AM29x Chassis Problem

[A.J. Codalata]

Chassis Type AM 29 X
Seat position 60 1/4 left
61 right
22 1/2 axle to seat
Flush with bottom of frame rails
1 set of struts
1040-M Axle
Short Hubs
131 1/2 Rear Width
1 1/2 Spacers on Inside of front wheels
Aluminum Wheels
Zero Pills / 2 mill toe out
Dunlop 4.50x5 Fronts 6.00x5 Rears SL-4 Compound
Driver weight is 90lbs medium height, we are running SSX Junior Can Weight 305 at New Castle

The track picked up quite a bit of rubber over the weekend, more rubber then it has ever had. We were quick through out the week, but once the track started getting faster we started getting slower. I think I know what I need to do, but I would like some input on the situation first. What do the two attached images show(Front tire wear), and what needs to be tuned to fix the problem? Times get slower as the race goes on, and Max RPMS also begin to decrease as the race goes on. From 14,200.. down to 13,700. My guess is the rear needs to be softened, drop the seat lower.. maybe move it forward. My other guess would be a stiffer chassis before too long. Any ideas would be greatly appreciated.

[Garry Lobaugh]

Call the office please and ask for garry. 269-756-9133 thanks

[Jim Holland]

To much grip in front. Widen the rear track and narrow the front. Lower tire pressure. Short hubs is correct. Med/Soft axel. Lower the front rde height. Leave the seat alone for now. lower the seat weights. Remove seat struts to loosen the rear if needed. Do not make all of these changes at one time. Make little changes and check the lap times. We had the AR28 and found success in the changes I have listed. Not all changes work at certain tracks so do some testing and take notes on every change made during the day.

Jim Holland

[Garry Lobaugh]

Hello AJ,
There are a couple of things to consider here and I will list them in order of how I would change them. These are only my opinions...

The M axle is a bit too rigid for the 100cc categories. It is a good all around axle and performs well on a "green" track. However, when the ruberstarts to come down, it will definitely put you in a bind. I normally run either F3 or F2.5 axles almost all the time in the KT100 classes. THe rear ride height will make a big difference in the Jr. categories as well, especially on DBS tires. When the rubbercomes down I would suggest raising the axle to take some of the bite off the rear of the kart.

In order to help the kart work (lift the inside tire) in the lower horsepower categories it is necessary to add castor (tip the kingpin back toward the driver). I normally run at least 1.5 degrees in the KT classes and as much as 3 degrees. This will also help with the excessive front tire wear.

Finally, it seems that the seat might be a bit too far back. I would have the seat set more like 58.5 on the left side and 59.5 on the right side.

Again, these are only my opinions, I would definitely take Mr. Holland's advise and change one thing at a time.