Shimano Dura Ace C24 for 1.92m 90 kg rider?

I'm 80kg, 1m75 and have had da c24's for last 2 years. Absolutely no problems, seem fast and comfortable but I too get a wobble but only over 52mph, seem fine up to that point. It is very worrying when it happens though.

Holimoli wrote:

I'm 1.87 and 90 kg and own some Dura Ace C24's. They've been really great untol today descending a hill. I reached 60 kph and the front wheel started to shimmy. From what I've read this is due to a combination of factors all acting at the same time. However, a couple of factors cited were frame length and saddle height - I.e. more likely to happen if you are tall. I guess if you ride some wheels that offer more comfort - like the C24s - then this is probably happening because they flex a little and the more you weigh the more they will flex.

Fortunately I managed to bring the bike to a stop, although for a bit I really did think I might crash. A change of shorts was definitely in order.

As I said, I don't know if the cause was just the wheels, weight and speed combination. there might have been a couple of other factors that added to those created the wobble. however, it was disconcerting and it might take some time before I descend at that speed again.

You had a classic speed wobble - it's caused by air flow over the bike causing the front wheel to oscillate. Whilst wheels are a factor (if you change the wheels, you might find it happens at a different speed or not at all) it's not transferrable to another bike and rider, since the airflows over that other bike and rider will be very different.

I'm a bit under 80kg and have used my C24s extensively, including commuting in the winter on a steel bike with a decent sized bag - my total weight (me, bike, bag) was prob not far off that of the OP and I've had no issues either. The wheels never feel flexy - I doubt you'd have any major flex issues.

step-hent wrote:

You had a classic speed wobble - it's caused by air flow over the bike causing the front wheel to oscillate. Whilst wheels are a factor (if you change the wheels, you might find it happens at a different speed or not at all) it's not transferrable to another bike and rider, since the airflows over that other bike and rider will be very different.

Yes, I'm not going to dispute this. All I can say is that it's the same bike and fit that I had before over many miles without problems, but when I changed to the c24s I started getting the speed wobble. As you say my particular combination of factors won't be the same as somebody else's but I'm pretty clear that the change of wheels is what has introduced this problem for me.

Holimoli wrote:

I'm 1.87 and 90 kg and own some Dura Ace C24's. They've been really great untol today descending a hill. I reached 60 kph and the front wheel started to shimmy. From what I've read this is due to a combination of factors all acting at the same time. However, a couple of factors cited were frame length and saddle height - I.e. more likely to happen if you are tall. I guess if you ride some wheels that offer more comfort - like the C24s - then this is probably happening because they flex a little and the more you weigh the more they will flex.

Fortunately I managed to bring the bike to a stop, although for a bit I really did think I might crash. A change of shorts was definitely in order.

As I said, I don't know if the cause was just the wheels, weight and speed combination. there might have been a couple of other factors that added to those created the wobble. however, it was disconcerting and it might take some time before I descend at that speed again.

And I was thinking to get some C24's. I was just about fed up with the speed wobble from my Fulcrum Racing Zero's. It's happened so many times, and usually on rough roads. It's worse if it's windy.

I'm 1.84 and 87 kg. Perhaps the low spoke count is a factor (16 for the Racing Zero's front wheel), perhaps they are not laterally stiff enough. I put a Giant P SLR 1 front wheel on (which has 18 spokes).

Over the past 3 days I rode the same route. After an hour on that route there is a descent which in the past I've hit 47 mph.

Day 1 - P SLR 1 front wheel, Racing 0 back wheel - no shimmy

Day 2 - Racing 0's front and back, same route same weather - shimmy

Day 3 - P SLR 1 front, Racing 0 back, same route same weather - no shimmy

The speed on descent:
Day 1 - 40.5 mph
Day 2 - 38.5 mph
Day 3 - 38.5 mph

I thought the Racing Zero's bladed spokes were making the situation worse, especially in the wind, but the C24 doesn't have bladed spokes...Oh well, the search continues