Increase track=lower lap times????, is wider better?? Options

[Mueller]

I thought I read someplace where someone was claiming that by increasing the track via wider wheels and tires a few inches(or even spacers) it was equivialant to a 100hp increase in power on large track

I know that is just way too much of a general statement, but could it be based on facts??

[Blake]

Well, any change in scrub radius creates a tradoff by definition. No way around that. It might be a net gain or a net loss, depending on your perspective. If you draw a line through the upper and lower ball joints, you get the kingpin inclination. That line intersects the ground and the difference between that location (center of rotation) and the center of the tire is the scrub radius. If they were the same (zero scrub radius) the effort to turn the wheel would be minimized (best leverage). Also, feedback from imperfections in the road surface will tend to be minimized (again, best leverage). And, so on. The suspension is designed with a certain scrub radius in mind and changing it (like changing anything in the suspension) is pitting your knowledge against that of a highly trained engineer. Now, that doesn't mean you can't accept certain tradeoffs the engineer didn't have the luxury of making and use some common sense in keeping things reasonable. If the car has very light and numb steering, increasing the scrub radius a little s not a bad 'hack' (buying a tigher ratio steering box might be the proper solution). But, if a quarter inch is nice, that does not mean 7/8th is better. And, I would tend to do this after more obvious ways of reducing weight transfer, like lowering the car an inch or so (again, in moderation) or removing excess weight. Anyway, the proof -- and consequences -- are in the pudding; experience is the best judge. I'm not telling anyone not to put on a wide body kit and run super wide wheels/tires on a stock suspension, but you should at least be aware there are potentially real tradeoffs. Just a heads-up.