How-To/Mechanics: NJS sizing

Hey there, im not sure if this is a stupid question, but i was wondering about the sizing of NJS track parts. Ive read on Sheldon's site that NJS was a way for making part interchangeability in Keirin racing easier, which would imply that there was a universal sizing among the parts, but from what ive seen different NJS frames, even different years of the same frame, have different seat post diameters. How does this work? is there a universal size? Any interesting info on NJS mechanics would be appreciated. Again sorry if this discussion demonstrates my ignorance.

Posted By: iron jaidenThe sizing should be all the same (68mm BB, 27.2 seatpost, 120mm / 100mm hub axle length, etc..)

120mm rear hub axle? I was under the impression that keirin rear hub spacing was 110 (an older track standard, which I guess was current in 1957, when NJS formalized their standards), while modern track spacing (used everywhere else) is 120. Phil Wood's keirin hubs are 110; I'd guess that would have to meet the NJS standard, otherwise there'd be no point in making them.

According to Wikipedia, NJS bosses keirin in Japan, but has no authority over keirin events outside that country. Which means that, if someone wants to hold an event in the US on non-NJS stamped equipment (120mm hubs, aluminum frames, 16-spoke radial wheels, saddles wide enough for a Westerner's backside), there's nothing to stop them aside from the willingness of spectators to show up.

Im not any expert on njs frames, but I have owned 3 of them now. The only thing that I have come across that is different in sizing was the rear hub spacing on the dropouts. But everything else was the same size.

Posted By: eaglerock

Posted By: iron jaidenThe sizing should be all the same (68mm BB, 27.2 seatpost, 120mm / 100mm hub axle length, etc..)

120mm rear hub axle? I was under the impression that keirin rear hub spacing was 110 (an older track standard, which I guess was current in 1957, when NJS formalized their standards), while modern track spacing (used everywhere else) is 120.Phil Wood's keirin hubs are 110; I'd guess that would have to meet the NJS standard, otherwise there'd be no point in making them.

According toWikipedia, NJS bosses keirin in Japan, but has no authority over keirin events outside that country. Which means that, if someone wants to hold an event in the US on non-NJS stamped equipment (120mm hubs, aluminum frames, 16-spoke radial wheels, saddles wide enough for a Westerner's backside), there's nothing to stop them aside from the willingness of spectators to show up.

Yep sorry you're right. I'm just used to typing 120 for track axle length automatically. I meant 110 rear.

all my seatpost sizes have been the same, 27.2,

The frames that I have owned have been, 1 bridgestone, 1 eimei, and presently my uno. the eimei had the 110mm rear spacing, and the other 2 have been 120.

Also there is two size of dropout opening (slot) in NJS standard, 11mm and 12mm. Many earlier Japanese rear hubs has two flat ends on the axle. I'm skeptic about 110mm rear spacing on a Japanese frame because they all use a 109mm BB shaft and a 68mm width BB shell. I've seen old Cinelli's track frames with a 65mm width BB shell and 110mm rear spacing.

The variations you will basically see in NJS frames will be in:

seatpost sizing: 27.2, 26.8, 27.0

two (2) dropouts types:
a. 110x9 (rear) 100x8 (front)
b. 120x10 (rear) 100x9 (front)

Also, the builder's have to be certified under njs.
Geo- the only area that I have seen variations in NJS frames have is in the seatube angle and I believe (2) options are allowed.
components also have strict guidelines in order to receive the the njs stamp, all must be silver with the exception of chains (black (dark navy),silver and blk/gold.