It should have Rolled.

My Highlander Hybrid 4WD-i was equipped with Goodyear Integrity tires, I replaced them after 6K miles. I replaced the Integrity tires on my 2004 Prius after 15K miles. However, a recent poll shows that a large proportion of Prius owners have gotten substantial mileage (30K+ miles) out of those tires.

Glad that the OP and his daughter were unharmed. An excellent lesson for her, I hope this incident will encourage her to keep focused on her driving at all times, not to overcorrect when a situation arises, and to not use cruise control in adverse conditions (i.e., rain, snow, high wind, poor visibility, etc.) The racing lessons should also help her to understand and not to exceed the limits of the vehicle being driven.

If the OP believes that his Prius handling is unusually skittish, then it would be reasonable to have wheel alignment and tire pressures checked. If those are OK and the problem persists, maybe new tires of higher quality would be in order.

 

read only up to this point.

glad you are ok.

i am appalled, especially after what happened that you are justifying your daughter's actions.

how would you have felt if she had been killed??

think about that for a bit.


**edit**

ok, read the rest of the thread. i am concerned that you feel your daughter's training allows her to ignore the speed limit. this incident seems to suggest her training was inadequate, she is simply too young, and you as a parent are giving her the wrong impression. high speed driving is for closed circuit tracks only.

i hope she gets several tickets and learns to obey traffic laws before anyone gets hurt.

no response from you is necessary

 

Hi Nick,

I'm interested to hear about your evaluation of these tires. Some of the 2010 Prius that we saw in Detroit and Los Angeles also had Bridgestone Ecopia tires installed, although a different model than being offered for aftermarket sales in the US.

 

I've done some things in my life that by rights should have killed me. So I'm certainly not qualified to judge your daughter. It sounds like she made a mistake and recovered from it imperfectly. The skids mean her reaction was not perfect. The fact that you both survived means that her reaction was adequate. And adequate is good enough. Give her a hug for adequate.

I'm glad you both survived, and I imagine the driving lessons will improve her skills. 17 is a dangerous age, and I think that few of us who have been 17 would have done any better than your daughter did. Let she/he who has never made a driving mistake be first to criticize Nick's daughter.

Of course, driving over the speed limit is a bad idea. it would be nice if your daughter was among the one-tenth of one percent of us who obey the speed limits. But again, few of us are qualified to cast aspersions. May we all be stopped by a cop and ticketed any time we go over the limit! It would do us all good.

 

That almost sounds Biblical. :madgrin:

But I agree, most everyone has done something that should have gotten them killed. If you were fortunate enough to survive, learn the lesson and go on.

 

I'm glad you are keeping us updated on the whole process. I, too, would like to hear about your driving impressions on the Bridgestones.

I've given you my responses/reactions to the whole event earlier, and there is no need to repeat what I said earlier -- except to say that I'm glad you two survived uninjured and thankful were willing to open up and share everything that happened with those of us on PC. This allows what you've learned to be shared with us as advice and warning.

 

I had to do a fairly agressive zig-zag at freeway speed, no time for brakes to avoid a huge roll of carpet that dropped off a truck. No problems what so ever. That was on the old OEM Goodyears. With the BFG sport tires I now have, its ready for the autocross. Who says Prius doesn't handle turns well?

 

Finding the brake pedal was not the problem, she did the right thing by NOT hitting the brake in that situation.

 

Speedometer accuracy, 1%? Speedometer accuracy 1 mph? Spare us!
Surely there is NO exact number for ANY driver to claim. The accuracy depends upon the rolling radius of the specific tire, which varies itself for different temperatures, different states of wear on the tread, different tire pressures and different vehicle loads. Add these variations to the stated theoretical 1% accuracy and you will see that the speedometer is only giving a transient approximation of vehicle speed.
For example, bicyclists calibrate their cyclometers by inflating tire pressure exactly, and measuring the length of travel of the bicycle/rider combo on a smooth surface for exactly 1 revolution (using valve stem plumb), accurate to about 1mm-2mm out of perhaps 820mm total for about 0.5% accuracy AT THOSE CONDITIONS. I don't believe that ANY car can EVER be setup to such exact calibration standards.
The vehicle in question wasn't even using original equipment tires! Who knows how that rolling radius compares to a factory tire/pressure/temperature rolling radius?
You will have difficulty knowing speedometer accuracy in a measured mile to 1% (1/2 sec) even with electronic timing sensors because your speedometer doesn't have a 0.1mph precision in its read out.
Come on....

 

No part in the Prius transmission can slip. The car needs to know the speed of the three components (engine, MG1, MG2) very precisely so it can perform torque balancing. I'm confident that the shaft speed of MG2, at least, is very accurate.

As you say, tyre rolling circumference is something of a hazy measurement changing with brand, temperature, inflation pressure, and wear. It shouldn't be a very large percentage change, though. A new tyre has perhaps 8mm of tread; the legal limit here is 1.6mm. That's a drop of 6.4mm. In circumference terms it's about 40.2mm. The nominal rolling circumference of the design spec 185/65 R15 tyre is 1952.5mm, so the difference between the new and worn tyre is a little over 2%. The car will travel 2% less distance on the worn tyre, per revolution, so will be going 2% slower than indicated.

(Note that most tyre companies and motoring organizations recommend changing at 3mm tread remaining; stopping distances are greatly increased with only 1.6mm tread.)

There's a legal limit of how much the speedometer can vary and for the UK I believe it is -4%, +10% (i.e. it's allowed to read at most 4% below actual speed, 10% over). On the UK Prius, Toyota appear to have programmed the speedometer to indicate 10% higher than the road speed calculated from MG2's rotation speed. I don't know if the calculation is compensating for the different tyre - all UK Prius came with 16" wheels, using a 195/55 R16 tyre. This tyre is 0.1% smaller (nominally) than the tyre used on the 15" wheel.

 

The OP's daughter had cruise control engaged. She needed to tap the brake pedal to disengage the cruise control (or else pull on the cruise control switch to achieve the same result.)

Then she should have slowed the car down gradually using the brake pedal, until the car was moving slow enough so that it would be safe to reenter the highway from the lower shoulder.

 

Yes, having an expected variation of up to 4% which might result in a reading of up to +/- 2 or 3 mph variation at 65mph depending upon round-off, would not be at all surprising. Tire inflation variations on rolling radius are probably at least of the same size of effect as tire wear variations. These rolling radius tire speed variation factors are reflected as gas mileage accuracy as variations
as well!

Changing rim sizes and using non-standard profile tires could add even more speed/mileage variation.

Programming in a +10% speed error is a bit of an eyebrow lifter, but it clearly would cover a multitude of sins in eclectic tire selection, overinflation (hypermilers push it up), etc., to prevent unintended speeding!

 

Crosswinds are very dangerous, and certainly "the flats" have their share of higher speed gusts and sustained winds. Driving slower helps. In straight line crosswinds of 60 mph tractor trailers blow over, at 80 mph locomotives can blow over. So, in severe winds there is NOTHING you can do except seek a sheltered route or drive very slow, or stay put. Prius has a larger side profile that makes it somewhat more susceptible to side winds than some heavier, smaller, or lower profile cars (Miata). There are threads here about stiffening your suspension, and it does improve response and feel. However, there are winds that will trump your best efforts, even in a locomotive. The Great Plains have had whole trains blown over on occasion!

I think it would really good to plant shrubbier TREES alongside I-88 in that area. Reducing wind velocity and sucking up carbon are two nice goals.

After having driven a VW "microbus" with a canoe on top along Lake Erie in crosswinds, my Prius actually feels like it is on rails!

 

Do you plan to add a front sway bar before taking it to Glen Autocross? If not, a before and after comparison would be quite interesting to read.