Yesterday I wondered into eBay, and their feed showed me a Rotrax straight 531 frame with less than 24 hours on the auction. I was tempted to bid, but thought better of it.

Does anyone have any input on this builder? Anyone have a complete bicycle? Are they common outside the UK?

The frame sold for roughly $72 plus shipping from the UK. There were 17 bids.

https://www.classiclightweights.co.u...ilders/rotrax/

There's an incredibly nice frameset on Bike Recyclery right now, asking a bit more than $72 though.

that's a crazy-good price for a frame that has a small but rabid fan-base, for good reason!
Assuming no damage or other downside...even if it was something made later by Whitcomb, I bet still a great riding British bike.
There was (is?) a contributor to this C&V forum who's based in Tokyo (but British) and was something of a Rotrax collector, if you search early posts for "Rotrax" I bet you'll see some pix of his machines

https://www.bikeforums.net/classic-v...beautiful-lugs. Here’s a thread of my 1953 Rotrax. I still have the bike and I’m slowly working on getting it in shape for riding. It’s been a multi year project but I’m enjoying it immensely. They were a small company but the workmanship is second to none.

If you look through the British forums there are many examples
https://www.lfgss.com/search/?q=rotrax&defaults=true
https://www.retrobike.co.uk/search/1...ax&o=relevance
and there is an excellent Facebook group Friends of Rotrax cycles (sorry but this forum has a problem with FB links)

I encourage you to read through Quiet Mike's 1948 Rotrax - latest project. It is a wonderful story and so beautifully photographed.
You may notice my suggestions in that thread.

An important consideration in bikes of this period is the project's end goal. If you are aiming for a period-appropriate bike, it may be far cheaper to buy an unmolested original bike rather than a frame and then buy the parts separately. The cost of the postage for multiple packages to international destinations are needed to be factored in. I live in Australia and my bikes have period-appropriate components and a number are British (1946 Hobbs of Barbican, 1952 EA Boult and 1952 Hobbs of Barbican Blue Riband)

Thanks for very good input. Maybe I should have bid, but I was looking for something to shoot for period correct, and I couldn’t see myself scouring the world for parts.

Plus I have other things on my plate.

Several good posts above with info, but I'll chip in too;

Rotrax are one of those brands that are still a little bit unknown even in the UK, knowledgeable people do know about them of course, but they're certainly not one of the first that spring to mind when you ask people to name a bunch English Lightweight builders. In some ways they're becoming less well known, like many of the smaller regional builders, as time goes on and the number of people with 'living memory' of them fades.
The bigger brands that were more prevalent nationwide have a wider following, but a lot of the smaller builders had more localised followings and Rotrax is one such brand.

Like many other builders from the era they built a lot of very good quality 'club' frames, nothing overly fancy, just good quality, well put together and overall quality frames for various uses. They also built some more lavish and fancy 'showcase' frames at the higher end, not necessarily any better riding or especially 'better', but definitely fancier with more elaborate lugwork etc. so you will find examples of both out there.

I actually own 3, despite them being from well before my time, but I have a bit of a thing for seeking out smaller builders and love learning about the history.

One is an unknown model/custom job from the late 40s, I've yet to build it as it needs some repair work as the back end is out of alignment but I'm hoping to get it back on the road at some point.

I've also a couple of 'Shirley' models, one is a 1955 Shirley which has had a repaint at some point but is otherwise unmolested and still has all it's original frame details and is currently built with a Sturmey Archer 3sp AW hub as a classic clubmans bike.

Another is a later (58 I think) Shirley which was significantly renovated about 10 years ago with the addition of downtube shifter mounts, repaced to 130mm, and had a new brake bridge fitted, relocated for 700c and recessed brakes, the fork crown was also drilled at the same time.
This one I have built up with a mix of older and modern parts and I use it as one of my Audax bikes.

It's supremely comfortable due to the long wheelbase (long stays) and very springy fork and jsut eats the miles up, but is still pretty fast. I love riding it and it always brings a smile to my face :-)

Gratuitous pic of one of the Shirley's:


Renovated 50's Rotrax Shirley