Would anyone be able to help identify the make of my bike frame? There's no branding on it and I built it up custom using different parts. I've never been able to find out what the make is and am v. intrigued.

It's really light and is probably aluminium. It's got a cut away on the seat tube. it's got down tube shifters. None of the tubes are round, all are odd shapes, quite thick.

Picture below. I can upload more is necessary.

enter image description here

  • 1
    I dunno about the bike but I like your wall-anchor. Thieves around here would steal both your wheels though by snipping your cable, so I'd lock at least the rear wheel using the Sheldon method.
    – RoboKaren
    Commented Aug 22, 2017 at 16:19
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    Where/how did you obtain it? Commented Aug 22, 2017 at 19:51
  • Looks titanium to me, high build quality, possibly custom.
    – mattnz
    Commented Aug 22, 2017 at 20:16
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    Whats the serial number like? Is it many digits or is it quite short? Short serial numbers can mean custom or short run local builders, whereas 7-10 digit ones imply mass-produced frames.
    – Criggie
    Commented Aug 24, 2017 at 15:49
  • @mattnz i also thought it looked similar to titanium frames i have seen in the past. Cool looking frame though either way
    – Nate W
    Commented Aug 24, 2017 at 21:58

1 Answer 1


From your photo I think the bike is a bitser, and without decals/names/markings its very hard to identify.

The front fork is clearly labelled Giant and has straight tines so its relatively modern. Possibly a carbon or aluminium alloy fork, it doesn't look like a steel fork. Fork is also painted completely different to frame, so they're not originally together. Fork is also threadless at the top, which is quite modern. The frame would have had a quill stem when new.

However the hoods and brake levers are 80s or possibly early 90s. They're not combined brifters, the shifters are on the downtube which is completely 80s.

The horizontal top tube looks 90s when considering its aluminium alloy. Thicker walled aluminium was used when it was a new material for framebuilding, and hydroforming wasn't possible so strength was added with bulk.

The rear wheel cutout in the seat tube is for aerodynamic reasons - it smooths the airflow a bit, but the main advantage was to permit a shorter wheelbase while retaining 700c wheels.

The road double chainrings are not a compact, instead they're quite close together in size. Not sure what that implies, other than few hills.

Identifying steel is easy - touch it with a magnet (like an old hard drive magnet) and see if it attracts. Aluminium or titanium won't attract a magnet. To tell Aluminium from Titanium is harder - neither require painting. Titanium will spark a lot, bright blue/white when touched with a grinder, and aluminium won't really spark at all.

If you can get to a bare piece of metal, apply a moist cathode (paper towel) to the positive-attached metal. 9v should do to get a slight tan tinge. 18v (2x9v batteries) will take you to dark violet. Some of these requires taking off a patch of surface coating, so not a first option.

Heres a 1998 mongoose road bike that shares a lot of features with your frame's design. This one is aluminium, and has the original fork still.

enter image description here

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    OP said they built the bike up so it has a mix of components, he want to know what the frame is. Commented Aug 24, 2017 at 16:56
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    @ArgentiApparatus yeah but "I don't know" was too short an answer for SE. There are components from at least two maybe three decades on that bike, which was worth noting but too long for a comment.
    – Criggie
    Commented Aug 24, 2017 at 20:25
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    Yeah, I would say an early AL frame. I forget the exact chronology, but I'm thinking about 1990 Cannondale and a few others produced AL frames similar to this. Commented Aug 25, 2017 at 3:08
  • @DanielRHicks the one pictured is a 1998, and the previous year's model had downtube shifters. So this is a data point if nothing else.
    – Criggie
    Commented Aug 26, 2017 at 2:45

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