Hello,

I am considering building my own recumbent and was wondering what length crank arms people prefer. Basically do you prefer a crank arm that is longer or shorter than what you would use on an upright bike? Or does it make no difference?

Thanks,

I will probably have more questions as I get further into the build, so I will post them in this thread when I have them.

Consensus seems to be towards shorter, but those can be harder to find. Use what you have available, I wouldn't sweat it too much.

Consensus seems to be towards shorter, but those can be harder to find. Use what you have available, I wouldn't sweat it too much.

A difference of 5 or 10 mm is as good as no difference at all, but if you get really short ones, you will notice it, and once you get to like short ones, it's hard to go back to long ones. So, if you're buying new, look at the 'Bulletproof' BMX cranks, lengths as short as 140 mm and fit standard 110 BCD rings ("compact").

A difference of 5 or 10 mm is as good as no difference at all...

My knees would respectfully disagree w/ that. 175's (same size I used on the df) on the VRex caused significant pain, but 170's are just fine. And, yes, I did adjust the seat position for the difference in crank length.

SP

I use the same crank length for recumbents as I do for uprights. I've tried short ones, and find that my climbing suffers. I"m not a great climber to start, so I'd rather not place an additional liability on myself.

I also need a small front wheel. I would like something less than 16" or even 12" if possible. I have been searching for one but have not had much luck. The narrower the rim the better.
Thanks



I also need a fork for it where can I find them???

A difference of 5 or 10 mm is as good as no difference at all....

My knees would respectfully disagree w/ that. 175's (same size I used on the df) on the VRex caused significant pain, but 170's are just fine. And, yes, I did adjust the seat position for the difference in crank length.

Fair enough! Evidently, somewhere between 170 and 175 mm, you have crossed a point beyond which crank arms are so long that you can actually hurt yourself by riding with them. I think we can we agree, then, that 175 mm crank arms are really "too long" for you; and since the 170's do not hurt you, they are in the "acceptable" range. Further experimentation is required before we can determine your "ideal" crank arm length.

My own experience, based on riding them all in the last year, is that 140's, 152's, 165's, 170's, 172.5's, and 175's are all in the "acceptable" range, and that in that range, the shortest is closest to optimal. I have recently (yesterday) installed 127's on one of my bikes, but haven't ridden it very far yet.

I've done a LOT of riding with 140's, and I like them a lot; I normally maintain a cadence around 120 rpm (as far as I can tell without a cadence computer). Recently I started riding a recumbent, the Counterpoint Presto mentioned in another thread or two. It has 170's, and I'm out of the habit of using such long arms; after a couple dozen miles they give me a pain in the @$$! I'm changing them to 140 at earliest opportunity.

By the way, I'm 6' tall, wear 32" inseam pants.

I also need a small front wheel. I would like something less than 16" or even 12" if possible. I have been searching for one but have not had much luck. The narrower the rim the better.
Thanks



I also need a fork for it where can I find them???

Small wheels are constantly being discussed at the Folding Bikes forum.

I would not recommend a very small front wheel. The front wheel determines the comfort (handling, stability, etc.) of a bicycle far more than the rear wheel. Basically, the smaller the wheel diameter, the closer the tolerances in frame angles; where a quarter inch in fork rake, for example, makes little difference with a 27" wheel, it may be critical with a 16" wheel.

For a specific example: the ride of my folding bike (a Downtube Mini) is certainly acceptable, but if I put a small tire (such as a Primo Comet 16 x 1) on the rear wheel, and a really fat one (such as a Schwalbe Big Apple 16 x 2) on the front, the handling improves considerably.

You can definitely get narrow rims and high pressure, kevlar-belted tires for both 16" wheel sizes (305 mm = 16 x 1.5", or 349 mm = 16 x 1 3/8). The former is common on children's bikes and some folding bikes, such as mine. The latter was used on the old Moulton bicycles as well as some modern folding bikes, especially Brompton. The selection of tires is definitely better for 349's. The availability of rims and forks is much better for 305's. If you go with 305's you can salvage the fork (and even front wheel) off a discarded child's bike; money will get you one with brake mounts.

You can get rims and tires of an acceptable quality for 12 1/2" wheels, but they won't be high-pressure. Again, the best source would be a discarded kid's bike or scooter. The Mobiky folding bike uses this size.

Smaller wheels exist; the Pacific Carryme folding bike has 8" wheels, if I recall correctly, and fairly high pressure tires, so they must be available.

I, personally, would not go below 12 1/2 " and would probably prefer 16" or even 20".

Ok well I have rethought my design and I would like to use 16” narrow rims so I can put a narrow high pressure tire on it. Can anyone point me in the direction of a place to buy rimes of this size as well as the fork and tires to fit? I have had no luck finding a place that sells them.

Ok well I have rethought my design and I would like to use 16” narrow rims so I can put a narrow high pressure tire on it. Can anyone point me in the direction of a place to buy rimes of this size as well as the fork and tires to fit? I have had no luck finding a place that sells them.

Okay, here's a rim:
http://www.bikepartsusa.com/bikeparts/item/01-124247/rim-16_inch/Alex%2D%2D16x1%2E5%2C%2DX%2D101%2C%2D36%2DHole%2C%2D305x20%2C%2DSilver%2DAlloy%2DRim&category=rim-16_inch
and here's a tire to fit it:
http://www.bikepartsusa.com/bikeparts/item/01-136722/tire-16_inch/Primo%2D%2D16x1%2E35%2C%2DComet%2C%2DKevlar%2C%2D85psi%2C%2DSkin%2DWall%2C%2DBlack%2C%2DTire&category=tire-16_inch
and here's a fork:
http://www.bikepartsusa.com/bikeparts/item/01-79256/fork-16_inch/Pyramid%2D%2DMX%2C%2D16%22%2DFork&category=fork-16_inch

They don't tell you the dropout width of the fork, so I don't know about what hub to use.

But before jumping on any of those, I'd go to Craigs List, see if you can pick up a kid's bike with 16" alloy wheels; then you'll have the fork and the wheel, and all you'll need is a high pressure tire.

Okay, here's a rim:
http://www.bikepartsusa.com/bikeparts/item/01-124247/rim-16_inch/Alex%2D%2D16x1%2E5%2C%2DX%2D101%2C%2D36%2DHole%2C%2D305x20%2C%2DSilver%2DAlloy%2DRim&category=rim-16_inch
and here's a tire to fit it:
http://www.bikepartsusa.com/bikeparts/item/01-136722/tire-16_inch/Primo%2D%2D16x1%2E35%2C%2DComet%2C%2DKevlar%2C%2D85psi%2C%2DSkin%2DWall%2C%2DBlack%2C%2DTire&category=tire-16_inch
and here's a fork:
http://www.bikepartsusa.com/bikeparts/item/01-79256/fork-16_inch/Pyramid%2D%2DMX%2C%2D16%22%2DFork&category=fork-16_inch

They don't tell you the dropout width of the fork, so I don't know about what hub to use.

But before jumping on any of those, I'd go to Craigs List, see if you can pick up a kid's bike with 16" alloy wheels; then you'll have the fork and the wheel, and all you'll need is a high pressure tire.



Thanks,

I have seen that site. I would like a fork that has mounts for V brakes already installed.

Any ideas??

Thanks,

I have seen that site. I would like a fork that has mounts for V brakes already installed.

Any ideas??

A number of cheap folding bikes, such as the Kent Ultralight
http://www.bikemania.biz/Kent_Ultralight_16_Magnesium_Folding_Bike_p/kent_61688.htm

and the Chrysler
http://www.overstock.com/Sports-Toys/Chrysler-16-inch-Folding-Bike/2968490/product.html

have forks like that, and occasionally you can find one of these on sale for like $90, shipping included. Right now, unfortunately, I'm not finding anything like that.

More expensive folding bikes have them too, of course; perhaps you can get a replacement fork from Dahon, Downtube, or BikeFriday?

Another option: forget about V-brakes entirely; get a drum brake hub, such as a Sturmey Archer X-FD,
http://aebike.com/page.cfm?action=details&PageID=30&SKU=HU2202
or a X-FDD (which also has a dynamo built in). I have an X-FDD, and it's great.

There are definitely kids' bikes with 16" wheels and v-brakes; but again, I don't find any on the internet now.