E.R.D.

16 12 2012

A few weeks ago, I built a wheel with a Hope Fatsno hub and a Surly Marge Lite rim. Good combo. I used a few different spoke calculators and did a bit of web research on what I might find with the numbers because I have zero experience of building with wheel components from these brands.

You may remember that my calculations based on the Surly supplied E.R.D (effective rim diameter) were out by about 1mm. Not a lot, but generally, when you build with aluminium nipples, you need to get it spot on, or even err on the side of too long. With an effectively singlewall rim, you need to be exact. The reason: in order to get the best from your alu nips, they need to have spoke threaded into the bulbous, saucer part that sits inside the rim. If you don’t do this, they will eventually fail at the ‘shoulder’ where the saucer part becomes cylindrical.

Ok, so I should have measured the E.R.D. The rims have 12.5mm offset spoke holes to allow builds with symmetrical 170mm O.L.D hubs and 135mm offset hubs. The Fatsno is a 170mm hub and the spoking angle is roughly symmetrical, so it is best to build side-to-side. In other words, when you calculate the spoke length, you need to allow for this offset. Two ways to do this: take 12.5mm away from the right/left-flange distance or make a rough guess at about minus 1-1.5mm in spoke length.

The quoted E.R.D for the Marge Lite rim is 543.5mm, but my feeling is that this *allows* for the offset as when I measured the E.R.D the result was 546.5mm (this was flush to the bottom of the nipple, so that each nipple is ‘full’ of spoke). This would make sense: when I used the DT Swiss spoke calculator, I did not correct for offset and used the quoted 543.5mm E.R.D and out popped 264mm spokes.

So when I went back and plugged the new numbers into freespoke, into which you can add offset measurements, I get exactly what I found I needed in practice.

Interesting in some ways! I should add that the Hope Fatsno hubs and the Marge Lites in particular seem very good quality. There is a lot going on with Surly’s new rims: well worth a look over the simple, singlewall rims from other brands.

Advertisements

Actions

Information

5 responses

20 05 2014
Jerome Esguerra

Hi there! very nice post. I am interested in building my first wheel set using Marge Lites and Fatsnos. Did you end up using 264mm spokes all around for both the front and back? I’m planning on using brass nipples. I’d appreciate your reply very much. Have a great day!

21 05 2014
velopest

Thanks! No, just the back! But both r and l were 264, with brass nips you have a bit more wiggle room, but 264 should work well!

21 05 2014
Jerome

Thanks for the reply! Do you happen to remember the length of the front spokes you used? Cheers!

21 05 2014
velopest

i didnt build the front wheel with hope hubs. i used a different rim and different hub!….sorry!….if you search mtbr fatbikes forum, im sure there is a thread or two with info about the fatsno front and marge lite.

21 05 2014
Jerome

Oh ok. Thanks a bunch!

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s




%d bloggers like this: