Should I be worried?

[lowflyer]

If you are keeping the bike for some time then you may as well change it sooner rather than later. Makes no sense to not get it sorted if it will prey on your mind.

Well said , but I think Mick was thinking that it may not be enough time to get a new wheel laced up in time for Galloway.

[AlanH]

The most sensible piece of warning advice is to whip the tyre off and check that the inside won't chafe a tube. As long as that checks out, I really wouldn't worry about it. It's not going to suddenly fold up even if you are landing some serious jumps off-road. You've got suspension and tyres that absorb most of the impact forces and the safety margin on OEM wheel rim strength is absolutely massive.

[ritosxf]

id ask the fella that fitted the tyre if he had a pile of rotting ally on his floor , if he didnt , and he wasnt gassed by the smell of rotting fish ( ally rot smells like grimsby fish dock ) then its not got too much ally rot ,,,,its usually worse on the inside than the out side , as water gets trapped in there and rots the ally , ever had an ally angined car and ran it on water not 100% anti freeze , soon rots the water pump ,,,, rims are very similar ,
ive seen em as bad as they get , gig chuncks dropping off both inside , and out

whens the mot due ? , a tester may fail it on this , or you may just get an advisory note ,,,

[angelo]

I don't think that is safe at all - only a few spokes come into play at any part of a revolution - a wheel spindle HANGS from spokes so there it a chance of this wheel collapsing. Seriously get the wheel checked professionally.

[AlanH]

I don't think that is safe at all - only a few spokes come into play at any part of a revolution

That's a common misconception. All the spokes are under tension and the load is spread over not just a few at the top, but all the ones above the horizontal line through the axle i.e around 50% of the wheel's circumference. The ones at the top will be under the highest tension with the spokes taking progressively less load the further towards the horizontal you get. The entire rim is held in compression as all the spokes are pulling it inwards therefore even a rim that has broken all the way through still tends to hold straight. Spoked wheels are mind-bogglingly tough.

[angelo]

I don't disagree but given that our wheels are on the large size means we have longer spokes - you can flex them by squeezing them together - it suggests that although you may not see movement there will be some any weak point as the hang and push if you get what I mean.

With the rim clearly weakened there is bound to me micro flexing - take a thin bit of steel and bend it back and fire enough times and it snaps - ok this is extreme but you have to wonder how the spilt got there in the first place.

If it were mine I would strip off the tyre and have a look - 15 minutes of time well spent.

[AlanH]

take a thin bit of steel and bend it back and fire enough times and it snaps

...but this is a thick piece of alloy that is not flexing significantly, certainly not undergoing any non-elastic bending and is therefore not a good comparison. Fatigue failure really isn't going to happen imminently on a small corrosion defect like this - especially one that does not involve any spokes. Ask anyone who has tried to straighten one of these rims how immensely strong they are.

If it were mine I would strip off the tyre and have a look - 15 minutes of time well spent.

Totally agree with that bit of advice. Post the photos too

[micksylver]

Don't Panic!

Something I really need to remember.

Took the rear back to my local repair shop. Took the tyre and tube back off to have a look and found that all is not as black as it seems.

The crack is not through the rim, it is just a "flake", plenty depth of metal still remaining. Seems that corrosion has started at the valve hole and spread outwards from there just below the anodising on the surface of the rim. The rim is otherwise sound with little or no sign of corrosion anywhere else. Whew!

Below are some pictures of the flake, looks a little like a razor blade. You can clearly see the half outline of the valve hole.



The rim is at the shop, valve hole being welded and a new valve hole drilled further round the rim, before refitting tube and tyre. Picking it up tomorrow. So Galloway trip is still on for me without having any doubts regarding the rim.

Had quite a few little problems in the run up to Galloway trip - hopefully this is the last!

Oh, and please don't anybody remind me that it is Friday the 13th when I'm travelling up!


Edit: Thanks again to all who posted a reply.