Puk wrote:To DaveW's point - you can't expect to know the optimal tyre camber to generate max grip and I agree but isn't it likely to be as close to 0* (so that the full width of the contact patch is bearing down on the road surface)??
As in everything, it depends .
Remember that the tire does not maintain a static shape during cornering (lateral) loads. It squirms around and deforms, rolling out from under the rim. We're basically driving around on big balloons.
How much deformation you will get depends on the tire (size, stiffness of the sidewall, etc.) as well as how you drive the car (cornering loads). For an example for Toyo RA-1s on the track the manufacture recommends at least 2 to 2.5 degrees negative camber (andsometimes a lot more) in order to get maximum traction and even wear. This is usually fine tuned at the track by using a pyrometer to measure temps across the face of the tire and see if they are uniform.
For street driving and street tires, less negative camber is recommended. Factory settings for many sports cars is zero camber, since most of your tire wear on the street is from driving in a straight line rather than scrubbing them in the corners.
wrankin wrote:Remember that the tire does not maintain a static shape during cornering (lateral) loads. It squirms around and deforms, rolling out from under the rim. We're basically driving around on big balloons.
How much deformation you will get depends on the tire (size, stiffness of the sidewall, etc.) as well as how you drive the car (cornering loads). For an example for Toyo RA-1s on the track the manufacture recommends at least 2 to 2.5 degrees negative camber (andsometimes a lot more) in order to get maximum traction and even wear. This is usually fine tuned at the track by using a pyrometer to measure temps across the face of the tire and see if they are uniform. -bill
Hi Bill thanks for the input - that does introduce a an important consideration - I'm theorizing that the paper design of the suspension needs to produce the manufacturer's recommended camber under the anticipated steady state dynamic load. I had assumed that maximum lateral force would be circa -0.5* negative camber (ok ok I admit that I plucked that value from thin air) and aimed to allow another degree of track side adjustment to refine it. So if I had gone ahead and built such a design it could very easily have been short of camber adjustment.
I'll see if I can round up some recommended camber values for tyres on a 7 - nothing springs out in a search of the forum (but if anyone knows better please correct me). I'll raise a separate question to see what folk are using.
Cheers,
Puk
Before you judge a guy walk a mile in his shoes. Then when you judge him, you've got a mile head start and you've got his shoes on:)
I spoke to Alan Meaker at Toyo who is their technical engineer in the UK and one time Locost racer. I asked what tyres and camber values would be suited to a Locost type car. He suggested two options the 888 for a track car that did a little road work or a T1R for a road car that did a little track work. He wasn’t able to provide a graph that showed a link between camber, tyre load and grip but did suggest that the value would likely lie between 0* and -4*. A road biased car would be set with a camber values closer to 0 which would likely sacrifice ultimate cornering grip for tyre longevity.
Yokohama's rep who suggested Yokohama, AO48 - R for a track day car. Like Allan Meaker he urged caution when trying to design for the optimum camber, but suggested that suspension geometry that could present the tyre at a negative camber of 2.5* when cornering would be a good starting point. Track testing will reveal whether more or less camber is required to get the best out of the tyre.
I had been naively hoping to design the suspension geometry to produce 0* ish camber at the target braking and the same camber at target cornering acceleration. But this little idea is shattered when it became clear that optimum camber for cornering is not 0 deg. So my current objective is to design for the cornering requirement, as in that mode the outer tyre is doing the lions share of the work, where as under braking the load is spread across both wheels on the axle.
Maybe caster and king pin inclination can be contrived to introduce negative camber in the outer wheel in a bend - at least a the front...
Before you judge a guy walk a mile in his shoes. Then when you judge him, you've got a mile head start and you've got his shoes on:)
Puk wrote:...He wasn’t able to provide a graph that showed a link between camber, tyre load and grip but did suggest that the value would likely lie between 0* and -4
...I had been naively hoping to design the suspension geometry to produce 0* ish camber at the target braking and the same camber at target cornering acceleration. But this little idea is shattered when it became clear that optimum camber for cornering is not 0 deg...
Your first thought reminds me of what I bring up when someone taking about the superiority of a live axle. If it's impossible to set the tires to the recommended camber settings, how good can it be?
Regarding 0 camber in braking, that's easy to achieve... it's when you want a different value in roll, which is exactly the same as far as the suspension knows, as the suspension compresses in both cases. Just realize that everyone else is in the same boat, too, and having a car that's >1000lbs less than anything else is a huge advantage.
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