Stiffness is the primary reason for USD forks, unsprung weight is a secondary reason

the reason you don't see many non cartridge USD forks is cause cartridges were an advancement in fork technology before someone decided to turn then upside down, they first appeared in the dirtbike arena before making theire way to the street

USD forks are stiffer but unsprung weight is increased because the dense part of the fork is now at the bottom.

Materials technology could overcome the stiffness advantage that USD forks have but manufacturers know that USD forks sell bikes due to the aesthetics so there is no incentive.

Exactly. Ride, say, a GSXR600 K2 vs a 750 K2 and you wouldn't get off thinking "Hmm, those RWU forks are much less stiff than the USDs", or for that matter "Wow, you can really feel the difference in unsprung weight!"... Perhaps if you were converting for race use, or a really, seriously demanding rider, but I guarantee most of us couldn't tell the difference. Both good, effective front ends.

Precisely, Curium well done I'm glad somebody else is aware of this too.

As said before: Any of the USD forks you are likely to fit to an SV, (any that you'll find on a road bike actually), do not have a better unsprung weight ratio.

I've had a think and can't see why usd is better than rwu. Surely quality and setup are far more important.

must be a fashion thing.

Absolutely. But it's sort of like radial master cylinders- fashion dictates that the best bikes have to have them, and so the most development goes into the fashionable part, and the best price is taken for the fashionable part. So, frinstance, Brembo don't make a commercially available top-end conventional master cylinder, even though it'd work perfectly well, because less people would buy
it. (most of the improvements that people put down to radial master cylinders actually come from the fact that they tend to be better built, and better designed.

So there's a sort of self-selection here, the fashionable parts do tend to be better than the unfashionable.

Not necessarily, USD do have some advantages, the design allows unquestionably better stiffness, (of course this is only any good if the chassis to which they're fitted is stiff enough to take advantage of that, not all are), however as a suspension medium they will have a poorer ratio of unsprung/sprung weight unless something quite exotic materials wise is used for the slider, and it never is.

Yes, but depends on the use to which the bike is put. Where stiffness is important, ie racing, there'll be USD.

Incidentally, the first telescopic forks were what we would now call USD, so really SVs have USD forks fitted as standard - Northy's fitted RWU forks to his bike... :lol:

Incidently...

Why the original switch from USD to RWU? My dad rode in his youth and all his bikes were USD apparently, then RWU came in, now back to USD...

Any idea's?

Stu