Speed Wobble when descending down hill.

bayhota
bayhota Posts: 40
edited August 2015 in Road beginners
After a week of having my new road bike, i decided yesterday that i would mix it up a wee bit and under take a few climbs as part of my run. So yesterday i was descending downhill at rough 30mph on a country road( i had no computer), it developed a wobble on the front. I had to slow right down ( as it give me a scare). I thought the front wheel was coming off. After stopping i was soon back on the road again.
So yesterday i started to read up on it, and this morning i done the opposite route coming downhill on a main road, change my body posture, loosing my arms and legs, but had slowed right down before i took the bend before i took yesterdays wobble. And the bike started to wobble again, not as bad as yesterday but noticeable.

The bike i bought is a Trek 1.2, carbon forks, Aluminium, would there be something wrong with the actual bike?

Comments

  • simon_masterson
    simon_masterson Posts: 2,740
    Speed wobble is horribly scary, for all that experience it. It can be brought on by mechanical problems with your bike, but in truth it's a complex phenomenon that many boffins have investigated; I am not one of them. Keeping your upper body loose and putting a knee to the top tube can both help, but it might be worth having a cursory look over your bike, in case there are bearings with a little play in them or anything else loose. Since you've only had it a week, get someone with an experienced eye to help if you don't feel able to do this yet.
    Retro(ish) TT 2017-
    Fixed TT 2015-2016
  • kajjal
    kajjal Posts: 3,380
    Simpler causes are :-

    Tyre pressure too low
    Headset too lose or tight
    Brakes not setup properly
    Hubs too loose or too tight
    QR lever broken or too loose.

    Does it happen on all hills or just that one ?
  • davidof
    davidof Posts: 3,127
    Holding handlebars too tight.
    BASI Nordic Ski Instructor
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  • CYCLESPORT1
    CYCLESPORT1 Posts: 471
    Relax !
  • sungod
    sungod Posts: 17,440
    umpteen possibilities, but holding too tight is certainly possible, the way it works is the body can't react fast enough to correct a slight deviation, the lag results in the attempted correction amplifying the deviation, things get worse, fast

    the trigger for wobble may be cross wind, speed, road surface, etc., once it starts you need to resist the reflex attempt to correct by turning the bars

    things to do if you feel wobble developing, stay relaxed, try one or more of...
      firmly press knee(s) against the top tube unload weight from saddle gently apply
    rear brake

    if a wobble starts, avoid using the front brake, that can make things much worse
    my bike - faster than god's and twice as shiny
  • DavidJB
    DavidJB Posts: 2,019
    Don't know why people make such a big deal about it. I didn't even notice it as a thing until people started going on about it on this forum...descend with your knees on the top tube...problem solved.
  • drummer_boy
    drummer_boy Posts: 236
    I had this problem, with a new wheelset. Tried everything suggested here, and in the end I had the spokes totally readjusted.
    Sympathetic vibration (which is what this is) has a lot of components, frame, rider, wheels, tyres, grip, that virtually every instance has it's own origins, that you need to work though.
    Good luck, and stay safe!
  • bails1310
    bails1310 Posts: 361
    I had the same issue last year at about 40 mph to the extent the bike became out of control and u ended up on the opposite side of the road.

    Every decent over say 30 I take the same stance and:

    • move weight to the rear of the bike, not all weight on saddle
    • relax through the decent, always in the drops and don't grip bars the top two tight
    • as others have said, push notifications be knew firmly against top tube

    I lost all confidence after it happened, but touch wood, have not had a single occurrence since as have followed the above, scared the living doodoo out of me so can sympathise.
    Kuota Kharma Race [Dry/Sunny]
    Raleigh Airlite 100 [Wet/Horrible]
  • Sirius631
    Sirius631 Posts: 991
    Two that are down to maintenance:
      Front wheel out of true. Dirt ingress into headset bearing.
    To err is human, but to make a real balls up takes a super computer.
  • desweller
    desweller Posts: 5,175
    [url=http://www.bikeradar.com/forums/viewtopic.php?p=19659962#p19659962]DavidJB[/url] wrote:
    Don't know why people make such a big deal about it. I didn't even notice it as a thing until people started going on about it on this forum...descend with your knees on the top tube...problem solved.

    That suggests to me that you've never experienced it. I've only had small amplitude oscillation myself, which are easy to mop up, but looking at some youtube vids shows some bikes that display dramatic oscillation.
    - - - - - - - - - -
    On Strava.{/url}

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