Bicycle Mechanics - Are all chainring bolts the same size?

I took apart my double chainring and thought I should replace the bolts. The LBS said they didn't have any of the same size, so I went on ebay to snoop around, and those don't show any size. This leads me to believe that they are all the same size. Is that true?

I took apart my double chainring and thought I should replace the bolts. The LBS said they didn't have any of the same size, so I went on ebay to snoop around, and those don't show any size. This leads me to believe that they are all the same size. Is that true?
Most are the same size, use a 5 mm Allen bolt and a nut on the back side that takes a pin spanner. They fit a 10 mm hole.

Some older cranks, mid-80s and earlier lower end models used oddball, un-obtainable bolts, usually with a smaller diameter hole.

If you had thought to mention what make and model your crankset is I could probably have told you for sure.

Sheldon "Maybe" Brown

+-----------------------------------------------------+
| Life is the art of drawing sufficient conclusions |
| from insufficient premises. --Samuel Butler |
+-----------------------------------------------------+

I took apart my double chainring and thought I should replace the bolts. The LBS said they didn't have any of the same size, so I went on ebay to snoop around, and those don't show any size. This leads me to believe that they are all the same size. Is that true?
As Sheldon says, they are mostly of the same size in terms of diameter and size of allen wrench needed.

However they come in different lengths. There is a standard length that is long enough to pass through two chainrings and the spider (works with most double or triple chainring setups). And then there is a shorter length that is only long enough to pass through one ring and the spider, which is typically used for single-chainring setups and to attach granny rings to the inside of the spider. These are typically sold on ebay as "BMX" or "fixed gear" or "singlespeed" chainring bolts.

Hope that helps!

Most are the same size, use a 5 mm Allen bolt and a nut on the back side that takes a pin spanner. They fit a 10 mm hole.

Some older cranks, mid-80s and earlier lower end models used oddball, un-obtainable bolts, usually with a smaller diameter hole.

If you had thought to mention what make and model your crankset is I could probably have told you for sure.

Sheldon "Maybe" Brown

+-----------------------------------------------------+
| Life is the art of drawing sufficient conclusions |
| from insufficient premises. --Samuel Butler |
+-----------------------------------------------------+


I have a Trek 460. The chainring tool that I have does not fit the stock chainring bolts as the tool is too big. However, I did buy one chainring bolt to replaced a stripped one, and that fit the tool.

I think track cranks are a little shorter. At least I remember road ones being too long to tighten correctly on my track bike.

edit: nevermind, that was when I put a road chainring on by mistake.

I think track cranks are a little shorter. At least I remember road ones being too long to tighten correctly on my track bike.

edit: nevermind, that was when I put a road chainring on by mistake.
Yes, that's generally correct... the road bike chainring bolts are meant to go through two rings and a spider, and are generally a bit too long to fit tightly on single-chainring cranks.

If you have access to a power grinder, it's very easy to make longer bolts work with a single chainring by grinding about 2 mm off their length.