KBS/QRE rear track

Technical discussion, questions, answers and information
Chris Reinhardt
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Joined: Sun Dec 04, 2005 12:18 pm

KBS/QRE rear track

Postby Chris Reinhardt » Sun Jan 13, 2008 5:10 pm

I'm setting up a new QRE 4 link rear and I'm a little puzzled by the rear track spec. The rear track is supose to be 45", and I know that can't be to the outside of the rear wheels!!! Is that measured to the outside faces of the rear hubs or ????

CR

jim l
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Location: United States, Ohio, Cleveland

Postby jim l » Sun Jan 13, 2008 6:17 pm

track is typically to the centers of the tires (track)

Chris Reinhardt
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Joined: Sun Dec 04, 2005 12:18 pm

Postby Chris Reinhardt » Sun Jan 13, 2008 6:31 pm

Jim, does 45" center to center of the rear tires sound about right for your car?

CR

Richard Schmidt
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Location: United States, Minnesota, Plymouth

Postby Richard Schmidt » Sun Jan 13, 2008 8:00 pm

Chris,

The GCR (pg 227) states that the maximum width is 55 inches. This would be measuring from the outside of one wheel to the outside of the other wheel. (not to the rim) Minimum is 50 inches.

Richard
KBS #6

jim l
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Joined: Fri Mar 16, 2007 10:12 am
Location: United States, Ohio, Cleveland

Postby jim l » Sun Jan 13, 2008 8:57 pm

I couldn't honestly say, but others here might know. I just set up the car close to 55" at the edges of the inflated tire. I might narrow things as I need for handling's sake. Wider is better except when it is worse...like less is more except when less is less.

Chris Reinhardt
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Joined: Sun Dec 04, 2005 12:18 pm

Postby Chris Reinhardt » Mon Jan 14, 2008 6:59 am

I'm working with the axle out of the car, with bare rims. If I measure 45" center to center on the rims, it's just shy of 54" to the outer most part of the rim. Now then, the tire must bulge past the rim slightly, is that where they tech?
Jim, I'm not 100% sure how it works on these cars, but from my experiences, you want to narrow the car up as much as possible for straight line speed, making it only as wide as necessary to turn the car.

CR

Chuck McAbee

Postby Chuck McAbee » Mon Jan 14, 2008 8:15 am

The 55 inch maximum width applies wherever it is. The tire bulge is a part of the measurement. If I recall correctly, several years ago, when both Goodyear and Hoosier were tire suppliers to the class, several drivers changed tire suppliers for a National or the Runoff's (the mind is a fuzzy thing to loose) and were DQ'd because the tire bulges of the tires were not the same. They had their cars a max width with one supplier and the other supplier had slightly more bulge....enough to exceed the 55 inch requirement.

jim l
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Location: United States, Ohio, Cleveland

Postby jim l » Mon Jan 14, 2008 8:41 am

[quote="Chris Reinhardt"you want to narrow the car up as much as possible for straight line speed, making it only as wide as necessary to turn the car.

CR[/quote]

That is the goal of road racing, I think.

Ed Capullo
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Location: United States, Connecticut, Norwich

track

Postby Ed Capullo » Mon Jan 14, 2008 5:23 pm

Gentlemen
Please check page 56 2nd para "Tune to Win" by the late Carroll Smith.....very interesting.
I also found interesting the concept tried by a FF at the Runoffs of using front tires on the rear..I presume to get less drag and more straightline speed??
Captain Eddie

Phil Green
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Location: United States, Michigan, Holland

Re: track

Postby Phil Green » Mon Jan 14, 2008 7:15 pm

For those of you who may not own this book (tisk tisk...)


Tune To Win - Carroll Smith wrote:TRACK AND WHEELBASE DIMENSIONS

The last geometrical considerations which we will consider are the length of the wheelbase and the widths of the track dimensions.

The advantages of a relatively long wheelbase are increased straight line stability, reduced longitudinal load transfer and pitching moments, somewhat easier reduction of the polar moment of inertia and more room to put things in.

The advantages of a relatively short wheelbase are reduced overall weight and increased maneuverability.

The advantages of wide track widths are reduced lateral load transfer for a given amount of centrifugal acceleration and room for longer suspension links. The major disadvantage is increased frontal area. When we get into aerodynamics, we will see that, at least on open wheeled cars, the importance of frontal area is overrated.

Very basically, the racing car with a long wheelbase and relatively narrow track widths will be very stable in a straight line at the expense of cornering power and maneuverability. The vehicle with a shorter wheelbase and wide tracks will be less stable, more maneuverable and will develop more cornering power. It will also be more difficult to drive to its limits. In general I favor moderately long wheelbases and wide tracks. I will point out, however, that if all of the corners are very fast, the disadvantages of narrow tracks can be overcome with aerodynamic downforce and, for USAC type racing the idea of a narrow tracked car with long suspension links and reduced front area is very attractive.

The situation becomes more complex when we consider the relative width of hte front and rear track dimensions. I believe that the front track should be considerably wider thant he rear track. More heresy! My reasons have to do with turning the car into corners and jumping on the power coming out. The wider the front track, the more resistance there is going to be to diagonal load transfer and the lesser will be the tendency for the car to "trip over itself" on corner entry and/or to push into the wall from the effect of the drive on the inside rear wheel when the power is applied. I believe that most of our present road racing cars, with roughly equal front and rear tracks, would benefit from an increase in front track width. The slower the corners to be negotiated, the more important this relative track width becomes.




Hope that helps someone!

Thanks Carroll!
Phil

jim l
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Postby jim l » Mon Jan 14, 2008 7:48 pm

Well, that states the present state fairly well. I guess our builders know something after all (joke).


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