[kgginslc]

It seems that info on spoke lengths for wheel building for fat bikes is a little difficult to determine (at least for me), especially for offset wheels for Pugsley and the like. So, I thought it might be nice to have a thread with info on what combinations people have used to successfully build their wheels.

I'll start with my rear wheel Pugsley build:
Hub - Shimano M756 6-bolt rear disc hub, 135 mm, 32 hole
Rim - Vicious Cycles Graceful Fat Sheba (single wall), 32 hole, offset drilled
Spokes - 260 mm 14 g. DT both sides
Nipples - 12 mm brass

This built up pretty nicely. I don't have a truing stand that will accomodate the hub and additional spacer required for a Pugsley build, so I clamped the fork in my Park workstand and mounted the wheel on it. Used twist ties on both sides as truing gauges and sighted down the steerer tube to get it dished correctly.

edit - forgot to add 3x build for both sides

 

[Speedub.Nate]

Isn't it the same as inputing an offset for an asymmetrical rim into the spoke length calculator, just with offsets for both sides?

 

[CLONG]

I built my 100mm rims to an Alfine IGH with 250mm Alpine III's (both sides) and to a Surly disk/freewheel hub with 260mm. Spoke offset ended up about 20.5mm for the NDS and 25mm for the DS.

See a few wheelbuild pics via my build thread here.
And read all about the boring calculations here.

That second thread has some helpful diagrams courtesy of forum-user, meltingfeather.

 

[mikesee]

I'd estimate I've built 100+ fat rims (LM's, 70's, 80's, and 100's) over the past 4-5 years. Unless I was using an oddball hub with non-3x lacing (Rohloff, for example) the spoke lengths have almost always come out to between 258 and 260.

I dare say you could safely use 259 on almost any fat build out there.

But don't blame me if it doesn't work!

MC

 

[kgginslc]

Isn't it the same as inputing an offset for an asymmetrical rim into the spoke length calculator, just with offsets for both sides?

I don't know - that for me, is the problem. Do you enter the offest as a positive or negative number since it's in the opposite direction of your typical offset spoke bed?

 

[kgginslc]

See a few wheelbuild pics via my build thread here.

Good to have links to those discussions here. I read that first discussion and it inspired me to go Full Metal Jacket for my brakes as well. I think I didn't manage to get the bends quite as smooth as yours, but I did take the metal tubing all the way into the brake itself - no intermediate cable run. One thing I neglected to anticipate was that it makes getting the rear wheel off a bit more difficult - there's just enough give to manage it though.

 

[Speedub.Nate]

I don't know - that for me, is the problem. Do you enter the offest as a positive or negative number since it's in the opposite direction of your typical offset spoke bed?

I don't know, either. I haven't built any offset wheels, but notice the offset box on some of the spoke calculators I use. I think it'd be the same result as subtracting the difference from the center-to-flange offset.

But then there was a discussion I read in the last week or so asking if the spokes should cross for increased stability -- left flange crossing to right spoke bed, and right flange crossing to left spoke bed. Seemed like a neat idea to explore 'cept that the spoke holes angle out in the wrong direction. Oh well...

 

[CLONG]

I'd estimate I've built 100+ fat rims (LM's, 70's, 80's, and 100's) over the past 4-5 years. Unless I was using an oddball hub with non-3x lacing (Rohloff, for example) the spoke lengths have almost always come out to between 258 and 260.

I dare say you could safely use 259 on almost any fat build out there.

But don't blame me if it doesn't work!

MC

Even if it's not true 100% of the time, it's good to have a rule of thumb. I'm going to build up another set in the next year or so, so thanks, Mike.

Good to have links to those discussions here. I read that first discussion and it inspired me to go Full Metal Jacket for my brakes as well. I think I didn't manage to get the bends quite as smooth as yours, but I did take the metal tubing all the way into the brake itself - no intermediate cable run. One thing I neglected to anticipate was that it makes getting the rear wheel off a bit more difficult - there's just enough give to manage it though.

That's cool! I was pretty lazy about the bends. I just tried it because I saw it on the Jones blog. There's a simple bending tutorial on Instructables. For the fork I bent around a 32T bashguard.
Also, I actually used a very short piece of the braided hose at the end of both runs of FMJ to aid wheel removal and brake adjustment, it's just hidden under the long rubber boot that extends from the caliper.

 

[dave29er]

I'll second what Mike said on the spoke length. 258 or 260 is what I've used for Large Marge Offset drilling rims with either Surly or Maverick hubs. And 234 and 236 for a Rohloff with a Large Marge. Next time I'll just get one size splitting the difference and make it simpler.

 

[kypa]

I need help with length calculation for a 80mm rim and Nexus 8v. Always spoke length is larger than is needed.

Do i have to take in ming the wide of the rim?

 

[sryanak]

I need help with length calculation for a 80mm rim and Nexus 8v. Always spoke length is larger than is needed.

Do i have to take in ming the wide of the rim?

Rim width makes no difference. Tell us what kind of rim, how many spokes, how many spoke crosses, how much the wheel is offset, if the rim is offset, etc. and people here should be able to help.

 

[kypa]

Thank you.

Rim us a robs'son rim 26' x 80mm. ERD is 548mm and the spoke holes are 20mm from the center of the rim.
Spoke number is 36, 3 crosses.

front hub | Rear hub Nexus 8v
A 28,3 | A 32,2
B 18,1 | B 42,7
OLD 99,8 | OLD 134,5
WL lado disco 21,6 | WL 35,05
WR 31,8 | WR 24,55
s 2,6 | s 2,6
d dl = dr 58 | d dl = dr 92
flange distance 55 | flange distance 55
Nº spokes 36 | Nº spokes 36

My last result are the following:

RearWheel Input Data Output Data
N, total number of spokes 36 cross left length right length
ERD, effective rim diameter 548,0 0 228,7 228,0
OSB, offset spoke bed 0,0 1 231,9 231,3
WL, width from center to left flange 30,0 2 241,1 240,5
WR, width from center to right flange 24,5 3 254,6 254,0
dL, left flange diameter 92,0 4 270,2 269,7
dR, right flange diameter 92,0 3,00 254,6 254,0
S, spoke hole diameter 2,6


Front Wheel Input Data Output Data
N, total number of spokes 36 cross left length right length
ERD, effective rim diameter 548,0 0 244,7 245,8
OSB, offset spoke bed 0,0 1 246,6 247,7
WL, width from center to left flange 21,6 2 252,1 253,2
WR, width from center to right flange 31,8 3 260,3 261,3
dL, left flange diameter 58,0 4 270,0 271,0
dR, right flange diameter 58,0 3,00 260,3 261,3
S, spoke hole diameter 2,6
X, cross number (decimal allowed)(optional) 3,00
WL_effective = W - OSB 21,6
WR_effective = W + OSB 31,8

 

[Frank Z]

Hi y'all. I would feel a little more comfortable starting my wheelbuild (Pugsley offset) if anyone could confirm if I'm right on these calculations:

Front Surly New disc on FlatTop 80;
N, total number of spokes 36 cross left length right length
ERD, effective rim diameter 540,0
OSB, offset spoke bed 10,0
WL, width from center to left flange 16,5
WR, width from center to right flange 56,0
dL, left flange diameter 58,0
dR, right flange diameter 58,0 3,00 256,9 259,6
S, spoke hole diameter 2,4
X, cross number (decimal allowed)(optional) 3,00
WL_effective = W + OSB 26,5
WR_effective = W - OSB 46,0

REAR: Shimano XT disc FH-M756 on FlatTop 80
N, total number of spokes 36 cross left length right length
ERD, effective rim diameter 540,0
OSB, offset spoke bed 10,0
WL, width from center to left flange 14,7
WR, width from center to right flange 36,1
dL, left flange diameter 61,0
dR, right flange diameter 61,0 3,00 254,9 258,9
S, spoke hole diameter 2,6
X, cross number (decimal allowed)(optional) 3,00
WL_effective = W - OSB 4,7
WR_effective = W + OSB 46,1

Thanks for any help and/or comments.

 

[sryanak]

Hi y'all. I would feel a little more comfortable starting my wheelbuild (Pugsley offset) if anyone could confirm if I'm right on these calculations:

Front Surly New disc on FlatTop 80;
N, total number of spokes 36 cross left length right length
ERD, effective rim diameter 540,0
OSB, offset spoke bed 10,0
WL, width from center to left flange 16,5
WR, width from center to right flange 56,0
dL, left flange diameter 58,0
dR, right flange diameter 58,0 3,00 256,9 259,6
S, spoke hole diameter 2,4
X, cross number (decimal allowed)(optional) 3,00
WL_effective = W + OSB 26,5
WR_effective = W - OSB 46,0

REAR: Shimano XT disc FH-M756 on FlatTop 80
N, total number of spokes 36 cross left length right length
ERD, effective rim diameter 540,0
OSB, offset spoke bed 10,0
WL, width from center to left flange 14,7
WR, width from center to right flange 36,1
dL, left flange diameter 61,0
dR, right flange diameter 61,0 3,00 254,9 258,9
S, spoke hole diameter 2,6
X, cross number (decimal allowed)(optional) 3,00
WL_effective = W - OSB 4,7
WR_effective = W + OSB 46,1

Thanks for any help and/or comments.

I think you are entering something wrong. There is no way the rear wheel will end up with one flange only 4.7 mm from the center. Likewise the 14.7 to start with on the front doesn't sound right.

Even if the rim is offset 10 mm, on the Pugsley the hubs will be offset 17.5 mm.

What hubs are you using?

 

[sryanak]

Thank you.

Rim us a robs'son rim 26' x 80mm. ERD is 548mm and the spoke holes are 20mm from the center of the rim.
Spoke number is 36, 3 crosses.

front hub | Rear hub Nexus 8v
A 28,3 | A 32,2
B 18,1 | B 42,7
OLD 99,8 | OLD 134,5
WL lado disco 21,6 | WL 35,05
WR 31,8 | WR 24,55
s 2,6 | s 2,6
d dl = dr 58 | d dl = dr 92
flange distance 55 | flange distance 55
Nº spokes 36 | Nº spokes 36

My last result are the following:

RearWheel Input Data Output Data
N, total number of spokes 36 cross left length right length
ERD, effective rim diameter 548,0 0 228,7 228,0
OSB, offset spoke bed 0,0 1 231,9 231,3
WL, width from center to left flange 30,0 2 241,1 240,5
WR, width from center to right flange 24,5 3 254,6 254,0
dL, left flange diameter 92,0 4 270,2 269,7
dR, right flange diameter 92,0 3,00 254,6 254,0
S, spoke hole diameter 2,6


Front Wheel Input Data Output Data
N, total number of spokes 36 cross left length right length
ERD, effective rim diameter 548,0 0 244,7 245,8
OSB, offset spoke bed 0,0 1 246,6 247,7
WL, width from center to left flange 21,6 2 252,1 253,2
WR, width from center to right flange 31,8 3 260,3 261,3
dL, left flange diameter 58,0 4 270,0 271,0
dR, right flange diameter 58,0 3,00 260,3 261,3
S, spoke hole diameter 2,6
X, cross number (decimal allowed)(optional) 3,00
WL_effective = W - OSB 21,6
WR_effective = W + OSB 31,8

I am not familier with those rims so don't know if all the spoke holes are offset to the same side or if they are staggered. However before we get there I see a couple of issues:

1. On your list of dimensions for the rear hub you list WL as 35.05 but when you put that number into the spreadsheet it was put in at 30.0.

2. If the rear is on an offset bike, such as the Pugsley, then you have to calculate that offset into the hub, the width from center to left flange should decrease by 17.5 and the width from center to right flange should be increased by 17.5.

3. The rim offset needs to be put into the spreadsheet as well. If it is 20 mm all to one side than put it into the spreadsheet so that it makes the left spokes longer and the right spokes shorter.

If I've missed something or screwed it up I'm sure someone will chime in.

 

[kypa]

thank you for your answers.
My hub is a shimano nexus 8v coaster brake.
All the spoke holes are offset the same distance from the center of the rim.

 

[Frank Z]

I think you are entering something wrong. There is no way the rear wheel will end up with one flange only 4.7 mm from the center. Likewise the 14.7 to start with on the front doesn't sound right.

Even if the rim is offset 10 mm, on the Pugsley the hubs will be offset 17.5 mm.

What hubs are you using?

Thanks for your comment, Sryanak. As you mentioned to kypa, I calculated the offset of 17,5 mm into the hub ("the width from center to left flange should decrease by 17.5 and the width from center to right flange should be increased by 17.5"). As I'm not that proficient with Excell I may have entered wrong WL and WR values for the rear hub (Shimano XT FH-M756 disc) which should be 19,5 resp. 42,2 mm. Spokelengths then will be 255 mm nonDS and 260,1 DS. Offset on the rim is 10 mm, all to one (drive-)side.

If I'm doing something wrong here, please correct me.

 

[sryanak]

Thanks for your comment, Sryanak. As you mentioned to kypa, I calculated the offset of 17,5 mm into the hub ("the width from center to left flange should decrease by 17.5 and the width from center to right flange should be increased by 17.5"). As I'm not that proficient with Excell I may have entered wrong WL and WR values for the rear hub (Shimano XT FH-M756 disc) which should be 19,5 resp. 42,2 mm. Spokelengths then will be 255 mm nonDS and 260,1 DS. Offset on the rim is 10 mm, all to one (drive-)side.

If I'm doing something wrong here, please correct me.

Frank, I think there is still an error somewhere. For your rear wheel, when I enter the data for the M756 hubs into the spoccalc spreadsheet I get spoke lengths of 259.9 l and 260.2 r respectivly using the 19.5 and 42.2 flange spacings and 45 mm diameters (you used 61 mm diameters) It could be that you have a larger flange hub than that listed in the spoke calc database. If yours are really 61 mm then the spoke lengths would be 256.5 and 256.8by my calculations. I think the reason your right and left differ by so much is that you entered the rim offset as a positive on the rear wheel. Put it in negative and it makes the lengths work much better.

For your front wheel, I was able to verify your calculations.

 

[sryanak]

thank you for your answers.
My hub is a shimano nexus 8v coaster brake.
All the spoke holes are offset the same distance from the center of the rim.

Kypa, I'm sorry but I am not coming up with a definitive answer. I can only find slightly conflicting dimensions for the Nexus 8V hub on Sheldon Browns site and a nother Shimano site and they don't really match what you have. The other two are close so if I plug them in I get:

Rear Wheel Input Data Output Data
N, total number of spokes 36 cross left length right length
ERD, effective rim diameter 548.0 0 228.8 227.5
OSB, offset spoke bed -20.0 1 232.1 230.8
WL, wdth frm center to left flange 14.3 2 241.4 240.1
WR, wdth frm cntr to right flange 44.0 3 254.9 253.7
dL, left flange diameter 92.6 4 270.6 269.5
dR, right flange diameter 92.6 3.00 254.9 253.7
S, spoke hole diameter 2.9
X, cross number (decimal allowed)(optional) 3.00
WL_effective = W - OSB 34.3
WR_effective = W + OSB 24.0

So hopefully 254mm spokes would work for both. 254.9 and 253.7 if you could get exact lengths.

As for your front hub.

If you are using a 100mm front hub you can't use a rim with a 20 mm offset. Your hub is starting out with a 21.6 mm left flange spacing. If you offset the rim holes 20 mm left then the spokes go straight up and down. If you flip the rim over you then only get an 11.8 mm offset between the rim holes and the right hub flange and that is still to close given that the other side is now offset 41.6 mm. Could you have the rims redrilled to say a 5 mm offset which would give you spokes of exactly the same length (assuming the 21.6 WL , 31.8 WR and 58 D values are correct. I couldn't find this hub anywhere to verify those numbers)? If those are correct then a 5 mm offset drilled rim gives 260.9 mm spokes on both sides. The additional holes should not compromise rim strength unless it already has a bunch of holes in it.

My last unhelpful question is are you sure about the ERD of 548 that seems pretty big to me but I am not familier with that rim.

 

[Frank Z]

Frank, I think there is still an error somewhere. ...45 mm diameters (you used 61 mm diameters). ... I think the reason your right and left differ by so much is that you entered the rim offset as a positive on the rear wheel. Put it in negative and it makes the lengths work much better.

For your front wheel, I was able to verify your calculations.

:thumbsup: It's exactly as you stated. I can order the spokes now. :yesnod: Thanks alot!