## Help please! Spoke length and extralite hub.

Discuss light weight issues concerning mountain bikes & parts.

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Nicholas68
Posts: 69
Joined: Wed Jun 19, 2013 1:30 am
So I am majorly confused at the moment, I have done spoke lengths before and gotten them right using the calculators but I am looking at the extralite J bend front hub. http://www.extralite.com/Products/Hyper%20JF.htm When I put the hub dimensions which they provide into the sheldon brown and dt swiss calculator I get same results, Left(disc) 292mm and Right 297. But extralite also has a chart where you pick the spoke size based on the effective spoke length which I measured at 604, same as my rims ERD 604. Using this chart I get Left 297mm and right 288mm. I think they read L and R opposite so the 297 I am fairly sure is on the non disc side as it has a smaller flange hence the longer spokes. But why is the disc side got 292 from the calculators and 288 from extralites chart. When I used the hub dimensions extralite list to do the calculations. Which would you order? They are both based around a 32h 3 cross lacing pattern.

So confused right now!

dwaharvey
Posts: 493
Joined: Thu Oct 26, 2006 8:54 pm
Location: USA
Take a step back. Using Table B on the Extralite spoke length site, you need the 3rd column for 32 holes, and this gives a disc-side spoke length of 292mm. That matches your calculation. Not sure where the 297 number you got came from, unless you're reading the 2nd column which is for 28 holes/spokes. Using Table A on the same page, you need the 2nd column for the JF hub (column 3 being JL=Lefty), and this gives a "right" side of 287mm. I agree "right" is a confusing term to use, but there are a few clues to clear things up:
1) Table B refers to Disc side, so Table A must therefore be non-disc
2) Table A says "Radial Lacing" in the header... no one in their right mind would radial lace a front hub on the disc side, so the side in this table must be non-disc

#2 Tells you the source of your confusion: Extralite are proposing that you radial lace the non-disc side of your front hub, whereas you calculated a length for 3x. The radial lacing has a shorter path between rim and hub so their length is shorter. Up to you if you want to follow their suggestion or stick to 3x on that side. I can't imagine it's going to make a very noticeable difference to anything except the spoke length.

Nicholas68
Posts: 69
Joined: Wed Jun 19, 2013 1:30 am
dwaharvey wrote:Take a step back. Using Table B on the Extralite spoke length site, you need the 3rd column for 32 holes, and this gives a disc-side spoke length of 292mm. That matches your calculation. Not sure where the 297 number you got came from, unless you're reading the 2nd column which is for 28 holes/spokes. Using Table A on the same page, you need the 2nd column for the JF hub (column 3 being JL=Lefty), and this gives a "right" side of 287mm. I agree "right" is a confusing term to use, but there are a few clues to clear things up:
1) Table B refers to Disc side, so Table A must therefore be non-disc
2) Table A says "Radial Lacing" in the header... no one in their right mind would radial lace a front hub on the disc side, so the side in this table must be non-disc

#2 Tells you the source of your confusion: Extralite are proposing that you radial lace the non-disc side of your front hub, whereas you calculated a length for 3x. The radial lacing has a shorter path between rim and hub so their length is shorter. Up to you if you want to follow their suggestion or stick to 3x on that side. I can't imagine it's going to make a very noticeable difference to anything except the spoke length.

Thank you. All cleared up now. I was thinking when they mentioned 3 cross in the lacing pattern it was for the whole wheel. But 3 cross on the disc and radial on the non disc side does make sense as far as the table goes. And completely missed that 28 spoke and 32 spoke. Must have had it in my mind the lefty was on right and JF was on left. I looked at the table 10+ times.

So in theory radial lacing on non disc side will save like 3g of weight in spoke length. And 3 cross will be slightly stronger? Would it be advised to go radial lacing since the max non drive tension is 60kgf, or is that just because it is radial laced and if I did 3 cross I could get away with 100kgf on both sides? I'm using a carbon rim so I'm wanting to tension the hub as high as it's rated, so 110 disc side and 70 on non disc side at the moment.

Really appreciate the help.

dwaharvey
Posts: 493
Joined: Thu Oct 26, 2006 8:54 pm
Location: USA
I think Extralite are probably intending the radial lacing to be done heads-out/elbows-in, in which case I think the bracing angle of the spokes is probably similar to a 3x where the spoke lines up with the flange center (rather than the inside) but attaches closer to the axle rather than at the periphery of the flange.

I'm not sure what the limiting factor is on the tension for the hub. The radial lacing with 32 holes on a small flange (not much material to support things) definitely limits tension on that side, but whether that's the main limiting factor for the hub and they're just transforming it over to an equivalent disc-side max-tension (assuming a symmetric rim), or if the disc-side flange really can't take more than 100-110kgf in a crossed configuration... I don't know. I do know that if I were building the wheels with carbon rims (which?) I'd want to go higher than even 110kgf... more like 120 or 130... so if I were in your position I'd call Fairwheel or someone who has experience with the hub and ask their opinion.

With a hard 110 limit on the disc-side, I'd go for the radial pattern suggested by Extralite. But if they thought the limit was just because of the radial non-disc lacing...I'd go 3x both sides and push the tension up to 120-130kgf.

xc71
Posts: 102
Joined: Fri Oct 14, 2011 4:36 am
I have a 1 1/2 years on my Extralite wheelset with no issues. 28 hole, straightpull, Radial laced non-disc side front.
Was going to post a pic, but not allowing attachments on this thread.

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