Rim Thickness

[User]

 

[raleighnut]

Rims used to be a lot thicker, especially single skin (unchambered) ones. Once they started extruding 'double wall' profiles to put strength into low spoke count wheels they discovered that you could reduce the wall thickness without weakening the wheel. the downside for us is they wear out faster but for manufacturers it's a 'win,win' situation, we just have to replace them sooner.

 

[Ajax Bay]

[QUOTE 5078866, member: 9609"]I am measuring it at between 1.7 & 1.8mm. which seems thick enough. . . .the new rim I bought last year . . was only something like 1.6 thick, and the one that replaced was down to 0.94mm[/QUOTE]
How did you measure these thicknesses? Dental calipers? What is the front rim? It looks fine to me btw. Many of these older ones don't have a wear indication groove to offer visual confidence. Before I had my September 'off' which damaged the wheel so it needed replacement (I have just replaced it and rebuilt the wheel), my front had done 25k km at least and its sides were still fine, if a little concave (rim was a Mavic MA3, replaced with an Open Elite).

 

[andrew_s]

Some rims have internal cavities that show up as holes in the braking surface when you hit the wear limit, rather than a groove that vanishes.

My experience is that the rims actually fails at about 0.7 mm, so retiring it when less than 1 mm seems right.
Your rim looks like it's got plenty of life left.

Rims also used to be thicker when they were simple extrusions bent into a circle and pinned at the joint. When you take the same extrusion, replace the pins by a weld, then machine the weld smooth, along with the rest of the braking surface, you take off quite a lot of thickness and wear life.
I call them "pre-worn out rims", but there's no choice these days.

 

[Smokin Joe]

Some rims have internal cavities that show up as holes in the braking surface when you hit the wear limit, rather than a groove that vanishes. View attachment 387300

My experience is that the rims actually fails at about 0.7 mm, so retiring it when less than 1 mm seems right.
Your rim looks like it's got plenty of life left.

Rims also used to be thicker when they were simple extrusions bent into a circle and pinned at the joint. When you take the same extrusion, replace the pins by a weld, then machine the weld smooth, along with the rest of the braking surface, you take off quite a lot of thickness and wear life.
I call them "pre-worn out rims", but there's no choice these days.

A good case for disc brakes.

 

[mjr]

A good case for disc brakes.

Or hub brakes.

 

[Smokin Joe]

Or hub brakes.

Anything but rim brakes. An antiquated system that is well past it's sell by date.

 

[Illaveago]

[QUOTE 5078866, member: 9609"]My front wheel is old, 30k ish miles, and I have noticed a slight concave on the wall and don't see any wear indicators. So I popped the tyre off the day to take a bettrt look and I am measuring it at between 1.7 & 1.8mm. which seems thick enough.
In comparrisom the new rim I bought last year for the rear was only something like 1.6 thick, and the one that replaced was down to 0.94mm

why is the rim I have so thick, did they just make them better once ?
and what looks like a little con-caveness - is it reasonable to assume it has just worn that way ?
View attachment 387185 [/QUOTE]
It looks like they were made that way according to the post showing a cross section.

 

[fungalcycle]

I have fallen slightly behind in tech/spec racing. How do rim/disk brakes compare weight wise? I am not talking in GP terms of carbon and titanium stuff, but in common similar price range systems.
The wheel design to handle the disk forces must have different bracing/spokes, while rim brakes don't need this extra loading. Looking around at modern bikes I just don't see this. Either those disk wheels should be deteriorating soon when heavy braking is a habit or rim brake wheels were always way over designed.

 

[Illaveago]

I have fallen slightly behind in tech/spec racing. How do rim/disk brakes compare weight wise? I am not talking in GP terms of carbon and titanium stuff, but in common similar price range systems.
The wheel design to handle the disk forces must have different bracing/spokes, while rim brakes don't need this extra loading. Looking around at modern bikes I just don't see this. Either those disk wheels should be deteriorating soon when heavy braking is a habit or rim brake wheels were always way over designed.

I wonder if they thought about that ?

 

[overmind]

Some rims have internal cavities that show up as holes in the braking surface when you hit the wear limit, rather than a groove that vanishes. View attachment 387300

How dangerous would it be to ride with a wheel like that where the gap is, say, less than 1mm or just a crack? Could the wheel fail catastrophically? Has anybody got any experience of a wheel failing while in this condition? What happened?

 

[Tim Hall]

I'd say it could fail catastrophically. Or at least very noisily. The rear wheel on my tandem failed in such a fashion. Tyre became unseated as the rim couldn't hold it in, tube escaped and went bang, wheel would no longer turn. I pushed it to a pub and had to get a taxi. The rear wheel went on my tourer in a similar fashion, luckily on yards from home.

A front wheel failure followed by sudden reluctance to turn would have a much more severe outcome.

If you're worried about the state of your rim, put on ear defenders and pump the tyre up to well in excess of your normal pressure (something in the back of my mind says 1.5 x normal, but don't quote me). If it goes bang it was on its way out. I've bought an Iwanson gauge to check my rim thicknesses and am using 1mm as the minimum.