Tire Spring Rate and its Affect on Vehicle Suspension.
Tire Spring Rate and its Affect on Vehicle Suspension.
(OP)
As you have no doubt noted, RunFlat tires are becoming more commonplace. They are reportedly much stiffer than conventional tires and that causes some ride complaints. How does the spring rate of a tire affect the Spring-Mass-Damper system we know as the vehicle's suspension. This question could also be posed with Plus-Sized tires as the tire type.
Here's what I know:
Tire stiffness is mostly a function of tire pressure.
The tire acts as its own Spring - Mass - Damper system with the spring rate of the tires being an order of magnitude higher than the spring rate of the suspension, and the damping being....uh....lower.
Any guidance in understanding this would be greatly appreciated.
The tire acts
Here's what I know:
Tire stiffness is mostly a function of tire pressure.
The tire acts as its own Spring - Mass - Damper system with the spring rate of the tires being an order of magnitude higher than the spring rate of the suspension, and the damping being....uh....lower.
Any guidance in understanding this would be greatly appreciated.
The tire acts





RE: Tire Spring Rate and its Affect on Vehicle Suspension.
Stiffer tires are bad for ride, shake and impact harshness, in most circumstances. You might occasionally find a surface where a stiffer tire is better for ride and shake, because it is stiff enough to break the stiction in the shock and so get the shock working.
The other thing you'll find is that the stiffer tire causes wheelhop frequency to increase. This will change how it interacts with the engine rigid body modes, which will usually make the car even shakier.
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Tire Spring Rate and its Affect on Vehicle Suspension.
But can the suspension be changed to compensate for these changes? What changes would be appropriate?
RE: Tire Spring Rate and its Affect on Vehicle Suspension.
I'm serious about the engine mounts - that's what all the fun and games with mass dampers was about in F1 this year.
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Tire Spring Rate and its Affect on Vehicle Suspension.
on another effect of increasing the tyre spring rate versus the suspension wheel rate, if it is a race car, you would find the tyres take longer to reach operating temp (if everything else compound wise was equal). This is because the energy input into the contact patch will be taken more by the suspension spring, and less by the tyre.
RE: Tire Spring Rate and its Affect on Vehicle Suspension.
RE: Tire Spring Rate and its Affect on Vehicle Suspension.
Not always. We have found that there are conditions where increased pressure will also cause the tire to heat through the contact patch sliding on the surface.