How do you tell if a frame is 501 or 531 if there are no stickers?

[montage]

I have a nice light blue Triumph Cyclone frame which I am guessing is 501 due to average componants, but there is always the chance that I may be wrong

 

[jimboalee]

Whip out the BB.

Take a shave off the end of an exposed tube where it protrudes out of the BB shell.

Take the shave to your local metalurgist or University Materials technology dept.

Chrome and Molyblenum - 501

Molybdenum and Manganese - 531

 

[jimboalee]

Hey, you might find your Triumph Cyclone might be made of willow.

Your lucky. They are pre 'kocked-in'.....

 

[brockers]

A 27.2mm seatpost probably won't fit in a 501 frame. I think they take a 27.0mm post

 

[montage]

Whip out the BB.

Take a shave off the end of an exposed tube where it protrudes out of the BB shell.

Take the shave to your local metalurgist or University Materials technology dept.

Chrome and Molyblenum - 501

Molybdenum and Manganese - 531

Ok, how do I find out with a method which is cheaper than buying a brand new bike?

 

[montage]

A 27.2mm seatpost probably won't fit in a 501 frame. I think they take a 27.0mm post

It takes a 27.0 so I guess it is 501

 

[e-rider]

531 frames always (I think) use 27.2 seatposts

 

[Tim Bennet.]

531 frames always (I think) use 27.2 seatposts

Except when they don't.
Mrs TB's custom built touring frame uses 531c and is only 26.8.

 

[4F]

I think that the fact it does not have a 531 sticker on it means it is either 500 or 501.

 

[biggs682]

the same question always stops me from buying a bike that has had a respray etc etc as no proof , and yes you can buy 501 and 531 stickers on flea bay

 

[threebikesmcginty]

501 is still a decent frame - and still surprisingly light isn't it?