Help 😆
 

My Co op cty1.3 has attachment points. Can anyone tell me the bolt thread size I would need ?

Attachment points for what and where on the bike are they?

(My house is painted, what do you think of the color:)) Andy

Maybe the vendor or manufacturer could tell you.

Buy a 5mm bolt and see if it fits.
If it doesn't, buy larger/smaller.

Attachment points for fenders~racks....danxs

As Bill said. Most all the typical mounting bosses, eyes, are M5 thread (5mm diameter by .8mm per thread). If the bike has a bottle boss set with bolts they are likely M5. Some drop out eyes are M6 (6x1), was popular in the 1980s on Asian made moderate cost bikes.

BTW most fender struts have a strut mounting hole big enough for M6, with a M5 bolt the bolt head can begin to sink into the strut's hole/loop. The strut will never get really tight and tend to loosen. I suggest considering sandwiching the strut loop with a couple of washers. This will allow the bolt to be better tightened and the strut's hole/loop not open up because of the bolt head. Andy

5mm x 0.8mm is the most common for those mounts. 6mm x 1mm is also possible. Others may be unthreaded to use a bolt that passes all the way through the fitting. Older USA-built bikes may have SAE spec fittings. And older British bikes may have Whitworth spec fittings.

If the old clunker is old enough, it might be ANSI and not metric.

But I guess someone already said that, but in other terms. <grin>

Looks like this is an REI branded bike. Call up the REI you bought it from. As you can see from the other posts there are no definite answers from your limited info.

Ride the bike down to your local hardware store, and ask if you can try an M5 bolt. It'll probably fit.

Check the eyelets for paint overspray before trying the bolts (yes, M5 is most likely). I've built up several frames with racks and/or fenders and the attachment point have often required clearing before the bolts would thread in.

5mm x 0.8mm is the most commonly used braze-on bolts. If the braze-on is SAE is it likely a 10-32 which is close enough to a 5x0.8mm to fit. 10-32 will work in the metric fittings as well.