lightweight bmx bb (mtb content)

[W W Biffta]

this is probably off topic, but im looking thinking of getting a pair of gusset pygmy r cranks, which use a 36t 19mm axle, and that is closer for me to bmx than mtb.
point is these cranks are made of reynolds 853, weigh in about 480g for the arms, but the bb they suggest for it weighs like 250g and another 250 for a steel axle, making the whole setup almost a kilo and the lighweight arms a bit of a waste.
i guess what i really want is the pygmy r arms with isis fit, but they dont make em
so im wondering is 36t 19mm a standard form? how hard might it be to find a lighter bb and axle, or is 500g about average?

 

[perry]

pretty sure profile has more splines

i think reanimation has gussets

am i right in thinking you will be using the euro cups for mtb use ?

http://www.gussetbikes.com/gusset/produ ... ?id=BBGUXE

the weight will be in the steel cups . i have both alloy and steel cups and im certain the outer diameter of the bearing is the same . if i remember in the morning ill weigh them both so you know how much weight you can lose by getting alloy cups

looking at it where did you get 36t ?

the arms are the same 48 spline as profile and many others . so you could get one of these instead

http://www.profileracing.com/profilerac ... oductid=62

about £80 from memory

so

reynolds arms
titanium profile axle
some self extract bolts ( not sure what thread profile use in the axles )
alloy cups with correct cartridge bearings for 19mm axles
the tube spacer so you dont overtighten the bearings
spacers for chainline
spider for 110 bcd or if your using a single ring might as well use a bmx one ( might need a top hat washer )

you will have flex free cranks with adjustable chainline and easilly replaced bearings . i plan on going back to using primos when money allows ( alloy arms with a ti axle option )

 

[W W Biffta]

cheers man just the info i was hoping for. yeah will be euro theaded cups.
the number of splines i got from the ebay ad i first saw the arms on, said 36t, but i see the pygmy 2 arms he also had are 36t so proably he just copied the blurb. 48t will probably make it easier anyway, i seen a guy on ebay.com selling those ti axles.
0 flex is what im after, dont mind carting around a couple of hundred extra gram if i can get it down that to much, sounds like its doable. just seemed really odd to put the effort into making light arms and not have a bb/axle to match. all the mtb specific steel crank setups i seen are like 1kg plus.

 

[perry]

my alloy cups are 91g and the steel ones are 127g both with bearings

the difference in weight is certainly noticeable just by holding them

with bmx cranks they need a strong axle . there are guys who snap square taper axles launching out of the gate on a track so its an area people want strength . the arms will have an element of rotating weight so losing weight there is a big benefit ( ive even seen broken steel tubular arms ) but for mtb use they will be fine . with the bottom bracket so low and central in the bike a touch of weight isnt as noticeable as other parts of the bike