Bolo Grubb

is it as simple as pulling off 2 of the chain rings?

I have a 1984 trek 720 tour bike. I am going to put a Nexus hub on the rear but hoping to save a little money by using the existing crank and BB. Is it possible to just pull off the smallest and largest chain ring?

operator

Assuming teh chainline is correct to the middle ring and your rear hub.

lukeC

Of the triples I've seen the Large and Middle Chainrings are usually held on at the same point with "longer" Double Chainring Bolts and the smallest or granny ring will be held on at a smaller BCD point.

you can pull of the small one easily. However if you want to just use one of the larger/middle the Chainring bolts you have will be too long.

- You will need to either shorten the chainring bolts (hacksaw or grinder) or buy some single Chainring bolts. (BMX / Track bike ones)

- and aggree with the above - you can have issues with getting a straight chainline.

Bottomfeeder

If your chainring bolt are too long once the outboard chainring is removed you can do 1 of 3 things.

1: buy some shorter chainring bolts from some niche webstore.

2: file the existing bolts and nuts down. (hope you have a bench grinde or at least a vice and decent file.) I've done this both with and without a vice for my various single speed projects.

3: go down to the hardware store and pick up some nylon spacers to use as 'washers' on the existing bolts. I did this as a 'temporary' fix when converting my wife's triple crank to a single to work with an internally geared hub. I assumed they would wear out somehow and I'd have to eventually do a 'better fix'. Well that was 3 years ago, and they look like they'll last as long as I don't monkey with 'em.

DanO

operator

They're not niche. Ever heard of a fixed gear? Short stack, bmx chainring bolts are a'plenty. At $5 A set, filing down chainring bolts is a serious waste of time, same goes for your washer method.

fiver

Well...I was going to recommend removing the teeth from the outer ring to make yourself a chain guard, and reusing the bolts at the same time, but it sounds like that would be a "waste of time".

ps: it's not kind to insult those offering you their opinions. I have been a mechanic for a long time and the previous posts are all good ideas.

Bottomfeeder

Yea. Kinda hostile there Operator. Usually I've seen short bolts for a bit more than that - https://www.webcyclery.com/product.ph...cat=406&page=1. In fact, If you've got a source for those $5 a set bolts I'd like to pick some up to have on hand. Then again, those 5 nylon spacers probably came in just under a buck down at the Do It Center. And perhaps once in a while spending a half hour at the vice with a file and a cold one is just what the doctor ordered.

DanO

fiver

word

erader