spoke length
#1
Senior Member
Thread Starter
Join Date: Jul 2009
Posts: 164
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
spoke length
I intend to build a pair of wheels. Never done it before but I fancy having a go. I've read several articles and for simplicity Sheldon's page is the one I'll probably follow. I've looked at the spoke calculators and feel happy to use them. But, after using these to determine the correct length it occurred to me that I'm unsure where the spoke should end at the rim. Is it flush with the inside of the rim or should it enter the rim slightly? Is there a rule for this? I feel daft asking because I've replaced plenty of spokes in the past on different wheels and none are consistent - as far as I can remember. I really don't want to make a mistake. Or does everyone use a calculator and just go on trust?
#2
Senior Member
Join Date: Apr 2009
Location: New Rochelle, NY
Posts: 38,952
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
Mentioned: 141 Post(s)
Tagged: 1 Thread(s)
Quoted: 5908 Post(s)
Liked 2,776 Times
in
1,548 Posts
I intend to build a pair of wheels. Never done it before but I fancy having a go. I've read several articles and for simplicity Sheldon's page is the one I'll probably follow. I've looked at the spoke calculators and feel happy to use them. But, after using these to determine the correct length it occurred to me that I'm unsure where the spoke should end at the rim. Is it flush with the inside of the rim or should it enter the rim slightly? Is there a rule for this? I feel daft asking because I've replaced plenty of spokes in the past on different wheels and none are consistent - as far as I can remember. I really don't want to make a mistake. Or does everyone use a calculator and just go on trust?
Here we get into a bit of confusion. Most calculators use a formula which has the spoke reach up the the diameter you entered as the ERD (effective rim diameter). Most rim makers allow for the height of the nipple when publishing the ERD for their rims, adding 4-5mm to the actual diameter. Others don't and you have to either add 2-3mm to the resulting calculation, or 5mm to your measured rim diameter at the spoke hole where the nipple seats.
This 5mm difference between the so called effective rim diameter, and the actual diameter is the cause of many spoke length calculation errors, and for my part, I'd rather that folks published actual specs which can be measured and verified, rather than guess at the nipples I plan on using and "correcting" for me accordingly.
__________________
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
#3
Senior Member
Join Date: Dec 2012
Location: Boulder, CO
Posts: 59
Bikes: Catrike Pocket, a few others
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
This is where ERD comes into play. Its the diameter as measured from the ends of the spokes. Ideally, this corresponds to the ends of the nipples, but due to the vagaries of fortune, it doesn't always work out just the way we want. If the spokes stick out of the nipples a bit, it isn't a problem, especially if you have a double-walled rim.
As for calculators, most of them use the same math, so most of them end up with the same length. As long as you have measured your ERD correctly, you'll be ok. You did measure your ERD, right? :-).
(As usual, FBinNY beat me to the punch, and with a better answer).
An addendum: you can make ERD measuring devices by cutting two spokes to a known length (200mm works well) and screwing them into the nipples that you are going to use. Measure the gap (or overlap) between the spokes, add (or subtract) from the sum of the spokes, and you'll have an ERD that should be accurate for your nipples.
As for calculators, most of them use the same math, so most of them end up with the same length. As long as you have measured your ERD correctly, you'll be ok. You did measure your ERD, right? :-).
(As usual, FBinNY beat me to the punch, and with a better answer).
An addendum: you can make ERD measuring devices by cutting two spokes to a known length (200mm works well) and screwing them into the nipples that you are going to use. Measure the gap (or overlap) between the spokes, add (or subtract) from the sum of the spokes, and you'll have an ERD that should be accurate for your nipples.
Last edited by 400trix; 02-08-13 at 04:53 PM.
#4
Goes to 11.
Join Date: Oct 2010
Location: Wichita, KS, USA
Posts: 2,547
Bikes: 2015 Soma Double Cross
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
This is where ERD comes into play. Its the diameter as measured from the ends of the spokes. Ideally, this corresponds to the ends of the nipples, but due to the vagaries of fortune, it doesn't always work out just the way we want. If the spokes stick out of the nipples a bit, it isn't a problem, especially if you have a double-walled rim.
As for calculators, most of them use the same math, so most of them end up with the same length. As long as you have measured your ERD correctly, you'll be ok. You did measure your ERD, right? :-).
(As usual, FBinNY beat me to the punch, and with a better answer).
An addendum: you can make ERD measuring devices by cutting two spokes to a known length (200mm works well) and screwing them into the nipples that you are going to use. Measure the gap (or overlap) between the spokes, add (or subtract) from the sum of the spokes, and you'll have an ERD that should be accurate for your nipples.
As for calculators, most of them use the same math, so most of them end up with the same length. As long as you have measured your ERD correctly, you'll be ok. You did measure your ERD, right? :-).
(As usual, FBinNY beat me to the punch, and with a better answer).
An addendum: you can make ERD measuring devices by cutting two spokes to a known length (200mm works well) and screwing them into the nipples that you are going to use. Measure the gap (or overlap) between the spokes, add (or subtract) from the sum of the spokes, and you'll have an ERD that should be accurate for your nipples.
#5
Senior Member
Join Date: Apr 2009
Location: New Rochelle, NY
Posts: 38,952
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
Mentioned: 141 Post(s)
Tagged: 1 Thread(s)
Quoted: 5908 Post(s)
Liked 2,776 Times
in
1,548 Posts
Ther are a number of small variables involved anyway. For example we use the centers of the spoke holes in the calculations, but spokes are measured to the inside of the elbow, so there's 1mm. Also the spokes don't assume a straight line form hub to rim, taking a slightly longer route because of the interlace. The spoke does elongate slightly under tension. In the end all these small variables are factored into the different formulas one way or another, or maybe not at all, which may account for why different calculators may come up with slightly different answers for identical inputs.
In any case, the best practice is to pick a calculator, use a consistent way of measuring everything, and generate a spoke length. Build the wheels, and make a note of how much the spoke ends up off target (just sub flush of the nipple head) and retain that as a correction factor for all future calculations. After a few builds the results will be so predictable that you can calculate lengths and buy spokes with absolute assurance. (provide you're consistent in your methods)
__________________
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
#6
Senior Member
Thread Starter
Join Date: Jul 2009
Posts: 164
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
I suppose what I was really concerned about was if the spoke was a tad too long the nipple could run out of thread when tightening. Is the thread length standard with all manufacturers (I sense a hollow laugh)?
#7
Senior Member
Join Date: Apr 2009
Location: New Rochelle, NY
Posts: 38,952
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
Mentioned: 141 Post(s)
Tagged: 1 Thread(s)
Quoted: 5908 Post(s)
Liked 2,776 Times
in
1,548 Posts
The only standard is that there is no standard. I carefully select nipples with threads short enough that I can thread spokes up to 2-3mm beyond the top of the head. When I couldn't find these, there were times I'd use a 2mm drill to deepen the skirt (hub end) a bit to get that margin of error.
__________________
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
#8
Senior Member
A perfect build would have the spoke end flush with the edge of the nipple with the right tension and and runout. Below that is fine for government work.
#9
Senior Member
Join Date: Dec 2007
Location: San Jose, California
Posts: 3,504
Bikes: 2001 Tommasini Sintesi w/ Campagnolo Daytona 10 Speed
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 145 Post(s)
Likes: 0
Liked 35 Times
in
30 Posts
__________________
5000+ wheels built since 1984...
Disclaimer:
1. I do not claim to be an expert in bicycle mechanics despite my experience.
2. I like anyone will comment in other areas.
3. I do not own the preexisting concepts of DISH and ERD.
4. I will provide information as I always have to others that I believe will help them protect themselves from unscrupulous mechanics.
5. My all time favorite book is:
Kahane, Howard. Logic and Contemporary Rhetoric: The Use of Reason in Everyday Life
5000+ wheels built since 1984...
Disclaimer:
1. I do not claim to be an expert in bicycle mechanics despite my experience.
2. I like anyone will comment in other areas.
3. I do not own the preexisting concepts of DISH and ERD.
4. I will provide information as I always have to others that I believe will help them protect themselves from unscrupulous mechanics.
5. My all time favorite book is:
Kahane, Howard. Logic and Contemporary Rhetoric: The Use of Reason in Everyday Life
#10
Senior Member
Thread Starter
Join Date: Jul 2009
Posts: 164
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
Thanks all for the replies. My hubs arrived today so I'll play around with the calculators until I pick the optimum length - I'll tape my new rim to my old wheel to see if the calculations look correct (!). I'm getting quite excited, but then I'm a bit sad .....