my diy 30 tooth 104bdc chainring

[ovwok]

Made mine own 30 tooth steel chainring for my XXIX dingle.



kind of steam punk looking but works great.



30t #40 ansi blank

[ovwok]

Run it on my dingle setup 26/22 low 30/18 high,same chain length. when I get to the top of a climb flip the bike over, open the quick release, raise up the wheel (vertical dropouts) and drop the chain to the 30-18 rings and ride on.

[zaskaranddriver]

Holymoly those are low gears. Sounds like some serious climbing. Nice work there!

[cdn-dave]

sweet, nice work!

where did you source the blank?

[ovwok]

sweet, nice work!

where did you source the blank?

McMaster Carr, $26

Its over 1/4" thick, after i found the center I bored a .750" hole in it and mounted it in the lathe on a 3/4" bolt with a center drilled in the end for support.
(note the live center in one of the pics).
I then shaved it down on both sides.
The holes are threaded 5/16 fine thread.
The bolts have a little .388"x.05" shoulder cut on them with a part-off tool
You have to file a bevel on the crank spider for chain side-plate roller clearance.

let me know if you need some dimensions because it not cut from the center line of the sprocket.

[ovwok]

Holymoly those are low gears. Sounds like some serious climbing. Nice work there!

Yes there are some grinder climbs around the San Fernando Valley.
Some are 14-26 percenters. You have to learn to say "shut up legs".

[AnonymouseTech]

Sorry for offtopic but I've been looking for something like this but why don't any companies make 30t x 104mm chainrings readily available?

[jetboy23]

Sorry for offtopic but I've been looking for something like this but why don't any companies make 30t x 104mm chainrings readily available?

In general, i think its a clearance issue. The spider for 104bcd is usually wide enough to interfere with the chain on the smaller chainrings. I think the groove/low point of teeth on my e.13 32t ring is right where my spider mounts on my Sram AKA. This is why spiderless rings will allow a smaller ring.

Moving the chainring away from the spider will adjust the chainline. Generally this is fine on a SS setup, but, geared may mess up the ring spacing. There are possibly too many factors to get the spider clearance on all cranks/spiders to make it worth the supply for the minimal demand.

[Sparticus]

In general, i think its a clearance issue. The spider for 104bcd is usually wide enough to interfere with the chain on the smaller chainrings. I think the groove/low point of teeth on my e.13 32t ring is right where my spider mounts on my Sram AKA. This is why spiderless rings will allow a smaller ring.

Moving the chainring away from the spider will adjust the chainline. Generally this is fine on a SS setup, but, geared may mess up the ring spacing. There are possibly too many factors to get the spider clearance on all cranks/spiders to make it worth the supply for the minimal demand.

This is spot on. Good explanation.

--sParty

[ovwok]

it moved the chanline over about 1mm, granny gear is still in the same place and i dont have any problems running 8 speed chain. there is a guy here on mtbr that makes a geared verison 30t with ramps out of aluminum google anderson 30t chainring.

[ovwok]

Sorry for offtopic but I've been looking for something like this but why don't any companies make 30t x 104mm chainrings readily available?

here a link to the tread

30 tooth 104 bcd

[cdn-dave]

McMaster Carr, $26

Thanks for the info! I think the last time I looked at McMaster Carr, was for an M10x1.0 bolt to mount my DIY chain tensioner onto the derailleur hanger

[J3SSEB]

Really nice! But don't try and go all homebrewed on us

[RustyLeaf]

How do you keep chain tension? I dont see a movable dropout or chain tensioner