spoke length calculation

[patpatbut]

Hi all,

I tried to use spoke length calculator using spocalc.xls but I could not quite understand what to enter.

I will be using this rim from Mavic EN321 26" rim.

Mavic EN321 Disc MTB Rim 2014 | Chain Reaction Cycles

With Bafang CST motor



Any help would be great!

Thanks
Pat

 

[Deleted member 4366]

What's the ERD of the rim?

 

[patpatbut]

What's the ERD of the rim?

559mm? Recommend rim tape says 559 from the web site.

 

[Sacko]

I was measuring a "559mm" rim yesterday as I was calculating a spoke length.

559 though is the measurement on the outer-wall over the rim, not the inner one the nipple sits on.

I am guessing you would be looking at something like 542mm. Check the Mavic website though.

 

[Deleted member 4366]

Measure the inside diameter and then add 5mm.

 

[Sacko]

Close, 539mm

Mavic EN321 disc 26" mtn rim dimensions | Freespoke

 

[patpatbut]

Thanks everyone. Back to the question, I know I need two sets of spokes for left and right sides. What measurements should I need to calculate the spokes length?

Thanks again
Pat

 

[Deleted member 4366]

The BMSBattery rime are ERD 539 or 540 mm for which I use 210mm spokes. If you measure the ID of your rim, I can compare it.

 

[banbury frank]

Hi we use 222 mm long for one side and 224 for the other with mavic rim and 500 watt CST motor

Frank

 

[patpatbut]

The BMSBattery rime are ERD 539 or 540 mm for which I use 210mm spokes. If you measure the ID of your rim, I can compare it.

What does ID stand for?

Pat

 

[patpatbut]

Hi we use 222 mm long for one side and 224 for the other with mavic rim and 500 watt CST motor

Frank

Thanks Frank. Are you using the same bafang CST? How many cross do you use?

I am planning to lace one cross only.

Pat

 

[Deleted member 4366]

What does ID stand for?

Pat

Inside diameter.

 

[Hackney Andy]

This has everything...apparenly, including numerous spoke length calculators:


Wheelbuilding

 

[patpatbut]

Close, 539mm

Mavic EN321 disc 26" mtn rim dimensions | Freespoke

Is 20mm measurement from the photo called Inside diameter ?

 

[patpatbut]

Thanks Frank. Are you using the same bafang CST? How many cross do you use?

I am planning to lace one cross only.

Pat

Hi Frank,

Would you mind to give me some advice?

How do you calculate those values?

Many thanks
Pat

 

[banbury frank]

Hi We use one cross I cant explain how we spoke it is two complicated

No we use another make off motor

Alan Rayburn ( catsnaper )the spoke maker is back in the uk now


Sorry Frank

 

[Deleted member 4366]

Pat
If you measure the inside diameter of the rim, I can tell you the spoke length and your problem will be solved. It should be in the region of 530mm, if that helps.

 

[patpatbut]

Pat
If you measure the inside diameter of the rim, I can tell you the spoke length and your problem will be solved. It should be in the region of 530mm, if that helps.

Thanks Dave. I just measured it and it is 529mm. Would you mind to tell me how to do the calculation?

In the end, I would like to learn how to do by myself.

Thanks
Pat

 

[Deleted member 4366]

The calculation is very simple. My rim is 530mm ID. I used 210mm spokes, so they'll work on yours too. You should use a 2-cross pattern because of the torque from the motor. 1-cross is OK for a low power motor like a Q100.

ERD is approximately 6mm bigger than the ID.

When I use the spoke calculator with flange dia 164mm and flange offsets of 22mm and 11mm, it gives spoke lengths of 211mm and 212mm if you want to be exact. With a double walled rim, spoke length is not so critical on the long side becuse it doesn't matter if they poke through the nipple a bit, so if you're ordering from a spoke-maker, you can order 212mm, but 210mm will be OK from a stockist that only has standard sizes.

This calculator has your rim in its database. It shows the ERD as 536mm which ties up with my estimate:
Edd, an easy to use spoke calculator