Depth vs width
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Thread: Depth vs width

  1. #1
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    Depth vs width

    The latest is that wider rims are more aero, right? To what extent? Meaning, how would a 30mm deep and 30mm wide rim compare to a 45mm deep rim of narrower flavor?

    There are just so many variables these days it is hard to compare or evaluate things.

  2. #2
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    no, wider is not more aero according to the video in this post which seems to be a very good source of information. 23mm wide and the deeper the better, however that is not going to be the most liveable wheel in the real world for most. https://forums.roadbikereview.com/wh...ow-369243.html
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  3. #3
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    Why are rims getting wider then? Genuinely curious.

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    Quote Originally Posted by lightning33 View Post
    Why are rims getting wider then? Genuinely curious.
    In a closed environment with no bumps (velodrome) , a skinny, deep wheel/tire combo like 21 or 23 would be fastest. Inflate to 120psi and your tires would be like a rock.

    The roads you and I ride on are not 100% smooth. Quite bumpy actually.
    Bumps:
    -Cause fatigue
    -Slow down the bike

    So today's rationale is that Wider tire 25/28 inflated to a good balance of front/rear psi will:
    -decrease fatigue
    -cause a more ideal contact patch for the rubber to roll over instead of "bouncing" over

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    Quote Originally Posted by sramred View Post
    In a closed environment with no bumps (velodrome) , a skinny, deep wheel/tire combo like 21 or 23 would be fastest. Inflate to 120psi and your tires would be like a rock.

    The roads you and I ride on are not 100% smooth. Quite bumpy actually.
    Bumps:
    -Cause fatigue
    -Slow down the bike

    So today's rationale is that Wider tire 25/28 inflated to a good balance of front/rear psi will:
    -decrease fatigue
    -cause a more ideal contact patch for the rubber to roll over instead of "bouncing" over
    Pretty much this. Except pursuit/kilo riders use 200-220ish psi on the track. Mass start racers are using 120-140.
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  6. #6
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    Quote Originally Posted by sramred View Post
    In a closed environment with no bumps (velodrome) , a skinny, deep wheel/tire combo like 21 or 23 would be fastest. Inflate to 120psi and your tires would be like a rock.

    The roads you and I ride on are not 100% smooth. Quite bumpy actually.
    Bumps:
    -Cause fatigue
    -Slow down the bike

    So today's rationale is that Wider tire 25/28 inflated to a good balance of front/rear psi will:
    -decrease fatigue
    -cause a more ideal contact patch for the rubber to roll over instead of "bouncing" over
    That explains tires bigger than 23.
    All true but the question was about wider rims not tires.


    For aero: A smoother transition from tire to rim. In other words no lightbulb shaping.

    For ride quality: Wider rims are to increase the air volume of same size tires as compared to a narrower rim. In other words you're using a bigger tire without actually buying a bigger tire and the weight that comes with it. Need to use less PSI to take advantage of this.

  7. #7
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    re: wheel depth vs aero

    wheel manufacturers are now making wheels that are wider due to:
    -the current tire research that 25/28mm tires are more popular, so they make wheels that match the profile to prevent the "balloon" effect. That causes a turbulent spot between the balloon of the wire and the edge of the rim.
    -wider rims may be more stable under all conditions (more while turning, but if you think about it, our front rim is 100% straight less than 10% of your ride, theres always little twitches, you tugging on the handlebars, turns on the road, etc)

    -cons: heavier rim + heavier tire + aerodynamic impact

    i'm currently riding 25mm GP5000 on 35mm, 19mm inner, 25mm outer Deep Carbon Hollowgram wheels.

  8. #8
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    Speed is not all about aero - rolling resistance is a factor as well and that's not going to be optimized with skinny highly inflated tires on the roads most people ride on.

    Being able to maintain a good position for aero for the rider for longer periods of time has some impact from rider comfort too, again which skinny tires with high pressure isn't going to be optimal. Heck just being to ride for longer periods of time skinny tires with high pressure aren't a great choice for most people.

    Usability in the real world one has to deal with cross winds also which super deep wheels aren't optimal for. Also rim cross section profiles optimized for aerodynamics aren't typically the best for cross winds.

    Bottom line, there are lots of trade offs choosing a wheel, having the best wheel aerodynamically for most of us isn't going to be the best choice, the trends in wheels are following real world trade offs and what people prefer all considered, and what is marketable.

    I have 23mm wide internal and 31.5 mm external with 25mm depth on my gravel bike, that weigh about 1300 grams - I don't really worry about aero on it as much as I do durability.

    On my climbing bike, I have 21mm internal, 27.5 external 40mm depth wheels that weigh 1400 grams because I care more about weight than aero and I wanted tubeless capable for comfort since the frame is fairly stiff and lower pressures from tubeless do that well.

    On my endurance bike used for my long rides on the road, I have 21mm internal 27mm external 50mm depth wheels that weigh 1570 grams - it's a cushy frameset so I don't need tubeless tires to be comfortable on long rides and aero matters more the farther the distance.

    I dont own any narrow deep wheels because they wouldnt be practical for any of the riding I do. Sure they would be fast on the flats with no wind, but the precentage of time I see that riding is very very low.
    Last edited by Srode; 3 Weeks Ago at 07:07 AM.
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  9. #9
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    Quote Originally Posted by Jay Strongbow View Post
    That explains tires bigger than 23.
    All true but the question was about wider rims not tires.

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  10. #10
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    The reason I started the thread was that on my new bike, it came with Reynolds AR 29 wheels. They are 30mm deep and 30mm wide (21mm internal) with 28mm tires. I was originally looking for a more aero wheel (like the AR41, just to keep it in the Reynolds family), but started thinking that yesterday's 41mm might be today's 30mm.

    Granted, I am coming from Shimano R500 23mm deep box rims with 23mm (max the frame could handle).

    I am not quite sure I notice a difference from the more aerodynamic and lighter wheels, but I 100% do notice the change from 23 to 28. Also, old bike was alu and new bike is carbon, so too many changes to really drill into what is making ______ feel ________ compared to the old bike.

    Thanks for the replies.

  11. #11
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    Quote Originally Posted by lightning33 View Post
    The reason I started the thread was that on my new bike, it came with Reynolds AR 29 wheels. They are 30mm deep and 30mm wide (21mm internal) with 28mm tires. I was originally looking for a more aero wheel (like the AR41, just to keep it in the Reynolds family), but started thinking that yesterday's 41mm might be today's 30mm.

    Granted, I am coming from Shimano R500 23mm deep box rims with 23mm (max the frame could handle).

    I am not quite sure I notice a difference from the more aerodynamic and lighter wheels, but I 100% do notice the change from 23 to 28. Also, old bike was alu and new bike is carbon, so too many changes to really drill into what is making ______ feel ________ compared to the old bike.

    Thanks for the replies.
    Upgrades are a law of diminishing returns. The R500 is Shimano's most entry level road wheelset. Anything above that is an improvement. Not to mention that it's a different bike as well, so too many variables to compare. Even with the wheels themselves, are they really faster or do they just feel faster? Reduced rotating weight will make you accelerate faster, but once up to speed, weight is weight. And unless you regularly race at speeds of 20mph, you are unlikely to notice any aero improvements.

    I would say that you are unlikely to notice any improvement stepping up to the AR41 other than the reduced weight of a lighter wallet.
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