Possible causes of my spill...?

Hi Guys,

On Tuesday morning my bike and I had a fairly hard liaison with the road, but I can’t come to a conclusion as to the cause.

So if I outline the scenario, I would welcome your ideas.

ME: Been riding since 1998, started on a moped commuting 4 miles twice a day in Central London. Progressed up the ranks and been riding my current bike since Sept 2002 (full test passed May 2002). August 2009 moved to Hampshire and commute to work - which is a 2 mile journey on urban residential roads with 30 & 40 limits. I’m a confident & cautious biker, do not take unecessary risks, have no issues riding in the wet/rain, filter where safe to do so (I won’t sit in a jam if there is space to get through) and do like bursts of speed on appropriate roads. In my riding experience on my current bike there have been a few occasions of doing emergency stops due to emerging cars and a couple of loss of grip scenarios fully recovered, one incident of dropping the bike while mounting a kerb. But no other accidents/incidents.

BIKE: 1990 Honda CB1, standard spec, unrestricted, passed MOT 21/SEP/2010 - tyres/brakes good condition.

CONDITIONS: Wet road surface - not rained in the previous half hour or so, no standing water at incident site. No wind, cloudy but visibility perfect.


Sequence of events;

  1. 7.35am set off on my usual route to work, north along Coleford Bridge Road and approaching the double roundabouts on the overpass of the A331.
  2. I crossed over the A331 in the left hand lane negotiating both roundabouts and took the left hand turn off of the second roudabout towards Farnborough.
  3. I went up the humpback bridge and down the other side where I saw 4 cars waiting at the T junction of Coleford Bridge Road and Rectory Road.
  4. I overtook two cars on the right but within the centre line with my left indicator on.
  5. A gap opened up and I manouvered into it and approached the mouth of the junction well to the left and dead slow.
  6. Still moving dead slow I checked right , then checked left , then I did a final right check .
  7. I released the brakes fully, applied gentle throttle, completed the turn and cancelled the left indicator - then I applied more throttle as there was a good gap in front of me and accelerated to around 25mph - but not more.
  8. Found myself going down leftwards almost in an instant. All I remember is being upright, then hitting the road, looking up and picking myself up.
  9. The chap in the car behind was stopped 3-4 metres behind me, walked me onto the pavement, asked me questions if I have any pain or obvious injuries (he had a firemans jumper on so I guess he knew how to deal with incidents).
  10. Together with a driver from the first oncoming car they moved the bike onto the pavement and the fireman chap stayed with me and decided I was in shock/disorientated and organised an ambulance.
  11. Half an hour in hospital and I was given the all clear, got tubigrip for my left shin which was hurting a bit and looked like I will be having a prize winning bruise - apart from that just various aches - nothing broken - no head injuries, except bike and pride.

BIKE DAMAGE: Handle bar end-weight sheared off with mounting point, mirror mounting point snapped off clutch lever assembly, clutch lever snapped in half, left hand side handlebar switch unit-half broken off, lefthand side steering travel stop tab bent/snapped, dent in fuel tank where left handle bar has travelled excessively, gear change lever bent inwards, footpeg bent diagonally down towards the rear, rear side fairing scratched, cargo net covering rear of seat sheared down its middle.

Your thoughts please…



Pure speculation obviously, but low speed offs like that are often associated with diesel spill. And I dare say the same thing has crossed your mind, too.

Unless there is evidence of either a collision or a sudden catastrophic mechanical failure with the bike - front caliper seized on, chain breaking, front tyre blow-out etc - then it is a fair assumption that with a sudden loss of grip at a relatively low speed and with no great cornering forces at work, diesel is the culprit. Losing the front would have you down in an instant; losing the back you would have known about.

It is quite possible that you will never know for certain what caused your tyres to lose grip - even if you go back there in the morning for a look any diesel or other contaminant could well have disappeared.

Glad you’re okay - and try not to fret about it :wink:

Sounds like you fell off but at least it was low speed with friendly people to help out. Might have been deisel though that is always a fallback scenario, suspect 65mph was just a tad fast for said roundabout though in retrospect we`ve taken it faster.

The 3 or 4 times iv ended up on my ass in the road and thought…" how did i get here so fast" were because i gassed it too hard on a slippery surface or had stone cold tyre.

come to think of it iv thought that while flying threw the air followed by “oh this may hurt!”

glad your ok and by the way CB1’s are great i have one as my winter bike :cool: dont spoze you have a tail light for one do you?

Sounds like diesel or cold tyre or most likely both! Glad to hear your back on your feet.

The front going happens really quickly and generally you’re on you’re arse before you know anything is even wrong. The back does tend to send a postcard to warn you before it goes.

The last few days it’s been getting very slimy out there. I’ve accidentally span up the rear wheel on my fire breathing 60BHP tub of lard Africa twin three times in the last week.

were you banked over at all? Just that you said you were upright and had completed the turn?

I guess then when you opened the throttle, with cold tyres slightly wet and diesel that would make the back step out and you would be where you found yourself. So agree with the others. Suppose if you have the contact details of the helpful people you could ask them what happened…

Diesel could easily come out onto the road on a tight corner like that, a very full tank can overspill…Do buses use that road?

Fact of biking life tho that, glad you are ok

Thank you for your replies. I will address all below.At that point I would have only covered 1.5 miles at 30-35 mph on rough asphault roads, so the tyres would probably have been cold - just starting to warm up.

I was travelling upright, having completed the left turn, I’m certain I didn’t jerk the throttle sharply as 20 metres up the road is a junction with a crossing on it. Yes, it is a small bus route (2 busses an hour).

There is no obvious evidence of a collision. I didn’t inspect the car behind me thoroughly but there was no obvious damage on the front of it and I would have thought the driver would have said or the driver of the on-comming car would have said something. Again no obvious signs of mechanical failure, I picked up the bike that night and walked it home - it starts, the brakes work, chain & tyres are ok.

There was a patch of something 1 metre ahead of where I hit the road. I walked past the spot two mornings now with similar conditions, wet road surface etc. At the junction there are a couple of small patches of something but further up the road (where I came off) surface looks clear (there are no visible patches or manhole covers).

I wish the front would also send postcards :crying: (Although I imagine riding a tub of lard would be much more dangerous).

I’ve not yet done a superman impression (and hope not to). Sadly I’m offering the complete bike for sale as spares/repair asap, as I move in 2 weeks time to somewhere without a garage :frowning:

Ok, so it looks like I lost the front (suspect oil/diesel/other substance), went down hard but got up again… which is the important part.

Thanks for all your input :slight_smile:

maybe also just check that your calipers and brake system are ok. to go from fully upright and on throttle to suddenly down takes some doing to be honest.