I just bought my first real MTB. Its a TREK 4500 and I love it so far. I've had it for 2 days. I was out riding the today and noticed that when going up incline i lost rear traction here and there. Is this a problem with posture, seating, etc ?


Is there a video online or a read that talks about proper posture etc for mountain bikes. I feel comfortable on it and the only pain I feel is on my knees, but thats because I generally have weak knees right now due to lack of running or any excercise in general.

Also, a trick my dad and I use in our big john Deer tractor is load the back wheels with water like 1/4 of the tire. Do people in the bike community do this? It would ad some weight to the back.

well how steep of an incline are we talking about here? It could be your tires, i dont know what your using for tires but if its slicks or anything without good knobs its much easier to lose traction on the rear. The idewa when climbing is to get weight on the front end, but you cant take that too far. THere is a balance that needs to be maintained, so that there is sitll some weight on the rear. YOur likely leaning forward too much. If your feeling pain in your knees however, you may consider taking the bike to the shop and asking them to help fit you.

Thats a good way of saying it
You should not need water in the rear tire anyways. Plus it would make an irritating sloshy sound

What tire pressure are you running? When climbing, and coming up to a root, I usually hover very close to my seat so when you hit the root the rear end of the bike stays down... sitting on the nose of the saddle while climbing usually works out pretty well too.

Yes, do tell! Just a few psi of tire pressure can make a huge difference in specific situations, usually steep, dry hardpack.

But of course learning to make small, quick adjustments to your center of gravity to shift weight on and off your rear tire is even more critical. And lastly, just having the legs to keep the momentum going is often what's going to keep you rolling through something steep and technical.

I think butt forward helps. You want your center of mass over the point where the rear tire tread contacts the ground. In general: climbing, weight slightly forward; descending weight slightly back.

A slight change in tire pressure can also make a difference. If you need more traction, lower the pressure - not so low that you get snakebit (pinch flat).

Draw a picture of a biker on bike. Rotate the picture so the person is climbing, and you can see that the weight of the rider is behind the contact patch of the rear wheel -> not as much downward force is being applied to the trail -> less traction.

What kind of hill? Hard packed, sandy, wet n' sandy, mud, almost mud? Type of tires? width? On really sandy or loose singletrack beat up hills with roots and nooks I almost always loose SOME traction. Shifting back on the seat...more weight over the wheel and I'm usually fine. Sometimes I spin the rear wheel all the way up and shifting weight makes no difference. But I crest the hill so whatever, its ok.

Not to start a flame, but you guys sayin "weight back" are crazy. Draw pictures. Work out the forces.

I agree - it's all about balancing your weight (and that of your bike) in the right spot. Too much forward - slippage. Too much back - slippage or wheelie.

Sometimes slipping is inevitable, given a grade, surface, weight, tire contact area, and tread.

Yup!

Right, i'd say you want to get fairly far forward, but keep a steady lift on the handlebars, this makes it so your body is forward, yet the back tire is weighed as much as possible.
I didn't see anyone say however that you should lean back or keep your butt over the seat, wording is tricky sometimes so no one here is crazy.

You lose traction on a hill when the horizontal shear force generated by the rear tyre exceeds the shear strength of the ground.
Imagine the ground as a series of layers that can slide against each other. The tyre grips the top layer but that layer slides against the lower layer.
There are two ways to approach the problem:
1. Grab more layers of ground. A narrower tyre will bite deeper than a fat one which rests on the surface layer.
2. Reduce the shear force by reducing your pedaling force or climbing in a higher gear. You cant always use max force; modulate the force that you apply to the pedals and reduce it as soon as you feel the wheel start to lose traction.

If you have ever tried to start a car on an icy surface you will know that you should use a higher gear to stop the wheels spinning.

Weight distribution is important. You need as much weight as possible on the rear but if you have too much, the front wheel will tend to rise on steep slopes. A lower stem may help to avoid front wheel rise and let you put more weight back. You will have to experiment with moving your body around on the bike.

There are a few things you can do to maintain good traction going uphill.
First sit back on the saddle and spin. Keep your upper body relaxed and concentrate
on a smooth steady climb. If you need to get out of the saddle to accelerate, do not
overgear. It' the bigger gears that make you skid. Use a higher cadence.
In cycling we strive for "weight loss" and adding weight to anything will only slow you
down. By learning how to shift your weight for each situation you will find yourself
doing better over any terrain:-)

You have to shift your weight constantly to find the right balance between traction and going over backwards. Ned Overend's Book and his video are excellent sources for learing mountain bike technique. I've done some experimenting with tires for climbing the steep ones in the N Georgia and Tenn Mountains.

The Ritchie Excavader (WC) just doesn't slip with reasonable technique.

Al