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PostPosted: Wed Jun 13, 2012 9:05 am 
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SWijland wrote:
Why doesn't LOOK reduce the spacing between the fork tips? This seems much easier, compared to the 'open' axle tips on the new Mavic wheel.


Claimed negative interaction with wide spoked wheels such as the IO and Hed3 and narrow spaced forks - search for comments referencing figure 9c in the following...

http://www.acusim.com/papers/AIAA2011_1 ... 11_web.pdf" onclick="window.open(this.href);return false;

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PostPosted: Wed Jun 13, 2012 9:34 am 
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Pokerface07 wrote:
SWijland wrote:
Why doesn't LOOK reduce the spacing between the fork tips? This seems much easier, compared to the 'open' axle tips on the new Mavic wheel.



The width of the fork tips is a standard measurement - designed so any track wheel fits in there. Wouldn't make sense for them to narrow it so that only one wheel fits!


Now I understand why Shimano is upping their spacing on the rear to 131 :roll:

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Posted: Wed Jun 13, 2012 9:34 am 


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PostPosted: Wed Jun 13, 2012 10:35 am 
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shimano isnt upping their spacing. dt swiss is.

as far as rear tire to frame clearance, quite a few companies are revisiting the "gap" importance, including cervelo. i believe at least one of them is putting a deep channel where the tire is to give air that is sticking to the tire a place to go.


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PostPosted: Wed Jun 13, 2012 4:33 pm 
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No, Cervelo's P5 reaffirms that a gap is just unnecessary. There is no drag difference for a gap up to 7mm for an optmized rear wheel drafting seattube cutout, which pretty much everyone follows as it makes sense and it is verified in tunnel and. cfd. Rotational affects at that Reynold's #?? not really.


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PostPosted: Wed Jun 13, 2012 4:57 pm 
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justkeepedaling wrote:
No, Cervelo's P5 reaffirms that a gap is just unnecessary. There is no drag difference for a gap up to 7mm for an optmized rear wheel drafting seattube cutout, which pretty much everyone follows as it makes sense and it is verified in tunnel and. cfd. Rotational affects at that Reynold's #?? not really.



Here is DZ's P5 setup:

Image

Cervelo has said that a gap of 1-6mm is the same, however Look's gap is significantly more than 6mm. I haven't measured it but it looks more like 20mm gap.


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PostPosted: Wed Jun 13, 2012 7:46 pm 
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Yeah, sorry, I meant 6 mm. But yeah, BMC's has a little bit of gap on the top of the seattube due to the seatstay design but considerably less at the BB. Trek has a constant gap but much much less than Look. Specialized and Cervelo are in complete agreement as is Scott


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PostPosted: Thu Jun 14, 2012 6:08 am 
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it turns out we're in agreement: no difference between 1 and 6mm of gap, to me means there's no point running the rear wheel right up against the frame, might as well increase the gap. which is what i was trying to say, apparently poorly. it used to be people would try to run the rear wheel as close as humanly possible to the frame...


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PostPosted: Thu Jun 14, 2012 6:25 am 
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thisisatest wrote:
it turns out we're in agreement: no difference between 1 and 6mm of gap, to me means there's no point running the rear wheel right up against the frame, might as well increase the gap. which is what i was trying to say, apparently poorly. it used to be people would try to run the rear wheel as close as humanly possible to the frame...


I wouldn't call 6mm a big gap though... Unlike the Look frames.

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PostPosted: Thu Jun 14, 2012 6:32 am 
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Does any one know the true width of the gap on the Look? I can guess but I would like to know for sure.


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PostPosted: Thu Jun 14, 2012 6:57 am 
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I believe Pokerface is correct that this extra large gap is a by-product of the gear ratio chosen, which is far more important in a track race than 15mm of gap at the rear wheel.

I would wager a guess that if the wheel were slammed all the forward in the track ends, the gap would be no larger than it is on the 596 ( which is probably a 10-12mm gap - still larger than most).


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PostPosted: Thu Jun 14, 2012 7:02 am 
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http://www.lookcycle.com/media/upload/L96_GB.pdf

some extra info here


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PostPosted: Thu Jun 14, 2012 11:46 pm 
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On my Look 595 track frame, there is enough room in the rear dropouts to have the wheel right up against the frame with the correct gearing. I'd say you can move it up to an inch away from the frame also.

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PostPosted: Fri Jun 15, 2012 1:22 am 
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some argue that the aero gains to be made on the rear wheel are minimal; so what is the point of having the tire run so close to the seat tube?


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PostPosted: Fri Jun 15, 2012 1:50 am 
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speedwobbles wrote:
I believe Pokerface is correct that this extra large gap is a by-product of the gear ratio chosen, which is far more important in a track race than 15mm of gap at the rear wheel.

I would wager a guess that if the wheel were slammed all the forward in the track ends, the gap would be no larger than it is on the 596 ( which is probably a 10-12mm gap - still larger than most).


I have never seen a 596 in person before, but from most of the pics I have seen the gap looks well over 20-25mm range.

Image

I don't believe the 596 has horizontal drop outs, does it? Looks like vertical dropouts here.



roca rule wrote:
some argue that the aero gains to be made on the rear wheel are minimal; so what is the point of having the tire run so close to the seat tube?


I am honestly curious, who said that? I assume maybe Look? Maybe the gains are minimal, but when you add enough minimal gains together you eventually get some "substantial" gains.


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PostPosted: Fri Jun 15, 2012 2:20 am 
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http://www.flickr.com/photos/kwc/3030865087/" onclick="window.open(this.href);return false;

There are actually relatively substantial gains to be had from getting cleaner flow off the seattube over the rear wheel. Think of it as fairing a substantial portion of the wheel. If the wheel/tire is too far from the seattube, the airflow actually rejoins and then hits the tire front on causing the flow to separate once again.


Last edited by justkeepedaling on Fri Jun 15, 2012 6:00 am, edited 1 time in total.

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Posted: Fri Jun 15, 2012 2:20 am 


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