Bike screw

[Toby]

Help!

I'm trying to find a screw to fit a pushbike but I've not got a clue what type of screw is required and I'm wondering if it's a standard size across all bikes which someone here might know.

It's the one used to secure the front of a pannier to the frame just below the saddle. There's a kind of "tube" welded to the frame on each size inside which is a screw thread but for what exactly?

Anyone got any ideas or am I destined to work my way through B&Q's screw department hoping to get lucky? :)

[Dymetrie]

Richard Slater says maybe an M6 or an M7...

It will depend how old the bike is, if it's ancient it won't be 'M' as that is metric.

[Toby]

Well the bike is an "Astra Starlifter II" ladies one. Pretty old but then the pannier kit came with M5 bolts to fit the bottom of the pannier and they fit fine so maybe it is metric.

The ones I need are narrower than the M5s, is that the case with the M6 and M7 as the names suggest otherwise. Ta.