Yikes, after another muddy winter off-roading it feels like my Magura HS33 rim brakes have munched their way into the braking surfaces on my Mavic rims.

The braking surface feels concave and grooved. Has anyone else experienced this? At what point should I get a new rim? Anyone had any experiences of rims failing because of this?

I’m strugging with a dliemma here. On the one hand, I’m so spineless and cowardly that I’m terrified of my rims splitting and killing me, and on the other hand I’m so lazy and stingy I can’t be bothered to get a new rim unless absolutely necessary.

Help!

Why do you have rim brakes? I lurve disk brakes

Thats what happens with rim brakes. I have had rims explode on me twice – heavy fall on one occasion as the front collapsed on a fast descent. Put a straight edge across the rim and measure how deep the wear is and compare that to the wall thickness of the rim.

Every couple of weeks try putting about 60psi in your tyres. If the rim goes bang then its time to change them. In the meantime you’ll probably find that one day you get an odd rubbing sound from one of the wheels. This will be the rim side wall starting to come away, this is also time to get new rims.
Otherwise just bite the bullet and get new rims now.

Or disk brakes?

get some ceramic or css rims, they are expensive on the outset but if your paying for someone to build your wheels each time they will soon save you money. most coated rims are about twice the price of their standard alternatives, we have these old 121’s at a great price to clear though;
http://www.sjscycles.co.uk/product-Mavic-Mavic-121-SUP-26-Inch–559-ATB-Alloy-Rim-with-Ceramic-Sidewall-765.htm

rim brakes, thats a blast from the past 😆

Discs would be ideal, but that’s an expensive upgrade because I’d need a new fork with disc mount, as well as the wheels and brakes. Like for like upgrade from my current kit (Pace, XT, Mavic, Magura) would be at least £800.

Some good advice here though. I’ll blow up my tyres and see what happens. I think they’ll last the summer when there’s less grinding through mud anyway, and then ceramic looks like an answer. Thanks.

It might be worth taking the wheels out if you are going to do that and not stand too close as if the rim does go it can be a bit unnerving. It was when it happened to me anyway 😯

I still use HS33s on 2 bikes, they’re the nicest feeling brakes IMO even over hydro discs. In the mud they’re real rim munchers however I have gotten right through some braking surfaces in sections 3-4 inches long without the wheel exploding – wouldnt recommend it though 😀

You shouldnt let the depth of the concavity get past about 1/2mm give or take. The wall thickness of your rim is not the thickness of the bit you think you can measure with calipers – thats a rolled over section so expect actual thickness to be about half that thickness.

I agree the feel is fantastic, as is the power. The real reason I still use them is poverty though.

Good to hear other riders are still using them, and I’m relieved to hear relatively few horror stories about catastrophic rim failures!

They dont work well in the snow though, and ultimate stopping power goes to a 4 pot large rotor disc 🙂

When my rims have “peeled” they’ve done it slowly and jammed the wheel first by expanding widthwise 🙂

I’ve heard stories from the early days on Whistler bike park (was on blackcomb back in the day) where riders rim brakes wore through the braking surface in only a few descents meaning that the tyre was no longer attached to the rim/spoke section.
Other stories about v-brakes bursting innertubes as the rims get so hot.

I’ve got some old radial bontrager wheels where there’s not a great deal of metal left on the rim cross section.

Essentially, discs wear out, so there no reason your rim wont.

For those of us who are old enough to pre date discs, this is nothing new. A rim would last a winter in scotland with cantis. HS 33s are known for eating rims.

I used to get through at least a rim per winter riding the Quantocks with Vs.

My take is that HS33s are so powerful, compared to V’s, that you are much more likely to get through your rims. Best plan is to either get ceramic rims (if you can still find any), or perhaps consider some decent V’s, at least at the back. They’ll be mostly as good at stopping you, but slightly easier on the rims.

Anyone had any experiences of rims failing because of this?

A few times, a very loud bang followed by a flailing strip of the rim, pumping your tyres up to 60 psi every week or so, to check the rim for signs of distortion is a good idea, but wear ear plugs because if the rim does go the bang really makes your ears ring 😕