Are tall skinny tires the future?

[NHB]

I really believe that these tall skinny tires are the future of tires. Less rolling resistance, less aero drag, less noise, better performance in wet conditions... I only wonder that why it took this long? BMW will roll out i3 soon and I'm sure that it won't be the last example. Hopefully more conventional cars like BMW 320 EfficientDynamics edition will get tall & skinny tires soon.

[Miller88]

Load rating has more to do with the load rating of the tire than the size - it's redundant, but it makes sense.

I went from 195-60-15 to 185-65-15 on my car. Load rating is the same between the two.

[RedDevil]

Within certain limits only.

A conventional CVT can couple any number of revs to any kind of speed, within the limits of the CVT. So on the highway I'm always on the far end of the scale ('top gear') and my RPM rise in tandem with speed.

The Prius has a HSD drive, which is a planetary gear set with additional electric motors and generators that simulate CVT behaviour. It has 3 gear ratios where the electrics don't have to do anything (the gearbox is switched to one of its 3 gears matching the ratio needed) and then it will be at its best, probably more efficient than any other gearbox.
In between the motors and generators compensate for the unmatched ratio and cause a slight loss of efficiency. On the whole, still better than my CVT.

Best of all, you can have a HSD gearbox in any brand of car, as long as that is Toyota.
Patent laws...

Because of the workings of the HSD there is no strict limit to the ratio, it can be 'infinite' (engine stalled, electric motors running).
The art is to make the gearbox work at its most efficient ratios for your regular use. Changing the tire size may help a bit. But as the transitions in the gearbox are seamlessso is the effect on efficiency; there are no sharp cliffs.

[euromodder]

Originally Posted by Miller88

Load rating has more to do with the load rating of the tire than the size - it's redundant, but it makes sense.

LI is just what the tyre manufacturer wants it to be ...
It's something they design into the tyre, given its intended use.

[user removed]

Originally Posted by RedDevil

Within certain limits only.

A conventional CVT can couple any number of revs to any kind of speed, within the limits of the CVT. So on the highway I'm always on the far end of the scale ('top gear') and my RPM rise in tandem with speed.

The Prius has a HSD drive, which is a planetary gear set with additional electric motors and generators that simulate CVT behaviour. It has 3 gear ratios where the electrics don't have to do anything (the gearbox is switched to one of its 3 gears matching the ratio needed) and then it will be at its best, probably more efficient than any other gearbox.
In between the motors and generators compensate for the unmatched ratio and cause a slight loss of efficiency. On the whole, still better than my CVT.

Best of all, you can have a HSD gearbox in any brand of car, as long as that is Toyota.
Patent laws...

Because of the workings of the HSD there is no strict limit to the ratio, it can be 'infinite' (engine stalled, electric motors running).
The art is to make the gearbox work at its most efficient ratios for your regular use. Changing the tire size may help a bit. But as the transitions in the gearbox are seamlessso is the effect on efficiency; there are no sharp cliffs.

Toyota lost a lawsuit for Patent infringment to an American company in Florida, for their hybrid synergy drive, and they were court ordered to pay a royalty on each hybrid the ysold in the USA. Not sure about the rest of the world or whether they won the case on appeal after that initial ruling.

regards
Mech

[RedDevil]

Originally Posted by Old Mechanic

Toyota lost a lawsuit for Patent infringment to an American company in Florida, for their hybrid synergy drive, and they were court ordered to pay a royalty on each hybrid the ysold in the USA. Not sure about the rest of the world or whether they won the case on appeal after that initial ruling.

regards
Mech

According to the (disputed) Wikipedia article about the HSD Toyota (and Ford) have to pay a license fee to the Paice company. The Antonov company also sued Toyota, but lost.

Nice snippet among the patent issue explanation:

The electrical path is only about 70% efficient, thus decreasing its power flow while increasing the overall performance of the transmission.

That is 70% efficiency between the closest physical gear ratio and the one simulated, if I interpret this correctly.
So if the system reduces the physical gear ratio by 20%, the gearbox would be 80% + (70% * 20%) = 94% effective (assuming the planetary gearing is near 100% effective)
A conventional CVT will lose at least 10% in any gear ratio.

[freebeard]

I can wait, but I still want these to be the next tires I buy. To replace 165R-15.