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Old 10-04-07, 09:37 AM   #1
smurf hunter
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Round up or down for spoke length?

I need to re-lace a rear wheel to replace a blown hub. This is a disc brake hub (Shimano Deore LX M858), so the dishing will differ a bit from your normal road wheel I figure. This is my daily commuter, so it probably will take a licking over time.

Most everything I've read regarding conventional rear wheels has the non-drive side 2mm longer than the drive side, but the calculations for this hub have barely a 1mm difference.

My spoke calculations give 282.7 for the right and 284.1 for the left. I got my rim's ERD and hub specs straight for the respective MFG websites and plugged it all into http://www.bikeschool.com/spokes/index.cgi.

Following the math it seems sensible to use 283mm for the drive side, but the trouble is I cannot find DT comp DB spokes in 283mm length pre-made. I'm hoping to buy from cambriabike.com at $0.59 each.

My options:

1) go to an LBS with a Phil wood machine and get 16x 283mm spokes custom cut/threaded for $1.00 each
2) round down and get 16x 282mm spokes for the drive side
3) round up 1.3mm and just get all 284mm spokes for my 32 hole wheel

I plan to use veloplugs, so I'm not terrified of long spokes approaching the end of the nipple.

Any advice is appreciated.
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Old 10-04-07, 09:58 AM   #2
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I've only tried once to go longer like you're suggesting and all my drive side spokes were bottomed out on the threads when dished correctly, so I wouldn't recommend that route. I'd use 282s and 284s if you can get them.
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Old 10-04-07, 11:12 AM   #3
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Get 282's drive side and 284's for non drive side.
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Old 10-04-07, 11:35 AM   #4
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Lickbike has the 282 and 284.......sold in 20 spoke bundles including nipples. I purchase all my spokes from Lickbike....excellent service.
http://www.lickbike.com/
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Old 10-04-07, 11:42 AM   #5
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Always round down so that you don't bottom out the threads.
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Old 10-04-07, 10:43 PM   #6
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Always round down so that you don't bottom out the threads.
But not with alloy nipples! Spoke length must be perfect for those. All the way through the nipple-no less.
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Old 10-05-07, 09:16 AM   #7
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But not with alloy nipples! Spoke length must be perfect for those. All the way through the nipple-no less.
Simply not true. All of my wheels are built with DT alloy nipples. I always round down at least 1 mm on the rear drive side. No problems with alloy nipples as long as the spoke wrench fits properly, you need to use the correct size wrench.

And being 1 mm shorter than the calculated length does not mean that the threads are not completely engaged, they probably will be.

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Old 10-05-07, 09:54 AM   #8
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Simply not true. All of my wheels are built with DT alloy nipples. I always round down at least 1 mm on the rear drive side. No problems with alloy nipples as long as the spoke wrench fits properly, you need to use the correct size wrench.

And being 1 mm shorter than the calculated length does not mean that the threads are not completely engaged, they probably will be.

Al
Simply uninformed!

I've been through the DT school and my certificate is hanging on the wall. They are pretty clear on this: if the spoke does not go to the end of the nipple, the nipple is prone to failure at the point at which it flares out. My personal experience of 25 years as a wheelbuilder and wheel repair person bears this out. When a nipple fails and it isn't due to impact, you can nearly always assume the spoke didn't go to the end of the nipple.

Brass nipples do not have this issue, and are very well suited to wheels not built for racing, or when the spoke length must be compromised due to availability.
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Old 10-05-07, 10:59 AM   #9
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Simply uninformed!

I've been through the DT school and my certificate is hanging on the wall.
So why is it that the DT spoke length calculator always rounds down, alloy nipples included? With Revolution spokes it rounds down an extra mm.
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Old 10-05-07, 11:04 AM   #10
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Simply uninformed!

I've been through the DT school and my certificate is hanging on the wall. They are pretty clear on this: if the spoke does not go to the end of the nipple, the nipple is prone to failure at the point at which it flares out. My personal experience of 25 years as a wheelbuilder and wheel repair person bears this out. When a nipple fails and it isn't due to impact, you can nearly always assume the spoke didn't go to the end of the nipple.

Brass nipples do not have this issue, and are very well suited to wheels not built for racing, or when the spoke length must be compromised due to availability.
Bikewise is right. Alloy nipples need full engagement of the threads or they will fail prematurely. You can certainly build a wheel without worrying about it, but the same wheel built with nips fully engaged will last longer, all other things being equal.

I do not have the DT certificate. But I have been building wheels for 18 years or so. And much of what I have learned comes from hands on experience and picking the brains of wheelbuilders all over.
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Old 10-05-07, 11:23 AM   #11
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The DT Comp spokes from Lickbike includes plated brass nipples at $13.00 per 20......alloy nipples are available though. I always round down and the spokes ends usually within the nipple screwdriver slot or (rarely) flush with the nipple end. My axpertise is very limited compared to BikeWise and others, but I have built 27 wheelsets with great satisfaction/performance.
To the OP.......Licbike has your specified spokes in stock.......
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Old 10-05-07, 11:29 AM   #12
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So why is it that the DT spoke length calculator always rounds down, alloy nipples included? With Revolution spokes it rounds down an extra mm.
Since I do not use their calculator, I am at a loss to explain that. However, it is wise to not round up with Revolutions. They stretch quite a bit compared to Competitions.

It is also prudent to note the size of the holes in the hub. That can add apparent spoke length on cheaper hubs with large holes (@2.6mm) when compared to higher quality hubs (@2.3mm).
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Old 10-05-07, 12:27 PM   #13
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Off topic for a moment, but cambriabike.com (CBO) does not include any nipples with their spokes. That's the reason DT spokes are so cheap there.
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Old 10-05-07, 12:58 PM   #14
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Off topic for a moment, but cambriabike.com (CBO) does not include any nipples with their spokes. That's the reason DT spokes are so cheap there.
CBO price per nipple is $0.10....which added to spoke price = $0.69 per. The Lickbike price works out to $0.65 per spoke....but you have to buy 20 of each size.....plenty of spares
I only suggetsed Lickbike because you requested a source......they have them in stock and they are great to deal with.
BTW, were you able to acquire 6 bolt hubs??? or did you get the Centerlock and use 6 bolt adapter???
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Old 10-06-07, 02:39 PM   #15
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Ok, the point I'd make is that the DT calculator rounds down the same for alloy or brass nipples. DT does not differentiate spoke length for brass or alloy nipples. Which is why I took issue with your previous statement, and I could have done a better job of explaining that. Of course it is advisable to engage all of the threads in the nipple and I've never had a problem doing that after rounding down. And I suspect that DT alloy nipples have as much tensile strength as brass.
As I'm sure you know, the need for rounding down is to avoid running out of threads when reaching the target tension. This is especially important on rear driveside spokes because of their higher tension.

Peace,

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Old 10-06-07, 09:30 PM   #16
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CBO price per nipple is $0.10....which added to spoke price = $0.69 per. The Lickbike price works out to $0.65 per spoke....but you have to buy 20 of each size.....plenty of spares
I only suggetsed Lickbike because you requested a source......they have them in stock and they are great to deal with.
BTW, were you able to acquire 6 bolt hubs??? or did you get the Centerlock and use 6 bolt adapter???
I'll try out lickbike next time around. 20 is an inconvenient quantity, if you figure most common wheels have 32 spokes, but that does give me 4 spares per side when building a rear wheel.

I actually scored a Deore LX centerlock hub off nashbar for 19.99. I also had to spend $14.99 for a centerlock rotor. In total that's still below the retail price for any shimano disc freehub I could find anyplace else.

Even though this is for my "rain" bike, I'm excited to build up a new wheel for it.
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