An SBDU 531SL Aero frame? SB4944 was an impulse buy from quite some time ago. I saw it listed on Hilary Stone’s site as an SBDU frame built from Reynolds 531 Professional tubing. The serial number and the date that number indicated together with the repaint showed it was actually built from 531SL and a later 531 Professional transfer was added. Since it’s arrival, it has been a bit of a mystery. But last year I was sent an image that finally lifts the lid on SB4944. It tells me exactly what it is.
Some Background
There are patches of red paint underneath the surface. My initial thought was that it had originally been painted in the TI-Raleigh colours.
So the plan, if there ever was one, was to return it to the TI colours. Other features of this frame were weird, like the top mount gear lever boss that fed the gear cables across the top of the BB shell – that was different and I did have a thought that it was a later modification. But it gave me one of the first ideas I had with this frame, and that was to fit Shimano AX components.
The shape of the lever boss stopped that though. The frame came with Suntour Symmetric levers which require a different shape boss to the AX levers I had, so rather than think of a way of dealing with the shape of the boss or removing it completely, I shelved the frame for a while to ponder.
The frame has been hanging in the workshop and while it was hanging there, I’d seen more and more 531SL SBDU frames, but the odd thing was that they appeared to be in a cluster! My collection has SB4933, SB4944, SB5084 and SB5464. It was that range spanning only 500’ish SB numbers and nothing earlier that made me look further. 531SL has been around just as long as Reynolds 753, so that goes back to 1975. But my own collection of them starts at late 1981. So I delved into my amazing archive of SB frames to see if there was a trend I could spot.
The archives were interesting. I’ve used these archives before to look at the more ‘rare‘ SBDU frame tubing types. I wrote about putting context to that over used term and it was 531SL that came out top of the list as the most rare type of tubing used by the SBDU. I came to the conclusion that as 531SL came out at the same time as 753, most riders must have preferred either the lightweight and strength offered by 753, or the stiffness and reliability of good old 531. 531SL was as thin and light as 753 but didn’t have the strength from the heat treatment. It was just very thin 531 tubing which really had a limited use. Maybe a light rider on good roads could use it but it probably wasn’t a popular choice.
The archives showed that there was indeed a cluster of 531SL frames. There are one or two that appear earlier on. However, they do seem to peak in a narrow range of SB numbers starting from the SB4800’ish point up to SB5500’ish. About 75% of this small cluster all exhibit the same frame features… a Cinelli BB shell, Cinelli fork crown, top mounted gear lever boss with Suntour levers, 2 sets of bottle bosses and a race number tag.
Some New Information
Then I received an image of a Raleigh 531SL Aero bike. Unfortunately, I can’t credit this person because they sent it via Facebook and now seem to have closed their account. They show in my messages list as “Facebook User”. So sorry whoever it was, I can’t recall who you were, so “Facebook User” receives all the credit.
Everything fell into place with my frame – I was looking at the bike that my frame should be, a 531SL Aero!
My theory with 531SL is that it wasn’t used very much and because its successor was around the corner, the SBDU made a series of specials. They had a set geometry and features and were marketed as an aero bike even though there isn’t a aero tube in sight. The ‘aero’ comes from all the assembled parts.
Specification
A quick use of Google Translate gives me the following spec…
- The parade horse from the raleigh racing stable
- Reynolds 531 Super Lightweight Silver Soldered
- Handmade 25mm wire tyres
- Super Champion black anodised rims
- Sugino Mighty aero series for sprocket and pedals
- Aero-Gran-Compe brake set
- Suntour Superbe aero derailleurset
- Available in team color
- Frame heights: 52 to 62 ascending by 2 cm
The specification from that image gives me a ready made build sheet for my bike, and it gives me another build project to plan for. I prefer building bikes that are different to the expected standard of Campagnolo, so I’m looking forward to this one.
A Cautionary Note
It isn’t just this 531SL Aero bike that does it. Any SBDU 531SL frame will be beautifully light and has the potential to confuse people. The SBDU were building their 753 and 531SL frames in Metric diameter tubing. It is that lightness together with a smaller seat pin (smaller than 27.2mm) that can confuse some frame renovators. They incorrectly label some of these 531SL frames as Reynolds 753. The lightness, seat pin size and inclusion of a Cinelli BB can be indicators of a Metric Reynolds 753 SBDU. But in this case, they aren’t!
