http://www.wildbike.co.kr/4917876

Q.  How can I tell if my spindle is long enough for 4 chainrings?

Shift the front derailleur  to the triple position.

Measure the distance between the inner arm of the derailleur and the seat tube (or equivalent)

If you have 8mm (.310") or more,  your spindle is long enough.

If not, subtract the measurement from 8mm. 

This is the minimum amount the crankarm needs to be moved to the right.

You also need 9mm space between the chainstay and the triple at the diameter of the quad.

Also check the distance between the chain and the tire when shifted into the lowest gear.

You can go to Sheldon Brown's incredible website and check out his Bottom Bracket Size Database to find what length spindle you have now. http://sheldonbrown.com/bbsize.html

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Q.  How can I move the crankarm over to accommodate 4 chainrings?

A.  Some spindles are adjustable.  Simply adjust as needed.

If the distance needed is less than 3-4mm

Measure the distance between the left chainstay and the crankarm (in the 3:00 position facing it)

If there is enough room, the bottom bracket can be shifted over by using spacers between the right BB cup and the BB shell.

If those methods won't do it, a longer spindle or bottom bracket cartridge is required.

Remember,  typically, but not always, half of the additional length is added to each side.

장착 사용기

the Mountain Tamer Quad is a fourth chainring, 16 teeth, with the Quad you can climb anything. I know, because I’ve ridden a few times with the inventor, Tom Mayer, co-founder of the Iron Horse Classic Road Race, member of the Mountain Bike Hall of Fame in Crested Butte and all around nice guy, and I’ve watched him climb steep slopes while the rest of us had our bikes on our shoulders.

The most significant hurdle to overcome was the cranks. The quad requires a 110/74 mm 5 bolt crankset. and these are hard to find. Easy enough, first attempt is to just use his old cranks. Worked on the Raleigh, with a wide anough bottom bracket spindle, they should work on the Soma. BUZZZZZ. Wrong answer. Even with a BB spindle length of 137 mm, the cranks hit the chainstays. can’t find a longer BB, so it’s time to find some new cranks. Searched through a few distributors, called a lot of shops, and searched the internet, but no dice. So, I called my good friend Tom for some advice. He sympathized with my dilemma, he already knew that these cranks were few and far between, and he let on that the last couple he’s known about were all found on E-bay. So off to E-bay I go, where I find a brand new Sugino crankset that meets the bill. I was even able to return to a normal length BB.

The next problem is immediately noticeable. the quad spider mounts between the middle chainring and the small chainring, and is 3 mm thick, which with the built-in spacer on the Suginos is just wide enough to drop the chain between the chainrings. Every shift..

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mtbr사용기

I've ridden with the owner a few times and his 4rth chainring allows him to climb insanely steep sections that others walk. It's really amazing - though he's riding 26" wheels. But with many geared 29er people wanting to run smaller chainrings up front, I wondered if anybody has considerd using this old and proven product. From what I understand this is the first product that Dirt Rag ever reviewed in their magazine. Seems to me the issue is finding a compatable crankset.

Other than the missing paint from the cranks it is a pretty sano setup.

I managed to clean a really steep section yesterday that had previously denied me. I have been trying it on and off for 22 years. Granted, it is not super technical with a small step up right at the start of the steepest pitch, but still, on my second try yesterday over the top I went. Used the 18/34t combo all the way from the bottom, the first part of the climb has a sharp right kink to it that pretty much limits one to around 4mph anyway.

The 26t middle ring is very nice, I may leave it on for a while. It lets me stay in the middle a bunch more in low speed climbing sections (duh!) without going to the 34t rear cog. Pretty nice as that 30-34t jump on the cassette is big. It also forces me to use the big ring (36t!) more and I wanted that, both to spread the wear more evenly over the middle and outer rings, and also to keep the chain angle down.
Didn't have a chance to find out what speed I would have spun out in the 36/11t combo at, but did note that at 24mph there was plenty more to go.

The 36t ring is an old full width tooth Suntour 8sp. unit and will hang the chain if care is not used when shifting off of it. So the the 38t ramped and pinned 9sp ring will go right on as soon as it arrives, more for the shifting than the gearing. Hmm, I can get a 37t pinned TA 9sp ring from Peter White....

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http://www.abundantadventures.com/quads.html

Don't be limited by stock gearing 
You can have LOWER GEARS  
Any way you want them