[Closed] New wheels...... Speed wobble

Brexit.

(Not really, obviously!)

Could be that they are out of true on the vertical (assuming you hadn't checked that), but then it could just have been the wind.

It was just a slight tail wind ...... The wobble was sudden and violent !

I've taken both wheels out and checked tyres are both on true ..... So if they were loose or not in line then hopefully cured in process. .

Are the spokes tight?

Did you have your weight off the bars?

Spokes seem OK...... Riding position no different to normal.... It's a hill I ride down regularly

Might try isolating which wheel is causing by trying route again with old front wheel back in ....

I thought speed wobble was primarily determined by the bike's geometry, the distribution of weight on the bike (rider and any luggage), and reaching the speed necessary for the oscillation to occur.

I'm surprised that wheels would cause it, unless the geometry and weight distribution were such that the bike was already more prone to speed wobble, and the difference (maybe weight?) between the old and new wheels has been the tiping point factor which has resulted in wobble now occurring.

Tyres to wide for your new rim, it happened to me 🙄

really?? they are 25mm tyres .... not huge ??
what size tyres did you have ?

Any play in the bearings / adjusted correctly?

Tyres to wide for your new rim, it happened to me

Nonsense.

Your tires were not very uniformly weighted if new tires helped.

Ive seen this caused by wheels that have heavy spots - be it tyres or wheels or otherwise.

Spin wheel slowly if it's out of balance it will always stop with the same spot at the bottom.

Also seen some bikes where the frames not straight causing it. But if y was fine before wheel change then it's wheel related I'll bet.

Some kind of aero effect? Have they got a vastly different profile to the previous wheels? Deeper rims? Bladed spokes??

Sounds scary!

Speed wobble is a result of an input force setting up a vibration which then resonates.

The force/vibration can come from literally anywhere, hitting a pebble, the particular road surface, a slight variance in wheel true/weighting, the wind, anything.The particular resonance will be affected by things too, geometry, speed, weight distribution, flex/stiffness etc. Some factors will be very minor influences and easily overshadowed by others so it can be very difficult to both predict and locate the cause of wobble, changing one variable could completely eliminate it or magnify it.

I've only ever had one bike prone to it, and it was only prone to it with one particular wheel and tyre combo and at a very specific speed, changing either the tyre OR wheel got rid of it for me.

Basically it's time to get experimenting and process of elimination, however... Check your headset for correct adjustment as that's an often overlooked cause.

yes ... it was certainly scary ! The bike is normally rock solid..... and I went down the same hill a week earler ... only change is the wheels...... I shall go back over the suggestions made and doublecheck everything through ....

thanks for the input fellas

First thought was could the wheel be straight but slightly offset. Do a trial fit in the fork the other way round to see if the rims are different distances from the fork legs.

Other thought was, were you carrying a load on one occasion, eg back pack or panniers?

Were you cold? Sometimes a cold rider shivering downhill can cause.

I have had it a few times and it is truly terrifying, you have no control of the bike. Luckily each time I have had it the bike has veered to the left.

[quote=eskay ]I have had it a few times and it is truly terrifying, you have no control of the bike. Luckily each time I have had it the bike has veered to the left.

I used to be able to stop mine wobbling by pressing my knee against the top tube.

It went away on its own at some point so I think it must have been a bad tyre in my case (though it looked fine)

New wheels weigh much different at the rim/tyre?

Wheel weight will influence shimmy as part of the system that's resonating, as above it's mainly about weight distribution, frame flex and steering geometry - wheel weight can come into it as a heavier wheel will have a bit more resistance to the shimmy ie it lowers the resonant frequency enough for it not to be an issue / occur.

Only time i've ever had it, was due to not effectively tightening the cheap qr skewers on a bike - they had a really particular "bite" point & anything else meant they ended up too loose (which was obvious) or too tight & the lever wouldn't completely close (so, again ended up too loose - felt tight until you cycled down the street wondering why your steering felt weird).

Had it on a PX Pro Carbon. Because they're flexi floppy rubbish.

Mrjmt.

Funnily enough that's the bike we couldn't solve the issue on. It was utterly horrendous bike bordering on unusable.

If you didn't know it was coming it would havr you off the bike in a heart beat. As above if you clamp knees and increase the mass of frame it calmed down.

Transpired the fork ends and frame ends were a good 1/4-3/8s of an inch out of line with each other

Planet x and intense have one thing in common 🙂

Update .... So I've removed tyres and refitted ,.... Made sure everything is tight .... Took it steady down same hill ... Tentatively built up to 35 mph without the death wobble.... So fingers crossed ok ..... Will try again next week and see how it goes

check the wheel balance. ie where it stops when it spins

How heavy are you?
How many spokes on the new wheels?
I had similar experience. Upped spoke count and wobble went away

Upped spoke count and wobble went away

All other factors remained unchanged?

Just changed the wheels and could go as fast as I wanted
32 f&r - had been on low spoke count wheels
I'm about 90kg

Ah so you didn't just drill some new holes in the hub and rim. So could have been a lump of weight in the rim perhaps

djflexure - Member
Just changed the wheels and could go as fast as I wanted

So could have been many factors