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Mavic EX823 ERD = 534mm

- seb

- seb

Turbo Monkey
Apr 10, 2002
2,924
1
UK
Right, controversial topic, a million answers!

What is the ERD of an EX823 rim? DT swiss used to say 538mm and everyone said they were wrong because their spokes were coming out to be too short.

I believe that this shortness was because DT's calculator shortens the spokes when you select longer nipples WHICH I BELIEVE TO BE A MISTAKE. I've read numerous threads (no pun intended) on the subject and compared my own 12mm and 16mm nipples, and my conclusion is that spoke length is irrespective of nipple length. Most nipples have the same amount of threading at the far end, and all that really changes is elongated flats for your wrench. Some nipples seem to have 1mm of extra threads maybe, but certainly not 4mm.

Oddly DT's calc persists in shortening spokes for longer nipples, and you'd think that they'd know.... nevertheless, I'm going to ignore them, and think that my fellow monkeys would be well advised to do the same.

DT have since lessened the ERD to 532mm. At first I thought this was because the newer EX823s have a deeper cross-section. They don't, it's the same (by my measurements).

Sicklines (our own jvnixon) claims the ERD of the EX823 is 528mm.
(http://www.sicklines.com/2008/02/04/2008-mavic-ex-823-and-mavic-ex-721/)

I fear he got this from measuring them himself, because if you measure the ID from one side to the other, that's close to what you get. Actually 526mm by my eyes. However, that's not how you measure an ERD. ERD is from the top of one nipple to the top of the opposite one. My nipples sit 4mm inboard of the rim, so ERD is actually 526 + (2 x 4) = 534mm.

FWIW the www.wheelpro.co.uk spoke calculator (the one Hope have on their site) agrees with me.

I'm about to order my spokes, and unless someone on here can convince me that some of the above is wrong, I'll be using 534 as my ERD and ignoring the what DT calc says about 16mm nipples. I'll be using several different spoke calcs cos I don't trust DT any more.
 
jvnixon

jvnixon

Turbo Monkey
May 14, 2006
2,325
0
SickLines.com
Those numbers are what Mavic told me when i called (528 for the 823) and i've built with that number and its worked out fine for me.

I have measured mine (top of the nipple) and its pretty close to that, measure your rim for yourself if you'd like.
 
Discostu

Discostu

Monkey
Nov 15, 2003
524
0
Hey I've always used 534.5 on the old style ex823, D3.1 and xm819 and 530.5 on the new style ex823 (these numbers come from spocalc). This has worked great for all my builds. I have both old and new ex823s and I'll double check, but I could swear the ID on the newer rims is smaller than the old ones.

If you go through mavic's tech documents on these rims you'll find that they list "Spoke support diameter" (which I assume is the same as erd) as 528mm for the new ex823 and 532mm for the old ex823. In terms of spoke length this ends up being a difference of about 1mm from the erd numbers I quoted earlier. I'm sure all my spokes could be 1mm shorter with no problems.
 
- seb

- seb

Turbo Monkey
Apr 10, 2002
2,924
1
UK
jvnixon said:
Those numbers are what Mavic told me when i called (528 for the 823) and i've built with that number and its worked out fine for me.
Click to expand...
How peculiar.

jvnixon said:
I have measured mine (top of the nipple) and its pretty close to that, measure your rim for yourself if you'd like.
Click to expand...
I've measured both of mine in 2 or 3 separate places on each, and they've all come out as 534mm. Your ruler needs checking ;)
 
jvnixon

jvnixon

Turbo Monkey
May 14, 2006
2,325
0
SickLines.com
- seb said:
How peculiar.



I've measured both of mine in 2 or 3 separate places on each, and they've all come out as 534mm. Your ruler needs checking ;)
Click to expand...
I don't use a ruler, I use one of those fitting measuring tape so I have no doubt i'm measuring correctly. Feel free to use what you've measured though if you think its right (maybe you have an older rim)
 
- seb

- seb

Turbo Monkey
Apr 10, 2002
2,924
1
UK
Mine are definitely the "new style" - had the new stickers on and don't have an indentation around the edge like the old ones did.

How weird that we're both measuring and both getting completely different figures.

I presume (since your first post showed you hadn't read my post properly since you didn't seem aware that I'd already measured my rims) that you didn't read the bit where I mentioned that if you measure the ID you need to add 8mm on to get the ERD due to where the nipples end up??
 
Eren

Eren

Turbo Monkey
Mar 18, 2006
2,874
0
mill creek, WA (now in Surrey UK)
- seb said:
Mine are definitely the "new style" - had the new stickers on and don't have an indentation around the edge like the old ones did.

How weird that we're both measuring and both getting completely different figures.

I presume (since your first post showed you hadn't read my post properly since you didn't seem aware that I'd already measured my rims) that you didn't read the bit where I mentioned that if you measure the ID you need to add 8mm on to get the ERD due to where the nipples end up??
Click to expand...
if your so sure he did it wrong, ignore what he wrote and order away :lighten:
 
jvnixon

jvnixon

Turbo Monkey
May 14, 2006
2,325
0
SickLines.com
- seb said:
Mine are definitely the "new style" - had the new stickers on and don't have an indentation around the edge like the old ones did.

How weird that we're both measuring and both getting completely different figures.

I presume (since your first post showed you hadn't read my post properly since you didn't seem aware that I'd already measured my rims) that you didn't read the bit where I mentioned that if you measure the ID you need to add 8mm on to get the ERD due to where the nipples end up??
Click to expand...
I read what you wrote but I was just reiterating that you can measure your own rims if you didn't believe my numbers and run your numbers.
 
- seb

- seb

Turbo Monkey
Apr 10, 2002
2,924
1
UK
Discostu said:
I have both old and new ex823s and I'll double check, but I could swear the ID on the newer rims is smaller than the old ones.
Click to expand...
You could be right, my old one is built up so it's hard to measure accurately. It's within a couple of mm though imho, certainly nothing like the 6mm change in DTs calc.

Discostu said:
If you go through mavic's tech documents on these rims you'll find that they list "Spoke support diameter" (which I assume is the same as erd) as 528mm for the new ex823
Click to expand...
What we have here is a difference of opinion. Mavic think you should screw your spokes in up to the point of nipple/rim contact. Traditional ERD measurements are with the spoke screwed in to the end of the nipple. So their "SSD" is NOT the same as ERD - hence the discrepancy, and hence the different terminology. General rule is to add 3-6mm to SSD to get ERD, apparently. Which takes us to 531-534mm.

More info here: http://www.sheldonbrown.com/rinard/spocalc.htm#MeasureHubAndRim
and here: http://groups.google.com/group/rec.bicycles.tech/browse_thread/thread/a4e7bf91e487b4b9/a41e554624e70df8

JV, just to be clear maybe you should make a note about SSD/ERD on your article, and not call their figure ERD, since they themselves don't.
 
- seb

- seb

Turbo Monkey
Apr 10, 2002
2,924
1
UK
I'm gonna go between the two and use 531mm now I know a bit more about it. I guess DT is pretty close after all ;)
 
jvnixon

jvnixon

Turbo Monkey
May 14, 2006
2,325
0
SickLines.com
While Mavic may call it SSD in their tech docs, the measured value i got was the same as the way Sheldon's picture shows it but i measured directly on the rim (with no spokes but with the nipple inserts knowing where the head of the nipple end up) and not by measuring each individual piece which can often give errors (bent spoke, rounding, etc) so I probably won't change it.
 
- seb

- seb

Turbo Monkey
Apr 10, 2002
2,924
1
UK
Well I think maybe you need to get a nipple in your hand and an insert in your hand, and have a close look. The top of the nipple (in my case anyway) ends up 4mm further out than the rim ID.

Anyway, I'm bored of this now, I've ordered my supercomps and hopefully all will be good. 256/258/256/256 for hope pro2 (20mm front/150x12mm back)
 
jvnixon

jvnixon

Turbo Monkey
May 14, 2006
2,325
0
SickLines.com
- seb said:
Well I think maybe you need to get a nipple in your hand and an insert in your hand, and have a close look. The top of the nipple (in my case anyway) ends up 4mm further out than the rim ID.

Anyway, I'm bored of this now, I've ordered my supercomps and hopefully all will be good. 256/258/256/256 for hope pro2 (20mm front/150x12mm back)
Click to expand...
I measured it with the insert in there and I know where the nipple sits and that's how i measured it myself. There is some leway as you know so you'll probably be fine.
 
J

Jonny5

Monkey
Feb 13, 2007
502
0
Why not use the two old spoke method and measure it properly? Thread nipples on and measure the cross over.
 
M

Mr Nug

Monkey
Aug 26, 2007
138
1
UK
Sorry I didn't read the whole thread and didn't realise the debate that was going on here!

I originally ordered my parts via mail order using the 538mm figure on the website. By the time I'd laced the wheel up, things didn't look right and measured the ERD of the other rim using the two spoke method (the way I've always done it). I screw the spoke into the nipple until it butts up against the bottom of the groove in the nipple.

It's definitely 532mm but the wheel can take +/- 1mm error in spoke length without any issues.
 
leprechaun

leprechaun

Turbo Monkey
Apr 17, 2004
1,009
0
SLC,Ut
We've been using 530 with 16mm nips for a couple years now with good luck. the numbers you get are the longest you can go, so err on the shorter side.

I've found that the 16mm nips, while being 4mm longer act like they're 2mm longer in terms of thread insertion.

Krispy
 
J

Jonny5

Monkey
Feb 13, 2007
502
0
its not subjective. ERD is measured from the top of the nipple.



1. Insert two old spokes into holes exactly opposite each other on the rim. Count holes to be sure.
2. Screw some nipples onto the spokes.
3. Pull them tight and measure dimension A in the figure (the diameter to the edge of the nipples, where the spokes dissapears into them). Do this at several spots around the rim and average the measurements.
4. Measure the length of a nipple (dimension B in the figure) and add it twice (once for each nipple). The result is Effective Rim Diameter (ERD). Thus,

ERD = A + 2B.
 
J

Jonny5

Monkey
Feb 13, 2007
502
0
I do the same, but instead I just have 2x 302mm spokes with the elbow cut off to make them exactly 300mm and thread them all the way to the top of the nipple- apply some glue. Then you measure the over lap. Then take that overlap from 600. Easy as pie.
 
- seb

- seb

Turbo Monkey
Apr 10, 2002
2,924
1
UK
Yep, I know how to measure an ERD, I'm not questioning that :) The point is that that ISN'T how Mavic get their measurement, which they DON'T call ERD.
 
J

Jonny5

Monkey
Feb 13, 2007
502
0
haha, yeah fair enough. Measure twice, cut once. I HATE having to rebuild a wheel because the spoke length was off. Drives me ****ing batty.
 
- seb

- seb

Turbo Monkey
Apr 10, 2002
2,924
1
UK
I've nver had to do that yet, but I know with an EX823 I'd be crying haha, ****ing nipple cups! Glad I've got a proper Park spanner insted of the crappy painful Mavic tool for them now.
 
M

manchvegasbulit

Chimp
May 23, 2004
18
0
manch vegas
Hello All,
It was brought to my attention that there has been some questions about the ERD on the Mavic EX823. I am one of there customer service reps and I can assure you the ERD is 528, with a 0 offset, and with the hollow eyelets. Im not sure why the DT site has 538, maybe a miss print, but I will contact them today to let them know.

cheers,
kyle
 
- seb

- seb

Turbo Monkey
Apr 10, 2002
2,924
1
UK
Ah, of course.

"I can assure you the ERD is 528"

Well I can assure you that you are incorrect. Mavic SAY 528, but the number they give you is NOT an ERD, it's a different measurement that Mavic choose to give.

I don't know how much clearer I can be on this variation, and frankly I'm pretty bored of debating it.
 
Salami

Salami

Turbo Monkey
Jul 17, 2003
1,784
118
Waxhaw, NC
- seb said:
I believe that this shortness was because DT's calculator shortens the spokes when you select longer nipples WHICH I BELIEVE TO BE A MISTAKE. I've read numerous threads (no pun intended) on the subject and compared my own 12mm and 16mm nipples, and my conclusion is that spoke length is irrespective of nipple length. Most nipples have the same amount of threading at the far end, and all that really changes is elongated flats for your wrench. Some nipples seem to have 1mm of extra threads maybe, but certainly not 4mm.

Oddly DT's calc persists in shortening spokes for longer nipples, and you'd think that they'd know.... nevertheless, I'm going to ignore them, and think that my fellow monkeys would be well advised to do the same.


I'm about to order my spokes, and unless someone on here can convince me that some of the above is wrong, I'll be using 534 as my ERD and ignoring the what DT calc says about 16mm nipples. I'll be using several different spoke calcs cos I don't trust DT any more.
Click to expand...

DT nipple length does affect the spoke lengths! It has been about 2 years since I have laced an EX823 but the nipple length is important. If you have any doubt this is wrong thread a 12mm & 16mm nipple all the way onto a spoke and measure to the end of the nipple, the 16mm nipple adds about 2-3 mm to over all length if my memory is correct. The spokes need to be shorter to compensate.


http://www.ridemonkey.com/forums/showpost.php?p=1461737&postcount=30
 
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