General Discussion Triathlon Talk » Descending felt so wobbly today! Rss Feed  
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2015-02-05 6:46 PM

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Master
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Los Angeles, CA
Subject: Descending felt so wobbly today!
Hello everyone!

I borrowed a friend of mine's HED 60/90 wheelset and installed them on my 2012 QR Illicito and took it for a ride during my lunch break today. It was windy but not super windy out there, 5-8mph winds with gusts around 10-12mph. I didn't feel much wobble heading out but on my way back the conditions changed drastically.

After turning around at the apex of this long climb (2.5 miles?) I started my descent. I got to around 30-35mph and started feeling alot of instability (wobbling?) that I had to ease up on my pedaling and get out of aero to maintain some sense of confident control. I still tucked myself down a bit but the constant wobbling really freaked me out. It got to me so much that I let myself cruise down without pedaling the last third of the hill. I've taken this hill many times before with regular training wheels (Felt TT4s) and didn't feel any of what I felt today.

Before riding, I made sure everything was tight and my rear limit screws are set correctly.

Is this normal? This is my first time ever using a racing wheelset this week with some windy conditions.

Thanks,
Roland

Here's a pic of my bike.

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2015-02-05 7:43 PM
in reply to: kloofyroland

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Subject: RE: Descending felt so wobbly today!

What type of wobbling are we talking about.  Wobbling like vibrations or wobbling like every time the wind gusted you felt the bike move laterally?

If the wobbling was wind related, then it's likely just getting used to leaning into the wind instead of trying to actually counter steer into the wind.  IOW, when the wind blows from the side, don't turn the handlebars...just shift your weight. 

Now if you're talking about wobble in your wheels not related to wind, then I would make sure that the wheels are true.  Spin them while on the bike and watch the gap between the brake track and the brake pad and see if there is any movement.  Next I would make sure that the tires and tubes are mounted properly and evenly.  Again, spin the wheels and see if there are any differences in the gap between the top of the tire and your seat tube and chain stays.

2015-02-06 12:25 AM
in reply to: Jason N

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Master
2759
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Los Angeles, CA
Subject: RE: Descending felt so wobbly today!
Originally posted by Jason N

What type of wobbling are we talking about.  Wobbling like vibrations or wobbling like every time the wind gusted you felt the bike move laterally?

If the wobbling was wind related, then it's likely just getting used to leaning into the wind instead of trying to actually counter steer into the wind.  IOW, when the wind blows from the side, don't turn the handlebars...just shift your weight. 

Now if you're talking about wobble in your wheels not related to wind, then I would make sure that the wheels are true.  Spin them while on the bike and watch the gap between the brake track and the brake pad and see if there is any movement.  Next I would make sure that the tires and tubes are mounted properly and evenly.  Again, spin the wheels and see if there are any differences in the gap between the top of the tire and your seat tube and chain stays.




I think it was a feeling of high frequency wobbling. I was not pushed around that much but when the wind blew pretty strong, I definitely felt the sideways push. I think you put it correctly Jason, the instability felt like vibrations. I put the Illicito on my bike stand and the wheels spun true. I'll remove and install the tires and tubes after my test ride on the same route with the wheels on my roadie and see how that feels first. I really hope it's not due to my Illicito frame not having a seat stay by design causing the instability.

Thanks,
Roland
2015-02-06 5:22 AM
in reply to: kloofyroland

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Pro
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, New Hampshire
Subject: RE: Descending felt so wobbly today!
Two things that you should do/check. More than likely, the vibrations came from you tensing up (which is quite normal when you change something major like the wheels). Try another few rides and try to relax the grip, it's probably that simple...

The other thing you should check is your headset. If it's just ever so slightly loose, you tend to feel it much more with deeper wheels than with shallower rims (due to the increased pressure of the larger surface area for the wind to pass by)
2015-02-06 6:13 AM
in reply to: kloofyroland

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Master
3205
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ann arbor, michigan
Subject: RE: Descending felt so wobbly today!
The other thing to think about is the dreaded "speed wobbles."

The theory is that most bikes have an oscillation frequency that is most pronounced at a given speed (different for every bike set up). This is the speed that the bike will suddenly feel wobbly at. By changing your wheel set up you may have changed the oscillation speed at which you feel the speed wobbles from your bike with training wheels.

The trick is to not panic but to change something on the bike when this happens. You can slide backwards or forward in your seat. You can press your knee against your top tube. You can get up out of aero. Just do something to change you and your bike just a tiny little bit and it almost always goes away.

Two years ago, at Tahoe, I was doing a practice descent from Brockway Summit and my bike suddenly felt like it was all over the place. It really felt like riding my bike on smooth ice; that very unstable, falling is imminently possible, sensation. I was going about 45 mph and it was terrifying. When I got to the bottom I had some vague recollection of reading about speed wobbles in the past so I rode back up and did it again. This time when I felt the bike start to get squirrely, I rested my knee against the top tube and it magically, instantly, went away. It was pretty cool and gave me confidence that I could descend fast on race day.

Now, whenever I descend and get to the speed where I am not pedaling any longer, I automatically place my knee against the top tube as a preventative measure.
2015-02-06 6:40 AM
in reply to: kloofyroland

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Subject: RE: Descending felt so wobbly today!
Originally posted by kloofyroland

Is this normal? This is my first time ever using a racing wheelset this week with some windy conditions.



some info here

http://www.beginnertriathlete.com/discussion/forums/thread-view.asp...


2015-02-06 7:31 AM
in reply to: marcag

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Master
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...at home in The ATL
Subject: RE: Descending felt so wobbly today!
An oldie but still a goodie - this video shows just how easy it is to induce speed wobble/shimmy, but more importantly how easy it is to recover if you don't panic: https://m.youtube.com/watch?v=xODNzyUbIHo. Years ago I had a Trek 5200 OCLV that would do it every time I hit 42mph on a descent - I learned to ride through it utilizing a lot of the tricks in the thread Marc linked to above.
2015-02-06 8:52 AM
in reply to: 0

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Extreme Veteran
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Greenwood, South Carolina
Subject: RE: Descending felt so wobbly today!
Great thread.

I ride some nice steep hills and never had the wobble issue until I put some new race wheels (Zipp 808) on my bike. My thinking was the difference in the weight of the race wheels compared to my other wheels. It does make you a little nervous and a little cross wind doesn't help any.
Never had any fear flying down hills before the ZIPP wheels but I had some fear in some races with my ZIPP wheels. There were a couple of hills in the Louisville IM race that were a gut check with the ZIPP wheels and the wobble effect.

Edited by GODAWGS 2015-02-06 8:53 AM
2015-02-06 9:49 AM
in reply to: marcag

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Master
3205
20001000100100
ann arbor, michigan
Subject: RE: Descending felt so wobbly today!
Originally posted by marcag

Originally posted by kloofyroland

Is this normal? This is my first time ever using a racing wheelset this week with some windy conditions.



some info here

http://www.beginnertriathlete.com/discussion/forums/thread-view.asp...



Ha. My story changed a little bit from telling to telling but the basic gist was the same........
2015-02-06 9:59 AM
in reply to: wannabefaster

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Subject: RE: Descending felt so wobbly today!

Nothing to add on the wobbles.  Just wanted to say I think those wheels look great on that bike.  Awesome looking setup.  Hope you get things worked out.

2015-02-06 1:15 PM
in reply to: kloofyroland

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Subject: RE: Descending felt so wobbly today!

Roland, no idea if it's speed wobble or not, bu I can relate that every time I put the H3 on the front (i only use it in races) i am amazed at the amount of instability I get when riding it, even in what I would consider light winds.  I eventually get used to it, and if I rode it all the time I probably wouldn't even notice.



2015-02-06 9:08 PM
in reply to: wannabefaster

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Master
2759
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Los Angeles, CA
Subject: RE: Descending felt so wobbly today!
Thanks guys! I remember reading that thread about wobble.

My top speed was about 35 mph and that's so interesting how aero wheels can have this kind of effect. I used them on my roadie today (on the same route) and I felt the same high frequency wobbling. This time though, I felt it more in the front much like ChrisM's situation when he swaps his wheels out for racing. I verified everything was tight up front. I tried putting my knees on the top tube but that didn't help any.

The wheels are true. Maybe the bearings are worn out???
2015-02-06 9:08 PM
in reply to: popsracer

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Master
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Los Angeles, CA
Subject: RE: Descending felt so wobbly today!
Thanks Popsracer!
2015-02-06 9:15 PM
in reply to: ChrisM

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Master
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Los Angeles, CA
Subject: RE: Descending felt so wobbly today!
The next thing I'm gonna try is re-verifying everything is tight up front and use a regular front wheel and keep the race wheel in the back and see how that feels on the same descent.
2015-02-10 3:40 PM
in reply to: kloofyroland

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Master
2759
20005001001002525
Los Angeles, CA
Subject: RE: Descending felt so wobbly today!
Originally posted by kloofyroland

The next thing I'm gonna try is re-verifying everything is tight up front and use a regular front wheel and keep the race wheel in the back and see how that feels on the same descent.


Update!

So I re-verified everything was tight up front and used a well used Mavic Krysium front wheel and took my bike out again for a lunch break ride. This time I felt no problems at all and the wind was stronger today too! I felt no fear and stayed in aero, wow! Very interesting.

What else could it be? Maybe the front wheel needs a tune up? They are true and I tried wiggling the bearings by hand and they don't wiggle.

Thanks,
Roland
2015-02-10 4:40 PM
in reply to: kloofyroland

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Champion
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Tacoma, Washington
Subject: RE: Descending felt so wobbly today!

It may just be the interaction of the wheels (yes, both of them) with the bike.

My own experience:

When I first got my titanuim Softride back in... 1993? Whenever... I had them put a Trek carbon fork on it -- lightest available at the time. I raced it in crits and road races, no problem. First TT, though, was a long one (36 miles if I remember right) which included some pretty good hills. Well, on every downhill, every time I got over 30 mph, the front end would go into a rather violent wobble. This was on Specialized Tri-Spoke wheels front and back. I'd used them on my Barkley Softride (with Tange aluminum fork) many times with no issue. What was up with that?

I swapped out the fork for a Kestrel EMS, and the problem went away. Seems the fork was just too soft.

BUT... I did have a lot of problems in strong crosswinds.

Fast forward several years, and I'm back in triathlon, different frame, 650's instead of 700's... Anywho, I'm running a Hed 3 up front and a Renn disk in the rear. Rock stable, even in some pretty strong winds. Something to do with the aerodynamic center relative to the steering axis.

So upshot to this? It might be just the way that wheel reacts with that fork, it may be that the fork is "soft", and it may be that you need a deeper rear wheel relative to the front (by reducing the depth of the front you've essentially accomplished the same thing).



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