Blog Featured Posts H Reference Reynolds 753 Reynolds 753 Information Road SB1948 SBDU Ilkeston

1978 Raleigh SBDU Reynolds 753 Special Order 61cm – New Arrival

I’m Slowly settling back into WordPress with a beautiful example of a Raleigh SBDU bike. A special order dating to 1978. I love finding bikes in this original condition, unmolested, and from the original owner. SB1948 has lots of little oddities to explore. This bike should be a good exercise in reminding me about all the quirks of these frames and I’ll revisit some research I’ve done over the years throughout this post.

A little background

I bought SB1948 from John, the original owner. Sadly this is so long ago now, and the initial messages we shared on eBay have gone, things are still a bit hazy in my head. However, I do remember some parts of the story from John, telling me about the paint. John asked for a particular paint, Eggshell Black, but it was a colour that wasn’t offered so it looked like he wasn’t going to get it. It wasn’t until there was a delay in the build that he was told he could have that finish. Sorry John if that story is a little off, I’m going off some faint memories from a little while ago.

The Eggshell finish, from what I know is actually based on how an egg shell appears, the definition is a low sheen soft smooth finish. The paint is currently sitting under a couple of decades of dirt and dust, but I can see a glimpse of how lovely the black finish looks. It is certainly something I’ve not seen much before, if ever, on an SBDU.

It may have had a replacement chain at some point, and of course the clipless pedals that were on the bike when I bought it were a nod to more modern pedalling convenience.

Yes that is a triple TA chainset, and it is rocking a huge 56T outer ring. All of that chain is running through a lovely Campagnolo Rally rear derailleur with a 6 speed block – that block still sounds sweet when it’s spinning. That’s how John said he liked his gearing.

Special Order SB1948 Reynolds 753 1978 Bike
Special Order SB1948 Reynolds 753 1978 Gearing

And that’s about as much as I know about this bike at the moment. So I’m looking forward to getting into the details and finding out more. Let’s start with some basics.

Frame number

SB1948 just creeps into the start of 1978.

Specialist Bicycle Development Unit (SBDU) Frame Numbers & Dates (Ilkeston Period)

YearStart NumberEnd NumberLocation
1987SB8431SB8432 - SB8438Ilkeston
1987SB8432 - SB8438-Nottingham
** Frame Numbers & Corresponding Dates: Last Updated March 2019

For more info on how I arrived at the different periods in that table, have a look at this blog post.

Special order H reference

You will also notice the H reference of 381 tucked in beside the frame size of 61.

H381 SB1948 Reynolds 753 1978 Frame Number
H381 SB1948 Reynolds 753 1978 Frame Number

Based on the other H stamped frames I have, I should also see ‘381’ stamped on the fork when this bike is pulled apart soon. At this time in Ilkeston production the H reference was duplicated on the fork column minus the ‘H’. Here is an old post I wrote about the H ref number – I probably need to revisit this at some point and update it with the range of SB numbers it applied to. The H ref existed for a small period of time as a stamped reference on SB frames. Although it disappeared from frames, it was still evident as a piece of data on SBDU build sheets.

Essentially, if you see this on a frame, it can indicate some type of customisation from the normal ‘stock’ build. Once the H ref disappeared from frames, that visible indicator was lost, even though on later frames these tweaks still happened in individual design in some way.

This is a reminder that if you are buying an SBDU bike, you are almost certainly buying a frame designed for a specific person. I find the most useful measurement on an SBDU is top tube length, and not seat tube length. I have several frames each sharing the same seat tube measurement, but with varying top tubes. That critical top tube length can make the difference to a frame being ridable or not.

My question at this point is… Is the paint colour the difference on this frame, and the reason for the H reference?

Frame features

SB1948 displays the various different features you would expect to see in this period of Ilkeston 753 production.

  • Single taper seat stays & oversize seat stay caps
  • RGF bottom bracket with 4 milled slots
  • Over the BB cable guides
  • Drilled Campagnolo 1010/B frame ends with Portacatena fittings
  • Prugnat S4 lugs
  • External semi sloping fork crown
  • Band on gear levers and top tube cable clips
  • Nutted brake calipers

Apart from the paint colour and transfers, there is nothing visually different to what I’d expect about this bike. The one note I’d make is that the head tube displays the large oval head badge transfer and not the more typical 3 pin badge.

H381 SB1948 Reynolds 753 1978 Details


I don’t normally make a point of focussing on wheels, but in this case, I’ll make an exception, as SB1948 is fitted with 27″ Mavic. The rims are laced with chrome spokes and large flange Campagnolo Record hubs.

It is the diameter that is of interest. There isn’t much original documentation available regarding options on wheel size and the options for having frames built for specific sizes. All I can go off are the frames and bikes that I have, and most, if not all of these are 700c/sprints. There is SBDU documentation that states the normal brake clearance of Piccolo, but not much about normal or alternate wheel size.

H381 SB1948 Reynolds 753 1978 Mavic Module 3

This frame looks as though it would certainly take smaller diameter 700c, but it would be a push with the brake blocks at the very bottom of the slot. It looks as though the 27″ (630) was the size SB1948 was built for.

So is the 27″ wheel size another factor for the H reference?


The tyres are definately too far gone to reuse. They are a Clement that I’ve not seen before! Clement Pneumatici Tipo Corsa.

H381 SB1948 Reynolds 753 1978 Clement Tyres


Apart from the gearing requirements needing that triple TA and Rally derailleur, I’d say this was quite typical in terms of components. The EDCO Competition headset was fitted to many SBDU 753 frames, then Super Record took over. This EDCO headset is still super smooth and rotates side to side without any noise or interference.

The brake levers, calipers, front derailleur, hubs, seat pin and gear levers are all Record. Based on their features most date to before the Consumer Product Safety Commission changes, commonly called pre-C.P.S.C. So they show the straight QR levers on the hubs and calipers and the lip free front derailleur cage.

The bars and stem are earlier versions of Cinelli (1R /Record and Giro D’Italia). The saddle is a Cinelli Unicanitor – a saddle that shows its cost of £11.95!

Special Order SB1948 Reynolds 753 1978 Parts
Special Order SB1948 Reynolds 753 1978 Cinelli Saddle

One thing to get into the habit of doing is checking small details. I’ve become very good at spotting details and running the detail through my head, comparing that detail to other features and searching for any correlation. Sometimes things come back as a match, and sometimes a flag pops up to show something more to check.

In this case it is the seat pin diameter and type and age of Reynolds 753. Is this another candidate for the H reference?

H381 SB1948 Reynolds 753 1978 Seatpin Size

Seat pin diameter and tubing type

Metric and Imperial diameter tubing

Back in the day, when not much was known about the SBDU and their use of Reynolds 753, there was an assumed distinction made between Metric and Imperial 753 tubing. Metric diameter was seen as the type used from the introduction of 753, through to 1982/83 when Imperial diameter 753R was introduced.

Metric was thought to have the older style Reynolds transfer and known to have seat pin sizes of either 27.0mm or 26.8mm. 753R (imperial) came with an updated transfer and was known for seat pins to be either 27.2mm or 27.4mm. There was always online debate on seat pin size on 753 frames where people would try and shoe horn actual physical evidence of seat pin size into the assumed knowledge of what was available in terms of tubing.

Metric tubing has the following diameters

TubeDiameter (mm)Diameter (Equivalent inch)
Top Tube26.0-
Seat Tube28.0-
Down Tube28.0-

Imperial has the following diameters

TubeDiameter (Inch)Diameter (Equivalent mm)
Top Tube125.4
Seat Tube1 1/828.6
Down Tube1 1/828.6

SB1948 tubing

So based on the old assumptions, my 753 frame transfer is an indication of frame age and therefore tubing type – the assumption would be Metric tubing. However, the 27.2mm seat pin size contradicts the assumption and indicates Imperial tubing.

And sure enough, a quick measure with a digital vernier shows Imperial diameter frame tubes!

Not a great deal is known about the variety of tubing gauges available to the SBDU. They were in a unique position as the team who worked with Reynolds to create the tubing. According to Gerald O’Donovan in a later interview, they started with a blank sheet of paper when designing 753. Who knows what went on to be commercially available from Reynolds to other builders and what the SBDU actually created?

The tubing gauge was considered for the rider and the type of riding they were planning. In 1978, for 753, that would normally be the lighter version of 0.7/0.3 or the slightly heavier weight and gauge tube using 0.7/0.4 (27mm and 26.8mm seat pin respectively).

A compromise for a heavier or stronger rider could be the heavier gauge Metric (26.8). A compromise between frame weight and frame stiffness. But it is clear that another option available to the SBDU pre ’82 was an Imperial diameter 753. Imperial tubing is again that same compromise. You get something significantly lighter than the 531 butted tubing, and you get a frame with 50% more strength than 531 butted tubing, and a wider diameter tube for stiffness.

As with everything on my blog, I like to speak from experience, so it was only when I started to acquire some Imperial tubed 753 frames from the ‘Metric era’, that I could finally start to sort out the myths surrounding what tubing was available. These Imperial tubed frames often came in the guise of modified Carlton Capella lugged frames such as SB664 or SB1625. Even Hennie Kuiper’s 1976 TdF frame is Imperial 753. Hennie’s frame also has the Capella lugs. Then I received SB1995, a renovated early 1978 frame which matches SB1948, an Imperial tubed frame from the ‘Metric era’ with Prugnat S4 lugs. SB1995 takes the larger 27.4mm seat pin.

SB1995 SBDU Ilkeston Reynolds 753 Road Frame Transfer Details
SB1995 SBDU Ilkeston Reynolds 753 Imperial Diameter Tubing


There could be 3 possible reasons for the H reference on SB1948. That is the paint, wheel size and tubing type. The paint and tubing type are the stronger candidates, the wheel size less so.

Whatever the story is behind this bike, it certainly has presence. It’s size and colour combined with that large gear and derailleur certainly make this bike stand out from the norm!

I can’t wait to get the dirt and grime off the paint and see how this frame comes to life.

SB1948 1978 SBDU Ilkeston Reynolds 753


  1. I hope maybe one day your be able to get a line on the early Frames numbers for the R frames .
    On subject of metric and imperial my seat pin is 26.8 on my 753R Frame Number 5590 made to measure for me in late 1982 , At the time “God” did ask me if I wanted the new style of frame, i can only assume that it is one of earliest R frames and imperial Tubing which i cannot confirm ,but can confirm i was not aware at the time that there was a tubing size change and just always thought the R was for Road . All the best for the Future I.M.P

  2. Glad to see you back, and thank you for a very enjoyable write up about SB1948. Rest well and all the best.

  3. Hi,
    Am blown away the black SBDU is a “factory triple” (still no eyelets as all other triple’s would have).
    Assume only SBDU with “triple bottom bracket spindle” also.
    Before photo of your’s, I would have never thought a SBDU was ever built as a triple.
    Thanks for sharing (very interesting ) photo’s.

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