Merry Christmas, does anyone happen to know the ERD of a MP2 or GM 26" rim?

[Andrew]

I am looking at getting either the ex729 or ex719.  I have a 729 already and it is very rigid.  Both are for downhill mtb and will take upto a3" width tyre. . I was hoping to save some money and use a brand new set of Magic Pie spokes and nipples I have. They have a maximum usable length of 119mm, minimum 110mm

[Bikemad]

Are the pie 2 spokes 12or 13g ?

I've just measured my MPII and MPIII spokes and they are both ~2.3mm diameter, which according to the Sapim site is 13G:

14G = 2,0 mm
13G = 2,3 mm
12G = 2,6 mm

The MKI Pie used longer 12G spokes with 13G nipples:



If you need to use new spokes of a different length, you might want to consider using butted spokes which are 13G at the hub end and 14G for the rest of the spoke and nipple.

If I can get some PIE 2 motor measurements I can try and work out the spoke length suggested by a spoke calculator.

That's not a good idea because spoke calculators assume the spoke are equally spaced around the hub, but the MPII and MPIII uses an unorthodox spacing pattern which the spoke calculator will not allow for.

If you place your wheel horizontally on the floor, you can then hang a plumb-line against the inside of the rim (or perhaps a set square?) and mark the floor where it touches, and then repeat on the opposite side (180 degrees apart) and then lift the wheel away and measure the distance between the two marks on the floor.

You will also need to consider the length of the nipple sticking out of the two rims, as I suspect it might be inset further due to the eyelets on the Mavic rim.

Example
If the Mavic rim inner diameter is 8mm larger than the GM rim, then the spokes will need to be at least 4mm longer.
If the nipple protrusion is 2mm less on the Mavic rim, you will also need to add an additional 2mm to the spoke length.
So, if the pie spoke was 110mm long, the required spoke length for the Mavic rim will be 116mm.

If the spokes you have are only slightly too long, you might still be able to use them. If you lace the wheel so the spoke heads are on the inside of the hub flanges and the spokes on the outside, it will make a much stronger wheel and also support the spoke elbows much better where they attach to the flange, and should take up some of the additional length.



Here's my Pie with the spokes re-fitted on the outside of the flange as described above:


Alan
 

[Andrew]

That is some excellent advice about having the spoke elbows on the outside of the flange so they sit tight against the flange edge.   

As for the pie spokes, with all things considered I think they will be too short. The maximum usable length of 119mm includes the nipple up to the base of the head with the nipple only just screwed to the thread.  Wishful thinking, but still maybe worth a go before I purchase longer made spokes.

Alan, thanks as always for giving up the time to demonstrate things so thoroughly.

[MAGICPIE3FOCUSPOWER]

Still I don't know why the people of GM install spokes in the wrong way!

The countersink hole is just for preventing spokes to brak when the spokes are laced in a angle.
The countersink hole is not for spoke head.

The only good way to lace the spokes are in second picture!

Also I did have a look at my Magic Pie 3 both side inner and outer has countersink holes.
I think they should thinking before drilling......