Rear rim's just cracked.

[Ming the Merciless]

Putting a wet dirty Brompton in the boot of a car will not have helped matters.

 

[Kell]

ALL rim braked small wheels have a shorter life than 'full sized' rims.
Bromptons used to be known for lacklustre braking. Fitting a more aggressive block sorted that, but at the expense of wear on the rim. My badly treated commuter on 700C rims managed about 4500 miles before the wear indicator showed a new rim was needed. As 10 out of my 16 mile each way commute was on little used country roads, and 3 was on A roads, the real wear took place on wet days in town.

As I say, I'm going to chalk it down to experience. I'm a little better with cleaning since this happened, but I'm still convinced that cycling around Hyde Park probably contributes to the excessive wear as there are sand horse tracks all around it. Pretty sure that the fine dust blows over onto the cycle lanes and gets flicked up, mixed with the oil and turned into a grinding paste.

It's very hard to prove what constitutes excessive wear, but I'd say that all things being equal, the new rim should have worn through much more quickly. As I was doing an additional 6 miles daily and a lot more severe braking. Yet it lasted more than twice as many miles/years and while showing signs of wear, was certainly not down to any wear indicator.

 

[Fields Electric]

Just for the record. Mine is on 4 years and 6500 miles and the rear rim is ‘going soft’ on the drive side. That means I can dint it with a flat screw driver. The drive side is worst because it catches the oil from the chain. This collects dirt, which turns into a grinding paste. I clean the rims when they look grey. I also use brake pads that are designed from aluminium rims. The blocks do last about 1800 miles and not cheap.

 

[u_i]

Just for the record. Mine is on 4 years and 6500 miles and the rear rim is ‘going soft’ on the drive side. That means I can dint it with a flat screw driver. The drive side is worst because it catches the oil from the chain. This collects dirt, which turns into a grinding paste. I clean the rims when they look grey. I also use brake pads that are designed from aluminium rims. The blocks do last about 1800 miles and not cheap.

You normally measure the rim thickness with an inexpensive dental caliper, looking for the places where you get the lowest readings. You should absolutely never go below 0.5mm and many people recommend not even going below 1.0mm. I usually push down to 0.7mm.

 

[rogerzilla]

I wore out a front 26" rim (the rim that isn't constantly sprayed with gritty water) in 18 months of commuting, half of it on country lanes. It was a fixie, as a rear rim with a brake would have worn out many times faster.

A rear 16" rim will not last long on mucky roads. That type of wear indicator groove does tend to encourage splits, unfortunately.

 

[Illaveago]

Ah! Finally an answer to the question in my head ! So the groove running round the rim is the wear indicator ? . Handy of them to put in a weak spot from a split to follow !
So if you go beyond the limit of the wear indicator the rim should look perfectly alright!

 

[u_i]

Ah! Finally an answer to the question in my head ! So the groove running round the rim is the wear indicator ? . Handy of them to put in a weak spot from a split to follow !
So if you go beyond the limit of the wear indicator the rim should look perfectly alright!

The rim wear indicators are usually quite conservative and wear is usually not uniform. This is why it can be good to measure after long-term use of the rim. Some rim manufacturers use the reverse: a hole begins to show once the wear gets to be excessive.

 

[keithmac]

My GTECH with 700c did over 6,000 miles of commuting with virtually no cleaning most of the time before the wear groove (sp?) showed it was time for another rim, Clarkes brake shoes.

 

[Kell]

Well, seeing as this thread has made a resurgence, I may as well update.

Still on the replacement wheel, and up until the pandemic, was still doing just under 2,000 miles a year. And in much harsher conditions than when the original wheel cracked - my daily commute includes a 40MPH downhill section (which I'd only just started doing at the time of the split), so I'd have thought if that wear was 'normal' then I'd be replacing it every 6 months.

As it is, my Strava log indicates that I've now done around 10,000 miles on the Brompton and the rear wheel looks OK.

As I maintained all along (and still do) that original wheel wore out much quicker than it should have done.

 

[Kell]

I was just looking for this thread to point someone else to, but thought I'd update that the replacement wheel was going strong up until a month or so ago, when I replaced the lot as the hub sounded awful. Grinding and general unpleasant.

Still not got around to fixing the old one, but have bought the parts. As I lost some of the bearings when I took it apart to see how it worked. D'oh.

What I would say is that I still think the original wore out too soon. After this thread, I started cycling that hill every day and the replacement wheel lasted a further 5,000 miles and didn't show any signs of wearing through...

If that post was true, then the fact that my current wheel has just gone crack means it lasted around 5,000 miles too.

Currently in the shop for a rebuild.

This time will be slightly easier to track as I've now downloaded that 'mainTrack' app that someone recommended on here.

ETA - because I know the rough dates, the app can calculate the distance retrospectively.

I overestimated it somewhat - it was actually 3,400...

 

[presta]

What are peeps thoughts on softer pads than the standard issue such as Koolstop Salmons to reduce rim wear?

As it is, my Strava log indicates that I've now done around 10,000 miles on the Brompton and the rear wheel looks OK.

I've had about 20,000 miles out my Mavic A719s, with fairy abrasive Shimano M55/T blocks. That would be equivalent to about 12,000 miles on a Brompton with smaller wheels.

 

[Fab Foodie]

I've had about 20,000 miles out my Mavic A719s, with fairy abrasive Shimano M55/T blocks. That would be equivalent to about 12,000 miles on a Brompton with smaller wheels.

Blimey - post from the past!!
I have Kool Stops (Salmon Front/Black rear) on all my bikes now, Broms and 700c wheels, wouldn't change now on stopping performance...no idea about rim wear though!

 

[ExBrit]

I have to agree with the OP. I would not expect the rim to fail, even if filthy and gritty, in such a short time. But it's not the time, it's the miles and it does sound as if the OP puts more miles on than I do. Cleaning the bike and lubing the chain once a week will increase the MTBF. It's 15 minutes well spent. If you ride a lot and in bad conditions it's 15 minutes even better spent.

 

[berlinonaut]

But it's not the time, it's the miles and it does sound as if the OP puts more miles on than I do.

It's miles, riding style, cleanliness of the bike, weather, type of breakpads, weight of the rider, speed, surface you are riding on, anxiety of the rider (how often does he break?) and probably a couple things more. One of those is obviously the type of rim itself. Also, it is quite typical that the rear rim cracks earlier often, for one as it is typically grittier than the front and second a lot of riders use the rear brake intensively on the Brommi. So a lot of things that influence the lifespan and a lof of influence of the rider.

Cleaning the bike and lubing the chain once a week will increase the MTBF. It's 15 minutes well spent. If you ride a lot and in bad conditions it's 15 minutes even better spent.

I do have my doubts that lubing the chain increases the lifespan of the rims but who knows. At 3.400 miles @Kell is at the lower (but not the lowest) part of the distribution in terms of rim lifespan. The majority seems to be between 10.000km and 25.000km, with a peak at around 20k km. However, sportier riders with a harsh riding style are typically way lower than that.
If I was @Kell I'd probably give the Sun CR18 a try - it is a dog to put tires on but rumors say it would be way more longlasting than other Brompton rims.
silver
black

 

[ExBrit]

It's miles, riding style, cleanliness of the bike, weather, type of breakpads, weight of the rider, speed, surface you are riding on, anxiety of the rider (how often does he break?) and probably a couple things more. One of those is obviously the type of rim itself. Also, it is quite typical that the rear rim cracks earlier often, for one as it is typically grittier than the front and second a lot of riders use the rear brake intensively on the Brommi. So a lot of things that influence the lifespan and a lof of influence of the rider.


I do have my doubts that lubing the chain increases the lifespan of the rims but who knows. At 3.400 miles @Kell is at the lower (but not the lowest) part of the distribution in terms of rim lifespan.
If I was @Kell I'd probably give the Sun CR18 a try - it is a dog to put tires on but rumors say it would be way more longlasting than other Brompton rims.
silver
black

Obviously I was referring to MTBF generally. I think getting into the mindset of cleaning your bike regularly and proportional to usage is a good thing. I've been riding as an adult for 30 years and only figured this out maybe ten years ago.

So am I right in understanding that newer Brompton rims have a black line that appears as a wear indicator?