FWIW
I used to run a filter test lab. The pressure drop across a functioning filter is quite low- so low that a filter length difference is of no practical consequence to that pressure drop in operating conditions.
Filters plug exponentially, not linearly. Pressure drop increase is moderate until the filter has accumulated at least 3/4 of its maximum dirt load capability, then goes up at a rapidly increasing rate. All other things equal, a bigger filter can hold more dirt but this is also not of much consequence in normal use because it takes so much dirt to plug a filter there is no chance you'll get to that point with reasonable service intervals on a bike with an intact air filter and closed crankcase.
BMW K wedge bikes have a couple factory filter sizes available. The longer one is a bloody nuisance to use so I use the short one. The reason they have the long one available I'm told was due to a couple bikes with clutch failures dumping too much clutch crude into the oil for the smaller filter but that is not a typical problem. Not relevant to R bikes with their separate tranny, either.
Re those cheap Frams- I don't like cardboard end caps either but my biggest objection to that filter is its greatly reduced area of filtration material which of course equally reduces its dirt load capability. All you need to understand that is to count pleats- its a cheap piece of junk all the way around but can still do an OK job at protecting an engine that gets reasonable service intervals, as long as it doesn't come apart.
My own filter choices come from those that a filter maker lists for the vehicle in question. All the makers have test labs and engineers for a reason and I don't second guess guys who do it for a living and have to stand behind their published info.
I used to run a filter test lab. The pressure drop across a functioning filter is quite low- so low that a filter length difference is of no practical consequence to that pressure drop in operating conditions.
Filters plug exponentially, not linearly. Pressure drop increase is moderate until the filter has accumulated at least 3/4 of its maximum dirt load capability, then goes up at a rapidly increasing rate. All other things equal, a bigger filter can hold more dirt but this is also not of much consequence in normal use because it takes so much dirt to plug a filter there is no chance you'll get to that point with reasonable service intervals on a bike with an intact air filter and closed crankcase.
BMW K wedge bikes have a couple factory filter sizes available. The longer one is a bloody nuisance to use so I use the short one. The reason they have the long one available I'm told was due to a couple bikes with clutch failures dumping too much clutch crude into the oil for the smaller filter but that is not a typical problem. Not relevant to R bikes with their separate tranny, either.
Re those cheap Frams- I don't like cardboard end caps either but my biggest objection to that filter is its greatly reduced area of filtration material which of course equally reduces its dirt load capability. All you need to understand that is to count pleats- its a cheap piece of junk all the way around but can still do an OK job at protecting an engine that gets reasonable service intervals, as long as it doesn't come apart.
My own filter choices come from those that a filter maker lists for the vehicle in question. All the makers have test labs and engineers for a reason and I don't second guess guys who do it for a living and have to stand behind their published info.