hi, going from rim with ERD 557mm to one with a 559mm ERD. Using the same hub. Existing spokes should be ok as its only a 1mm difference in spoke length?

Have you actually measured these ERDs or are you just going off manufacturer info?

manufacturers info. Have I done a whoopsie?

You should always measure the ERD yourself if you’re going to the trouble of building the wheels, often the manufacter info is off, I’ve just received a brand new DT EX471 rim, manufactrer ERD says it should be 662, but I measured an average of 558.25, how much different 3.75mm makes over the course of the whole wheel I don’t know, but the ERD quoted is often a bit off, it must be hard to make rims completely round 100% of the time 🙂

Possibly, some (Mavic?) used to quote something that wasn’t quite ERD and a couple of other manufacturers are notoriously inaccurate.

I had one manufacturer who’d quoted an ERD that would have put the spokes pretty much on the tyre bead. It’d been like that for 2 or 3 years on their documents. (It’s now corrected.)

Should be fine – i’ve done it with a couple of mm either way (assuming the ERD is correct of course).

In fact i’ll be doing the same myself next week on a set of wheels I have just paid for – wanted the hubs mainly, but as luck would have it, the decent DT DB spokes can be re-used too! 1mm difference, result!

Assuming the erd numbers are correct, how far up the nipple does the spoke come currently?

not sure , at work trying to figure it out if its a goer

Should be fine as long as the current ones aren’t on the short side.

Measuring ERDs is fine if you have everything except spokes, but if you need to order things in… (have never measured ERDs, have never had a problem, may consider doing it in future if it’s for an existing rim).

Personally I’ve never had a problem going off manufacturer ERDs (albeit with some extensive googling and checking of spoke calculator databases to see whether people were finding the manufacturer figure accurate or not), but it doesn’t hurt to verify. And yes, Mavic used to (still?) quote a figure different to ERD.

You have easily a couple of mm of overall leeway in spoke lengths so it just depends where your current build sits in the acceptable range. A rough “will I be ok with 2mm more ERD?” guide:

– If you can see spoke thread poking out of the hub end of the nipple then no.
– If you look under the rim tape and the spoke end comes up to the very end of the nipple then yes.
– If the spoke end sits at the base of the nipple threads (ie where the main spoke extension meets the base) then probably yes but be cautious.
– If it turns out to be “no” and your current nipples are 12mm then you could just buy some 14mm nipples and they’ll take up the slack.

All the above is just advice from some git on the internet, don’t sue me, etc 😉

Depends. On the face if it, everything equal, it’s less than 1mm difference per spoke, which should be fine.

But there’s too many variable to be sure. There are a couple of different ways manufacturers define ERD – spoke level to bottom of driver slot in nipple, or level with top of nipple. Spokes can be chosen which are rounded up to the nearest mm required or rounded down, or up/down to the nearest 2mm. Or are the wrong length, but just about OK in terms of thread engagement.

In your case, those might not apply, or might cancel out, or might add up to spokes which are in no way compatible.

But if you’ve got both, and you’re not in a hurry, dismantle and measure up, order if you need to.

Edit. Bez said it better, plus mentioned 14mm nipples.

fantastic info and guidance all, much appreciated.

Where I said “where the main spoke extension meets the base” I meant nipple instead of spoke. Oops. Might still be unclear anyway: my word brain is have a bits of a shutdown today.

all that advice, ruined…..

I’ve just received a brand new DT EX471 rim, manufactrer ERD says it should be 662, but I measured an average of 558.25,

Did you measure it with the PHR washers in place? with them installed you get an ‘effective ERD’ of 662 which is what you need for calculating spoke length.

If you did measure it with the washers in place I apologise, but your discrepancy does seen suspiciously close to 2 washers’ worth.

+/-1mm is an acceptable tolerance IMO as many manufacturers make spoke in 2mm length increments – there’s a huge amount of thread redundancy on spokes anyway.

Did you measure it with the PHR washers in place? with them installed you get an ‘effective ERD’ of 662 which is what you need for calculating spoke length.

If you did measure it with the washers in place I apologise, but your discrepancy does seen suspiciously close to 2 washers’ worth.

No I didn’t 😳 the washers brings it to 600mm, thanks for the warning!!

WTF is with all the numbers? We’ve had 558, 559, 662 and 600 for the same rim. I thought it was all typos at first (the 662 should have been 562 for a 27.5″ rim, right?), but then with washers it’s 600mm? Are you folks using toilet rolls for washers, rubber tape measures or what? 🙂

Manufacturer ERD is 537/562/600 for 26/27.5/29″, I assume we’ve got a 29 here then…? 😕 But then we’re allegedly starting from a 557mm rim on the current wheel. My head hurts. No, wait, the 600 is another typo and it should be 560 and we’re all talking about 27.5s after all…?

It’s Stevelol’s keyboard that’s going wrong, isn’t it? It’s not me? Right? 🙂

the ERD quoted is often a bit off, it must be hard to make rims completely round 100% of the time

Well, quite: I suspect the roundness is probably more likely to be a bit off than the ERD is. If you’re going to measure a rim, measure at multiple points across it: you may well find that the ERDs average out to the quoted figure…

It’s been a long day trust me and yes I’ve typo’d the hell out of calculating these spokes today!!! Lmao I originally got an erd of 558, but put 588 into spoke calculator and ordered the wrong spokes. Then the helpful chap mentioned the washers and I noticed the typo and corrected it to 560, but typed 600 here for God knows why.

It’s time for bed I think….