My wife has bought a Cannondale Topstone 1 recently. It was supposed to be the bike of dreams, replacing and old hardtail and her roadbike.

But she’s a bit disappointed with it.

The problem is at speed on road (I don’t know what speed, I’m not a road biker but would say she’s reasonably quick down hill) she gets speed wobble. The first time she rode it said it was awful & scary, she’s now able to “manage” it a bit better but she’s still not happy with it.

Her old £300 Boardman is much more stable at speed & more confidence inspiring apparently.

It’s gone back to the shop for them to check it out, the front wheel feels slightly rough but nothing excessive. She’s also going to try different tyres (it has some semi slick road tyres of some description at the moment).

Is this just likely to be a gravel bike not as good on road as a road bike (even an old cheap one) thing or anything else to look at? Known issue for a Topstone?

At the moment she’s considering selling it, accepting a loss and looking at something else. It was a bit of a rush buy but she did ride it first, just not down any steep hills.

Cheers

Gravel bikes are more stable (generally) than road bikes, so not a clue what’s going on here

It’ll likely be an accumulation of factors: weight distribution, balance, bars, wheels, tyres, tyre pressures, aerodynamics. Try making small changes to any of these to see if there is an improvement. I doubt that there is anything inherent in the bike itself.

has it got a shorter stem than she is used to when compared to her road bike?

I swapped the stem on my road bike from something like 110mm to 80mm, and the speed wobble it introduced was amazing – I got used to it in the end, and dont suffer from it now, but it was quite surprising how much speed wobble there was as a result of just a shorter stem.

I agree with scotroutes.

This can happen on almost any bike. It’s about the combination of geometry, handlebars, weight distribution etc…

Motorbikes suffer the same issue. Some motorbikes are fitted with bar end weights while others have steering dampers – all to stop the dreaded ‘tank-slapper’

I’d change the handlebars for something slightly wider or heavier and go from there. You could even fit some weight inside the outboard end of the handlebars you already have – that might just be enough :o)

Loads of detail on this and things you could do to adjust over on CyclingTips.

Is there any play in the headset? This can produce some pretty scary tank slap. Had it on my Soulcraft a few years back. I thought the headset was seated properly but it wasn’t quite. A quick tweak and the slap was sorted…

I have a Topstone and haven’t had any issues with riding downhill on roads. Coming off a flat bar MTB your wife might not like the different position. Does she ride on the drops or hoods? Mine feels super on the road riding on drops, very comfortable and stable.

Yep, I agree with the comments up there that in general a gravel bike will be more stable than a pure road bike. Mine certainly is. So it’s definitely not a “gravel bikes are not designed for the road so they do this” kind of thing. That cyclingtips article is good. I’d try it with different tyres and a thorough check that all is snug (particularly headset and wheel bearings) first, and then tweak one thing at a time. For some people it only happens rarely and is hard to predict; for others it’s very repeatable so easier to assess whether a change has fixed it.

It’s a very difficult thing to pin down. It’s a mix of everything, geometry, wheel profiles, wind, weight, rider position, all sorts, even loose headset. Check tyres are on straight too.

I’ve only had this on one of my road bikes when either I’ve been descending with full guards at speed, or was hit at about 50 mph by strong side winds – started the wobble, I eased off, wind went, back on with the speed.

My custom hand built bike is a dream – never done it, although I’m too chicken to hit 60 on it these days – when I was in my 20’s – yup, not 50’s.

The Topstone has a fair bit of fork offset and a slacker HTA. Works well generally but it may be putting less rider weight on the front wheel naturally. If that’s accounted for (saddle fwd or right position overall, right stem length etc) it might eliminate it by changing weight distribution. I doubt the frame itself is prone to shimmy – stiffness is likely to be high enough that it won’t happen at least not when unloaded.

Back in the day this sort of wobble was a problem on one edition of the Range Rover, Land Rover solved this by adding a mass damper. Does a full water bottle achieve the same thing?

I’ve both had it and not had it on the same bike (a 531 tourer) so all kinds of factors could be the one (or combination of) that is causing it. In the end I just relaxed and it seemed to improve. Maybe have a watch of this?:

I’ll echo some other posters. It’s really weird to have a speed wobble on a modern gravel bike. Not only is the geometry better suited to descending (longer, lower, slacker) but modern bikes tend to be stiffer than noodly steel frames of old. So it sounds like something is broken or poorly fitted, perhaps headset, something with the fork or hub, perhaps even a tyre that isn’t properly seated and only reveals itself at speed.

Um. I may be wrong here. But I didn’t think speed wobbles/tank slappers were anything to do with the general stability of the bike’s geometry. It doesn’t wobble because of the twitchiness of the geometry.

Speed wobble is caused when something, either an inherent misalignment of the frame or components, or an outside force, that causes the wheels to track divergent paths. The frame flexes to allow this to occur until the action is overpowered by the self-correcting forces created by the bike’s steering geometry.

(From https://roadbikeaction.com/ask-rc-what-causes-speed-wobble-2/amp/ )

In motorbike terms a Harley is just as likely to tankslap as a GSX-R750.

Thanks everyone. I’ll point her at this thread and check the bike over again when it’s back.

Um. I may be wrong here. But I didn’t think speed wobbles/tank slappers were anything to do with the general stability of the bike’s geometry. It doesn’t wobble because of the twitchiness of the geometry.

Agree. I would be thinking there is something wrong somewhere rather than blaming geometry, stem length etc,. Those things will affect the handling but why would they introduce a speed wobble

My Marin 4 corners gets wobble at higher speeds when I ride no handed. It’s a bit annoying but holding the handlebar again stops it so it’s not a big issue. If it was happening when holding the bars I’d be taking it back as it would not feel safe.
It has quite a high front end (which is good for my T-Rex arms) with some spacers so maybe that doesn’t help? No idea really.
I do have a Dynamo front hub which does “pulse” a little when you turn the axle by hand but you can’t feel it when riding the bike at all. Maybe that isn’t helping.