I have a new arrival in the collection. There have been a few frames available lately but I’ve resisted buying them as they didn’t fit the ‘wanted list‘. But, after seeing the images for this frame, I had a hunch that this one did fit the list. So without asking any questions of the seller, without even knowing the SB frame number, and going off pictures alone, I tested my visual and technical knowledge on SBDU frames and bought it on a hunch. My hunches normally pay off, I’ve acquired some beautiful frames based on hunches so hopefully this one does too! Time to check and measure…
Earlier in the week I published a graphic on my Facebook page showing the gaps in my collection of SBDU frames based on ‘frame type’ and ‘tubing type’ – frame type means ‘Road’, ‘Track’ etc
I’m happy with both Randonneur models I own. I’m more than happy with my collection of Time Trial frames; not many people have an SBDU time trial frame and I have three. Maybe one day I’ll tick all the boxes. Track frames are much more rare so that collection is a slow burner. That leaves the Road bike category and as the graphic shows, I’ve nearly got a full house.
During it’s lifetime at Ilkeston the SBDU built with 531DB, 531SL, 531c, 531P, 753 & 753R/T. The vast majority of frames were built with either 531DB/531c or 753/753R. Not many 531SL/531P frames were built, so even though I have a couple of these, they are harder to track down, especially the early road version. 531P road frames became more popular in 1984/85 with models such as the 531 Pro Super and Super Chrome.
531SL (Special Lightweight) and it’s successor, 531P (Professional) were a lighter gauge of tube than 531, similar in weight to 753 but without the strength and heat treatment that 753 had. It was an excellent and cheaper alternative to 753, and often used because of it’s lightness for time trials. However, the long proven and ‘tried and tested’ tube was 531DB and the sought after tube was 753, so 531SL seemed to take a back seat. Not many were built, not many survive and not many surface for sale.
When I noticed this one shared on the internet, I recognised it as a possible frame to plug my only gap in the road bike section. It was listed as a 531 Professional 1983 57cm frame with a 27.2 seatpin; but it didn’t look like that. Key frame details pointed to something else. My hunch was that it was an early 80s 531SL. 531 Professional typically had double taper seat stays, this had single taper, a feature of earlier bikes. Although there was no picture of the BB, the side view of the frame looked suspiciously like a Cinelli CCM bottom bracket, it had side tabs on the BB shell. SBDU used this on early 80s metric tubed frames. It didn’t have drilled drop outs so almost certainly ruled out 753. It was described as the same weight as 753, so with all those clues, my hunch was that it was 531SL.
This is what came in the post today…
My first hunch was correct, it was a Cinelli BB. My second hunch was correct, it is SB4944 – this number corresponds to the very end of 1981 or the start of 1982 but definitely not 1983. It clearly shows signs or a respray so the Reynolds frame decal is incorrect, another hunch proven. The frame tubes measure as 26.0mm top tube and 28.0mm seat tube which is the metric version of Reynolds tubing – another correct hunch. So frame spec is…
SB4944 1982 Single taper seat stays 16mm - 10mm Oversized seat stay caps Round Oval Round chain stays 22mm - 11mm Prugnat 62D lugs Cinelli CCM BB Cinelli SCA fork crown Campagnolo 1010/B Portacatena drop outs Metric diameter tubing
This a a top quality and top of the range frame. I’m 90% certain that this is 531SL, I just need to try and confirm that so that I can label it correctly.
Frame weight is in the realm of 531SL and 753.
Fork weight isn’t important – most forks weigh the same because most wide oval fork blades are the same gauge of tubing. It is the choice of fork crown and length of steerer that normally makes the difference. Frame weight is the key value. Reynolds 531DB for this size frame would be approx 1950 – 2050 grams; the typical 753 gauge and 531SL is approx 1700 – 1800 grams. This frame, just as it was described by the seller, is light and in the 753/531SL range.
I now have a large library of SBDU information and articles, together with a good searchable database of frame features. That puts me in an excellent position to positively ID frames. The 1982 SBDU frameset catalogue, produced in November 1981 describes the following frames.
This is exactly the same period that SB4944 was built. The wording describes my frame exactly. 753 would normally have drilled 1010/B fork ends, mine doesn’t, it “…is near enough identical to the 753 road frameset…”.
Reynolds 531 Professional does not feature in any SBDU literature until the 1983 catalogue (produced in 1983). The significant differences between the 531 Professional ‘Super’ Road frame and the 531SL is that the 531 Professional frame uses a standard steel BB shell and not Cinelli. 531 Professional also used a double taper seat stay. Therefore, SB4944 matches the 1982 531SL Road frame specification. One final detail to differentiate between 531 and 753 is the stamping on the fork steerer.
If you look closely, you can see “Reynolds 531 Butted” and 16/13 which is the single butted gauge of a 531 steerer.
This is a snippet of the data I’ve collected about Reynolds tubing. This graphic shows Reynolds 531SL in both Imperial and Metric versions. All the tubes of this frame match the metric data in this table.
I’m 100% happy to call this frame a Team 531SL Road frame. 58cm with metric tubing taking a 26.8mm seat pin.
Based on what I’ve found out, I’ve updated my collection graphic. The road bike section for tubing is now complete.
So what is the plan for this frame..?
The plan is to clean up the frame as it is. It is marked and scratched but quite clean, so it is going to get a new lease of life with a Shimano 600AX group. This group set was produced in the early 80s and is perfect for this frame. Keep a look out for a blog post coming soon…
It is also frame number 13 in the collection… if I were superstitious, I should move on quickly and buy another!