20 vs 23 tires

Discussion in 'Cycling Equipment' started by edd, Mar 11, 2006.

  1. edd

    edd New Member

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    Now nearly every one runs 700 x 23 mm tires (tyres) by one make or another and I read an interesting article on the net ( I'll find the url and post it ) which pretty well said 20 mm tires (tyres) were no advantage in rolling resistance etc.

    Seems to me though tire manufactures make these 20 mm tires for some one or some reason, you can pump them up harder and they weigh less.

    So question is … who uses them ?

    … even Conti have made a 700 x 20 in their new GP 4000 range ( 180g )
     
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  2. John M

    John M New Member

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    20mm only for TT on front wheel (narrower, more aero) or maybe on track.
     
  3. Powerful Pete

    Powerful Pete New Member

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    Obviously some people still prefer riding 20s and 21s. Most people who ride a 20 do it in specific circumstances (mainly TTs and track, as John stated).

    Stay with 23s for the extra comfort, unless there is a really specific reason you really need to go with something more narrow...
     
  4. edd

    edd New Member

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    Okay … I got that, 23s are what I use, I was wondering if anyone who rides on 20s has some insight … I am considering them for TT bike but was wondering if there is any real advantage of having 160 psi 150g tire for one thing my existing rims only recommend inflation to 138 psi
    … so I'm confused to why ?
     
  5. Spunout

    Spunout New Member

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    No advantage.
     
  6. 531Aussie

    531Aussie Well-Known Member

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    I agree with the others: no advantage.

    I rode 20mm tyres at 150psi for at least 10 years, so I can provide the insight. :) I thought I was getting some speed benefits, but I wasn't. Some of the 'race only' 20mm tyres, such as the Continental Supersonic ride ok (but obviously wear quickly), but for the most part, 20mm tyres just mean an uncomfortable ride, poor deformation over anything other than super-smooth roads (which means you're being slowed down), and VERY crap cornering. I feel like I wasted all those years. :( :)

    Back when I was riding 20s, every now and then I would try a cheap 23, then mistakingly judge all 23s by the characteristics of a cheapy.
     
  7. artmichalek

    artmichalek New Member

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    The rating on your rims takes into account an increase in pressure that occurs under heavy braking. If you aren't going down any long descents you might be ok at 160, but the handling is going to be terrible. Hitting the smallest pebble is going to launch your bike off of the road. While the rolling resistance goes up for smaller tires, there is a significant aerodynamic advantage (Rolling resistance is linear with speed and aero drag is quadratic. I think the break even point here is about 25mph). If the TT's you're doing are short enough that you won't mind the uncomfortable ride it might be worth going to a 20 on the front. The back won't make a difference. Also, there's no reason to run any clincher over 125 psi on pavement. If your TT bike hits anything hard enough to pinch flat at that pressure, you'll probably crash anyway.
     
  8. lugger

    lugger New Member

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    I absolutely love 20's!!!

    I use cheap Conti Sport 1000 700x20mms pumped all the way up to 145 psi on an Open Pro rear rim, 36 Swiss DT spokes with 105 hub and a Matrix Titan S (Trek?) front rim with Maillard hub. I don't race.

    I love 20's bacause they give that floating, skimming feeling, almost like I am not really touching the road at all. So nimble. And I don't know anything about rolling resistance. I do not think rolling resistance should apply to 20's because, as I mentioned above, 20's don't feel like they roll. Their rolling feels like skimming. Of course, I am talking here about aesthetics, not science.
     
  9. edd

    edd New Member

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    This emotive response was a nice balance, I get the science, it's the 145 psi and the wheel weight that gives the float I guess …

    ever have a stone launch you off-course ?
     
  10. edd

    edd New Member

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    I'm not sure the 20 mm tire is going to give that much aero advantage. It is the rotational aerodynamics of the front wheel that cause increase or decrease of turbulence that is the buffer at the front of the bike … so I'm lead to believe
     
  11. artmichalek

    artmichalek New Member

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    That's an interesting theory, but it doesn't match up with real world testing: http://www.cyclingnews.com/tech.php?id=tech/2005/features/conti_tech
     
  12. lugger

    lugger New Member

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    Never launched off course, but I can feel how that could easily happen on 20s. I feel like I am less stuck to the road, but that instability is balanced out by how fast and easy my bike responds to my movements and shifts of weight. I have done some touring and always enjoyed bopping around on my bike without packs after a whole day of riding with tons of gear. It felt, it was, weightless. Riding on 20s is like that. There is a bit less stability, but the bike is much easier to work. It's hard to describe exactly. With 20s, there is a lightness and quickness to the ways the bike responds to the road and to me. The floating feels like I am carried along and I just control my being carried along, a bit like x-country skiing actually, both kicking by pedaling and gliding over the road. And I don't hit many stones or branches or stuff anyway. I sort of jolt-swerve the bike around them or take the hit, especially over cracks in the pavement, by bending lower, flexing my elbows and gripping the handlebars tight or letting go for a second and then back to skimming. I guess I'm saying you can do a lot more instant finessing on 20s.
     
  13. Cat1RDR

    Cat1RDR New Member

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    Last year I ran the Conti. force and attacks. 21 (or 20... I think it's 21) in the front. I loved those tires, they cornered really well and rolled very quickly.

    I think rubber compound has more to do with cornering than width. I switched to cheap 23's on my training wheels and I was sliding all over the place.
     
  14. edd

    edd New Member

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    Interesting article ! I'll try to find the thing on rotational aerodynamics and post it. I think any kind of side breeze and wheel aerodynamics change.
     
  15. edd

    edd New Member

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    couldn't find it, will look again tonight. Found this though …

    http://www.analyticcycling.com/WheelsConcept_Disc.html
     
  16. artmichalek

    artmichalek New Member

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    That would be interesting. There are a lot of models flying around on flow over rotating disks and cylinders, but I haven't seen anything for a toroid yet.
     
  17. edd

    edd New Member

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    Can't find it, but I'm sure it was on this site somewhere, Not sure exactly what it said but it left me thinking that the hub, forks and rotatiing spokes in combination create a unique drag that effects the aero dynamics of leading end of the bike and not just the rim depth and tyre to rim interface.

    anyway for what its worth …

    http://www.slowtwitch.com/mainheadings/techctr/torque.html
     
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