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Rim Brakes Wearing Out Rims

Old 08-14-19, 08:47 AM
  #26  
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Great Trivia information!

Originally Posted by terrymorse View Post
That article is mistaken. Kool Stop Salmon pads are made with the Scott Mathauser compound, which has a hardness of A/91.

Compare that to pads from Shimano, which range from A/89 to A/92. Or the Kool Stop Eagle Claw pads at A/89.
TIL that rubber compounds are measured for hardness! It's not a logarithmic scale like the Richter scale, is it?

BTW, this thread is kind of off topic anymore. OP wanted to know how to slow brake surface abrasion, and was concerned about sidewall blowout. Responses indicated that cleaning the pads and rims will abate said abrasion, or that the degradation is typically gradual enough to not merit extra concern.
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Old 08-14-19, 08:52 AM
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Originally Posted by Unca_Sam View Post
Responses indicated that cleaning the pads and rims will abate said abrasion, or that the degradation is typically gradual enough to not merit extra concern.
In addition, Kool Stop Salmon pads will reduce abrasion of the rim's braking surface. Especially if the bike is ridden in wet conditions.
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Old 08-14-19, 08:56 AM
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Perhaps people just think Kool Stop pads are soft because they're replacing brick-hard pads from decades ago.
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Old 08-14-19, 10:13 AM
  #29  
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Originally Posted by 79pmooney View Post
Celticgirl, rims wear out from caliper brakes over time. Fact of life. It's part of the stopping process. (Discs do too.) How fast depends on a lot of factors mentioned above. Riding in the wet speeds up the wear a lot. Likewise riding in abrasive dust, sand and gravel.
+1
If the OP is a fair-weather only type of rider, donít worry about it.
All-Weather, high-mileage riders can benefit from regular inspections.
Iíve had two rims fail catastrophically, and some merely flare out in a less spectacular manner.
About the only realistic way of reducing wear that I can think of is pad choice, and regular cleaning of pads and rims. The stock pads on a Merida I have were nothing short of AMAZING WRT picking up debris.
Itís possible that brake technique might matter too. Dragging the brake is poor descent technique WRT heat build-up. Perhaps it also accelerates wear.
One expensive option is to go for ceramic coated rims. As far as brake wear goes, they last ĒforeverĒ.
With that said, they need to outlast a standard rim 3-5 times to make up for the higher price.
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Old 08-14-19, 10:18 AM
  #30  
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What about aluminum oxide buildup in the pads!?

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Old 08-14-19, 10:34 AM
  #31  
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Celticgirl, I forgot to mention one thing you can do that will make a real difference, especially if you ride in the wet. If you have access to a garden hose or the like after your rides, you can do a quick blast with the nozzle set on a narrow jet. I have a routine where I spray the bike down (below the top tube) with a fine mist to generally clean the bike (and wash off that miserable grey braking powder) and blast the brake pads from both front and back with the jet (making sure I don't it the headset). This way you start your next ride with very little grit embedded in the pads. (I don't inspect but I can tell they feel clean when I apply the brakes.)

Another trick - if you feel grit in the pads while you ride, dab on the brakes a few times. Doesn't always work, but often you can feel the pads go clean as you knock stuff off them.

Edit: If I lost access to my garden hose, I would look into brushing my pads clean with say emerycloth. Something cardboard like in stiffness that I could easily slide between the pad and rim and gently "brush off" the pad, maybe very gently squeezing the brake as I did so. (I just thought of the material. Discs for angle grinders. The 6" (or so) hard, thin pads of say 60 grit coarseness. Home Depot tool section.) I haven't tried this. Actually I have a non-incentive to being completely pro-active in saving rims - I love building wheels!

Last edited by 79pmooney; 08-14-19 at 10:43 AM.
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Old 08-14-19, 10:55 AM
  #32  
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If you have canti brakes, you can quick release the yoke cable and the pads should swing out so you can visually inspect them and clean them. Then wipe down your rim brake surface at the same time.
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Old 08-14-19, 11:24 AM
  #33  
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Originally Posted by Unca_Sam View Post
How many miles were on those rims?
Probably quite a few. The thing I've noticed when a rim is getting thin and the brake track begins to bulge outward under air pressure, the brake will give a "thumping" sensation when it's applied. Once the thump is felt, a close inspection of the rim will usually reveal a wide spot associated with a crack. This is the time to replace the rim... before it looks like the image ^^.
(Note that rim damage from an impact can also cause thumping in an otherwise un-worn rim.)

Originally Posted by Unca_Sam View Post
A wheel is more likely to require replacement for worn cups or impact damage to the rim than for a sidewall blowout.
I'm going to disagree with you here (about worn bearings anyway). Hubs can last a long, long time if they are maintained regularly and properly. When the bearings start to wear out, it's usually the cones that show early signs of wear; if these are replaced, the cups can last almost indefinitely. Rims can be thought of as "consumable" parts, sort of like brake pads.

In my experience, road rims and mountain rims wear slowly... almost imperceptibly. Small-diameter (406 ERD 20") rims on commuter bikes do wear out. I have replaced several over the course of ~20,000 miles. Interestingly, the only wheels that I've had the "thumping" phenomenon on are the rear wheels. These are on bikes with rim brakes on which the front brake is used heavily. The front rims show wear, but I've never had to replace one. My hypothesis is that the front wheel kicks up road dust that gets on the rear rim and acts as an abrasive. This problem was so bad on my dedicated "winter" bike that I installed a roller brake on the rear wheel. Problem solved.


This is where the brake was thumping.
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Old 08-14-19, 11:44 AM
  #34  
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Originally Posted by Unca_Sam View Post
A wheel is more likely to require replacement for worn cups or impact damage to the rim than for a sidewall blowout.
Not if it's used for rain riding in the PNW with rim brakes.
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Old 08-14-19, 11:52 AM
  #35  
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Originally Posted by sweeks View Post
I'm going to disagree with you here (about worn bearings anyway). Hubs can last a long, long time if they are maintained regularly and properly. When the bearings start to wear out, it's usually the cones that show early signs of wear; if these are replaced, the cups can last almost indefinitely. Rims can be thought of as "consumable" parts, sort of like brake pads.
This is where the brake was thumping.
No, no, we agree, with the key phrase being regularly and properly maintained. A hub refurb costs $50 for two wheels and is recommended at least annually by most bike shops, because balls are cheap and a new wheelset is not. Poorly done maintenance can easily trash a hub if the cones are too tight. And you at least agree that an unfortunate pothole or hard pavement transition is far more likely to trash the rim than brake wear, unless you're on tiny wheels or in the PNW apparently.
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Old 08-14-19, 01:21 PM
  #36  
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I've worn out 2 set of road rims to point of noticeable cupping. I avoid riding wet conditions as much as possible. Mainly use Kool Stop salmon pads.
Probably about 40k-50k miles before cupping is a concern.
Went threw 2 sets of mtn rims before going to ceramic coated rims which really reduced wear. Before disk brakes were a common brake.
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Old 08-14-19, 08:50 PM
  #37  
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Originally Posted by Unca_Sam View Post
How many miles were on those rims? As is the case with jetliner crashes, a few spectacular failures will hog all of the attention when there are a million non-failures.

A wheel is more likely to require replacement for worn cups or impact damage to the rim than for a sidewall blowout.
It was less than 3 years and maybe 5,000 miles from when I built that wheel until the time it let go. The bike was ridden all year long and I live next to Portland, Oregon. Mooney's correct: our rain plus road grit wears rims like nowhere else.

Since then I've rebuilt several wheels before the rims went boom. Once the brake track shows lots of dish- out it goes.

FWIW: my next bike will have disk brakes.
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Old 08-14-19, 10:43 PM
  #38  
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Originally Posted by rydabent View Post
Hmmmmmm the anti disc brake types says this dont happen.
No one has ever said that here. What we do say is that they donít wear out as rapidly as you seem to think.

BTW they are losing the argument to all the new road bikes coming with disc brakes.
There are still millions of bikes being made without discs and there are millions (perhaps a billion) more that donít have them.
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Old 08-14-19, 10:57 PM
  #39  
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Originally Posted by HTupolev View Post
It does happen. How fast it happens depends on how clean the rims and pads are, the particular rim and pad materials, the conditions you're riding in, and how much you're braking.
How often you use your brakes is the most important parameter. If you don’t use your brakes that often, you rims will last longer.

Cost to replace a rim depends entirely on the particular components.
Basic reasonable rims can be had in the ~$30 range. Fancy aluminum rims can get into the ~$200 range. Decent round spokes and nipples tend to run a little over $1/spoke, although nice bladed spokes can be over $3/spoke.
Not quite. I’m not sure what you mean by a “basic” rim nor by a “fancy aluminum” rim but $200 is far too high for even the fanciest of aluminum rims and $30 for a cheap rim is probably too low. $40 to $90 would be a more realistic range. You also need to factor in the cost of the relacing and retensioning the rim. That’s going to be probably about an hour of mechanics time which is about $75.

It’s also not as simple as you make it out to be. Rims have different effective rim diameters (ERDs) that have to be matched or the spokes won’t work. A single wall rims ($40 above) can’t just be swapped for a double walled rim (the $90 one). The spokes would be too long. The spokes would be too short if you went the other way.

Often it isn’t cost effective to rebuild a wheel because of the cost of the rebuild and having to find an identical rim to the one being replaced or at least one with the same ERD. Spokes can outlast lots of rims but getting everything just right isn’t always possible.

Alternately, it's frequently cheaper to just buy a new wheel... You'll want to check hub adjustment and spoke tension on any wheel that's not made carefully by a good wheelbuilder, though.
Generally speaking, yes, buying one is always cheaper than building one. The only real reason to build a wheel is if you are building something special or because you want to experience the process. But you can’t build one for cheaper than you can buy one.
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Last edited by cyccommute; 08-15-19 at 06:30 AM.
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Old 08-14-19, 11:11 PM
  #40  
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Originally Posted by cyccommute View Post
How often you use your brakes is the most important parameter. If you donít use your brakes that often, you rims will last longer.
Effects of environmental conditions can be just as dramatic. I've got two Sun M13II rims that each have about 1,500 miles on them, both ridden by myself over about the same span of time in the same area. One has been used almost entirely in the dry, the other almost entirely in abrasive PNW wet conditions. The former still looks practically new, the latter is most of the way through its wear life.

Not quite. Iím not sure what you mean by a ďbasicĒ rim nor by a ďfancy aluminumĒ rim but $200 is far too high for even the fanciest of aluminum rims and $30 for a cheap rim is probably too low. $40 to $90 would be a more realist range.
By "basic" I'm referring to entry-level box-section rims like a CR18. By "fancy" I'm referring to exotic high-performance designs like the AForce Al33 (perhaps usually less than $200, but with options like ceramic coating they can get close).

Itís also not as simple as you make it out to be. Rims have different effective rim diameters (ERDs) that have to be matched or the spokes wonít work. A single wall rims ($40 above) canít just be swapped for a double walled rim (the $90 one). The spokes would be too long. The spokes would be too short if you went the other way.
That's why I mentioned the cost of spokes.
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Old 08-15-19, 06:06 AM
  #41  
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Mavic A119 is 16.76€. I have them on one of my bikes, and they're not too bad. If I were going through rims on that bike, I'd just buy a stack of them.
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Old 08-15-19, 08:29 AM
  #42  
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OP has suggested in other threads that she rides a cruiser style bike on paved surfaces. Also, she hasn't been back to this thread so I'm guessing her question was answered.

As my boss likes to say, I think everything's been said but not everyone has said it.
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Old 08-15-19, 09:04 AM
  #43  
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Originally Posted by kingston View Post
Mavic A119 is 16.76€. I have them on one of my bikes, and they're not too bad. If I were going through rims on that bike, I'd just buy a stack of them.
When I built the dyno front wheel for my fixed-gear, I chose the lowly Weinmann ASX7. Generous brake track thickness yet decently lightweight for its width, and if I do manage to wear it out, they're $20 and plentiful.
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Old 08-15-19, 07:42 PM
  #44  
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Thanks everyone for the very informative posts, I've had quite an education. This topic is something I never thought about all these years, until I read about rim wear somewhere.

I just ride casually pretty much around town and to the grocery store, and in dry weather.

From what I've read I guess my rims should outlast me.
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Old 08-15-19, 09:20 PM
  #45  
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Originally Posted by Celticgirl View Post
From what I've read I guess my rims should outlast me.
May they take a long time to do so!
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