I know each stack is different but this one seems particularly liberal in allowing things like subjective answers and incomplete answers. Some of these answers even receive upvotes. It seems to me that this decreases the value of all answers. Has this been discussed in any explicit sense or is it just the nature of the participants?
I don't know that there has been formal discussion either way, but as a smaller and lower volume stack there are only a few moderators involved, and only a handful of users who have reached a high enough rep level to take on moderator actions.
I notice two things frequently. First, as you mentioned, answers that are relatively subjective and short answers that should be comments. When you notice these please click the "flag" link and choose the appropriate message. One or more of the moderators will then take a look at the post. Because we recognize some allowable subjectivity in a lot of answers we may not delete it, but the flag is still useful because we can track who posts a large number of flagged content.
The other thing that happens on this stack frequently is that a perfectly valid answer will be posted as a comment. In these cases it would be appropriate to comment as well and ask the original comment poster to create an answer so that the content can be upvoted. It doesn't always work, but is a reasonable approach.
As Gary has mentioned, this is a smaller stack, and also much about cycling is subjective; answers to such questions are largely a matter of opinion.
Being low volume means that questions can be posted for hours without an answer, and can stay on the first page for over a day. On the main stack, or English, most questions get a (fairly definitive) answer within minutes, and are also quickly pushed of the front page.
So I observe an approach of well since nobody else has answered, I'll have a go. Any answer, or a partial answer, being better than none. Often this has the effect of triggering other answers in response.
Sometimes a short answer that could have been a comment is all that is required; one or two of your own answers are in this category. But longer more thorough answers almost always attract more votes. But because of the small user base, no answer has ever achieved Great Answer status.
The voting patterns are interesting (to me, at least). Question pages with 50 or so views commonly get 4 or so votes, spread between the question and the answers. But pages with thousands of views tend to get far lower voting rates per view.
So, on the one hand, the early voting tends to be quite generous, encouraging people who answer. But the later voting suggests something like meh, (s)he's got enough votes.
But the view of generous voting is also supported by the culture that we have very few downvotes, preferring to upvote other answers or leaving a comment. Looking at the voting figures for the top 50 users shows a downvote rate of about 1% or 2% of the upvotes.
The mouse-over for the vote buttons says
This answer is useful
This answer is not useful.
They don't say correct and incorrect.
So I think we tend to upvote answers that are useful, and downvote answers that are seen as wrong, rude/abusive or even dangerous.
To answer the question - I think it's due to the small size of the user base. We like to encourage new members, and also downvoters quickly become known.
I may be being over cynical but taking andy256's point further
"So I observe an approach of well since nobody else has answered, I'll have a go. Any answer, or a partial answer, being better than none."
I think their are a few users who subscribe to this ethos but also have a points mentality as well. They will answer any question very quickly with a poorly structured and not very comprehensive answer. I find the true answer is then teased out by other users in the comments.
Hydraulic brakes is a good example of this. There is a small knowledge base that understand and can answer questions, but always a proliferation of low quality answers, that the answer as often as not is go to your LBS.
There are a few users whose answers I value and others which I usually over look. Probably the reason I don't engage in the site as much as I did previously.