Hi,

I am thinking about buying a down tube shifter that's designed to screw into braze-ons on your down tube, however, the frame I am fixing up doesn't have these (i.e. is simply straight) is there any easy way to convert so I can fix a metal strap on piece to the shifters.

Cheers.

70's bikes used a band for the shifter mount, the tube diameter 1.125".
you can find those.. old bike , cannibalized, or someone else's stripping
and auctioning off the parts ..

I think you will find the braze-on shifter levers are different internally and will not mount on the strap without significant modification. You could try these instead https://www.sjscycles.co.uk/mobile/pa...air-prod20973/. Modern Strap-on shifters are fugly and no love goes into the strap at all. If you can get an old pair of say 600 Arabesque or 105 Golden Arrow strap-ons I'd be very tempted.

Be careful googling for "strap on" stuff.

Plenty of old "clamp-on" shifters out there.

As noted, the lever mounting points on clamp-on downtube shifters are typically not compatible with braze-on levers so you will have to purchase a complete clamp-on shifter set or have a frame builder braze dt mounting bosses to your current bike. The later approach can be expensive and will require a repaint.

There is pretty much anything for shifters and bicycles. https://www.ebay.com/itm/Shifter-Boss...-/120705782780 Could you tell us what kind of shifters you want to use; brand, speed, friction/index..? Might be able to find something better fitting a newer bike.

I am trying to fit an entire Shimano 600 group set.

Perhaps the best option would be to just buy the 'arabesque' clamp-on shifters. I presume they would be compatible with later 600 derailleurs?

Friction shifters are compatible with everything.

As stated, so long as your clamp is the right size to fit to your tube,
you should be good to go.

Note that frames originally equipped with a set of DT clamp on
shifting levers usually has something braised to the down tube
as a stop to prevent them shifting down the tube under use.

You might need to kludge something for this or you might not,
depending on how well the clamp fits your tube and how hard
the pull is.

Even many cheap bikes with stem shifters had a "stop" brazed on the underside of the downtube to keep the band-on cable housing stop in place.