72 Blu,
[1] So Amtronic in post #62 was just imagining a rougher ride with bigger wheels???????????????? He didn't really feel the difference????
[2] An observant driver[ maybe not you ] will notice that if they have over inflated their tyres, the ride is harsher. This is particularly noticeable if the pressure was low initially, for whatever reason. Why is it harsher?
[3] Run your tyres WITHOUT air & see how good the ride is if you think air is 'inconsequential'. Try solid tyres, no air, & see what the ride is like. Circle track drivers like their tyre pressures right at the amount that they found gives the best handling/braking...within 1 or 2 psi...& using accurate measuring equipment to get it perfect. To them, 1 or 2 psi is NOT inconsequential.
[4] You must have a reading problem, so I will repeat it a second time. You claim that 'tuning'
the suspension to work with bigger 17" wheels/shorter side wall tyres will 'fix' the harsher ride.
If the same tuning is applied to the 14/15" taller sidewall tyre, it will give a smoother ride than the 17"combo. Somehow I think you know this but too gutless to admit it. Because at the end of the day, simple physics is involved....which you either do not understand....or not want to understand because it destroys your nonsense argument. The air in the tyre & the tyre sidewall take the initial 'hit' when the wheel hits a bump. The air inside the tyre is compressible & acts as a shock absorber, absorbing the shock from the bump. If you put more air in the tyre, the extra weight increases the density of the air & it becomes more solid. If it was possible to put so much air in the tyre that it became virtually a solid block, the ride would be veeeeeeeery harsh.
[5] To your question of pressure in the tyre increasing because of temperature increase, I agree, the ride quality does change......but it is so slight you do not feel it. We are getting into semantics here: the tyre [ rubber ] also heats up; when rubber is heated, it gets more flexible. So the tyre carcass will probably expand slightly from the heat....& the sidewall also flexes more. Competing parameters.
[6] Your bigger wheel combo being lighter could be because the wheel is lighter or the tyre is lighter...or both.
[7] Bottom line is what I said in my original post: the bigger wheel combo has less air to absorb the shock from road bumps....& gives a harsher ride, all else being equal. The air in the tyre is the first line of defence when the wheel hits a bump & the more there is, the better it will cushion the bump. The springs, shocks, come afterwards, to deal with aftermath.
1- I'm sure he did feel a difference, and I'm equally sure it's because he's running 17" wheels with otherwise stock suspension and cheap shocks. There doesn't
have to be a difference in the ride of the
car, IF you use the proper components. Notice I have said repeatedly if you slap larger diameter wheels on with stock suspension you get a **** ride? You must match your suspension components with your tires so the whole thing works together. Your tires connect the suspension to the road, nothing else, change those and you have to alter your suspension as well.
2- Yes, the ride is harsher with overinflated tires. And I didn't dispute that. It just has absolutely NOTHING to do with the
weight of the air in the tire. Increasing the PSI in the tire exerts more force on the wall of the tire, which means it can absorb less additional force. (like from the road!) So it has to transmit it. Not difficult to understand.
3- Again, this is NOTHING to do with the
weight of the air in the tire. Changing the pressure in the tire changes how the tire and sidewall deform with loads, this has to do with the
force exerted on the wall of the tire by the pressure of the air inside. Racers of any kind are trying to maximize the grip of their tires, which means maintaining the maximum contact patch under whatever varying loads their sport subjects their tires to. Too much pressure and the tire loses the ability to keep the tire tread flat on the road, too little and the sidewalls roll over with harder cornering. I did not say a change in PSI didn't change handling, I said it has nothing to do with the weight of the air like you claim. I tried to lead you to water by giving the example that the density also changes with temperature, which would mean the same PSI in the tire with less weight of air, but you missed it entirely. The force exerted by the pressure inside the tire is the important part, not the weight.
4- Yes, a tire does act like a shock absorber. Changing the height of the sidewall does in fact change the way a tire absorbs/transmits energy, and I've never claimed otherwise. If you change the way the tire absorbs energy, you must change the suspension to compensate, which has been my point since the very beginning.
The point you seem unable to comprehend is that the frequency, rate and amplitude of the forces transmitted by the tire to the shock absorber change when you change the tire, profile, and/or construction because the tire is transmitting the road inputs differently. Those changes in frequency, rate and amplitude require different amounts of damping, which your shock may or may not be able to accommodate.
The cheap shocks many use have a narrow range where they can keep up and remain near critical damping, they only work well in a certain, narrow range of inputs. A better shock will work over a wider range of inputs, keeping things closer to critically damped with more varied inputs. BUT, if you tune a shock specifically for the inputs you'll get from a tire with a short or low profile sidewall, that shock will NOT give the best ride with a taller tire because the frequency, rate and amplitude of the oscillations coming from that tire do NOT match those coming from a 17/18 tire.
The physics of this is literally what proves you wrong.
5- Nope, right over your head. The
pressure in the tire changes more than the compliance of the rubber, which changes the profile of the tire, which changes the tread patch on the road. If you listen to any modern auto or motorcycle racing discipline, especially F1 or MotoGP, you will hear the announcers speaking at length, every race, about how tire pressure and tire temperature are related AND how they effect suspension set up. Those cars and motorcycles are so sensitive to tire pressure changes they literally set the cars up differently if they expect to be running in traffic or free air because that changes the temperature which changes the pressure. Since no air is being added to the tires in any of those situations, the weight of the air isn't changing at all, but yet, the pressure in the tires remains
critical to performance and handling.
6- No kidding. The larger wheel combo is lighter because the wheel weighs less. Thanks Captain Obvious. Again, you missed the point. The change in the weight of the air between a low profile and taller profile tire is
thousandths of a pound in most cases, which should have made you realize it was irrelevant especially considering you can easily have differences in the several pounds range with different wheel/tire combinations. Orders of magnitude higher. The weight of the air is negligible.
7- Finally realized your argument was horseshit and decided to move the goalposts (again)?
"All things being equal" - this is the problem, only someone that doesn't understand suspension would keep things equal with the suspension when changing their wheels/tires. Literally my point this whole time.
I've never argued that the lower profile tire didn't change the ride BY ITSELF. My entire argument is that if your ride sucks with lower profile tires, it's because you failed to change your suspension to match them. This is true if you put lower profile tires on suspension set up for taller profile tires, but also if you put larger profile tires on suspension intended for lower profile tires. The input from the tires has changed, so, you change your suspension to match.
As I have said
from the beginning- there is no reason your ride quality has to be terrible with lower profile tires, or that changing to lower profile tires means your car MUST ride like crap. Your car can ride just as well with larger diameter wheels and lower profile tires
as long as you change your suspension, and mostly your shocks, accordingly.