How to check if the chassis is straight?

Bill Lin · Joined: 18 Jul 2010 Posts: 14 Location: Canada, B.C,

Hi,

I have a problem with the kart having massive understeer on right hand turns, but on left turns it's fine. I want to check if the chassis is straight. Can anyone give me tips on how to do this?

I'm still a beginner so I don't have experience in this..

Thanks,

Bill

Jim White · Joined: 21 Jul 2001 Posts: 999

A couple of simple things to do will give you a pretty good idea. Measure from the rear axle to the top of the king pins. Should be equal side to side (unless you are oval racing).
Another trick I learned is take all the wheels off and place a long straight rod across the top of both king pins (spindles must be spaced up and down equally on both sides. Now stand behind the kart and sight across the ends of the axle to the rod on each side. They should be equal. If one side is higher than the other you have some twist. This is more than likely what you are dealing with. No big deal to correct that.
The more expensive way is to scale the kart (unless you got a buddy with a set of scales). Chances are if it was fine before and this just started than you've developed that little bit of twist.

Richard Gray · Posted: Mon Jul 25, 2011 3:25 pm Post subject:

Two things come immediately to mind. You could scale the kart as Jim said, with driver, and compare weights; side-to-side and cross. If, from that, you suspect it is bent, take the seat off, place a string from one kingpin to the opposite side bearing mount, do the same thing for the other two points. The two strings should touch at their cross over point (you have to do this twice, starting with the opposite points so that one string is over the other on one try and under on the other try. If the strings don't touch (or come really close in both tries, the the chassis is twisted.

Yes, chassis can be straightened.

BTW, where are you (perhaps someone near could help)?
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Bill Lin · Joined: 18 Jul 2010 Posts: 14 Location: Canada, B.C,

Thanks guys for the tips. I'll give those a try.
Richard, where is the bearing mount? Is it the mount for the rear axle?

If the chassis is bent, how can it be straightened?

I live in Vancouver, Canada. The closest shop will be ItalianMotors, I suppose I can take it to them for a look at if all else fails.

thanks guys.

Bill Lin · Joined: 18 Jul 2010 Posts: 14 Location: Canada, B.C,

I tried to measure from the front kinpin to the rear axle. However, the engine is in the way on the driver-right side.

Richard Gray · Posted: Tue Jul 26, 2011 4:27 am Post subject:

Walt Gifford · Posted: Tue Jul 26, 2011 7:56 am Post subject: Check the roll out

Check the roll out and caster/camber settings both sides, you might have one tire bigger than the other.

Gif Cool

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JIM SILVERHEELS · Posted: Tue Jul 26, 2011 2:17 pm Post subject: Straight?

I'd check if there were any rainbow colors on the kart 1st !
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Walt Gifford · Posted: Wed Jul 27, 2011 9:21 pm Post subject:

Chris Reinhardt · Posted: Thu Jul 28, 2011 4:43 am Post subject:

Go with your baseline setup first before you jumping at a bent chassis...

Check the rear axle first: Equal length sticking out measured from end of axle to the bearing. Axle ride height equal both sides, all up or all down. Have somebody sit in the kart and loosen all the cassettes, then tighten(axle all up), or put some lumber under the frame(wheels off the ground) and have somebody push on the axle(axle all down).

Once the rear axle is set, put it up on the stand, put a level across the rear axle, shim the back of the frame (screw driver) until it's level, put a level on top of the king pins, should be level also.

The other thing you might want to check is if the axle is parallel with the front end. Lock the steering straight, set zero toe on the front, measure from the front axle stubs to the rear axle on each side, should be equal.

Hope that helps...

CR
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Cesar Rull · Posted: Thu Oct 11, 2012 12:16 am Post subject:

sorry to bring this thread back to life after so long.

I noticed that my chassis is a little higher on the rear on the side where the motors goes. The chassis is bare with no seat or motor at the moment.

The different it height it about 1/4 - 1/2 ? - I can't help to think that kart (a sprint CRG) was setup like that to compensate for the weight of the motor, but at the same time something tells me that in a kart with no suspension, ride height should be the same from left to right.

What do you guys think ?