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ZOO
ZOO SuperDork
5/15/13 2:40 p.m.

Hello All,

I need some guidance around a "do most things" alignment for my E46 M3. It is running a TC Kline coilover set up, and has been corner-weighted so I won't be adjusting the ride height.

Everything else is stock, but I am also running a square tire and wheel set up (245/40/18 Rivals on 9 inch wide rims).

I use the car in autox, in an ST class, and for HPDE events. I also drive the car regularly -- so I'd like to minimize tire wear -- I recognize this is a compromise -- I'd like to wear out the tires before ruining the tires, especially the inside edges on the fronts. I am realistic, though -- I don't expect to get more than a season (from now to late October) from them given the events I plan.

Any recommendations?

Can anyone give me a refresher on what characteristics influence what aspects of the car's handling? For example, what does increasing toe, caster, or camber do? Decreasing?

I tend to like my car a little loose, with good turn in.

Rob

wbjones
wbjones PowerDork
5/15/13 4:29 p.m.

if you're worried about the inside edges of the front tires, stay away from any toe out .... at worst adjust to the outer edge of the green on the alignment machine .. neg. camber itself usually won't cause any excessive tire wear

toe out, both front and rear will help with turn in (too much of course, as with pretty much anything, will not be you're friend)

neg. camber helps the loaded tire lay flat in a corner ... look at a NASCAR car, the rt front has LOTS of neg camber, so that the tire will be flat in left hand turns, the left front has LOTS of pos. camber so that tire will be flat in those left hand corners

as to caster, I sorta, think, maybe I might understand it's purpose ... but as wishy-washy as I'm being about it, I probably shouldn't try to explain it to anyone else

kevlarcorolla
kevlarcorolla Reader
5/15/13 7:20 p.m.

Within reason castor can be useful for adding camber to the outside and pos camber to the inside wheel while the wheels are turned.Also changes the load the tire sees due to the eliptical arc the spindle takes while turning by increase inside tire weight and reducing outside tire weight. Basically it can help help improve front grip without needing camber/toe settings quite so agressive.

ZOO
ZOO SuperDork
5/15/13 8:28 p.m.
kevlarcorolla wrote: Within reason castor can be useful for adding camber to the outside and pos camber to the inside wheel while the wheels are turned.Also changes the load the tire sees due to the eliptical arc the spindle takes while turning by increase inside tire weight and reducing outside tire weight. Basically it can help help improve front grip without needing camber/toe settings quite so agressive.

That's helpful -- any recommendation for an amount to aim for? Should it be maxed out? Or at one extreme of the factory recommended settings?

Rob

ZOO
ZOO SuperDork
5/15/13 8:33 p.m.

These are the factory specs:

Front:

Camber: -1.3 to -0.7 degrees Caster: +6.9 to 7.9 degrees Toe in: 0.08 to 0.19 degrees

Rear:

Camber: -2.0 to -1.5 degrees Toe in: 0.13 to 0.23 degrees

My friend recommends 3.0 degrees negative camber in front, and keep everything else as posted. Seems like I should minimize toe in and maximize caster? Or is the smaller number for caster more ideal?

I have adjustable camber plates so I can likely reach that spec.

Rob

Jaxmadine
Jaxmadine New Reader
5/15/13 8:36 p.m.

Usually anything over -1.5 camber will cause inside wear. But if you get tyres that don't. Last long anyway, say 10k miles. Then 2.0 neg should be fine, wear will be at about 2-3mm when the shoulder wears out.
I've seen up to .25 toe in and out on factory settings that don't hurt wear on stickier tyres as well. Maybe get a lifetime or 5 year plan at your local shop and just change it all the time?

Dusterbd13
Dusterbd13 HalfDork
5/15/13 8:44 p.m.

and for my own alignment tomorrow, positive camber is achived by tilting the top of the spindle towards the rear of the car, correct?

Hal
Hal Dork
5/15/13 9:06 p.m.
Dusterbd13 wrote: and for my own alignment tomorrow, positive camber is achived by tilting the top of the spindle towards the rear of the car, correct?

No. Front to rear changes the caster. In and Out is camber. In = negative camber and Out for positive camber

Dusterbd13
Dusterbd13 HalfDork
5/15/13 9:08 p.m.

E36 M3. meant to type caster. im tired. which is why im not aligning my truck tonight....

motomoron
motomoron Dork
5/15/13 10:08 p.m.

I've got an e36 M3 w/ AST4100 coilovers, 550#F, 625#R, 28mm H+R bar F, 20mm UUC bar rear. Lots of bracing, roll bar. It's competitive in NASA TTC but needs aero.

I arrived at:

  • F: 3.2 degrees neg camber, zero toe, all the caster you can get w/ Vorshlag plates.

  • R: 2 degrees neg camber, 1/16" toe in both sides.

At Summit/VIR/NJMP I run the ASTs at full hard or 1 click off F, 2-3 clicks off R.

Over the years I've found that it's toe, not camber that grinds tires to dust. And if you do much hard track time, insufficient camber will result in...ground up tires.

Also - get a pyrometer. I got the harbor Freight one when it was on sale for $29.95. I know you're supposed to have a real Longacre probe type - but I'm not looking for total accuracy of actual temp - but temp difference across the tire, and for 30 clams it works fine.

Have someone take temps as soon as you enter the hot pit off track. Get the outside, 1/4 in, middle, 3/4, inside. When the camber is correct, the temp is uniform. Period.

crazycanadian
crazycanadian Reader
5/16/13 1:43 a.m.
motomoron wrote: I've got an e36 M3 w/ AST4100 coilovers, 550#F, 625#R, 28mm H+R bar F, 20mm UUC bar rear. Lots of bracing, roll bar. It's competitive in NASA TTC but needs aero. I arrived at: - F: 3.2 degrees neg camber, zero toe, all the caster you can get w/ Vorshlag plates. - R: 2 degrees neg camber, 1/16" toe in both sides. At Summit/VIR/NJMP I run the ASTs at full hard or 1 click off F, 2-3 clicks off R. Over the years I've found that it's toe, not camber that grinds tires to dust. And if you do much hard track time, insufficient camber will result in...ground up tires. Also - get a pyrometer. I got the harbor Freight one when it was on sale for $29.95. I know you're supposed to have a real Longacre probe type - but I'm not looking for total accuracy of actual temp - but temp difference across the tire, and for 30 clams it works fine. Have someone take temps as soon as you enter the hot pit off track. Get the outside, 1/4 in, middle, 3/4, inside. When the camber is correct, the temp is uniform. Period.

Thats some good info there... I don't know BMW's specifically and what they like.. Every car is a little different and you'll have to play with the temp gun, and your alignment settings to find that sweet spot.. Every car is a little different..

My mazda really likes having - 3.24 deg camber up front when I am running my V710's in the dry. But in the wet it really kills my straight line braking and accelerating. This just goes to show there is always compromises when setting up a car..

Caster is always a good thing to a point.. I wish I could get almost 8 deg caster. I would start with the most I could get and try it.. You don't have to worry about this angle wearing your tires while daily driving the car..

GameboyRMH
GameboyRMH UltimaDork
5/16/13 9:23 a.m.

Yep toe-out makes a much bigger difference in tire wear than camber. Still, 3deg is pretty aggressive for a "do most things" setup.

Here's what I'd recommend as a starting point: All factory rear settings, zero toe front, max factory recommended front caster, -2.5 front camber. If you want it to rotate more you could try zero toe rear.

I'm not saying the -3deg is a bad setting, but static camber is the worst way to get camber, the extra caster will give you more beneficial camber changes in corners.

ZOO
ZOO SuperDork
5/16/13 9:47 a.m.

Thanks for the recommendations so far.

Can there be too much caster? Should I ask to maximize it even if it goes out of spec? It looks like caster is a "something for nothing" trade . . .

GameboyRMH
GameboyRMH UltimaDork
5/16/13 10:05 a.m.
ZOO wrote: Can there be too much caster? Should I ask to maximize it even if it goes out of spec? It looks like caster is a "something for nothing" trade . . .

Yes there can be too much caster (and too little) but it won't be within the factory recommended specs for sure.

It's not totally "something for nothing," steering effort will be increased slightly.

ZOO
ZOO SuperDork
5/16/13 12:28 p.m.

I think I will aim for:

Front Camber -3.0 degrees Caster +7.9 degrees (max factory spec) Toe 0.0 degrees

Rear

Camber -2.0 degrees Caster not adjustable Toe 0.0 degrees

Thoughts? Will I kill myself?

GameboyRMH
GameboyRMH UltimaDork
5/16/13 12:32 p.m.

It'll be fine, it's not a radical setup, looks like you're putting emphasis on autocross performance.

ZOO
ZOO SuperDork
5/16/13 12:39 p.m.
GameboyRMH wrote: It'll be fine, it's not a radical setup, looks like you're putting emphasis on autocross performance.

That's where most of my competitions will be. I will have four or five track days too, but they are HPDE, not racing.

bludroptop
bludroptop SuperDork
5/16/13 12:42 p.m.
ZOO wrote: I think I will aim for: Front Camber -3.0 degrees Caster +7.9 degrees (max factory spec) Toe 0.0 degrees Rear Camber -2.0 degrees Caster not adjustable Toe 0.0 degrees Thoughts? Will I kill myself?

I'd consider adding just a touch of toe-in in the rear.

My STX e36 does dual-duty pretty well with these settings;

Front Camber = -2.5 degrees Front Caster = 5.5 degrees Toe = zero

Rear Camber = -1.8 degrees Rear toe in = 1/8" (total)

It turns in well and is pretty neutural. That's with adjustable coil overs, 600#/650# springs, 28mm front bar and stock rear bar. We're going to be playing with some different bars to try dialing out some corner exit oversteer, but otherwise it is predictable and easy to drive.

iceracer
iceracer UberDork
5/17/13 5:21 p.m.

For autocross, a little toe out in the rear will help turn in. Not recommended for track or street, too squirrely.

preventing the car from leaning helps tremendously

Jaxmadine
Jaxmadine Reader
5/17/13 7:06 p.m.

actually it doesn't .... toe out will .. I run 3 1/2° neg. camber on the front of my CRX with zero inside tire wear, driving ~ 5000 mi per yr ... when I've experimented with more than max factory spec toe out, I've seen excessive inner edge tire wear .... I've talked with many others on this subject and it's been their experience also ....

You might have talked to others. Its what I do for a living. 5k a year is nothing on a car anyway. Try 15k or more, then let me know. I can't even count how many factory bmws and mercs I've had to install camber kits on because the excessive camber was killing the inside of the rear tyres. They were lucky to get 10k out of a set. Fix the camber, and then they are gettin 30k+ out of the same tyres. Same goes with my mazda. Had -3 in the rear and -2.5 in the back,zero toe, tyres got worn out on the inside edge within 10k miles. Lower it down to -2 in the back -15 front, double the miles.

Jaxmadine
Jaxmadine Reader
5/20/13 4:39 p.m.
wbjones wrote: ok... you're talking rear tires on a rwd car ... my experience is with fwd and camber on the front end ... I'll get 1 1/2 - 2 yrs out of a set of r1r's with the camber I mentioned (-3 1/2° front and -1 1/2° rear) and I run 20 - 25 a-x's a yr and 5 - 7 TT/track days a yr ... total toe on the front is -.30°, and the toe in the rear is - .03° so while 5k miles is "nothing" it's pretty hard miles ... and while I'm sorry for your customers, all the people I race with (many of whom dd their cars) have the same type of tire milage, with much (if not more) the same alignment

Dude, racing miles is not the same as street miles. Go read a few books about tyres, hell go look at what is standard in the industry. If it didn't wear, then why would nitto sell a tyre with thicker insde tread, and a harder compound on just the inside? For toe wear? You might feel sorry or my customers, but you are just flat out wrong and ignorant. As are the other people you race with.

Jaxmadine
Jaxmadine Reader
5/20/13 7:43 p.m.

Yes, they are bogus. Serious. If u wanna do a quick test, run straight on some dirty road with your slicks. any dirt on the outside edge? Its simple geometry. Go read a book.

Nathan JansenvanDoorn
Nathan JansenvanDoorn Dork
5/20/13 8:18 p.m.

:)

Jaxmadine - I have the same experience as some others on this thread. I LOVE -ve camber on every strut vehicle that I've had (almost all of them). I've never had camber related wear. In fact, when I run close to 0 camber, I wear the outside of the tires more than the inside. This is a result of how I use the vehicle - I don't like to slow down in the corners much, and I autox. As a result, -ve camber results in LESS overall wear, and much more even wear. You'll find most auto-xers and track day enthusiasts have similar results. I HAVE chewed up a set of tires in no time as a result of excessive toe.

To the OP: I suspect you'll love the effect that -ve camber has on front grip on a strut front suspension. Let us know how it works out for you.

I expect that your statistics come from a crowd that uses their car very differently, not that there is anything wrong with that.

fanfoy
fanfoy Reader
5/20/13 8:49 p.m.

Tire wear is a lot more complex then saying camber causes wear. Milliken tells us that tire wear is caused by tire scrub, which is normal since tire scrub is the equivalent of dragging an eraser on paper.

There are four types of scrub:

1) compression scrub: the track width of the car changing in bump or droop

2) steering scrub: the steering center not being equal to the tire center

3) rolling scrub: the thread pattern deforming under load or slip

4) alignment scrub: Toe-in or out.

As an end user, you have no control on the first two types of scrub. The third one you can affect with tire pressures. And the last one, you can remove with setting your toe to zero, with the side effects on stability. Camber has no effect on any of those scrubbing effects.

On a road car that sees very little suspension movement, removing negative camber spreads the scrubbing effects on a wider section of the tire.

But in performance driving, the rolling scrub becomes HUGE as you are sliding the tire. A few miles of track time can cause more wear than thousands of miles on the street.

So, for a performance application, you want negative camber because all cars (almost) don't have enough camber gain in bump designed into their suspension (for various excellent practical reasons) for performance applications. So as the car rolls, the contact patch moves to the outside of the tire. So by increasing negative camber in a performance application, you are doing the same as reducing it in a DD application.

So to answer the OP: Like people have already mentioned, the only real way to know is start with something conservative as far as camber (not to reduce too much your braking traction), increase caster to the max (and live with the increased steering effort) and set the toe to zero to reduce the scrubbing that you can reduce. And verify that it works by checking your tire temperatures.

Jaxmadine
Jaxmadine Reader
5/20/13 9:30 p.m.

fanfoy is correct!

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