# Why do pros use shallow wheels even on mountain stages?



## deviousalex (Aug 18, 2010)

So let's sum up a few things that have been stated on this forum or is general knowledge.

* With the latest carbon bikes and high-end groups the use of a very shallow tubular wheels means weight needs to be added to the bike (via heavier BB, cassette, bottle cage, etc) to meet the UCI's 15lb requirement.

* At the speeds where people ride their bikes (especially when going uphill) the rotating weight argument makes little to no difference. The speeds are not fast enough for rim mass to truly matter.

* Even when accelerating at slow speeds overcoming aerodynamic drag is more important than weight (see Alex Simmon's blog post Alex's Cycle Blog: The sum of the parts II ).

So why not use a more mid-depth 35-50mm rim to meet the UCI's minimum weight requirement?


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## tlg (May 11, 2011)

Per Alex's blog... "At 9% gradient it's line ball and once you go steeper than that, well the lighter rim is quicker." 
His "hill" analysis is at a 4% gradient. I'm not sure the pro's consider 4% a climb. 

Also the pro's ride in groups and have lead-out men. So overcoming aerodynamic drag isn't as much an issue. 
For solo breakaways a deeper wheel would make sense though.


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## deviousalex (Aug 18, 2010)

tlg said:


> Per Alex's blog... "At 9% gradient it's line ball and once you go steeper than that, well the lighter rim is quicker."


I saw that statement as well, but if we follow the conclusions of his argument that rotating mass is un-important I would assume he's talking about total bike weight there, not just wheel weight.


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## tlg (May 11, 2011)

deviousalex said:


> I saw that statement as well, but if we follow the conclusions of his argument that rotating mass is un-important I would assume he's talking about total bike weight there, not just wheel weight.


Well he says steeper than 9% the lighter rim is quicker. Not the lighter total weight. All the calculations were with equal total weight.

I'd be interested to see the calcs on a 10%+ grade with a 30sec acceleration.


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## deviousalex (Aug 18, 2010)

tlg said:


> Well he says steeper than 9% the lighter rim is quicker. Not the lighter total weight. All the calculations were with equal total weight.


His calculation there is accounting there is where the bike stays constant and the rim gets heavier hence a heavier total weight.


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## tlg (May 11, 2011)

deviousalex said:


> His calculation there is accounting there is where the bike stays constant and the rim gets heavier hence a heavier total weight.


Ahhh gotcha.


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## den bakker (Nov 13, 2004)

which rims are more fun on steep twisty descends at their speeds?


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## Gnarly 928 (Nov 19, 2005)

*Deep wheel sections in the mountains...Not that fun..*



den bakker said:


> which rims are more fun on steep twisty descends at their speeds?


 For one thing, a deep section front wheel in the windy alpine mountains can be fairly scary, even dangerous, to handle. Perhaps that's one reason they choose ride the climbs with lower profile wheels...

I have a choice of carbon tubie wheels and when it's windy I stick on my 22mm reynolds, for sure on the front anyhow. It just doesn't get blown around like my deeper ones. I can't really detect the difference in uphill speed at my pace but there is.....a very noticeable difference in handling on the descents and even on the climbs..... I do often encounter swirling winds and side-gusts...Palomar mountain, Montezuma Grade, the Eastern Sierras, the Mount Hood area and the Columbia Gorge (windsurfing capitol of the US, some say) Even a mid-rim like the Zipp 303s are subject to getting blown off-line when on the front end. That is my guess..


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## Gnarly 928 (Nov 19, 2005)

den bakker said:


> which rims are more fun on steep twisty descends at their speeds?


 There IS a quantifiable speed advantage on the downhills with a deep section tubular carbon rim, however...I had the pleasure of climbing and descending a 3700' climb repeatedly with my Garmin and Strava...sometimes on deep rims, sometimes on shallow...perhaps 30 times last winter with various friends and in all kinds of conditions...With the deep dish carbons on both ends of the bike, a significantly better tucked-in speed, compared to other riders, than when tucked in on shallow rims with the same riders....but you must really pay close attention to any side winds on the deep section wheels...Usually I reserved those wheels for really calm days or when I was riding alone so I could brake and descend at a slower pace...


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## looigi (Nov 24, 2010)

With the current crop of fat inner edge deep section (not dish, that's pizza) rims, the concern over crosswinds are overblown (so to speak) IMO.


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## deviousalex (Aug 18, 2010)

looigi said:


> With the current crop of fat inner edge deep section (not dish, that's pizza) rims, the concern over crosswinds us overblown (so to speak) IMO.


Indeed. Plus the faster you are going the more the apparent wind angle becomes a straight headwind.


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