@Spartak @User482 @Dogtrousers The sequel - having picked up my bike at last, and examined the evidence.
Well, exactly one month on from my ‘off’ I have recovered enough to drive. So I took the train up to Bristol/Keynsham to pick up my car (which had been recovered by a friend from the audax start) and then headed down to pick up my bike (which had been in the care of another friend who lives very close to the site of the accident). While there I drove up the hill (it's about 1:10): the scene of the accident - and slowly back down, recognising where my tyre had ‘blown’.
My posts describing/discussing the accident are here:
https://www.cyclechat.net/threads/t...challenge-chatzone.95264/page-84#post-4950192
https://www.cyclechat.net/threads/t...challenge-chatzone.95264/page-85#post-4952273
Apart from the front wheel my bike is relatively unscathed: the (1970s) Brooks ‘Competition’ saddle has been badly scuffed on the left back corner, but remains functional/useable; and the left hand STI is a bit scratched and was twisted in. The inner tube has a major snakebite in it: 11mm on one side and 9mm on the other, which will have caused/allowed the near instantaneous deflation I remember. There is a significant dink in one side of the rim where the puncture was. And there is damage to the left hand rim edge for about a third of the circumference, consistent with the rim attempting to roll on the road surface before saying ‘enough’. There is damage to the tyre sidewall in this area too. Of interest, the tyre had rotated about 20cm round the wheel (ie the maker’s logo was no longer aligned with the valve). I expect this happened when I tried to brake and the tyre gripped more on the road overcoming the friction between it and the rim.
All this supports my ‘analysis’ that coming down the hill, on the drops (always go on the drops downhill – much ‘stronger’ position and better leverage for braking), fingers lightly on both brakes, I suffered a near instant flat, and, after some immediate (swearing and) braking (which I remember) very shortly afterwards went over the bars landing supine, feet forward, first on my shoulder blade (crack) and that banged in to break ribs, one of which punctured my lung. My head then came down on its left side: the helmet is broken (cracked) and has friction damage. I was unconscious for an undetermined number of minutes. Because of how I fell, the helmet ‘wanted’ to come off: stopped from doing so by the helmet’s underchin strap which cut me and the sidestrap which had a go at my left ear (with a fair bit of blood (ears bleed easily)). This was the only damage to my head (lucky and protected) but my neck got a bit of a bashing – not surface but left/right and up/down stiffness/internal bruising. Substantial bruising (but not grazing) above my shoulder blade suggests I ‘bounced’ on that and serious grazing on my left arm/elbow and left hip suggests that I slid on those two main points till stationary. Other sites of grazing ‘are available’ – all now healed.
Lucky I was that others were right behind me (and called 999 etc). They thought I had gone down the hill ‘too fast’ (I have this on hearsay, third hand) and maybe this is so, but they will not have known that I’d suffered a puncture when descending. Whether this would have altered their judgement I know not. Whether a lesser speed and their riding skills would have allowed them to stay upright in the event of a flat will not be tested, I hope.
I do not know what caused the snakebite to the Continental tube. The tyre (Michelin Pro4 SC 25-622) was new on before London-Edinburgh-London and so had done about 2300km – I’d expect about 6000km from that make/model of tyre on the front. I had checked my tyres before the ride and the front was at 75psi (5psi more than the graph readout in Jan Heine’s BQ article: actual width 26.7mm, total load 85kg, front 38kg, rear 47kg). It is possible it had lost pressure during the 199km I had ridden. I checked the rear 31 days later: it was at 72spsi (same tyre make/model) - I had inflated it to 90psi before the ride). The road was clear and, having examined the surface by both driving up and down it and walking up and down the stretch where the flat occurred, the surface is good, with no potholes. The side of the road is a bank so I guess the only possibility is a largish stone: the sort of stone you can see and avoid as you ride down hills, I’d like to think. Maybe/clearly not this time.
What lessons can I learn from this incident?
1) A ‘fast’ puncture going at speed is likely to cause the rider to crash, especially if any braking or turning is needed.
2) Don’t apply any front brake (or release it if it’s already being used). Shift weight back to get as much effect from the back brake as possible.
3) Stay as straight as possible.
4) Check tyre pressures before each ride. Do a thumb check on each tyre at every stop (well, every couple of hours).
I have decided that the rim cannot be satisfactorily repaired and since the wheel/hub/spokes (Mavic MA3 on a Tiagra HB-4400) have done 25,000+km, it’s not worth lacing a new rim on. And I'm not sure how much damage has been done to the tyre sidewall so I'm reluctantly retiring that (to the bin) too. I have another similar front wheel: an Ambrosio Excursion rim on a 105 32 spoke hub which now has a new Continental GP 4 Seasons 28-622 tyre on, ready for when I’m able to ride again (hopefully in a fortnight or so). The Brooks saddle is off and being saved for long rides next year and the STI is straightened. All good. Almost off the pain killers now – just using for overnight comfort in an effort to achieve more sleep (still a challenge). Just need the bones to complete their healing, and to regain both mobility and strength in my left arm/shoulder and my neck.
Some may suggest I’m ‘overthinking’ this accident. But a month off work and 6+ weeks off the bike gives one ample time for overthinking. I hope some may find some of the facts and analysis interesting.
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