If your bike has US-designed or made components, buy an imperial set of hex or allen keys. I learnt the hard way by rounding off the pad retention bolt on my Avid Elixirs and had to drill it out and buy a new bolt.

That's all I have to say on the matter for now.

Are you sure?

I've an imperial set and the only thing I've ever used them for was changeing the clutch on the midget.

Yanks still use imperial, so US components are not metric-sized.

Thought they farmed out production to the far east(to a factory where they don't/can't bleed the f***ing things properly).

my elixirs use a 2.5mm bolt as a pad retainer

In 15 years of bike and car faffing, frigging and fettling, I have never met an imperial hex bolt. My FACOM metric set however is well used.
Only time I could imagine using imperial is with cheap metric components where they are made to poor tolerances, so that the correct allen key is a loose fit?

Use avids here and other american bike parts metric tools with no problems.

Weird then, as a 2.5mm key is definitely too small and a 3mm too big for my Avids.

I use imperial allen keys every day 🙁
(I work with lasers, and lots of US components have 'english' threads)

Trailrider Jim – if your bike has US-designed or made components, buy an imperial set of hex or allen keys.

that'd be why park tool allen key sets have a mix of metric and imperial on the same carrier.

Avid is part of SRAM

are all SRAM and Rock Shox stuff imperial?

Avid service guide

Avid service guide says you need metric Allen keys

From Avid Elixir service instructions.

1. Remove pad retainer bolt
Start by removing the “E” clip on the wheel side of the caliper, then unscrew the retainer bolt using a 2.5 mm hex wrench. Remove the retainer bolt all the way

Are you SURE they aren't TORX head bolts on there?

😕

In building and maintaining several mountain bikes over the last fifteen years using components from all over the world I do not recall ever using anything other than metric hex keys, with the exception of Torx!

Bought some Ti bolts, my 5mm allen key doesn't quite fit but my pedros 5mm fits fine. Never quite worked it out.

Got a set,Never used them.Its all metric

you have just fekked it i reckon.

Someone once tried to convince me that there were tolerance differences between Japanese nd European versions of metric for both tools and fasteners.

Have to say, I checked the date wasn't 01/04 for that but he was adamant it was true.

i have NEVER found an imperial bolt or nut on a bike.

though we have a 50s cruiser here and cant get the wheel off as its whitworth, which needless to say, halfords and the bike shop, do not stock (boo)

The only time I have found imperial allen bolts on a bike was on my 1990 Bontrager Competition fork crown clamp bolts.

Onzadog – Member
Someone once tried to convince me that there were tolerance differences between Japanese nd European versions of metric for both tools and fasteners.

This is partially true but I've never seen it on a bicycle component as they are only small size threads. Motorcyle bolts are different tho. M8 bolts (normally 13mm hex head) are usually 12mm and they use a lot of fine metric threads too.

As regards allen keys there is a standard and sizes are defined in ISO 2936:2001

lots of US made products quote metric tool sizes, however I've found particularly for Fox that the Imperial size is a better fit eg 1" AF sockets for fox 32 topcaps & 1 1/4 AF for fox 36 topcaps

also the schrader valves in talas 36's are held in by 7 /16……

rule of thumb is the metric sizes work fine if your careful…

I suspect the sliding drop out adjuster bolts on my Lynskey are imperial.
I haven't checked the threads, but a 5/16 AF spanner fits better than an 8mm one.
Something for any Lynskey owners to bear in mind if you ever need to replace the bolts.
Don't try to force an M5 bolt in what I think is probably a 3/16 UNF thread in the frame.