Your most recent bike related purchase?

Discussion in 'The Bike Cafe' started by steve, Oct 30, 2013.

  1. danfoz

    danfoz Well-Known Member

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    Nice. Sounds like you got 'em on alright but for others daring to take the plunge, aside the obvious possible allergy thing, they do tend to creep into spaces inside the rim bed. It seems more important than with butyl to make sure that once plopping the last of the tire onto the rim bed during install it's important to do a quick check around the rim and make sure no bit is trying to sneak out from under the tire before fully inflating. Which brand did you get btw (I'm using Vittoria)?
     


  2. Mansmind

    Mansmind New Member

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    I'm using Vittoria as well. Funny you should mention the creeping thing. I noticed it was significantly more difficult to get everything "in the tire". Fortunately I'm anal about checking around before inflating! It's pretty obvious they are more supple than butyl just by handling them. I'm sure that translates to some extent in the ride it's just hard for me to pick out right now. I've changed a lot of things recently though. I've gone to carbon deep rims, the wider rtire bed, different tires, and now latex. I'm still figuring out pressures, but it will be much lower than the 120 psi I use to typically run.
     
  3. danfoz

    danfoz Well-Known Member

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    For the wider rim it is recommended by HED to go with lower pressure (sounds like your rim's manufacturer as well as). More air volume means less pressure is needed. Apparently excess pressure will cause the spokes to decompress, I'm not privy to all the sordid details but it doesn't sound like an ideal scenario. Also possibly less than ideal things happening to the CF rim walls vs typical alloy rim walls as they heat up on a fast decent? I'm currently running 25c Conti 4-Seasons, which while having a sidewall max indicated pressure of 120psi, Conti recommends 100psi for my bodyweight of 160lbs+/-. On my HED C2's its recommended to run lower than 90psi to compensate for the extra width. On paper that seemed way too low but after running some different pressures I've settled on about 85psi for the rear and 80psi for the front give or take. I went a little higher one day and was surprised how harsh the ride was at 90+psi on the rear. 80psi on a 19mm wide rim was entering pinch flat territory, not so on the 23mm wide rim. Even at that low pressure the tires feel responsive, not sluggish as they may have on a narrower rim.
     
  4. Mansmind

    Mansmind New Member

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    Yeah I know they should be lower, I just haven't dialed it in yet. I'm running Enve 6.7s, and although I can't recall the exact rim widths I know they're wider than normal (and the front is wider than the back). I'm using 23mm tires (my S5 would probably rub with wider ones) and I'm currently running a little over 90psi. I'm a heavier rider though (190 lbs). I've varied between 90 and 100 and still haven't settled into a place that I think is perfect...we'll see. As you mentioned, I've yet to feel them as "sluggish" at all.

    Conti GP 4000s tires
     
  5. danfoz

    danfoz Well-Known Member

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    SWEET! Once I'm back in the black I'll be adding some nicer wheels to my SuperSix.
     
  6. Mansmind

    Mansmind New Member

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    Yeah I did an initial review of them over in the review section. So far I like them... but they are different than shallow aluminum for sure..lol.
     
  7. alienator

    alienator Well-Known Member

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    Mansmind, from what rims did you switch to the Enve's? Danfoz is right that higher pressure will result in higher temps in the air inside a tube, at least that's what was found from Sr. Boltzmann's distribution. Note that is advised to NOT use latex tubes in CF clinchers on long and/or twisty descents as the latex tubes will fail at a lower temperature. No doubt you've discovered that latex tubes requiring pumping up a lot more.
     
  8. Mansmind

    Mansmind New Member

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    I've never ridden anything but aluminum rims. Various ones over the years. I think my favorites were Velomax Circuits (which I still have). I was NOT aware of the latex tubes not being good for downhill stuff, although fortunately for me while my rides are very hilly, there isn't anything extremely long or twisty. (1 mile long or so).

    Actually they don't deflate as quick as I thought they would. I expected to walk out the next day and they would be flat. They had lost 10 psi or so over-night. I top off the air before I ride everytime anyway, so it's not a big deterrant for me.

    To answer your first question more directly, I put the Enve's on my Cervelo S5, which came with Fulcrum 5.5s (which I wasn't too fond of).
     
  9. danfoz

    danfoz Well-Known Member

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    That's certainly worth considering on a ride like the haute route or some other climbing intensive course. I had heard that latex tubes were not available for a short time in this country (not including tubular tire inners). Do you know if that is the case or is it just park bench rumor? Certainly seems like tube failures could be responsible for some sort of embargo, at least until some legal way was found to circumvent.
     
  10. alienator

    alienator Well-Known Member

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    I haven't heard that, but I do know that butyl tubes have also failed under braking on CF clinchers. I've not seen anything on any other forums about a shortage of latex tubes, well, except for some tubes that just run out of stock.
     
  11. Mansmind

    Mansmind New Member

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    We have been talking about Assos lately. For those interested there is a guy on ebay selling the s7 equip bibs for $233
     
  12. danfoz

    danfoz Well-Known Member

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    The S7 stuff is mucho dinero. Colorado Cyclist is running a decent sale on the S5 stuff: http://www.coloradocyclist.com/product/display/90205
    As little as $150 can get one a ticket to the dance. I'm really glad I tried the stuff on at a local shop before ordering. I'm pretty lean but thick in the thigh with some muscular glutes, and at 5'9" and 160lbs needed the XL knickers. For added reference I wear Pearl Izumi lowers in a LG. Their info packet says with time one will migrate to the smaller sizes but I'm not seeing it. First 2+ hour ride in them on Sunday and the fit and feel were glorious btw, I'm confident saying better than anything I've ever owned before.
     
  13. alienator

    alienator Well-Known Member

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    While I love my Assos bibs, I actually prefer my Giordana Silverline bibs. My Giordana Forma Red bibs equal the performance of the Assos bibs. My Silverline bib tights are also the beez kneez.
     
  14. Mansmind

    Mansmind New Member

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    I have one pair of S5 and one of S7, I can definitely feel the improvement in the S7. At what they cost though it's not like you're going to have a closet full! I do know what I tend to be reaching for when riding now...and it isn't all the Pearl and LG stuff I have. That's wild on the sizes, I'm almost 6'1" and over 190 (at the moment) and L fits me perfectly. I've been dropping pounds though and will continue to until I hit 185 or so. Past that I start looking anorexic.

    Quote:
    Originally Posted by danfoz .
    The S7 stuff is mucho dinero. Colorado Cyclist is running a decent sale on the S5 stuff: http://www.coloradocyclist.com/product/display/90205
    As little as $150 can get one a ticket to the dance. I'm really glad I tried the stuff on at a local shop before ordering. I'm pretty lean but thick in the thigh with some muscular glutes, and at 5'9" and 160lbs needed the XL knickers. For added reference I wear Pearl Izumi lowers in a LG. Their info packet says with time one will migrate to the smaller sizes but I'm not seeing it. First 2+ hour ride in them on Sunday and the fit and feel were glorious btw, I'm confident saying better than anything I've ever owned before.
     
  15. Mansmind

    Mansmind New Member

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    So little time and so many things to try..lol

    that reminds me of this operations guy that stood in front of the board of directors of a company and actually said to start his talk "so little time and so many asses to kiss"
     
  16. doss

    doss New Member

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    Just ordered a new 1 1/4 crown reducer so I can put my free 1 1/8 fork on my free bmc sl02 frame... Thanks to fsa actually having great customer service. Sent from my iPhone using Tapatalk
     
  17. urge2kill

    urge2kill Member

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    Friction?


    Increasing gas temperature increases gas pressure when the gas is in an enclosed space (Gay-Lussac's Law i.e. Amontons' Law), but I don't think it works the other way around.

    As far as I know, increasing the molar density should buffer against changes in air temperature. A larger amount of gas will require more kinetic energy to achieve an equal rise in temperature.

    n/V = P/RT
    n/V is molar density.
    P is pressure
    T is temperature
    R is a mathematical constant

    If over-inflating your tubes somehow leads to more friction, that miiight do it. I don't know. Ask a chemist and/or physicist. However, per the calculations below, you would have to raise the temperature quite a bit to see a significant increase in psi.

    Ratio of temperature increase to pressure increase:

    PV = nRT
    One form of the calculation assigns R=0.08206, and uses the units: moles, atmospheres, Liters, and Kelvins.
    Moles and Liters (n & V) will be held constant.

    Conversion factors:
    1 atm = 14.7 psi
    1 K ∝ 1 C°
    1 K ∝ 1.8 F°

    TR = P
    T x 0.08206 = P
    An increase of 0.08206 atmopsheres, or 1.2 psi, per degree Celsius.

    If we're talking Fahrenheit.
    1.2 ÷ 1.8 = 0.67
    That's 0.67 psi per degree Fahrenheit.

    So the corresponding change in pressure shouldn't be a problem unless you are increasing the temperature by something like 15 degrees Fahrenheit.
    Just don't fill your tube with air that is significantly warmer or cooler than what it will be exposed to during your ride. So don't fill it inside your house, and don't fill it in the morning or at night while the temperature is low.

    That reminds me. My most recent purchase was a Silca floor pump.
     
  18. danfoz

    danfoz Well-Known Member

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    Friction?

    Rim wall deformation in combination with increased pressure due to increased temperature resulting from friction causing the tire to potentially free itself from the rim.

    http://themanleyreport.blogspot.com/2009/10/levis-granfondo-carbon-clincher-failure.html
    http://www.bikeradar.com/gear/article/are-carbon-fiber-clinchers-safe-34521/
    http://www.roadbikeaction.com/Tech-News/content/71/4808/Tech-Report-The-Real-Story-Behind-Carbon-Clinchers.html

    [​IMG]

    Does the red signify a change in temperature beyond 15 degrees? I dunno. My swag tells me something more like an increase in excess of 100 degrees on a rim/pad combo that can't dissipate heat adequately when combined with a rider who enjoys fanning the brakes on a 30 minute long descent. As I'm neither a chemist or a physicist my opinion should be taken with a grain of salt and a bona fide expert should be consulted for the details.

    That's some fancy math. Based on my X-rays my dentist says my molar density is fine but that I shouldn't let up on a nutritious diet containing adequate amounts of calcium and sunshine.

    Congratulations on the pump.
     
  19. urge2kill

    urge2kill Member

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    I cheated by looking at my old chemistry notes. [​IMG]

    I was only speaking on the relationship of temperature to pressure. Of course, increased temperature alone can lend a thing to deformation.

    That looks like thermal imaging, which is just a camera photograph that detects wavelengths below what our eyes can detect.
    Basically, the wavelengths of "light" emitted by an object correspond to its temperature. The image is showing us the wavelengths emitted, so it's showing the heat on the outside of the object, but not the heat of the air inside the tube.
    Nonetheless, the bikeradar article mentions "outward pressure" as a contributing factor.
     
  20. urge2kill

    urge2kill Member

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    Second thoughts on my proposal that change in temperature necessarily changes psi. If the temperature of the surrounding air is increasing/decreasing too, there might be no change in net pressure against the tire.
    I will do an experiment when my high-precision Silca pump arrives. I will see if I can get the psi to something higher than where it started just by bringing my bicycle into the warm house.
     
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