Bolo Grubb

I have a triple chain ring on a bike that now only needs 1 chain ring in the middle chain ring spot. Do I need to buy new (short) chain ring bolts or will the bolts holding on the smallest chain ring work?

this is on a 1984 Trek 720. The 2 larger chain rings are held on by the same set of bolts and nuts(?) the smallest chain ring is held on by just bolts into the crank.

Thank you

caloso

You need shorter bolts. Go to the LBS and ask for "single stack" or "BMX" chainring bolts.

(I learned this the hard way. I thought I could get away with the same bolts, but I lost 2 of the 5 on the way to work on my first fixed gear commute. Not good.)

digger

Yes, the bolts used to hold your large ring are also used to hold your small ring onto the cranks. To say that another way, when you undo the bolts for the large ring the small ring will also be removed.

A seperate set of bolts are used to hold the small ring onto the crank.

No, you do not need to get new bolts UNLESS you break one (or more). This is easy to do as they are hollow, just don't over torque them.

HillRider

I think digger mis-understood what you are trying to do. You want to use a single chainring on a triple crank spider, right? Yes you will need shorter bolts and nuts.

Caloso is correct in describing what you should ask for.

JanMM

If you are really cheap, and want to continue to use the original bolts, you can make spacers out of an old chainring, by cutting off the ends with the holes. I've done this and it's not elegant.

digger

OH! I thought you wanted to replace your middle ring with a NEW one.

Sorry! Never done this, but I would imagine you'll need shorter bolts.

tellyho

No need for new bolts. Pop the old ones out, take the grinder to the female part. Presto: single-speed chainring bolts.

jgedwa

Chainring bolts are strangly expensive for what they are. Typically about $10. Because of this, I grind them when I need them shorter.

One bit of advice, be careful if you buy replacement ones that are aluminum. (Many made for BMX use are.) It is very easy to strip them. But if you don't get them tight enough they will work loose. Grease the threads and tighten methodically.

jim

Bolo Grubb

ok but would the bolts holding on the granny chain ring be short enough and the right size to replace the bolts holding on the 2 larger chain rings?

So bolt A into hole b

tellyho

Different bolts. The granny ring bolts onto the crank spider with holes drilled in the crank itself. Bolts for the other two rings are separate and two-piece. So the answer is no.

In any case, your granny ring is not going to fit in the middle slot, if that's what you're thinking of doing.

Bolo Grubb

Thank you, that was the information I needed. And no I thinking of using my granny ring. I want to use my largest chain ring, but need to move it to the middle position and remove the other 2 chain rings.

tellyho

So you'll need to pull all the rings (and possibly the crank to get to the granny bolts), and reinstall the big ring with either the ground-down bolts or a new set of single speed specific bolts.

caloso

Oh, and when you're at the LBS buying your new singlestack bolts, do yourself a HUGE favor and pick up the proper tool:

Zouf

Often heard about this, never experienced it nor done it (since I had no grinder), but (since I now have a grinder!), you confirn it's the female (i.e. inner) bolt that needs grinding?

lukeC

yeha bolts for a Single are really over-rpiced from most places. - as a result i've done two dodgy fixes to fit the bolts from a Double to just hold a single

In one case I bought a few washes and used those to replace the metal of the old chainring and tightened down hard. - this worked ok - but does have a tendency to come loose every now and then. so check them regularly.


2. I cut down the female parts using a hacksaw. how?
- if you screw the male in the back of the female a bit it will add some radial strength then - cut a little notch into two bits of wood - say soft pine. then clamp down in a Desk Vice. - its now pretty easy to cut them down without causeing any real damage.

Thumpic

dremel cut off wheel.....run the bolt into the female from the back far enough so that only the length needing to be removed is "empty". Cut off excess; run the bolt on through to clean up the threads; pretty up it all up with the dremel and your done........