Weight Distribution/Center of Gravity

Many consider the overall weight of the bicycle when it comes to performance, but what about where this weight is on the bicycle? A bicycle with a lower center of gravity is more stable (just like in martial arts! You're harder to tip over). In general though, geometry and rider position play bigger roles in stability.

The fore-aft weight distribution of the bicycle does not simply affect stability like the verticle weight distribution mentioned above. It also affects control both on the trail and off (when airborne). If the center of gravity of the bicycle is too far forward, the bicycle will tend to rotate nosefirst into the ground. If the center of gravity of the bicycle is too far backwards, the bicycle tend to rotate upwards, causing a loop out.

Having the center of gravity at 50% of the wheelbase is the average. Trials riders who do alot of rear wheel riding usually have a center of gravity that is much more so to the rear (35%-50% of wheelbase from rearhub) Some cross country bicycle setups have the center of gravity much more forward, being infront of the 50% wheelbase mark. This keeps the front wheel on the ground for better traction especially on hills. The disadvantage of having a center of gravity that far forward is that descending control is compromised. Bunnyhopping and other techniques that require lifting or unweighting the front wheel become more difficult as well.

Having the center of gravity very far backwards allows unweighting the front wheel to be done very easily. It does not help with bunnyhopping though as the rear is much more difficult to rotate into the air after the front is lifted. Climbing is compromised as well, since the weight distribution makes keeping the front wheel grounded much more difficult.

Personally, my bicycle is setup with the center of gravity at 46-48% of wheelbase from the rear. Having the center of gravity slightly behind the 50% mark allows me to have an advantage when it comes to unweighting the front wheel. It is slightly easier to rollover large jutting objects like roots and rocks. Bunnyhopping is much easier as well.

As stated earlier, geometry and rider position are the dominant factors affecting stability. All the above mentioned ideas contribute very, very little of the full effect of rotational/fore-aft/lateral stability (the bike weighs about 27 lb, the rider weighs about 160 lb, so we can guestimate that the weight of the bike contributes less than 15% of the effect on stability, even lower if you're more than 160 lb).

May 11, 2004

Top Previous Next