The use of 12 gauge spokes on most hub motors

[hillslayer@]

I realize most on this forum believe that all bike wheels should be laced with 14 g spokes , but the fact's are most hub motor bikes are using 12 gauge spokes and I am not seeing a massive amount of wheel failures that you would think would be happening. If it was then those wheels wouldn't be on new bikes. Most consumers probably never even look at wheels until something obvious is wrong. So maybe 12 g spokes are not totally unusable.

 

[Chalo]

They don't stay true. They don't stay tight. Inspect any such bike that's had a few miles and you can confirm this. If you turn them up enough to stay true and tight, they pucker or crack the rims. So in the same way as all department store garbage bikes sort-of appear to sort-of work, yes you can sort of use the wrong spokes and get away with it. But if you like your stuff to work well and stay that way, you will use the correct spokes for the job.

Day before yesterday, I built up a nice coaster brake wheel to improve a fixie bike. After sifting through I don't know how many donated and subsequently scrambled spokes, I came up with 28 14-17ga spokes of the right length and built a wheel on a cast-off Velocity Blunt SL rim. The future buyer will never know how nice a wheel that is. They'll only know they don't have to mess with it because it's just fine.

 

[E-HP]

They don't stay true. They don't stay tight.

On my first kit hub, I had to tighten spokes every 500 miles or so, and the rim went out of true over time, but in radially.
I laced my current wheel with 12/13 spokes, because I didn’t want to use washers, but even thats been ok (but I’d go with straight 14 with washers next time). It took me a while to get everything tensioned correctly, since it was my first time, but haven’t had to make any adjustments for 2 years now.

 

[amberwolf]

I realize most on this forum believe that all bike wheels should be laced with 14 g spokes

No, just the ones with rims designed for those (which is most of the bicycle rims).

If you use rims designed for the tension requirements of 12g spokes, you can use those safely.

If you use rims designed for 10g or even thicker spokes, you can use those safely.


No real way to know how many wheels using 12g spokes are on rims that are designed for them, vs ones that just happen to be strong enough to handle the tension under the usage scenarios they see, vs those that can handle it for a while, vs ones that simply can't do it even from the beginning.


Regarding failure statistics, remember that most people that have problems (of any kind, with anything) don't communicate that anywhere--they just replace the thing that fails. (A few will fix it or have it fixed, but most find that inconvenient or not cost effective, or don't even know that they *can* fix/have it fixed).

Only a small percentage of problems get discussed at all, and only a small percentage of that is done on the internet, and only some of that is on forums where posts about these issues will be retained over time (so they can be found in searches).

 

[hillslayer@]

No real way to know how many wheels using 12g spokes are on rims that are designed for them, vs ones that just happen to be strong enough to handle the tension under the usage scenarios they see, vs those that can handle it for a while, vs ones that simply can't do it even from the beginning.

So it could be maybe wheels that come with hub motors are actually designed for 12 g spokes that might be why there aren't massive failure rates.

 

[Chalo]

So it could be maybe wheels that come with hub motors are actually designed for 12 g spokes that might be why there aren't massive failure rates.

If that were true, they'd have motorcycle/moped rims. But they use bicycle rims, and I've never come across one of those rated for more than 1400N per spoke.

The downside of moto and moped rims is that they're pig heavy and don't seat bicycle tires well.

 

[amberwolf]

So it could be maybe wheels that come with hub motors are actually designed for 12 g spokes that might be why there aren't massive failure rates.

I don't think so.

If that were the case, we wouldn't see the problems with hubmotor wheels that we do, that are caused by spokes too thick for the rims, breaking them from the tension required to make them function as tensioned-spoke-wheels.

As previously noted, it's not possible to find out what the actual failure rates are.

 

[markglos]

My first hub motor (cheap 1500w) came with 13g spokes in a 26" mtb rim, the spokes broke constantly and in the end so did the rim. Replaced the rim with another no name 26" but this time used 14g and never had another issue with that wheel until I eventually overheated the windings.
Seems like my experience is very similar to lots of others so personally I'd stick to 14g on mtb rims.

The only time id use 12g is like i did last month when i built up a Mxus 3k motor with 12g spokes in a 17" moped rim as I wanted a wheel strong enough to cope with heavy weights and high speeds. The big tradeoff though is the weight.

 

[Sturmey]

I notice in this discussion that its not clear whether we are talking about front or rear hubs. I find there is a difference. Nearly all spoke problems (12g & 13g) I have dealt with have been on rear hubs. The only problem I have have seen on front hubs were spokes clicking at crossover that was cured by tightening the nipples. The last few kits I have fitted (from pswpower) do not lap the spokes (leave a gap at crossover (2x). All kits I have fitted so far needed some re-tightening. The rear especially have needed several re-tightenings.

 

[amberwolf]

Most mechanical failures will accelerate the more cyclic loading there is on the stress points, so more rear wheel failures are expected than front, as those are more lightly loaded and see less stress during the cyclic loading as they rotate than the rears do, for most bike (and trike) designs.

 

[hillslayer@]

Ok been running a Chinese CSC 1500 watt hub with a mid-drive running full power up hills often packing and extra 50 lbs , besides an occasional loose spoke it's holding up really good, cruising at 30 mph plus mostly. 12 gauge spokes might be alright.

 

[Chalo]

besides an occasional loose spoke

Yes, that's the problem. Not only does that make your wheel go out of true, but a loose spoke is the same as an absent spoke in terms of it being able to support the wheel's structure.

 

[amberwolf]

besides an occasional loose spoke

And it means that your spokes are continually loosening. (if they weren't, you wouldn't have this problem)

That happens when too-thick spokes are used for the given rim so they pull too hard on the rim and the rim deforms or cracks, reducing tension on the spoke, spokes never fully tensioned, etc., as previously discussed in numerous threads (including a previous one you'd participated in).

It's ok if you don't agree, but if you want the problem to stop, you have to fix the cause.

 

[hillslayer@]

It's not a problem wheel is staying true. Even with big loads and massive torque to it.