Midway, 30k mi, tire report

About 30,000 miles ago, I put larger diameter tires on the front and standard size tires on the rear:

• 195/70R14 (849 rev/mi) - front
• 175/70R14 (886 rev/mi) - rear

This configuration has improved the straight-line stability and so far, no handling problems even with emergency stops. The speedometer and odometer read ~6% low.

I've been looking at the tire wear and both the front and rear appear to be roughly equal. Ordinarily, one would rotate tires front/rear. I had always seen the front tires come off with more wear than the rear. But it makes sense that the slower turning, larger diameter front tires are wearing at nearly the same rate as the rear tires.

The advantages of having larger diameter tires up front:

1. straight light stability is improved
2. 6% overdrive reduces transmission and rolling drag - requires manual calibration and/or use of GPS for speed and distance measurements
3. moves hybrid threshold speed from 41 mph to 44 mph for better city mileage
4. tire-wear front and rear appears to be equal rates - no need to rotate

The disadvantage is acceleration should be slower but I don't perceive it to be a problem as our NHW11 has never been a 'drag racer.' The ending speed of a maximum hill climb is ~91-92 mph versus ~95 mph but this is well within normal performance range.

Bob Wilson

 

Thanks John,

We're probably two years away before testing oversized tires on our ZVW30. However, I might be able to replicate it by reducing the rear tire pressure to the door jam, 32 psi or lower, while keeping the front at 52 psi or a little higher.

Unlike the NHW10, the ZVW30 has acceptable handing and straight line stability. The other attributes are not quite as important in the ZVW30 as the NHW10 gets a nice urban speed improvement. Then I keep thinking about the 'donut' spare that to my eyes looks significantly smaller . . . not that I have one any longer. I replaced it with a full-size spare.

As for grip, I would have though having the steering and drive wheels in firm control would be more desirable than the rear. But this is not an area I have any expertise . . . I don't drive that way.

Bob Wilson