spoke threading question (cracks in rim)

jimmyhackers

jimmyhackers

10 kW
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May 11, 2015
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ive had my rear 1000w 26" hub motor for about 6 or 7 years now....no real problems.

decided to wash it today and ive noticed every other spoke hole in the rim has minor cracks (see pictures)

these cracks i suspect are from the steep angle of the spokes causing the spoke nipples lip/rim to be catty wompus and dig in and malform/destroy one side of the rims spoke hole more, which eventually leads to cracking.

my question is.... would i be better off if i did rerim/respoke this rear motor, to have straight spokes that dont cross each other?
 

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Lets ask our wheel building expert.
Posted by: Chalo,
Search results for query: spoke angle
endless-sphere.com

Search results for query: spoke angle

endless-sphere.com endless-sphere.com

I would start with a plan. Buy new spokes and a rim. Need measurements of rim and motor.

Wheel Building

Wheel Building - Learn

There are many good print and online references for lacing bicycle wheels. Many will defer to Sheldon Brown, Brandt's Bicycle Wheel Book, and others. However, a lot of the points and details with a conventional bicycle hubs don't necessarily apply to hub motors with their much larger flange...
ebikes.ca ebikes.ca

Spoke Calculator

Online Spoke Calculator for Hubmotors and Ebikes

Our handy spoke length calculator allows for easy calculation of spoke length for custom builds - and is the only one of its kind to include paired spoke holes in the flange as is common with many large diameter hub motors. It also creates an automatic side view drawing of the laced wheel and...
ebikes.ca ebikes.ca
 
Spokes that are too thick tend to crack rims. Use 2.0mm or 2.0/1.8mm spokes next time.
 
what im asking about is the bias in force distribution on the rim vs the cracks forming.....ill ty and do a paint sketch to explain.
spoke nipple damage.png
1. is ideal/90 with even distribution round the whole of the nipple.
2. is what i currently have.. where the bias is putting more stress on one side compared to the other, causing it to crack mainly on one side of each nipple hole.
 
Spoke holes in bicycle rims are often drilled straight (perpendicular) when in fact the spoke is applied at an angle.
Which you have identified by asking about radial lacing.
Your pictures appear to show the nipples are not fully collinear to the spoke indicating stress at the spoke hole.
Your drawing does a good job of explaining the fix.
Usually I take a small round file and alter the hole to match the preferred spoke angle.
To reduce stress, debur all rim holes.
An e-bike rim will be thicker in the spoke area.
The rim models with rivets may be stronger but are harder to custom alter.
Personally, I'd go with a spoke cross rather than radial lacing.
Sapim strong spokes would be a good choice.

Rims, like tires and tubes, are consumables items.
They sometimes need to be changed.
 
thanks for the info, im quite read up on wheel building, but couldnt find any material addressing my specfic issue (hence asking)
ive just relaced the same hub motor onto a new 20" bmx rim/wheel. it originally came with radial spokes and ive replaced it with similar. the smaller space meant that cross lacing wasnt really an option. (see picture)
20230315_165310[1].jpg
factoring in this cost me 65 for custom sapim spokes and nipples and 40ish for the rim. A whole new rear motor kit with rim, tube and tyre (plus controller, throttle etc) is 170ish

im not sure if id be better off just getting a whole new wheel and hoping it lasts for another 6 -7 years :D

i suppose my real question is/should of been:
is what i loose strengthwise in going radial over crosslaced, worth the gain of not having angled spoke nipples slowly destroying the rim?
 
jimmyhackers said:
factoring in this cost me 65 for custom sapim spokes and nipples and 40ish for the rim. A whole new rear motor kit with rim, tube and tyre (plus controller, throttle etc) is 170ish
Click to expand...

A whole new prebuilt hub motor wheel is complete garbage 9 times out of 10, too. I would only get one if I needed the hub, and I'd disassemble it and recycle the rim and spokes. That's what quality we're dealing with from Chinese hub motor sellers-- the wheels aren't even worth using up first. They will let you down and they, not you, will choose the time and place to do it.

Use regular 14ga or 14/15ga spokes and they will not cost you $65 for a wheel's worth.

Angled spoke nipples aren't a problem for the rim. That's why their heads are conical or hemispherical. Fat chunky spokes that don't stretch worth a damn are the problem. Cruddy cheap Chinese rims are also a lot more likely to have problems than reputable (not the same as expensive) rims.

DT Swiss Champion or Sapim Leader spokes, plus a suitably beefy rim from Alex, SE, Ryde, heck even Weinmann, will give you a chance at getting long and reliable service from your wheel. Use a janky no-name rim and Lincoln Log spokes, and it won't matter how carefully you build it, it will suck.
 
i found this from sapim.....their polyax spoke nipples
polyax nipple-01.png
the diagram shows a 12 degree angle......and im wondering if thats implying they can cope with upto a 12 degree angle, or more.
im just wondering even if i did have a nicer rim, spokes+spoke nipples, wether the excessive angle a hub motor+26" rim creates would still be too much angle?
atm it seems closer to 15-20 degrees.
 
It looks like the cracked rim doesn’t have eyelets. You may want to have them on the replacement rim, or double eyelets like in the Sapim diagram.
 
The Grin spoke calculator does output spoke angle.
For an eyelet rim the spoke angle will need to stay between 78 ~ 90 degrees.
Only spoke brand / model they offer is Sipam Strong or Sipam E-Strong.
 
lol, the grin spoke calculator for my hub+26" rim gives me a 76.2degrees at 1 cross lace and 67.7 for a 2 cross pattern. both of which exceed the recomended max of 12 (78) degrees.

see what im getting at now maybe? it would appear there is no (in spec) way to use a cross lace pattern with my hub and a 26" rim.

i will probably go with a double eyelet rim and 1 cross lace pattern.
if anyone can recomend some double eyelet 26" rims that allows for a steeper spoke angle than 12 (78), please do.

p.s. found this page.....talks about mismatching hubs to rim hole numbers so you get less spoke angle......but they all seem a compromise too.

Bicycle Wheel Spoking Patterns for Large Hubs

This article describes how to spoke a bicycle wheel with a large hub such as an electic-bike motor, while avoiding excessive spoke angle at the rim.
www.sheldonbrown.com
 
Going from a 26" rim to a 20" 'BMX' rim is not, imo, a good idea (especailly one that is radial laced). I say this because most radial laced rims are for show only. Meanwhile, you are probably running spoke/nipples that are way too thick for your rim/hub combo (as Chalo often says). Meanwhile, the photos you posted very clearly indicate very bad spoke angles. You should have noticed this long before you 'decided to wash' your ebike.
 
jimmyhackers said:
lol, the grin spoke calculator for my hub+26" rim gives me a 76.2degrees at 1 cross lace and 67.7 for a 2 cross pattern. both of which exceed the recommended max of 12 (78) degrees.

see what I'm getting at now maybe? it would appear there is no (in spec) way to use a cross lace pattern with my hub and a 26" rim.

i will probably go with a double eyelet rim and 1 cross lace pattern.
Click to expand...
A spoke nipple that's not collinear to the spoke can break a spoke at the end of the thread.

Radial spoke works fine, there are plenty of successful wheels built that way.
Due to the shorter length a radial pattern allows the least spoke weight.
The gamble with the scheme is : due to the straight pull it puts a higher load on the minimum amount of material on the hub flange.
i.e. more spoke angle means more hub flange material the spoke pulls against.

Think about this : to install a rivet the hole in the rim is actually drilled larger.
With a bigger hole is the rim stronger ?
Don't discount changing the spoke angle at the rim.
It is something I've done on lots of successful wheel builds.
Most recently for a set of custom motorcycle wheels.
Sometimes it's the best answer.
 
FMB42 said:
Going from a 26" rim to a 20" 'BMX' rim is not, imo, a good idea (especailly one that is radial laced). I say this because most radial laced rims are for show only. Meanwhile, you are probably running spoke/nipples that are way too thick for your rim/hub combo (as Chalo often says). Meanwhile, the photos you posted very clearly indicate very bad spoke angles. You should have noticed this long before you 'decided to wash' your ebike.
Click to expand...
Im not sure you read/understood properly.....I have both a 20" wheel bmx ebike and a bigger 26" wheel ebike. both with the same size/power hub motor and 1500w controller.
ive only just relaced the 20" after it being OOA for the past yearish (dented rim lip from flatish tyre+rough ground, not bad spoke holes).
the old 20" rim itself is still perfectly round.
I only posted the pic of the 20incher to show i can lace a wheel semi compentently to avoid patronishing tones.


I half missed the bad angle, because every single 26" 1000w wheel is laced exactly the same, and as somewhat proven by the grin spoke calculator, its impossible to get a good spoke angle and have spokes cross laced.

thanks for the help papasteve, as you can tell, im torn between radial n cross.....as everyone/internet says radial is "terrible" and to avoid it.
I half think most people who had a bad experience with radial.....didn't check spoke tightness after each ride for the first few weeks of riding on new spokes.

Changing/drilling/filing the spoke hole angle on a "naked" rim will still end up with the same problem somewhat.... the spoke will go through nicer but the nipple flange will still not sit evenly on the rim hole edge.....again causing uneven stress on one side of the rim holes.
A larger hole in a double skin rim with double skinned eyelets.....may or may not be stronger (depends what type of strength you mean).....as each eyelet joins the outer skin to the inner for extra overall reinforcement of the rim.
seeing as the strength failure in my current (cheap poo chinese) rim was the eyelet holes and not a malformed "doritoed rim"
i could extrapolate that a resonable quality rim from a reputable brand should be made of better material and be able to cope with larger spoke holes drilled for steel eyelets.

i really could do with a "better design rim" where each spoke hole has been pressed into the right shape/angle (like a motorbike wheel) see pic
14.jpg
dont suppose they do this for bicycle rims?

seems like short of finding the magical "above pictured rim" anything i do choose will end up being a compromise in one area or another :(
 
Last edited:
A craftsman takes raw materials and modifies as needed to create the best solution.
Spoke wheels are pretensioned to create light weight, strong structures.
This inborn tension puts them close to the ultimate failure point.
Keeping an eye on areas of stress risers and quality materials are keys to a lasting build.
In your example I'd say a weak rim is the cause of the cracks not the nipple angle.
This is a recent motorcycle wheel build that required a slight mod to the nipple holes to keep the nipples and spokes collinear.

jigged up wheel.jpeg

As always
Your Results May Vary
 
PaPaSteve said:
A craftsman takes raw materials and modifies as needed to create the best solution.
Spoke wheels are pretensioned to create light weight, strong structures.
This inborn tension puts them close to the ultimate failure point.
Keeping an eye on areas of stress risers and quality materials are keys to a lasting build.
In your example I'd say a weak rim is the cause of the cracks not the nipple angle.
This is a recent motorcycle wheel build that required a slight mod to the nipple holes to keep the nipples and spokes collinear.

View attachment 331450

As always
Your Results May Vary
Click to expand...
Any benefit to using brass or stainless spoke nipple washers? I'm wondering if that help a little with the angles or help a weak rim last longer.

wheelbuildingparts.com

Product categories Sapim|Spoke & Nipple Washers|Spokes

wheelbuildingparts.com wheelbuildingparts.com
 
E-HP said:
Any benefit to using brass or stainless spoke nipple washers? I'm wondering if that help a little with the angles or help a weak rim last longer.
Click to expand...

I use nipple washers often. Today for instance, I was working on a pedicab wheel with one eyelet that was getting uprooted from the rim. I took out that spoke, punched out what was left of the eyelet, and reinstalled the spoke with a 4mm stainless steel flat washer under the nipple head. For that job, I almost always use a flat washer (which often forms into a cone as I tighten the spoke).

Where I use conical washers like the Sapim "HM" type is when I'm using a rim that's drilled for 12ga spokes, or when I'm using a non-eyeleted rim but I need to get the spokes extra tight (like for a pedicab). I can't say they do anything as well as proper eyelets, but they make a non-eyeleted rim work better both for spoke line and for reducing friction at the nipple under high tension.
 
the bias of the cracks on my rim all to one side (the side the nipple digs into) suggests it was the excessive spoke angle.
wether a better naked rim would cope with these uneven forces better, or eventually fail the same way, i guess is up for debate.

spoke washers do seem like a good shout though. im not sure if the conical cup ones will help my excessive spoke angle (sapim doesnt specify maximum angle for them)....but the flat ones should reinforce the area of the rim im having trouble with.

failing that....do they make 26" bicycle rims that have the pressed/formed holes like they do on motorcycle rims?
like in the pics i showed of a motocyl;e rim and papas picture of one too?
 
jimmyhackers said:
the bias of the cracks on my rim all to one side (the side the nipple digs into) suggests it was the excessive spoke angle.
whether a better naked rim would cope with these uneven forces better, or eventually fail the same way, i guess is up for debate.
Click to expand...
Indeed ... The nipples making hard contact on the side of the hole could be the causation of the crack ...
A few strokes to the nipple hole with a round file would have fixed that.
Once the rim is removed cut it apart and measure the material thickness at the nipple holes.
Look for a model with more thickness in that area.

As shown in my motorcycle wheel build, Just because the rim has dimples does not mean it didn't need to be modified to work properly.
Your creating a non-standard custom build.
Finding standard parts that work without some mods may not be possible.
 
A 15% thicker spoke bed allows for super high tension-reliable wheel builds.

Velocity Rim
 
jimmyhackers said:
Im not sure you read/understood properly.....I have both a 20" wheel bmx ebike and a bigger 26" wheel ebike. both with the same size/power hub motor and 1500w controller.
ive only just relaced the 20" after it being OOA for the past yearish (dented rim lip from flatish tyre+rough ground, not bad spoke holes).
the old 20" rim itself is still perfectly round.
I only posted the pic of the 20incher to show i can lace a wheel semi compentently to avoid patronishing tones.


I half missed the bad angle, because every single 26" 1000w wheel is laced exactly the same, and as somewhat proven by the grin spoke calculator, its impossible to get a good spoke angle and have spokes cross laced.

thanks for the help papasteve, as you can tell, im torn between radial n cross.....as everyone/internet says radial is "terrible" and to avoid it.
I half think most people who had a bad experience with radial.....didn't check spoke tightness after each ride for the first few weeks of riding on new spokes.

Changing/drilling/filing the spoke hole angle on a "naked" rim will still end up with the same problem somewhat.... the spoke will go through nicer but the nipple flange will still not sit evenly on the rim hole edge.....again causing uneven stress on one side of the rim holes.
A larger hole in a double skin rim with double skinned eyelets.....may or may not be stronger (depends what type of strength you mean).....as each eyelet joins the outer skin to the inner for extra overall reinforcement of the rim.
seeing as the strength failure in my current (cheap poo chinese) rim was the eyelet holes and not a malformed "doritoed rim"
i could extrapolate that a resonable quality rim from a reputable brand should be made of better material and be able to cope with larger spoke holes drilled for steel eyelets.

i really could do with a "better design rim" where each spoke hole has been pressed into the right shape/angle (like a motorbike wheel) see pic
View attachment 331449
dont suppose they do this for bicycle rims?

seems like short of finding the magical "above pictured rim" anything i do choose will end up being a compromise in one area or another :(
Click to expand...
 
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