CRG JUNIOR 100CC Guide de dépannage télécharger pdf (Page 12)

Rear End Adjustments

The rear end adjustments include wheel hub length, track, rear ride height, axle stiffness, bearing

locations and seat struts. Changes to these settings are usually made when handling problems occur

on the exit of the corner.

Some have said that the entire kart should be regarded as a tuned spring. When you change the rear

axle stiffness, hub length or rear width, you’re actually tuning the spring’s “frequency”. You can “tune”

the frequency and alter how/when the inside rear wheel comes up on corner entry, holds through the

center of the corner and then sets back down on corner exit.

Wheel Hub Length:

CRG makes three different wheel hub lengths for their chassis. It’s highly recommended that a kart

racer purchase all three of these sizes, as they are the most commonly adjusted setting on the kart and

have a significant impact on chassis balance.

Think of the relation of the rear hubs to the axle and chassis as you would your hand to a pry-bar and

an object at the other end of the bar. If you hold the bar at the farthest end of the bar or hold it with less

of your hand, you will have less leverage. Rear hubs on the axle work in much the same way.

Longer hubs tend to provide more rear grip because the inside rear wheel will spend more time on the

track surface. So if the kart oversteers as it exits a corner, a longer hub may be desirable.

Short hubs are used when the kart understeers at the exit of the corner. If the driver runs out of track

surface as he/she exits the corner the kart has a “push” on exit. While it’s not the only possible

change, switching to shorter hubs will reduce grip at the rear and may be desirable in a situation like

this. The shorter hubs have a lower “frequency” and will allow the inside rear tire to stay off the track

surface longer, and the kart will have less grip on corner exit.

Overall choice of hub length should ultimately be based on how flat the tire is wearing. If the kart is

running little caster, a soft axle and generally feels good, but the rear tires are “coning” (the inside of the

tire is wearing faster than the flat or outside), decrease the rear width. If the problem persists, increase

the hub length or turn the bearing carriers facing out to support the axle end more.

Rear Track:

The general rule is to run the rear of the kart as wide as feasible, assuming the chassis is performing

well. For sprint racing in the US, most rules dictate a maximum rear track of either 52 or 55 inches.

Most CRG manufactured chassis are specifically designed for rules allowing a 55” rear track width.

Therefore, it is important to set the kart’s rear track to the maximum that the rules allow. Also, a wider

rear tread will provide a smoother ride.

There is an interrelationship between rising/falling grip and stability in the 52” to 55” range with

maximum grip in the 54” range. Smaller track width dimensions will provide more grip, but at the

expense of stability.

However, this adjustment is made as a last resort. The driver should change to short wheel hubs

before decreasing the rear track width narrower than 54-1/2”. If necessary, narrow the rear track in 1/8”

increments, as most chassis are very responsive to minor changes if the seat is in the correct position.

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CRG JUNIOR 100CC Guide de dépannage Page 12