lived in Wellington and Auckland many years ago and have family in Auckland, nice to see a Kiwi around here!

nzitr

Thanks but think I have the pivot point wrong as I had overlooked the top ball joint. I have just taken a wheel off to get a better look at it.

There are three arms attached to the hub. Looking from the side of the car they are arranged as follows:

3pm, toe adjustment arm
6pm, setback arm.
8pm, rear arm

To complicate things the setback arm is on an angle where it will move the hub rearwards when lengthened.

The ball joint is at the top with the pivot point being about 120mm above the center of the hub. I think the hub moves around this point depending on the adjustment of the 3 arms. I think the relationship is probably too complex for a calculation as simplistic as the one I originally did. I do however think the hub center change will likely be minimal.

regards,