Noisy vs Quiet freehubs, efficiency?

My present bicycle is a year 2005 Trek 2100WSD 47cm with Bontrager Race 650C wheels and Ultegra 9-speed cassette. Comparing this bicycle to several others which I've ridden over time, in particular the new Trek Domane, it feels like my old 2100's freehub is more efficient - the bicycle just wants to go faster coasting downhill. It's also very quiet compared to most others.

In general, noise = mechanical energy, and noisier = more energy loss to the freehub action while not pedaling. But of course there's nothing general about comparing one specific freehub to another one, which is why I'm here today asking you for your advice!

I recently rented and rode several hundred kilometres on a 2013 Trek Domane 5.9, with Bontrager Race Lite wheels and Ultegra 10-speed cassette, and I've just started the ordering process to buy a 2014 Trek Domane 5.2 with Bontrager Race wheels and Ultegra 6800 11-speed cassette. The 2013 Race Lite rear wheel's freehub is noisy, and coasting downhill without pedaling I really feel that the freehub creates noticeable resistance. (I also recently rode a Scott S20, and similarly the freehub was very loud and the resistance it created was noticeable).
I just returned today from a ride on my old Trek 2100 with its quiet freehub, and I'd swear that it just rolls downhill faster.

There's at least one not-apples-to-apples comparison here - my Trek 2100 has 650C wheels, and all of these other bicycles that I'm commenting about have 700C wheels. If nothing else, the inertia of the larger wheels is surely greater, which would mean that the larger wheels would accelerate more slowly. But on a long coasting descent, the speeds which the bicycle would routinely reach shouldn't be affected by the wheel size and inertia, because slower acceleration is still acceleration. But it would be affected by the efficiency of the freehub, which is constantly (and at higher speeds, more) bleeding off energy/speed.

So here's the question: Does anyone know the details about the efficiency of the 2005 Bontrager Race wheels' freehub - Ultegra 9-speed as came on my 2005 Trek 2100WSD 47cm with 650C wheels, and how to compare that to the efficiency of the modern 2014 Bontrager Race wheels' freehub - Ultegra 6800 11-speed? .. and suggestions on how I might make a brand new 2014 Domane 5.2's freehub quieter and more efficient?

thanks, and I apologise in advance for any obvious boneheaded misunderstandings I've demonstrated in asking the question here today. (Plus, please don't respond "real riders should always be pedaling, so the freehub's efficiency shouldn't be that important". So, I'm not a "real" rider. Fine).

Jay

 

I have a set of 50mm no name Chinese carbon/alloy wheels. Novatec hubs. Not exceptionally loud. Not outstandingly quiet. My bike is a no name carbon aero frame. Not exceptionally heavy (as is often said about aero bikes). Not especially light. The remarkable thing is it honestly feels like the bike coasts uphill! I sh!t you not! I love it!

 

Thanks BikeLockHolmes. Can you tell us the specific model number of the Novatec hubs? ...Something about how they're designed/ how they work which make them quiet and efficient? I looked at Novatec's website, and they have a lot of different hubs, and no information (that I could find) about what makes them work and what makes them better/worse than any other. thanks,

 

I've got two pairs of Novatec's A271SB & F372SB hubs on my 2 pairs of Chinese carbon wheels. They're pretty ubiquitous. They're stock on tons of wheels you buy from China. They came already installed on both the 2 pairs wheels I own when I bought them. Didn't have to lube 'em or anything. Straight out of the box, plonked the cassette on 'em. And BOOM! I was on the road in seconds after they were delivered! Love em! I can't tell you anything about the tech side of it though. But maybe this doc and these vids will answer your tech questions: That's not me in that last vid, by the way. That guy just happens to have the same hub; Like I said. They're very common on no name Chinese carbon wheels

 

I've never tried it myself. But I seem to recall reading somewhere that prodigious amounts of grease (in the inner workings) cures a loud hub. Don't know if it would affect efficiency one way or the other though.

 

The sound made by Campagnolo hub/cassette mechanisms is a symphony and should rightly be patented by Campy as the most glorious sound in cycling.

Noise/volume can be generated and amplified by the design of the freehub assembly, the number of springs/pawls, the number of ratchet teeth, the spring pressure on the pawls, the lubricant used, the bearing type the freehub body rotates on, etc. I'm not sure a loud freehub is an inefficient freehub...it may be one that just amplifies the sounds that are dampened by a less noisy unit.

I currently train on the cheapest Mavic wheels in the product line and can discern no difference in the drag of the freehub than my race wheels built on Record hubs. The Campy unit spins on some of the most precise bearings in cycling while the inboard side of the Mavic uses a much higher drag (in theory) Delrin bushing.

 

I was in a bike shop today which had a couple of 2014 Domanes (a 4.7 and a "Leopard" which I guess is a 6-series). Both had rather quiet freehubs.
So, maybe, probably, hopefully, the 2014 Domane 5.2 which I've ordered is going to be quiet, and the problem I'd been expecting was just because the 2013 Domane 5.9 which I rode last week has a noisier hub. Fingers crossed!

 

Drag created by the ratchet mechanism should be insignificant. Unless one bike makes you more aero or or is heavier than another, the difference in ability to coast downhill is all in your head. This can easily be tested with both bikes, a hill and a stopwatch.

If the drag were real, you would feel the pull in your legs. If you want to go fast, you should be pedaling on the way down anyway.

If it is a matter of taste - the wheels can always be swapped.


Another way to test the drag without using two bikes would be to do a series of coast downs from speed. Half the coast downs would be with your feet in the pedals so that the crank does not spin. The other half of the coasts would be with your feet out of the pedals allowing whatever drag in the freehub to spin the pedals. If your theory is correct, the noisy / high drag hubs should spin the unimpeded pedals and you should coast farther at a given starting speed whereas low drag hubs should have no discernible change in coast distance.