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Prius Tire Tuning - Page 7

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Posted by Elmo P. Shagnasty on May 21, 2011, 12:10 pm
In article

...which has nothing at ALL to do with braking performance, which you
declare to be "the same" despite your total lack of data--

--and then you demand that if the world doesn't like your declaration,
it's up to the world to prove you wrong.

Yeah, bob.  Sure.

Posted by bwilson4web on May 21, 2011, 2:35 pm

.. . . (troll scat that will soon disappear)

As I was saying:

Prius alignment is normally limited to just front toe, the angle the
tires are pointed inward or outward. Camber is the vertical tire angle
and on the front and may require a new camber bolt, ~$.00. Toyota
documents a rear wheel toe adjustment but it requires a special tool
that appears to bend part of the rear axle, a smaller version of a
frame bending.

Another approach is to use shims that adjust the rear wheel hub,
mounting bolts. Each hub is held by four mounting bolts:
The upper tube is the brake line, the round sensor is the rotation
sensor used by the ABS. The four bolts hold the hub to the axle. But
there are two shim styles available, tab and disk.

The tab systems come with a box of assorted sizes, ~$5-25. Pairs of
shims are put on adjacent bolts, vertical pair for toe and horizontal
pairs for camber:
By putting them on in pairs, there won't be any rocking motion after
the bolts are torqued. If anyone wants to try the metal tabs, I have
left-over tabs and have no problem with sending a set for both rear
wheels. Send me an e-mail with your address and Prius make and model.

First adjust the wheel with the worst toe. Then put tabs in the
opposite wheel to adjust camber. Sad to say, a certain amount of
experimentation is needed:
I first put a pair of 1/32 inch shims on on rear wheel and instead of
decreasing the toe, the pink and red lines, it made it worse. So I
removed those and put a 1/64 inch shim on the front and the toe for
both rear wheels came right into the value I was after, nearly zero.

Wheel alignment measurements can be expensive so I bought a life-time
alignment service from Firestone. I understand other tire chains offer
similar services but check the terms and conditions. So far, Firestone
has been very good about it and I only go back for a second reading if
I make a change. Sad to say, none of them have figured out that
perfect, four-wheel alignment could be a nice profit center.

In a similar fashion, I used a pair of 1/16 inch shims on the opposite
hub and over corrected. Replacing them with 1/32 shims brought both
rear cambers to nearly zero. Notice that changing the camber had a
very small impact on toe.

The other shim style are two, slightly tapered disks, the EZ shim
system, ~$5/disk, two required:

Using a table or the Specialty Products online tool, the numbers
around the edge are rotated so the two disks correct both toe and
camber. Tabs are removed for the bolts. This is the system I'm using

I switched because the metal tab system will always leave a gap
between the hubs and axle:
The ends to the metal tabs can be seen sticking out of the hub-axle
mating in the bottom-center of the photo. But you can see the
accumulated road grime on the black painted axle and this is not
something one wants between the gap.

We seldom have salted roads in North Alabama but any gap is a place
where air and water, especially salt water, can come in and rust or
corrode the gap. Although the zinc coated tabs are probably OK, they
remain another potential source of corrosion. In contrast, the plastic
disks blocks water and air and can't corrode. They are available from
(Amazon.com product link shortened)

Excessive camber leads to one side of the tires wearing out first. But
poor alignment, especially toe, can make Prius steering and tracking
unstable as well as wearing out the tires. So before trying different
diameter tires, make sure the alignment is as perfect as possible.
Then increasing the tire diameter, especially for the front wheels,
completes the job. It also improves braking stability by preventing
wheel asymmetry from coupling with the braking forces.

Bob Wilson

Posted by Elmo P. Shagnasty on May 21, 2011, 7:50 pm
 In article

Show us again, bob, where is your data regarding actual braking
distances--and not just your claims that "well, the car braked"?

We're still waiting for your actual data that PROVES what you claim.

What, no charts and graphs?

Posted by bwilson4web on May 21, 2011, 10:19 pm

Another boring driving day as the car ran and the brakes worked just
fine. With the warmer temperatures, it showed 62 MPG for the 26 miles
I drove on Friday. It really is a superior car.

Bob Wilson

Posted by Elmo P. Shagnasty on May 22, 2011, 3:23 am
 In article

The question was, Bob, do you have actual data to back up your claim
that braking distance/performance is unaffected by changing tire sizes?

You don't.  All you can say is that they "worked just fine".  No data

Is that what your pretty charts and graphs are full of?  Random "I say
so therefore it is" numbers?

Certainly if some numbers show up that you don't like, you simply ignore
them.  That seems to be how you do things.

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