Youth ATV suspension upgrade: Phase 1

May. 01, 2004 By
Most of the Asian manufacturers have done a commendable job balancing reliability with performance and have ended up providing us with fairly meek, mild mannered mini quads. But as our kids grow, inevitably the first thing they ask for is more speed, and Kids Korner followed the tried and true process of bolting on the essential motor goodies. With those parts we successfully affected a significant improvement in the engine power of our project mini-quad, but unfortunately built a machine with almost too much motor for the chassis.  Certainly for racing intentions some suspension and chassis enhancements are in line, but most of the mods we'll be looking at apply to both youth riders that have developed in skill but even the novice rider. These modifications ought to be considered by the latter simply because they can make the machine safer- more stable in corners, more controllable in the rough, and more predictable over jumps. The goal of our first phase is to simply widen the machine. Common intuition will tell you that wider is better for purposes of lateral stability- it's simply harder to tip the machine over. The negatives are very few and almost not worth mentioning: slightly more weight, theoretically a bit less straight line stability, and higher stress on certain components. The reality is that most youth quads could stand to be a bit wider right from the factory. To actually make the ATV wider is quite simple, and there's a few approaches to accomplishing this, varying in complexity, expense, and ultimate machine performance.

Wheel Spacers The most common method is to install wheel spacers that fit between the wheel hub and wheel. These are typically CNC machined billet aluminum and either include longer bolts to sandwich the spacer between the wheel and hub, or separate studs to mount the wheels. 

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DMI Racing billet aluminum wheel spacers.
DMI Racing manufactures these spacers for a number of common full-size quads as well as minis. They are beautifully machined 6061 aluminum spacers with large reliefs in the four corners to minimize the weight. They stock them in a 2" width for the minis, but can make them whatever size you may need.  A set of two will run about $106.95, or 4 for $199- significantly less expensive than the other options considered in this article.  Installation is a breeze- not coincidentally about as easy as changing your tires. However, the shock preload needs to be increased (and hopefully there's adjustment left!) since you've effectively increased the length of the control arm (the same vehicle weight is acting on a longer lever arm). The downsides to this approach are the following:
  • additional unsprung weight at each corner- each spacer weighs just under 2 lbs. This makes the shocks work harder, and the suspension less capable of keeping the tire in contact with the ground through rough terrain.
  • increased stress on the stock kingpin (spindle); this might be an issue for heavier rider and/or aggressive riders.
  • increased 'scrub radius', which is the theoretical radius drawn from the front wheel spindle centerline (where the wheel pivots) and the contact patch of the tire. This is significant from the standpoint that forces acting on a front tire such as bumps and braking tend to push it backward/outward. This is felt directly by the rider through the handlebars and can be difficult to manage for younger riders. Some call the machine twitchy or nervous with this condition.
The upsides to wheel spacers:
  • inexpensive option compared to wider axles and longer a-arms
  • easy installation
  • easy to modify configuration from wider to narrower, or back to stock

A-arms The "downtown" method of widening the machine is by replacing your stock hardware with specialized, racing-intent componentry. Installation of new A-arms falls into this category. A number of companies sell mini-quad A-arms, but given the numerous designs of quads out there, be sure to check that the A-arms you're purchasing are a direct fit into your machine and require no welding or shock relocation.

A comparison of stock and Hetrick Racing A-arms for Kasea quads
The A-arms purchased for our phase I upgrade came from Hetrick Racing and are specifically designed for Kasea and LRX quads which have the 'double-clevis' style spindle. These arms come in two varieties: "+2" and "+3", which corresponds to the extra width (inches) per side. The Hetrick A-arms are very nice pieces, and come in a gloss black powder coat finish. For additional wheelbase, some other suppliers have A-arms that additionally bring the spindle more forward, thus increasing the wheelbase by an inch or so. Installation of A-arms is not difficult at all for the weekend mechanic. Unbolt the old stuff, replace or reuse the bushings, install the A-arms, install new tire rods (longer to accommodate the extra track width), and adjust the toe (front wheel alignment). About a 1 hour job. The advantages of installing wider A-arms
  • typically, a stronger design (and less stress on the spindle)
  • possibly additional wheelbase (+1" usually), which can make the machine less twitchy and have better straight line stability
  • no change in scrub radius means less twitchiness
  • light weight
  • the ability to go a full 3" per side
The disadvantages are:
  • about 3x pricier than spacers
  • may require new shocks (stay tuned for stage 2!) if the shock perch location is different than stock
  • more time intensive to install

Wider Axles Most youth racers that are getting big air and hitting whoops hard run wider axles rather than spacers for the simple reason that the stock axle just wasn't made to take the abuse that a fully modified mini-quad can dish out. It's not uncommon at all to see a snapped axle on a mini-quad due to excessive stress caused by the sudden impact of slightly cock-eyed landing. Obviously this may cause a lost race, but more importantly can cause serious injury to the rider. Unfortunately, not many of the axle manufacturers have caught on to the mini quad racing scene yet. One of the biggies has- Durablue. At this time they only offer an axle for the Kasea, a +4 (total) Eliminator. At $406 it's not cheap but it's warranteed for life (for the original purchaser). With incredible strength, and a polished and chromed outside, they are considered the world's #1 axle.   >>>> Next Month- we venture into high performance shocks. Newsletter
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