Not sure what the hells going on but I bought a Giant TCR which comes with 42mm deep aero wheels and the bike wanders all over the place at high speeds or in the slightest side winds.

These are my first pair of “aero” wheels and, frankly, they terrify me. What am I doing wrong?

How heavy are you?

88kg (and 1.93 metres, or 6’4″, in case that is relevant…)

42 mm is not massively deep, you may get some disturbance from wind but nothing major.

Are the tyres seated squarely and are the rims true?

Have you ridden road bikes before? If not it may be you are unconsciously tensing up during the quicker descents.

Speed wobble is frightening at high speed.

Not sure about the tyres so I’ll check that out but not seen or felt anything odd

Yes, I’ve ridden multiple road bikes before but none with “deep” rims (granted, mine aren’t particularly deep).

My other road bike is a Cannondale SpeedSix with bog standard rim brakes and I would confidently hit 80km/h+ down the local ski hill roads but the Giant is terrifying, even when I consciously relax…

I have a tcr with the slr1 42 mm wheels and it’s the most jittery bike I’ve ever ridden at speed. I’m not sure what you are experiencing is speed wobble as such, rather just the nature of the bike!

For what it’s worth mine is super fast, but I far prefer my defy for most of the riding i do..The tcr feels like it’s always on edge.

The problem now is overcoming the subconscious fear of descending on this particular bike.

I had this once on a bike I owned and I failed to ever trust it at speed after a couple of out of control speed wobble experiences where the bike shook violently. I stopped riding it because it scared the shit out of me.

Like you I have had multiple road bikes and have been on TT aero bars at 50mph but just could not ride that bloody thing!

The wheels will contribute to a bit of instability, in the wind, but it’s more likely down to speed wobble. A friend of mine had it, in his mountain bike, descending from Whinlatter pass to Keswick.
We looked into it, afterwards, and discovered that it can be solved by gripping the top tube between your knees – this changes the resonance of the bike, and stops it wobbling

My old Coventry Eagle developed a speed wobble at around 20 miles an hour. I think it was probably all the off road miles it did before I’m pretty much sure something was misaligned. That shouldn’t be a problem with a new carbon frame but it’s worth trying with a different set of wheels to rule it out.

OTOH my TCR with 45s feels planted to me, and I weigh 10st

I have 42 and 65 SLRs on my propel.

No such issues.

I can’t see it the wind making it that wobbly. In my experience having ridden all sorts of bikes and deep wheels, the wind isn’t a wobble, it’s more a push. I have 65mm wheels and when going fast downhill, I may feel the front wheel being pushed, multiple ways to compensate for it, but it is a very definite feeling to a wobble.
I also use 40mm wheels as my winter all weather wheelset. In the 20/25mph winds we have recently they get knocked and I can feel the push but it’s really feels different than a wobble.
When my Reynolds wheels were out of true, they would feel like a wobble (front wheel) when going at speed and pulsing when braking (rim brakes).

If you get a real speed wobble try pinching the top tube with your knees it should stop the oscillation. Least it works for me.

Fortunately speed wobble is less common that it used to be – helped a lot by carbon frames which tend to be less flexible along their length. I remember coming down the Wicklow Gap in the pouring rain and nearly not making the big bend due to a viscous wobble. Opinion is its created by a harmonic resonance including the frame, forks, wheels and rider. I changed the forks on my bike at the time and got rid of it.

There’s definitely two different sensations at play here:

One is just a slight sideways push at “regular” speeds (eg on the flat) in sidewinds. I was half-expecting that from aero wheels though a little surprised at how “bad” it feels considering the rims are only 42mm. I’m expecting to get used to this and being able to compensate for it. (Although I’ve had the bike a few months, I haven’t been out on it much in windy weather yet).

The second sensation seems like a mixture of speed wobble and aerodynamic instability coming from the front end. I’m having to constantly make slight adjustments and can feel the gyroscopic forces yawing the bike. Next time I’m coming down a big hill, I’ll try the “grip top tube with knees” trick.

Your headset adjusted correctly ?

Your headset adjusted correctly ?

Yup, though maybe the stem isn’t the exact recommend torque as I don’t have a torque wrench and I’m reluctant to over-tighten against a carbon steerer…

Hi, I’ve read all the replies and I’m going to say something a bit different to everyone else.

Not all aero wheels are made equally.

A 42mm aero carbon rim does not equal a 42mm aero carbon rim. Different brands have small differences in the shape to help deal with crosswinds. If you look at Zipp with the tiny holes like a golf ball, Fast Forward which have an indentation under the braking surface and bulge out a bit away from that, and Vision rims which are different again.

I’m not sure what rims are on your bike, but most top end wheelsets can deal with winds pretty well. I have a pair of Vision 40s and a pair of Zipps also (202 on the front and a 303 on the rear… approx 35mm, 45m) both very stable wheelsets.

If you’re confident they are good wheels, then I’m not sure. The bike might have twitchy geometry…. or maybe try a bike fit? Maybe it’s not the bike for you but hate to say that, I haven’t ridden it though.

To the OP, I used to road race on those wheels and their 55mm SLR wheel, certainly no wobble at speed, either descending or flat. In fact the 55mm SLR wheels were pretty awesome.

Are you UK based? Any other wheels you can try on that frame or anyone else try your wheels?

Are you UK based? Any other wheels you can try on that frame or anyone else try your wheels?

Nope, Vancouver…

I have a buddy who wants to buy some aero wheels (so is interested in trying mine) so we should be able to swap them over (same axle sizes and centre-lock discs AFAIK) but that might have to wait til after Covid-19 self-isolation ends…

Speed wobble is frightening. I’ve never experienced it, but the stories from friends makes me paranoid.

One friend had this issue (different bike/wheels to you) and he fixed it by a combination of removing a spacer under the stem and just going a bit slower. I suspect the latter was more of a fix than the former. Interestingly, he never had issues until he got a pair of 45mm deep Mavic wheels – which suggest speed wobble can be caused by wheels.

When I first got my canyon ultimate I rode it from holyhead to London. Descending down snowdon I got a strange speed wobble. Turned out they hadn’t fitted the headset correctly.

May be worth checking stuff like that?

Is your stem long enough?

Is your stem long enough?

I think so.. it’s about 120mm I think, not a stubby mountain bike stem!

My fast carbon bike with 55mm wheels sometimes suffers from horrific speed wobble, and yes it can be terrifying. It seems to only occur in certain wind conditions though. I think its more a function of the head angle on the bike. If you have it slammed you could add a few spacers underneath the stem, it seems worse the more aggressive your position. I just dont take it out on windy days.

What bike are you coming off? The TCR is a full on super stiff race bike with race bike geometry so is twitchy. My mates got one, I had a Propel which felt similarly racey and twitchy so responds to every minute movement of the handlebars. Wouldn’t describe it as ‘wandering’ or wobbly As it only does what you tell it to do, it’s just super sensitive and super responsive. Have since moved onto a Scott Addict Endurance which is supposed to have a lore relaxed endurance geometry. Well it certainly is a bit less twitchy than the Propel and a much more relaxing and nicer ride though I wouldn’t say it is ‘relaxed’.

I put some 45mm aero rims on the Scott so compared two different wheel sets on the same bike and the deeper rims do respond to side winds slightly more than shallower rims, but nothing particularly alarming or scary and I’ve certainly not had anything that can be described as wobble. In fact at speed they feel more planted, but that could be that they are adjust a better wheel that I came from full stop.

Only ever has this when the wheels were out of true and balance.

Lift the bike off the floor and spin the wheel up by hand – does it want to spin round in a proper circle or does it wobble sideways or in an oval?

Are the wheels built well and fitted tightly? I know it makes no sense but my road bike used to get speed wobbles when descending in the drops and having the front wheel rebuilt cured it. It was true, but the spokes were not very tight.
The reason I mentioned being fitted tightly is that I can’t be 100% sure it was the rebuild or simply the act of removing/refitting the wheel which cured it.

Following on from retro83 above, is the bearing preload on the wheels set correctly (if it is adjustable)? I.e. grab the top of the wheel and try to move it side-to-side.

Can you try some different wheels?

See if it’s the same or not.

Simple test.

Going back to the headset, it might be worth checking the bolts on the stem move freely in the threads. I had steering issues on my Trek even though they were torqued correctly, turned out the top bolt had a bit of swarf trapped in it so wasn’t actually tightening on the steerer. This led to it pushing down on the headset which stopped the micro adjustments and self-correcting you and the bike make.

What bike are you coming off? The TCR is a full on super stiff race bike with race bike geometry so is twitchy. My mates got one, I had a Propel which felt similarly racey and twitchy so responds to every minute movement of the handlebars. Wouldn’t describe it as ‘wandering’ or wobbly As it only does what you tell it to do, it’s just super sensitive and super responsive. Have since moved onto a Scott Addict Endurance which is supposed to have a lore relaxed endurance geometry. Well it certainly is a bit less twitchy than the Propel and a much more relaxing and nicer ride though I wouldn’t say it is ‘relaxed’.

My other road bike (now reduced to turbo trainer duties since I purchased the TCR) is a similarly stiff/racy/responsive Cannondale SpeedSix though is has low end Shimano RS10, shallow rim alloy wheels. I love the “responsiveness” of both bikes but the SpeedSix is a lot more stable on fast descents.

Lift the bike off the floor and spin the wheel up by hand – does it want to spin round in a proper circle or does it wobble sideways or in an oval?

I’ve just picked the TCR up and held it in my left hand whilst spinning the wheels manually as fast as I can. Both “pulse” noticeably though whether this happens in all wheels, I don’t know. I wonder whether they are slightly out of balance (valve or clump of dried tubeless latex inside???). Anyway, both wheels seem true with little side flex and no obvious places where they are out of round.
They are both Giant SLR-1 composite factory wheels so whilst not top end, neither are they cheap Chinese eBay wheels either.

Following on from retro83 above, is the bearing preload on the wheels set correctly (if it is adjustable)? I.e. grab the top of the wheel and try to move it side-to-side.

I believe the hubs are DT Swiss 240 and I don’t think they have/need bearing pre-load (ie they aren’t cone hubs). Anyway, there isn’t any noticable lateral looseness…

Hopefully, I’ll get to try another fast descent later today and will report back on whether gripping the top tube with my knees helps!

Update:
I checked out the wheels and slightly tightened the axles (not that they were particularly loose…) then went up the lower part of a local ski hill road. Descending I hit around 65km/h (I was spinning out at that point) and no speed wobble! Granted, it was a windless day and I couldn’t get up to the higher speed I can do on the steeper sections…

Another’s silly headset question
Carbon steerers have the ally knurled bung in, not a s f. n
These can be fiddly to get right. My lbs guy reckond it was best to tighten the allen bolt with the stem nipped up already. This helps the bung grip the steerer tube.
Try wheel at 90 degrees and front brake on test for movement
I see a 60kmh test was ok, so sounds like the qr s were to blame although i am surprised
I ride a propel with 55mm spins and get the sidevwind push and in a 20kn + crosswind i have to lean the bike to windward and get low on drops, never had speed wobble
Tyre pressure v width could be a factor
Dried latex could be a factor
Pop off the tyres put rims in frame spin them. Up and check for wobble or out of round

my 2p.
I have recently switched from my winter Cannondale CADD4 with open pros and race guards (old school geometry) to my summer TCR advanced. The TCR is noticably lighter and twitchier. The wheels are a lot more sensitive to side winds and speed makes this more evident (and scary). I have found a combination of staying relaxed physically, only making gentle steering corrections and mental alertness works well with this bike. It’s not one for a gentle pootle…

Carbon steerers have the ally knurled bung in, not a s f. n
These can be fiddly to get right. My lbs guy reckond it was best to tighten the allen bolt with the stem nipped up already. This helps the bung grip the steerer tube.

I thought the idea of the bung was to compress and load the bearings so there was no play before fitting the stem which holds everything in place, if the stem is done up this won’t work. IIRC You can in theory set up the bung, tighten the stem and then remove the bung – it’s not there to hold everything in place

Yeah if you do the stem up first how will the bung compress anything?

/the outer allen bolt that squashes the 2 parts of the bung together prior to fitting the top cap bolt and tigjtening it down
The theory, and its just a theory is by nipping the stem up you can safely tighten down the 2 parts of the bung witjout fear of splitting the steerer tube. Then remove stem, fit spacers, top cap and tighten down.
Having red it back i failed in my explanation really badly and sound like a dumbo

What tyre pressure are you running?

What tyre pressure are you running?

80psi f&r (tubeless tyres, if that makes a difference)