Modern rims crack at spoke holes

[ichitan]

Recently, I was in one of the local bike shops. Someone had brought a bike back to have the back wheel re-trued. There were actually cracks in the rim, originating from the spoke holes.

I have had the same problem with my bike.

In past decades you could buy a bike, and the wheels were strong. With modern rims, the aluminum is getting thinner and thinner. Now the rims crack.

With heavy riders, and people riding on rough tracks, rims may crack in a fairly short time. With lighter riders, they may take much longer to crack. They may not crack on bikes which are only ridden for short distances on rare occasions.

Shimano has had to have a huge recall for selling faulty cranks. I wonder if there will ever be repercussions for rim, or wheel, or bike manufacturers, over faulty wheels.

https://forums.bikeride.com/thread-8594.html.

The response everybody gives is, buy an expensive bike or expensive wheels. The wheels on many expensive bikes are the same, and will crack the same. Don't just buy any wheels, do your research and buy wheels that are stronger.

In the past, you could buy a cheap bike, and the wheels were strong. Bikes should not have parts designed to fail.

My suggestion to people wanting to buy a bike, is buy a used older bike. They are stronger.

   

   

   

[ReapThaWhirlwind]

Rim cracks are still mysterious to me.

I never had to deal with one yet, but I would imagine it's due to poor maintenance and truing schematic over years in most cases, rather than the material. When you take your wheel to bike shops to have them trued, often they will only true them lateral and will not true them radial. Overtime, this would cause the wheel to become crazy tension webbed. Where wheels will already have certain spokes with a little more tension than others—this becomes accentuated terribly—and the strain on that part of the rim will increase exponentially.

If you really wanted to narrow it down to quality, you would need to know the brand of the bike for a better idea of what the cost of production likely was (and thus, the range of quality in the materials used/purchased). I honestly don't find that top companies use any components at all that are low quality. The rims are always very strong, double walled, 6061 T6 aluminum. The larger the wheel, more prone it becomes to flex, because of the distance factor involved. Even so, it's not easy to bust a double wall high grade aluminum rim this way. One should always consider sabotage in these cases also, where a person vandalizes their own components in attempts to cash in on any warranty benefits.

[ichitan]

(11-07-2023, 03:50 PM)ReapThaWhirlwind Wrote:  Rim cracks are still mysterious to me.

I never had to deal with one yet

How new are the bikes you ride? I have only experienced this with bikes that were new in the last couple of years. If you are riding older bikes, I would not expect rim cracks.

Not all rims are equal. There are many stronger rims. There are also many of weak rims.

[ReapThaWhirlwind]

(11-08-2023, 06:54 AM)ichitan Wrote:  

(11-07-2023, 03:50 PM)ReapThaWhirlwind Wrote:  Rim cracks are still mysterious to me.

I never had to deal with one yet

How new are the bikes you ride? I have only experienced this with bikes that were new in the last couple of years. If you are riding older bikes, I would not expect rim cracks.

Not all rims are equal. There are many stronger rims. There are also many of weak rims.

I rode Mongoose and Hyper big box bikes for years. They have general grade aluminium single wall rims. Never seen a crack, but saw quite a few broken spokes on the rear drive side wheel (from machine built under-tensioned spokes). I've had over tensioned wheels where indents were left in the spoke holes, but no signs of beginning to crack. I've built a dozen wheels on new rims. The metal is so strong and rigid from having no weathering. Older rims will still be good and usable, but the metal becomes more flexible as it ages and weathers; especially if it still has old spokes lacing it together. Today's manufacturing has become so good, cheap quality parts can only really be seen where metals are competing against one another; such as with tools or with threading. Even with today's manufacturing, steel screws can still strip out aluminum threads fairly easily.

[ichitan]

If you look at the picture, which is zoomed in a long way, the spoke is 2 mm thick. Compare the thickness of the rim where it is cracked. How thick is it?

These rims are designed to fail.

   

[ReapThaWhirlwind]

It might also be helpful to consider that wheels built on machines use spokes that are longer than hand-built wheels.

I honestly have no idea how that works, but it does result in a crazy tension web eventually; where all the spokes will be tightened all the way to the nipple heads. Some will turn incredibly easy and some will be incredibly tight. That's very bad wheel schematics.

With spokes the proper length, the nipple will fail long before the rim ever could. It will pop from the threads from overtension.

[ichitan]

Here are some videos on wheel assembling and truing machines.

https://forums.bikeride.com/thread-8683.html