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So, my road bike has a very noticeably worn rear wheel rim and it's got me thinking about when I should replace it.
My only thought at the moment would be to use calipers to measure the minimum rim-wall thickness, much as you would on a car disc rotor, but I couldn't say what would be a safe minimum.
Does anyone have any rule of thumb that they would use for determining when a rim is past its best? STW, help me out!
Don't rim-brake rims normally have a wear indicator groove running around the circumference?
If you can't see this, you've presumably worn through it.
If you're thinking about it anyway, just replace it man! What's the worst that could happen if you didn't?
Usually when rim wall is <1mm and the rim brake track is noticeably concave - as the metal wears thin and the pressure of the tyre bead forces the edge outwards, the brakes start to 'pulse' like its buckled, but it isn't and cracks form in the rim walls. Leave it too long and the rim fails catastrophically, tyre comes off the bead jams the wheel and if going at speed sends the rider OTB.
The best thing about disc brakes is not having to replace a wheel because the braking surfaces are worn paper thin after a year riding in slop in grit.
+1 that, and doesn't matter so much if it goes out of true a little.
Leave it too long and the rim explodes. I know.... ahem. Had to call the Team car out - the only time ever, and I was on a long commute home (i.e. going the long way) and it happened at the furthest point from home.
Put 130psi in the tyre. If the rim doesn't explode then it's probably ok for a bit more use.
Hah, good advice - thanks all.
Usually when rim wall is <1mm and the rim brake track is noticeably concave
It's definitely this, and some more. I think that, for my own piece of mind, I will replace them with something new.
If you “think” it needs replacing then it more than likely does need replacing, especially if the braking surface is concave in nature.
Back in the early 90’s my mates rear araya rim on his diamondback apex exploded and split whilst we were out exploring in the middle of nowhere in the Galloway hills on a very shitty spring day, a long sliver of swarf separated from the rim and pierced right through his lower leg calf muscle due to wheel rotation - it was **** gruesome and i left him immobile with my jacket round him on the hillside as he couldn’t move, it took me almost 2hours to get to the nearest house to phone for help, then a further 3 hours for mountain rescue to reach him and a further 2 hours till he was in hospital. A very messy day indeed but he has a cool scar and story to show for it as they had to open up his calf muscle to ensure it was clean and to prevent infection.
I’ve just noticed I have a VERY worn rim on a Tiara front wheel (it’s had 1000s of miles of County Durham winter commutes, no no too surprised) I might use the opportunity to save the hub and give this wheel building lark a go. If it goes bad, what’s a new Tiagra wheel....£45?
If you don't give wheel building a go I've a brand new, unridden/fitted Shimano R500 wheel that needs a buyer.
I did once cut up a heavily concaved road rim that I was retiring. There was a surprisingly large amount of material still left across the thickness of the braking surface, considering the wear. I have no hard info on what the safe limit is.
lordmerchant - swapping a rim is a great way to start wheelbuilding. You can skip the whole palaver of having to lace it, just unwind the spokes one by one and reattach to the new rim. If you make a balls up of it. you can always take it to a shop! Plenty of good folk here would be happy to write a more detailed and helpful procedure if you're interested.
Yeah, I have exactly this on my road bike. Irritatingly it's a Campagnolo wheel with a 22 hole rim which seems to be completely unobtainable. So, new wheel it is.