pastorbobnlnh 

I believe the spacing will be fine--- but it will depend on the crank set.

As I mentioned, in my case, this was the only 130BCD I could easily pull off the shelf and attempt to run the triplizer as the outer ring and effectively move the 74BCD granny to be in the space occupied by a traditional inner. I believe if my crank arm did not have the platform for mounting a 74BCD chainring, this set-up would work perfectly. I wish I had an unmounted Shimano 130BCD to attempt this on. I'm pretty certain it would work on this Dura Ace crank.



However, I'm not planning to pull it off the bike to service the BB until after Christmas, so it would be a long wait for the OP to get an answer. I'd like to encourage @Byepsycho to try his Willow set up in a similar way on his Centurian crankset.

Again, just a boomer's two cents FWIIW for a millennial. YMMV.

Kuromori

I'm just not seeing it. I can't see any way the chain would clear the spider tabs if the inner ring were pressed up against the inside of the spider tabs instead of below the teeth. The chain needs room to both sides of the chainring to sit on the chainring. If you manage to put a 30t on a 130bcd crank, the teeth will be right around where the chainring bolts and the tabs are, and without being spaced in, they will be pressed up right against the tabs, leaving no room to the side.

If you lay a chainring flat on a table, then you can't put on a chain on it without lifting it. If the chainring spacing is kept the same, then the granny ring is being pressed up against the insides of the tabs the same way it would be if you put the ring on a table. It only works with the bigger inner ring because it overhangs the tabs.

Salamandrine 

^^^ I'm not sure how you're envisioning this. The tripleizer replaces the inner chainring, and becomes the middle chainring. The drop down tabs on the tripleizer ring go in between the spider arms. The inner chainring bolts onto the tripleizer tabs using stand off spacers to get the correct spacing and room for the chain.

WRT to everyone else telling the OP to go for it and learn by trial and error. That's typically good advice and true. Just fair warning that this may not be easy or cheap. Spindle swaps and triple conversions could be a big pain even in a well equipped shop with boxes full of various sizes bottom bracket spindles. I do agree that if the the OP does this DIY, best to start by putting the newly reconfigured crankset on the existing BB. It might fit, and if it doesn't, it will show you how much extra space is needed.

ThermionicScott 

The problem is that some people are proposing using the tripleizer as the outer ring so that the 74mm BCD ring would become the inner. It's not clear how the spider tabs would not interfere with the teeth of the inner ring unless it was spaced way out.

rccardr 

Well said and summarized, sir.

Let is remember that even in a normal installation, there is a spacer placed between the spider tab and the inner ring, so as to enable the correct ring spacing. If the tripleizer is used as the outer ring, then one must simply increase the size of the spacer by the thickness of the crank arm where the outer ring bolts up- perhaps 5 to 7 mm, depending on the particular crank. This assumes there are no other protrusions cast or forged into the crank arm itself that might interfere with a smaller ring than originally designed for.

I can forsee circumstances where a very larger spacer might result in an inner ring that is inadequately supported-especially if being used energetically by a particularly stout rider, but generally this should work just fine.

Salamandrine 

Oh, I see. Honestly that sounds like a dumb idea. I don't think it will work either.

It might potentially work with certain cranks if they have enough undercut to the spider. Some early 90s aero cranks for example. I still don't like the idea. Would probably require grinding away the inner chainring ledge of the spider.

Kuromori

There's the rather large problem that the gap between the chainrings becomes rather large with a phantom middle ring, large enough for a chain to fall through.

rccardr 

I believe you misunderstand either my meaning or the construct involved. There is no phantom middle ring, it is essentially set up as a double. So the spacing between outer ring and inner ring (remember, there are only two rings in this example) is no different than the spacing between normal rings on a normal double.

As it were.

So to speak.

Kuromori

I reread it 3 times over, maybe I'm fuzzy on what exactly you mean, but I can't read it any other way but to say continue spacing out the granny ring until it works, while keeping the triplizer in the outer position. You mention larger than normal spacers, which means larger than normal chainring gap. It doesn't really matter if you can find an alternative mounting method that lets you mount a 30T where a 42T used to be, the chain and the spider can't occupy the same space to the side of the 30T.

jonwvara 

Wait, what? Is there really talk of using the triplizer as the outer ring and the granny as the inner ring of a double? The best way to see why that won't work is to try it.

rccardr 

...and you should know.

jonwvara 

I suppose I should, but I might not--I only skimmed this thread after the subject line caught my eye, so I may misunderstand what's really going on. But here's an approach I used to set up a triplizer and granny ring as a double. I realize this isn't the BCD under discussion here, but the same approach would work, I think.

Installing a Triplizer as a Compact Double - Red Clover Components

rccardr 

Aha. NOW I understand. Thanks so much!

pastorbobnlnh 

...and where is our OP newbie who could try out what I suggested with his/her Centurian/Shimano 130BCD crankset?

Last night I almost bought an orphaned right side crank arm (a double) in order to try out what I've suggested, but decided even if it was just $20, I didn't need to spend the money. All we need is for the OP to chime back in and tell us what solutions seem to make the most sense. I even went on another search through my spare cranksets, but to no avail, the only 130BCD one I have that is not currently mounted to bike--- is pictured above. 'Tis the season and I don't have time to remove one from one of my existing bikes to attempt something I doubt I'd ever need.

So--- OP--- please come back and respond to our suggestions and guidance.

P.S. I can almost guarantee my suggestion could work on a Single Speed 130BCD crank arm. There are several relatively inexpensive options on ebay including this one which I almost bought.

Byepsycho

Dear 'dad' from another brother,
Y​​​​​​our suggestions may confuse succeeding generations of inexperience mechanics.
Although, you may have turned my first post into a presumptuous tangent, I still love you for all you do for us younger, internet trolls - "no matter what mom says".
Thanks for always going the extra mile for me. ♡

​​​...I've tried attaching the Triplizer where the big ring belongs, but the crank arm makes it impossible to then attach the granny ring to the Triplizer's screw holes. The only way I can envision this working is by attaching the Triplizer to the back side of the spider; attaching the granny ring to it; and recentering the chainline by getting a BB with a longer spindle.
I'll take a picture to illustrate what I described.

Also, please pardon my delayed response.
I've tried commenting, but I keep getting an error notification about not having enough posts to reply.
I hope this goes thru.

P.S. Thanks to everyone else who chimed in.
There's a great deal of options and opinions on here for me to reference, and I hope it helps others in the future too.

I'll post pics of the final product and the steps that worked for me.
Thanks, again, O.G.s!

pastorbobnlnh 

OP--- @Byepsycho oh how you have made my heart leap with joy that you came back and responded! I'm so sorry that you've experienced technical challenges with BF. That's a bummer!

When I tried to mount mine, I discovered that I needed to attach the one nut/bolt loosely on the 74BCD that sits under the crank arm to the 130BCD triplizer, before slipping both rings into place. When you do so, install this one with the nut under the arm and the screw side facing towards the frame. After you do this you should be able to attach the remaining four 74BCD nuts/bolts and the five 130BCD nuts/bolts.

Looking forward to your pictures and thank you for taking some good natured "chiding" from your 62 year old internet "dad."

P.S. I have a single 27 yo daughter living in the Nashville area who is gainfully employed. Looking?

tomtomtom123

As others have said, a triplizer on the outside of the spider won't work. The chain will either hit the spider when down shifting or the outer bolts will hit the inner ring. If increasing the gap between the rings to solve this, then the chain will fall between the gaps.

Also, if the existing chain line was already 43.5mm on the double, and using a triplizer on the inside as the new outer, then you'd have to move the crank 8mm outward or 16mm spindle length.

jonwvara 

,

Yes, as noted, the idea of attaching the triplizer in the outer position was doomed from the beginning. In fairness to you, though, that's really not obvious until you try it--at which point it becomes very obvious (as you discovered).

But as I noted in my previous post, you can install the triplizer in the middle-ring position in combination with a triple spindle, and then put some kind of a chainring guard or "bash guard" in place of the outer ring. You can make a bash guard from a worn-out chainring pretty easily, or buy one. Cyclocross riders use them, and they're available, and not expensive, in most common BCDs. It works well and looks good. If you don't mind the setup looking a little weird, you don't even need to use the bash guard, which is basically cosmetic.

Revracer

What amazing timing as I almost ordered the 46T Tripleizer for the outer ring of my Shimano 600 and then this thread was found. I too wanted to make a sub-compact double but realized that without the 50.4/80 BCD it almost needs to be a triple to get the range.