Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site osiris.UUCP Path: utzoo!watmath!clyde!burl!ulysses!allegra!bellcore!decvax!genrad!panda!talcott!harvard!seismo!umcp-cs!aplvax!osiris!phil From: phil@osiris.UUCP (Philip Kos) Newsgroups: net.auto Subject: Re: Miscellaneous Ramblings Message-ID: <175@osiris.UUCP> Date: Tue, 12-Mar-85 10:53:00 EST Article-I.D.: osiris.175 Posted: Tue Mar 12 10:53:00 1985 Date-Received: Fri, 15-Mar-85 01:48:33 EST References: <330004@acf4.UUCP> <330020@acf4.UUCP> Organization: Johns Hopkins Hospital Lines: 80 (Just a few comments on weight distribution, weight bias, and four- wheel disc brakes.) The reason big old American sedans spin out is because (essentially) all their weight is over the front wheels while they drive with the rear. That "huge, overhanging trunk" doesn't weigh anything. That's the problem: there's not enough weight over the back wheels to keep them planted on slippery pavement. So it's too easy to lose traction at the back, and when you do, because of the severe front weight bias, the back end "comes around". (Can you say "fishtail"? Sure.) Front wheel drive cars have a similar weight bias, but because they drive with the front wheels, they aren't prone to fishtailing. The bias does mean that they handle differently from rear-wheel-drive cars, though - I know a lot of people besides myself who don't par- ticularly like them for this reason (I guess we're just old and get- ting crotchety or something). 4-Wheel Disc Brakes I'm not entirely sure that four-wheel disc brakes aren't overkill. If you're racing at LeMans in the 24 Heures, well, of course you have to have them to last more than a lap, but on most cars they're definitely unnecessary. Most cars on the road today are either small front-wheel-drive jobbies or older dinosaur-type vehicles. These cars all have a severe front weight bias. Now consider braking. Most hard braking is done while the car is traveling forward, right? Well, have you ever noticed how when you're moving forward and you hit the brakes, there seems to be a force pushing you forward that makes the back end rise up and the front end dive? You have? Good. You all pass the pop quiz. Anyway, the net effect of this "force" (which is not really a force any more than "centrifugal force" is a force - it's really inertia) is that the weight bias of the car shifts farther forward, greatly reducing the loading on the rear tires. Now, any time the load on a tire decreases under braking, you're going to have to watch out for lockup. Also, the amount of braking the wheel in question can actually do decreases because of the decreased "lockup threshold". In most cars this effect is not insignificant. (See early GM X-body cars for a good example.) So little braking is actually done by the rear wheels that there is no point in putting discs back there; drums are just fine, and cheaper at the factories, which is why there aren't a lot of 4-wheel-disc cars around. Cars with a more reasonable weight distribution, by the way, will benefit from discs on the back wheels, as will cars with a rearward weight bias (e.g. Porsche 911s, VW Beetles, Pontiac Fieros, etc.). The Vette is in this class. Weight Distribution Proper weight distribution is something I've always appreciated in a sports car. It improves both the handling and the stability of the car. As far as Corvettes are concerned, I won't argue with you on the figures. But think about this: the front-mid engine/rear drive con- figuration was around for quite a long time before Chevy "thought" of it. Look at pictures of cars from the teens, 20s, 30s, even the 40s. My first car was a lowly MGB, not the sort of vehicle that will regu- larly blow Vettes away at stoplights, but it had a nearly ideal weight distribution. So did my second car, a Triumph GT6. Neither of these cars was what I would call "state of the art" in terms of engineering or performance, but they _felt_great_ on twisty roads. I have driven several cars which supposedly could blow my GT6 away canyon racing, but I just plain didn't like their handling. I'll take balance over raw power any old day. BTW - I'd be interested to know what the weight distribution was on the '63 Stingray. Do you have the numbers? Phil Kos Still Looking for a Good Car in Baltimore of course, I could be wrong... :-)