Building a super strong rear wheel
 

I have a canadian tire schwinn Izip, which is basically a Currie Ezip that Dorel Canada has stamped their own name on.

I have less than 1000 kms of commuting on it, and I noticed that there are 4 spokes broken on the rear wheel they are all right next to each other and broke at the hub, not the rim.

When I took it to the local bike shop, they told me that the spokes were already the strongest spokes that you can get, and they didn't seem optimistic that a different rim would help.

Has anyone had their rear wheel rebuild with specialty parts that make it super strong? what parts did you use?

There is a local bike shop in town that is also a good motorcycle shop, I'm thinking that the 2 shops can collaberate to make an extra strong wheel for me, but I am curious if someone can recommend their build?

thanks in advance.

TS

did the spokes snap on the drive side or the non-drive side?
snapping at the hub side usually means spoke metal fatigue, which leads to not enough spoke tension when the wheel was first built up.

I'd recommend having the wheel rebuilt with 2.0/1.8/2.0mm double butted spokes and brass nipples.
and if the wheel builder can do it, tie solder the non drive side spokes.

Doing some googling but can't determine which bike it is that you have. Post a pic or a link to a pic. We need to know more about the wheel and the drive assembly to be able to say something specific.

That's where they usually break. Which side, drive side or non-drive side?

Strong in everyday terms is too fuzzy when you get down to detailed engineering questions. Since your spokes held up in the beginning the issue you're dealing with is fatigue - not "strength". When it comes to pure pulling power spokes are just about always more than strong enough. Nipples and rims tends to fail way before the spoke is torn apart.

If most characteristics of you, your bike and your riding are "average", then it's unlikely that it's the rim that's at fault.
What could happen though is if you have a rim that has a bad low spot, then the builder might have prioritized roundness above spoke tension. This can leave you with a group of spokes that are badly undertensioned, and they will fail due to fatigue rather rapidly. In this situation replacing the rim would help. What you need in that case isn't a stronger rim, but merely a rounder one.

Sure, but unless there's something "special" about the rest of the situation there's usually an easier fix to the problem. Most rear wheel issues is down to build quality rather than parts quality.
If your issue is fatigue related, then tension, tension and tension are the most important keywords. There is a bunch of tricks that can be used, but we need to kow more about the drivetrain and the wheel to be able to say which can be used by you.
Is it a stock hub?
How many spokes?
how many crosses?
what gauges?
how is the drive arranged?

What do you mean by "strong"? capable of taking endless mileage or capable of carrying huge loads w/o buckling? These two are kinda mutually exclusive.

Well I'm not saying it's impossible, but it'd probably be hopelessly expensive. A bicycle hub can't be drilled for motorcycle spokes, the flanges aren't big enough. There's nothing preventing a good metal fabricator from replacing the flanges, which'd immediately leave you with the issue of finding a rim that could be redrilled to take the thicker nipples. There are probably wide section DH rims that are meaty enough for such a procedure, but unless there's something extreme that you aren't telling us about your riding situation you really shouldn't need it to get a functional wheel.

My money is on a poor build quality. Get the wheel rebuilt to the proper spoke tension. If there's problem with the rim it should surface then and if needed you can have it replaced.

I agree with dabac.

A tension spoked bicycle wheel has 4 components: hub, spokes, rim and build quality. The typical 32 spoke 3 cross wheel, when well constructed, is so reliable that manufacturers are generally looking for ways to make it lighter rather than to make it stronger.

Along with the other posters I agree that the problem lies with build quality rather than parts choice. The wheel would have had insufficient tension and unequal tensions. Those two things are the biggest factors in the longevity of a wheel and they are both as equal.

Machine-built wheels (as are on your bike) are notorious for poorly tensioned wheels. This leads to early metal fatigue.

2.0/1.8/2.0mm gauge of spoke will be ideal and will also absorb shock loads better than a 2.0mm plain gauge spoke and thus will give a wheel that can absorb better. Spokes like DT Competition and Sapim Race are ideal and very high quality.

Find a good wheelbuilder and get them to re-build with new spokes. Of course finding a wheelbuilder is easy but finding a good one is a lot harder. You could even do it yourself and with the correct information you could do a better job than a poor "wheelbuilder".

Read my wheelbuilding tips and you will gain the knowledge for what is needed in a search for a good builder or for doing the job yourself. The link to Roger Musson's wheelbuilding e-book at the end of my info would be the best click you could place.

Agreed. Unless this is a low spoke count wheel (doubtful from Canadian Tire) your spokes and rim are likely more than adequate strength. Fatigue failure of spokes is almost exclusively due to low spoke tension, and I suspect a Canadian Tire bike would have machine-built wheels and probably not retensioned since they left the factory.

AT this point my recommendation would be to tear the wheel down and rebuild it with all new spokes. Make sure the rim is not damaged, as this would be the ideal time to replace it if it is. If the rim (or hub) is damaged, you may wish to consider a replacement wheel, preferably built, or at least retensioned by your LBS staff.

The DT Swiss Alpine III spokes are triple butted and thicker at the hub end, 2.34-1.8-2.0. I don't know if they are compatible with your hub though. http://www.dtswiss.com/getdoc/02e74b...Datasheet.aspx

And I agree with the others, your spoke failure sounds like insufficient tension.

Al

I'd like to thank everyone for their help and support.

I took the wheel to a specialty shop today, and I'm having them hand build the wheel with a new set of spokes and a double walled deep V rim that is rated for riders that like to take lots of jumps. My hub is a custom hub that has a sprocket on one side, and a 7 sprocket gear set on the other side, so it will be the only thing that will remain the same.

At the end of the day, I'll have spend about $200 but I'm commited to making are really good wheel.

I am totally ok with the possibility that this is all a waste of money, and maybe 4 new spokes and a retensioning would have sufficed. I'm expecting to be happy with my new wheel regardless.

Just to add a bit there... failure to stress relieve, or not correcting the spoke line will cause fatigue failures just as quickly. Just sayin, it's not always about low tension.

I'm thinking it won't be a waste of money.

Yeah, I've seen this happen before. I agree with all who say it's the build. My friend's rear wheel broke a few spokes, and she had the hack LBS replace them...and then even more broke than the first time, etc., etc. When she showed me the wheel, lots (10 or so) of spokes were broken. I took the wheel and rebuilt it (reusing rim and hub) with new DT 14/15/14 spokes. She paid me back the $40 for the two boxes of spokes and in brownie points for the labor. She's ridden the rebuilt wheel for over a year now with no complaints. :)

Build is super important.

Sounds like you have your problem solved, now can we get a photo of that hub?

I don't have a photo of my hub, but I was able to find this pic on google. but
It is definitely the same as my hub.

I'm sorry for the lack of views. What you are seeing is the left side of the rear hub, on the right side there is a 7 sprocket gear set for human powered riding.

here's another view, but this guy has modified the electric bracket to accomodate 2 motors. The stock bikes only have 1 motor. In fact, I was shocked to see this. Its not something that I've seen before.

my invoice says "New DT Swiss Spokes 2.0 Silver Lace to new 721"

does that give you any indication of what he sold me?

edit: looks like DT Swiss spokes and a Mavic 721 downhill mtnbike rim

is it any good?

It should be fine. Would've been better to get double-butted spokes or the triple-butted ones Al1943 mentioned.


If you are using an electric motor to drive the bike, that's definitely a contributor to the broken spokes.

What's the HP-rating of the motor?
What's the gearing-ratio?
How is the throttle controlled?
Is it linked to the brakes?

Ther are any number of small reasons that might make it impossible, but a hub much like that could easily be put together by taking a stock disc brake (free)hub and then putting a tomicog (a special sprocket) in place of the brake rotor. Lace to a rim with with brake surfaces and you're good to go.

That's a very neat way of putting it:thumb:

thanks. 450W motor, I think my legs can deliver 600W but only for a short sprint. i would decribe my legs as 150W continous output. the motor adds an extra 5 mph to my speed, and provides me with a much wider range of comfotable cruising speed

the throttle is a twist grip, and the brake levers have a cut out switch which is so popular that it is considered a manditory safety feature in many areas of north america.

gear ratio, its a fixed gear as a dc motor can deliver a fair amount of torque even when it isn't at an efficient operating speed. the ratio reduces the 3000 rpm t0 about 260 rpm. (i think)

you might consider a rear wheel from a tandem bike. I hear they are wicked strong w/ 46 spokes cuz they're built to hold up 2 people!

that's either a 40 or 48 spoke.
spoke count is always a multiple of 4, not including 18h.

or, 21 and 27 on the rear.

or, 22 and 26 on the front.