Wheel stiffness???
 

When I'm out of the sadle cranking with all of the strength I have (but still produce little to no power), glancing down I noticed that the tire on my front wheel deflects side to side substantially. This leads me to wonder if the wheel stiffness even matters but apparently it does as many can attest to. Since I can't look back and down to see what my back tire is doing, I can only assume that the effect is even more significant. So what am I missing here?

It sounds like there is something wrong with your front wheel, or the skewer.

Couple questions:

What are the wheels and their history? Does either rub on the brake pads or anything else? Can you have somebody ride behind you and see if your rear wheel is deflecting?

You may know this, but power doesn't enter into the front wheel, it's just holding up a portion of your weight dependent on your position on the bike and the pitch.

Check your spoke tension and the tightness of your skewer.

My money is on skewer.

Spoke tension does not affect wheel stiffness unless the spokes go completely slack.

Things that do affect wheel stiffness:

A strong rim is stiffer than a weak rim. They used to make crazy light 280 gram alloy tubular rims back in the day, but they were so weak that you had to build them in 32 and 36 hole, which took away all the benefit of the weight savings. Nowadays rims can be fairly lightweight and strong allowing lower spoke counts to be used.

Spoke count does affect wheel stiffness though. More spokes will make a stiffer wheel and heavier riders are going to want to use a wheel with more spokes. Spoke type and thickness will also contribute to stiffness but can affect both weight and aerodynamics.

Hub flange spacing. Wider flanges make for a larger bracing angle. If you think to a triangle shape, a triangle with a wide base is a sturdier structure than a tall narrow triangle. Having the flanges spaced out as far as possible makes for a stiffer wheel.

Hub stability gets overlooked, and I wrote a blog about that recently:
http://blog.boydcycling.com/2013/05/hub-stability.html

And definitely do check to make sure that your hub is tight and also that your skewers are tight. If your hub is moving back and forth on the axle or if your wheel is moving around in the drop outs that won't be good for anything.

I had a similar problem and it turned out to be the skewer was not tight enough.

How does your hub put the DS hub bearing where the arrow is at the end of the axle? That's pretty cool. Does it use a bushing under the freehub? Most hubs have two hub bearings and then two freewheel bearings all on the same axle (viewed left to right). All stiffness comes from the axle. The only ones I know that have the hub bearing on the outside are DA hubs (and I'm not sure the newer ones do that). There's a new Alchemy hub that has the DS hub bearing in about the middle of the freehub. Because the hub body takes up room under the freehub, one of the freehub bearings is a bushing.

Great insight.

There are two freehub bearings and two bearings inside the hub. There is a spot where two bearings touch and having the bearing underneath the pawls means the freehub also has the bearings spaced out as far as possible. If both of the bearings are located on the right side of the freehub body then the left side of the freehub body (where the pawls are) can have a little bit of play in it. With our current design (and most hub designs) having the freehub spin over top of a bearing instead if a bushing is better for longevity. I know Mavic has had the bushing design around for a while and there have been a lot of reports of people having issues with that system.

I have my skewer on tight, but when I really crank on it, I can get the wheel to move around left and right. Depends on the wheel.

Sounds like Easton is doing something similar for 2014:

http://brimages.bikeboardmedia.netdn...Comparison.jpg

My CAAD 10 fork flexes enough to cause rims (all three sets I have) to contact the brakes in a corner at speed. Only on my CAAD.

Really? I haven't noticed that at all on my 10 or any of the 10's I've worked on. The steerer tube has a lot of flex IMHO, but the arms don't seem overly flexy to me, might want to have that checked out at your LBS.

I had an issue with my front race wheel while climbing or sprinting. It's radially spoked heads out and was all set to have it de-spoked and rebuilt heads in or possibly 2x. Then someone suggested looking at the skewer. I ditched the external cam skewer that it came with and replaced it with a good old fashioned internal cam (Ultegra) skewer. No more brake rub.

This.

Also, Neutrons.

http://everygramcounts.blogspot.com/...rade-time.html

What sort of wheels are they?

Here's another trick: sometimes ya think ya skewer's tight enough, but it ain't. Grab ya front wheel and give it a hard-ish wobble from side to side. If you feel more than just 'normal' flex, tighten the skewer.

Makes sense. Where pawls engage has the highest radial load to the axle and having a bearing under the pawls would be a more robust design.
When you say play, you are referring to radial clearance. For those interested, in any design the farther outboard the supportive bearings, the better restraint of the hub or freehub or any body relative to the axle. Because there is freedom between a wheel hub and freehub, ideally you want the bearings as far outboard as possible for each. Having inboard bearings or bushings in particular is particularly problematic on a freehub because of asymmetric loading of the cassette/freehub by change in chainline. An unrelated wheel analogy but cycling related is...why outboard bearing cranks work so well.
Thanks for sharing your knowledge here Boyd.

I did that. Even road a couple other new one and they are pretty flexy. Take the wheel out and pull around on them a bit...sort of scary and nothing like my Klein but that's pretty old school carbon. Could be that I'm that much heavier than you as they never noticed it either. I also keep my brakes pretty close to the rim (about .5mm) so it doesn't take much I guess. Their suggestion was to loosen up the brakes.

When you take things apart and start pushing, pulling and twisting, it's really amazing how much flex there is in just about everything. Put it all together and stick a fat a$$ on it and something got to give:-)

Fair enough! I have always noticed with all my Cannondales an extra amount of flex in the front forks focused in the steerer tube, mainly when the front brakes are grabbed. I do know on the CAAD10 they were worried about added front end stiffness hence why they raked out the fork so much, so that could add to it. I also run my brakes pretty loose, not for any reason other than that's how I like it, so that makes sense.

Yeah, I like to have my brakes right there. I tend to be able to feather them more that way in a hurried stop;)

This is best article on wheel stiffness and many of the myths.

http://www.slowtwitch.com/Tech/Debun...ness_3449.html

Crap! I just re-read my post and I wrote it wrong. I meant to say that the tire deflect side to side, not the wheel.

Well that's a bit different.

What is your tire size, rim width, psi (f & R) and body weight?