Advertise on Bikeforums.net



User Tag List

Results 1 to 12 of 12
  1. #1
    Senior Member
    Join Date
    Jul 2005
    Posts
    88
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Dramatically different spoke tension with tire on and off rim?

    I’am measuring spoke tension with a Park TM-1. With the tire and tube off the rim the average spoke tension reads around an average 22 degree deflection which is around 111 (kgf). All of the spokes fall well within the 20 percent variation. The wheel is also true both laterally, vertically as well as dished properly. When I put the wheel together and pump up the tube (100 psi) the average spoke tension changes dramatically. The average is now around a 18-19 deflection which is around 72-80 (kgf) (Most of the spokes are still tensioned proportionally the same but, one of the spokes is reading around a 15 degree deflection which is around 54 (kgf)). Is this normal?

    Rebuild of lightly used rim. New spokes and hub, Original rim. I have put around 30 miles on this wheel before noticing this.

    I have also been looking for the proper tension for a Matrix IS0 C-II rim, but since no luck so far I’am using what I think was the original tension 110- 115 (kgf). Since this rim does not have eyelets I wouldn’t think the tension should be any more than this?


    3 Cross spoke pattern
    Matrix IS0 C-II 700C 13mm internal dimension, So should fit 18-25 (Sheldon Browns Guide)
    Shimano HB 5501 Front Hub
    Spokes stainless steel 14 gage 2.0mm -1.8mm -2.0mm
    Tire WBT Camino sport Casing 23/20 700C steel bead (Rated to 100 psi)
    Tube continental Race 700

  2. #2
    You need a new bike supcom's Avatar
    Join Date
    Aug 2002
    Posts
    5,434
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Think about what it means to pump up a tire to 100 psi. The pressure is squeezing your rim pretty tightly. what would you expect to happen?

  3. #3
    JRA...
    Join Date
    Oct 2003
    Location
    philly
    My Bikes
    trek 520 & 736, DeRosa Professional, Fuji Professional, Raleigh International 3-speed, Saronni (any info people?), Humber 3-speed, Raleigh Sports, Carlton Grand Prix coming soon!
    Posts
    839
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    can't speak for spoke tension on a quality rim, but i can say many a time i've had to readjust brakes on a dept. store bike after inflating the tire, because the rim will grow wider or even out of true...

  4. #4
    Senior Member
    Join Date
    Jul 2005
    Posts
    88
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    The fact that inflating the tube will have some affect on rim tension makes sense to me. What surprised and a little concerned me is the amount. So I guess the question I should have asked was did I under tension the wheel to begin with allowing the inflated tube to radically affect the final tension.

    I have built wheels before, and have just used feel to tension the wheel. Now that I have Parks TM-1 tension meter I’am checking everything, and becoming aware of just how off I was in the past.

  5. #5
    Senior Member
    Join Date
    Jul 2004
    Location
    Cental New Jersey
    My Bikes
    Klein Quantum Pro
    Posts
    469
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Adohrn
    The fact that inflating the tube will have some affect on rim tension makes sense to me. What surprised and a little concerned me is the amount. So I guess the question I should have asked was did I under tension the wheel to begin with allowing the inflated tube to radically affect the final tension.

    I have built wheels before, and have just used feel to tension the wheel. Now that I have Parks TM-1 tension meter I’am checking everything, and becoming aware of just how off I was in the past.
    111 Kgf actually seems a little high to me. I target 100-110 for most rims on front wheels. That said, I'm not familiar with the rim you are using. You should get a specification for spoke tension from the rim manufacturer.
    Check out my club's site:
    New Jersey Road Club

  6. #6
    Junior Member
    Join Date
    May 2006
    Posts
    19
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    You said you rode the bike for about 30 miles before noticing the change in tension. My guess is that the change is a result of the spoke heads, nipples and/or ferrules "seating" themselves, plus the bend where the spokes cross straightening out. Plus maybe some spoke windup being released. I would also guess that even with a used rim, the spoke tensions should be more even than you've described.

  7. #7
    Senior Member
    Join Date
    Feb 2005
    Location
    Oklahoma
    My Bikes
    Trek 5500, Colnago C-50
    Posts
    9,155
    Mentioned
    2 Post(s)
    Tagged
    0 Thread(s)
    That's a much bigger change than what I've measured with my Park TM2.
    My wheels are MAVIC OP's and DT RR 1.1 rims, DT Revolution spokes. As best I can remember I've measured a deflection decrease from 23 to about 22 with an air pressure of about 115 psi.
    Are your posted numbers from a front wheel or rear driveside. The 110 kgf seems a bit high for a front wheel but that would not explain the big reduction after inflation.
    I've found that to get an accurate measurement with the Park tensiometer it's necessary to release the gauge onto the spoke slowly. A quick move causes a rebound and an incorrect result.

    Al

  8. #8
    THIS SPACE FOR RENT
    Join Date
    Jan 2006
    Posts
    2,849
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Al1943
    I've found that to get an accurate measurement with the Park tensiometer it's necessary to release the gauge onto the spoke slowly. A quick move causes a rebound and an incorrect result.

    Al
    ^^^^^^ Hot tip of the week. I hadn't figured that out myself, but it certainly explains some past weirdness.
    "I don't buy new frames, it just encourages them."

    -T.G.

  9. #9
    Senior Member
    Join Date
    Jul 2005
    Posts
    88
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    The measurements are from the front wheel. I made sure to slowly release the meter, and to not measure the tension from the butt of the spoke.

    I did a lot of pre stressing before using the wheel. So while the wheel did need a quick tune up after the first 30 miles the tension and trueness did not appreciably change. I have since checked the trueness of the assembled wheel (at 100 psi). It did not appear to affect the lateral trueness by more than a millimeter at most. The vertical true is harder to judge, but appears fine as well.

    I also checked individual spoke tensions after inflating and deflating the tube. At least on this rim it really does appear to affect the final tension that dramatically.

    You got me on the average spoke tension. The 110-115 kgf was taken from the rear drive side. I was just tensioning the front wheel to that measurement. I should have know better, but was not thinking. I’am probably going to leave it at 111 (non assembled) just because its running at 75-80 at 100 psi.

    I have also spent several hours online looking for the proper tension of this rim, but with no luck so far.

    Rode another 60 miles on Sunday with no problems. I think for now I will just continue to use the wheel, but not race down any hills until I’am sure its not going to do something like taco.

  10. #10
    Senior Member
    Join Date
    Feb 2005
    Location
    Oklahoma
    My Bikes
    Trek 5500, Colnago C-50
    Posts
    9,155
    Mentioned
    2 Post(s)
    Tagged
    0 Thread(s)
    Yeah, I'd just watch it closely for awhile, check for cracks or stretch marks in the rim near the spoke holes. If the tension remains fairly consistent and the rim's not cracking you're not going to taco the wheel.
    When you calculate the kgf are you using the 1.8mm size? I'm not sure how accurate the chart is. According to Park I'm running 157 kgf on my driveside rear with no problems 2.0 - 1.5 - 2.0 spokes.

    Al

  11. #11
    Senior Member
    Join Date
    Jul 2005
    Posts
    88
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I used the 1.8 mm spoke diameter on the conversion table.

    I actually had to ask the answer to the question not to long ago on this forum. I had reached the 22 degree deflection, and was originally using the 2.0 mm conversion on the table. So according to the chart I was only at 85 kgf. At that point in time I was smart enough to stop, and ask for help.

    Thanks again everyone.

    Double butted 14 gage (2.0mm -1.8mm- 2.0mm) round stainless steel, Champion DT

  12. #12
    Curmudgeon Wil Davis's Avatar
    Join Date
    Aug 2005
    Location
    Nausea, New Hamster
    My Bikes
    (see http://wildavis.smugmug.com/Bikes) Bianchi Veloce (2005), Nishiki Cascade (1992), Schwinn Super Sport (1983)
    Posts
    1,572
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    It sounds intriguing - so, I took a front wheel; the rim is an ARAYA 26x1.50HE RX-7, laced to a Shimano Exage HB RM-50 hub, with DT 2.0 straight spokes (32 x 3); measured the spoke tension (average of 87 Kgf); fitted an IRC Metro Duro 26"x2" tyre, inflated to 85 psi. measured tension again - no noticable change…

    - Wil
    "………………………" - Marcel Marceau

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •