Precise crack or join in aluminum wheel rim?

ao77

I'm trying to decide if I have a problem with a crack / break in my front wheel or if it is a join (or something else). There was a previous post on these forums but unfortunately the pictures are unavailable.

About 10 days ago I had a front wheel flat tyre and had to change the inner tube by the roadside.

On the way home I heard some sort of fluttering sound when I used the front break but stopping performance was fine. I thought maybe there was something caught in the wheel arch or some sort of sloppy repair.

When I got home and did a close inspection I noticed a sort of precise, even ridge on one side of the front rim, on the breaking track, in the same orientation as the spokes. It is easily visible and easily felt with fingertips; I'd estimate a step of 1 mm or less.

(There is another similar marking on the rim but it is only visible, no 3D ridge, can't feel anything with fingertips. I'm assuming this one is irrelevant.)

I hadn't noticed this before nor had the noise been there. There isn't something similar on the other side of the front wheel, nor on the rear wheel. I have my previous set of wheels which are the same specification and there isn't anything similar on them.

I replaced both my aluminum rim break wheels in May 2021 and they have done about 3,000 miles, less than half of what I did in the previous pair (same spec).

It is a Kinlin rim.

Why has it just become noticeable? Is this anything to worry about?

pinkbikini

Hmm- looks a bit dodgy. All alu rims have a join, but you can usually see the join all the way round on both sides and it’s pretty subtle (or non- existent) on the actual braking rim. Doesn’t cause a brake noise.

If the previous flat was a pinch flat then possibly some rim damage. Is the wheel stil true?

It could just be that the rims are a bit cheap and not well finished, therefore nothing to worry about. But I’d take it to a bike shop/ mechanic to take a look to be safe.

imposter2.0

It's where the rim is joined, so nothing to worry about. Manufacturers usually place the rim decal over the join, which is where yours happens to be. Carry on riding.

imposter2.0

Also - 'brake' - not 'break'

andrew_s-2

The join is almost always opposite the valve hole, so the internal sleeve or pins can be balanced by the weight of the valve.
The rim is under quite a lot of compression because of spoke tension, so the crack won't open up.
If you keep riding, the brake blocks will eventually wear the step in the rim smooth and the noise will go away. Before rim braking surfaces were machined smooth, such braking noises used to be commonplace for the first 500 miles or so.

ugo.santalucia

the joint has a sleeve inside, so the rim won't come apart, even if the joint itself doesn't look perfect... it will probably judder a bit when you brake and at worst eat your brake pads faster, but other than that, there is nothing to worry about

First.Aspect

imposter2.0 said:

Also - 'brake' - not 'break'

That's grate.

Imposter should have a capital "I". Glad to be of help.

masjer

I agree with the above about not being much of a concern but, is it possible the brake track has been bent outwards (by unlucky positioning of tyre lever) when fixing the puncture.
It should be possible to bend back and using emery cloth sand flat the joint. Or better still, use a Garryflex abrasive rubber.

pinkbikini

Yeah, ignore my concern - now I’ve zoomed in I can see the join in the non-rim part of the wheel too, so it’s the manufactured design.

Quite possibly unlucky tyre lever positioning when fixing puncture, as mentioned above, has caused it to flex a bit.

Slightly annoying but not dangerous!

ao77

Thanks for the replies.

I am continuing to use the wheel.

One of the people I cycle with thought that the rim was one piece of metal and the crack might propagate. I don't have a good understanding of the engineering of the rim; if it's one piece of metal and the join has cracked that sounds serious.

I had thought the crack might be in the braking (!) track and the rim itself would be unaffected. He also suggested taking a look at the rim from the inside, which I've done and taken some photos and a 30 second video.

https://photos.app.goo.gl/BCeWaRKzWE7spCRSA

I've added some additional information in response to the posts.

pinkbikini said:

If the previous flat was a pinch flat then possibly some rim damage. Is the wheel stil true?

It could just be that the rims are a bit cheap and not well finished, therefore nothing to worry about. But I’d take it to a bike shop/ mechanic to take a look to be safe.

I think the flat was caused by going over roughly finished tarmac at speed. I think the valve on the (unbranded) tube failed as it wouldn't take any air when I tried to locate the position of the leak so as to remove any sharp object.

The pair of wheels were £350 in April of this year.

masjer

Thanks for the update.
The rim isn't cracked, it's just the join.
The rim starts as a flat piece which is then bent into a hoop, trimmed, then either welded (in which case it's harder to see the join) or it's pinned/sleeved (which leaves a visible join).
One thing to check is the brake track isn't too worn. They either have a wear marker or check the thickness isn't less than 1mm.

Ben6899

ao77 said:

One of the people I cycle with thought that the rim was one piece of metal…

Keen to know about whatever wizard manufacturing processes this person knows about!

First.Aspect

Ben6899 said:

ao77 said:

One of the people I cycle with thought that the rim was one piece of metal…

Keen to know about whatever wizard manufacturing processes this person knows about!

In fairness, it is one piece of metal.

Ben6899

First.Aspect said:

Ben6899 said:

ao77 said:

One of the people I cycle with thought that the rim was one piece of metal…

Keen to know about whatever wizard manufacturing processes this person knows about!

In fairness, it is one piece of metal.

We both know what they meant; no joint.