spoke size - Mtb disc Powertap and ZTR Alpine rim ?

[Konaman]

I have a Cycleops powertap Mtb disc SL+ hub and Ztr Alpine 26"32h rims ERD 536 559x20

 

Non-drive size Flange 74mm

Drive size Flange 70mm

Non-drive Center to flange - 33.9mm

drive Center to flange - 15.9mm

 

 

I was told by somebody this is the sizes but would like to confirm it

 

Non-drive Side Drive Side

256mm 254mm

 

 

please assist

[kosmonooit]

Here's an on-line calculator

[Johan Bornman]

You don't say how many spoke crosses. Lets assume 32.

 

Further, lets assume that the stated rim ERD for that ZTR rim is correct. Stan's has a curious way of measuring ERDs and they're always 2mm out. Lets hope the Alpine is an exception.

 

Further, the Powertap hus is pretty symmetrical, so I'm surprised by the difference in left and right you give. My calculation gives me 256.6 and 256.2mm for left and right. These are absolute measurments, therefore you still have to round down. If your spokes are double butted 2-1.8-2mm, then use 256 and 255mm or of you want to reduce your size variants, 255mm on both sides.

 

If you plan on using Revolution or Laser spokes, use 255 and not 256 at all.

[Konaman]

Hi J

thx for info; Its 32h; 3 x laced

I got rim size from actual rim where its printed. ERD 536 and 559x20 erd 536; Seems you are correct with this differences. The Stans website says ERD 537 for this rim - http://www.notubes.com/literature/2011-StansNoTubes-Catalog-Small.pdf

 

i would like to use Revolution. Its for my son thats +-60kg. Should be strong enough

The flanges are different sizes. I just checked. The flange sizes i got from a pamphlet that came with hub

So i should go for 255 on both sides.

regards

Konaman

 

 

 

You don't say how many spoke crosses. Lets assume 32.

 

Further, lets assume that the stated rim ERD for that ZTR rim is correct. Stan's has a curious way of measuring ERDs and they're always 2mm out. Lets hope the Alpine is an exception.

 

Further, the Powertap hus is pretty symmetrical, so I'm surprised by the difference in left and right you give. My calculation gives me 256.6 and 256.2mm for left and right. These are absolute measurments, therefore you still have to round down. If your spokes are double butted 2-1.8-2mm, then use 256 and 255mm or of you want to reduce your size variants, 255mm on both sides.

 

If you plan on using Revolution or Laser spokes, use 255 and not 256 at all.

[Johan Bornman]

Dont' let the differnt flange sizes confuse you. It is a method used by hub designers to compensate for hub offset's effect on spoke length. In theory, you can fiddle with the flange sizes on a dished wheel so that you have the same spoke length both sides.

 

That particular hub has 74 and 70mm flanges to compensate for the 29.8 and 19.9mm flange distance to hub centre.

 

If you want some 255mm Revo's or Lasers I can help. I cut and thread from longer lengths, so I can even give you the exact size, if you want to be a bit pedandic about the lengths.

 

Edit: If you have the rim on hand, I suggest you measure first and then recalculate the spoke lengths.

Edited March 28, 2011 by Johan Bornman