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Wheel alignment settings

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exdos
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Re: Wheel alignment settings

Post by exdos » Tue Jan 14, 2014 7:22 pm

Viren wrote:So here's what I'm thinking:

Front camber: 1.0
Front toe: close to zero or slight toe in (0.04)

Rear camber: 1.4
Rear toe: 0.06 toe in

Given the car is used daily, mostly road use, couple track days a year seems an okay compromise. Any thoughts?
Provided that the pins are still in your front top mounts, I'd leave them at that, which is around -1.2 degs camber. I'd reduce the rear camber to nearer to -1 deg.

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Re: Wheel alignment settings

Post by Viren » Tue Jan 14, 2014 11:41 pm

exdos wrote:
Viren wrote:So here's what I'm thinking:

Front camber: 1.0
Front toe: close to zero or slight toe in (0.04)

Rear camber: 1.4
Rear toe: 0.06 toe in

Given the car is used daily, mostly road use, couple track days a year seems an okay compromise. Any thoughts?
Provided that the pins are still in your front top mounts, I'd leave them at that, which is around -1.2 degs camber. I'd reduce the rear camber to nearer to -1 deg.
Thanks for your help exdos, once done will let you know how it feels. One question, why would BMW dial in to much negative as standard? I would have thought by reducing rear camber the tyre contact patch on high speed bends would reduce therefore cause the back to slide and outer edge tyre wear (maybe my lack of technical knowledge! 8) ), cheers
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Re: Wheel alignment settings

Post by exdos » Wed Jan 15, 2014 12:25 am

Viren wrote: Thanks for your help exdos, once done will let you know how it feels. One question, why would BMW dial in to much negative as standard? I would have thought by reducing rear camber the tyre contact patch on high speed bends would reduce therefore cause the back to slide and outer edge tyre wear (maybe my lack of technical knowledge! 8) ), cheers
Manufacturers use negative camber and toe-in on the rear axle to resist any tendency to oversteer, even in FWD cars. Take a look at the Smart car and many other small low powered cars: many of them have such a configuration.

During high speed corners the rear camber angle (in relation to the road surface) does reduce, and if the static camber angle is correct for the amount of bodyroll (i.e. static camber of say -1.6degs and 1.6 degrees of bodyroll) then the contact patch will be across the full width of the tyre when the bodyroll produces a vertical attitude of the tyre, and this will wear the tyre evenly. Having said this, when the car corners, the outside suspension gets an increase in load, which compresses the outer suspension, which in turn increases relative static camber, say to -2.2degs. Therefore, if bodyroll is 1.6 degrees, this means that with that much bodyroll, there is still -0.6degs of camber on the outer rear wheel in my example, so the contact patch is still not evenly across the full width of the tyre at peak cornering load. I think this is the case with the Z4M rear geometry, hence I think that -1 degree of camber works better.

At the front, the negative camber on the outer wheel increases during turning of the wheel due to the effect of caster (watch any modern Mercedes doing a parking manoeuvre for a demonstration of caster/camber change with steering input).

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Re: Wheel alignment settings

Post by Vanne » Fri Jan 17, 2014 7:51 am

okay, i am understanding the camber, but why would you want to toe in? (or out for that matter) zero toe will be the best for the tire right? i wanna get this right as i need to get 2 new rears anyways and want to do that after ive done about 500 miles on the new setup so its betted in a bit. might as well hit 2 fly's with one rock.

so rear camber about -1.2 around zero toe in/out and what about the front camber?

Viren, why did you go for 0.06 toe in at the rear?

(hmmm, i should stop hi-jacking this tread)
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Re: Wheel alignment settings

Post by exdos » Fri Jan 17, 2014 10:33 am

Vanne wrote:okay, i am understanding the camber, but why would you want to toe in? (or out for that matter) zero toe will be the best for the tire right?
In the dynamic situation, when the suspension is either compressed or decompressed through its range, the camber angles will change and since toe angle is related to camber angle with MacPherson strut front suspension (Z4M), the toe angles change with camber change. Setting static geometry is therefore based upon establishing a compromise of finding the correct range of toe angles for the range of camber angles (and vice versa) in the dynamic situation through the range of suspension movement.

Personally, I find that the toe angles have the greatest influence on the handling of a car, where toe-in creates understeer and toe-out creates oversteer. Since understeer is considered to be a much safer characteristic for most drivers, manufacturers invariably use OEM geometry settings, which tend towards the safer handling of their cars (but not the case with the BMW Z3MC)
Vanne wrote:so rear camber about -1.2 around zero toe in/out and what about the front camber?
I'd stick with the -ve camber that the OEM top mounts give with the pins located, which will increase the -ve camber somewhat with lowering, but then correct the front toe, to give zero toe. :thumbsup:

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Re: Wheel alignment settings

Post by Viren » Sat Jan 18, 2014 11:35 am

Vanne wrote:Viren, why did you go for 0.06 toe in at the rear?
I wanted to keep a little toe in for stability as it's used everyday. As exdos said I would change front camber to 1.2 and rear to 1 though. Once I get my eagle f1s for the front I will get the alignment done.
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Re: Wheel alignment settings

Post by Viren » Tue Jan 21, 2014 7:10 pm

exdos wrote:
Viren wrote:So here's what I'm thinking:

Front camber: 1.0
Front toe: close to zero or slight toe in (0.04)

Rear camber: 1.4
Rear toe: 0.06 toe in

Given the car is used daily, mostly road use, couple track days a year seems an okay compromise. Any thoughts?
Provided that the pins are still in your front top mounts, I'd leave them at that, which is around -1.2 degs camber. I'd reduce the rear camber to nearer to -1 deg.
Did the garage that did your alignment use weights in the car for custom settings? Thx
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Re: Wheel alignment settings

Post by exdos » Tue Jan 21, 2014 8:15 pm

Viren wrote:
Did the garage that did your alignment use weights in the car for custom settings? Thx
I do my own alignments. In theory you should use weights on the seats and fuel in the tank, but all that goes out of the window when you have a passenger and when your tank gets empty. Personally, I don't bother weighting because I have aftermarket suspension, RTAB limiter kit and uprated ARBs, which restrains suspension movement more than OEM in the dynamic situation, so my static geometry settings are less of a compromise than the OEM ones. In practice, I don't really notice any difference from any dynamic geometry changes which may occur from having a passenger or an empty tank, but I do notice the difference in handling caused by adjusting the static geometry, from say, toe-in to zero toe, or camber change, irrespective of the load of a passenger or fuel load.

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Re: Wheel alignment settings

Post by Viren » Wed Jan 22, 2014 4:11 pm

Thanks for all your help! I'm booked in to see wheels in motion this wkend and will give them the alignment numbers posted earlier, will let you know how it goes.
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Re: Wheel alignment settings

Post by Viren » Sat Jan 25, 2014 9:26 pm

UPDATE: Went to see WIM, what a great bunch of people,talk you through everything they do on your car, would defo recommend! I got the following settings;

Front:
Camber - 0.5
Toe in - 0.04

Rear
Camber - 1.4
Toe in - 0.12

Massive improvement, rear and front feel more connected! Only thing is even with pins removed the max camber I could get was -0.5 on the driver side.

Would camber shims help me get closer to -1 to -1.2?
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Re: Wheel alignment settings

Post by exdos » Sun Jan 26, 2014 2:08 pm

Viren wrote: Massive improvement, rear and front feel more connected! Only thing is even with pins removed the max camber I could get was -0.5 on the driver side.

Would camber shims help me get closer to -1 to -1.2?
I wouldn't worry too much about the camber because, in reality, you need zero camber when travelling in a straight line, and negative camber will naturally increase in the dynamic situation on the outer wheel as soon as you turn the steering because of the caster angle. To see this for yourself, turn the steering and measure the angle when the car is stationary. Because you've reduced the front toe angle, the car will now turn more readily than it would with the OEM toe angles, so the negative camber will develop earlier in a turn with reduced bodyroll. As you've said, you've obtained a massive improvement. :thumbsup:

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Re: Wheel alignment settings

Post by Viren » Sun Jan 26, 2014 3:03 pm

exdos wrote:
Viren wrote: Massive improvement, rear and front feel more connected! Only thing is even with pins removed the max camber I could get was -0.5 on the driver side.

Would camber shims help me get closer to -1 to -1.2?
I wouldn't worry too much about the camber because, in reality, you need zero camber when travelling in a straight line, and negative camber will naturally increase in the dynamic situation on the outer wheel as soon as you turn the steering because of the caster angle. To see this for yourself, turn the steering and measure the angle when the car is stationary. Because you've reduced the front toe angle, the car will now turn more readily than it would with the OEM toe angles, so the negative camber will develop earlier in a turn with reduced bodyroll. As you've said, you've obtained a massive improvement. :thumbsup:
Fair point, I will probably look to shim in the future to about 1.1-1.2 negative camber upfront, before I track the car. Thanks for your help exdos! :thumbsup:
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Re: Wheel alignment settings

Post by Vanne » Sat Mar 21, 2015 3:33 pm

Exdos, and Viren..
Sorry to dig up this thread, but I need some help..
After my last CSL wheel swap, the company that mounted the tires insisted on doing a wheel alignment.. anyways, the car drove like a skitchy rat after that// they changed a lot of stuff and remember watching them and shaking my head.. anyways, as per normal, they didn't listen to a word I said and were stuffing around for a long , long time with my rear toe in... anyways..

sold those wheels, now running on 19 inch CSL wheels, slightly lighter than our stock wheels, but I guess a larger final drive ratio..

I am going back to my old, old wheel shop in the next few days. and was wondering with the 19 inch wheels, will my setup stettings still be what I am after, or will the 19's change everything.

going back to what I had before..

Camber

front -1.5 rear -1.2

Toe

front 0-ish and rear 0.26 toe in

(ive since pulled the pins on the front and have been running at -1.7,)

what do you think Exdos?

cheers
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Re: Wheel alignment settings

Post by exdos » Sat Mar 21, 2015 10:59 pm

Vanne,

Increasing wheel size should have no effect on the geometry, so go back to the geometry that you'd been happy with before it was recently changed.

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Re: Wheel alignment settings

Post by Vanne » Sun Mar 22, 2015 3:16 am

Thanks mate, if your ever in Dxb, you need to let me buy you a beer (or twenty) :-)
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