Tankslapper!!

TigerTim

Hi All,

If I was on a motorbike it would have been called “a big tankslapper”. First time it happened me on a road bike (pedal). Coming down a hill at about 40K last Saturday on my Bianchi I hit a rough patch of road & the whole bike started vibrating & moving from side to side. I thought something had broken. Felt like the back wheel had come seriously loose. Was able to brake & get out of it but got some fright. First time it has ever happened me in over 30 years of cycling. Anyone else experience this?. Checked afterwards & nothing loose or broken.

T.

magicbastarder

speed wobble? 40km/h seems a bit slow for one though.

On motorbikes, are you meant to accelerate out of it, or am I thinking of something else?

Wishbone Ash

Has happened to me a few times particularly when very cold or tense while descending (usually while abroad). Clamping the top bar between knees sometime stops the oscillations.

poochiem

Bring your weight forward. Speed wobbles are well documented, plenty of videos and explainers. Scary

kal7

Pretty sure this is a common speed wobble, that could be better explained by other cyclists.

I have had that feel, it is like have a rear flat, strong wobble, it has only happened at high speeds though. Approx 55km/hr plus

I slow down and it stops, think due to my being tall and fairly heavy 95kg, think it is tyre warping.

Don't think I could accelerate out of it on bicycle, as you could in car or on motorbike

Wishbone Ash

https://cyclingtips.com/2011/03/speed-wobble-when-the-bike-shakes-its-head/

Harrybelafonte

TigerTim wrote: »

Hi All,

If I was on a motorbike it would have been called “a big tankslapper”. First time it happened me on a road bike (pedal). Coming down a hill at about 40K last Saturday on my Bianchi I hit a rough patch of road & the whole bike started vibrating & moving from side to side. I thought something had broken. Felt like the back wheel had come seriously loose. Was able to brake & get out of it but got some fright. First time it has ever happened me in over 30 years of cycling. Anyone else experience this?. Checked afterwards & nothing loose or broken.

T.

Coming down into Kilmacanogue (sp?) once it happened me at about 70km/h. Terrifying, but as guys said grab TT with legs/knees.

I had a proper tank slap moment on second last corner of Mondello one night. One big shake of the bike like a horse trying to throw me. Track was oily that night I think. Looked back and everyone had kept their distance.

Canis Lupus

I've had a speed wobble once but braking sorted it out although it wasn't severe.

There's lots of advice surrounding the subject, some say grip hard, some loose etc but to be fair you'll probably just go instinctual and hit the brakes to some extent. Assuming you're not completely bombing down the side of a mountain you should be fine.

CramCycle

Had it once where the speed coming down a steep hill on my audax bike seemed to cause the dynamo to reverberate and cause the frame to oscillate. Scared the sh1t out of me, the frame felt like it was warping underneath me. Managed to clamp the top tube with my legs and stutter to a stop and nearly crash into a wall while I tapped the brakes.

magicbastarder

i've wondered what difference clamping your knees onto the frame, vs. simply being in the saddle makes, in such situations.
you can certainly feel the difference while wobbling the bars, between seated and standing, so i guess i just assumed that your arse on the saddle is the greater part of the stabilising effect.

CramCycle

magicbastarder wrote: »

i've wondered what difference clamping your knees onto the frame, vs. simply being in the saddle makes, in such situations.
you can certainly feel the difference while wobbling the bars, between seated and standing, so i guess i just assumed that your arse on the saddle is the greater part of the stabilising effect.

I think it part psychological, part of it may possibly do something like absorb some of the vibrations, for me, it seemed to make me more stable, so I didn't feel like the bike was going to throw me off, which made me slightly less likely to sh1t my pants or crash.

Cee-Jay-Cee

Yeah it happened me once at about 60kmph when I veered slightly on to loose gravel. The whole bike started wobbling from side to side. I managed to get out onto the road again and brake to a stop. It took me 5 minutes or more to calm myself down enough to continue. Some scary shít that!!

AxleAddict

I've had it happen to me twice - both times at speeds upwards of 65kph - the second (and easily scariest) time it happened was on the descent from Glengesh (Co. Donegal) after the switchbacks - thankfully no traffic - felt the initial oscillations, which then quickly intensified - over time I've managed to suppress my natural instinct to pull hard on the brakes in danger situations unless absolutely necessary and gradually trimmed off the speed.

Not sure what exactly triggered it on that occasion - I'm a fairly steady rider - not weaving in and out all over the place - I've been down that descent a few times without issue - but I sure was glad I managed to bring it back under control - real 'life-flashing-before-my-eyes' kinda moment that particular day! I normally love my descents but it certainly has made me a little more cautious since. After the most recent episode I did take some time to look into it more and came across much the same advice (some of it conflicting) that has already been discussed here - hopefully won't have to put it into practice!

TigerTim

Thanks for all the replies. Was a scary moment OK. Max speed on that descent was 48KM/h. Must have been the rough section I hit that caused the initial oscillations & it just got worse. Have some info anyway if it happens again. I'll have to fit a damper to the handlebars like used on the motorbikes :P

Thanks,

T.

D13exile

Happened to me once on the descent from Moll's Gap to Kenmare where I hit 64kph. Bike started to vibrate after I went over a small pothole and I thought I was going to lose it and end up doing a Superman flight before shredding lycra and skin all over the road. I resisted the urge to pull the brakes as the bike was really starting to wobble and I straightened up as best I could and gripped the frame with my thighs and they seemed to calm the vibration down. Scary as hell though and not an experience I'd like to repeat. I actually prefer climbing to descents. I wonder why?????

Cionn

Same thing happened to me too on a decent in Wales, I had the added complication of having to pass over a cattle grate as I was trying to slow down, still at 40+ kph. Basically I stopped braking and concentrated on balance until I got the bike under control. Those bib shorts have now been retired.

C

ednwireland

front wheel isnt a mavic ksyrium notorius for a wobble when hit by an unexpected crosswind

Cionn

Funny you say that, mine was a pair of Ksyrium's. I didn't get on well with them on that trip and changed them shortly after, I went Fulcum and never looked back. Horses for courses and all that.

TigerTim

ednwireland wrote: »

front wheel isnt a mavic ksyrium notorius for a wobble when hit by an unexpected crosswind

I didn't know that. I've Mavic Ksyriums front & back. Was just looking at the bike in the garage last night & gripping/shaking the wheels from side to side. There is quite a bit of movement even thought the wheels are tight in the forks & spokes perfect & wheel running true.

Thanks for the info,

Interesting.

T.

AxleAddict

Likewise, a Mavic Ksyrium wheelset (disc, thru-axle) on my bike...

m5ex9oqjawdg2i

I hit a speed wobble at about 70km/h, stuff of nightmares. I'm not good at descending, normally keep below 60, closer to 50. This time i said i would try and go a bit faster. Never again. It didn't help to have a car stuck to my back wheel. A gust of wind started the wobble and that was that. I just rode the brakes and prayed to the god named Fcuk, if you say his name over and over again it helps.

fryup

its yet to happen to me ....feeling apprehensive going on the bike after reading this thread

TigerTim

fryup wrote: »

its yet to happen to me ....feeling apprehensive going on the bike after reading this thread

I'm cycling for well over 30 years & its the first time its happened to me & I have the Mavic Ksyriums for quite a while too. At least we've some info now if it happens again.

T.

magicbastarder

TigerTim wrote: »

I'm cycling for well over 30 years

you must be knackered!

(never gets old)

(well, for me at least)

Daroxtar

I had it a couple of times, first time terrified me coming down Ballinascorney full pelt towards the army camp.
I actually have one wobble on video, skip in to 4.55. I got that back in line very quickly by jamming my knee on to the top tube (luckily, as there was a rock wall on one side and a good drop on the other!!)

https://www.youtube.com/watch?v=JXNbj0pOREc

magicbastarder

it's a pity you overlaid a soundtrack on that, i'd have been curious to hear what the live commentary was like during the wobble.

fryup

so the thing to do is to..close your thighs tightly on the upper bar?

Esroh

First time this happened to me, knowing how to take a fall a from riding horses I relaxed and waited for the crash . It did the trick. I'm not a good descender
The theory behind the knee grip is to get you to take the tension out of your arms by concentrating on your knees.
The more you fight it the bigger it gets.

Daroxtar

magicbastarder wrote: »

it's a pity you overlaid a soundtrack on that, i'd have been curious to hear what the live commentary was like during the wobble.

You can't hear anything other than the wind





Escaping

CramCycle

Esroh wrote: »

The theory behind the knee grip is to get you to take the tension out of your arms by concentrating on your knees.
The more you fight it the bigger it gets.

The more you know, I thought it was to stop or absorb osscillations