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  1. #1
    RoadBikeReview Member
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    Advantages of oversize steel tubing

    What are the advantages to having a steel frame made with OS tubing with all else being equal? To help frame the question weight is not an issue and stiffness is secondary to comfort.

    The reason -- I am looking at a stock Bob Jackson that is available either in standard or oversize tubing. The price difference is less than $30.00 at current exchange rates so cost is not an issue.

    Your thoughts are appreciated.

  2. #2
    n00bsauce
    Reputation: Mel Erickson's Avatar
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    You can build either to about the same stiffness and comfort levels. The main differences are weight and aesthetics. Oversize will probably be slightly lighter and slightly uglier, IMO of course.
    "Those who can make you believe absurdities can make you commit atrocities." Voltaire

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  3. #3
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    If there is no real need for the OS, go with standard, it will be stronger and more durable.

    OS tubing gives you slightly better stiffness / weight ratio at the expense of really thin walls which are easily damaged.

  4. #4
    RoadBikeReview Member
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    strength increases as tube diameter increases. Wall thickness can also be decreased, resulting in a tube that is about the same weight as a smaller diameter tube but is stiffer. Downside is decreased wall thickness makes it more susceptible to dings and may sacrifice comfort. Sounds like the standard dimension would be better for you.

  5. #5
    RoadBikeReview Member
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    I personally prefer standard tubing for unloaded/light load riding.

  6. #6
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    The "new" standard, 28mm top tubes and 32mm down tubes, replace the older 1" standard which referred to the 1"/25.4mm top tube and 28.6mm downtube.

    The engineering of it is, the tube's resistance to flexing or stiffness increases dramatically with small increases in diameter. It's something like a 10% increase in diameter results in a 100% increase in stiffness. Changes in wall thickness are not that much of a factor, so once you increase the tube diameter, you can decrease the wall thickness and actually wind up with a stiffer, yet lighter tube.

    The reason you want the lighter tube is, few cyclists could be convinced to ride a stiffer, yet heavier bike. A stiffer bike feels better for many cyclists, particularly bigger riders and sprinters. As long as the resultant ride does not beat you up or make the bike difficult to control on rough surfaces, there's little downside to a stiffer frame.

    Another issue OS tubes can address is shimmy. A contributing factor to shimmy is a flexible top tube, especially in larger frames. Larger diameter top tubes resist the twisting forces inherent in shimmy, reducing the likelihood of its occurrence.

    Finally, OS tubes can make a frame which is less likely to flex under intense pedaling loads, which often leads to annoying front derailleur rub.

    But as other posters have pointed out, reducing the wall thickness of OS tubes to reduce the weight can lead to easier to dent tubes. Some manufacturers have responded by formulating tubes that are more dent resistant. Consulting with a framebuilder to see which tubes would offer similar dent resistance to 1" standard tubes would be your best bet.

    I think the new OS tube sets are a great idea. More stiffness is not necessarily an improvement and I doubt riding OS tubes versus standard tubes would mean the difference between standing on the podium and being pack fodder, but I believe frames can be built stiffer without riding harshly. In my opinion, most of the comfort of a frame comes from the shock absorption of the fork, and the right tire size and choice of pressure.

  7. #7
    waterproof*
    Reputation: Creakyknees's Avatar
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    good answers above.

    and don't worry about the strength of OS tubes to routine dents etc... think of it this way, it's no worse than any of the millions of aluminum frames.
    * posted by Creakybot 2013 all rights reserved.
    * not actually waterproof.

  8. #8
    eminence grease
    Reputation: terry b's Avatar
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    Quote Originally Posted by Creakyknees
    good answers above.

    and don't worry about the strength of OS tubes to routine dents etc... think of it this way, it's no worse than any of the millions of aluminum frames.
    Trying to get to 16,000 tonight?
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  9. #9
    RoadBikeReview Member
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    Oddly enough, I have a BJ in 853OS. Mine's custom though, as I tend to odd sizes here and there.

    How can I put it?

    I LOVE IT!!!!!

    Though it's not as fast as my previous BJ - spousal unit reckons that's due that I raced my last one in 1973 - I really love the ride. It was designed to my tastes - I never liked riding a long way when I did it seriously and nothing's changed with old age, but I do like to get a move on at times and the folk I've ridden with over the last few years did insist on the odd sprint for a coffee bar.

    Given how far I ride, it isn't a harsh ride. My biggest vote for my BJ is probably the CF Trek Madone I sold myself on beginning of this year, and recently sold on EBay after a couple of thousand miles and a warranty replacement frame for a cracked headtube...

    I visited BJ's place on my last trip back to my native England in 2005. They have a room off the main bike shop that has nothing but steel frames and bikes, all their frames are built and painted in that building too.

    Whichever way you go, you won't be disappointed with a BJ. Fortunately, my photos are on a different computer, so I won't drip on any more ;)

    Regards

    Dereck

  10. #10
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    I have found that the more oversize a steel frame is, the more it rides like aluminum. I had a newer oversize Gunnar which seemed harsher than a steel frame should, and it wasn't my fastest bike either. I've got a 2003 LeMond Buenos Aires with pencil thin seat stays which makes me feel fresh on the longest ride.

    I've found that a standard steel frame made from 853 offers as good a ride as one could ask for. But comfort is pretty important to me.

  11. #11
    waterproof*
    Reputation: Creakyknees's Avatar
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    Quote Originally Posted by terry b
    Trying to get to 16,000 tonight?
    no, not especially.
    * posted by Creakybot 2013 all rights reserved.
    * not actually waterproof.

  12. #12
    old school drop out
    Reputation: laffeaux's Avatar
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    I think others have covered the pro/con of over-sized tubes pretty well. From Bob Jackson's web site, it's not clear exactly what is entailed in the "OS" tubeset - other than ovalized chain stays. My main ride has an over-sized down tube - 34.9mm instead of 31.75mm - while the remaining tubes are 28.6mm. It rides nicely and I prefer the aesthetics of the one larger tube. ;) It's probably worth calling and asking what the exact differences are.

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