I need 165mm or 160mm cranks for my shorter legs.
I don't know if they are available for the Dahon P8.
Also, I'm in the market for a new folder. Are shorter cranks available
for Downtube folders? What about Brompton/Merc and Bike Friday?
You can put shorter cranks on any bicycle so long as it matches the interface type of your bottom bracket (e.g. square taper BB requires square taper cranks) That said you can always change the bottom bracket too if necessary.
What however you might be asking is - Do any of these bicycles come with the option of a shorter crank at time of purchase? (Rather than buying the bike and then upgrading the crank and maybe the bottom bracket later).
Dahon bikes come standard with 170mm cranks so far as I know.
Downtube... not sure if Yan does customization.
I also know little about Brompton/Merc
Bike Friday definitely can customize your bike for you - BF just costs a lot more I think.
(so the question is if it is cheaper to get a Dahon/Downtube and upgrade after the fact, or get a Bike Friday and get them to do it from the outset).
You might also speak with your local dealers, perhaps they will offer to sell you a bike + the upgrade for less cost than if you were to do both separately?
Rarely needed. The Speed P8 cranks are pretty good, so they will be expensive to replace unless you go with a different crank. That said, if you have knee pain, have very short legs, or have pedal strike on turns, it might be worth it.
I use 165mm cranks only because I had knee problems. (I tend not to have pedal strike problems b/c I used to race and am used to keeping the pedal up on turns.) My partner uses them b/c she is smaller. We both use Shimano 105 cranks, which we found for around $20-40 on Nashbar. That said, you have to make sure that you get the chainline right. Look up the specs for the Speed P8 and try to match the BB axle length (won't be exactly the same, but very close). Alternatively, you can look on Sheldon Brown's site for calculating the chainline and try to match it more exactly with spacers.
Almost all stock bikes come with 170mm or 175mm cranks. O/w you have to do a custom order.
I'm 5'-8" with a 30" inseam, and swapped out the stock 170mm cranksets, OEM chainring, and *** bottom brackets and pedals on my 3 Bromptons. All now have 165mm TA Specialites cranks, chainring, chainguard and bottom brackets and MKS Ezy pedals. I like the difference. If you decide to buy a Brompton, post me and I can give you the specs for the bottom bracket spindle replacement and chainline info. Good luck!
It is true that most bikes come with 170's stock. But it doesn't make sense to me. In the old days, when all bikes were dreadfully overgeared, most bikes came with 165's. Now that we habitually spin in lower gears than was fashionable 30 years ago, we use longer crank arms.
I just got back from a 18 mile ride or so; I had a meeting down at Brooklyn College, and it's such a nice day I rode back to the office instead of taking the subway. Average speed, through NYC traffic, around 15 mph. I'm a little hot and sweaty now, but knees are not sore at all!