The ONLY way to measure bicycle rim ERD: a Wheelbuilding hot take!
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- Опубликовано: 1 июл 2024
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Accurately measuring Effective Rim Diameter is crucial in allowing you to correctly calculate spoke lengths in bicycle wheelbuilding; let's put what ERD is to rest once and for all, and kick some pedants to the ground whilst we're at it ;-)!
Featuring my go to tool the SON Speichen rechner:
www.spokesfromryan.com/produc...
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Super informative! Next time someone is a pedant about ERD, I'm going to link them this video.
YES please @Flying Clown! It's those people that made me want to make this video!
Ryan... what a great little video, simple & informative without getting too technical for those with an interest in the "Dark Art" lol of wheel building. I do hope you continue with more, covering other topics, just like this. Great job, thank you.
LOADS of topics lined up @TheLocalSpokesMan! I'm on a mission to make the whole process much less dark; stick around and I'll shine a light in as many nooks and crannies as I can!
Terrific video , ERD pretty much the quintessential ingredient in the correct spoke length quest. You’ve got my brain working overtime in regard to your upcoming invention. Anyway keep on sharing your wealth of knowledge, take care and enjoy 👍👍
Excellent thanks Paul! You're right, there's only ONE other dimension that can mess with spoke length calc's more than ERD and it's a tricky one for sure...I'll let people guess what it is here if they fancy but for now, hey, I'll keep you all guessing ;-)!
Sure pleased to know this was helpful and that you're intrigued by the upcoming 'ultimate ERD Tool'! I'm still sketching it in my brain but when it's time to shove bits of metal together in interesting ways I'll be sure to let the world know!
Another excellent video Ryan!! Thank you!! Malc
Very welcome as always!
Great video Ryan. Clear and to the point. Calling ERD an moving target is really helpful because its not just the rim that you are measuring, the the diversity of spoke nipples used today has made it impossible to create one uniform standard for measuring. On the topic of pre-made tools I agree that the SON tool is certainly a winner when it comes to readability. The main issue I have with it is that the way the tool sits in the rim only really works on rims that are drilled very straight in both the internal and external rim holes. A lot of modern rims with directionally drilled offset rim holes and asymmetric profiles will struggle to work with this tool. The original Wheelsmiths rim rods had the same problem but the BSC tool has a much smaller head (measuring end point) that allowing the rods to pivot within the rim cavity to allow for an accurate measurement directly across the rim. With the BSC tool, you can also just measure the overlap like you used to with the old Wheelsmiths rim rods. Its another step in the process and then you have to account for the nipple head, but it works. I would agree that there is no perfect tool.
Oooh! Those are some great points and food for thought Adrian! Another type of rim that can prove hard to measure are those that are directionally drilled AND have a very thick spoke bed such as the Ryde Andra 30/40 commonly used for heavy duty or touring rigs: the (albeit roughly) machined countersink on those can play havoc in deriving correct ERD.
Great video, thanks Ryan. When building the ERD sticks, should you factor in further spoke length "growth" as the spokes tension during the building? In other words, if your stick positions the spoke head flush with the nipple top without tension, will the spokes end up longer than needed once they're tensioned up? Hope that makes sense!
@RogerMusson 's The Spoke Length Project takes this into account for you luckily and that's why mine and his ERD sticks that use a standard slotted nipple are flush with the slot and not with t hey nipple top. If you had ERD sticks flush with the top then you'd expect some stick out.
Great video, Ryan! I’ve always found this aspect confusing even though I suspected it was more due to a crisscross of info and explanations - as a nascent wheel nerd, I can feel the need for getting hold of a decent tool for this purpose (I have none at the mo) as I hope to be working out the ERD of a delicious Alchemist 36” carbon fibre rim somewhen soon ⚙️🤩
Glad it was helpful! If you don't want to spend the big bucks then for such a big wheel you could simply increase the length of a pair of ERD stick and use 300mm spokes instead for example; send me an email and I can make some up for you!
Thank you! Very good video😊. You say DT Swiss measurements can be trusted, does this apply to only the spokelengths received from the DT Swiss calculator or others aswell? The lengths differ when comparing calculators
DT's stated Rim ERD's will work with any spoke calculator assuming ERD is what it wants you to input. Remember that DT's ERD number assume you'll be using a certain type of nipple (standard slotted for their entry level and Squorx for their PHR series) alongside any relevant PHR washers.
Currently planning to relace a rim and I made some ERD sticks out of the existing spokes and nipples.
I marked a point on each stick 250mm from the end and when pulled across the rim the marks were 56mm apart, so I caculated 556 mm ERD. Measured three times to be sure.
But when I look up ERD for my model of rims (Mulefüt 80SL 26"), I find multiple sources saying 551mm. I'm guessing that number is the 'nipple seat' measurement.
Yep: almost certainly! You see the problem we’re facing!
An extra 5mm is quite a lot: if using slotted nipples my advice is to only wind your ERD stick donor spokes to the bottom of the slot: this helps account for spike stretch. See my video on how to calculate spike lengths for my favourite Calculator reccomendation 👍🏻
I have been using Wheelsmith Rim Rods forever while making any adjustments necessary for different nipples. Requires a bit of technique to get accurate readings, but then again, I think any method does.
For rims drilled for internal nipples, the Rim Rods don't work because they don't fit through the holes, so then it's time to use spokes of a known length.
That fancy German tool looks pretty slick, but I don't see one in my future.
Never had the joy of owning a pair; I should add some to the colleciton I guess...! My intention with what I'm planning in house is that it will essentially be 'zero technique needed'; pop the rim in, look at the reading; BOOM!
@@RyanBuildsWheels That would be nice, but every once in a while, I get the rims with no nipple access holes. I am planning a video on dealing with those at some point. They are fun.
2 short cut J-bend spokes, 2 14mm brass nipples threaded ALL the way onto the spokes. a normal longer sized, rubber band. insert 1st spoke/nipple to the right of the valve hole, insert 2nd spoke/nipple opposite (the left of the rim seam. attach the 2 j bend spokes with the rubber band, measure from the tip of the nipple to the tip of the other nipple with a quality tape measure (I use a Shimano tape measure). Add to your measurement, 28mm. measure twice in the other direction, the two measurements should be the same, or very very close give or take a fraction of a mm. if their not, you have either placed the spoke incorrectly, or your rim is an Egg shape. (also when re-lacing a used alloy rim, check for this and also flatness on a flat surface, like a marble countertop.
this is how I measure ERD, and it works every time, if you plan to use washers, or use an internal spoke nipple (such as the spline drive from DT swiss with the pro washer) include those in your ERD measuring tool assembly, when taking your measurements, as they will change the ERD outcome.
this is the method I use and it has always worked for me, however their are many ways to measure for ERD and so long as you have a basic understanding of wheel building any method will lead you to a measurement that will work (if any method doesn't you've either done it wrong, or your wheel is an egg) measure twice, calculate spoke lengths, and cut spokes once (or 28..32...36...48...56....64....72....96.... however many spokes you need but personally i'd rather just order them from Sapim or DT swiss then cut them all, been there, done that.
good video! subscribed!
Great stuff! Pleased to have you on board 😀!
The rubber band trick does work well 👍🏻
Big up!
Thanks Neil!
Excellent
Thanks
Thank you for this video, it’s definitely helped.
A related question, if I want to replace a rim, how do I get hold of a rim with the same ERD? Especially if I can’t trust the ERD from the manufacturers.
My partner’s braking tracks are worn, nothing else wrong with the wheels but I can’t seem to get hold of the same rims and if I have to replace the spokes too I might as well build or buy a new wheel.
Good question Graham! One manufactuer who's rim ERD you can trust is DT Swiss; note that some of their rims MUST use washers (the PHR series of rims, such as the EX511, RR481 etc.). After that it's a case of taking things at face value I'm afraid and / or asking others of their experience / measurements.
Remember though; if the ERD is too small you've a few tricks up your sleeve; you can add washers to non washered rims, or use nipples such as Sapim's Double Square which will add another 2-3mm on either side of the rim. Also don't be afraid to 'overwind' spokes by a couple of mm if needed; there are actually benefits to this (see link below).
wheelfanatyk.com/blogs/blog/nipple-threads
@@RyanBuildsWheelsthank you. Really helpful answer. Your videos are great.
Nice video! Do you recommend using washers for a 50mm deep carbon road wheel build? I do not really know when to use washers and when not to :(
Yes I do! I'd recommend a suitably profiled stainless steel washer on any and all carbon builds whenever possible; especially when / if using alloy nipples.
Suitable washers might include Sapim's MG or HM options and the reason you'll want to use them (along with lubrication and suitable weatherproofing technique) is to decrease the effects of galavanic corrosion. See the video by @BillMouldWheels for more on the subject until I manage to make one of my own ;-)! (sorry Bill!)
@@RyanBuildsWheels awesome! Thanks for the reply :D
And I am looking forward to more of your videos and knowledge :D
Why not just use two spokes that will pass each other in the middle and clamp them together with say an electrical strip connector and remove a nipple and measure it in one piece?
Would also work 👍🏻
Is the process the same when spoke holes are staggered? For example I have a Ryde Andra 40 rim.
Yep; these are the same stagger as a rim like that; SOME rims will have the drive side spoke holes on the right of the valve hole (these are left hand) which sometimes get called 'French' or 'B Type' rims but, in terms of lacing the pattern is the same.
A future video will give a full lowdown on lacing :-D!
Wouldn't it be much easier if the rim manufacturers stated RD ( rim diameter of a fixed point) and let us do ERD depending on the nipples. I've no idea where some brands get their ERD from.
Right!?! Feels like they're pulling numbers out of thin air sometimes!
I feel similalrly; it ERD is what we're stuck with right now as the guiding principle for spoke calculations but with education we *could* push to have NSD (nipple seat diameter; what you currently term 'RD') as the standard metric which rim manufacturers publish, and make sure that builders understand that their nipple and washers choices will then 'create' the ERD needed to calculate spoke lengths.
An almost Dada-ist approach to the above can be see in the way that Spank Industries present their ERD...which they term "ERD++" (ERD double boost anyone?!!!!) in an attempt to point out that you need to add nipples+washers to the equation...but they've only managed to muddy the water by not using the term NSD ('ATMO' : to steal a phrase from the great Richard Sachs.)
Whats up with the sound in the video - dips in and out from time to time, like Ryan's previous video with Joey Strongheart in it.
Oh, that's a simple one ;-). A) I need to buy a decent mic, and B) my editing skills aren't as good as they could be yet!
Also, I'm currently going with the philosophy of 'Never Let Perfect Stand in the Way of Good Enough'! What I mean by this is that I get about 1 day a week to attempt to get these videos out on top of trying to run a professional wheelbuilding business...as such whilst I learn a few things like this will slip but I'd rather get an OK video out rather than keep folks waiting for the next exciting drop ;-).
I'm a fucking fool caus i didn't understand anything of this. I can true a wheel and build it. But when it comes to what length of spokes i need to order for a new wheel i have no idea on how to measure it.
Nah, you've got this!
Here's the Spoke Length Calculation and other measurement video:
ruclips.net/video/F5gV2s-dvn8/видео.html
In the video you've just watched I do go into a bit of a rant / detail about the minutiae of ERD ;-).
In this video you didn't actually demonstrate that ERD changes with nipples as all the measurements you took are just with one type...I'm lost with this one...
Also the 150mm spokes that you cut, you weren't clear if that 150mm goes into the nipples or not.
Thanks Joe! Good points :-)! I'm trying to keep video's a little shorter but those details are missing here.
So: 150mm spokes go into the nipple yes; stopping at the point you want the spokes to end up when the wheel is complete BUT taking into account spoke stretch; take a look at my last video '10 minutes of nipples' as a good example of where this might be.
ERD Changes and nipple types; for a super clear example head to 3'17" : this shows the biggest difference in ERD change that I can think of; external vs internal nipples. If you then consider how much additional thread is present in something like a Double Square or Squorx nipple etc (again, see previous video) then that should make things a bit clearer.
Really appreciate all your questions! As an expert in the field it's sometimes hard to figure out what bits of information I need to convey in clearer terms.
so the spokes are exactly 150mm long... then thread a nipple on... not 150mm long from end to nipple end?