Smaller 5-speed MTB cogs

A question about : Smaller 5-speed MTB cogs

I have an old Raleigh Triton Firejet 10-speed MTB which I commute 12.5 miles on. It must be about 20 years old; but I'm hanging on to it as all of its disadvantages will only make me fitter!

It has a 14-28 rear hub, and the largest crank gear has 48 teeth.

On downhill sections I'm limited to about 32mph because I can't physically move my feet any faster, so I want to change the gear ratios so I can go faster.

Is there such thing as a 5-speed screw-on type hub with a smaller gearset than 14-28?

Failing that, is it viable to upsize the crank gears?

Best answers:

• 32 mph on a 20 year old MTB while commuting isn't fast enough for you!. How fast do you want to go?. How good are the brakes?.
• Brakes are reasonable, roads in question are mostly NSL; the ones that aren't have better discretion applied! I'm a generally slow & high-torque pedaller and feel as though I could go faster with a couple more gears down these hills.
  From what I can gather, the old screw-on type cassette hubs don't have (won't physically accommodate?) cogs with fewer than 14 teeth, regardless of number of gears; and MTB crank gears of more than 48 teeth also seem to be non-existent.
  Are these reasonable assumptions, or is someone aware of an item that proves either wrong?
• If you want to go faster maybe you should get a road bike. The bike you have wasn't intended for high speed even when it was new and I suspect finding the parts you want will be almost impossible. Alternatively you could just work on increasing your cadence which won't cost you anything.