Broken Pro Connect Rim

[Neil]

Not My day. Got home from work to find my wheel loose. The rim has snapped. I was planning to take it to France on Friday.... oh well

 

[eddieo]

Blimey, was watching the cycling this afternoon on TV and and a girls bike snapped in half...**** happens I guess

 

[flecc]

Sorry to hear this Neil, really bad luck just before travelling. On the few occasions that this sort of break occurs it's usually at the seam since they are made from continuous channel section turned and joined, but that looks more like the metal has fractured through at the weakest point of a spoke nipple hole. Probably the brake pad wear has thinned and weakened the sidewalls enough for it to happen.
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[Dynamic Position]

Its a worrying thought that these fractures can occur. It is just good luck that it happened now than when you are in France. Even better that you were not cycling when it hapened as it could have led to much more serious consequences! How many miles did you get from the wheel before it failed?

 

[Neil]

The bike has done 9100 miles. When I bought the bike I asked the question is this bike suitable to do 120 miles a week and 50 cycles said yes. The wheel is the original low spoke one (you can't get replacements) so will need a new hub or a second hand wheel. The bike is coming up to its being 2 years old.

 

[flecc]

That's a good mileage on an alloy rim used daily in varying conditions Neil. One of the pains of the change from steel to alloy rims has been the need for regular rim renewal to cope with rim brake wear, but at least we can stop in the rain, something very difficult to achieve with steel rims!

Steel rims that last for ever are still made if someone doesn't mind being unable to stop in the wet, here's one manufacturer:

Sunjourney Steel Rims

The last one is suitable for your bike.
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[HarryB]

You did well to get 9100 miles - I got 1400 out of the first rim on my Cytronex Trek. If I had a rim braked bike again I would consider getting them converted to ceramic. I wonder if there is a significant advantage in wear rates for the extra costs. Otherwise I found the Magura hydraulic brakes seem to be kinder on rims than the most.

 

[Neil]

Had A better look

Toke the Tire and tube off. Noticed I had two Brakes in the rim. One where the valve hole is an one directly opposite. I guess one went first causing the other to fail. Lucky no accidents caused. The rim has not warn through. I attach a cross section of the broken rim.

 

[flecc]

The killer of alloy rims is the same as that for chains, the fine grit particulates in the air and road muck that gets into chains and onto rim walls. The latter embeds into brake pads when the brakes are applied and from then on the pads are a grinding medium to pare alloy from the rims every time brakes are used.

I use my bikes for years without rim changes with these measures:

I always try to avoid braking, letting the bike have it's head downhills and using the kinetic energy to propel me after the foot of the downhill.

Planning ahead for traffic helps me to avoid brake use

Although I hardly ever clean my bikes, I do very regularly wipe the rim walls with solvent cleaners.

At the slightest sign of any scraping sound from a brake I remove the pads, wash the rim walls and fit new pads. It's a waste of time trying to clean pads once contaminated so I keep new spares in stock always.

Of course all these aren't practical for daily commuters, especially when riding in heavy traffic conditions, so I sympathise with them. Best e-bikes for the simplest dealing with rim wear in such conditions are those using the centre motors from Yamaha, Panasonic or SunStar with derailleurs, since they can have instant complete wheel changes from about £30 each, unlike e-bikes with hub motors and hub gears.
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[flecc]

Toke the Tire and tube off. Noticed I had two Brakes in the rim. One where the valve hole is an one directly opposite. I guess one went first causing the other to fail. Lucky no accidents caused. The rim has not warn through. I attach a cross section of the broken rim.

That's certainly not caused by wear Neil, it's very low wear for that mileage. Could there have been any shock damage such as from pothole at any time? If not, it could be that a slight imperfection in the rim material coinciding with the valvehole, coupled with the added metal fatigue over time caused it to fail.
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[Dynamic Position]

The bike has done 9100 miles. When I bought the bike I asked the question is this bike suitable to do 120 miles a week and 50 cycles said yes. The wheel is the original low spoke one (you can't get replacements) so will need a new hub or a second hand wheel. The bike is coming up to its being 2 years old.

High mileage does not always imply high wear and tear. Given you bike is still under two years old the wheel should be covered by the warranty if wear and tear can be ruled out? Don't throw away the faulty wheel as it could provide the evidence for or against fair wear and tear or imperfection.

 

[Neil]

No Pothole Damage

I went to work by my usual route, I know all the pot holes by now and can't remember hitting any on the way. I have spent a lot of love and attention to this wheel. It has had over its life 9 spokes replaced (7 Radial one drive side).

 

[flecc]

I cant help feeling that you won't suffer this experience again with a 36 spoked wheel Neil. I was very critical of the choice of the 24 spoke on e-bikes in general and your model in particular when it first appeared and had some arguments in here about it. Fortunately Kalkhoff quickly adopted the same view and changed it.
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[Neil]

Good news

Contacted 50 cycles today and

"Wow. that is a mess, haven't seen a rim break that for a while.
What model pro connect is it? I'll get a replacement wheel out for you" Jim

So let hope It will arrive in time to take it on a well earned Holiday.