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PostPosted: Tue Aug 06, 2013 1:18 pm 
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Joined: Mon Apr 11, 2011 3:16 pm
Posts: 166
Hi guys!

I am about to dive in and build up the Tune Mag 170 that just arrived.

I am building into a 38mm Chinese carbon blank that I have previously been riding. All good there.

I have measured the ERD and get an average of 568mm. I measured every single place around the rim (24 hole rim, so 12 diametres measured. Took a while, but I wanted it to be perfect). Some places were 569mm and one place was 567.8mm so pretty good there.

Now, I have input all the figures into WheelProUK spoke calcultor and get the following for spokes...

275.2m on the left
270.3mm on the right.

Well, first of all, this will be a 2 cross wheel, on both DS and NDS. Also, I will be using Sapim CX Ray spokes, so given that Sapim only supply spokes in whole number lengths, would you think I could go for...

275mm on left
270mm on right

Which would be rounding down to the nearest whole number, or do I need to round UP and go for;

276mm left
271mm right

?

Any help would be greatly appreciated, as I will order the spokes the minute I am sure.

I seem to remember something in this thread with someone suggesting knocking 1mm off spoke lengths, or something, but this thread is so long now it is hard to find info!

Well, cheers for your help in advance!


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PostPosted: Tue Aug 06, 2013 1:34 pm 
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Joined: Tue Jan 05, 2010 12:29 am
Posts: 142
I am far from an expert, but .2mm is about 1/2 the thickness of this letter I. There is no way that could make a difference. If it had been a .8 or .9 mm value rounding up would make sense.


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Posted: Tue Aug 06, 2013 1:34 pm 


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PostPosted: Tue Aug 06, 2013 1:58 pm 
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Joined: Mon Apr 11, 2011 3:16 pm
Posts: 166
Wow, speedy reply, thanks!

OK, so in your opinion, you are thinking I go with the rounded down lengths of; 275mm / 270mm ?

I was thinking the same, so thanks for the input.

I would be interested in hearing other opinions on this too; buying CX Ray spokes is expensive, and I want to get the correct lengths!!


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PostPosted: Tue Aug 06, 2013 9:42 pm 
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Joined: Sun Jun 17, 2012 3:15 pm
Posts: 183
Everyone's got a different opinion on rounding up or down, to be honest either length you've given will work just as well as the other. Measure how long the length of the threaded portion of a spoke is, and how long a nipple is, now add them together. This is the range of variation available when you tighten the spokes, and you're worrying too much about whether the spoke will be .3 of a mm one way or .7 of a mm the other side of "perfect".

So basically order the ones they have in stock. ;)


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PostPosted: Tue Aug 06, 2013 10:39 pm 
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Joined: Mon Apr 11, 2011 3:16 pm
Posts: 166
Thanks again!

OK, given this sound advice, I will go for the rounded down numbers. Nice and even in my mind!

Appreciated.

One more thing; looking at the numbers I have given, and considering I am using a Tune Mag 170 hub... do those lengths look correct? I would have thought the NDS would have been greater than 5mm longer than the NDS...


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PostPosted: Wed Aug 07, 2013 5:09 am 
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Joined: Mon Apr 11, 2011 3:16 pm
Posts: 166
Oh yeah, in my search around for online spoke length calculators, one of the recommendations was the UBI one, here;

http://www.bikeschool.com/tools/spoke-length-calculator

Now, I may be being stupid here, but I can only see one input for flange diameter... My Tune Mag 170 has different diameter flanges on L and R, so how does that work (please correct me, whilst tutting, if I have made a schoolboy error!)


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PostPosted: Wed Aug 07, 2013 9:22 am 
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Joined: Sun Jun 17, 2012 3:15 pm
Posts: 183
Depends on the flange diameters, but generally if they're equal then they aren't that much different in length regardless of dish. For example, if the flanges are the same diameter there should only be about 2mm of difference between the NDS and DS so don't expect any whopping difference between the two.

Try the edd calculator too, you can pull the Mig hub out of the list then put your own ERD in.


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PostPosted: Wed Aug 07, 2013 11:04 am 
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Joined: Mon Apr 11, 2011 3:16 pm
Posts: 166
Thanks for the reply, and the hint about EDD Spoke Calculator.

I just used it and got the following;

DS = 270.6mm

NDS = 275.5mm

Given that, and given the other numbers I got from WheelProUK, would it be a good idea to round this up to 271mm and 276mm for the spokes?


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PostPosted: Wed Aug 07, 2013 11:57 am 
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Joined: Sun Jun 17, 2012 3:15 pm
Posts: 183
CX Ray are quite thin as far as spokes go, so it depends on wether you anticipate them stretching at all. If you believe they will then round down, if you don't then round up.

Either way you'll be fine.

A lot of spokes only come in 2mm increments so its not unusual to knock off 0.5mm or add on 1.5mm in those situations, and many sound wheels have been built in the annals of time both ways.


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PostPosted: Thu Aug 08, 2013 2:58 am 
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Joined: Tue Dec 04, 2012 3:57 am
Posts: 88
DT's online calculator can compensate for the stretch of thin spokes, and the result is quite accurate. If the spoke's stretch is added to the result, I usually round down if the decimal number is less than 0.2, and round up otherwise.


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PostPosted: Thu Aug 08, 2013 5:47 am 
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Joined: Tue May 20, 2008 5:34 am
Posts: 50
I'm looking at building up a lightweight alloy clincher wheelset around a Powertap G3 hub. I'm about 150 lbs. Many of my wheels are 20/24 spokes. I was thinking of Sapim CX-Ray spokes with a BHS front hub. Mostly looking for rim recommendations or other ideas. These would be primarily for mountain climbing and descents (aka, why I want alloy brakes surfaces). Thanks!

-Pete


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PostPosted: Fri Aug 09, 2013 12:06 am 
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Joined: Tue Nov 11, 2003 9:47 pm
Posts: 1698
Location: Santa Cruz, California, USA
XR270 if you are ok with a narrow rim. The KinLin wide rims on BHS are nice but I think there are lighter options. I llke the UL66 hubs. The wider hubs are ok too but the slightly flexier wheel with the narrow flange hub doesn't bother me. I laced the last one 1x heads in and I think I like that. I've had spokes break on those hubs when laced radial heads out. My theory is that the spoke hole countersink on the outside leaves the elbow unsupported.

I weigh just 5lbs less and I am ok with 20h fronts but build 28h rears for training.


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PostPosted: Fri Aug 09, 2013 7:59 am 
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Joined: Tue Aug 14, 2012 7:36 am
Posts: 53
Since the XR-270 rims weighs the same as the Pacenti SL23 and only at litte less than the H Plus Archetype and HED Belgium C2. I would take any of those rims before the Kinlin rims as they are stronger and wider.


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PostPosted: Fri Aug 09, 2013 11:33 pm 
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Joined: Tue Jan 22, 2013 6:23 am
Posts: 352
I'm thinking about building my first set of wheels. I've been truing wheels on my bikes (zip tie method) for a while. I ride road, mtb, and race downhill bikes. Is the Park TS-2.2 still the industry standard for truing stands? I'm tired of the zip ties, and looking forward to learning how to build good wheels.


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Posted: Fri Aug 09, 2013 11:33 pm 


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PostPosted: Sat Aug 10, 2013 12:27 am 
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Joined: Tue Nov 11, 2003 9:47 pm
Posts: 1698
Location: Santa Cruz, California, USA
It's pretty nice. It is the shop standard. It'll last you the rest of your life and you can will it to your kids, assuming there are still bicycles with wheels then. However it does not keep center very well. It seems that when you adjust the arms from front to rear hub width a few times it loses center. So you also need a wheel dish tool or the Park stand centering gauge (or you can make one).

Less expensive truing stands will work fine too.


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