Mudguard eyelets - thread size

[Steve I]

Hi all, I'm a new member. I tried this on bike radar, but had no luck. I've just bought a 2008 Giant scr 1.5. I'm after some bolts for the fork and frame mudguard eyelets. For some bizarre reason the guard eyelets are a different thread type from the bottle cage and rack eyelets, which are the generally standard M5 (5mm metric thread).

As chance would have it, I have a single pan head bolt which fits the mudguard eyelets. I think it used to fix the guards to a 1990 Raleigh Record Sprint I used to own, though I'm not completely certain about this. The outside diameter of the unknown bolt is 4.5mm or 11/64". It also has a different thread pitch as I've compared it to the 5mm bottle cage bolt. Does anyone know what size bolts I need?

[cranky]

I think you'll find it's an M4, as supplied with SKS mudguards, although I'm prepared to be corrected on this

[Steve I]

Thanks for the suggestion, but it's not M4 as the opposite end of 4mm drill bit goes right through the threaded holes. A 4mm bolt would do the same. I don't even think it's metric at all, I think it's some kind of imperial screw thread.

[hubgearfreak]

For some bizarre reason the guard eyelets are a different thread type from the generally standard M5

outside diameter of the unknown bolt is 4.5mm or 11/64".

if the existing thread is 4.5 mm outside diameter, i'd run an M5 tap down the hole. job done, and no struggling for spare bolts in the furture

[Bob S]

Mine are 5mm.

[ianr1950]

I seriously doubt that it is imperial, M5 would be my bet if
4 is too small.

[aesmith]

All the bikes I tried use M5, except my wife's late '70s Raleigh which has something almost exactly the same diameter but with a different pitch.

I vaguely remember these being one of the BA threads. 1 BA ?

Surprising on a modern bike. Are Giant American? Maybe ask them or the dealer.

Tony S

[Steve I]

Thanks for all the input. Not sure I fancy running a tap through the tapped holes on a new bike, the threads may end up a bit shallow. Tried both the dealer and Giant, neither of whom have replied yet. Looks like I'll have to use a nut and bolt to hold the mudguard stays, and use the single bolt I have where I can't use a nut and bolt (on the cassette side of the rear). What Giant were thinking when they specified this odd thread is beyond me. If I ever find out the bolt size I'll post back.

Cheers for the 1BA suggestion Tony, that's worth a try.

[Steve I]

The 2BA thread size has an outer diameter of 4.7 mm, but from what I've read the BA thread range is obsolete.

[Ambermile]

Don't you believe it!

[fossil]

Giant bikes are American , and they use the old imperial mesurement system ie feet and inches
so it wont be a metric thread
if you know someone with a tap and dye set try puttin a few through till you find the right one

hth

[ianr1950]

My Giant carbon race bike has metric threads

[cranky]

I know this may sound boringly naive but have you checked for and removed any overspray from the aforementioned orifice ? If not, you may find on doing so, that which did not fit is in fact, a goer.