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  • ot: steer tube tolerances

    can anyone tell me about the tolerances for steertubes of bicycle forks. Someone in another forumn is telling me that they are not exactly the size they are advertised out to be (i.e 1.125 inch), which is totally acceptable and reasonable, but that person is saying that this tolerance will not allow my model of stem to work.

    http://s111.photobucket.com/albums/n122/elninio123/

  • #2
    I can almost see why he would say that. Unless you have slots or some way for the four bolts to slide a bit then how can yours clamp down hard enough to make up the difference in the tubing OD?
    That being said...Look at any mfg tubing spec list. Most good quality tubing is pretty darn close to the advertized size.
    Now you get to do some R+D...to see if he is correct.
    Turn a plug a few thou over...see if you can slide your rig on it...turn the plug down a few thou under and see if it'll tighten up enough. Can you still get the bolts in if you have to take the loose clamp side off etc...
    All stuff you have to figure out before you start trying to market your gadget!
    Russ
    I have tools I don't even know I own...

    Comment


    • #3
      tolerances

      Elnino,

      You can look that up on the onlinemetals website. 1"Al. 6061 tube has a tolerance of +/-.004"......

      Nothing that would make that beautiful part you made not work. Sounds to me like that other person is trying to keep you from marketing your part.

      FWIW
      Lenord

      Comment


      • #4
        Tolerances

        Torker,

        Unless he has no room at the bottom of the blind holes, the side with 4 bolts, he should easily be able to make up the tolerances in tubes of Al. or steel. Looks like he has 3/16" of room there. Less room for the side with 2 bolts, but it sure looks like it will work from that blown up picture of the part. He may want to through drill those 4 holes to make sure, but I suspect it isn't needed.
        20 minutes of testing with different OD tubes to make sure would not hurt a thing.

        What kind of metal is that part made from anyway ? Sure looks nice !

        Lenord

        Comment


        • #5
          [QUOTE=Elninio].............. but that person is saying that this tolerance will not allow my model of stem to work.[QUOTE]

          So what are his credentials to make that statement?

          IF what he says is true, it should be a easy enough work around by simply widening the saw cut in the one end a putting slot in one hole of the other to allow the bolt to still mate up (or maybe slightly oversize bolt holes). You might also have to make the holes larger and sell it with a bushing kit to fit differant manufactures of bikes. No big deal and it allows you to customize fit. Could actually make a better product by doing so.
          - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
          Thank you to our families of soldiers, many of whom have given so much more then the rest of us for the Freedom we enjoy.

          It is true, there is nothing free about freedom, don't be so quick to give it away.

          Comment


          • #6
            bicycle steer tubes

            I can tell you that the steer tube on my GT mtn bike fork was exactly 1 1/8" OD, because I used part of it for a bushing sleeve that I needed for my lawn tractor. However the fancy paint that was on mine added considerable thickness to the OD. This was from my unused original non suspension fork.

            I would suspect that anything in the upper price ranges, would use some higher end chromoly tubing. I think modern forks are made of good material even in the cheap stuff. I had a lower end Schwinn 10 speed in Jr high school. I crashed it one time into a curb at a fairly decent speed. The frame bent at the top tube and the down tube about 2 inches from the lugs or junctions where they met the frame fork tube. The fork was unhurt. I suspect that the old design where the stem went a good distance down the fork tube and was secured with a wedge, was a heavy, but a stout design.

            It looks like it works just fine in the first pictures. Nice looking stem.

            Comment


            • #7
              It's been 10 years since I morphed from bicycle mechanic to machinist, but as I recall, steer tubes of all diameters (25mm, 1", 1-1/8", 1-1/4") measure within about 3 thou of nominal. I don't think you need to worry.

              Comment


              • #8
                here is the forumn im posting in

                http://www.bikeguide.org/forums/show...t=91247&page=3

                although i dont agree with what hes saying, its gonna be hard to prove him wrong..(lots of research)

                Comment


                • #9
                  Lotta little snot balls on there huh? Oh...and a whole lot of jealousy I'm thinking also.
                  I have tools I don't even know I own...

                  Comment


                  • #10
                    Originally posted by torker
                    Lotta little snot balls on there huh? Oh...and a whole lot of jealousy I'm thinking also.
                    that's about how I read it!
                    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
                    Thank you to our families of soldiers, many of whom have given so much more then the rest of us for the Freedom we enjoy.

                    It is true, there is nothing free about freedom, don't be so quick to give it away.

                    Comment


                    • #11
                      one guy there seemed to know what he was talking about, but for the most part that is some really funny reading, a mind is a terrible thing to waste.

                      just tell 'em its made of billet and all those ignorant naysayers will be be full of oooooo's and ahhhhhh's
                      .

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                      • #12
                        Considering the level of ignorance and illogic in the few posts on the "bikeguide" forum manifest in the postings referenced by elninio, I would definitely find a different forum for info. www.bikeforums.net has a lot higher percentage of knowledgeable types posting and they have a BMX
                        group as well as builders groups. "bikeguide.org" might do it for laughs but not as a creditable source of information if this is an example.
                        Steve

                        Comment


                        • #13
                          if only i could sell a few, and those guys could tell 2 freinds, and then those can tell 2 more a couple of guys are interested in my stem but lost interest a few days later (probably after having read those other posts), i gotta counter that guy's comment!

                          Comment


                          • #14
                            Chris...sometimes you have to bite the bullet...if you want...you gotta give one to a pro to try.
                            Hmmmm...I could talk to my nephew to see if he'd try one out for you.
                            His seal of approval could go a long ways in the BMX world.
                            BTW...I did this with one of the air shifters that I build for mud racing buggies.
                            I picked one of the front runners in the class below me and sponsored him a complete air shifter outfit. Did a lot of "free" R+D cuz it was a 3 speed shifter(shifted twice) where my usual was a two speed that only shifted once.
                            After that I sold enough to make it well worth my time.
                            Russ
                            I have tools I don't even know I own...

                            Comment


                            • #15
                              that would be awsome

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