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Re: 1x aero gains [Bogusdogs] [ In reply to ]
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+1 on that.

29 years and counting
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Re: 1x aero gains [Bogusdogs] [ In reply to ]
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Bogusdogs wrote:
Speculative minimal gains, if any it seems. Not to mention these gains were at 30mph...do you remember that triathlon you did where you averaged 30 mph? I am sure there is a reason for that but it seems most testing has been done at 40 kph (~25 mph), why the change?

I personally struggle with the constant jumps in gears you will experience on the road. I understand it more on a mt bike, but on the road you get a subtle headwind, a pitch from 1% to 1.5%...going from a 15 tooth cog to a 16 allows you to maintain a similar cadence/power by shifting a gear. Seems like your best time trialists maintain a steady power and cadence...less stress on the body. I get why they run a 1x in the world championships or Olympics when it's a flat course. So maybe courses like IM Florida, AZ, Texas, would all be good places to run a 1x. But not so much Whistler, Cda, Lake Placid, Lanzarote, etc.

So, I guess if you have to switch cassettes to run a 1x, then maybe a 1x isn't ideal...for me anyway But if the course you are racing on, and terrain you train on, allow a 11x25, then maybe a 1x is a good fit.

Well your concerns are kinda different from what the OP was asking, but they do make for decent discussion points. My bike is set up as a pure TT bike for sub-60 minute efforts on a typical TT course, which I consider to be from flat to rolling with grades of not much more than 3-4% absolute max. A 52 front with an 11-27 is all I would ever need on this bike. 2X is just extra baggage/chainwatcher.

If you ride your TT/Tri bike everywhere then 2X is kinda hard to beat with current technology.
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Re: 1x aero gains [M----n] [ In reply to ]
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Would it not have been more appropriate to test a 1x Premier against a 2x Premier to understand the advantage of 1x?


Take a look at the figures directly below the graph.

'It never gets easier, you just get crazier.'
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Re: 1x aero gains [grumpier.mike] [ In reply to ]
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Ya, I guess I did kind of go beyond the original question. But I guess I was more looking at it from any time gains versus performance loss. But for 40k generally "big ring" rollers, the small ring is juts an ornament.
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Re: 1x aero gains [CCF] [ In reply to ]
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It's funny to see people talking about this now. About 10 years ago, I switched to a track crank with a single chain-ring because:

* Much narrower Q-factor
* Possible to use the old Campy square taper BB, which had the lowest drag of any I ever tested



https://hcphoto.smugmug.com/keyword/0942/i-LQSvgJv/A

I saw gains that worked out in the 3 watt range, though I believe that was because of the Q factor, not having one less chainring.

<RANT>
Unfortunately, with all the Bike Mfr bottom Bracket stupidity that has happened in the last 15 years (yes, I mean you Cervelo), we're stuck with massively wide BBs that are aerodynamic crap AND have huge seal drag. My Campy square taper saved several watts even over the Ceramic outboard BB of the day. I'll bet the new PF/BBright stuff is even worse. All in the name of "stiffness." Stiffness is great for the bedroom. For the race course, it's highly over-rated.
<\RANT>

My latest book: "Out of the Melting Pot, Into the Fire" is on sale on Amazon and at other online and local booksellers
Last edited by: jens: Jan 11, 17 17:14
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Re: 1x aero gains [jens] [ In reply to ]
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Re: 1x aero gains [jens] [ In reply to ]
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Yep, the whole BB thing is a farce.

29 years and counting
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Re: 1x aero gains [jeffp] [ In reply to ]
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jeffp wrote:
I doubt the numbers come out the same once you add spinning feet into the mix
Agreed. It's going to be SFA at most when you look at the whole picture. Better off concentrating on making your training count.
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Re: 1x aero gains [jens] [ In reply to ]
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What was you Q factor with the Campy square taper BB?

I just looked at Power2max's and SRM's track powermeters (Rotor versions). The Power2max is not any narower than their road version, while the SRM is slightly narrower at 141.5mm. I would like it even narrower, but as you mention, might not even be possible on my P5 with BBRight.
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Re: 1x aero gains [MTM] [ In reply to ]
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MTM wrote:
What was you Q factor with the Campy square taper BB? ...


The Campy BB with the Campy Record Pista track crank was 131 (!). That's the one in my photo above.

I don't think you can get much narrower than that. The only challenge with the track crank was finding road-pitch chainrings with a 144 BCD bolt pattern.

I used to love giving the crank a spin when the chain was off. It would spin for ages, just like a wheel with a really good hub. The stupid external BB cranks spin for a turn or two at most.

My latest book: "Out of the Melting Pot, Into the Fire" is on sale on Amazon and at other online and local booksellers
Last edited by: jens: Jan 13, 17 3:32
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Re: 1x aero gains [jens] [ In reply to ]
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You can always go Fibre-Lyte rings and chose your tooth count.
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Re: 1x aero gains [BMANX] [ In reply to ]
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This has me wanting to buy back my old P3 setup. The only thing stopping me is that I can't get the Campy Pista cranks in 145mm.....

My latest book: "Out of the Melting Pot, Into the Fire" is on sale on Amazon and at other online and local booksellers
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Re: 1x aero gains [jens] [ In reply to ]
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Can you go as short as possible then have Fibre-Lyte custom make a ring for you. If you send them the drive side crank arm, they can actually cut out the ring to match the profile. I had this done on my road cranks and they are sweet.
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Re: 1x aero gains [CCF] [ In reply to ]
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CCF wrote:
I know that some have switched to 1x for a mixture of simplicity and aero reasons. Can anyone who has been able to do testing share any aero data? Was the switch to 1x a significant improvement, or just an incremental gain?

Thanks,
-Colin

I can't remember if it was on the forum or in a PM exchange (didn't do much of a search), but I remember a member had posted 1x aero tests with a QR frame (again, can't remember the exact one, but I think it was a current PR model, but did have the "shift" downtube) and found the removal of the FD increased drag but something like 4-6 watts.

Offered up as another data point ... maybe your search skills will better mine.
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Re: 1x aero gains [jens] [ In reply to ]
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jens wrote:
MTM wrote:
What was you Q factor with the Campy square taper BB? ...


The Campy BB with the Campy Record Pista track crank was 131 (!). That's the one in my photo above.

I don't think you can get much narrower than that. The only challenge with the track crank was finding road-pitch chainrings with a 144 BCD bolt pattern.

I used to love giving the crank a spin when the chain was off. It would spin for ages, just like a wheel with a really good hub. The stupid external BB cranks spin for a turn or two at most.

I have always wondered how much extra friction losses there are in external BBS.
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Re: 1x aero gains [Thomas Gerlach] [ In reply to ]
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Thomas Gerlach wrote:
Seems to be very conflicting data out there. I have heard rumors that some people claim that bikes were designed with airflow of the chainrings in mind and removing a chainring actually increases drag. I am not so sold on that and I think obviously an opportunity exists to design a bike around 1x but this provides at least another data point. As a DI2 user, I also recognized that the DI2 brake lever is quite a bit bigger than than non-di2 and you get to remove one of those as well.

When it comes to true TT bikes, it wouldn't surprise me at all if this were the case. I bet it's an unintentional design choice though since they are probably only testing with double chainrings since that's what's most widely used.

--------------------

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Re: 1x aero gains [jens] [ In reply to ]
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jens wrote:

This has me wanting to buy back my old P3 setup. The only thing stopping me is that I can't get the Campy Pista cranks in 145mm.....

Don't let that stop you - bikesmithdesign chop off a minimum of 22mm when shortening cranks. So taking 170s to 145 is no problem.
Then find a P4...
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Re: 1x aero gains [boulderoadie] [ In reply to ]
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I tested 1x this week at the wind tunnel - frame was a size 54 P5-6 with eTap, 170 SRAM RED DZero, 55T SRAM TT ring.

We removed the FD and hanger - we did not swap chainrings to a xsync (no time, this was our last run).

0 yaw was .002 worse with the FD & hanger removed.
-10 yaw was .000 different

I was on the bike and pedaling.

I wasn't really wanting to go to 1x and perhaps the xsync ring and lack of inner would be different but for me, I'm sticking with my two ring setup.
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Re: 1x aero gains [WD Pro] [ In reply to ]
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WD Pro wrote:
I wonder how something like this :



Or one of the carbon covers would influence the results (with regards yaw and the inner chainring) ?

WD :-)


I'll one up you. Built in narrow/wide chainring to boot. I can't find it in stock anywhere :(
http://www.visiontechusa.com/...-megatooth-crankset/
Edit: can't get image to embed
Last edited by: GreenPlease: Jan 22, 17 18:11
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Re: 1x aero gains [GreenPlease] [ In reply to ]
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It could potentially make things worse. The bottom bracket and crankset are a high-pressure area on the bike, and restricting airflow (rather than increasing it as in most 1x setups) may increase this pressure. Or it could make things better, but it's complex air around there.

See for example this image:
http://www.computationalfluiddynamics.com.au/...s/2012/06/avanti.png

And the interesting magazine article it came from:
http://resource.ansys.com/...-I2-Full-Version.pdf

'It never gets easier, you just get crazier.'
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Re: 1x aero gains [Thomas Gerlach] [ In reply to ]
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I'm surprised nobody has attempted to make an aero chain guide for frames where you can't remove the FD hanger.
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Re: 1x aero gains [GreenPlease] [ In reply to ]
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GreenPlease wrote:
I'm surprised nobody has attempted to make an aero chain guide for frames where you can't remove the FD hanger.

Prob too small of a market. I just want a better airfoil shape that I can use behind the FD hanger - should be easy enough to 3d print.


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Re: 1x aero gains [GreenPlease] [ In reply to ]
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Is that actually available for purchase anywhere?

I've been looking at an aero 1x setup, and it's going to be at least $350 for the chainring (http://absoluteblack.cc/...-criterium-chainring) and a crankset to mount it up on. If there was something else that is already cleaner, I'd be mighty interested.
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Re: 1x aero gains [chicanery] [ In reply to ]
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Not to my knowledge. Someone should make one (3d printed would be fine).
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Re: 1x aero gains [GreenPlease] [ In reply to ]
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I was almost stressed out enough about the hanger to put a wrap of electrical tape around it. But then I got over it.

/kj

http://kjmcawesome.tumblr.com/
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