i could use some help with spoke length

[potna]

i am building a rear wheel with a 9c "3kw" rear hub motor. i tried to buy the exact rim twice, but it wasnt the exact rim, twice now, sun ringle mtx39 36 spoke, fine so i have extra rims now lol.

i ordered custom custom spokes at about $100 for the spokes, they are 12g usa made spokes, they are 150mm. they are not the correct length.

i pulled this motor out of a 3kw rear hub so i could upgrade it to a qs205 v3 4t and the qs was a drop in on that wheel, the spokes were perfectly sized and it was super easy to build that wheel.

now i have an extra motor, and tried to buy the same rim and spokes and just built another wheel, but the wheels are different. this rim is hard to get and i am stuck with it, and can use the extra spokes in the future i guess.

so tonight i decided its time i learn how to actually measure the motor and the wheel so i get the right spokes. i created a custom wheel and rim in their calculator, using a single cross pattern their calculator says i need 157.7mm for one side and 156.6. the spokes i have are 155mm spokes and they just wont work. i get to about the 6th spoke, on just one side mind you, and it just isnt long enough to reach the nipple, it wont even touch it. i played around with loosening and tightening the 5 spokes to try to get the spoke closer to the nipple but it wont reach.

so my question is this, am i doing something wrong like usual or do i really need to get 157.7mm spokes? i thought for sure i had a little wiggle room with these numbers, but it appears not. seems like if my spokes were too short i could at least be able to get a couple threads on each nipple, but nope. this situation makes me feel kinda dumb

any advice would be appreciated.

btw, if you didnt already extrapolate it, the qs205 v3 4t has the same dimension as my old motor i am now trying to build, its the dang variations on the mtx wheel that is throwing all my work into the gutter, i would have thought they would all be the same, they have the same model number but nope they are different.

i am super tempted to buy the tool and just make my own spokes in the future, if that matters

 

[Chalo]

i ordered custom custom spokes at about $100 for the spokes, they are 12g usa made spokes,

Mistake. 12ga spokes and bicycle rims don't go together, no matter how often Chinese junk merchants or window licking dingdongs combine them. Their correct operating conditions don't overlap. Barely tight enough for 12ga spokes is too tight for bicycle rims.

i created a custom wheel and rim in their calculator, using a single cross pattern their calculator says i need 157.7mm for one side and 156.6. the spokes i have are 155mm spokes and they just wont work. i get to about the 6th spoke, on just one side mind you, and it just isnt long enough to reach the nipple, it wont even touch it.

You have bad data for your calculation, or else you're using the wrong lacing pattern.

If you post the dimensions for your hub and rim, maybe one of us can do the calculation for you.

 

[amberwolf]

the spokes i have are 155mm spokes and they just wont work.

Are they actually 155mm spokes? (meaning, what do they measure, in your hand, in case the seller mistakenly cut them short)


If they are, then there is something in the measurements of the hub and rim that are incorrect, or something in the calculator used that gave incorrect results, or both--you should at least be able to get a couple of threads engaged for every spoke and nipple even if they are a couple mm short, (though if they're not engaging enough threads you might break the nipples or strip the threads during tensioning...the initial lacing should still be possible at least further than a few spokes).


If it's useful, the first google hit for the rim you list gives these specs. I didn't look any further, but the manufacturer may also provide them; you may be able to compare the specific rim part number and version number (if any) with the manufacturer to get specs to double check your numbers. The manufacturer of the rim may have a way for you to tell which versions of the rim you have there, to verify which specs each would have.

Sun Ringle MTX39 Rim 26" 36h Presta, Black
Sun Ringle 0E6E058136051
Color: Black
Weight: 660 grams
Diameter: 559
Valve: Presta
Tire Type: Clincher
Brake Track: No Brake Track
Spoke Drillings: 36
The Sun MTX series is a super heavy-duty design perfect for DH and freeride applications, or just people that break a lot of wheels.
Double wall design
Welded joint
Heavy duty extrusion for maximum durability
Eyeleted spoke holes
Item Specifications
Manufacturer Spec ERD: 525
Wheel Size: 26"
Rim Center Offset: 0
Rim Joint: Welded
Rim Width (Internal): 26

 

[Chalo]

i ordered custom custom spokes at about $100 for the spokes, they are 12g usa made spokes,

Mistake. 12ga spokes and bicycle rims don't go together, no matter how often Chinese junk merchants or window licking dingdongs combine them. Their correct operating conditions don't overlap. Barely tight enough for 12ga spokes is too tight for bicycle rims.

i created a custom wheel and rim in their calculator, using a single cross pattern their calculator says i need 157.7mm for one side and 156.6. the spokes i have are 155mm spokes and they just wont work. i get to about the 6th spoke, on just one side mind you, and it just isnt long enough to reach the nipple, it wont even touch it.

You have bad data for your calculation, or else you're using the wrong lacing pattern.

If you post the dimensions for your hub and rim, maybe one of us can do the calculation for you.

 

[gobi]

ERD - Your rims have ERD on the spec sheet, I bought used rims of ebay and had to measure ERD with a spline from one of my kites. Maybe you can measure and confirm ERD.

Pain - Spending $$$ on spokes does not lead to happiness if they don't work. I have thought about picking up some el cheapo spokes (longer than my length and do a mock up with them and then mark each side with different color marker and taking them off and measuring each color length and averaging it.

 

[potna]

i am an idiot. the second rim was also a 32h, and my hub is 36h. so much for saving money and doing it my self lol

just thought i would follow up. the good part of this is that these mistakes are costing me and i shall pay closer attention.

 

[999zip999]

Is the rim 559 ERD ? 26in. Right ? 36 hole ? I will look tomorrow.