How much camber?

[ozracer]

I was wondering if anyone can tell me how a race car handles when it has too much or not enough negative camber. the class i race in has a maximum allowed negative camber of 4 degrees. i have got the feel for setting the castor and, to a lesser extent, the toe.
Thanks.

[shiny side up!]

The simplest way (but not necessarily the best, as we've discussed on here before) to find a good camber setup is to adjust it until your tire temps are pretty even (within 5C or 10F) across the tread (inside, outside, and center). Thus, if the outside of the tire is hotter than the inside, then you give it more negative camber, and vice versa. This approach will be really thrown off if your tire pressures are out to lunch, however.

The handling problems from missing the camber setup could manifest themselves as under or oversteer, lack of forward grip, or very touchy steering. Actually, it can cause lots of nasty things, it's difficult to make a list because nearly anything could be on it...

What kind of car are you running? What kind of speeds do you carry in corners? What kind/size of tires?weight/weight distribution/cg height? All of those things (and more) can effect the camber setup...

[ozracer]

Thanks for your help, if you have any other useful information then please keep it comming!The car is a family sized sedan. If you are familiar with V8 Supercars, our series is the same commodore falcon thing, but the models from 10 years ago, and 6's instead of V8's. The tyre size is 225x60 R16 Bridgestone Potenza RE540s. Weight distribution would be close to 60/40 but im not certain. Cg i wouldnt have a clue (maybe 600mm at a guess). Car weight is 1365 kg. I think i need to buy a tyre pyro but they are damn expensive! Think i should cornerweight my car soon too.

[shiny side up!]

Well, for a really general idea I would expect that you will run less camber at the rear than the front, and probably a fairly high level of camber due to the high weight/roll of the car. But as for real numbers, I'm not much help...

[GTV27]

Running much more than 3 deg neg in static camber can lead to problems in braking - esp if you pick a bit extra dynamic neg as the front dives under brakes - you can end up with not much contact patch left and flat spots.

Putting the car on an alignment machine (or using the appropriate gauges) and moving the suspension through its travel will tell you about dynamic camber (and caster and toe) change.

Too little neg camber will result in unplesant mid-corner understeer and scrubbed outside sidewalls/edge of tread.

Also generally the B'stone RE540's seem to have a very stiff sidewall (like the Dunlop DO1's) and thus can tend to like less negative, than say Yoko AO32's or Falken RS-VO4's (experience mostly based on 195/60 14).

[Jukebox]

Excessive toe is what causes uneven tread wear, not camber. Try this settings...Front -2 to -2.5 degrees, toe 1/16" in (+.25 deg) & Rear 0 to -0.5 degrees, toe 0.

[Amaroo Park]

I think that Caster is more important than Camber. Wehn corner you will find with the right caster angles you will get more neg camber

[MA2]

Originally posted by Jukebox
Excessive toe is what causes uneven tread wear, not camber.

No so - too much negative camber can result in loss of contact patch width with high cornering loads. Lose too much, and the grip level decreases. On the front this will manifest itself as mid-corner to exit push, with occasionally a snap oversteer as you unwind the steering. That push will rip the rubber right off the tire.

It's quite common on FF's to see this - the front tires get a big scallop right near the inside edge.

Being a radial, plan on seeing inside and middle temps within 10 degrees of each other (Farenhiet, that is!), with the outside about 15-20 colder than the inside.

Use ONLY dry nitrogen, NOT AIR, to fill the tires. Pressure rise front to rear is a good indicater of car balance - a pushy car will give a bigger rise, but not always show a greater temperature when you check it in the pits.

Try also toe out in the front if you still have a mild push, or if the car doesn't feel very crisp on initial turn in. Toe out in the rear can also be used to help the car to rotate. Again, a very common tuning aid.

[GTV27]

MA2 - agree with all of that, except for the use of toe out (esp at the front). In my mind, if you have to resort to toe out to get the thing to turn, then something else is wrong and needs to be fixed.

Having said that, the same can be said for camber if you are getting past the -3.0 deg level - if you need this much camber maybe the car should be stiffer in roll to keep it on its tyres? In the end it is a compromise and after all, stuffing around with the settings is half the fun.

[MA2]

Front toe-out is pretty standard on formula cars, and at least over here just about all sedan cars. The idea, put rather simplified, is to get as much grip from the inside tire on initial turn-in. On cars that don't have 100% ackerman, toe-out is pretty mandatory.

As far as camber is concerned, on a mac strut type car with radials, a lot of negative is necessary to counteract the camber loss due to roll. On unequal length a-arm setups, most suffer from a gain in absolute negative camber. On top of this, radials generally will need more negative than a bias-ply due to the reletive flexibility of the sidewalls. Lateral distortion and "tuck-under" increases with narrow tires, so increased pressures and negative camber is necessary.

You'll have to experiment to find out what is right for your particular combination. Don't make the mistake of dismissing a particular change until you've actually tried it!

[gttouring]

i road race and my car running on 225/55 17's my camber is set at -2.5 in both fronts and -2.6 on the back, it is a rear drive (mazda rx-7) and it is heavily ported, so it is reasonably fast, when i am on it, because i many time am not fast. it is pretty neautral and does not over steer much any more, the larger cornering coontact patch on the rears is what's helping. The toe is set in on the front 0.09 and 0 to .005 onthe rears. i don't udse toe out on any front wheel only on the left front of my sprint car, for ovals...

[shiny side up!]

Keeping with MA2, we utilize front toe-out on our formula cars, especially on tighter tracks. Haven't really played around with heavier sedans on twisty courses, so I don't know if the toe would have a similar effect, but perhaps something to try???

[GTV27]

OK I stand corrected on toe out - have not had any experience with 'formula cars', just my Alfa GTV (which runs zero toe, but also has ackerman in the steering, which helps with inside tyre grip).

I can support MA2's comments on radial v's bias ply - I tried some bias ply slicks on the Alfa and it was diabolical (REAL stiff sidewalls) - went back to radials rather than having to reconfigure the front end and probably spring rates to suit.

I am now starting to play with a sports racing clubman that runs bias slicks, so am going to have to get used to them.

[MA2]

Try the toe-out configuration sometime - it might surprise you!

Also, contrary to the old school of thought, rear toe-out is not unstable, but it can enhance initial rotation. I've used it quite a lot in the past on different cars, including a win at Long Beach with a Indy Lights car using a spool (!), and have been pleasantly surprised almost every time.

[laser2]

just a couple of things...scalloping of the tyre under brake..ie flat spot usely occur on the inside shoulder on the unloaded side ie inside tyre to the corner not the outside loaded tyre. V8 supercars and lots and lots of australian touring cars run up to 6 degrees neg ( have seen more) and the brake performance is fine. This is because when the car brakes the tyre contact patch widens due to the amount of weight transfered to the front. It could be argued that having the tyre more vertical in braking would give the best grip level but as braking is usually the area where the car spends the least amount of time (the most is accelerating or cornering) why not emphasis the areas where the most benefit will be.

If you leave your foot on the brake too hard when entering the corner as the weight transfers to the outside the inside unloaded tyre locks. This causes flat spots.

You have to know what "your" car's toe does do under brakes. Some cars 'do' naturally toe out under brakes due to geometry variations in the steering arcs compared to the suspension arcs. Especially when the car is lowered (or raised for that matter) as the geometry will be operating outside the manufacturer's original height where the steering will operate at its debatable/theoretical best. At either end of the operating range the manufacturer's steering geometry can do very bad things. If a car toes out under brakes how much does a car need for good turn in? if it toes in under brakes how much initial toe out would you run to compensate?

as for castor...it only works when you have a fair amount of lock on the steering wheel, like when the car turns in , beyond this point if you have any amount of lock you have some slight to at extreme unbelievable understeer.

[avsfan733]

toe out is fun

[Onlooker]

Originally posted by shiny side up!
The simplest way (but not necessarily the best, as we've discussed on here before) to find a good camber setup is to adjust it until your tire temps are pretty even (within 5C or 10F) across the tread (inside, outside, and center). Thus, if the outside of the tire is hotter than the inside, then you give it more negative camber, and vice versa. This approach will be really thrown off if your tire pressures are out to lunch, however.

The handling problems from missing the camber setup could manifest themselves as under or oversteer, lack of forward grip, or very touchy steering. Actually, it can cause lots of nasty things, it's difficult to make a list because nearly anything could be on it...

What kind of car are you running? What kind of speeds do you carry in corners? What kind/size of tires?weight/weight distribution/cg height? All of those things (and more) can effect the camber setup...

Be careful not to be fooled by a long straight etc prior to pit lane.This can heat up the inside of the tyre and trick you into thinking you have to much camber as can excessive toe.
If you can SAFELY get out on the track (during testing)and check the tyre temps at a point that is say after a set of sweeping bends then you will see what is happening in the real world.
take Phillip Island,Eastern Creek,Calder,or even Winton for that matter,the pit lane or track configuration allows for long periods of straight running or off throttle transport prior to arriving in the pits.

Or whack in a motec and tyre temp sensors and see it as it happens,may be a bit pricey but eh

[rorym]

Excellent read!...For the OZ guys..I am finishing off a HDT LH L34 replica Group C car and am a bit lost on radials vs. bias ply. Stuckey tells me to use a 250/585 on a 8' rim on the front...I will fit one and try it to see if it clears..the rears are 10" 250/585-15s so no0 dramas there. The car is to be used for mainly hillclimb and 1 lap sprints but I might take it to Morgan Park or similiar for the 5 lap sprints as well. I was thinking Dunlop D12 s al round to see how I go. The info here probably save dme **** loads of set up time.
Rory

[zefarelly]

Originally Posted by avsfan733

toe out is fun

in a pants filling uundersteer kind of way . . . I accidentally went testing with toe out ( changed struts) and I killed a set of fronts in 3 hours

on Dunlop M section 204's I run 2 degrees neg camber, not sure on caster angles, need to measure them, but I believe caster helps more than camber

rear end is fixed, so without bending the axle casing I'd assume its neutral from the factory

[Al Weyman]

Also its camber at full cornering speed thats important and different types of suspension will require different set ups, some will gain more camber at full bump than others.

[rorym]

I am still abit lost on why the experts say dial in more neg camber for radials compared to bias ply.
R

[zefarelly]

because the tyres 'roll' less ?

a few people said to me when I started not to worry about camber with crossplys, you want caster . . . how true that is I don't know as I was told a lot of 'Paddock ball cocks' back then . . . .

[jonners]

We run Avon crossplies.

We chose to use crossplies on Avon's advice since our car has a live rear axle and therefore fixed zero toe, camber and caster.

Yokahama had already told us that we were wasting our time using radials with zero settings since on a hillclimber the rear tyres will not get anywhere near optimum temperatures since the runs are so short

Avon explained that crossplies warm up just by going along - because of the crossplies moving [I think]. Therefore it is imperative not to run extreme castor camber or toe with crossplies as they will destroy themselves very rapdily.

Radials do need caster camber and toe to warm up quickly

Avon told us not to exceed 1.5 in either camber or caster so that's what we run at the front

Crossply slicks are just gorgeous to run on - soo forgiving and the most amazing smooth breakaway - but we haven't come anywhere near matching our best time on Yokohama 32 R's....

[Speedy1]

rear end is fixed, so without bending the axle casing I'd assume its neutral from the factory

once worked as a fabricator for a guy doing a lot of Super 7's
( I drove a Mark 1 Lotus Cortina )
we alignment checked all rear axles, none were straight
most tended to be toe out
the method I was taught for checking:
* empty axle housing
* make bushings that fit in place of the bearings both inside the housing and the wheel end. All 4 bushing have common I.D. size (25.4mm?) with an approiate size for the O.D.
* run straight rod (25.4mm?) thru all four bushings i.e. the total length of the housing
* we would cut the outboard flanges off thru the original factory weld and then reweld in the correct aligned position
* basicly line boring application done on the cheap
* depending on the application we might also beef up the housing
Now days, with the presses here I might also try rebending.

[GordonG]

I ran an English axle in a light kit car racer (125bhp, 530 KG) for several years with 1 degree of camber. Just cut 3/4 through the case from the top with a grinder at the inboard end of the tube, bent by hand to where I wanted it, measuring relative angle between the 2 outer faces, then welded a tubular brace in place before welding up the tube.

The splines in the standard driveshafts accepted this angle no problem. You could also get a shade of toe this way too. No reliability issues.

Course, if you start putting hundred of HP and tonnes of weight through it it might suffer more, then it probably would anyway.

G