A Wheel Education

cornerblock

I have just spent most of the day fettling, which has involved working on 3 bikes. Moving bits from one bike to another, rebuilding the commuter and stripping down what was the best bike. When I finally finished, I had the rebuilt commuter and a recently purchased CAAD 10 both upside down and along side each other.

The commuter, an old Giant FCR, great servant and done thousands of miles, now has a 2 year old pair of Mavic Aksiums on it. While the CAAD 10, a brand new bike has a 1 year old pair of Dura Ace C24 wheels now adorning it. While turning the cranks I noticed that the Aksiums seemed to spin far longer than the Dura Ace C24's. I thought that the Dura Ace wheels being a lot more expensive, and reputedly better wheels, would outspin the Aksiums. I timed both wheels by turning the cranks one revolution, and every time the Aksiums span for around 15-20 seconds longer than the Dura Ace wheel.

Now apart from proving that I have become a proper sad case! And probably need to get out more. Can anybody explain why the seemingly lesser wheel should appear to have a more impressive spin than the better wheel? Or am I missing something, I realise my test is not exactly done under lab conditions, the wife has been very patient with me for turning our hallway into a workshop! Too cold outside.

I suppose my main concern is, are the Dura Ace 24's faulty in some way. Surely they should spin longer than the Aksiums.

Thanks for listening.

oldraver

Haha not sad enough to google the relevant weights but, a heavier wheel is more resistance to deceleration, ( fly wheel effect ).Maybe the bearings in the Aksiums are in better shape than the Dura Ace bearings? Maybe it is marketing that leads to the higher price? We both appear to be sad cases? :-)

oldraver

Ps were both wheels being spun on the same size sprocket given that according to Mr Newton F=MA.

cornerblock

oldraver wrote:

Ps were both wheels being spun on the same size sprocket given that according to Mr Newton F=MA.

They were. And give or take, with the same force on the crank. I am currently swapping tyres over! I am getting saddder by the minute.

oldraver

I like a man who takes things seriously.
You will of course have checked that the bearing preloads were the same & repeatable.

cornerblock

Not sure, I suspect the wife will want the hallway clear of tools, bikes and greasy rags by the morning!

huuregeil

Cornerblock,

There are lots of factors in play - the short of it is not to worry! Bearing drag is of the order 1W per wheel, plus or minus even 50% is not going to noticeable on the road. Some factors: unloaded spinning is not the same as loaded spinning (this is the big one, the minute your bearing gets subjected to different loads, it's performance will change - better bearings/hub designs are less variable with respect to loading pattern); the mavic bearings are 2 years old vs new dura aces (i.e. packed with grease and not subject to any wear); the sealing is likely different. You can, if it bugs you, adjust the dura ace so it spins more freely, possibly at the expense of more wear. I wouldn't bother - get them on the road and enjoy them!

Regards,

cornerblock

Thanks huuregeil, that all makes sense. Just seemed odd to me that the Mavic wheel would spin for so much longer, in my technical testing area, upside down in the hallway! I will not worry too much, but out of curiosity how do you adjust the wheel to enable it to spin more freely. Had a look on the Shimano site and the technical documents that I downloaded were not much help.

Thanks.

Wirral_paul

As Huuregail says, what you're seeing on an unloaded bearing by spinning your wheels on an upturned bike bears little relation to whats happening under loaded conditions. Too many variables to use a simple unloaded spin to determine bearing condition / adjustment. By adjusting the wheels to spin more freely, you may well end up with lateral play and hence wear the bearings out / end up with brake rub.

Maybe drop the chain off and listen for any signs of wear in the bearings. If there is none and no obvious play then i'd leave well alone.

cornerblock

OK, thanks Paul.

Twostage

When I put my bike in the bike stand this afternoon after a while I noticed the front wheel was slowly rotating about a quarter of a turn one way, pausing and then rotating back again. It did this for a couple of minutes. Smooth rollers these halo aerorages.