Black Mamba

Hello. This is my first post, although I've been reading this forum for a while. Thanks in advance for any advice you can give.

I am struggling to establish whether my wheels are steel or aluminium. I've done the magnet test and it is... inconclusive.

If I attach the magnet to the outer edge of the rims, the magnet sticks - but if I attach the magnet to the underside of the rim, it doesn't. The spokes are presumably steel, so I am wondering if the magnet is sticking to the steel in the spokes, through the rim, rather than the rim itself.

I'm guessing that if they don't stick to the underside, then they must be aluminium? A second opinion would be much appreciated.

2manybikes

If your rims are chrome plated and smooth, and the magnet sticks to the side where the brakes touch the wheel, they are steel. When you get to 10 posts you can post a photo, if you're still not sure.

2_i 

An alu rim may still employ steel elements. A steel insert is e.g. used where the band forming the rim closes on itself. Besides spokes, eyelets for the spokes will be out of steel. Alu is soft and the surfaces for braking will be covered with grooves. Steel surface, on the other hand, will stay relatively smooth. You can make a hardness test and try to mar rim surface by using the tip of a nail like a pen. It should be easy with alu but very hard with steel. Don't overdo it because you do not want to damage the rim.

Marcus_Ti

What year/make/model is this bike? Unless it is extremely cheap, or vintage...you probably don't have steel rims.

Andrew R Stewart 

Also is the outlier of stainless rims. They look much like chromed steel rims but with little or no magnetism. Some Asian bikes in the late 1970s and 1980s came with them. Have you weighed the rims? Scratch test or spark tested yet? Andy

dsaul

Are there wire bead tires installed on the rims? The magnet will be attracted to the steel wire inside the tire bead, which would explain why the magnet only sticks to the side of the rim.

SurferRosa

Put the magnet up to something you know is steel. It will be attracted h a r d !

Put the magnet up to something like aluminum rims with steel beaded tires, and it will barely be attracted.

Learn the difference.

Don't use a giant magnet. Use something like one would find on his fridge.

Black Mamba

It's a vintage Dawes. I haven't been able to find out the model, but it's old enough that it doesn't have indexed gears. I'd guess early 70s?

Thanks for all the replies and suggestions. It's still inconclusive but may be clearer when I take the tyres off (I have replacements on the way).

Based on the descriptions (hardness test, smoothness of rims) it sounds like they must be steel - but the magnetism in different parts of the wheel is a bit of a discrepancy. I tried again with a different magnet which is less strong. On the spokes, it stuck straight on. Where the brake pad touches the rims, it fell off. So I'm still baffled.

HillRider

The rims are aluminum. If the magnet fell off the brake track, they aren't steel.

Black Mamba

I wanted to write an update to this, in case someone has a similar query in the future.

The rims turned out to be aluminium. The magnet test was much clearer cut once I took the tyres off. It seems like maybe the magnet I used initially was too strong. Like @dsaul suggested, the magnet might have been attaching to the wire bead of the tyres.

A couple of other points:
- The hardness test suggested by 2_i was inconclusive (maybe I wasn't doing it right)
- The rims are smooth and possibly chrome plated - but the wheels are still aluminium

In the end, in the end, there was a crack in the hub, so I ended up replacing the back wheel anyway.

Thank you everyone who replied for your tips and advice.

mr_bill