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Wheel spin down results

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Wheel spin down results

Old 04-29-20, 08:22 PM
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Miles2go
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Wheel spin down results

I recently replaced an older carbon race bike and suspect the much older wheels are faster...and/or more efficient.
Funny thing is, I've pulled these 2007 Campy Neutron wheels forward to a total of 3 bikes because it they've always been fast and reliable, but now switched from Campy to Shimano. Spin down tests or coast down tests is how I compared.

The new wheelset is a Dura-Ace 9100 C24 and after over 1,000 miles, If I lift the front the front wheel and spin it, it will stop spinning at a consistent average of 1:15 seconds,
and I'm now being passed on big hill coast downs, when on rides with buddies.
The old Campy wheelset using ball bearings consistently spins for 3:45 or longer,
and even though I'm a lightweight, I'm rarely out coasted on descents.

I never would have guessed that in this day, I could buy a well-regarded wheelset and have them turn up slower than my 2007 wheels with a serious amount of miles into them.
So how do I ensure my next wheels are as efficient as the old Campy wheels? Of course you should be able to see the implications of the difference as applied to a long race. One wheelset is taking more of your power to maintain the same speeds.
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Old 04-30-20, 08:46 AM
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New wheelset = new seals and grease in the bearings.

New seals are draggier than old worn-out joints. New grease is stickier and more plentiful than in old hubs. Heavier wheels will also spin longer, but I don't know the specs of either wheel you have. Also, the wattage losses seen in hub drag is next to nothing, so unless it bothers you, I suggest you pull the Shimano hubs apart, clean them up, and put a small amount of lighter grease in them.

Loose-ball hubs can be set "loose" then the QR will take up that last bit of slop to make them perfect. I used to ride with a Master TT national champ that ran a Dura-Ace front hub and Zipp Sub-9 disc rear. He sanded the seals back on the front hub so there was no contact between the seal and the hub body, then he pulled all of the inner seals off of the ceramic bearings in his rear hub and shaved the cassette body seal. He used Triflow chain lube on the bearings and rear hub pawls. He claimed his front wheel would spin for 20+ minutes, then spend about 25 minutes dipping back and forth until the valve came to a rest at the bottom position.

Obviously an extreme example, but still neat.

Here in the PNW people cling onto Chris King hubs like they are a gift from the almighty himself. I had them on a MTB build once and was amazed at how draggy the sealing system is. Spin down tests on new CK hubs is shockingly bad. Like, legit 7-8 seconds.
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Old 04-30-20, 11:32 AM
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Originally Posted by Miles2go View Post
and I'm now being passed on big hill coast downs, when on rides with buddies.
120rpm on a 53/11 is 45mph. You all coasting down hills at faster than 45mph?

Either way, at those speeds if you do reach spinout on your drivetrain and reach terminal velocity then your aero resistance is vastly vastly more important than a half or one single watt in the wheels. That, and your body weight for going downhill.
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Old 04-30-20, 11:49 AM
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Unloaded coast down measurements of a wheel is dependent primarily on rotating mass of rim and tire. If the bearings are broken in and good.the heavier wheel should spin longer. Same effect coasting downhill, But to a lesser degree. Ironically cheap heavy steel rims with mountain bike tires should coast much longer unloaded then then a good carbon fiber rim with 25 mm racing tires, and to a much lesser degree even riding.

The point of low rotating mass is to reduce the amount of energy required to accelerate the wheel and bike. Those big heavy wheels and tires that coast so well significantly reduce acceleration, While the extra energy used to accelerate that mass is only lost when you brake, It's not going to help someone in a race when it's often that last few hundred meter sprint that determines the winner, Or coming out of a turn when we slow down. Also when climbing the heavier wheels are not your friend. For recreational cyclist though it's not that important.

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Old 04-30-20, 01:56 PM
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Originally Posted by Cypress View Post
New wheelset = new seals and grease in the bearings.

New seals are draggier than old worn-out joints. New grease is stickier and more plentiful than in old hubs. Heavier wheels will also spin longer, but I don't know the specs of either wheel you have. Also, the wattage losses seen in hub drag is next to nothing, so unless it bothers you, I suggest you pull the Shimano hubs apart, clean them up, and put a small amount of lighter grease in them.

Here in the PNW people cling onto Chris King hubs like they are a gift from the almighty himself. I had them on a MTB build once and was amazed at how draggy the sealing system is. Spin down tests on new CK hubs is shockingly bad. Like, legit 7-8 seconds.
I always found the stuff that shimano uses in their hubs, even DA to be on the tacky side and not very slick feeling and always replace it with finishline white lithium grease for something faster, there is a noticeable spin difference.

As for CK, even broken in they tend to fail the unweighted spin test, don't know if its just the design of the races but they do terribly in a truing stand spin test. On the pavement is another story. I worked for a shop that had a nationally ranked BMX team and some of the kids really loved the CK hubs and some of the naysayers pointed to the spin test as proof they were over rated. We did a weighted test on the road swapping just wheels, so same bike, cog and tires, weighted the CKs always coasted further. I typically out coast anyone with me, partially due to gravity having a greater affinity for me, though I'd assume wind resistance balances some of that, while the hubs just seem to spin forever. Other positive was recently overshooting a turn and riding through a puddle created by a tree falling over, don't know how I didn't flip the bike but the water was almost completely covering the stanchions, and I don't feel the need to worry about water getting in.

Originally Posted by burnthesheep View Post
120rpm on a 53/11 is 45mph. You all coasting down hills at faster than 45mph?

Either way, at those speeds if you do reach spinout on your drivetrain and reach terminal velocity then your aero resistance is vastly vastly more important than a half or one single watt in the wheels. That, and your body weight for going downhill.
Yes, don't you? Best ever was 70 according to the speedo, coming down a 4 mile descent called Petersburg Pass on the NY MA border. Even blew past a couple cyclists I knew who were only doing 55mph. I'm older and not as foolhardy but still consider 55 down large hills/small mountains where I know the roads to be quite reasonable.
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Old 04-30-20, 02:07 PM
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Originally Posted by Russ Roth View Post
I worked for a shop that had a nationally ranked BMX team and some of the kids really loved the CK hubs
I knew a few BMX dudes that loved the CK rear hubs for their pawl action. The nearly-instantaneous engagement meant they could get on the beans a millisecond faster out of corners/landing.
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Old 04-30-20, 04:07 PM
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Spin-down tests are mostly measuring the unloaded drag on the bearings (i.e. seals and lubricant pack), which is a very small portion of wheel-related drag in actual use. When you're riding, the really big factors are the energy taken for air to plow its way around the rim and tire, and the rolling resistance of the tire setup, neither of which are being measured at all in the spin-down.

The front hub on my grandfather's 1979 Fuji still has its original NTN cartridge bearings, and until the middle of last year, they had never actually had their grease refreshed. So while they were spinning smoothly, they were running fairly dry and had extremely low unloaded drag. Early last year I did a spin down testing them against a friend's Vision Metron wheels, complete with ceramic bearings. The ancient 36h box-section wheels spun for twice as long as the modern racing wheels.
This was sort of amusing, but fairly meaningless: at high speed on the road, the Metrons are easily more efficient.

Your Shimano wheel setup may well be less efficient than your Campy wheel setup, but the hub bearings aren't the first place I'd look for big discrepancies, unless you packed one of them with concrete instead of grease.
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Old 05-01-20, 12:04 AM
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Thanks all. The Dura-ace wheels are wearing heavier 25c Michelin tires with sidewall protection and the Record wheels are shod with 23c Michelins without sidewall protection. When you spin up two wheels back to back and there's a significant diff in rotational weight, it's easy to tell which is lighter, and in this case, it's the Campy wheelset. I never had this concern with the Campy wheels when they were new, and I'm guessing it's the weight of what they've packed the bearings with. The Dura-ace wheel doesn't even roll back from its stopping point. I'll dig into them and have a look.
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Old 05-01-20, 06:19 AM
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Originally Posted by Russ Roth View Post
Yes, don't you? Best ever was 70 according to the speedo, coming down a 4 mile descent called Petersburg Pass on the NY MA border. Even blew past a couple cyclists I knew who were only doing 55mph. I'm older and not as foolhardy but still consider 55 down large hills/small mountains where I know the roads to be quite reasonable.
Cool.

What about the part though where I said a minuscule detail involving your aero is significantly more important than a watt in the wheel hubs?

Is the concern that they don't spin nice in a work stand, don't roll as far down a small roll down test, or are they sooooooo slow descending that they outweigh the importance of your position on the bike?

I'm a marginal gains kind of thinker for TT, but there has to be some practical application as well.

Also, the whole spin down and little tests done aren't the practical application anyway. You'd need to be able to accurately replicate it at the speeds of concern like a rolling resistance test using a set of rollers and really nice power meter.

Unloaded bearing spin is a worthless assertion of their capabilities under load and at speed.
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Old 05-01-20, 07:15 AM
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Originally Posted by burnthesheep View Post
Cool.

What about the part though where I said a minuscule detail involving your aero is significantly more important than a watt in the wheel hubs?

Is the concern that they don't spin nice in a work stand, don't roll as far down a small roll down test, or are they sooooooo slow descending that they outweigh the importance of your position on the bike?

I'm a marginal gains kind of thinker for TT, but there has to be some practical application as well.

Also, the whole spin down and little tests done aren't the practical application anyway. You'd need to be able to accurately replicate it at the speeds of concern like a rolling resistance test using a set of rollers and really nice power meter.

Unloaded bearing spin is a worthless assertion of their capabilities under load and at speed.
I failed to mention, I'm not an aero person and never have been, I'm just the wrong shape and wear shorts and a t-shirt to everything but races. So while I know position and clothing make a huge difference the ability of the wheel to spin significantly faster and stay stable at high speeds is very important.
Your last part I addressed with my example, couldn't agree more, wheel spin loaded is the important determiner.
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