To update...I now LOVE hills! You were right; time and practice has given me so much confidence!
Descending
- Thread starter sbayhylle
- Start date
So true. I would like to add something to that. I've been riding for 36 years and have hit speeds of 40 to 50 mph quite often. Thank goodness I've only had to high speed wobbles in all that time, but, both times it was terribly scary. That 2nd time was a couple of days ago. I was coming down Mt. Baldy Road around 40 mph when the front wheel started to wobble. I don't know what caused it but I was in trouble. I did use my brakes a bit, lightly, but it was no use. As the wobble continued I resigned myself to hitting the deck, but, I just barely got back on the bike after recuperating from broken and bruised ribs. As I contemplated the rocks on the side of the road and my speed I said to myself "I can't afford to hit the deck again". At that moment I recalled something I had read a long while ago, "to stop a high speed wobble" squeeze the top tube between your knees". As soon as I put my knees together with the top tube between them the wobble instantly ('Miraculously') stopped'! I cannot tell you how relieved and Happy I was at that moment. I sincerely hope my experience will be remembered and someday help someone out of the same predicament.
Glad you refreshed my memory on the knees to top tube thing.
I have descended Mt Baldy several times. That is one road you don't want to have the wobbles. Never happened to me but always good to get a refresher.
The dh section before the tunnels is pretty darn scary even on a steady run.
Sounds like a blast! But scary. I'll give the tube squeeze a try if I get in trouble like that
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What you need to do is put your weight back a little and relax and let the bike do what the bike wants to do.
The bike “wobbles” when you get in a repetitive cycle of it wanting to move left or right to center itself balance wise and you being too stiff and not letting it do that.
Piano hands. Rest your hands in the drops and keep your fingers relaxed.
One big thing that gets most cyclists is the inability to understand countersteering and using it to initiate turns. You can do it at any speed. Find a wide, quiet road that goes gently down hill that allows you to relax and prepare for the unexpected - except I’m going to tell you this so you will expect it. Go in a straight line with your hands preferably in the drops (brake levers are fine though) and press forwards gently with your left hand. You will go left - so don’t be too close to a kerb or similar. Why does it do this? Two wheeled things turn primarily by leaning. Pushing to turn initiates a lean very quickly. Once you’re in a turn push a little more to tighten the turn or less to straighten up. If you need to go straight in a hurry, push a little with the opposite hand.
Be relaxed when you do this.
When you learn this turning becomes more fluid and relaxed and much less scary.
Watch Fabian go. One of the best descenders out there back in the day.
View: https://youtu.be/RxXqQqAc2pA
Notice near the start of this he’s on the radio and the hand on the outside of the curve is on the radio. Similarly, towards the end the outside hand (this time is other hand) is getting some food from his pocket. That’s no coincidence that the hand on the inside is on the bars.
If you can learn to steer this way with just one hand you will be much much more comfortable on the bike. With one hand, push to turn in and increase the turn with the inside hand and pull to turn the other way. So with left hand - push to turn left, pull to go right.
With bicycles you can force it to turn incorrectly as they are so light but with something like a motorcycle, especially a sports bike that has slow steering, you have to use this countersteering to make the bike agile. This works on all two wheel things and is the very reason why learning to ride on two wheels is so difficult.
I'm not so sure about this. Certain bike properties makes it more likely to wobble so it's not entirely dependent on rider skill, knowledge, and experience. Sometimes, the bike is just more susceptible at high speed wobble even if it's absolutely 100% free of defect.
Certain bike properties, setup, or even fit / geometry makes it more susceptible to wobble. I actually did tests on this deliberately inducing a wobble and observing how long until wobble ceases on its own or if it wobbles at all. Among these factors are:
1. Location of the Center of Gravity (CG). Lower and closer to the front wheel makes the bike more resistant to wobble. Modern bikes tend to put your weight closer to the front wheel via steeper seat tube angle and that is good in terms of improving wobble resistance (unfortunately, some riders would find it less comfortable). Setting the saddle too high is fatally bad because it potentially injure your knees if you keep riding that way and raises your CG makes wobbling more likely. That also explains why descending on the drops is better as it helps lower your CG but there's another reason why the drops makes it less likely to wobble.
2. Length of stem and dropbar reach. Now this is funny. Using shorter stem and/or less dropbar reach will make your bike feel more twitchy or even feel less stable. But actually makes the bike more resistant to wobble. Takes getting use to and when you do, the bike doesn't feel twitchy anymore.
3. Overall lateral stiffness of the bike against the road involving the frame, fork, wheelset and even the tires. Stiffer is better. Having more lateral flex makes the bike more unpredictable in how it will behave in a wobble. The wheelset can make a big difference here. Wider rims against the tire width helps improve overall lateral stiffness significantly. Classically-designed steel bikes tend to have more lateral flex than modern CF or aluminum bikes save for the lightest frames for bikes that break UCI rule for min weight.
Ironically, Downhill MTBs seemed to be designed under such guidelines like having the seat and the CG of the rider closer to the front wheel and lower too with dropper post. Good lateral stiffness with wider frame and fork components and wide rims. Finally by having very short or even "negative stem". And DH MTBs are known to have very good resistance against wobble.
" I actually did tests on this deliberately inducing a wobble and observing how long until wobble ceases on its own or if it wobbles at all.'
This an interesting technical discussion . Could you tell us about the bike(s) used including make size weight wheels tire type your weight and height ect. Not that I doubt any of your post. I just want to look at the test conditions.
Knowing more about what bikes have wobbled with what riders ,quality of road surface and texture ect & how they were set up on the bike would be insightful. If I had read through correctly , it appears a smaller guy with lower COG might have less chance for HSW to occur? And /or is there a trend of bikes that might have this tendency ?
I'd been blessed with thousands of miles on my bikes decades back , had not experienced a HS wobble on my old steel or aluminum bikes in any of the casual rides or centuries
These days ,of the last 7 months returned to road cycling hadn't had my Scott speedster 60 much over 40MPH period. Just not that guy anymore , I'm brittle or so says the bone density scan.
So I would not be able to comment on whether that bike has or could suffer from HS wobble. I had a Trek frame way -way back was epoxy bonded aluminum tubes aluminum fork . Forgot the model #. The fork at front axle would appear to visibly flex quite a bit from riders perspective over rough roads at speed . But that never translated to a HS wobble at the bars .
I was planning on cycling Mt baldy when in So Cal next time and the reference in a post above got my attention. I might not go fast enough these days for HSW but would like to hear more about others occurrence of this.
This an interesting technical discussion . Could you tell us about the bike(s) used including make size weight wheels tire type your weight and height ect. Not that I doubt any of your post. I just want to look at the test conditions.
Knowing more about what bikes have wobbled with what riders ,quality of road surface and texture ect & how they were set up on the bike would be insightful. If I had read through correctly , it appears a smaller guy with lower COG might have less chance for HSW to occur? And /or is there a trend of bikes that might have this tendency ?
I'd been blessed with thousands of miles on my bikes decades back , had not experienced a HS wobble on my old steel or aluminum bikes in any of the casual rides or centuries
These days ,of the last 7 months returned to road cycling hadn't had my Scott speedster 60 much over 40MPH period. Just not that guy anymore , I'm brittle or so says the bone density scan.
So I would not be able to comment on whether that bike has or could suffer from HS wobble. I had a Trek frame way -way back was epoxy bonded aluminum tubes aluminum fork . Forgot the model #. The fork at front axle would appear to visibly flex quite a bit from riders perspective over rough roads at speed . But that never translated to a HS wobble at the bars .
I was planning on cycling Mt baldy when in So Cal next time and the reference in a post above got my attention. I might not go fast enough these days for HSW but would like to hear more about others occurrence of this.
Size 50 disc brake gravel bike (undersized for my 5'8" height) using 35mm 700c slick tread road/urban tires. It's one of those cheap generic Asian brands ~$400 that is just a step above the quality of department store bikes. The original wheel set had rim internal width of 17mm. Switching to wider 21mm internal rim width wheelset using the same tires significantly reduced wobbling triggered by front wheel disturbance during HS descent. The whole bike still possesses significant amount of lateral flex (if I try to press the pedal sideways with my foot while I'm off the bike and and holding it upright despite the laterally stiffer wheelset.
My weight is 128 lbs. Bike empty weight is 38 lbs. I suppose that gives me low CG which makes everything more resistant to HS wobble. I can still make the bike wobble at HS but this wobble always dampens itself and ceases completely in under 2 seconds. For me it's only a matter of making the wobble less intense and ceases quicker.
Riding conditions and wobble testing is almost entirely on paved roads. Poor quality, very bumpy road though so I bought myself a gravel bike so I can put wider, more comfortable tires in it. Not all kinds of road imperfections will cause a wobble. Potholes definitely won't cause a wobble unless its big enough and you hit it while riding one-handed. But assuming you're hitting bumps with both hands on the handlebar, letting your wheel fall into gaps and cracks that run parallel to the road can definitely trigger wheel wobble. Skinny wheels are quite susceptible while wide tires can remain unaffected. Losing traction even by a small bit while swerving around something can also trigger HS wobble royally. Even hitting just a tiny patch of sand or ice while swerving can be extreme risk for HS wobble so I would probably suggest to avoid swerving at all during HS descent. Just pay good attention to the road and very carefully plan your lines so you don't have to swerve for any bumps. That's one advantage of having wider tires is you can just probably safely sail through the bumps without swerving.
With the modifications I did like moving the seat forward, replacing seatpost with no offset, shorter stem. I've almost eliminated HS wobble even if I deliberately disturb the handlebar at HS. It can still wobble badly ofc, if you disturb the handlebar strong enough for the rear wheel to lose traction. But I wouldn't advise that as you're likely to crash if you did.
Moving forward of your seat during HS descent will also make the bike stable and more wobble resistant.......BUT if you slam the brakes hard in that position, you could tumble forward and crash this is why many riders move all the way back on their seat. It's a compromise position. Less stable but less likely to crash should you need to brake hard to slow down quickly.
Obviously, some of these modifications may not agree with your bike fit and may induce discomfort. It is always a compromise.
The source of HS wobble can also be from loose QR skewers or TA's and loose / faulty headset and wheel hub bearings. Worst case is a cracked frame. If your bike is 100% free of defects, and QR skewers are tight enough, you have already eliminated a large degree of HS wobble factor.
Thanks for the details lots provided there. !
Could you provide actual tire used pressure front and rear.
Im also a lightweight rider who has recently been experimenting with lower PSI depending on which bike and route.
Could you provide actual tire used pressure front and rear.
Im also a lightweight rider who has recently been experimenting with lower PSI depending on which bike and route.
YW! Tire pressure F/R is 38/45 psi for the 35mm wide tubed 700c tires. I've run it as low as 25/35 psi but started to worry about pinch flatting.
Recently running the tires at 45/55 psi. Made me a bit faster but feels a little more twitchy and more susceptible to HS wobble due to the reduced steering load (easier to disturb the front wheel). So it seems less pressure may reduce HS wobble however, rim width still has bigger influence on wobble.
I never really did except for those hairy tests where I'm deliberately disturbing the handlebar to try induce wobble during HS descent.
Now, I couldn't induce wobble at all due to changes to my bike fit and wheel. A comfortable and powerful bike fit to my needs is still my #1 priority. I'm simply fortunate the adjustments made also improved the bike's wobble resistance like moving the CG forward and reducing the stem length.
Long stems can make wobble more severe if you're holding the hoods while descending. It is safer to put your hands on the drops. This happens because the bike is trying to correct itself during a wobble or more accurately - overcorrecting. The farther your hands forward of the steerer tube, the stronger this over-correcting tendency. Putting your hands on the drops moves your hands back against the steerer tube and improves wobble resistance.
One of my favorite sayings is "you gotta pay to play.". This means that if you are going to go fast and take chances on a bicycle don't be surprised when you crash someday and end up disabled or dead.
One guy I worked with just barely survived a crash going fast downhill because he ruptured his spleen. A doctor in my town was going fast downhill and could not stop before running into a bus and he died.
There is one hill I go as fast as I can on where I live but it is clear of obstacles and the road is wide so if I did crash the chance is very low that I would go off the road and hit trees or rocks or an oncoming automobile. I have crashed going down big hills in the past and I do not want to do it again, so I go slow down big hills now, especially since I am in my 60s in age. The trick is to slow down when you get to the hill and stay slow all the way down it. Once you let your speed creep up going down a big hill it is exponentially harder to bring it back down or stop. I ride old bicycles with brakes that work on the rim, and one with a coaster hub that gets red-hot down big hills. Even with the most modern brakes money can buy, there is still the chance of mechanical failure in the all-important front brake, so ask yourself if you are willing to risk your life on that small mechanical device. Younger people heal up better than old people usually, but not all the time. I know one guy locally pretty well that lost one of his legs from the knee down when he was 18 in a cycle crash by hitting an automobile while going really fast.
Think about it..............
One guy I worked with just barely survived a crash going fast downhill because he ruptured his spleen. A doctor in my town was going fast downhill and could not stop before running into a bus and he died.
There is one hill I go as fast as I can on where I live but it is clear of obstacles and the road is wide so if I did crash the chance is very low that I would go off the road and hit trees or rocks or an oncoming automobile. I have crashed going down big hills in the past and I do not want to do it again, so I go slow down big hills now, especially since I am in my 60s in age. The trick is to slow down when you get to the hill and stay slow all the way down it. Once you let your speed creep up going down a big hill it is exponentially harder to bring it back down or stop. I ride old bicycles with brakes that work on the rim, and one with a coaster hub that gets red-hot down big hills. Even with the most modern brakes money can buy, there is still the chance of mechanical failure in the all-important front brake, so ask yourself if you are willing to risk your life on that small mechanical device. Younger people heal up better than old people usually, but not all the time. I know one guy locally pretty well that lost one of his legs from the knee down when he was 18 in a cycle crash by hitting an automobile while going really fast.
Think about it..............
I agree with you and avoid steep descents if I can and take another route where the descent is less steep even if farther away.
Fortunately, I don't have to drag my brakes all the way down. My bike fit is relatively upright and I'm pretty light. I can keep myself getting too fast on descents simply by sitting more upright, in a position that creates a lot of drag in the wind.
Dragging the brakes on the way down is only ok if you're descending slow. At higher speeds and/or steep descents, you could overheat the brakes or even explode the rim/tires if on rim brakes.
Incredibly steep descents is the only time I drag the brakes all the way down at slow speeds. Because if I don't use the brakes, I'll be hitting 60 mph. If I had to slow down for anything going fast on a very steep descent, the very steep gradient might cause me to tumble forward and crash. I avoid those routes if I can. Before disc brakes, I had to get off the bike and just walk the bike downhill while still pressing the brake levers for really steep descents!
Some of you probably watched GCN how to brake on high speed descent and avoid tumbling forward, they advice scooting back on the seat.. It doesn't always work, and it won't work on really steep descents!
Hey there! I completely understand your concern about steep descents while cycling. It's always important to prioritize safety on the road. Taking a different route with a less steep descent sounds like a smart move to me, even if it means going a bit farther. It's better to be safe than sorry!
I appreciate your insight about bike fit as well. Being in a more upright position can definitely help control your speed on descents. And creating drag in the wind is a clever technique to prevent yourself from going too fast. Safety first, right?
I completely agree with you that dragging the brakes on a steep descent can lead to overheating or other issues. It's crucial to find the right balance between speed and control.
Thanks for sharing your thoughts on this topic. It's always great to hear from fellow cyclists who prioritize safety and enjoy the ride. Keep pedaling and stay safe out there!
I appreciate your insight about bike fit as well. Being in a more upright position can definitely help control your speed on descents. And creating drag in the wind is a clever technique to prevent yourself from going too fast. Safety first, right?
I completely agree with you that dragging the brakes on a steep descent can lead to overheating or other issues. It's crucial to find the right balance between speed and control.
Thanks for sharing your thoughts on this topic. It's always great to hear from fellow cyclists who prioritize safety and enjoy the ride. Keep pedaling and stay safe out there!
