A bike that does not shimmy / speed wobble

[User65906]

Hi everyone, I recently bought a Genesis Ridgeback day 00,
it is clean, did only ten miles and was stored in a house.

I know now why it only did Ten miles, I took it out and began pushing it
on a slight downhill straight, and all of a sudden it started to wobble like
a jelly, almost lost it, if it had of been wet I would have come off.
I was only doing 30 mph, its useless to me, as I need to go a lot faster than that.

I checked the bike, nothing wrong mechanically, or with tires and wheels,
it cost me very little but I need to replace it with something that owners
have found to be be ultra stable at speed.

I just sold my voodo agwa, which was a rolls royce compared to the Genisis,
I could ride that halfords lump flat out and never had any moments on it at all
on the very same terrain the Genisis crapped out on,
so much for marketing BS, the Genisis is the worst bike I ever owned.

I would like to hear from users of bikes in the 1000.00 quid range that can be pushed and
remain planted, ideally endurance rather than pure race, but ultimately I will take
the one that is the most sure footed and easy to handle, and from my experience on
the Genisis, I have changed my mind about sticking with alloy unless the experience of
others prove me wrong, I even like the specialized allez and would consider it if others
have pushed it to good effect, but Carbon is becoming more acceptable to this old dog,
as it would seem that weight for weight Carbon is a lot stiffer and not much more expensive.
The 6061 alloy in the Genisis is what I blame for its flex, the 7005 in the voodo did not flex, but
in fairness the tubes were also much larger, should have kept it for all I got for it put better
wheels on it to train in the wet.

Looking forward to hearing of your experiences and recommendation.

 

[Venod]

I had a Raleigh 531 (steel) that nearly killed me descending Holme Moss at about 45mph the shimmy was uncontroble, it's the only bike I have had problems with descending.
My favourite bikes for a fast stable descent are CX bikes, big tyres, big forks, tapered headtube.

 

[User65906]

Thanks Afnug
Am not familiar with cross bikes, / cyclo cross, but if am not wrong
they are geared for slower pursuits, the bb is higher off the ground too.

Like you I never had an issue before this one, so now I know its possible
I need to find a steed that is not known for this kind of behavior, I looked
into the possible causes and cures, engineers cant even agree on what causes
it, and the user solutions are also varied, and in some cases there simply is
no cure, so am going to get something safer.

 

[Slick]

That certainly sounds unusual. This is my Genesis descending that was handled with ease. You might have to fast forward the first couple of minutes, I needed a breather after getting up there.

View: https://youtu.be/7nCOR0HzV1o

 

[User65906]

Good bike work Slick,
this is the model I have, no drops.
https://www.cyclechat.net/attachments/i_3-jpg.405763/

 

[User65906]

Here is the belly dancer I speak of

 

[Slick]

Here is the belly dancer I speak of

Looks like a nice bike, seems strange to get problems like that on a new bike.

 

[Tim Hall]

It's a resonance thing, caused/affected by high tyre pressure, low tyre pressure, height of stem, length of stem, position of saddle, height of saddle, size of rider, weight of rider, wind, road surface etc etc. Saying it's down to a particular bike is unlikely.

 

[User65906]

That bike is 6 or more years old, the original owner put the miles on it,
and I can see why he did not use it, am puzzled too, going to swap out
the front wheel and see what happens, though I can see nothing wrong
or off balance with its own wheel, but its too wet to chance it tonight.
The rims are like new, as are the tyres, must check pressures again too.
to me its an odd bike, front has a steel fork, yet it feels very light, back
end seems too heavy, something is off, lifting the bike one needs to grab
it almost at the seat post, my hands are also sore carrying my body on the
bars, it feels like am wedged into the bike, instead of balanced on top of it.

 

[User65906]

Hi Tim
I have no links saved, but I read about a guy on a defy having similar shimmy,
and another guy commented his defy did the same, there was one other bike
that people commented on a whole lot more which was just too dangerous
to ride at all, all the commenter's who owned it ditched it after tinkering with
tyre pressures, seat height, seat for and aft, stem adjustments ect, engineers
could not agree as there are simply too many variables.
My tires were fine, but am checking them again, the seat was quarter inch
or so too low, but a higher seat would have made the shimmy worse.

 

[the snail]

my hands are also sore carrying my body on the
bars, it feels like am wedged into the bike, instead of balanced on top of it.

I reckon that's more likely a factor in the wobble. If you're tensed up, with a side wind or poor road surface that could put you into a wobble. Very unlikely that an aluminium frame will flex much unless it's broken imo. The only time I had a speed wobble on a bike, I came to the conclusion it was down to me being cold/tired/tense in combination with a side wind - I've ridden down the same hill lots of times and covered 1000s of miles on that bike without any wobbles.

 

[Levo-Lon]

as its a flat bar i'd try a wider bar first.
check wheels are good ,spokes and bearings ,maybe a longer stem?

 

[User65906]

Thanks to all who posted.
I had a look at the tires again, and the back one was down a little, but oddly after the wobble
I tired to induce it again and could not, so still not sure what caused it.
I investigated spokes, bearings wheels brake pad clearance and mechanics,
head tube is free with no movement or binding, nothing wrong that I could find,
and ive been blown to the other side of the road when I was young, and have had
a good few blast since then and never got the same degree of unstoppable wobbling
that I got the other night with no wind involved.
Handlebars, are painful to lay into so had a look at them, first off they are
thin, I did not take off the rubber but they look about an inch in diameter, and to
top that off, the rubbers have a bulge cast onto them, this causes the grip
to be always at an angle no matter where you rotate the humpy bit, it still knocks
your palms or fingers so you never get comfortable, looking closely at the bike
these grips look to have been substituted from something else, they are not at all
worn but they do look like older rubber and may not be original.

I'm looking into either a CAAD12 v brake with 105 or a Synapse carbon with the same setup.
I think the Synapse would suit me better being more relaxed and comfortable,
but it is 250.00 more, am wondering if the CAAD12 in alloy is really that much more harsh or
twitchy to justify going for the Synapse.

I had considered a Trek Edmonda AL5 for a brief moment, until the little voice in my head
said, remember last month whey you priced a Trek and was quoted 2800 as being the cheapest
carbon Trek available, that con man sent me straight to Canyon where I got a bike for considerably
less, I can still get an Edmonda in carbon for less than the 2800 quoted,
but that crook has put me off Trek, so Cannondale will be the beneficiary this time round.

Any comments on the Synapse or CAAD12 welcomed, to help me hone in on which would suit.

Thanks & Regards to all who posted.

 

[User65906]

I reckon that's more likely a factor in the wobble. If you're tensed up, with a side wind or poor road surface that could put you into a wobble. Very unlikely that an aluminium frame will flex much unless it's broken imo. The only time I had a speed wobble on a bike, I came to the conclusion it was down to me being cold/tired/tense in combination with a side wind - I've ridden down the same hill lots of times and covered 1000s of miles on that bike without any wobbles.

I had a slightly soft back tire, but not that one would notice, I put the gauge on it and found it just low of where I left it,
I have had tires much lower in pressure and no wobbles, but I will pump both wheels before trying again when its dry,
I will also be changing the bar ends, as they are a bad shape and ensured my hands were never at a relaxed angle on the bar,
this I believe is what caused me the hand pain, for my arms were fine,
the seat is like a steel banana, but will do for testing, I would like to get to the bottom of what caused this wobble,
so will try harder tires, if I cant induce the wobble on the same stretch of road, I will let out some air and proceed
with caution a little more speed each time to see if anything stirs, I want to like this bike, but until I understand why
it went like a jelly I will not be happy with it.

 

[User65906]

as its a flat bar i'd try a wider bar first.
check wheels are good ,spokes and bearings ,maybe a longer stem?

Thanks for commenting, the bike has a 90 mm stem, a longer stem wont work for me, I wont be able
to reach the bar with comfort, the bar is quite wide already at 570 mm, so will try to figure out what
caused the wobble if I can, the bike was cheap so not going to invest much in it unless I can sort the
wobbling, I have a Canyon CF SL7 with only 400 mm bar and no problem with controlling it.
A bend backwards at the end of the bars would make it easier for me to get at the back facing shifter leavers,
for right now they have to be low down, thus thumbs are stretched to reach them, if I turn them up
this turns down the brake leaver on the front of the bar which makes them too difficult to grasp, this
is mostly to do with the angled rubbers on the bar, getting rid of them or finding a bar with a slight
bend back at the ends will angle my hands so the thumb will be located a little further forwards towards
the short shifting lever, never seen shifters with such short levers before.