.

I went out again up a different big hill and “breezy” conditions and, holy f++k, this bike is sooooo unstable it’s frightening.
Didn’t make any difference whether I was on the drops or the hoods, whether I gripped the top tube with my knees or not, whether I was tense or relaxed or whether I soft pedaled or not (I’m spinning out around 60km/h anyway).

For context, the wobble started kicking in around 55km/h and the bike only stabilized when I braked down to around 50km/h. As soon as I let off the brakes, the wobble kicked in again.

According to Strava, the wind was NNW @ 12 km/h so not exactly blowing a gale. The road surface is pretty good, it’s very wide (3 North American lanes wide) and had no traffic whatsoever (it’s closed to vehicles currently) and is mostly sheltered by trees. The road is mostly straight with a couple of very wide hairpins.

I’ve been up and down that road multiple times on my Cannondale previously and never experienced the same problems even on windier days.

https://strava.app.link/h6FBG9hDF5

Strava shows my previous best time on the descent being 65.5km/h (Cannondale) yet I was shitting myself down the same segment at 46.5km/h…🤔
(The KOM is 77.3km/h…😳😳)

It sounds to me like you may be expecting it and subconsciously causing it.

Do you feel yourself tensing up as the speed gets higher?

This happened to me after my experience earlier in the thread and it took me ages to get over it.

Just out of interest, what was the temperature when it happened?

I did loads of reading on the subject when I was going through it and it can happen more when temperatures are cooler because you may shiver slightly when going fast down hill on cold days.

Gripping the crossbar with my knees made no difference at all.

It is incredibly frightening and dangerous when it happens because the bike is out of control, I would veer to left or right whilst braking until the bike was back under control.

Lowest temperature was 9°C at the top of the hill and I had a thermal tee shirt + long sleeve fleece jersey + windproof jacket and whilst I wasn’t warm, I don’t recall being cold enough to shiver.

Based on the GCN video, I’m wondering whether my frame might be too small…(it’s a carbon 2020 Giant TCR so Im confident it’s stiff enough.) According to Giant’s size charts, I’m slap bang in the middle of the overlap between a L and XL frame and I opted for the L…hmmm.

I’ve got some spacers under the stem so I might try dropping the front end a little (though not much as my back will suffer).

I went through all of this, changing wheels, stem length and height, saddle height, pretty much everything you read about online I changed. I finally realised that because it had happened twice for no apparent reason I was getting very nervous at high speeds and changing the damping of the bike by tensing slightly.

Took me ages to get over it. Riding my MTB on the road helped, in fact it was doing that that made me realise I was the problem. It was so planted that I was reaching speeds way in excess of what I would even dare on a road bike at that time.

I bought a gravel bike and put 45mm road tyres on at low pressures and gradually improved my confidence.

I can now descend at 45mph+ on 23mm twitchy road bike.

I keep meaning to write an article on what I went through as it may help others.

Just back from a spin on my tcr, which rarely gets used. Today’s ride reminded me why…it’s not a relaxing ride, and I have to agree with the op, descending is utterly terrifying, it feels ridiculously unstable. Contrast it to my defy, which is a magic carpet ride, and far more relaxing to spend any time on.

I’m not saying the tcr isn’t fun, it is, in the same way as riding on the back of a tiger would probably be fun…you just don’t want to do it that often …

Have never ridden a Giant but from comments above not sure I’d want to…the best road bikes are fast, stiff but also have handling which should be rock solid at speed, and they do differ. Given at this time it may be hard to get a bike shop to check it over, I would want to iron out any possibilities that there’s something wrong with the bike – check the alignment of the frame, a bike shop will have a tool to do this but you could carefully eyeball the bike from the front and see if the wheels appear to line up perfectly in plane, they don’t always and inconsistencies can wreak havoc in high speed handling. Likewise wheel balancing to lesser extent, put the bike in a work stand and spin the wheels at speed – most wheels will have a bit of a wobble even when perfectly true and round due to balancing..wheels where for instance the carbon rims aren’t made very consistently in the mould might exhibit a violent wobble in the stand, if you think own brand rims differ much from cheap Chinese options then you may be disappointed. If there’s violent wobble in the stand then this is one of many factors that can contribute to speed wobble, I mean like the whole bike bucking in the stand as the wheels spin…really good well balanced wheels are smooth in this scenario, ie: some manufacturers go to the length of weighted inserts to counterbalance the valve stem. A big dried lump of sealant could just about have this kind of effect too.

Some of the comments on the function of the bung in a carbon steerer tube have me slightly worried about the safety of peoples bikes…read the manuals please peoples. No one ever wants their steerer tube to snap at the stem, ever, you do not want to rub your face on tarmac at 40mph. Carbon hates compressive force and the bung is there to support the tube against the forces from the correctly tightened stem…without this set right its tarmac-face Russian roulette.

Strange. I had a tcr for a bit. Rode like a well planted bike. Climbed really well , won me the club hill climb champs on one.

Bought a propel and despite the geometry being more aggressive it’s still a delight to ride compared to the stuff of yesteryear.

Fast stiff handles a dream -with one caveat….if you can’t ride it fast you won’t enjoy it. Its not a bike for bimbling about on. It wants to be ridden fast and it wants to be driven into corners.

If you can’t commit you probably do want a more relaxed geometry bike that will forgive you.

My friend had this problem with Giant aero wheels (SLR 0 I think). Will check for the exact cause but I think it was one of the tyres. He got it fixed easily, anyway.

Nudged 80km/h on my TCR in fairly windy conditions on Thursday morning, felt fine. Not entirely convinced it’s the bike tbh

Not entirely convinced it’s the bike tbh

Haha…as the OP, I’m not being self-defensive here but…

My TCR has replaced a similarly racy and stiff Cannondale SpeedSix, though the SpeedSix has cheap Shimano non-aero alloy rims rather than 42mm deep carbon rims. I’ve been road riding for 20+ years so I’m not a novice and the bikes are comparable. I’ve even checked the geo charts of both and they are quite close though I doubt the TCR is less stiff than the SpeedSix.

I’m comparing riding the same roads in the same conditions. I’ve ridden up the same big, wide, open ski hill access roads about 10 times in the last month.

On Thursday evening, there was NO wind and the bike was rock solid (though it still wanders so needs to be brought back into line). Saturday was a little windy and I felt the bike start to shimmy around 55km/h but stabilize once I dropped some speed.
Someone further up this thread suggested gripping the top tube with my knees so I tried that but the TCR has a dropped top tube so that’s a bit awkward. I found that if I pressed my leg quite hard into the top tube (and compensating by leaning the bike slightly into the leg) then the shimmy eased off and the bike felt much better at up to ~ 60-65km/h (about terminal velocity on those roads as they are only around 8%).

So, the “leg-being-pressed-into-the-frame” technique suggests it’s dampening some imbalance (whether from lack of frame stiffness <unlikely>, aerodynamics and out-of-balance wheels)…

Anyway, I’ll get the shop to check the bike out…

Hi, just wondering if the cause of the speed wobble was found? Are you enjoying the bike now? thanks

As the OP, the short answer is no, I still don’t really know what the “problem” is. I suspect a steep head angle but I have no way of proving that and I don’t have a second set of wheels I can swap out to do back-to-back comparisons against.
For sure, pressing my left leg into the top tube seems to damp down any vibration and the wobble eases…

I do enjoy riding the bike but have learnt to be cautious on descents or places where a cross-wind is likely

I’ve never ridden the Cannondale so can’t comment on that but find the TCR quite a smooth ride. Don’t get me wrong it’s responsive but not twitchy. I’ve ridden some road bikes that are too responsive for my liking that any input sends you off in a different direction but even then it’s not wobble

I would be check that

– Hub bearings are running freely but not loose

– Tyres are seated correctly on the rim ie you should be able to see the bead following an exact circle to the rim. That the tyres are are seated correct left to right ie spinning the wheel looking from above they look true

– Headset moves freely but not loose

– rims are not massively out of alignment in all axis

The fact is the TCR is a very competent well rested bike and doesn’t normally have these issues

If it’s new take it back to the shop and get them to ride it.

Finally when I moved from shallow rims to 50mm I really noticed it for about the first 3 rides, now I don’t at all

Cycling tips said the following in their review

Such flex between these two ends of the front triangle can go a long way to creating a bike that offers a nice ride quality, but it does detract from how the bike feels in an urgent surge of power. More importantly, both Andy and I each experienced a one-off bout of speed wobble in gusty conditions at over 75 km/h that we then couldn’t replicate (and I haven’t been able to get back to the same seated coasting speeds around my local roads in Sydney). James Huang experienced a similar thing on his stiffer TCR Advanced SL test sample and claims to have solved the issue by balancing the wheel.

That shouldn’t be a problem with a new carbon frame

It shouldn’t, but I wouldn’t have a huge amount of faith in that 😉

I wonder if you contacted the Peak Torque guy on YouTube if he’d be interested. This type of engineering/aerodynamic type query would be right up his street. Iirc he has a tcr too.

I had a TCR Advanced Pro and it was one of the most stable bikes I’ve had at speed . I decided to upgrade to the TCR Advanced SL as I thought it would be even better . I was wrong , it was too twitchy and although I didn’t experience speed wobbles on it I didn’t have as much confidence at speed on it. I think confidence is a big factor as I have had speed wobble problems a few years ago and it takes a long time to learn to flow with the bike again . Best bike for stability , feel etc I’ve ridden was a BMC SLR 01, absolutely rock solid at speed and could be thrown into any corners on any surface .

I have the same bike (or at least the 2021 version of it) – got it last summer.

A couple of weekends ago I went out on it and there was a foehn wind blowing (I live in the mountains). There were a couple of spots where it was blowing strongly across the road and it was really scary! Until then I had not been out in any strong winds. It has made me consider buying another set of wheels that are not deep-section for windy days.

Thanks for the responses. I’m basically on the market to replace my 2009 Cannondale CAAD9 Tiagra and have narrowed it down to a TCR Advanced pro 1 disc or a Specialized SL7 Expert. I love very fast descending and have never had an issue on my CAAD9. The Specialised would cost me £550 more with the main advantage of it having a threaded BB and integrated headset. Although from what I understand the headset spacers cannot be put about the stem so the steerer would have to be cut. I’ve ridden a friends SL7 briefly and got on well. No chance of riding a TCR as they sell out locally before the stock comes in. Has anybody ridden both?

I’ve just bought the latest TCR Advanced 0 and I have to say it’s probably the best bike Ive ever ridden. I went through all the reviews before hand of which there are plenty & they are exactly right. In respect to descending I live in Bucks very close to Whiteleaf hill which is rapid very steep short descent – the bike is so fast going down it took me by surprise but I gradually got used to and it’s no problem and handles the speed easily plus the disk brakes are amazing. The caveat to this though is that I would concur with those that have said confidence might be an issue as I was a very capable descender with top 10’s on Strava leader boards but last year I had a couple of spills one in winter (hit some ice on a descent but pretty slow & one high speed on a corner hitting loose gravel) both really hurt me and I know that they took an impact on me psychologically. I’ve also experienced a speed wobble and on deep rims (pre sram Zipp 404s) but also had gusts catch deep rims wheels – in my experience they are two separate issues.

At 6’4″ youre going to have a higher centre of gravity than many. Does this occur more on the hoods / less on drops? Perhaps try getting into a lower position on descents to drop your CoG a bit.

Or get a dropper post!