Bob Dopolina 

I'm finding conflicting info for this rim. Anyone have CONFIRMED ERD numbers for these rims?

mrrabbit 

This is no such thing as "confirmed" ERD's per se.

ERD means "Effective" Rim Diameter. Notice the keyword "Effective".

Any ERD that is published WITHOUT specifying where the aim is at on the nipple and WITHOUT specifiying what type and length of nipple used is NOT TRUSTWORTHY!!!


For example the ERD for the Open Pro is 602mm when aiming for the screwdriver flat of a standard 10mm or 12mm nipple using standard boxed factory threaded spokes.

For example the ERD for the Open Pro is 604-605mm when aiming for the top of a standard 10mm nipple using standard boxed factory threaded spokes.

Switch to inverted nylock equipped nipples and suddenly those ERD's are useless because you have to go much higher in the nipple thereby easily adding another 8-10mm to the previous ERD.

=8-)

operator

Length of the nipple doesn't matter. A 'long' nipple (12mm+) has the same amount of threading in the same placea as a regular 12mm nipple. Cutaway nipples will show you this. You always calculate based on assumed 12mm brass nipple. The ERD does not change. If you use longer nipples it just covers more of the spoke up. It doesn't mean you can use a shorter spoke length.

As for the OP, why doesn't he just measure it?

operator

This is a special case, and it's obvious you add 10mm -the length of spoke threading on a regular factory or shop cut spoke, to the resulting spoke length. The ERD again, remains the same.

mrrabbit 

Operator:

FSA RD-600

577.5 Using standard profile 12mm nipples w/ boxed factory threaded spokes and aiming for the flat. (Almost never used though...)

593.5 Using FSA's own inverted 12mm nipple w/ boxed factory threaded spokes aiming 2mm below the inverted barrel.

=8-)

Drew Eckhardt 

DT 12mm nipples have 8mm of thread, 14mm 9mm, and 16mm 10mm.

DT spokes have 9mm of thread.

Combine the two and the spokes run out of thread 1mm past the end of a 12mm nipple, at the end of a 14mm nipple, and even with the spoke slot on a 16mm nipple.

https://www.bikeforums.net/showthread...56#post7610856

Use the bottom of the slot for determining ERD with the DT spoke/16mm nipple combination and you may be out of luck when you encounter a small spot on the rim.

The DT calculator takes this into account, recommending shorter spokes for the longer nipples.

I think the longer threads for longer nipples are stupid especially with alloy nipples where a spoke ending below the head may lead to breakage, but marketing expectations from people wanting to use longer nipples to kludge around too short spokes probably trump that.

operator

I'm going to have to read this again when i'm not drunk.

Bob Dopolina 

Jebus,

By CONFIRMED ERD I meant one that the poster is SURE is correct - not a guess or a link to someone else's guess.

And, yes...I know what ERD means.

I don't have tools to measure the rim (not the kind of work I normally do. I produce stuff, not fix stuff) so I was hoping I could find the info here.

Apparently not.

I will contact a friend at Easton.

laura*

The triple butted DT Alpine spokes have 9.5mm of thread. I didn't believe this at first, but I remeasured and compared to DT Champions, and by golly, the Alpines have more thread.

FBinNY 

You're doing better than I am. Decades ago ERD meant effective RIM diameter, or the diameter at the nipple seat. Since the commonly used formulas calculate a spoke length that has the spoke ending at the same diameter, it used to be necessary to add 2-3mm so the spokes end in the heads of the nipples.

Since then some have taken to adding the thickness of the nipple heads to get an ERD that includes the height of the nipples. So we now have 2 ways to measure ERD and nobody bothers telling you which they used, what used to be useful, meaningful data, as no garbage.

mrrabbit 

I've been building wheels since 1984.

Never once in any publication I reviewed back then nor in any discussion with the frame builder I worked next to nor with other very experienced wheel builders was "Effective Rim Diameter" as a term been bound to a "seat" or other physical part where the definition is concerned.

The definition from day one has always been roughly as follows:

"That rim diameter used by a wheel builder for spoke length calculation purposes that results in a properly trued and tensioned wheel WITHOUT any functional or visible issues involving the spokes, nipples or rim."

In other words, if the diameter you measured when calculating spoke lengths resulted in a spoke and nipple combination that resulted in a functionally fine wheel - then that is YOUR "effective rim diameter" for that particular wheel.

If however you are having to grind spoke ends down when done, or are staring at exposed threads at the barrels - an adjustment is needed...

Note the importance of the all caps "YOUR"...

YOUR ERD is not good to anyone else unless you specify the particulars:

1. What profile nipple was used.
2. What length of nipple was used.
3. What restrictions that nipple has.
4. Where you were aiming at in relation to the nipple used.

etc...

One person's ERD is not another person's ERD unless they are both doing the same thing.

=8-)

mrrabbit 

Anal woman! Go climb a mountain!!!

=8-)

FBinNY 

I agree with all your points, and if anyone does his own measuring, it doesn't matter where or how he measures as long as he considers and compensates for the implications. Which BTW- is why I measure all rims myself, and adjust the calculated results according to the spokes and nipples I'm using.

But, when rim makers publish specs we cannot expect that they be psychic and know what spokes and nipples a builder will select.

That's why I prefer that a published dimensions be an actual dimension, something that anyone can measure and duplicate regardless of how he plans to adjust later. Published specs are 100% useless unless they conform to a single protocol, or they clearly state how they're measured.

The current state of published ERDs is analogous to the question of published frame sizes, and handlebar widths where some measure on centers and others to the outside. (and many don't say which) To be useful, published ERDs should state whether they're measured to the nipple seat, or if not, to what height beyond the seat.

mrrabbit 

FBinNY:

You seem to be forgetting something. What you are asking for is "what is". Essentially "rim diameter".

That fine and all...but the problem is most wheel builders are asking for "what works". That's what ERD answers...

I work with a wheel builder who has built just as many wheels as I have and for a few years longer. If I were to give him a list of simply "rim diameters" and a set of adjustment instructions - he would simply set them aside. That's too much trouble...it's not what he wants.

When he asks what will "work" for an Open Pro with 12mm nipples...that it literally what he wants to know...what will "work".

An ERD is what I give him. He's happy....cause that is exactly what he is asking for.

Same for most users popping in here asking the numbers question. They are not asking for a "what is" number to then do more measurements and adjustments with - most don't even want to or even have the tools to do so. Most are asking for the "what works" number so they don't have to do that - so they can just order the spoke of the right length and nipples and get right down to building the wheel.

That is essentially how ERD ("effective rim diameter") came about over the decades...

It's not an "as-is" product "spec" standard and was never meant to be.

=8-)

FBinNY 

We're debating the same side of two coins, and basically we agree.

If you want the question of what will work, which, as you point out is what people want, you have to have a language that gives data and defines what that data is in a standardized way.

Take something as weight of packaged goods. When you buy a pound of coffee you want to get 1# net weight, so you're getting a pound of coffee, not including the container. But if coffee was sold by gross weight, you'd never know how much coffee you were actually getting.

Likewise with rim diameters. You ask the manufacturer for an ERD so that you can calculate a spoke length before actually seeing the rim. The manufacturer has no way of knowing what rims and spokes you plan to use, so what does he publish? The actual diameter? a diameter that assumes you have standard nipples with 3mm thick heads? a diameter based on 12mm nipples? or longer nipples? As you point out these are all different, but the one thing that is certain is the actual dimension of the rim. Mavic can measure that in France, and I can measure it in NY, and we both will get the same answer.

Once he has a good starting point that he can count on, the builder can make the necessary adjustments according to his needs and preferences. Otherwise we have the situation of a husband and wife three fourths of the way to the airport each saying "I thought you were bringing the tickets".

operator

My head just exploded.

greyghost_6

There is no difference the spokes and nipples make in finding ERD! Period. That's like saying "Oh well you used a WALMART ruler, TARGET rulers yield different results" Using one kind of spoke and saying it changes the diameter of the rim is crazy talk. I think what you are trying to say is that when you use different spokes you need to be careful where you measure from since the top of the nipple head is not counted in measuring ERD. What good is ERD to find spoke lengths, if it relies on spoke lengths? There is no "YOUR ERD" I have never seen a rim change ERD, unless its oval. The effective part is because some rims holes are not always perfectly in line, some are stagered, some rims are offset, etc. You can measure it with spokes if you want, but it leads to confusion if you are not careful as you can see. Why not use a piece of wire, knot one end and make sure it hits the eyelet of the rim, thread it through the other side, mark it where the nipple would hit, and measure the wire length? Do this on a few other parts of the rim too to make sure it isn't oval. This keeps keeps nipples and spokes out of the equation if you are getting different results using different brands

Bob Dopolina 

I work with rim factories every day. I have NEVER had a factory ask me anything about how I will build the wheel, how my customer will build the wheel or what parts will be used if I ask them for ERD.

I ask for an ERD and I get a single number. Every time.

I also just check my ETRTO manual (which sets the standard for every kind of tire and rim manufactured in the world) and there is no official definition of ERD so I'm not sure what is being quoted here.

I 'popped in' to see if anyone else in the community has ever rebuilt these wheels (I'm helping a friend) and if they happened to know the ERD of this rim. Nothing so far so I emailed the factory.

My guess is they'll give me a single number and not ask me a thing about what nipples I'm using...

greyghost_6

+1 As they should. But if they DO ask you how long your nipples are its probably best to post pics because I have to see this

Bob Dopolina 

...not very long but boy are they thick...

mrrabbit 

Need a pic of that operator...

=8-)

mrrabbit 

So if a factory aims for the top of a nipple for their ERD...you'll just use it "as-is" when building the rim up with 16mm nipples for the same spokes?

Or are you going to come up with your own ERD in that instance?

=8-)

urbanknight

Can you use the 2 cut spokes & 2 nipples method mentioned on Sheldon Brown's site? That has yet to fail me.

mrrabbit 

I don't know if you have realized this yet FBinNY...but what you are asking for is what you are already getting.

For example:

Mavic aims for the screwdriver flat of standard profile 10mm, 12mm and 16mm nipples when they publish their ERDs for traditional rims. I know this because everytime I've done the same - I get the same number +/- .5mm.

What does Damon and company do on SpokeCalc? They add 3mm to all of Mavics numbers and they tell you exactly why. They are aiming for the top of a standard profile nipple.

What's the standard in the above for providing ERDs? Simply telling people what the objective was aiming-wise.

Mavic doesn't tell you, but Damon and Co. and I know. And when we publish ERDs, we do tell you.


That's the problem - not standards - but communication. Period. It's worse when someone can't get the definition right to begin with.


Now let's flip it around...


What do you do though when someone who doesn't get it starts publishing actual ERDs as Rim Seat Diameters? You are right back where you started - you can't trust the numbers because you can't be sure that the publisher knows the difference between ERD and RSD unless they tell what they were measuring when they publish their numbers for Rim Seat Diameter.


We don't need a new standard. What we need are people who:

1. "Get" diameter
2. "Get" effective rim diameter
3. An communicate how they got it when they publish their numbers.

That's it in a nutshell..

=8-)

Drew Eckhardt 

Two spokes (insert in opposite holes), two nipples (thread to desired depth), and calipers (measure across the elbows and add to twice the spoke length) do the trick (repeat at several locations and average). Harbor Freight sells digital calipers accurate to +/- .001" or .03mm for $16. Vernier calipers should be much cheaper.