Free Speed - what is it?

Everything about building wheels, glueing tubs, etc.
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JBC2
Posts: 16
Joined: Sat Jan 13, 2018 4:51 pm

by JBC2

I spotted this term in comment three on post linked below and it had me wondering what it meant.

viewtopic.php?f=113&t=137898&hilit=free+speed

I am in the market for a new wheelset for racing in region of ÂŁ800 and the wheelset this comment was made about is on the list although my preference is probably for high end aluminium rather than cheaper and heavier carbon (at this price point).

However the "free speed" comment concerns me and I confess I am not sure what was meant?

In my experience I have rear wheels that spin but quickly have some form of drag on the rear hub and the wheel slows to a stop reasonably quickly.

On the other hand I have had rear road wheels that spin up and stay at a decent velocity for some time.

So in a racing scenario if I was descending on wheels with a lack of "free speed" does that mean I would need to work harder to maintain pace than a rider on a set that had "free speed".

Any advice gratefully received!

by Weenie


AJS914
Posts: 2478
Joined: Tue Jan 28, 2014 6:52 pm

by AJS914

Yeah, it means you'd have to work about .5 watts harder.

JBC2
Posts: 16
Joined: Sat Jan 13, 2018 4:51 pm

by JBC2

Noted but what is actual technical difference between hubs that create this effect?

There has to pro's and cons for both else surely all would all would maximise free speed?

I have read that Mavic also have 'draggy' hubs, is this the same kind of effect?

AJS914
Posts: 2478
Joined: Tue Jan 28, 2014 6:52 pm

by AJS914

all would maximise free speed
The primary driver is cost. You can buy the smoothest rolling hub with the most expensive bearings and it will cost you a small fortune to save 1/2 watt or less.

As far as aero goes you can buy the most aero wheel set. There are tradeoffs though - high cost, braking issue with carbon, the fact that aero wheels only really provide major benefits at high yaw, weight, and being affected by side winds.

JBC2
Posts: 16
Joined: Sat Jan 13, 2018 4:51 pm

by JBC2

Thanks, so in essence there is no difference in descending in race conditions on a wheel that doesn't have as much "free speed" than one that does? Money is better spent elsewhere?

AJS914
Posts: 2478
Joined: Tue Jan 28, 2014 6:52 pm

by AJS914

Has anyone in a local race ever won on a downhill? If you save 3 seconds on a downhill with a set of $2500 wheels is that the difference between winning and losing the race?

You could run models at a site like analytical cycling and compute differences.

https://www.analyticcycling.com/

You can buy a some speed but it isn't free and it's generally expensive. The free stuff is positioning, wearing tight fitting aero clothes, shaving legs, face, etc.

Multebear
Posts: 1168
Joined: Sat May 02, 2015 10:11 pm

by Multebear

I've never heard the term "free speed", and I have no idea, what the poster in question is referring to.

If you spin a wheel on a bike without you riding it, just spin it while holding it, it is a question of the lubricant in the bearings, that decides how long the wheel will keep spinning. And I can assure you, that you can't draw any conclusions regarding the wheel by just spinning the wheel in your hand. This doesn't give you any information about how fast the wheel is at all.

Regarding the wheelset in question - Fulcrum Racing Quattros. I've never owned a pair of Fulcrum wheels, but from the countless reviews, posts and comments about them, they are very good wheels. Solid hubs, rims and construction. If you like them, buy them. Will they cover your needs? I don't know, since you haven't specified your needs.

We need to know your weight, riding style, terrain, weather and the purpose for the wheels in order to give you some good advice regarding the right wheelset.

And BTW carbon isn't heavier than alloy. It's the other way around. And cheap rims aren't necessarily bad. All my carbon rims are from chinese company Farsports. I've laced them to some high end hubs and used high end spokes. I'm pretty sure they aren't slower, heavier or less durable than the top end offerings on the market. At least not to an extend where it would make a difference in a race.

JBC2
Posts: 16
Joined: Sat Jan 13, 2018 4:51 pm

by JBC2

Thanks for the replies.

I read the "free speed" comment as spinning the rear wheel and timing its spin time. I may be wide of the mark for whatever the original poster was referring to however I have a set Farsport CX wheels that have seen better days and hardly spin at all, just a few seconds max! I certainly wouldn't want that on a new set of road wheels!

Just to note at the price point I am concerned that the available Carbon Clinchers will not be on par with what I think is my preference and that being the Fulcrum Racing Zero Nite.

The Fulcrum Racing Quattro Carbon's are actually heavier than the Zero's and I think I prefer the practicality and stopping power of aluminium.

Its a difficult call, but I feel the Zero's are better spec overall.

Multebear
Posts: 1168
Joined: Sat May 02, 2015 10:11 pm

by Multebear

Not sure what kind of Farsports wheels you're running and how much you've used them. But first of all, Farsports sell rims. If you want a wheelset, they will pick some hubs and spokes, and put it together. But they are a company selling rims first of all.

If your wheels don't spin enough, it's probably because of wear and lack of servicing the hubs/bearings. Farsports least expensive complete wheelset offerings come with Bitex, Novatec or some other low end hubs. And if you ride cx with them, you'll decrease their life span significantly. That is the reason why I build them with high end hubs like DT Swiss 240s, Chris King R45, White industries T11, Dura Ace or a few others.

JBC2
Posts: 16
Joined: Sat Jan 13, 2018 4:51 pm

by JBC2

Yes these are on Novatech's and built by Farsports and priced very fairly.

I wasn't expecting any more than what the wheels have provided at the price I paid, particularly the abuse they get training and racing CX.

My point was purely that the lack of free spinning is something I always check for first when I buy new wheels.

Multebear
Posts: 1168
Joined: Sat May 02, 2015 10:11 pm

by Multebear

JBC2 wrote: ↑
Sun Jan 14, 2018 12:49 am

My point was purely that the lack of free spinning is something I always check for first when I buy new wheels.
Well, it wont provide you with more information than kicking the tire of a car....

AJS914
Posts: 2478
Joined: Tue Jan 28, 2014 6:52 pm

by AJS914

It's only showing you the friction against the bearing seal unless there is an issue with the bearings. Getting past the friction of those seals only takes less than a watt (I think i read 1/3 of a watt).

If your Novatec hubs have seen better days then service them with some high quality bearings. Cheap speed.

Alumen
Posts: 113
Joined: Tue Aug 18, 2015 1:47 pm

by Alumen

Post subject: Free Speed - what is it? --> it is a myth that exists between our ears for us mortals... Unless your surname is Dumoulin, Cancellara or Froome...

If you want free speed while descending, you better can gain some extra weight...

Sorry for bullying, I don't mean it that rude, but in reality you won't notice any differences.
CAAD 10 2015

vanillaflyweight
Posts: 25
Joined: Thu Aug 10, 2017 5:54 am

by vanillaflyweight

Free speed is the term given for additional speed for the same watts. An example is zipp 808s vs some old aluminum box section wheels, obviously you are buying the "free speed" but nevertheless you won't need to work as hard to hold the same speed (on the flat anyway).

by Weenie


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