Speed-wobble on the flat - stiiffer front-end required?

IShaggy

I was giving a Strava segment a good thrashing the the other weekend. It's a flat segment, and I was just north of 45kph (OK, I'll admit, I did have a tail-wind ;-)) when my front-end went light and started to wobble. I backed off a bit and it calmed down, and then it started to wobble again when I put the power back down. It was towards the end of the segment, and so my pedalling was probably getting a little ragged - however my cadence was relatively high at 110bpm.

I checked the headset and hub, and nothing's loose. I've never experienced speed wobble on the bike in question before - although I have on a previous bike - but only downhill - so know the feeling.

Generally the bike descends well, and the front-end feels OK in the corners. But I do know that the fork has a reputation for being a little soft.

Does this suggest that it might be worth investing in a stiffer fork, or is it just one of those things to be expected from time to time?

cougie

I'm not sure anyone knows the real reason behind speed wobbles - I know I had one coming off the moors in a howling gale one time - but it never happened again.

I'd not change the fork on one occurrence.

IShaggy

Maybe I'm looking for an excuse to upgrade the fork ;-)

I wonder whether a stiffer fork could adversely affect the handling. As I said, the bike descends and corners well. Would a stiffer fork improve this, or could it adversely affect this - by not bring compliant enough?

iron-clover

I'm not sure speed wobbles are just caused by flexy forks, and if it already descends and corners well then it probably isn't that flexy anyway.
Also, if you've only experienced it once it could well have been certain wind conditions buffeting you into the wobble- I can feel these coming on at very high speeds sometimes which is when I gently apply the brakes, but there's no reason why it can't occur at slower speeds too depending on the system.

What are you currently using?

IShaggy

I've got a PX Ti Pro - the Lynskey made one from a few years back - paired with PX forks. The frame is solid, and the best thing I've ridden (and I've ridden a good few bike so have some idea). It's a keeper for life. But the forks are soft, and have a reputation for being so. I've had no handling problems till now. So maybe a one-off or may be a hint that things could be improved. I'm currently also riding a Kinesis Aithein and the Aithein front end is definitely stiffer and it's a little sharper in the corners.

sloppyschleckonds

Buy a new bike

IShaggy

I've got a few on my n + 1 list. Bank manager says NO!

andrewjoseph

good article on speed wobble in issue 33 of cyclist magazine.

diamonddog

^^This, very good article.

First.Aspect

You were cycling too furiously.

DavidJB

Never ever had this issue...

IShaggy

First Aspect wrote:

You were cycling too furiously.

And wantonly. But it did not lead to bodily harm so I didn't break the law ;-)

debeli

IShaggy wrote:

I was giving a Strava segment a good thrashing the the other weekend. It's a flat segment, and I was just north of 45kph (OK, I'll admit, I did have a tail-wind ;-)) when my front-end went light and started to wobble. I backed off a bit and it calmed down, and then it started to wobble again when I put the power back down. It was towards the end of the segment, and so my pedalling was probably getting a little ragged - however my cadence was relatively high at 110bpm.

I checked the headset and hub, and nothing's loose. I've never experienced speed wobble on the bike in question before - although I have on a previous bike - but only downhill - so know the feeling.

Generally the bike descends well, and the front-end feels OK in the corners. But I do know that the fork has a reputation for being a little soft.

Does this suggest that it might be worth investing in a stiffer fork, or is it just one of those things to be expected from time to time?

No, of course you don't need a new fork. But you knew that.

Indeed, a speed wobble may be as much attributable to too much stiffness in one or another part of the wheels and frame set as too little.

There are so many variables and thus so many possible causes that to isolate the front fork on the basis of one occurrence seems unwise.

Do you invert the frame to put the wheels in and lock the QRs? If so (and this is not an uncommon cause of wobbles - through front or rear wheel) it could be that the wheel is locked by the QR while minutely out of true. Flip the bicycle onto its wheels and (if it has standard modern vertical drop-outs) bear down on it while releasing and re-fastening the QR levers. It's amazing how many times a slightly (very slightly) wonky wheel can lead to the wobbles and the slapping of tanks. If the wobble is a one-off, this is not unlikely to be the cause.

But whatever you choose to do, do not feel the need to blame a speed wobble on the front fork. It can be triggered by many other components and indeed by the person on the bicycle.

I hope I have helped, but I fear I have only made you more determined to 'upgrade' what was fine in the first place. I speak as an expert, having recently upgraded my trowel as my bricklaying was no good. It is always the tools.

thegreatdivide

You need thru-axles. Preferably on a Giant Defy.