Steel wheel for hub motor ebike?

[zeddrick]

Would there be any reliability/strength advantage in using a steel wheel over a regular alloy one for a direct drive hub motor? I wouldn't be concerned with the extra weight. It seems like all DIY hub kits come with cheap 12g spokes that don't work well with alloy bike rims because they require more tension than the alloy rim is made for. So I was thinking that maybe a stronger steel bicycle wheel would be better suited for short 12g spokes because the steel should be able to handle higher tension right?

I've had my 1200w ebikeling direct drive kit for a few years now and it started snapping the original 12g spokes around the 3k mile mark, afterwards I got custom cut 14g butted spokes from ebikes.ca and rebuilt the wheel with those but after about 2.5k more miles I had one of these new spokes break on me. So now I'm just looking at how I can affordably make a super reliable DD hub wheel setup. I'm constantly worried about spokes breaking now.

 

[amberwolf]

The steel rim has no advantage over the alloy rim, other than probably being cheaper. I went that route once...made things worse.

Just use the right rim for your loads/usage/road-conditions, and the right size spokes for your rim, with the proper tension, and the wheel should last a very long time, short of stresses that exceed it's capabilities like collisions and such.

What are your loads (weight, cargo, etc), usage scenario(s), and road conditions? Those may affect recommendations for the right rim for the job.

What rims were used on each of the failed wheels? (to know what you may want to avoid, or improve upon)


If you haven't done so in each case, you also have to replace the rim when the spokes are breaking because of too-high a tension, as the rim damage is what is causing them to loosen and then break (at the elbow, usually). Once the rim has even a tiny crack or deformation at the nipple hole, etc., it's not going to hold spoke tension there correctly, and it or other spokes may loosen, and failures may begin.



Usually you can just use single-butted 14-15 Sapim or DT Swiss, etc.; you can get them from a number of places online, or your local bike shop if you have one. If you have to you could use 13/14 single butted; I use that size in my SB Cruiser heavy cargo trike without spoke or rim nipple hole problems, even when I have hit potholes that crushed the rim edge, or broken the motor axle.

I've only had one wheel failure on that trike, with spoke issues, and it was an OEM A2B Metro wheel I didn't build or rework when I got it (I should have)--it snapped almost half the spokes in one big BANG for no obvious reason.

The ones I built with good eyeletted rims and properly-thin spokes haven't failed.


In case you need the info, the forum has various wheelbuilding and repair threads (a search on "spoke" or "spokes" along with "rim" or "rims" will find many of them), in some of which there are links to various places, including spoke calculators, etc., to ensure you get the right parts to build a good wheel, and links to places that show how to build them as well.

 

[CONSIDERABLE SHOUTING]

Chalo has had some great comments on spokes and what makes wheels truly strong.

You're suffering the same problems and discussions as what we have in the car world over and over again- steel wheels exist and will always exist, just because they're cheap. They really aren't much stronger than aluminum in function because the physical method of pouring and casting to keep a structured "grain" in the metal still matters- aluminum can easily be made much stronger than steel thanks to thickening of load-bearing regions and still be lighter, which is why steel wheels on cars never look different or unique until you're looking at off-road tires.

I would look to getting good, name brand spokes and checking if you need a thicker sidewall on your tires to absorb more impacts.

 

[Chalo]

Steel bicycle rims are not just heavier than aluminum rims-- they're also much weaker on average because they're rolled out of sheet metal. You can't make forms like that out of high strength steel unless you use a multi step process that includes annealing and subsequent heat treatment (which nobody does because it would nullify the cost advantage of steel rims).

Most steel rims pucker at lower spoke tension than aluminum rims will tolerate. There's not a single way in which steel rims are an improvement over aluminum ones. In addition to being heavier and weaker, they also provide an inferior braking surface, are lumpy and uneven, and tend to damage spoke nipples with their sharp edged holes.

You're best off using the strongest aluminum rims you can get your hands on (not the cheapest one you can find like Ebikeling and other motor kit sellers use). Then use 14-15ga butted spokes if you can get the right length, or straight 14ga if you can't. 13-14ga butted spokes are okay too, but are only beneficial if they allow you to avoid using spoke head washers.

No matter what spokes you're using, you have to build the wheel correctly to prevent spoke breakage. This includes using spoke head washers if the hub holes are too large, using a lacing pattern that allows spokes to maintain a straight line all the way through the nipples, and stress relieving the spokes at the time you build the wheel. There are plenty of ways to get it wrong that don't have anything to do with the quality of spokes or rim. Then after all these factors are accounted for, you have to get the tension high enough that normal loads won't make them go slack at any time.

Check out a copy of Jobst Brandt's The Bicycle Wheel and read it. The instructions in there will walk you through a correct wheel build, but the background information will help you understand why you're doing it that way.

 

[red]

You're best off using the strongest aluminum rims you can get your hands on (not the cheapest one you can find like Ebikeling and other motor kit sellers use). Then use 14-15ga butted spokes if you can get the right length, or straight 14ga if you can't. 13-14ga butted spokes are okay too, but are only beneficial if they allow you to avoid using spoke head washers.
No matter what spokes you're using, you have to build the wheel correctly to prevent spoke breakage. This includes using spoke head washers if the hub holes are too large, using a lacing pattern that allows spokes to maintain a straight line all the way through the nipples, and stress relieving the spokes at the time you build the wheel.

Zeddcick,

I agree with Chalo. Start with a strong, high quality rim first. You may need heavier gauge spokes, and in any case, with rim washers between the rim and spoke nipple.

 

[Chalo]

, and in any case, with rim washers between the rim and spoke nipple.

This is sound advice for rims without eyelets or those that are eyeleted oversize for thick spokes. Rims with eyelets don't benefit from nipple washers, since the eyelets are basically built-in washers.

 

[amberwolf]

I agree with Chalo. Start with a strong, high quality rim first. You may need heavier gauge spokes, and in any case, with rim washers between the rim and spoke nipple.

I think you mean thinner gauge spokes?

Heavier than 12g will require much stronger (and more expensive) rims, or moped/motorcycle rims instead of bicycle rims, to be able to properly tension them without eventual rim damage.