Following on from my previous blog posts about SBDU fork ends and seat stay caps, here is another short post in a series I’m writing about individual areas of SBDU frame design. This time I’ve chosen to write about gear levers, or more precisely, where they are positioned on the downtube. I’m quite sure that many people have never even considered this, after all, they are just levers mounted on a tube. And let’s face it, who actually does think about the small stuff like this… apart from me!
I find this type of minutiae really helpful when I’m trying to identify or date a frame. Knowing about these small details and being able to combine several together allows me to build a picture and overall assessment of a frame, even spotting things like repaints and repairs.
The SBDU changed the location of their gear lever bosses during the Ilkeston period. I touched on this when I wrote about the TI-Raleigh transfer scheme and the position of the 1980 TDF down tube transfer. Gear lever bosses started to appear on SB frames from approx SB2200’ish – that places the date at the mid to latter part of 1978. Their early position was a little inconsistent but always appeared to be fitted in the region of 115mm from the back of the head tube.
You can see in the image above that there is ample room between the long point of the head lug and the lever boss to fit the 1980 TDF transfer – that transfer started to appear on frames near the end of 1980. I’ve noted measurements of gear lever bosses between 105mm and 120mm during the period from 1978 to 1983. The following three frames are 1979/1980/1981.
Looking at the side view of an SBDU bike of this period, it is clear to see how far the gear levers sit along the down tube.
The position of the lever boss remained within this 105-120mm range during the 1982/1983 period. This is SB5464 (1982) and SB5794 (1983) with an average measurement of 105mm…
But then 1984 came along and the position changed, not a little, but a lot! The central position of the lever boss was moved by approx 45mm – this meant that the lever boss was now positioned at 70mm behind the head tube. This is SB6398, note from the same side view of an SBDU bike that the gear lever has been positioned much further up the down tube, and the tip of the lever is starting to overlap the head tube…
This change in position wasn’t just a ‘blip’ on a couple of frames, it lasted throughout the 1984 period. Here is SB6560…
I repaired the damage on this frame by removing the old stubs and fitting new bosses. But before starting any work I made sure I measured the original position before removing the damaged remains. So these new bosses were fitted in the exact original position.
And just to show that this measurement continued throughout 1984, here is SB6827, a later ’84 frame.
You can still see the tip of the gear lever overlapping the head tube. The image above clearly demonstrated how the 1980 TDF transfer had to move – there was no longer any space for it between the tip of the long point lug and lever bosses. Even with the shorter point Cinelli lug of the Services des Courses frame of SB6560 there is very little room.
1985 saw a new position for lever bosses. This also appeared to be the last time the SBDU moved them. Frames dating to the start of 1985 had lever bosses positioned at approx 85mm from the back of the head tube – that additional 15mm was just enough to drop the levers back a little from the head tube and allowed some extra space for the TDF transfer.
That small change of 15mm, an increase from 70 to 85mm, brought the levers away from the head tube.
This is SB8851 which is an SBDU Nottingham built frame. This late SB number demonstrates that the 85mm measurement became the norm in 1985 and lasted throughout the final years of Ilkeston and into the period at Nottingham. My three SBDU Nottingham frames, which are all different sizes, have the bosses set at 85mm.
Here are the 3 positions I’ve documented during the SBDU period…
On the left is the earlier position typically set at approx 115mm behind the head tube (variations can be seen between 105 and 120mm). In the centre is the 1984 position with the lever pushed right up so the tip of the lever is overlapping the head tube. The distance from the back of the head tube to the centre of the lever boss is 70mm. The right hand images are from 1985 onward, the position of the boss has been relaxed by 15mm and set at 85mm from behind the head tube.
If you have an early frame without brazed on lever bosses and are wondering where to fit the levers, I would recommend fitting the band in the 115-120mm region. That will place your levers in a similar position to the earliest braze on fitting – the tips of the levers should fall somewhere near the point of the head lug.
Although I have all these measurements documented, I really don’t know why the changes were made. I could speculate and probably end up being wrong. But if I had to think of a legitimate reason why the bosses were moved then these two possible scenarios sound like they have some reasoning behind them…
Were the changes related to moving the bosses (and heat required for brazing) away from the thinner centre section and onto the thicker butted end of the tube? Or was it associated to some kind of change in frame spec, perhaps linked to the professional team? At the start of 1984 it would have been the Panasonic Raleigh team; was the position of the lever boss better suited to the layout of the new transfer scheme if it was higher up the tube?
Regardless of what the actual reason might have been, I just like to note and share these SBDU specific details because someone, somewhere like me, could find it useful.