Go Back  Bike Forums > Bike Forums > Bicycle Mechanics
Reload this Page >

spoke lengths: round up or down

Notices
Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

spoke lengths: round up or down

Old 05-28-22, 10:14 AM
  #1  
joedab
Senior Member
Thread Starter
 
Join Date: Oct 2007
Posts: 87
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 41 Post(s)
Likes: 0
Liked 1 Time in 1 Post
spoke lengths: round up or down

My understanding is that spoke lengths are generally forgiving rounded to the nearest even or odd number, plus/minus almost 2 mm and they will still fit without any problems. My question is whether it is optimal rounding these numbers up or down. A shorter spoke may not start showing threads beyond the nipple but could be shy of engaging threads in the head. A longer spoke may not bottom out its threads but still engage ample threads in the head of the nipple, while there is usually ample space within the walls of a given rim to allow for some spoke protrusion. Therefore, would people generally agree rounding up 1.5 mm is better than down 0.5 mm? Attached are a couple wheels I am working on in case there are any opinions.




Last edited by joedab; 05-28-22 at 10:17 AM.
joedab is offline  
Old 05-28-22, 10:24 AM
  #2  
79pmooney
A Roadie Forever
 
79pmooney's Avatar
 
Join Date: Oct 2014
Location: Portland, OR
Posts: 10,600

Bikes: (2) ti TiCycles, 2007 w/ triple and 2011 fixed, 1979 Peter Mooney, ~1983 Trek 420 now fixed and ~1973 Raleigh Carlton Competition gravel grinder

Mentioned: 115 Post(s)
Tagged: 0 Thread(s)
Quoted: 3492 Post(s)
Liked 2,272 Times in 1,477 Posts
I'll go .5mm short, but not 1mm short IF I'm taking the erd to the top of the nipple heads. This keeps the top of the spoke well into the nipple head. Shorter is a sure fire way to promote the nipples popping their heads (for me, usually before 5000 miles). I've found I can usually poke 1.5mm above the nipple head without running out of thread. (I may hit the end of the threads, but I've found the softer nipple will simply distort around the spoke for a thread or so and not be an issue.)

Edit: This is a good reason to measure your rims for the erd and not take a published (or someone else's) value. Besides, published values may well have been printed before that rim went into production or a change make on the line.
79pmooney is offline  
Old 05-28-22, 10:36 AM
  #3  
ThermionicScott 
working on my sandal tan
 
ThermionicScott's Avatar
 
Join Date: Aug 2011
Location: CID
Posts: 22,050

Bikes: 1991 Bianchi Eros, 1964 Armstrong, 1988 Diamondback Ascent, 1988 Bianchi Premio, 1987 Bianchi Sport SX, 1980s Raleigh mixte (hers), All-City Space Horse (hers)

Mentioned: 95 Post(s)
Tagged: 0 Thread(s)
Quoted: 3628 Post(s)
Liked 2,061 Times in 1,309 Posts
For me, it depends on how much I expect the spoke to stretch. I'm comfortable rounding rear drive-side spokes down a bit, since they will stretch the most, especially if using thin butted spokes. The others I might round up, unless that puts me at 2mm too long or more.
__________________
Originally Posted by chandltp View Post
There's no such thing as too far.. just lack of time
Originally Posted by noglider
People in this forum are not typical.
RUSA #7498
ThermionicScott is offline  
Old 05-28-22, 10:38 AM
  #4  
Aardwolf
Old Git
 
Join Date: Aug 2021
Location: London UK
Posts: 234

Bikes: 1982 Holdsworth Avanti

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 67 Post(s)
Liked 128 Times in 74 Posts
I found a spoke calculator that allows for spoke stretch:
https://www.wheelpro.co.uk/spokecalc/

If you look at the 'log' tab it looks like

Spoke lengths required

  • Left : 298.2157 (will stretch 0.1969 to make calculated length).
  • Right : 295.8789 (will stretch 0.4400 to make calculated length).
I couldn't find what kgf this is based on but I'm guessing somewhere around 100 to 120.

The stretched spoke lengths agree with the Spocalc results.
I've also found a (UK) spoke supplier that cuts to any length in 1mm increments.
Aardwolf is offline  
Likes For Aardwolf:
Old 05-28-22, 01:45 PM
  #5  
GamblerGORD53
Senior Member
 
Join Date: Apr 2010
Location: Elevation 666m Edmonton Canada
Posts: 2,003

Bikes: 2013 Custom SA5w / Rohloff Tourster

Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 930 Post(s)
Liked 159 Times in 129 Posts
Always go longer. There's no downside. The head will be far stronger. They seem to calculate short all the time anyway.
I have 2 specific flat screwdrivers, one with a notch and the other with a tooth sticking up for starting the nipple.
GamblerGORD53 is offline  
Old 05-28-22, 02:00 PM
  #6  
Troul 
:D
 
Troul's Avatar
 
Join Date: Oct 2013
Location: Mich
Posts: 5,537

Bikes: RSO E-tire dropper fixie brifter

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 6 Post(s)
Liked 1,844 Times in 1,235 Posts
I'd go with longer. Worse case, you end up using nip washers to address shortages regarding thread length.
__________________
-Oh Hey!
Troul is offline  
Old 05-28-22, 09:17 PM
  #7  
joedab
Senior Member
Thread Starter
 
Join Date: Oct 2007
Posts: 87
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 41 Post(s)
Likes: 0
Liked 1 Time in 1 Post
given the tentative consensus on longer spokes, in this particular case:



either 1. all @ 290 2. round n-ds up 1.4 mm for half at 292 3. worth spending on 191?

splitting the distance between both, leads to the fourth option of 288 and 290, even though shorter.

regardless, stretch would seem to be negligible until getting into spokes double-butted above 15 gauge.

could all be trivial if a given spoke has 2 mm between either bottoming out or exposed threads ..

Last edited by joedab; 05-28-22 at 11:05 PM.
joedab is offline  
Old 05-28-22, 10:53 PM
  #8  
GamblerGORD53
Senior Member
 
Join Date: Apr 2010
Location: Elevation 666m Edmonton Canada
Posts: 2,003

Bikes: 2013 Custom SA5w / Rohloff Tourster

Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 930 Post(s)
Liked 159 Times in 129 Posts
Get 290 and 292.
GamblerGORD53 is offline  
Old 05-28-22, 11:53 PM
  #9  
cpach
Senior Member
 
Join Date: Oct 2009
Location: Mt Shasta, CA, USA
Posts: 2,052

Bikes: Too many. Cannondale SuperSix, Trek Remedy 8, Trek Crossrip+ get the most ride time.

Mentioned: 26 Post(s)
Tagged: 0 Thread(s)
Quoted: 491 Post(s)
Liked 264 Times in 203 Posts
Longer always if available--you have a ton of room past ideal before anything bad happens. Even if you start having to force the last half turn or so to get ideal tension its not the end of the world. Here's a good explanation of why: https://wheelfanatyk.com/blogs/blog/...ed27ffcf&_ss=r .

With your specific situation I'd probably build with 290 and 292 if I had them (or were ordering), would feel OK building with 290s all around otherwise.
cpach is offline  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.