Not signed in (Sign In)
    • CommentAuthorrobin623
    • CommentTimeNov 14th 2012
     
    Hi All,

    I just purchased a Schwinn bicycle from the Voyageur 2 series and the tire pressure noted on the tires should be 44 to 73 psi. All my riding is done on paved streets. Considering that, could you please recommend a more exact pressure for my tires?

    Thanks in advance
    •  
      CommentAuthorSigurd
    • CommentTimeNov 14th 2012
     
    I would inflate to towards the high end of that range for pavement riding under normal conditions.
    •  
      CommentAuthorsvelocity
    • CommentTimeNov 14th 2012
     
    It depends on a number of factors, tire size, tire width, terrain, etc. The biggest factor is your weight. The lighter you are the less pressure you have to run and vise versa.

    You need to experiment with it. I would start as Sigurd suggests and run your pressure at the higher range. If you find the ride to be harsh back the pressure off to where you feel you still roll fast but the edge is taken off the bumps and cracks. If you back it off to much you will find the ride to be sluggish and you will also run the risk of pinch flats. Also a general rule of thumb is you can run the front tire at a lower psi than the rear. For example I weigh 200lbs and my tires are 700c x 32. The are rated up to 100psi but I run the front at 75 and the rear at 85.

    Lastly use the same pump when you do this experiment.
    • CommentAuthorsynthetic
    • CommentTimeNov 14th 2012
     
    100psi tires should be run at 100
    •  
      CommentAuthorsvelocity
    • CommentTimeNov 14th 2012 edited
     
    synthetic:100psi tires should be run at 100

    False

    No tire I've have ever seen says one pressure. Usually they have a range of psi. On my commuter the range is 50-100psi. That means I can experiment and have them pumped up to any pressure I please as long as it says between that range.
    • CommentAuthorJSnook
    • CommentTimeNov 14th 2012 edited
     
    robin623:Hi All,

    I just purchased a Schwinn bicycle from the Voyageur 2 series and the tire pressure noted on the tires should be 44 to 73 psi. All my riding is done on paved streets. Considering that, could you please recommend a more exact pressure for my tires?


    Unless you're pavement is smoother than the areas I ride in SD I'd start around 50 to 55 psi and go from there with those tires. My experience is most people run higher pressure than they need to which leads to a harsh ride and worse rolling resistance.
    •  
      CommentAuthorVelo Cult
    • CommentTimeNov 15th 2012 edited
     

    Unless you're pavement is smoother than the areas I ride in SD I'd start around 50 to 55 psi and go from there with those tires. My experience is most people run higher pressure than they need to which leads to a harsh ride and worse rolling resistance.


    Yes on all accounts. I would add that ALL pavement is faster and more comfortable at lower pressure so long as you have a supple tire. It's counter intuitive and goes against all we've known up until now but it's true. High pressure only leads to more resistance and slower riding. A large, supple tire at low pressure is considerably faster than a stiff tire at low pressure and any tire at high pressure.
    •  
      CommentAuthorbikingbill
    • CommentTimeNov 15th 2012
     
    Higher pressure FEELS faster, but it's not in the examples above. The road feel gives you the illusion of speed.
    •  
      CommentAuthorbilld
    • CommentTimeNov 15th 2012
     
    I still don't think it's as simple as lower = faster. There's going to be an optimal point based upon multiple variables including the smoothness/roughness of the road, the suppleness of the tire, the weight of the bike+rider+gear.
    • CommentAuthorShady John
    • CommentTimeNov 15th 2012
     
    I agree with Billd. This is what I recall from my reading on tire pressure/rolling resistance a few months ago:

    1. At THE SAME PRESSURE, a narrow tire and a fat tire will have the same contact area with the road (force = pressure * surface area; force = weight of bike + rider, which is kept constant)
    2. The fatter tire deforms less than the narrow tire, leading to lower rolling resistance
    3. Lower rolling resistance does not necessarily mean overall "greater efficiency." Factors such as tire/wheel weight and wind resistance tend to favor the narrow tire, while increased road surface irregularity (bumps) tends to favor the fat tire
    4. FOR A GIVEN TIRE, decreased pressure should increase rolling resistance because you will have a larger contact patch, with correspondingly greater tire deformation (remember force = pressure * surface area). But again, this is balanced in the real world against surface irregularity and traction issues (off-road especially), with the ultimate limiter of the pinch flat risk.

    Mountain bikers (not me, I'm a dinosaur) are moving towards tubeless wheel/tire systems run at low pressures (no pinch flats), and also larger diameter wheels (29ers) (again, not me, because not only am I a dinosaur, I'm also not very tall, meaning a 29er in my size has kind of extreme geometry). This is for traction in loose surfaces, and to allow for easier rolling over obstacles several inches high.
    •  
      CommentAuthorVelo Cult
    • CommentTimeNov 15th 2012
     
    Right. Not all tires can be fast at lower pressures. It must be a supple high end tire. In every study a bigger more supple tire at low pressure always wins. Most big tires are not supple, they are the exact opposite. They will prevent flats and last longer but they certainly will ride like crap and go slower.
    •  
      CommentAuthorbikingbill
    • CommentTimeNov 15th 2012
     
    Velo Cult:Right. Not all tires can be fast at lower pressures. It must be a supple high end tire. In every study a bigger more supple tire at low pressure always wins. Most big tires are not supple, they are the exact opposite. They will prevent flats and last longer but they certainly will ride like crap and go slower.


    Yes. The Marathon Pluses were not supple at all. The Marathon Racer Evolution tires are. They are rated (in 26 x 1.5) at 55 to 85psi. Running them at 75-80psi.
    • CommentAuthorsynthetic
    • CommentTimeNov 15th 2012
     
    Most of those who race with 700x23-25c tire run 100-105psi
    •  
      CommentAuthorSigurd
    • CommentTimeNov 15th 2012
     
    There are so many subjective factors impacting on optimal tire pressure, including (but not limited to) wear, braking efficacy, expected surface conditions, tire model/size/design, comfort, rolling resistance, traction under various conditions, that is is impossible to give an answer that is accurate for all riders, on all tires, and in all conditions.

    But if we focus on speed alone (and nothing else) I refuse to buy into the dogma that "softer equals faster" until I see credible evidence supporting it - which for me would include that the majority of the pro peloton and track racers decide en masse to reduce tire pressure for speed races (such as a TT).
    •  
      CommentAuthorbikingbill
    • CommentTimeNov 15th 2012
     
    Track? Smooth Surfaces, run high pressure.

    I did read that there has been some switch to 25mm from 23mm or narrower on the road.

    Take wider tires run at lower pressures: VeloNews reported that in this year’s Giro d’Italia, many teams used 25 mm-wide tubulars even on smooth roads. For more than 30 years, 21.5 mm tubulars were the standard tires in professional racing. Back then, pro racers used 25 mm tires only on the brutal cobblestones of Paris-Roubaix, “The Hell of the North” (below in the mid-1990s).



    What caused the change to wider tires? Most important was the realization that lower pressures don’t make tires roll slower. This means that wider tires – which have to run at lower pressures – can be as fast or faster than narrower tires. Once this was established, at least partially through Bicycle Quarterly’s research, equipment makers could test wider tires in the wind tunnel and on the road. And they apparently found that wider tires perform better even on smooth roads. A mechanic explained: “You get more grip, more comfort; the guys like it.”

    As to my commute, the roads are so craptastic (Vulcan in particular) that I have opted for fat (40mm) tires. Particularly at night where I may miss some pothole.
    •  
      CommentAuthorbatmick
    • CommentTimeNov 15th 2012
     
    I "widened up" my Gator Hardshells from 23mm to 25mm and have decreased pressure to 85-90 instead of the 100+ I had been running. No impact on my averages but it definitely feels a little better.

    Will need new tires pretty soon and I think I will give the 28s a shot.
    •  
      CommentAuthorbikingbill
    • CommentTimeNov 15th 2012
     
    batmick:I "widened up" my Gator Hardshells from 23mm to 25mm and have decreased pressure to 85-90 instead of the 100+ I had been running. No impact on my averages but it definitely feels a little better.

    Will need new tires pretty soon and I think I will give the 28s a shot.


    I'm running 75-80psi on 40mm wide tires, but I'm heavier than you are :-)

    (not to mention the 50lbs bike and cargo)
    •  
      CommentAuthorbilld
    • CommentTimeNov 15th 2012 edited
     
    bikingbill:Track? Smooth Surfaces, run high pressure.
    Indeed.

    Jobst Brandt's rolling resistance tests back in the 80's were done on a smooth surface and showed higher pressures to have lower rolling resistance.

    Unfortunately, he did not consider rougher surfaces, like southern California roads, in his tests and it turns out that the surface is important in determining the optimal pressure. Lower pressures do better with rougher surfaces.
  1.  
    My narrowest tire is Continental touring 700 x 28c (rear 80 psi, front 70) and I have been using this size on my old commuter year round: Fall, Spring, Summer, and the harsh winter season in Toronto. I find it ideal in urban commuting which balanced the need for speed, efficiency, and suppleness.

    On my Panasonic touring deluxe I use a Michelin Urban tire (heavier due to thicker thread) 700x35c. Front at 65 psi and Rear at 70 psi. I had it pumped close to its maximum at 95 psi but the ride felt to harsh
    • CommentAuthorJSnook
    • CommentTimeNov 16th 2012
     
    Tom Boonen won Paris Roubaix this year on cotton casing FMBs at 60 psi. They were 27mm tires but measured a bit bigger than 28.

    In addition to going to 25C tires the pros are also going to wider rims. Above someone mentioned narrow tires would be more aero but in fact wider tire/rim combos are often more aero than narrow ones - it all comes down to lots of factors beyond just the width. Manufacturers are realizing they can do more with rim shape to cheat the wind including cross winds by making the rim wider and using wider tires.
    •  
      CommentAuthorbikingbill
    • CommentTimeNov 16th 2012
     
    JSnook:Tom Boonen won Paris Roubaix this year on cotton casing FMBs at 60 psi. They were 27mm tires but measured a bit bigger than 28.

    In addition to going to 25C tires the pros are also going to wider rims. Above someone mentioned narrow tires would be more aero but in fact wider tire/rim combos are often more aero than narrow ones - it all comes down to lots of factors beyond just the width. Manufacturers are realizing they can do more with rim shape to cheat the wind including cross winds by making the rim wider and using wider tires.


    Some recumbents (typically CF very low ones) use tires and rims that match the width of frame itself. Most notably in the Nocom.



    No, I would not commute on that.
    • CommentAuthorJSnook
    • CommentTimeNov 19th 2012
     
    That recumbent looks fast. I bet that chain weighs a few pounds. Seems like a belt drive and internally geared hub could clean that thing up a little.
    •  
      CommentAuthorbikingbill
    • CommentTimeNov 19th 2012
     
    JSnook:That recumbent looks fast. I bet that chain weighs a few pounds. Seems like a belt drive and internally geared hub could clean that thing up a little.


    The bike is sub 20lbs. Maybe even 17 lbs. cant get a custom belt that size.

    Called the NoCom, for no compromises. Yes, fast.

    I rode a bike almost this low down Torry Punes at over 50mph in the car lane in 1998 or so.
    • CommentAuthorShady John
    • CommentTimeNov 21st 2012
     
    I assume people have tried, and discounted, front wheel drive for recumbents? The drivetrain would be so much simpler. You would probably want to do it with an internally geared hub. Traction would be an issue, especially climbing. I remember riding Big Wheels when I was a kid. But for a bike like this, I imagine you'll never be going slow enough for the traction limit to matter.
    •  
      CommentAuthorVelo Cult
    • CommentTimeNov 22nd 2012
     
    The study's and evidence are out there. I say test it yourself though. I did and was shocked. I thought it was all BS too.

    Now if you want to say why aren't the pro's doing it I have two answers for you. 1) they are. They've gone from 700x20 with 120 to 160psi to 700x25 in most cases with 72psi. 2) Even though a larger tire is technically faster over the entire course racers at that level don't care one bit about that. They only care about the sprint and not just the finish line sprint. They care about the break away's and fast burst of speed. A slightly lighter tire will be faster for that and really that's more important to them than an even faster sustained tire that's a hair slower in the sprint. For them the perfect compromise is 700x25 with 72psi. For the rest of the world going larger and lower pressure is even faster since we don't depend on the sprint but want to be faster and more comfortable over a longer ride.

    Again, don't knock it til you try it. Get a real soft supple rando tire and do your own science. The scientists have all done their studies and it's all out there now, high pressure tires are slower. Fact. It's counter-intuitive so test it yourself. I was so reluctant to all the low pressure stuff I just went out and did it to prove them wrong but proved them right instead. I was once a very high level racer and my science showed my rando to be 8 to 10% faster on normal smooth pavement and got even more efficient as the pavement worsened. You MUST get real rando tires designed for this though. Riding a regular tire at low pressure probably won't do much for you.
    •  
      CommentAuthorbikingbill
    • CommentTimeNov 23rd 2012
     
    ShadyGaga:I assume people have tried, and discounted, front wheel drive for recumbents? The drivetrain would be so much simpler. You would probably want to do it with an internally geared hub. Traction would be an issue, especially climbing. I remember riding Big Wheels when I was a kid. But for a bike like this, I imagine you'll never be going slow enough for the traction limit to matter.


    There are two types.

    1. Chain run through pulleys to the front wheel.

    I rode this from 1999 to 2004:



    It was fast, set my best Fiesta Island 20KM TT on it (31:05) in 1999.

    Why did I switch? On steep hills that fork would move to and fro with every pedal stroke, and yes ... I could sometimes slip the front wheel.

    2. Entire front end pivots, pedals and all.



    This is simple, you can involve more muscles ... the drawback? Steep learning curve.
    • CommentAuthorShady John
    • CommentTimeNov 23rd 2012
     
    That thing looks awesome! I've never ridden a recumbent but I would love to try something like that.
    •  
      CommentAuthorbikingbill
    • CommentTimeNov 25th 2012
     
    ShadyGaga:That thing looks awesome! I've never ridden a recumbent but I would love to try something like that.


    Easily ridden no-hands, once you figure out how to pedal it.
    •  
      CommentAuthorbikingbill
    • CommentTimeNov 25th 2012
     
    I lowered the pressure on my 40mm Marathon Racers to 75psi, from 80. Noticeable ride and handling improvement.
    •  
      CommentAuthorsvelocity
    • CommentTimeNov 26th 2012
     
    Since this thread started I dropped my commuting bike tires (700c x 32mm) psi from 75/85 front/rear down to 60/70. That was too low as I felt the tires to be just a bit squirrelly in the corners. So I pumped them up to 70/80 and that really seems like the sweet spot between compliance on the bumps, rolling fast, and holding in the corners.
  2.  
    Does anyone here follow Sheldon Brown's recommendations? More specifically, this very scientific-looking article he cites from Bicycle Quarterly. If so, please let us know what your experience is with this method.
    •  
      CommentAuthorbikingbill
    • CommentTimeNov 27th 2012
     
    Looks like I should be running far lower pressures, based on that article. Hmmm...