numptie question about rim wear

Ranger

New Member
Location
Fife borders
After reading a few posts about replacing rims I was putting my bike back on the car rack and felt a ridge on the front wheel just as the tyre bead joins onto the wheel. The question is how do I know I need to replace a wheel rim??? The wheel is about 4 years old and did about 70 miles a week for 2 years and has done 125 miles a week for the last 6 months. All a bit of a mystery as I have never done the sort of mileage I have in the last few years.
 
Location
Leicester
for me it was when my rims felt a bit concave due to rim wear. Some rims I believe have a wear indicator - a groove which helps identify when rims need changing, apart from that I can offer no more scientific a basis for when to replace rims - I'm sure someone else will help though....
 
Rim wear is a difficult area, you want to replace the rim a few minutes before catastrophic failure but how to tell when it's about to occur is tricky. The most spectacular example of brake pad wear induced failure was whe a colleague of mine was pumping up a Brompton wheel off the bike with a track pump. He got close to the recommended pressure when the whole side of the rim flew off with a bang and flew across the room. Quite spectacular but not the kind of thing you want to happen on a fast corner surrounded by traffic.
Brake wear can be influenced by many factors, the most common cause of accelerated wear is when brake blocks are used for too long. Over a period of time the surface of the block will pick up bits of grit and specks of aloonyman from the surface of the rim. These, now super abrasive, blocks will devour the brake track in a matter of a few weeks. Dirty bikes are more likely to suffer from this. The very worst thing you can do to a rim is leave the brake blocks to wear down to the steel backing plate. OW!! That desperate scraping noise is the rim dying.
Old blocks with some life left in them can be made rim safe by being sanded or filed down. Lay the file on a bench and run the block flat on to keep the surface nice and even. Clearly its much cheaper to replace blocks than to replace rims or complete wheels.
Entry level bikes are more likely to suffer premature rim wear because they use cheaper aloonyman. Small wheeled bikes suffer because theres less material there to wear out. Bromptons seem to suffer because their owners often dont clean them, they ride around for ever with a lovely abrasive soup on the rims and are taken by surprise when their rims fail.
Brake wear indicator tracks are a mixed blessing, most people dont know they are there for a start but in my view cutting a groove into the brake track is simply removing material from where you actually need it most.
So to sum up, keep your wheels clean, resurface or replace your blocks regularly and when replacing rims get the best that you can afford. Hard anodised (or even ceramic coating, yum) lasts very much longer than cheapo 2000 series aluminum.

In answer to the OP. I dont know if your rim is worn out because I cant see it. Sorry. Your LBS will tell you.
 
OP
R

Ranger

New Member
Location
Fife borders
Thanks for your help everyone. I understand you cannot tell me how worn my hubs are and for clearing up that realistically I can't either. Trip to the bike shop in order, I might be paranoid but I don't remember the ridge being there before.

Mickle - I'm afarid I am guilty of just about every poor maintenance sin you have ever mentioned but am learning that bikes need to be clean(ish):blush: to work properly, it isn't just to look pretty
 

biking_fox

Veteran
Location
Manchester
One tends to wear the back rim more substantially than the front - because you brake more with the back brake. If you can feel a notable ridge on the front check the back!

If you see a crack running around the rim even if it's only short they are definetly work way too thin and shoudl be replaced PDQ!
 

Chris James

Über Member
Location
Huddersfield
That depends on whether you brake more with the front or rear brake! We've had this before. Sheldon Brown (and me) recommends favouring the front brake.

(A bit off topic I know)
 

HJ

Cycling in Scotland
Location
Auld Reekie
Chris James said:
That depends on whether you brake more with the front or rear brake! We've had this before. Sheldon Brown (and me) recommends favouring the front brake.

(A bit off topic I know)
I find I tend to wear out the front pads faster as well.
 

fossyant

Ride It Like You Stole It!
Location
South Manchester
Back pad man me as it's a slower braking - front brake man is the last minute sort in a car :biggrin:

Difficult to tell on the rim wear - I have, and have just stripped down (for parts) an old set of Shimano 600 hubs with old Mavic MA40's that expired years ago, as the rims were thin enough to crack through the side wall in - but as that appeared they were shelved....good rims though !

Rim wear indicators help, but do check the condition of the rim on a regular basis, not just for wear, but impact damage, or out of true.
 
OP
R

Ranger

New Member
Location
Fife borders
Hairy Jock said:
Those of us who only work there, not live there, can only just about afford to replace the rims...:biggrin:
Live in Inverleith Place, I don't think so!! I think the new rims/wheels could be my Christmas present from the wife after buying the new pedals and shoes last week.

As for my lbs, I tend to use Sandy Wallace Cycles in Inverkeithing and think they are OK but am willing to take on any suggestions of other shops for north of the Forth.

Update:
Went to LBS and they took one look at the wheels, gave me a worried look and suggested that perhaps it was time to replace them as concave rims apparently aren't a good idea. I should be the proud owner of a new pair of handbuilt wheels between Christmas and New Year.

Thank You Mrs Ranger
 
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