Frame weight… it’s often talked about, requested and used as a measure to try and determine tubing type. From my own experience I can see several factors that affect final weight and I frequently see through my own documentation process that frame weight can be very random and time and again I see that it can be impossible to correlate frame weight to frame size to frame tubing.
The Problem with Weight
I’m not talking about my own eternal struggle with the middle aged waistline here, rather the ability to predict frame weight. I wrote a brief post about frame weight two years ago and hit on the conclusion that frame weight was not an exact science. Since then I’ve collected a lot more frames and still see the same trends in frame weight.
Sometimes the largest frames can weigh the lightest and the smallest can be surprisingly heavy. Because of this unpredictability I’m going to summarise the weights of some of my SBDU frames in an attempt to give a reference point or guide on the subject of SBDU frame weight. I have frames in so many different sizes and different tubing types so the results should hopefully be interesting.
Frame weight is a product of frame design. It is only something that becomes a piece of data once the frame is built I.E. you don’t go to have a custom frame built and say “I want a 1600 gram frame please”; instead, what you do is say “I want a frame to fit my body and riding style and to ride in this type of race or event or activity”.
My research and hours of reading SBDU documents, certainly shows that weight wasn’t the factor that governed frame design. A custom frame was first and foremost designed to meet the needs of the rider in terms of geometry to fit their body measurements and then the tube selection was considered to suit their strength, riding style and intended use of the frame. The final frame weight only came as a result of those design choices, proving that frame weight is dependant on several design options.
People will ask me for the weight of a specific size frame built in a certain tube. This simple question will never have a simple answer. I can’t say with certainty that a frame WILL weigh (x) grams. The best I can do is say that for a given type of tubing, a frame of a certain size will weigh in the range of (x) grams to (y) grams.
Frame geometry is the first thing to affect weight. Just because two frames might share the length seat tube doesn’t mean that every other frame tube will be the same. Wheelbase, reach and brake clearance are just a few of the geometry options that can add or remove metal to a frame.
Frame features such as lugs, bottom bracket shells, braze on fittings, seat stay caps and even seat stay placement on the back or side of the seat lug can also have a small affect on frame weight.
But the one thing that probably has the greatest affect on frame weight is also the one thing that is the most difficult to judge, and that is tube gauge (tube wall thickness). The outer tube diameter can always be measured quite easily, even on a painted frame, but once a frame is built that tube gauge becomes a hidden mystery. And it isn’t just the tube gauge itself, you also have to consider the length of a butt on a tube, how long is that thicker or thinner section of tube?
It’s no wonder that weight isn’t an exact science!
Reynolds Tubing up to 1982
The SBDU built in at least two sets of Metric Reynolds 753 tube and each set had a different gauge. The difference in gauge can be differentiated by the seat pin size that each set will accept. The thinner and lighter gauge would use a 27.0mm seat pin (28mm outer diameter with 0.7mm/0.3mm single butted seat tube) while the heavier gauge 753 would use a 26.8mm seat pin (28mm outer diameter with 0.7mm/0.4mm single butted seat tube). Therefore two very similar looking 753 frames built from ‘Metric’ 753 and sharing the same 753 frame transfer and built with the same geometry and features can have different weights based only on that hidden tube gauge.
Even though I set the scene at the beginning and described how frame weight can be impossible to predict because of factors such as geometry, fittings and gauge, sometimes things do actually seem to follow a predictable pattern, and here is a great example of when frame weights can make perfect sense but only if you know the frames you are dealing with…
I have some 57cm 753 Metric tubed road frames in my collection that can demonstrate predictable weights with geometry, frame fittings and gauge. Two of these frames are very close together in frame production and are both built with almost identical frame parts and features, they also share exactly the same geometry. The only tiny difference is the style of brake bridge which I feel is negligible. These two only differ in gauge, therefore one will be predictably heavier than the other.
- SB3800 is a 57cm 1980 Metric 753 frame with a 26.8mm seatpin, RGF BB and Prugnat 62 lugs
- SB4059 is a 57cm 1980 Metric 753 frame with a 27.0mm seatpin, RGF BB and Prugnat 62 lugs
SB4059 with the lighter gauge tube has a frame weight of 1633 grams…
Here is the 57cm Metric 753 SB3800 with the heavier gauge tube…
SB3800 (in the image above) accepts a 26.8mm seat pin, an indication that it is built with the slightly thicker gauge of tube. Because it shares the same geometry, lugs, BB, seat stay arrangement, frame ends and braze on fittings as SB4059, the 106 gram weight difference has to be down to the thicker tube gauge, I can’t see another explanation.
SB5377 is another 57cm Metric 753 frame but it is slightly different and demonstrates how frame features and fittings can also have an affect on frame weight albeit not as much. SB5377 has the same geometry to SB4059 and accepts a 27.0mm pin, meaning they both share the lighter gauge tube. SB4059 weights 1633 grams but here is SB5377 on the scales…
Although both frames share the same gauge tubing and have exactly the same frame geometry, they differ because they have different frame features. SB5377 has a different BB shell, head lugs and additional braze on fittings such as a front changer and number tag. It is 54 grams heavier than SB4059. Because the tube gauge and geometry is the same between the two frames, this additional weight difference must be accounted for by the different frame fittings.
SB3800, SB4059 and SB5377 are clear examples of how frame weight can occasionally work out – if every frame was like this then life would be simple, it gives the impression that there is actually a correlation and that the weights are in some way predictable.
NOTE: Tube gauge selection was a part of the frame design process, the slightly thicker tube wall offered a slightly stiffer frame, sacrificing a small amount of weight was much better for bigger and stronger riders.
Those three Metric 753 frames above demonstrate a link of some kind between weight, tubing and frame fittings, but life is never that simple. Here is an example of how it can go wrong. The next two frames clearly demonstrate the entire point of my blog post and show how you can’t rely on frames to conform to any relational pattern when discussing weight.
- SB632 is a 52 cm 1976 Metric 753 Track Pursuit frame with a 27.0mm seatpin
- SB1500 is a 56 cm 1977 Metric 753 Time Trial frame with a 27.0mm seatpin
Both frames are built for a specialist purpose and the tubing type and gauge appear to be the same, they are both the lighter gauge 753 with Metric diameters and both accept a 27.0mm seatpin. They also share the same type RGF BB shell and Prugnat S4 head lugs. The only real visible difference is their physical frame size and slightly different seat stay caps.
SB1500 is a much larger frame and has a 56cm seat tube. SB632 is a small 52cm frame. Even if SB1500 was built to the SBDU stock geometry dimensions, it will still have a much longer top tube, head tube and down tube than SB632. The expectation given the large difference in frame size is that SB1500 WILL be heavier than SB632 – the scales however, tell a different story…
This is the 52cm SB632 – Metric 753 with 27.0mm seat pin (1580 grams)…
If you were going to try and predict the weight of SB1500, which is 4cm larger, you wouldn’t be wrong in thinking that it would come in at over 1600 grams (at least).
But you would be wrong, here is SB1500; remember, this is the same Metric 753 with 27.0mm seat pin but 4cm larger… it has an almost identical weight.
So the much bigger frame is more or less the same weight as the smaller frame even though there is 4 cm difference on the seat tube – how does that even work? Is the smaller frame unusually heavy or is it the larger frame that is unusually light?
Because the seat tube gauge and 99% of the frame features are the same between the two frames, there has to be something different between the gauge of the other tubes in these frames, I just don’t know how to explain it other than thinking that top tubes and down tubes also had several gauge options and were chosen specifically to suit the rider and use.
SB2692 is another 56cm Metric 753 27.0mm frame but comes in at 1629 grams. This is the weight I would have predicted for SB1500.
SB2692 is virtually the same as SB1500 but is heavier which makes me think that there has to be something different happening with the tube gauge on SB1500. I have another 56cm Metric 753 Time Trial frame, SB3327, which has a 26.8mm seat pin and a frame weight of 1789 grams
SB632 and SB1500 are part of the reason why I can never give anything other than a ‘range’ of frame weights rather than something more accurate.
The SBDU were also in a unique position with Reynolds 753, as they had access to something different to the standard Metric diameter tubing, they also had Imperial diameter 753. These early Imperial frames weren’t common, but shared the same 753 frame transfer.
SH377T and SB664 are beautiful examples of this type of frame. The early Imperial version of 753 is often identifiable by Carlton Capella lugs and a 27.2mm seat pin together with the Reynolds 753 frame transfer. This is a similar type of tube that was later released under the tag of Reynolds 753R. Because it has a larger outer diameter seat and down tube and thicker gauge tubing, these frames are usually heavier than their Metric equivalents.
SH377T is a 56.5cm frame and has a weight of 1799 grams – that is much heavier than my 57cm Metric 753 frames. SB664 is a large frame with a 61cm seat tube and has a weight of 1888 grams.
So to summarise frame weights for those SBDU frames that display that iconic Reynolds 753 frame transfer, I have frame weights from approx 1580 grams up to 1800 grams.
In the same period as Metric 753, the SBDU built with Imperial Reynolds 531 Double Butted (531DB) tubing. 531DB had lots of different characteristics that made it more appropriate for other frames and uses, but its major difference to 753 apart from tensile strength was its weight, it was a much heavier tubeset.
Here is SB1861, a 54cm 531DB frame from 1977…
This isn’t just a few grams heavier than 753, it is significantly heavier.
To give a good comparison between Metric 753 and Imperial 531DB I can use my 57cm frames again; SB4059 (the 57cm Metric 753 road frame) which I demonstrated earlier had a weight of 1633 grams, but here is SB518 (a 57cm Imperial 531DB frame from 1976)…
SB518 comes in at 2209 grams, that is a massive 576 grams heavier than a similar size Metric 753 frame. That is enough of a difference to feel just by handling a frame.
So in the era of Metric 753 and Imperial 531DB, there was a noticeable difference between these two tubesets. That is important to note when you also want to compare later period 753R and 531c frames.
Before leaving the topic of this earlier period of Reynolds Metric 753 and Imperial 531DB, I want to mention a tubeset that is regularly mis-badged due to its weight. It may not have been as popular as 753, but Metric diameter 531 Special Lightweight (531SL) was just as light, it was ultra thin 531 tubing. It had a similar weight to 753 but the strength of 531.
753 could be built in thin gauge because of the heat treated nature of the tubing which almost doubled the strength of the tube. 531SL did not have that strength because it wasn’t heat treated, it was just thin. Because of this, it was probably quite a specialist tube that would not suit all people and all uses.
The frames the SBDU would build from it could look and feel exactly the same as the 753 SB framesets. Both tube sets sat within the same weight range and could both share a similar 26.8 diameter seat pin. If a frame isn’t found in original paint or for some reason it doesn’t have the original Reynolds frame transfer attached to it, then I’ve seen several restorers make a mistake and label 531SL incorrectly as 753.
There was a period during 1981 and 1982 where the Team 531SL SBDU frame was 99.9% identical in frame features to the Team 753 Road frame, the SBDU documentation from 1982 used the words “…near enough identical…”
My own SB4944 is one of several I have seen in the SB4800 – SB5500 range to be built from Reynolds 531SL with a top mounted down tube lever fitting (normally fitted with Suntour Symmetric levers). These frames are a 99% match to the same period 753 frame – they share the same Prugnat 62D head lugs, Cinelli BB shell and Cinelli SCA fork crown. The only difference is the lack of additional drillings on the rear Campagnolo 1010/B frame ends on the 531SL frame.
SB4944 is a large 58cm 531SL frame but its weight of 1780 grams is still in the acceptable range when quoting for Metric Reynolds 753 (with the thicker gauge tube). This frame is only slightly heavier than the 57cm SB3800 753 frame at 1739 grams.
With the two main tubesets of 753 and 531DB being so different, it is no surprise that the more rare and similar weight 531SL was and still is often confused for 753. You can hopefully see the clear problem of defining tubing type based on frame weight.
Reynolds Tubing 1982 Onward
Moving onto Imperial 753R. The reputation that the earlier Metric 753 had of being ultra light and ultra thin will probably always exist in the heads of those that knew it, so no matter what type of 753 is being discussed, it will always be associated with wafer thin tubing. However, 753R was a totally different tubeset. It still retained the 0.7mm butted tube end but the thinner centre section was increased from 0.3 to 0.5mm, and that was also combined with the increase in seat tube and down tube diameter from 28.0mm to 28.6mm.
Many people picking up a 753R frame for the first time will often remark on the unexpected heavy weight and be confused about it being either 753R or 531c. The larger diameter tube of 753R combined with the increased wall thickness will result in a heavier frame when compared to a similar size Metric 753. Therefore, a typical 753R frame weight will fall into a slightly different range.
I have 753R frames ranging from 1648 grams to 1876 grams. The following three frames are built from 753R and all require a 27.2mm seat pin.
Note how the larger 57cm frame (SB6398) is lighter than the 54cm frame – this is mainly due to measurable geometry as SB6398 has a very short top tube (less metal = less weight); but is there also something going on with hidden tube gauge?
Reynolds 531c was also released at the same time as 753R. The overall tubeset weight of 531c was lighter than 531DB. A clear comparison is demonstrated between SB518 seen earlier (a 57cm 531DB frame weighing 2209 grams) and SB6560 below (a 57cm 531c frame)…
1906 grams is a good saving on the 2209 grams of the similar size 531DB frame. And this is where you see another problem introduced for defining tubing type based on frame weight.
The revamped 753R tube didn’t just change from Metric to Imperial diameter, it also beefed up the tube gauge. The table below shows 753R compared to Metric 753 and 531c
|Tubing||Top Tube||Down Tube||Seat Tube|
This is a clear comparison showing how different 753R was to Metric 753, but how close it was to 531c. Those thicker tube wall dimensions on 753R resulted in a slightly heavier but also stiffer tube. However, those same beefed up tube walls also bring it very close to 531c dimensions meaning that the weight between each tubeset was very close.
So whereas a Metric 753 frame is noticeably different to a 531DB frame in weight, a 753R frame can on occasion be difficult to differentiate from 531c.
You’re now probably wondering where Reynolds 531 Professional (531P) sits on the weight scales. You have to be careful with the type of 531P used by the SBDU as they started with Metric 531P tubing but most of the later 531P frames were Imperial. The two 531P road frames I have are from 1985 and are Imperial, so I’m going to compare these Imperial 531P frames to Imperial 753R and Imperial 531c.
This is SB7393, a 57cm 1985 531P frame…
And here is SB7219, a 58cm 1985 531P…
These 531P frames are on the heavier side of 753R frames just as 531SL was on the heavier side of Metric 753. A 531P frame could easily be confused for 753R.
All the information I have from various official Reynolds sources list 531P with the same tube gauge as 753R – I did find one source that listed a different down tube gauge but that wasn’t official Reynolds. But if you look at the example tube weights quoted by Reynolds, 753R is always quoted as 50 to 100 grams lighter than 531P. How can the same gauge tube be lighter?
My theory on how 753R can be lighter but have the same gauge is that 753R must have had a different butted profile/length of butt. 753R was significantly stronger than 531P and may not have required the same length of butting as 531P. Whereas 531P was simply thin 531c with the same 531c strength, meaning a longer butted section would be required to keep sufficient strength at the frame joints.
Although several documents list Reynolds frame set weights, they don’t give any context to what a ‘set’ consists of. Is a ‘set’ just a set of tubes with no lugs? Is it a set of tubes at the standard length? Or is the weight quoted an actual frame weight? If it is a frame weight then what size? There are two Reynolds documents from the 1982-1987 period that list different weights..
|Document Name||753R (g)||531P (g)||531c (g)|
|Reynolds Tube Talk||1650||1700||1800|
|From Raw Material to Racing Certainty||1800||1900||2050|
Those two documents have a very different idea of weight. Maybe the top row is actually just the tubes and maybe the bottom row is a complete frame? Possibly 58.5cm? I do wish documents like this took a bit more time and quantified their data.
I haven’t mentioned forks throughout this post. I still weigh the fork when I document a frame, but I don’t compare the data or try and use it to differentiate tubing.
The later wide oval fork blades on 753R, 531P and 531c were all the same gauge, a taper gauge of 1.0/0.5. There are a few small factors that can slightly affect fork weight, but overall, forks generally come in quite close. Here are some of those factors…
- Brake clearance will mean a longer or shorter fork blade
- Internal and External fork crowns will differ in weight
- A bigger frame will have a longer steerer and therefore a heavier fork
- 753 steerer tubes up to a point are plain gauge, 531 is single butted and therefore heavier
I’ve listed approx 30 frames. There are still some bikes in the collection that either haven’t been taken apart yet or I just haven’t had the chance to weigh. The frames I have listed are in ascending weight order and show the significant frame features of tubing type, tubing diameter, seat pin size, weight, seat stay type, lug type, BB type and Fork Ends…
As you can see, it is a mixed up set of data with different tubing types and sizes randomly spread through the table.
A better way to visualise the data is to see it spread out on a chart, this is the data up to 1950 grams…
I can’t quite get the size and resolution crisp enough on here so please feel free to save and download these in order to see the detail. My overwhelming thought on the image above is just how crowded the range is from 1600 gram to 1800 gram and from 54cm to 61cm. There are three 57cm frames in 753, 531SL and 531c all within 70 grams of each other; that just shows how difficult it is to determine frame tubing based on frame weight.
This is the other end of the chart, dominated by 531 Double Butted tubed frames.
I looked back on the many many drafts I’ve written for this post and realised that I first put pen to paper (I mean finger to keyboard) in February 2018. Since then I’ve formed opinions, changed opinions, scratched my head at the results, gave up writing about it, started writing again, got confused about the data, kept on topic, wandered off on several tangents and finally just decided to fill the post with my actual data and let you lot try and figure out your own meaningful insights from everything I present here.
But I do think I need to give you my own conclusion, and it is that frame weight really isn’t the best way to judge tubing type on an SBDU frame. It can work, but you need to be comparing significantly different gauge tubes such as the thinnest gauge Metric 753 with Imperial 531DB, essentially the two extreme ends of the scale; anything else is too close to call.
Some of the weight differences between different tubing types are so small, too small to make a meaningful decision; 50 to 100 grams is such a small amount of weight but could be the difference between 753 and 531SL or 753R and 531P. In some cases you may only have 30 grams between 753R, 531P and 531c. Just to put 30 – 50 grams into context, it is the weight of a lightweight aluminium bottle cage!
What about 100 grams? It sounds a lot doesn’t it, it can be the difference between a 753R frame and 531c frame… but put into context, it is only the weight of a set of steel toe clips!
A much better way of defining tubing type on an SBDU frame, and the method I prefer to use, is to investigate frame details. The SBDU were a custom unit but they also kept close to their frameset documents and designs. Visual clues about BB type, seat pin size, fork crowns and lugs are much more accurate than trying to judge frame weight. Earlier frames are far easier to define, later frames can be much more tricky. But because of that ‘custom’ word, there is always a slight possibility that different fittings were mixed in and used during the build making things even harder.
Assess as much as you possibly can, include frame weight as a factor, but just don’t form your final opinion around it.
One final word for the weight weenies… if you are looking for a frame simply to get one as light as possible then firstly, you are doing this all wrong, secondly, be very careful what you add to your bike. I measured a few items that most people will carry on a bike. I weighed 2 x alloy bottle cages, 2 x full 750ml bottles and my tool bag (containing my spare tubes, levers, CO2, pump, chain tool and a few allen keys). Fitting 2 cages with full bottles will add 1690 grams, the equivalent of strapping a spare 753 frame to your bike. If you also add on a tool kit, you take that extra weight up to 2277 grams, the equivalent of a 531DB frame strapped to your bike. Even if you drink most of the contents of the bottles, you still have almost a kilo of extra weight.
Weight is not the driving factor of bike design, get a bike that fits you well and get a bike with geometry and design features that suit your purpose – it will not only be comfortable to ride, it will also meet all your needs.
One final word to those on a constant quest to find the 753 of their dreams. There is nothing wrong with having that mission, these SB 753 frames are beautiful things. But always remember, that frame you find was almost certainly built for someone else. It was built for their shape and riding style and probably built for use on the best roads on an occasional basis. Don’t just look at seat tube size, make sure you look at stand over height too and more importantly, check that top tube length. I have so many frames that have either longer than normal or shorter than normal top tubes – that measurement can really make the difference.
The best riding frames I have are 531c. My 531c SB7660 Randonneur is a dream to ride, it almost moves itself down the road.
One final word for the few that say they have the ability to flick a tube and tell you the type of steel… Darth Vader must be your father, as that is surely a Jedi skill?
For uniformity in my results, I always weigh frames on the same scales and in the same location and with ALL fittings removed. Most of the frames were weighed again for the purpose of this post to ensure that the readings were as accurate as possible.