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When exploring a braking system, I noticed with surprise that they tested their brake actuations to match the 1000 mile quality life expectation of a comfort bike. This seems to imply that this is the expected design life.

Surestop brake life

Since the page is oriented towards bicycle manufacturers, can we imply that 1000 miles is the expected design life of mid- and low-end bicycles? The lab itself seems rather legit:

ACT lab

This does hinge on what "quality life span" and "comfort bike" mean.

tl;dr: Is there evidence that the industry believes that 1000 miles is the reasonable lifespan of a low- to mid-end bicycle?

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    Most bikes are ridden probably under 100 miles over their lifetime before they're stuffed in a garage. Also, quality life span might just mean til you need some service -- new chain, brake pads, etc. – Batman Apr 20 '17 at 15:36
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    This is by no means a definition but my understanding of "quality life span" is the period before things start to deteriorate noticeably. The may need replacing or more likely just tweaking. Note that Halfords (a shop that sells mostly cheap bikes in the UK, as well as car parts) offers a free 6 week service (tune-up) on all their bikes. They also sell road bikes for £250 (about $320). In 6 weeks you could do a decent fraction of the 1000 miles without trying too hard. – Chris H Apr 20 '17 at 15:37
  • I wonder what you mean by mid/low end -- I made an assumption in my previous comment, but if you consider expected chain lifetimes that would mean that a chain lasted several bikes. As another pointer I have a <$1000 hybrid with 25-30 thousand miles on it which is still going strong after normal component replacements (and a new back wheel). – Chris H Apr 20 '17 at 15:40
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    Mid- low- end: I extrapolated from the bikes that the SureStop is on, which seems to be sub-$500 bikes. Many might consider these to be all low-end. Another translation of "comfort bike" would be appreciated. It's not BSO but the level above that. – RoboKaren Apr 20 '17 at 16:00
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    The surestop looks like a product that's aimed at people who don't ride bikes at all, so 1000 miles is probably enough. – ojs Apr 20 '17 at 18:59
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have a look at this : https://en.wikipedia.org/wiki/Design_life

and this : https://en.wikipedia.org/wiki/Mean_time_between_failures

It is all a matter of statistic and probability of failures in the lifetime of the component.

This means that the component should have a normal life of about 1000 miles before a certain percentage of failure (can) start appearing on a number of components.

Another example, my washing machine has a design life of about 14 years [1]; before that the number of failure should be minimal according to the manufacturer, after 14 years, the number of failures should start to statistically increase.

It does not mean the component will fail after the design life, but that the probability of failure increase.

[1] http://homeguides.sfgate.com/expected-lifespans-washing-machines-67293.html

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Since that search term "quality life span of a comfort bicycle" does not come up in google I would conclude it is not a standard.

Just take it at the word.

In 2013, ACT Lab began testing SURESTOP for a few bicycle brands looking to use the technology on their bikes.

  1. Durability testing – tests were run for 1000 miles and 5000+ brake actuations, which historic labratory testing has shown to represent the average quality life span of a comfort bicycle. The SURESTOP did not show any signs of failure during this test.

Note they misspelled laboratory.

More than 1 brand was OK with only testing "1000 miles and 5000+ actuations". Does not mean they expect it to fail on 1001 miles and 5000++. If it passes there is no evidence it will fail at 1001 miles.

I think that number more reflects the BSO market than SureStop. That is a believable number for BSO (to me).

SureStop is using it on their mid range bicycle so clearly they expect it to have a lifespan more than 1000 miles or they would fail in that market. Another market is rental which is a high mileage market. Not saying it will take a lot of miles but clearly it would not be in their best interest to design for 1000 miles. Even if a BSO is good with 1000 it seems like it would be their best interest to test at a higher number. If wear out a brake pad would fail the "quality life span" then that would explain 1000.

The lab may have historical data that they do see failures on low end bikes in that period.

Most likely scenario is marketing is looking at the low end market and determined that most of those bikes are not used more than "1000 miles and 5000+ actuations". How cheap can we get and hit that mark.

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Warning: speculation ahead.

I think that those lifespans are more likely to be a "minimum aimed lifetime" rather than something else.

What leads me to think that is that lab testing is costly, and some tests are also verytime consuming. Take stress-testing (testing for material fatigue) for exmple. Flexing a component repeatedly until it fails. My guess is that those tests must be performed on a statistically significative sample. You either build several machines to test several prototypes at once or do it one by one. Im also assuming that testing for 2000 km needs the double as to test for 1000 km.

Taking that into account, there must be a certain point of equilibrium between how much to test something, and how sure to be of the spected lifetime of a design, o a production batch. This is much more important in low to mid priced items, because they are sold in higher volumes, so a tiny cost saving gets multiplied by huge quantities.

Higher priced items on the other hand tend to be more exclusive, much less units are sold, but also, all that testing is even part of the marketing of the product, and the target market is likely to "appreciate" all that testing and quiality guarantees, i.e. it's more sensible to test these products toward higher extents.

That being said, I doubt that there is something "conspiracy theory" styled argument towards purposefully designing a mid-range or low-range component to fail after a defined time/usage span. That would add up to the design and development stages.

  • I don't think this is production testing. It is a sample set for bike brands considering the product. – paparazzo Apr 21 '17 at 18:17

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