Re: Tires

[douglas.carter@platinum.com]

Chris Collier inquired:

>> 1) has anyone considered going w/ 195/50-15 tires on our cars; the
thought here would be since we have a 6.5" wide rim, the 195's would sit
down in the rim better, thus reducing roll-over; true or false?
Ok, here's my opinion, for whatever it's worth. A narrower tire of the same
aspect ratio (or better yet a 55 series) will sit on the rim just the same
as a 205 will, depending on the tire manufacturer, and within reason. Ten
millimeters or one centimeter should not have too much effect on the way it
beads.

It is said that everything is a compromise, so the question is what does
this compromise? I'm using 195/55-15 snow tires right now, and the first
thing you notice is a lighter steering feel because of the smaller
footprint made by the front. Conversely, there's that much less footprint
to put power down. Real world applications, if you can put the power down
with a skinnier tire, it will be faster. The rotating mass will be less,
thus accelerating and braking will be quicker, to some degree.

Way back when, I used to race RC cars on a pretty high level of
competition. I used to run very fast dirt oval cars, both 2 and 4-wheel
drive. We found that by cutting down the wheel contact patch until it was
small enough to reduce rotating mass (a lot) but still put enough rubber on
the track to get the power down, lap times went up dramatically and power
consumption went down (meaning mileage, essentially). An added bonus was
that the cars were also easier to drive.

My philosophy is that you ideally should use as much rubber on the car as
needed to put the power down consistently. If you are spinning the tires
through the first few gears, you need a stickier compound or more contact
patch. If not, maybe a narrower tire would be faster for you.

This argument doesn't even get into cornering forces put on the tire or the
ability for a narrower tire to keep the car planted in a turn. What it does
do, however, is show that the wide (225) tires drag down as much horsepower
as a larger rim.

Tires need to be matched to the performance of the car they are going on,
just like speakers on a stereo, too much or too little, they aren't going
to work quite right.


Woa, that was long. Sorry.




Doug