Rear sprocket bolts.

Discussion in 'Dyna Models' started by porkchop, Apr 18, 2009.

  1. porkchop

    porkchop Active Member

    Do the rear sprocket bolts realy need to be replaced once they have been removed? If there grade 8 and threaded into a aluminum hub i wouldnt think they could stretch. I had been told to replace them by a dealer and an indy said it wasnt needed. I find it hard to beleive that they would need to be replaced. I have allready reused them a couple of times now and torque them to spec with out any issues.
  2. porkchop

    porkchop Active Member

    Well im not against replacing them but i just figured that the aluminum threads in the hub would stip out before the grade 8 bolt would stretch or even weaken. I do use lock tight and the torque spec is only 55 to 60 ft lbs. maybe i will just go ahead and replace them any way.
  3. bwalsh22

    bwalsh22 Junior Member

    I just went through that with mine, for the price, easier to just replace them.
  4. jel123

    jel123 Active Member

    I can,t belive a grade 8 bolt being torqued to 65 pounds would need to be replaced,jel
  5. fin_676

    fin_676 Experienced Member Staff Member Moderator Contributor

    I'm sure that the hd dealer will be right with everything well they will sell the best boots money can buy cos the hd badge is on them

    The indy may be a proper engineer rather than an hd trained money collector
    steel bolts going into aluminium shouldn't strain the bolts if that were the case then every time you removed a bolt you'd have to replace it
    However the bolt may be placed under strain by the action of the brake
    As i have a tendency to replace all fasteners with stainless steel id fit stainless as a matter of course (harsh environment in north Scotland)

  6. jmpancoast

    jmpancoast Active Member

    Absolutely replace them. Lots of occurances of them shearing off. I can provide you with references, if you would like.
  7. STEVE07

    STEVE07 Well-Known Member Staff Member Super Moderators

    I deal with fasteners all the time,and when I used to rig steel I had to know the limits of a fastener.My opinion is that you don't have to replace the grade 8 bolts you have never stressed them ! check this out:

    Mark’s Standard Handbook for Mechanical Engineers lists Grade 5 fasteners as 120 ksi fasteners. This means the tensile strength is 120,000 lbs per square inch. It also lists Grade 8’s as 150 ksi fasteners meaning the tensile strength is 150,000 lbs per square inch. Also, the ultimate shear strength of a fastener is typically about 60% of its ultimate tension strength. So given a certain diameter (cross-sectional area) and strength rating, someone can figure out how much load that fastener can carry in both tension and shear.

    Using a .250-inch diameter grade 8 fastener gives you the following shear capability:

    A = Cross-sectional area of the fastener size (since bolt bodies/shanks have circular cross-sections, use area of a circle) = Pi x r2 where R (radius) = .250/2 = .125, therefore A = Pi x (.125)2 = .0491 square inches (in2)
    Capability in shear = 91,000 lbs / in2 x .0491 in2 = 4468 lbs

    Using the same .250-inch diameter grade 5 fastener results in the following:
    Capability in shear = 75,000 lbs / in2 x .0491 in2 = 3683 lbs

    Hope this helps:D
  8. Brutal FXDX

    Brutal FXDX Active Member

    There actually is a service bulletin the factory came out with last year and includes all beltdrive models. Yes replace the bolts, red loctite, and new torque spec. I believe it is 75-80 ft. lbs.
  9. dangerdan

    dangerdan Junior Member

    Steve , I am not an engineer , but those numbers only tell us how many lbs are required to shear a bolt.

    What is the actual number of "lbs" exerted on one of those bolts during a hard acceleration or de-acceleration.

    My bike weight is about 800 lb
    I weight 260 lb
    My riding partner weight is about 140 lb

    Thats a total 1200 lb dead weight.
    Now factor in a hard acceleration in first gear.

    Again I am not an engineer, so I cant do the math. It would be interesting to know what kinds of forces are exerted on those bolts. Until someone can, I think it worthwhile to replace those bolts.

    Thanks for the math lession. That formula is now recorded in my books.
  10. porkchop

    porkchop Active Member

    I went ahead and replaced my bolts with new grade 8s but i wont use red lock tight in aluminum, i only use the blue medium. Have had the red pull the threads out on aluminum.