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There is this trail around my location. Half of it is a rock garden. The stones are similar to the picture below.

The elevation is not extreme - one can ride uphill, at the lowest gear.

My bike has 160mm front and rear travel. It actually goes over any of the stones without help from my side :)

Here is my problem. When I try to descent over them (at some speed) there are times, when the front tire "steps" on the side of a stone, then slides down (and because, unlike the picture, the stones are watermelon-shaped, this is easy, there is no flat "top" to step on).

Because the rear end is moving forward, this attempts to turn my handlebars to the side and throw me from the bike. Both times this happened, I regained control, but the look of the "landing", should I fail the third time, discouraged me from descending at joyful speed.

It doesn't look really difficult, the stones are arranged at a flat pathway, and the slope angle is not steep at all. What should I do to learn to handle those front tire slips on the side of a rock? Or how should I prevent them? enter image description here

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I think you need a Pugsley. –  Daniel R Hicks Nov 17 '13 at 20:02
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Jahaziel's answer on this question doesn't get much better: bicycles.stackexchange.com/questions/9790/… The key things to be prepared for rock gardens is: attack position, keep looking forward to choose a line (not watching the front wheel, keep on reminding yourself), keeping your body loose, being in a high gear that will allow you to push against the pedals (if needed) and lots of momentum. Also practice heaps!! –  DWGKNZ Nov 17 '13 at 20:39
    
@DWGKNZ Vorac participated in that thread, so I suspect he needs more than that. –  andy256 Nov 18 '13 at 2:47
    
You mention watermelon size rocks but the photo shows baby head size rocks (and even smaller). Which one is it? –  cherouvim Nov 18 '13 at 7:52
    
@cherouvim, watermelons come in all sizes, from that of a tomato upwards. Anyway, most are about 20cm in diameter. –  Vorac Nov 18 '13 at 8:22

3 Answers 3

up vote 4 down vote accepted

On the type of rockgarden described, you can:

  1. Reduce the slippage tendency by loosening your pressure on front brake. Let's put it this way: the stone surface provides you with little friction. In some circumstances, the friction is just enough to keep the tire rolling in line. Add the friction needed for braking and you overpass the available friction. The tire then will slide to wherever the sum of all other forces lead it.

  2. You can predict where the tire will go when it slips. It will usually go to the gap between two rocks. Thus it is useful to pick a line where you follow the natural trace given by those gaps.

  3. Ignore slippage. This is indeed is easier said than done, it sounds just weird, I know. The point is, if you pick a good line, specially a straight one, the inertia of your body mass is bigger than the one from your bike. This means that your body tends to go in a straight line, so even if your bike slips a few centimeters below you, it will not be enough to immediately tip you off the bike. You will have a fraction of time to react and return to the balance point. For this to work, your bod must be traveling in the direction of the line you have selected.

Finally, the general idea is to feel like you "float" over the rock garden, get used to the feel of the bike sweeping a couple of inches below you while keeping a good, firm but not stiff grip on the handlebars.

If you don't feel comfortable at certain speed, reduce it, and practice. Have patience. Sooner or later your speed will grow and you will master these sections. Also, with practice, your line selection abilities will improve, you will do it faster and find ways of sticking your front wheel in strategic points where it wont slip and those points will serve you to improve control, switch lines or change course. Remember: practice and patience.

On a side note: Did you ever as a kid played running and suddenly stiffening your feet so you slid on the floor for a couple of yards? You weren't afraid of such slippage right? Why? You already knew how to predict it, you actually enjoyed it, so relax and enjoy your gardens!

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First of all it is better to try to prevent such front wheel slips than having to react to them. That means in first place you should try to ride a line where you reduce the chance to hit a stone in a way that your wheel could slip sideways down. The following hints will serve a bit of both purposes – riding a smooth line and giving you a better reaction on such slips.

The overall principle is "Get ourself light on the bike!" The rougher the terrain gets the less hard should you clench on your bikes handles and pedals – unfortunately this is some kind of counterintuitive as normally if things get rough one gets more anxious and tries to control this by fastening ones grip.

So what do I mean by "getting light"?

Most important is getting your center of gravity a bit backwards to remove some pressure from the front wheel. It is quite complicated to exactly specify the amount as it depends a lot on your normal riding position and on how good your feeling for slight shifts of your center of gravity is. What certainly can be said is that "far back until your chest hits the saddle" is way too much, it should be more like "point your buttocks back a bit". This will already make your front wheel less prone to slipping as you don't force it downwards that hard anymore. If the front wheel slips this shifted position will prevent you from getting slingshot towards the front and loosing balance. And it will also give you the possibility to lift your front wheel over some stones that you otherwise maybe would hit at a bad angle such that your wheel might slip.

Furthermore don't get stiff in your legs, but remain flexible here. This will allow you to move and steer your bike under you without having to throw around your whole body from one side to the other with every slight turn. This way you can make your bike go slalom between the stones while keeping your body in a much more straight and stable motion above it. Also the heel-drop technique discussed here will be quite useful to keep control of the bike.

And last but not least: look forward and try to figure out a line where your front wheel can roll with as less contact to bigger obstacles as possible. Don't care too much about the back wheel, this will just roll behind and especially with 160mm of rear suspension it won't be too impressed by some stones.

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Disagree with blanket 'moving weight back'. The front needs enough weight to hold it in contact with gound. Many novice riders have poor body position (too upright, like they are riding a crusier down main street), so are unable to change balance and weight distribution, so they have too little weight on front most of the time. (We would need to see OP in action to know what correction is needed.) –  mattnz Nov 17 '13 at 19:58
    
@mattnz Agreed, just getting stuff all back as far as possible is a bad solution as well. I will clarify on this. –  Benedikt Bauer Nov 17 '13 at 20:24

when the front tire "steps" on the side of a stone, then slides down

Being able to experience and describe the above (on 20cm diameter rocks) means that you are going very slow. Speed is your best friend here. Maintain a relaxed and neutral attack position and let the 160mm bike of yours handle the terrain.

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