Static Loadad Wheel/Tyre Radius 2

[brentonschnaars]

Hey guys just seeking some input for a formula to work out the Static Loaded Radius of a wheel/tyre. The variables that come to mind are Tyre pressure, Unladen mass of vehicle, Strength of side wall of tyre, Stiffness of suspension. When wheel manufacturers calculate for test loads what data do they use for their tests? eg Static loaded radius of largest tyre to be used on wheel will depend on what tyre and which vehicle the data is derived from. I understand i can ascertain the STL using a FEA but am lost as to how to define the variables to a point that will be sufficient for standards testing. Any input you could give would be appreciated

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[brentonschnaars]

i have bought the new standard SAE J 2538 which is different to AS the amount of tests required on each wheel as well as the factors for test loads, Because the test house is in US they use j 2538 so i have to supply my own test specifications.

One thing i cant find is an organisation who actually gives type approval for automotive products in australia. Any ideas?

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[CapriRacer]

I think it might be helpful if you scanned the pertinent pages of the standard. That way we could look at what is required and give you better advice.

BTW, SLR is highly variable in tires and there isn't a universal formula that will cover every conceivable combination - BUT, some educated guesses can be made. Having said that, I noticed that while there have been suggestions to use 10mm as the deflection, I also noticed that we still don't know what type of vehicle the rim is intended for. I think we've all assumed this is for a car, but that is not clear. Obviously the deflection for a truck would be different.

 

[brentonschnaars]

Capri,


Unfortunately they are copyright so not so sure about posting the standard. Sorry about not specifying the type of wheel, your correct in assuming its a light alloy wheel. The standards I'm referring to are only light alloy road wheel applicable. I agree that the SLR is highly variable so will be working with the largest Unloaded radius possible relating to specified diameter including tolerances in the T&RA manual. By doing this it only increases the test load so the wheel will meet a standard greater than specified. that way i cant go wrong, but what I'm at a loss at is why they have used this equation instead of other equations as in UNECE or SAE.


Thanks everyone for the discussion and your comments

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[patprimmer]

I think it is legal to post extracts from copyright material, but I am not sure how far that can go before it infringes.

I stick by my earlier statement, take the highest unloaded radius or half the stated rolling diameter for the tallest tyre available, then add 10mm to cover the possibility of taller tyres being released in future.

Regards

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[brentonschnaars]

Pat,

I called Australian standards to check with them a few weeks ago for one of the test houses wanted a copy of the testing appendixes, AS explained unless it was copied for an company that is a division of the company who bought the standard its illegal to reproduce in any way. I hardly think that is fair when all it is would be the way to perform the tests and nothing that i wouldnt have to specify if i didnt copy it.

Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic