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  1. #1
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    Help: Scary braking wobbles whilst cornering going down hill.

    Having just taken up using drop handlebars I have a rather concerning problem.
    As I descend the mountain where I live as I reach corners I brake to slow down (still not confident with skinny tyres coping with my 115kgs) the handlebars start to wobble, if I try to slow down even further it gets uncontrollable. Today it almost had me off the bike and into the crash barrier in front of a bus.
    This is NOT the speed wobbles, I am going slowly and gets progressively worse as I slow down
    It only occurs when I turning fairly sharp corners whilst I am going downhill.


    The bike is new and has been professionally checked so it is not a mechanical issue I am doing something wrong.


    Any suggestions for causes and cures will be very gratefully accepted.


    Chris
    Hobart

  2. #2
    Matnlely Dregaend
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    Re: Help: Scary braking wobbles whilst cornering going down hill.

    Sounds like your brake pads aren't bedded well. Wipe off the rims with some mild abrasive and do some long straight braking and see if it clears up. I'm assuming you're using aluminum rims?
    "I haven't @#&$ed like that since I was an altar boy." - Hank Moody
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  3. #3
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    Hard to say without watching you in person. And, downhill turns can be challenging for everyone. But, maybe a basic refresher on turning form:

    - control your speed early - better to enter the turn embarrassingly slow than too fast (gradually build your confidence). On a big descent this means you will spend a lot of time dragging the brakes or even braking hard. That's ok. Keep your brake pads lean and free of grit.

    - your fit and position on the bike is critical. If your handlebars are too high, too low, too forward or rearward it can cause problems.

    - elbows bent, not straight and locked.

    - hands can be on the brake levers ("hoods") or on the hook part of the drops (best for intense braking) .

    Note that when your hands are on the lower part, snug them up into the hooks and you should be very stable and solid; this also shifts weight toward the front wheel, so on a very steep descent while braking you should slide your butt backwards to keep the rear wheel weighted. In the extreme, you'll have your arms fully extended, butt back almost off the edge of the saddle.

    It's ok to brake while turning but understand that will cause the bike to want to "stand up" and move your line toward the outside of the turn. Compensate in advance.

    Relax and breathe. Wobbles are frequently associated with nerves. Look where you want to go.


    * posted by Creakybot 2013 all rights reserved.
    * not actually waterproof.

  4. #4
    wim
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    Quote Originally Posted by Creakyknees View Post
    Wobbles are frequently associated with nerves. Look where you want to go.
    Agree, "nerves" is the most likely cause here. While people often get nervous when the speed goes much beyond 30 mph, you probably get nervous because a curve is coming up. That's perfectly understandable.

    Small point on going into a turn: it's correct to say that it's better to enter the turn embarrassingly slow than too fast. On the other hand, many riders misjudge speed too much on the side of caution. If you slow down significantly on the approach, but then feel after you've completed the turn that you could have gone through it much faster than you did, you slowed down too much. Of course, if you're not going to race, none of this matters. Slow down and live. :-)
    Last edited by wim; 05-13-2013 at 09:51 AM.

  5. #5
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    Quote Originally Posted by DrSmile View Post
    Sounds like your brake pads aren't bedded well.
    What does this even mean? "Bedded well"? Either they are installed correctly or they aren't... brake pads don't need a "break-in period". As long as they are clean and free of grit, they should work.
    * posted by Creakybot 2013 all rights reserved.
    * not actually waterproof.

  6. #6
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    Quote Originally Posted by Creakyknees View Post
    What does this even mean? "Bedded well"? Either they are installed correctly or they aren't... brake pads don't need a "break-in period". As long as they are clean and free of grit, they should work.
    This isn't true for most aluminum rims because they are ridged, and the pads are flat. In addition even if you tighten the pads with the brakes fully engaged, the rotation of the wheel tends to bend the pads / holder / brake slightly while braking, causing slightly uneven wear until the pads wear in. I notice this on hard braking with any new pads, and it's most noticeable with very hard pads.
    "I haven't @#&$ed like that since I was an altar boy." - Hank Moody
    “Bicycling has done more to emancipate women than anything else in the world.” - Susan B. Anthony 1896
    "Genuine Campagnolo Spares - Inserts for Dura Ace pattern brake shoes." - PBK

  7. #7
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    Quote Originally Posted by DrSmile View Post
    This isn't true for most aluminum rims because they are ridged, and the pads are flat. In addition even if you tighten the pads with the brakes fully engaged, the rotation of the wheel tends to bend the pads / holder / brake slightly while braking, causing slightly uneven wear until the pads wear in. I notice this on hard braking with any new pads, and it's most noticeable with very hard pads.
    ^this^

    I got an older bike and checked it over (I thought) thoroughly. Took it for a spin and everything seemed great. On a descent at 30+ I started braking and nothing. I grabbed a little more and the wobble started. After feathering, alternating and pushing myself as far back as possible, I got it slowed down. Old, dried out pads, but they were no problem under 30 or so. New pads, problem solved.

  8. #8
    wim
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    Quote Originally Posted by Blackbeerthepirate View Post
    I got an older bike and checked it over (I thought) thoroughly. Took it for a spin and everything seemed great. On a descent at 30+ I started braking and nothing. I grabbed a little more and the wobble started. After feathering, alternating and pushing myself as far back as possible, I got it slowed down. Old, dried out pads, but they were no problem under 30 or so. New pads, problem solved.
    More likely, nervous-tension wobble when you tried to brake and nothing happened. With new pads, you're calm and collected because you know they work. I don't see either how "ridged rims" and pads not "worn in" could possibly cause a wobble.

  9. #9
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    Quote Originally Posted by wim View Post
    More likely, nervous-tension wobble when you tried to brake and nothing happened. With new pads, you're calm and collected because you know they work. I don't see either how "ridged rims" and pads not "worn in" could possibly cause a wobble.
    It causes pulsation, which can lead to a wobble if you're turning.
    "I haven't @#&$ed like that since I was an altar boy." - Hank Moody
    “Bicycling has done more to emancipate women than anything else in the world.” - Susan B. Anthony 1896
    "Genuine Campagnolo Spares - Inserts for Dura Ace pattern brake shoes." - PBK

  10. #10
    wim
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    Quote Originally Posted by DrSmile View Post
    It causes pulsation, which can lead to a wobble if you're turning.
    Thanks for the reply. Never heard of this, but I'll think about it some more.

  11. #11
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    Bike like as you are driving a car approaching a turn: Brake before you enter the turn, coast in the turn and accelerate out of the turn. Also, make sure you pick the right line(apex of the turn) before you go into the turn.

    I get a little bit nervous on descent turns myself since I don't get to practice much. Thus I try to remind myself to do the advice above. As other posters said, it's all about getting use to doing it. The more you do it, the more second nature it will feel.
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  12. #12
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    Quote Originally Posted by wim View Post
    Thanks for the reply. Never heard of this, but I'll think about it some more.
    I'm not convinced this is the issue of the OP, I've just experienced it with new pads (Swiss Stop) that were pretty hard so I figured I'd mention it...
    "I haven't @#&$ed like that since I was an altar boy." - Hank Moody
    “Bicycling has done more to emancipate women than anything else in the world.” - Susan B. Anthony 1896
    "Genuine Campagnolo Spares - Inserts for Dura Ace pattern brake shoes." - PBK

  13. #13
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    Quote Originally Posted by Creakyknees View Post
    Hard to say without watching you in person. And, downhill turns can be challenging for everyone. But, maybe a basic refresher on turning form:

    - control your speed early - better to enter the turn embarrassingly slow than too fast (gradually build your confidence). On a big descent this means you will spend a lot of time dragging the brakes or even braking hard. That's ok. Keep your brake pads lean and free of grit.

    - your fit and position on the bike is critical. If your handlebars are too high, too low, too forward or rearward it can cause problems.

    - elbows bent, not straight and locked.

    - hands can be on the brake levers ("hoods") or on the hook part of the drops (best for intense braking) .

    Note that when your hands are on the lower part, snug them up into the hooks and you should be very stable and solid; this also shifts weight toward the front wheel, so on a very steep descent while braking you should slide your butt backwards to keep the rear wheel weighted. In the extreme, you'll have your arms fully extended, butt back almost off the edge of the saddle.

    It's ok to brake while turning but understand that will cause the bike to want to "stand up" and move your line toward the outside of the turn. Compensate in advance.

    Relax and breathe. Wobbles are frequently associated with nerves. Look where you want to go.


    Good stuff. Too bad I can't rep you because you're already over-repped.
    My other chainring is a 39...
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  14. #14
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    Quote Originally Posted by wim View Post
    More likely, nervous-tension wobble when you tried to brake and nothing happened. With new pads, you're calm and collected because you know they work. I don't see either how "ridged rims" and pads not "worn in" could possibly cause a wobble.
    Believe me, there was plenty of nervous-tension when I grabbed the brakes and nothing happened. I was trying to slow before a big sweeping right.

    Quote Originally Posted by DrSmile View Post
    It causes pulsation, which can lead to a wobble if you're turning.
    Whilst in the turn, I got some brake and then the wobble. There was zero degree of turn in my front end. I was leaning sooo far right it was stupid. I was thinking it would be better to slide out than high-side, but it stuck.

    After the new pads I have done this descent a few times. A lot slower the first time but faster after that. Never as fast as the wobbley ride but pretty quick. No problems. Don't know which was the cause for sure but I'm leaning toward the pads.

    Thank you Haggismuncher for allowing me to use "whilst". Cool word.

  15. #15
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    Quote Originally Posted by Blackbeerthepirate View Post
    Thank you Haggismuncher for allowing me to use "whilst". Cool word.
    You learn something every day, I never knew Americans don't use "whilst", as a Scot living in Australia there are so many words I either have to learn or others I have to stop using.

    The front wheel is straight,
    the brakes new and so at the pads, frame is brand new and straight
    I fear only one factor is to blame and that is the pilot.
    Seems I may need lessons in cornering better.

    Oddly it is not a problem if I am on the hoods just on the drops (but that may of course be that I am braking more as I can reach more from the drops).

    As for trying to brake before corners this is a problem as the road is perhaps 3 or 4 km of 5 to 7% with a mix of wide sweeping bends and a couple of sharper ones. Being a fatty I pick up speed very quickly but being a coward I don't believe I will corner well so I brake, leading to wobbles.

    Chris

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