Downhill turns

[funsocaltiger]

First off, I live in a real hilly area, so avoiding hills is completely out of the question. Having a current top speed of only like 50mph, I already have mastered the art of starting the bike from a stop facing uphill.

Anyway, yesterday when I was riding around the neighborhood I found a few relatively steep downhills and I got pretty freaked out. On one downhill I slowed all the way down to 20mph before entering the turn. And I just felt so unstable all the way through. Luckily the speed limit there was 25mph (residential) but cars often fly through there at 40-50mph regardless.

I guess my question is...

Is there any real reason why taking a curve downhill should really be any more dangerous than uphill or straight? I took the same curve back uphill at 45mph. So is it all psychological? It just feels like my lean angle is so much steeper going downhill and I worry about going too fast since you're theoretically supposed to be accelerating into all turns.

[ronboskz650sr]

Yes, there is a reason. The load on the front end makes you tend to run wide, so early off the front brake as you enter the turn and very light trail braking (with the rear brake, in this case) help stabilize the chassis. You need to push the bar hard enough to compensate for the extra weight on the front, to tighten the turn. And you still need to accelerate to unload the front for the exit. That was all a fancy way of saying "practice these things at progressively higher speeds until you figure it out, and are comfortable." Don't worry about the lower speeds at first...this takes practice.

[funsocaltiger]

The load on the front end makes you tend to run wide, so early off the front brake as you enter the turn and very light trail braking (with the rear brake, in this case) help stabilize the chassis. ... And you still need to accelerate to unload the front for the exit.

Alright so for clarification... you mean trail brake entering into the turn but not during the turn, correct?

Also, unfortunately the particular turn (well, curve, really) Im thinking of was pretty long (like 1/4 mile) but it was pretty wide so steering wasnt the main issue. Just a little scary having to slowly accelerate through the entire thing more or less when I already felt unstable. I basically just went inside the curve and then straightened up and hit the brakes to manage my speed periodically. Would have really sucked if a car was behind me, though.

[Lion_Lady]

Downhill curves are creepy... I find that if the hill isn't too steep I can manage speed by slowing as much as possible BEFORE the turn, including downshifting.

Other than that stay OFF the front brake through the curve. Using your rear brake actually stabilizes the bike at lower speeds.

P

[blair]

Outside-cambered turns are tougher because for the same lean you get less turn of the wheel. Gravity is still pulling straight down, but the perpendicular force from the road surface is not pushing straight up, so there's less of it, and the wheel doesn't go to the same dihedral angle as it would on a flat. And because of the outside camber, you need more than the usual dihedral angle anyway to keep the line around the turn. So the two effects add and you're wondering how much countersteer you have to force into this thing to get it to turn. And any error is amplified, so it feels a lot less stable. Plus you can sense that the perpendicular force, which determines wheel/road friction, is lower, and you can tell you're going to low-side at a much lower speed.

Inside-cambered turns are "easier" because they help you turn with less than normal wheel-turn, but not because of gravity, just because the road is curving the direction you are. In this case the gravity effect is the same as in the outside-cambered turn, but in this case it's the opposite of the effect of the dihedral deviation. So it seems more like a flat-road turn, with less dihedral, but still stable.

These are my observations, at least. Digging into the math might find situations where they don't hold true. But that kind of math, even in experienced hands, takes a lot of work to crank through. And I'm not up for that kind of brain-fry on a Sunday afternoon this close to August...

[ronboskz650sr]

You can trail brake in the turn, using the rear brake...while applying throttle. Like I said, it takes practice...there's more to do on a downhill curve. Still, stabilizing the chassis in the turn is key, and a combination of rear brake and throttle really does the trick without causing a nose-dive like the front brake might going downhill. Using the right combination of front and rear brake before corner entry is important, too, as this sets your entry speed and determines what the lean angle will be, until something else changes. In my opinion, you should keep the front brake applied lightly until just after you begin the turn, but if you are uncomfortable, it's best to set the chassis with a power setting appropriate to the speed and gear you're in, and turn in with no other inputs to change. Sort of coasting under power until you apply more for corner exit. Whatever you do, don't coast with the clutch in! Relax and take it a little at a time. If you have just reached a 50 mph personal best speed, a 20 mph turn is already a challenge. Don't worry about it. Ride your own ride. Things will speed up in time, as you get comfortable. BTW, make sure your bike is up to snuff, too! Fork seals okay? Fork oil need changing? Rear shocks okay? ETC....

[Sev]

We should keep in mind, as always, that to much force on the back wheel will lock it which leads to all sorts of unpleasant events. It doesn't take a lot to keep that back wheel stable.

[Loonette]

Downhill curves still freak me out a bit, especially on roads that are new to me. I've never used the rear brake, but I do slow down a bit and usually will downshift. More and more practice makes it much less nerve wrecking. Eventually you'll enjoy the challenge of finding the perfect mix for you and your bike to master those types of curves. Just keep practicing.

Cheers,
Loonette

[Randy]

A lot of excellent advice, and I would like to point out that Blair is about three for for times smarter than me and my dog put together.

[sapaul]

Followers of the pace(not the force) will tell you that your entry speed and correct counter steering will determine the comfort of the corner. On my first ever fast track day I had a fast downhill right hander that I just could not get right, an instructer followed me and gave me the following advice. My entry speed was too fast, brake, clutch, gear down and get off brakes early. My right elbow was too stiff and I was not counter steering properly, push harder, tuck elbow in. My body position was wrong, was told to get my pelvis closer to the tank and to hug the tank with my knees, also to push on the right footpeg. Look for just before the apex and apply power gently so the chassis stiffens. Before this advice my heart was beating faster coming out of the turn than going in. After the advice I scraped the front of my boots without batting an eye, it just felt so right. On the same corner same day, another rider took a tumble. He was given the same advice but panicked in the corner, stood the bike up which then went straight and he ended up in the bales. One thing I do know is that counter steering works for me and I have never had my bike over so far as to scrape the hero pegs. See if you can find an experianced friend to follow you down this hill and maybe he can see if there is anything really wrong or maybe you just need to practice more.