Trying to understand rear-track width

[xaugievike]

I'm suffering from newbie over-analyzation.

I've been told that widening the rear loosens the kart, and narrowing the track tightens it....my "rear-end gauge" has told me that this advice is true.

but I can't wrap my brain around that....my mind wants to think that widening would tighten...narrowing would loosen.

Isn't the idea with the rear axle to get the inside rear tire to "lift" to make turning easier? If so, I cant grasp how a wider rear end makes that easier for the kart chassis to achieve...

[Jeff Stamper]

More Leverage and spreading the weight out farther. Look at it like this. If you were able to pull the tires all the way together in the center of the axle, it would have all the weight on that spot. If you move them all the way out, you have distributed the weight to a much larger area. with the same 14 in contact patch. When you move them out it will help you pick up the rear, but its because of weight shift to one tire. And to answer you other statement, no one said moving them in would make it corner better ! It wont. It will make it want to push. That is the special spot we are all striving to find ! the Proper amount of traction and the ability to turn ! All of this is cool, but what about the front end also controlling both rear grip and rear jacking ! Whole different story there !

[rct25]

I'm suffering from newbie over-analyzation.
...


When you get over that....you will get fast!
Just drive the kart and have fun; eventually you will get fast.


Good luck!


Roberto C.

[Rick]

It is due to the fact that karts, unlike cars, do not have a rear differential. This causes the kart to want to understeer if both rear tires are on the ground. This is due to the fact that most of the weight is on the rear axle. Kart chassis are designed to lift the inside rear wheel to allow the kart to turn more "freely" (without friction of the inside rear tire touching the ground).

By lengthening the rear axle, you lengthen the leverage you have to lift this wheel. Longer, generally equals more leverage which in turn usually means easier to lift the inside rear wheel. A more narrow width generally makes it harder, therefore tighter.

For some weird reason, there might be a point at which narrow becomes looser. This has to do with the triangulation of the seat to the axle, etc.

You will have to learn how to feel all of this over time.

[JET Karting - Andy Finke]

I think part of the equation you are missing is the chassis flex. The 'softer' the chassis, the looser. When you widen the track, you are creating a longer 'lever' to flex the chassis with, and therefore making it seem softer.

You could also take the bolts out of the middle bearing cassette and replace with zip-ties, loosen the rear bumper, use narrower hubs that don't stiffen thee axle as much, etc.

If you go very stiff and narrow, you can get the kart to 'tip' and transfer the weight. It's VERY tough to get that setup even close to as predictable as the wider setup. Tippy goes to far quickly.

You can also get too soft, but that will be pretty difficult in a Spec Racer.

Does this help?


Andy

[xaugievike]

Thanks for the replies guys....

Like I said in the OP - my rear end "gets it"....

I'm just trying to wrap my brain around the concepts....obviously handling isn't always totally dependent on one area, but rather is a result of many different chassis settings/adjustments as Andy (the wise sage that he is!) pointed out.

And ultimately the biggest factor is the lump sitting behind the steering wheel anyway! If I've learned nothing else in the last 5 months it is that!

And thinking about stuff like this sure beats workin'!