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Issue 168 (November 2009) - Words: Jeff Eveleigh It becomes very difficult to discuss forward grip on its own because, other than with a starting grid, it is almost always a component of corner exit. That being said, we're going to break down and explain how to adjust for forward grip within your chassis. Much of this article will tackle physics and theories, but remember that there are so many factors to chassis setup that no amount of theory beats good old track time So, learn how your vehicle is supposed to react to certain changes, and then go try some of them yourself to see how they work with your setup, driving style and track conditions.
Another major factor of tread design that affects forward grip is the density of the spikes in the center of the tire. Tires such as Pro-Line's Revolver and Caliber pay more attention to the center treads. As the tire expands under heavy acceleration, the only contact patch is that of the center spikes. More center spikes offer more forward grip, and longer tire wear when your finger is heavy on the throttle. Also keep in mind that any tire tread choices that increase forward grip will also greatly increase your vehicle's braking ability in the forward direction.
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Tires
should be the largest single factor when it comes to any traction
consideration. This holds true for forward grip as well. Given that
tires are so important, we snagged ourselves an expert to interrogate:
pro driver Scott Hughes of Pro-Line fame sat down with us for a bit
and chatted rubber, tread, traction and gazebos!
TRACTION
CONTROL
The
inserts used within your tires will not affect handling as drastically
as tire or tread design, but they still play a role in forward grip.
When it comes to off-road racing, a softer insert will give you better
side bite, while a firmer insert will increase forward grip. A firmer
insert helps to maintain tire shape integrity more closely under heavy
acceleration, allowing the tires design to do its job. A softer insert
allows more pin flex, which would reduce contact in a straight line
and reduce forward-grip slightly. The opposite holds true for on-road
inserts. A firmer insert will help prevent your tire from rolling over
while side-loaded—increasing side-grip, while a softer insert will
increase forward-grip.
Adjusting
rear toe angles is one of the quickest, easiest and most reliable
forms of increasing rear traction almost everywhere on the racetrack.
If you need a bump in forward grip, then try adding 0.5 to 1 degree of
toe-in at the rear of your car. You'll be able to accelerate harder
out of a turn with the increased rear traction (but keep in mind that
increased rear toe-in will reduce your steering through pretty much
all phases of a corner).
When
it comes to weight transfer and forward traction, two of the most
common adjustments affecting front-to-back movement are droop and
anti-squat. When dealing with 4WD vehicles, the trick to increasing
forward-grip is to try and balance the power amongst all four driven
wheels. While under acceleration, your chassis wants to transfer
weight to the rear of the car, so adjustments need to be made to help
keep weight over the front-driven wheels to fully utilize their
traction-providing capabilities (and fully appreciate the advantages
of 4WD). When too much weight is transferred to the rear of the car
under acceleration, the front-driven tires can unload and spin,
reducing their pull in the forward direction. Reducing front droop or
increasing rear anti-squat will help to prevent so much weight
transfer to the rear of your car maximizing forward-grip.
The
opposite holds true for 2WD cars where the front wheels aren't driven.
To increase forward traction with this drive setup, you want to
transfer chassis weight over the rear tires to reduce wheel spin and
maximize forward grip. This is done by increasing the amount of front
droop, allowing the front end to rise up further during acceleration
and transfer more weight over the rear end. You can also increase
forward-grip in a 2WD vehicle by reducing anti-squat allowing the rear
suspension to settle more once you tag the throttle.
When
it comes to camber and forward grip, it all really comes down to tire
patch and surface area against the racing plane. The closer your camber
angles are to 0 degrees, the more forward grip your setup will offer.
Reducing camber to increase traction in a straight line isn't always the
best first move, since you will almost definitely lose grip throughout
the turn. Since camber is such a great tool for adjusting for side-grip,
there is usually another setup change that can be made to increase
forward grip without drastically affecting other aspects of handling.
Scott
Hughes needs no introduction, but we'll do it anyway. Pro-Line's front
man is also one of nitro off-road's fastest drivers and setup guys. With
multiple Worlds finishes and countless National podiums, this guy can
win on any given day at the racetrack. After hitting the track with his
Mugen MBX-6, here's what he uses to increase his buggy's forward grip.
Martin
Crisp is the author of the "XXX Main Racing Touring Chassis Setup
Guide" and he is known as a setup god! With multiple A-main
finishes at National events as well as Worlds qualifications, Martin
knows how to translate his setup ideas into results on the racetrack.
Here is the list of changes Martin makes when he wants to increase
forward-grip on his Tamiya Touring Car.
1st
- Tires - Softer tires offer more forward grip and less side bite. (And
softer inserts also offer more forward grip in an on-road car).
