Rim wear - what rate to expect?

tgotb

I built myself a pair of relatively cheap, bombproof wheels last year, specifically for commuting. Open Pro rims, Planet X hubs (they were going very cheap) and plain gauge spokes. In general they've been great; after about 8 months they haven't needed any tweaking, and are still perfectly true. However, the braking surfaces are showing some wear. Haven't measured it yet, but there's a noticeable depression (maybe 0.5mm) where the brake blocks run.

Is this normal, or do I have soft rims/abrasive brake blocks? They've probably done 4000-5000 miles, mostly through the Winter, experienced a lot more braking on the commute than they would on Sunday runs, and other than hosing it off after a wet ride I haven't been that fastidious about cleaning the bike...

How long should I expect a set of rims to last?

vorsprung

I've had a front 32h Open Pro since 2007 and it has probably done 15000 miles
It feels a bit worn and I am considering replacing it

mikety

Your wear rate is about right, I got about 9000 commute miles out of a set of Mavic Aksiums then about 6000 miles out of a set of Fulcrum Racing 7(although the hubs went first on these) I managed to improve the wear rate by using coolstop pads with an edge that cleans the rim of grit before the main pad touches.

mikety

Your wear rate is about right, I got about 9000 commute miles out of a set of Mavic Aksiums then about 6000 miles out of a set of Fulcrum Racing 7(although the hubs went first on these) I managed to improve the wear rate by using coolstop pads with an edge that cleans the rim of grit before the main pad touches.

UndercoverElephant

You wouldn't be the first to complain about Open Pro's having excessive rim wear recently. They appear to have gone markedly downhill in the past couple of years. Rigida rims are wear it's at for the all the cool kids.

Ian.B

I've got Mavic Ksyrium Elites showing about the same amount of wear - definitely concave on the braking surfaces also with about 0.5mm depression, maybe a bit more. I would guess they've done about 5000+ miles, mainly London/commuting.

There's no discernible rim wear indicator and I'm wondering if I ought to replace them to avoid risk of a blowout, but on the other hand I like the wheels, they've never needed any attention and always stayed true, and I don't want to bin them if there's a good bit of life in them yet. Hiow do you judge when to replace?

Underscore

I've just replace the rear wheel on my commuter (i.e. used when the weather is pants) after 5000-6000 miles so it doesn't seem too wide of the mark. My front, in contrast, is barely worn.

_

UndercoverElephant

If there's no wear indicator, I seem to remember that you inflate the tyre above what you normally ride at and if the rim goes pop, it was too worn. Better then than on the road. :shock:

Underscore wrote:

I've just replace the rear wheel on my commuter (i.e. used when the weather is pants) after 5000-6000 miles so it doesn't seem too wide of the mark. My front, in contrast, is barely worn.

_

Really? Shirley, you should brake more with the front?

MrChuck

Doesn't sound like bad mileage if it's ridden all year round.

MonkeyMonster

I still have the original wheels that came with the bike back in '98

built to last back then...

bigmat

MonkeyMonster wrote:

I still have the original wheels that came with the bike back in '98

built to last back then...

Only replaced my mountain bike wheels a couple of years ago, having been purchased in 1993 - even then, it was only because of a faulty freehub. I have since replaced the freehub, fitted knobblies and kept the wheels for snowy / icy commutes.

tgotb

Thanks all; I'd convinced myself that my (highly effective) brake blocks were unusually abrasive, good to know that's probably not the case.

As an aside, I was under the impression that 95% of the time I only use the front brake. The fact that both rims are equally worn shows that's clearly not true!

MonkeyMonster

UndercoverElephant wrote:

If there's no wear indicator, I seem to remember that you inflate the tyre above what you normally ride at and if the rim goes pop, it was too worn. Better then than on the road. :shock:

Underscore wrote:

I've just replace the rear wheel on my commuter (i.e. used when the weather is pants) after 5000-6000 miles so it doesn't seem too wide of the mark. My front, in contrast, is barely worn.

_

Really? Shirley, you should brake more with the front?

Now see... its more effective to break with the front but does that mean you need to or should? Ie if you manage your speed effectively then slower back wheel breaking might be more cost effective?

UndercoverElephant

MonkeyMonster wrote:

UndercoverElephant wrote:

If there's no wear indicator, I seem to remember that you inflate the tyre above what you normally ride at and if the rim goes pop, it was too worn. Better then than on the road. :shock:

Underscore wrote:

I've just replace the rear wheel on my commuter (i.e. used when the weather is pants) after 5000-6000 miles so it doesn't seem too wide of the mark. My front, in contrast, is barely worn.

_

Really? Shirley, you should brake more with the front?

Now see... its more effective to break with the front but does that mean you need to or should? Ie if you manage your speed effectively then slower back wheel breaking might be more cost effective?

Cost effective in what way? The amount of friction is the same, but the momentum gives you less braking. Thus, your pads and rims wear out the same amount, but you stop less.

greg66_tri_v2.0

This place is losing its touch. Almost a page down on a thread with "rim wear" in the title and not the slightest hint of a single entendre, much less a double.

<weep>

Come on, it's not that difficult. Friction. Riding. Lube. Blown rim. Banging. Rubbing. Squealing. Juddering. Fingertip test. Pads. Hell, there's even "hosing it off after a wet ride" right there in the OP.

Do I have to spell it out?

tgotb

UndercoverElephant wrote:

Cost effective in what way? The amount of friction is the same, but the momentum gives you less braking. Thus, your pads and rims wear out the same amount, but you stop less.

I'm pretty confident that the amount of wear is roughly proportional to the amount of work done in braking, so all you're really doing (from a wear perspective) is shifting the wear from one wheel to the other. The friction generated by the rear brakes is limited by the potential to lock the wheel, whereas you can apply more force, and therefore generate more friction, on the front.

If you throw away your wheels when the rims wear out, it's probably more cost-effective to use the front brake (because throwing away a front hub is cheaper than a rear). If you rebuild a new rim onto the existing hub, it's probably cost-neutral.

We should go back to the chromed steel rims I used as a kid. Not only are they harder wearing, but the brakes are so ineffective in the wet that there's little point in using them...

Edit: Greg66, you owe me a new keyboard...

UndercoverElephant

Sorry, Greg.

OP, What you should expect after a good deal of rim wear would be a little seepage in the undercrackers, and perhaps your voice raising a couple of semi-tones.

Edit: And I did put a grammar-nazi baiting trap into my first reply, I'd have thought you'd have spotted it.

UndercoverElephant wrote:

You wouldn't be the first to complain about Open Pro's having excessive rim wear recently. They appear to have gone markedly downhill in the past couple of years. Rigida rims are wear it's at for the all the cool kids.

MonkeyMonster

UndercoverElephant wrote:

Cost effective in what way? The amount of friction is the same, but the momentum gives you less braking. Thus, your pads and rims wear out the same amount, but you stop less.

My physics brain just went - eh?

Amount of friction as someone else has added isn't the same. Its more at the front hence better(faster) braking assuming standard tests etc.

Front blocks will wear quicker and/but you will stop faster using front rather than back. Therefore pads need replaced at front quicker - hence my *if* you manage your speed better and keep the friction less but for longer - ie use back, I would have thought that would wear the brake pads less quickly than if using the front - hence more cost effective. The replacing wheel arguement is entirely valid and answers it better and I remove my question but still - your points seem wrong to me in terms of physics.

shirley.

UndercoverElephant

I'm not sure about this, and so have reverted to A-level physics grade postulation - I'm happy to be wrong about any of the following.

It depends if all friction causes wear or not.

I was assuming that the wear caused by the brakes would be a constant for the pressure applied on either brake at a given speed. Both brake levers being identical and the pads also being identical. Thus, if you try to stop the bike with either brake, the wear of the pad would be due to the amount of time the brakes needed to be applied to the rim surface before stopping the bike.

It seems to me that the CoG that's behind the front wheel would mean that the bite of the front brake would be quicker, meaning that the front brake would be applied for a much shorter time, thus much less wear on the rear brake where the CoG is dragging the wheel further round.

tgotb

UndercoverElephant wrote:

I'm not sure about this, and so have reverted to A-level physics grade postulation - I'm happy to be wrong about any of the following.

I was assuming that the wear caused by the brakes would be a constant for the pressure applied on either brake at a given speed. Both brake levers being identical and the pads also being identical. Thus, if you try to stop the bike with either brake, the wear of the pad would be due to the amount of time the brakes needed to be applied to the rim surface before stopping the bike.

It seems to me that the CoG that's behind the front wheel would mean that the bite of the front brake would be quicker, meaning that the front brake would be applied for a much shorter time, thus much less wear on the rear brake where the CoG is dragging the wheel further round.

The flaw in your argument is that you're actually applying more force to the front brake (because you can). If you apply that much force to the rear brake the wheel will stop going round (which will reduce rim wear but increase tyre wear).

If you apply less force to the rear, the rim will wear more slowly, but you'll have the brake on for longer; the total wear will be the same.

UndercoverElephant

I think we need better fizzysists.

I can see that the force you can use may well be less, but I still think that the total wear is more related to the number of revolutions of the wheel than the braking force; especially in a coastal commute like mine where sand gets clogged on the pads and rims.

Edit: Plus, you've actually nullified your own argument that it's more cost-effective to use the back brake by saying that the wear is the same.

jonginge

Assuming wear scales linearly with force, I guess?

tgotb

UndercoverElephant wrote:

I think we need better fizzysists.

I can see that the force you can use may well be less, but I still think that the total wear is more related to the number of revolutions of the wheel than the braking force; especially in a coastal commute like mine where sand gets clogged on the pads and rims.

Edit: Plus, you've actually nullified your own argument that it's more cost-effective to use the back brake by saying that the wear is the same.

No, I said it's more cost effective to use the front, because the wear is the same (and the front will presumably be cheaper to replace)

You're right about the fizzysists though...

MonkeyMonster

UndercoverElephant wrote:

I was assuming that the wear caused by the brakes would be a constant for the pressure applied on either brake at a given speed. Both brake levers being identical and the pads also being identical. Thus, if you try to stop the bike with either brake, the wear of the pad would be due to the amount of time the brakes needed to be applied to the rim surface before stopping the bike.

It seems to me that the CoG that's behind the front wheel would mean that the bite of the front brake would be quicker, meaning that the front brake would be applied for a much shorter time, thus much less wear on the rear brake where the CoG is dragging the wheel further round.

First para is correct. However there is the fact that your weight helps the front means higher pressure between blocks because you can't skid so easily on the front and grip tighter - I was going higher pressure even for shorter time would mean greater wear than longer and softer on the back, but that is me taking a guesstimate based on knowledge. We're at odds with that but hey ho, you're probably wrong but it happens .

The front wheel replacement cost wins overall regarding rim replacement though tbh. Unless you can write the equation to take variables such as rim length of life, braking force back and front, rubber composition etc. etc. that shows more careful rear braking will still be overall cheaper over the lifttime of the bike...

Throwing sand is a factor might change the results but that depends on how the sand interacts at given heats. Lower speed back brakes are likely cooler and thus less rubber abrasion and longer block life. Higher pressure front will be the opposite. Sand would likely embed into the rubber if it were warmer and thus then abraid the rim more in conjunction with the hotter (front) pads.

Too many variables to cope with in all honesty - but overall replacement cost of front wheel being cheaper wins I think.

graham.

Greg66 wrote:

This place is losing its touch. Almost a page down on a thread with "rim wear" in the title and not the slightest hint of a single entendre, much less a double.

<weep>

Come on, it's not that difficult. Friction. Riding. Lube. Blown rim. Banging. Rubbing. Squealing. Juddering. Fingertip test. Pads. Hell, there's even "hosing it off after a wet ride" right there in the OP.

Do I have to spell it out?

I'd be happy if they'd just stop calling me "Shirley"!
Graham.

Underscore

UndercoverElephant wrote:

Underscore wrote:

I've just replace the rear wheel on my commuter (i.e. used when the weather is pants) after 5000-6000 miles so it doesn't seem too wide of the mark. My front, in contrast, is barely worn.

Really? Shirley, you should brake more with the front?

Indeed - I do. However, on my semi-rural commute, the front wheel flings all sorts of carp* from the road surface on to the rear wheel to the extent that , on a wet ride, it feels like the pads are faced with sand paper. Meanwhile, the front wheel has remained relatively clean. Hence, although I brake less with the rear brake, it suffers disproportionate wear.

_

* Grammar Nazi note: Deliberate misspelling - nothing fishy here

bikerwaser

Greg66 Tri v2.0 wrote:

This place is losing its touch. Almost a page down on a thread with "rim wear" in the title and not the slightest hint of a single entendre, much less a double.



<weep>



Come on, it's not that difficult. Friction. Riding. Lube. Blown rim. Banging. Rubbing. Squealing. Juddering. Fingertip test. Pads. Hell, there's even "hosing it off after a wet ride" right there in the OP.



Do I have to spell it out?

nice one Gregg66

LOL !

but we never Spoke about Valves, Tubes, Nipples(?) or Buckling under the Pressure .

what do you Sphincter that !

rjsterry

The other bit you are missing is that the rear rim tends to get a lot more dirt and grit sprayed up on to it from the front wheel, which increases the rate of wear. I've found the last year particularly abrasive, having comprehensively trashed a pair of RS10s in less than 18 months. BTW, if there's no wear indicator, you can get a good idea by putting a straight edge against the braking surface, but for more accurate measurement, take the tyre off and measure (with calipers) the thickness of the surface plus two cut pieces of spoke or other thick wire placed either side, then subtract the diameters of the wire

rolf_f

rjsterry wrote:

The other bit you are missing is that the rear rim tends to get a lot more dirt and grit sprayed up on to it from the front wheel, which increases the rate of wear.

Unless you run mudguards which has a huge impact on the amount of crap getting on the rear rim.

But anyway, this is nearer the point. It isn't so much about which rim and how much braking pressure you apply it is about when you are riding. If you ride on dry roads only, the rim wear will be negligible no matter how you brake. It is wet, dirty roads that kill rims and the solution to that is to just keep cleaning blocks and rims as often as possible when riding in poor conditions. TBH, I think that should really mean after every ride though I'm not quite that dedicated. But I do spend a lot of time cleaning the rims and pads of my Ribble (mainly because if I don't, and they are dirty, I always think of myself as deliberately sandpapering the rims everytime I brake which is pretty sobering!) and so far I reckon I've got about 8000 miles out of a pair of Khamsins with a lot of the rim wear groove still present.

Re concave braking surfaces. One point here is that if you are wearing a braking surface down, and your pads are centred on that braking surface, then they will wear a depression into the rim because the pads are not as deep as the rim itself. But that doesn't mean that the rim is bowing out due to weakening. So I think the caliper measurement that rjsterry mentions in the above post is far better than the straight edge method which could give entirely the wrong impression.

pitchshifter

Metal and stones embedded in your brake pads are your worst enemy for rim wear. I make an effort to check them once a week or so.

I had open pros , great rim in my opinion. Would be even better if they had a wear indicator..

Don't let this happen!

veronese68

Quite some thread resurrection. However, I can now look at this thread, sit back and say how much I like the discs on my new bike. 8)