Downhills

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Downhills

Postby Don Bolton » Wed Aug 20, 2008 11:31 am

For some of you this tour will feature a new twist... Loooooong downhills and there are a few things to keep in mind.

I have been composing an extensive narrative in spare moments regarding techniques, road types, cycle types, etc but its like a manual and nowhere ready for prime time. Soo a few lowlights :)

I'll focus the text on the standard diamond frame roadbike here as that accommodates the vast majority of riders. What we need to keep in mind here is that we spend countless hours developing techniques to power our bikes and spend very little time in downhill situations.

When we get on a downhill and just freewheel it may seem fast but fast as we may think we are others are faster. Recumbents with their low shape feature a reduced frontal area and cut through the winds with a vengeance. Tandems had sheer weight going for them. Both styles of bike are likely to come screaming by on some of the downhills.

For this reason one should keep right except when passing (or avoiding surface deviations) and USE YOUR MIRROR! I've experienced closing speed differences in excess of 20 mph in some instances. Be alert.

If being to the right is "spooky" then maybe a slight speed reduction is in order. ALWAYS RIDE WITHIN YOUR COMFORT ZONE!

A standard bicycle is designed for ease of propulsion. Those big skinny wheels with high pressure tires reduce rolling resistance which makes your pedaling effort more efficient. The downside of this is that this reduces the surface to provide grip in lateral G force loads and transfer braking energy to the road.

Further, the bicycle is given an very high center of gravity well above it's axle centerline. So it's top heavy, doesn't feature a lot of lateral grip, and doesn't provide for fast efficient braking. And oh yeah, those racing style frames also feature a geometry for quick steering that may lead to speed wobbles on steeper > 7% downhills at the (truly) higher speeds.

In cornering the bike can be leaned into the corner somewhat. In order to effectively lower the weight mass stand off the seat slightly with all your weight on the high side pedal in the down position. (this would be the pedal facing the outside of the cornering direction) This presses the focus of your body weight down onto the leaning bike below the axle centerline and allows for a steeper cornering angle.

Speed wobbles occur when your body weight is transfered too far forward relative to the speed you are traveling. The wisdom of being in the drops reducing the frontal area places your body weight forward and at excessive speeds and angles of descent a wobble can set in.

There are some riders who feel clamping the top tube with your legs will quiet this. What I've seen is that you start wobbling too and the end result may not be pretty.

Ease your weight back and ease on the brakes till the wobble subsides somewhat at which point you can raise out of the drops and ease your weight back further till it stops the wobble. Relax your grip doing this. The spinning wheels provide a form of gyroscopic effect it will subside if you let it. Using a "death grip" only serves to amplify the instability.

I descend smooth wide sweeping cornered downhills in the aero bars (I've touched 55 mph in this position). On steeper grades with tighter corners I move to the hoods where I can position my body weight fore/aft at will with little effort.

The downside to this on hood position is braking. You can't clamp with as much force as when in the drops. With exercising focused on increasing wrist and grip strength one can develop the strength but you cannot sustain it for long durations without discomfort. Since I really cannot reach the levers from the drops I cannot vouch for how my wrists might feel using that approach however. Might be the same.

If you just feel you must not go fast at all on the hill alternate between the front and back brakes to allow rims to remain cool while sustaining long duration braking forces. Excessive braking can overheat the rim which transfers to the air in the tube. Air expands under heat and it is possible to have a tube explode.

Another possible negative effect of sustained continuous braking is that the brake pads could overheat and "glaze" over and provide little stopping resistance when you really need it.

If you feel you need to maintain continuous braking alternate between the front and rear giving one time to cool while the other works...

Normal down hilling means braking on corner approach and freewheeling through up to the next corner. How much braking is required depends on speed, angle of descent, and sharpness of the corner.

Normally you enter the corner wide, drop to its (or your lanes) inside edge about 2/3 of the way through and ride back out to the edge on exit (a textbook fast line). This line however is likely compromised by road surface deviations in many places.

As vehicles brake for the corners the tires transfer energy to the road. Add in the additional loads of cornering weight transfer and many corner entry points have developed pot holes and or gravel. This is normal wear and tear and needs to be watched for as you approach the corner so you can adjust your line to enter on smoother pavement inside the optimal turn in point.

You need to look as far ahead as possible, focus on where you want to go (you end up steering where you are looking so don't look at the cliff look at the line you wish to traverse). Keep an eye open for upcoming possible side intrusions (deer, red necks in turbo diesel pickups, etc) possibilities and plan your line/speed accordingly.

A common mistake riders and vehicle operators make is focusing in too close. What happens is when you encounter an obstacle your response needs to be excessive and you don't have much time to respond. By looking farther ahead you've seen the obstacle sooner, adjusted your line earlier and more smoothly to avoid it.

Look where you are going, feel where you are.

Other riders serve as early warning systems too. By watching the riders up ahead you will note when they seemingly do something abnormal, (slow suddenly, scatter about, start shouting) and you can slow down earlier in response.

And finally, braking distances vary by road conditions, speed, weight, and descent angle. On a 5 or 6% downgrade one has pretty efficient braking from speed. When the descent angle gets steeper the braking distance extends greatly. Practice mid hill stops if you can before the tour and feel what the effort is. There have been times when they have stopped us mid hill for a safety concern. Its nice to know when you toss the anchor you will stop where you expect to.

Brett Flemming of the Bike Gallery will host some evening riding demonstrations as well as basic mechanic things. His demonstration of braking is worth seeing if you haven't.

Nearly all of your stopping power is in the front brake. Being thats on the wheel that steers this means really feeling whats going on so you don't scrub the wheel out from under you while cornering. You can brake aggressively in corners but its a developed technique and not for most.

And now really finally... If it rains lean angles go away. watch the upcoming road surface for spots that look slick. If its wet, and its shiny smooth looking it's a safe bet it's slippery. Rougher surfaces tend to disperse the water better and provide some grip. Adjust your speeds accordingly.

Last time we went from Halfway to Joseph it was wet (and COLD). The road for the most part had a rougher surface and I rode fast and hard except this one section for about 1/4 mile that was really smooth looking. TIPTOE...

In dry conditions the smooth parts have better grip go figure.

I spent my youth and younger adult years racing off road motorcycles and my favorite was open course cross country events. Attacking an unknown downhill has the same appeal to me. I'm not normal in this regard I know but WOW is it fun!

Ride within your limits, be confident, inform riders you are passing that you are there, and keep an eye out for the seemingly crazy riders rushing up from behind.

With a 10 mph or greater closing speed "On Your Left" is "ON" and your are past. I abbreviate under these conditions to a loud half crazed sounding "LEFT!" Seems to work.

Have fun and be safe.

Don "only a little crazy honest" Bolton
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Postby Force 5 Robert » Wed Aug 20, 2008 11:45 am

Don,

GREAT summary!! I would add to that (for road bikes) that be careful of your grip strength and pull over and rest if your grip is getting tired.

Recumbents need to yell loudly as we will likely be moving at a very quick pace. When closing so quickly bells, etc don't do it anymore. For sure though - whatever the speed limit is on a downhill some will be exceeding it. :D

:shock:

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Postby aktiv » Wed Aug 20, 2008 12:29 pm

These are great pointers Don and thanks for doing this. I do need to put in my experience:

First of all, speed wobble is extremely rare for the most of us, but it is good to be prepared should it ever happen. Second, I'll have to politely disagree with the assessment on clamping the top tube - it's saved my bacon down winding 8% grades more than once. Doing so "mass loads" the bike to the point that the shimmy is much more manageable. Third, it's been my experience that steady braking only increases the amplitude (strength) of the wobble; I had better luck with short, hard, a rhythmic stabs at the brake.

Don't let this scare any of you - this happens to very few riders. As Don stated, the main point with enjoyable downhilling is to relax. Bring yourself up off the seat an inch or so, use your brakes to control your speed rather than for panic stops, use your legs as springs to soak up bumps, and shift your weight (rather than turn the front wheel) in order to steer the bike.

If I remember right, the downhills on this year's course aren't anything wild (as opposed to descending from the top of Crater Lake), but they're all very very fun. Enjoy!

Cheers

Keith.
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Postby MarbleMtn » Wed Aug 20, 2008 12:37 pm

Thanks Don.

I am so sad Bridget and I will not be there with CO this year. (First grandchild due then).

Have the Bike Gallery folks check your brakes somethime and have fun on the downhills

Clyde
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Postby Don Bolton » Wed Aug 20, 2008 2:33 pm

Good to note your experiences.

I've been side by side with riders that have gone to wobble and they tried the top tube clamp method and ended up in a ditch. Its an interesting perspective being alongside a rider when this happens. I find myself checking their bike for damage to the wheels or such, slowing alongside them, watching the fall, feeling the pain.... Its one of those slow motion things.... Kind of cool in a sort of way.

As to the wobble and braking causing amplification. Easy gentle braking on the rear while sliding my weight back has worked for me every time.

My first road bike I bought based on stand over height. My gnome sized legs fit a 50cm frame (with a 52cm top tube). In order to have the proper top tube reach a longer stem 1.5cm longer was added which the fitter told me was putting 15% more weight forward. I could get it to wobble once in awhile but it was a sport touring frame and had more relaxed angles so not so bad normally. ( I ride a 54 cm frame now)

2 or 3 years back I switched saddles on my bikes. Wider with a different profile. I didn't have the pro's refit me so I was riding 1.5cm too high PLUS 1.5 cm too far forward ( I found out later).

Coming off Anthony lakes when I'd break 50 mph the bike started the wobble. Knowing what I know I just let it do it and no problem. Once the road leveled out some it went away. At first I did what I suggested and that worked fine. But hey then I was below 50 :cry: so I just let it shimmy. I'm sure that looked odd as I passed riders :? .

Anyway Your point about it being rare is important to note. Its got to be a steep slope and you have to be near the 50mph range before its a possibility so for most this is a non issue... Then factor in body mass and size, bike size, type, and fit, plus other factors and many things might result in a blissful resolution differently for different conditions..

Thanks for your input!

And Keith is quite right about this years descents. They are not overly technical and really, really fun if you just relax and enjoy them...

See you soon...

Oh and for the record. I own a turbo diesel pick up 8)

Don "speed wobble is not my middle name" Bolton

aktiv wrote:These are great pointers Don and thanks for doing this. I do need to put in my experience:

First of all, speed wobble is extremely rare for the most of us, but it is good to be prepared should it ever happen. Second, I'll have to politely disagree with the assessment on clamping the top tube - it's saved my bacon down winding 8% grades more than once. Doing so "mass loads" the bike to the point that the shimmy is much more manageable. Third, it's been my experience that steady braking only increases the amplitude (strength) of the wobble; I had better luck with short, hard, a rhythmic stabs at the brake.

Don't let this scare any of you - this happens to very few riders. As Don stated, the main point with enjoyable downhilling is to relax. Bring yourself up off the seat an inch or so, use your brakes to control your speed rather than for panic stops, use your legs as springs to soak up bumps, and shift your weight (rather than turn the front wheel) in order to steer the bike.

If I remember right, the downhills on this year's course aren't anything wild (as opposed to descending from the top of Crater Lake), but they're all very very fun. Enjoy!

Cheers

Keith.
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Postby Steve from Beavercreek » Wed Aug 20, 2008 2:52 pm

Hi Don. I experienced a wobble on the downhill from Anthony Lakes two years ago. I was going about 47 mph. It scared the the heck out of me. I thought that I had a defect in my bike. Now that you have explained it so well, I now understand how my weight was much too forward. I don't think that we will be having any comparable downhill on this year's ride. Thanks for the good advice!
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Postby grin4joy » Wed Aug 20, 2008 2:58 pm

Thanks guys for all the great information - it's gonna be so fun to see everyone!!
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Postby Red Zinger » Wed Aug 20, 2008 4:26 pm

A mild word of caution here, based on an experience unpleasant indeed! It seems sensible--hard though it might be--to keep speed well under control when you're riding in a group the size of Cycle Oregon. You'll be surrounded by other riders much of the time. Someone could fall or make a mistake and cause you to crash too. So being careful around other riders makes sense. I like to take the downhills with no one anywhere near me, but that's rarely possible!

:?
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Postby Udiboy » Wed Aug 20, 2008 4:42 pm

In Vermont, where the roads were built before the advent of modern road building codes, we have gaps (aka passes) where the grade can be upward of 12%. At least the climbs are shorter than out west. I find that it can help to REST one knee against the top top, which seems to break-up the harmonic wave of the "wooble". Clamping the tube with both knees or just riding in a ridged position makes it much more difficult to react to rapidly changing road conditions and is probably the worse thing you can do.

Bottom line, try to relax and slow down.

It is also worthwhile to note that having a big honking bag on the back of a road bike completely screws up the aerodynamics and makes road wobble a possibility. A few years back, on RTR, my buddy cured his wobble by moving the contents of his bike bag into his pockets and tossing the bag into the trash.
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Downhills

Postby wayneh » Wed Aug 20, 2008 7:01 pm

After doing a number of these great rides, I am firmly convinced that I love my skin intact, I like the way it covers and protects my body, and I don't relish the though of spreading it across the road due to excess speed and a lack of confidence dealing with it. I try to move my weight back, slightly off of the seat, and keep my speed under control, staying as much to the right as is realisitic. I do feel more confident locking my knees against the top bar but otherwise try to assume a balanced and calm position on the bike. Sometimes I do pass someone, simply yelling "LEFT!" as I approach. I find the speed-burners screaming by on my left sometimes more un-nerving than the descent itself. But the reality is, I don't come across these types of descents in normal training (who does?) so I respect gravity and do my best to arrive in camp intact.

Look down the road, anticipate your line, ride within your own ability, and pull over and rest if your hands cramp up or fatigue from too much braking. So far, so good.
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Postby grin4joy » Thu Aug 21, 2008 6:26 am

MarbleMtn, Sorry you and your wife won't be on the ride this year, but I think you have the best reason ever! My husband and I expect our 1st grandchild in November. Congratulations! :D
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Postby aktiv » Thu Aug 21, 2008 8:44 am

Easy gentle braking on the rear while sliding my weight back has worked for me every time.
Ooooh, good point on that. Let me amend my previous statement - front wheel braking will increase the amplitude of the wobble. I hadn't considered using just the rear brakes. Good on ya m8.

Keith.
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Postby Rox » Thu Aug 21, 2008 10:09 am

Remember that brakes heat up on hills. This can blow out a tire. Many CO's we have had someone blow a tire this way. The result is not pretty.

So on a steep downhill where you are braking a lot - stop and feel the rim with your hand. Sometimes it will burn you.

Take a break. Take some pictures. Let the rims cool for a few minutes.

If you blast through downhills you may not use the brakes enough that this is a problem. If you are cautious and brake a lot this will definitely be a problem!

Also, pay attention to your hands. We have had some BAD accidents caused by people with hands so tired they couldn't brake properly.

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Postby All about downhills » Fri Aug 22, 2008 11:56 am

For this reason one should keep right except when passing (or avoiding surface deviations)


Don't assume you will go faster than the people you passed going uphill.

I'm not that great of a climber, but I fly downhills and have passed tandems, etc. and people are surprised by how fast I go down, especially when they passed me a while ago on the up.

the downhills on this year's course aren't anything wild (as opposed to descending from the top of Crater Lake


Those were great downhills last year. I was able to get to 48 on one before I had to slow down due to a turn.

I can't wait to ride! 2 weeks left!!
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Postby Don Bolton » Fri Aug 22, 2008 12:56 pm

Precisely why I started the narrative.

Burrito dynamics go slow uphill but fly down.

Even in the pro ranks there are downhill specialists and most of the pack are not really good downhill riders.

There are just some riders that unexpectedly have the gift on the downhills.

Don "feel the rush" Bolton

All about downhills wrote:
For this reason one should keep right except when passing (or avoiding surface deviations)


Don't assume you will go faster than the people you passed going uphill.

I'm not that great of a climber, but I fly downhills and have passed tandems, etc. and people are surprised by how fast I go down, especially when they passed me a while ago on the up.

the downhills on this year's course aren't anything wild (as opposed to descending from the top of Crater Lake


Those were great downhills last year. I was able to get to 48 on one before I had to slow down due to a turn.

I can't wait to ride! 2 weeks left!!
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