What thread are chainring bolts?

75mm thread. As a rule, a set of chainring bolts designated for use with a single chainring will do the job nicely. Trouble arises when the chainring is thinner than it might be and the bolts tighten against themselves instead of clamping the ring to the spider.

What size chainring bolt do I need?

Single bolts are generally between 3.5 – 5.0mm Long. Double bolts are generally between 5.0 – 6.5mm long. Triple bolts are generally 7.0mm or longer. Triple bolts are normally only used to hold the two outer chainrings as the inner will be smaller and screwed directly to the crank.

What are standard bolt threads?

There are three standard thread series in the Unified Screw Thread System that are highly important for fasteners: UNC (coarse), UNF (fine), and 8-UN (8 thread).

What is a chainring bolt?

Chainring bolts perform the simple task of securing one or more chainrings to the chainset spider, and in the case of many MTBs, a bash guard as well. The outer nut has a standard external diameter of 10mm so theoretically the bolts can be used to fit any chainset.

How do you fit chainring bolts?

Securing the nut with chainring nut wrench or hex key, thread the bolt into the nut in a clockwise direction, screwing in just until the bolt feels resistance and the rings are held in place. Repeat for all bolts and then gradually move from bolt to bolt, tightening each bolt a quarter of a turn each time until tight.

What size are Shimano chainring bolts?

Outer diameter of male bolt across threads is 7.7mm, outer diameter of female sleeve/nut is 9.6mm. Diameter of both across the pan head is 11.6mm. These are the measurements for a Shimano 5700 compact crank 50/34 stock chainrings, for future reference.

What does UNC bolt mean?

Unified Coarse thread
UNC :Unified Coarse thread. UNF :Unified Fine thread. UNEF: Unified Extra-Fine thread.

What kind of chainring bolts do you need?

The inner needs only be long enough to obtain sufficient clamping force from its fine M8x0.75mm thread. As a rule, a set of chainring bolts designated for use with a single chainring will do the job nicely.

How big is the outer part of a chainring?

The female-threaded “outer” part has a standard external diameter of 10mm, so any crank bolt will fit into any chainset. That does not, however, mean that any set of crank bolts will work for every chainset.

What is the BCD for a chainring bolt circle?

Instructions have been moved to a separate page. For uneven spacings, see the next section of this table. Beware of near-matches! Measure! The BCD is 1.414, 1/sin 45°, times the spacing between adjacent holes.

How big of a chainring do you need for a crank spider?

Until then, of course, they perform the simple task of securing one or more chainrings to their crank spider. The female-threaded “outer” part has a standard external diameter of 10mm, so any crank bolt will fit into any chainset. That does not, however, mean that any set of crank bolts will work for every chainset.