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Old 07-13-05, 11:50 AM   #1
mx_599
Lost in the Black Hills
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My basic question is: Why can't I get my rim true without ending up with tight spokes?

Now let me give you all the details so hopefully you will say it is probably okay or shed some light on this problem. Furthermore, I do understand that when dishing the wheel there will be a tighter side as well to account for the assymetry between the rim/hub.

1) all new parts

2) DT Super Comp 2.0/1.7/1.8, Brass nipples, Sun DS1-XC rims (32 hole)

3) my weight 135lbs

4) Park "home use" tensiometer (TM-1)

5) I called SUN and they recommended a tension on these rims of 70-95 Kgf depending on spoke diameter and nipple material.

6) my final approx. tension measurements: (front & back) "tighter side" = 150 Kgf, "looser side" = 100 Kgf

As you know, the way this tensiometer measures depends on spoke thickness. I am considering my spokes to be 1.7mm. It appears that the tensiometer is measuring over the section of the spoke that is 1.7mm. However, if the spoke head diameter or threaded diameter is to play a part in these tension measurements, then the tension would effectively be lowered according to my Park TM-1 TENSION METER CONVERSION TABLE. Lowered to the point of being more within spec of SUN's recommendations.

Couple more points. You would think if I just systematically loosened all the spokes that things would have stayed properly trued and dished. This is exactly where my problem would come. I tried multiple times to equally loosen things back up but would run into the same problem each time:

1) spokes on respective sides greater than +/- 20 % tension

2) dishing totally out of whack

Even though this is the first wheel set I built, I am generally pretty good with this type of thing and do not see where I might have erred. It is like the "dishing" forces and imperfections of the new rim prevented these lower tension values.

I feel like I obtained the lowest tension values possible while keeping the rim true, spokes to 20 %, and the proper dishing.


1) Do you think the tensions I achieved will damage my rims?

2) Do higher tensioned spokes make for harsher riding characteristics...or not that I'd notice?

I know this is long, but I am hoping with the details that those of you with experience can help.

thanks

Last edited by mx_599; 07-13-05 at 11:57 AM.
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