Had an experience with a rental bike that raised some questions.

Rental was a road bike. I planned an ~50 mile ride just to see the country. About 15 miles into the ride a spoke on the rear wheel broke. At first I didn't know what happened. But when the brake started dragging I knew.

The LBS wanted me to ride it back. When I told them the wheel was so out of true it still drug when the brake was fully open they sent a van.

-Only broken spoke I've ever had. Best guess why it broke? Safe to ride the road bike? If so, how many can be broken and the bike is still safe?

Sometimes a spoke just breaks. It could have had a manufacturing defect and just let go. Or something could have hit the spoke. I was riding on a trail in June and a large, solid stick jumped up into my wheel and broke a spoke.

Is it safe to ride? Often when one spoke breaks, you just replace it and true up the wheel. Off you go. However if a second or third spoke breaks, well, it might be telling you something.

I mentioned earlier that I had a spoke break in June. I was crossing Missouri on the KATY trail when it happened. I had spare spokes, but wouldn't you know it, it was a spoke behind the cassette and I didn't have a cassette tool. So I widened up the brakes and loosened the spokes on each side of the broke spoke a little. I rode it that was for about 70 miles when a spoke 180° opposite broke. I then rode the bike that way for another 60 miles until I found a bike shop that replaced the spokes in Defiance, Missouri (a great little bike shop). I've ridden that bike since with no issues. BTW: It was a 36-spoke wheel which probably helped matters a lot.

If you break enough that it's unusable, that's pretty safe.

Much of your question deals with what do you mean by "safe"?
Depending on the spoke count, you may be "safe" at any time.
I imagine a very low spoke count wheel could collapse and toss you though, IF you broke a couple? spokes at once.

Spokes break from incidents, poor manufacturing/QC, and from fatigue. I suspect the latter did this spoke in. Rental bikes (like autos) lead a hard life. If the wheel had been treated poorly in the past, then trued/retrued a few times, and used over and over by riders who didn't baby the wheel I can see very easily why a spoke might break with out any other influence.

Wheels with fewer spokes, narrower rims, lots of dish (rear wheels with lots of cogs), poor initial build and follow up tensioning/truing, and big riders who pedal squares all make matters worse. Andy.

This last sentence is why Spinergy's Rev-X wheels left the market place. With only 4 spokes a side it took only one pair to break for the rim to have no support for almost 180*. There are documented incidences of a pedal or QR lever getting snagged up in such a wheel (during group riding/sprints and the adjacent bikes), the spoke fracturing and the rider taking a tumble as the rim leaves it's placement WRT the hub. This is why so many aero carbon spoked wheels used 5 spokes/pairs of spokes.

It was interesting to watch Spinergy go from their Rev-X wheels and marketing claims (of aero advantage being 31) to their Spox (?) designs as being best in only a couple of years. Andy.

Hi,

My best guess for a rental bike is your are the rider that broke a Camels back.
Very likely heavy renters with poor technique give the wheels a real hard time.

Anyone that then comes along that can put some real torque through the
rear wheel can then break a spoke, though it never happens on their bikes.

Best tool for broken spoke is a spoke spanner and loosening the two either side.

How many can be broken and its still safe ? I'd guess 3 or 4 spread
around the wheel for a typical 36 spoke count, easy but very unlikely
on the front, and on the rear at that point IMO you really don't want to
explore how many further spokes you can lose without catastrophic failure.

FWIW with a spoke spanner and knowing what you are doing you could
theoretically lose half of your rear NDS spokes evenly and half of all
your front wheel spokes evenly (with assumptions) still being "safe".

That assumes none are damaged, whist the previous assumes they are.

rgds, sreten.

Wheel destruction aside, if a pedal or QR gets snagged in the spokes of a wheel, chances are the rider is going down just the same.

Alloys have changed a lot in the last 20 years. I've broken a few spokes from years back. It doesn't seem to happen as much these days. Depending on the wheel, sometimes you can adjust the wheel back, close to true, to get you through the ride. On a rental, I'd do what you did. Not a can of worms worth opening

Y'all have mentioned "heavy rider" several times. For a road bike, what is that?

HawkOwl- I hope we haven't accused you of being a heavy rider. I use this label to describe both weight and/or pedaling style. Both are a shade of gray definition. Weight is often thresholded at around 200lbs. But BITD many xlight components were "limited" to less then 175lbs rider weight and some consider above 150 to be more then average (wish I could be in that crowd these days, surpassed that a decade ago). By style I mean how smooth one's pedal stroke is. How much upper body or hip is used to power the bike. How easily one unweights the pedals/seat for shifting or bumps. Often associated with one's average cadence but in my experience not a direct connection. Riding fixed gears and/or rollers helps this "light" manor of pedaling.

As an example of a heavy style but not weight I see many women (Yes, I know I'm entering dangerous waters saying this) with low body weights that pedal slow, can't shift smoothly and don't unweight over bumps. Of course many men do this too but I mention women because they are usually lighter in weight and a heavy style is not dependent on weight.

So if I have insulted you or the many women out there I ask for your understanding. This is a discussion and not a sexist diatribe. Andy.

I actually did once break half of the DS spokes on our tandem when the chain overshifted and sheared off the heads of every other spoke. Since the broken spokes were evenly spaced the wheel remained reasonably true with just a shift of the wheel's dish. We moved the brake over a bit to the NDS side so it didn't rub (also adjusted the limit screw in the RDR and bent the broken spokes so they were out of the way) and continued the ride uneventfully - no need to even get out the spoke wrench.

What a refreshing change it is to see a post that reflects a civilized concern for someone else's feelings. Kudos.

But, in my case, I was just trying to get a frame of reference definition. My personal road bikes are both carbon fibre Versailles and have a manufacturer's stated limit of 275#, if I remember correctly. Hybrids and other flat bar bike's limits go up to 350#. I suppose other manufacturers similar limits. So, to have damage from a "heavy" rider wouldn't the rider need to exceed those limits?

That leaves inadequate maintenance as a cause. Yes?


By the way, at a mid-190s and a low body fat number at the time I sure wasn't a racer body type. But I got by.

Most broken spokes are the result of a poor quality wheel build.
Improper spoke tension on the initial build.
Machine built/trued wheels need a human touch

If the world was digital then any rider less then X weight (and being under the manufacturer's limit) would not wear or load the bike more then a rider of Z weight. But the world does not follow this dream. The world is made of shades of grays. The world is analog. A 100lb rider won't load a bike anywhere near as much as a 250lb one.

Consider the auto that carries only one person compared to the one that is always packed with four and all there baggage. Sure the unibody might not wear out much faster but we all know that the brakes and shocks will wear faster with the heavier load. So why isn't a bike the same, it is the same. The bikes frame might not flex beyond design limits but the parts will have a shorter life. Brake pads will be stopping greater mass, chains and cog teeth will see higher peak and average loads, the clamping systems will have to withstand larger rotating or sliding forces and the spokes will go through a wider range of tension changes.

It should be pretty easy to understand that greater forces means more fatigue and wear. You see it in the shoes of heavy people, in their beds and hear it stressing the floor above you when they walk. Again why is it expected to be different for a bike?

Added to all this is the way a bike can be used, shifted, loaded for the same weight. As my last post tried to say how you load a bike (for whatever weight you are) also contributes to wear and problems. Back to the auto example. We all know that jack rabbit starts, race course like braking and not slowing down for speed bumps shortens a car's life. Why, again, do we think it's any different for a bike??

You do have a point in that inadequate maintenance is a factor. But if that maintenance is also replacing parts (not just "tuning" them) how many will still feel that "its" called maintenance? The auto example again, is it maintenance to replace the tires as they wear? To the car as a whole yes. But to the tires, no. We replaced them, not just checked their air pressure or balance.

So what one calls maintenance another calls repairing. As i said this discussion is full of shades of gray. But what it not at question is that how much we weigh and how we treat the bike during our riding does effect it's function.

In post #13 Bill says "Most broken spokes are the result of a poor quality wheel build.
Improper spoke tension on the initial build.
Machine built/trued wheels need a human touch"

I would say that poorly built wheels let the spoke suffer from fatigue sooner. I do agree that most machine built wheels are not as well tensioned as QUALITY human built wheels. But hand building alone is not god's gift to reliability. Andy.