How do I know I need new rims?
 

Hello!

I was just having a look at my Mavic A719's and whereas the breaking surface (I use v-brakes) is ok in the front, in the back wheel it's slightly indented indicating significant wear. This year I'm planning to go on a 1500+ km tour, would you say I need new rims? Having said this, would you think switching to discs is a good thing to do?

Best
Przemek

Put a straight edge across the side of the rim and check the amount of wear, I would rather be safe than sorry and start with a new set of rims. Changing to discs can be cost prohibitive, especially if your current bike doesn't have the disc mount front and rear.

Aaron :)

I'd get new rims and have the peace of mind of one less thing to worry about.

As for switching to discs, is your bike set up for discs? If so, and if you have the money to do it, I would do that in a heartbeat.
I am planning on getting a new touring bike with discs this year, to replace my old bike that has canti's.

Many rims have a small indentation on them, which serves as a wear indicator. Once the indent has disappeared and becomes flush with the rest of the braking surface. If you notice any cracking near the eyelets or holes where spokes enter, that is another reason for new rims.

Switching to different brake style may or may not be cost effective. It would really depend on your current wheels- do you have really nice hubs? Can your fork/seatstay accept a disc brake caliper?

Mavic 719's have an internal rather than external wear indicator. When the rim is finished a small hole will appear in the side of the rim where material has been machined out from the inside.


Aside from replacing the rim outright, the best alternative is to estimate how many kilometers are already on the rims to decide if another 1,500 is significant enough for concern. Braking wear is determined by driving habits and terrain. For example I wear my front rim more than the rear but get good milage out of both because most of my driving is on flat terrain with a touring rig.

If a straightt edge across the rim shows 1mm wear you're really close to the end.

if you switched to discs you'd have to change the pads! Seriously one new rear wheel would be cheaper than switching out two wheels with a whole new braking system.

Thank you very much for your answers! I've used the rims since Aug 2010 and only for daily commuting 1h a day in total. And actually I asked the question about discs before realising how expensive they can be ;) For a set of A719's I paid something around 160 GBP ($250). Would you say that it's more cost effective in the long term to buy discs and curb rim wear? As for being set-up for using discs I'll be getting the Planet X Kaffenback frame so no problem with that.

PS: I've just found a good deal on A719, possibly I can reuse my XT hub after some cleaning but what spokes would you recommend?

Unless there`s more to the story, you can definitely reuse the hub. And since you`re talking about another rim of the same model, you should be able to reuse the same spokes too, IMO. But you`ll have to weigh that one out for yourself because some folks will likely tell you not to reuse the old spokes- your call there.

Any name brand stainless steel spoke, (Wheelsmith, Saipim, or DT). You can reuse the old, I do it all the time. My only caveat would be to make sure you put the spokes back in the hub using the same orientation that they had originally.

Aaron :)

+1

Unless you are riding somewhere pretty hard on rims 1500k is a pretty small portion of the life of a rim. Unless you are somewhere pretty remote replacing a rim along the way isn't that huge of a deal anyway. It may vary depending on where you are going, but I probably wouldn't worry unless there are definite signs of impending failure, like cracks or wear indicators showing.

Replacing a rim using the same spokes is super easy and if you are somewhat mechanically inclined you could do it by the side of the road in 20 minutes or so. You can just:

1. Tape the old rim to the new one with the holes lined up (including valve hole).
2. Loosen all of the spokes.
3. Move spokes to new rim one at a time.
4. Discard old rim.
5. Tighten all spokes to some uniforn repeatable place, like maybe with 1/4 turn of thread showing. This will keep the roundness and dish pretty close to correct.
6. Go around the wheel tightening each spoke the same number of turns until the wheel starts to firm up.
7. Once the spokes have some light tension, be sure it is true and round. Also try for even tension. Adjust as necessary.
8. Then add tension is layers. By that I mean, increase tension in all spokes in increments truing at each pass.
9. Repeat until desired tension is acheived and then fine tune trueing one last time.
10. Stress relieve the wheel in the last step by squeezing groups of four spokes.

On the switch to discs... Why? Did you find your current brakes unsatisfactory? If not, in what way? If only to avoid rim replacement, I wouldn't unless maybe extreme conditions are causing very short rim life.

tbh if its just 1500 km i'd keep using what i have

Take off the rim tape. Loosen all spoke nipples a turn or two. Then tape the new rim to the old rim so that the valve hole is in the same place and the labels read the same (not one being upside down when you look at them). Then start transferring spokes from the old rim to the new, one at a time. You will figure out rapidly which spokes to move first and which to transfer last.

I think I have three times as many miles on my A719 rims with minimal wear. I would look at them harder to figure out if you really need a new rim. Since you put very little wear on the front rim, keep the old rear rim for possible use on the front later if you do buy a new rim.

When my brake pads look bad like aluminum oxide instead of rubber or when they sound rough, I lightly sand the brake pads to get to fresher rubber. Brake pads are a lot cheaper than good rims.

I have done something like this. I stuck a ring of duct tape on one side of the spokes, about mid way between the rim and the hub, then turned it over and put a matching ring of tape on the other side. Glue side to glue side. That held all the spokes in place. Then I unscrewed the nipples and swapped rims. It didn't take long at all. I did have a bike shop do the final truing, though. They charged $10 per wheel.

same, 18mo of unloaded commuting doesn't seem to be enough to need a replacement.

I agree, it may as well not be. Just preferred to ask experiences of the folks around here what is a dinifite indication of an exhausted rim. Especially with a view to riding such a long distance at once. I'm not really proficient at truing the wheels so I would rather not something like this happened en route.

Today I put a ruler to the sidewall to check how big of an indentation there is between the wall and the ruler. Well it's slight but heading for 1mm and in this situation I may be inclined to spend the 40 GBP for a rim if a third what Im going to cover in three weeks was what took me to ride a year and a half.

I'm guessing that if you're talking GBP then you're somewhere in the British Isles, which have more than their share of hills and rain. So if you managed to put that much wear on a rim driving unloaded, I agree it would be safer to swap it out before going on an extended loaded tour. You'll be using the brakes to slow a much larger payload and rim wear will increase accordingly.

I've found that it takes surprising little winter riding on steep hills through slushy dirty snow with heavy down-hill braking to wear out a rim.

Przemek, If worrying about the rim will interfere with the enjoyment of the tour, replace it.

Brad

+1 or 2.... I found these metal particles in a set of brake pads I was cleaning today.
I suspect that this is pretty hard on rims.

http://i783.photobucket.com/albums/y...IMG_6936-1.jpg

Yikes! I'm looking at the contact area (or rather the lack of) on those pads. For maximum braking efficiency the pads need to make full contact with the rim - not just on one corner!

When I lived in Seattle and commuted in wet, crappy weather all winter, my LBS recommended sanding the brake pads pretty regularly to get the bits of metal out. These accumulate alarmingly rapidly when riding in wet weather.

The cheaper black pads, like the ones that come with Tektro brakes seem to pickup more aluminum than better pads, like the salmon Kool-Stops. And those aluminum pieces are very tough on rims. If you let it go too long before picking them out, you'll get some nice gouges in the rim.

After you pick the aluminum pieces out of the pads and sand them, I'd check the rim and sand it also if needed. Those pads look like they have a lot of life left, when it is time to replace, I'd recommend a better pad. Or, you could be like me and replace them as soon as I buy the brakes.

Sanding the pads is a good idea. If the pads are glazed over, you don't have as good of braking as you can get. But sanding really doesn't get the aluminum out, unless you want to sand a lot of the pad away. Just pick the pieces of aluminum out of the pads. I usually use either a razor blade or one of my "pokey tools". Which ever I see first on the bench.

My concern is the dark gray color dust because that is Aluminum oxide. That is the stuff that most grinding wheels for grinding on metal are made out of. When the brake pad surface is saturated with Aluminum oxide, that can eat away at the rims. You can't avoid Aluminum oxide because a fresh Aluminum surface will oxidize in seconds, but you can try to minimize the damage it can do by trying to avoid too much of a buildup of it on the brake pad surface. I don't get obsessive about it, when it looks bad to me or the brakes sound scratchy, that is when I will clean a bit off the pads. In my case that usually means maybe once every three to five hundred miles when it has been dry, more often when wet.

That was not the wear pattern! I was in the process of sanding the glaze off and evening up the pads. Once I saw the metal. I just sanded that area to clean it up for a picture. The corner was all that was left. I decided to toss the pads so I really didn't care how flat I made the braking surface.