It's been a while since we had a chassis Q&A, but we now have veteran chassis builder and Pro Mod racer Tim McAmis to give you the benefit of his years of experience. So keep those questions coming to chassis@racingnetsource.com and look for the answers right here in Check Out This Chassis!

Dear Tim,

I'm planning on building a tube chassis car. Haven't decided exactly what just yet. Can a guy with welding experience and a Greenlee tubing bender builde a chassis in my home garage that will pass tech?

I'm a good welder and have bent lots of exhaust pipe, so I feel I can bend tubes pretty well. I'm planning on buying the Old Joint Jigger for easy tube notching.

I'd like to do this all myself so I can say I did it, and also because this will be on a tight budget. But I don't want to make something unsafe. Am I in over my head?

Greg Rourke

Greg,

If you have some general fabricating experience you should be just fine as long a syou're talking about doing the chassis in mild steel. A 4130 25.1 D spec. chassis is going to be a little bit tougher with the bender that you are going to use. You may want to buy a chassis print from a reputable builder to give you some guidelines to work by,.

Whichever way to decide to go, make sure you get the rulebook for the class you are running and also the SFI spec sheet for that particular chassis.

Good luck.

Tim McAmis

Dear Tim,

I have a '68 Nova with a ladder bar and coil-over suspension. My question is in regards to the pre-load of the rearend. I was told that, when jacking the car up under the hog head, you should actually see just a little bit of daylight under the driver's side tire before the passenger's side tire. Is this correct or should it be the exact opposite? (Common sense would be they way I was told).

The reason I'm asking is that when I launch the car, it drops over to the passenger side very badly. Before it would launch evenly. Looking at the black marks, both tires (with exact same tire pressure) the driver's side leaves a nice even black patch all the way across, but the passenger tire leaves a black patch only in the center.

Just to give you some info on the car: it has a 6 point cage, three-way adjustable shocks on the rear set at 50/50, 90/10 shocks on the front, sub-frame connectors and the tire is 29x11.0 slick. The best the car has ever 60-footed was 1.65. This is a stick car. The shocks and coil over springs on the rear are brand new, as well as the front shocks.

Any thought or help is very much appreciated. Thanks.

Keith Cambron

Keith,

If the car was going straight, then pre-load adjustment is not necessary. Pre-load is used to transfer weight from one tire to another and should only be used to correct a directional problem with the chassis. Jacking up the car under the center section is a good way to tell which tire has more load on it without putting it on scales, but you should use a piece of round solid rod to keep the pivot point as small as possible.

Tim McAmis

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