Black ice

General cycling advice ( NOT technical ! )
User avatar
[XAP]Bob
Posts: 16871
Joined: 26 Sep 2008, 4:12pm

Re: Black ice

Postby [XAP]Bob » 4 Jan 2017, 11:19am

Psamathe wrote:Do studded tyres actually help on black ice ? I'd have imagined that the studs would provide extra grip by digging into the surface a bit and that resting on a hard surface they cannot dig into they might even give a lower surface area in contact with the surface. And I'd guess that black ice is hard enough not to allow studs to dig-in.

That said, I've never even seen studded tyres so may be completely mis-understanding how they provide extra grip.

Ian


Tyres provide grip by moulding around the minute imperfections in the road surface.
Tread, and studs, provide grip by causing the soft surface to mould around the tyre/stud.

So they can help - to the extent that you can just sail over some black ice - but if it's sufficiently thin then it will still be slippery, but you'll be breaking it up, so there will be more traction than otherwise (always assuming you don't grab the brakes and lock the wheel in a position where there are no studs)
Last edited by [XAP]Bob on 4 Jan 2017, 11:57am, edited 1 time in total.
A shortcut has to be a challenge, otherwise it would just be the way. No situation is so dire that panic cannot make it worse.
There are two kinds of people in this world: those can extrapolate from incomplete data.

Vorpal
Moderator
Posts: 16817
Joined: 19 Jan 2009, 3:34pm
Location: Not there ;)

Re: Black ice

Postby Vorpal » 4 Jan 2017, 11:36am

Psamathe wrote:Do studded tyres actually help on black ice ? I'd have imagined that the studs would provide extra grip by digging into the surface a bit and that resting on a hard surface they cannot dig into they might even give a lower surface area in contact with the surface. And I'd guess that black ice is hard enough not to allow studs to dig-in.

That said, I've never even seen studded tyres so may be completely mis-understanding how they provide extra grip.

Ian

Studs on black ice are like normal tyres on dry, clean asphalt, maybe even better. No problems with the studs digging in, anymore than on other types of ice.

The first time I commuted on studded tyres, a few miles into my journey, I came to a junction that looked clean & dry. There were some damp looking patches along the edges that made me think it had been gritted. I didn't realise that I was riding on ice, until I stopped at the junction, set a foot down, and immediately fell over because my foot had no traction.
“In some ways, it is easier to be a dissident, for then one is without responsibility.”
― Nelson Mandela, Long Walk to Freedom

User avatar
NATURAL ANKLING
Posts: 10160
Joined: 24 Oct 2012, 10:43pm
Location: English Riviera

Re: Black ice

Postby NATURAL ANKLING » 4 Jan 2017, 12:15pm

Hi,
With all the will and safety in the world you will still fall off, I did on my normal commute three times in three miles one icy morning., over forty years ago.
I was barely moving at the time on each occasion, sore hips feet still in clips, on two wheels its safer when the wheels are moving on flat ground that is, I cycled one steep hill that day and had wheel spin, but deemed it safe enough.

If you are going to slip on ice then a bicycle is always going to be safer for others than any other form of transport, not much chance of injury to others for sure, only your own.
Safest a-b with no one else around at all is a trail / trials motorcycle with block pattern tyres, when you fall you flip onto side and quite often are still sitting on bike when it stops or you just drop off the back and slide on your feet and bum.
The fall is not so high and sudden and the mass of bike cushions the fall.

At no time do you ever use the brakes on ice on motorcycles just the engine and friction from deforming under inflated tyres, which is a trick for extra grip on all motor vehicles of course.

Seen many 4x4's in ditches later in day when I venture out when we have snow :?

I have never seen a studded bicycle tyre but assumed that it will grip like spiked m/cycle tyres other wise whats the point?
http://www.britishpathe.com/video/speedway-on-ice-1
If You Don't Try You Don't Do.....Don't Do You Don't Get...I'm Still Trying....Well Very..
You'll Find Me At The Top Of A Hill...............Somewhere...After Dark..

User avatar
mjr
Posts: 13073
Joined: 20 Jun 2011, 7:06pm
Location: Norfolk or Somerset, mostly
Contact:

Re: Black ice

Postby mjr » 4 Jan 2017, 1:08pm

eileithyia wrote:I never used cycle lanes on icy mornings... and kept out from where the drains are etc........

This is often the official advice from highways authorities who don't grit cycle lanes and tracks (including Norfolk). Cambridge had a go at gritting tracks but gave up a few years ago as far as I know - unlike Norfolk, Cambridgeshire do at least seem to have the gritters set with a wide enough spray to cover on-road cycle lanes, though (and me as I was walking past on the footway :lol: ).

We've an old MTB with Schwalbe Winter studded tyres on all winter here (so no wheel-swapping, although sometimes last-minute bag and spare tube swaps) and it works astonishingly well (yes, even on black ice!), but we've only one for the house, so I'm usually either waiting until it's thawed or taking one of the older wide-tyred bikes out at minimum non-pinching tyre pressures with a slightly lowered saddle. I toy with the idea of kitting out a second bike, but the best would be the folding bike (as when I use it, I'm usually going to appointments so would rather not abandon) and studded tyres seem very expensive in 20".
MJR, mostly pedalling 3-speed roadsters. KL+West Norfolk BUG incl social easy rides http://www.klwnbug.co.uk
All the above is CC-By-SA and no other implied copyright license to Cycle magazine.

AMMoffat
Posts: 204
Joined: 1 Dec 2007, 1:05pm

Re: Black ice

Postby AMMoffat » 4 Jan 2017, 2:08pm

Dave W wrote:"Neither freezing fog or black ice in themselves cause crashes. Drivers failing to drive appropriately for the conditions, or choosing not to drive at all when the conditions are severe, cause crashes - failure to reduce speed being the main issue"


How does 'Not driving at all' cause crashes?
Lost me on that theory.

It's called 'black ice' because it can't be seen, it doesn't tend to reflect light like frost does which makes it difficult to predict. Even if you take precautions and crawl along you are quite likely to come off. Horrible stuff.



Ha ha - so you spotted my badly constructed sentence :oops: though I'm sure you know what I meant, but just to make it clear I've edited my piece to read correctly

Dave W
Posts: 1483
Joined: 18 Jul 2012, 4:17pm

Re: Black ice

Postby Dave W » 4 Jan 2017, 4:16pm

:D I didn't spot the edit, so I read it again today and this time it made sense. I thought I was going mad.

Phileas
Posts: 192
Joined: 18 Feb 2009, 6:12pm
Location: Bristol

Re: Black ice

Postby Phileas » 4 Jan 2017, 6:49pm

In my experience it's sometimes very difficult to predict ice the day before. The roads can be bone dry in the evening but icy the next morning even when there is no rain overnight. On the other hand, sometimes the roads are wet on an evening and the forecast is for the skies to clear and temperature drop but the next morning the roads are dry and ice free.

Also, whether there is likely to be ice when the air temperature is above freezing depends on how windy it is - an air temp of 4C can only lead to ice when the air is still.

As it happens, I fell off on black ice on Monday, on a cycle path. I was aware of the ice risk but was probably lulled into a false sense of security because the corner I was on had no white frosting. Not for the first time, my hip took much of the impact.

MikeF
Posts: 3706
Joined: 11 Nov 2012, 9:24am
Location: On the borders of the four South East Counties

Re: Black ice

Postby MikeF » 4 Jan 2017, 7:54pm

Dave W wrote:"Neither freezing fog or black ice in themselves cause crashes. Drivers failing to drive appropriately for the conditions, or choosing not to drive at all when the conditions are severe, cause crashes - failure to reduce speed being the main issue"
Surprisingly they can. A neighbour of ours parks his car at the top of his drive. It's on a slight slope at the top and then is moderately steep. One day in freezing weather his car slid down the drive and crashed into the house - still with the handbrake on. :wink:
"It takes a genius to spot the obvious" - my old physics master

recumbentpanda
Posts: 211
Joined: 6 Apr 2009, 12:13pm

Re: Black ice

Postby recumbentpanda » 4 Jan 2017, 8:21pm

I also went down on black ice on Monday, also on a cycle path (the Bath-Bristol). Big plus point for low-rider recumbent, no damage to rider! As I was soon after overtaken by numbers of roadies caning it on narrow tyres who appeared to have come to no harm, I began to wonder if my bike with its relatively lightly loaded rear wheel was partly to blame. Shouted warnings to a few oncoming riders all the same. Took the rest of the ride very carefully, constantly paranoid about probably imagined 'squirrelly' feelings. Made a note to self to check out the spot carefully on the way back. As I approached I was horrified to see a small pile of cyclists sitting under blankets by the side of the path, awaiting the arrival of the ambulance man who was wheeling his mobile stretcher carefully along towards them with an escort of cyclists.

Not just me then. Sorry I doubted you, bike!

User avatar
CyberKnight
Posts: 558
Joined: 18 Dec 2009, 4:44pm
Location: Derbyshire

Re: Black ice

Postby CyberKnight » 4 Jan 2017, 9:25pm

recumbentpanda wrote:I also went down on black ice on Monday, also on a cycle path (the Bath-Bristol). Big plus point for low-rider recumbent, no damage to rider! As I was soon after overtaken by numbers of roadies caning it on narrow tyres who appeared to have come to no harm, I began to wonder if my bike with its relatively lightly loaded rear wheel was partly to blame. Shouted warnings to a few oncoming riders all the same. Took the rest of the ride very carefully, constantly paranoid about probably imagined 'squirrelly' feelings. Made a note to self to check out the spot carefully on the way back. As I approached I was horrified to see a small pile of cyclists sitting under blankets by the side of the path, awaiting the arrival of the ambulance man who was wheeling his mobile stretcher carefully along towards them with an escort of cyclists.

Not just me then. Sorry I doubted you, bike!


I came off too on monday on my drop bar MTB on slick tyres too.turned into works side gate off the cycle path and caught the white line thats was covered in frost , wibble wobble and i hit the deck luckily onto a patch of mouldy leaves.

Today i got a flat , found a throrn in the tyre:(
John Wayne: "I won't be wronged, I won't be insulted, and I won't be laid a hand on... I don't do these things to other people, and I require the same from them."

User avatar
horizon
Posts: 9211
Joined: 9 Jan 2007, 11:24am
Location: Cornwall

Re: Black ice

Postby horizon » 20 Jan 2017, 4:18pm

samsbike wrote:
What I am unsure about is when to expect ice. Tonight it's down to around -3c and then staying there or thereabout so tomorrow should be cold. Today it's dry so am I safe to assume that the likelihood of black ice is greatly diminished?



I went for a ride this afternoon in bright, cold, sunny conditions. The road was nice and dry and the forecast was for 6 deg. I reached the point where I know ice can form as water runs across the road from a hillside. And sure enough there it all was: across the road in thin sheets, in puddles by the side of the road and icicles hanging from the bank. This stretch of lane is in shadow for much of the day in winter. I turned back, albeit with some slipping and sliding (I had dismounted). This is southern Cornwall BTW at sea level, not Scotland.

My point is that I don't recall the forecast being below 3 deg overnight but I don't know how to check this (any ideas?). My rule of thumb is that if the forecast or actual temperature falls below 3 deg overnight for your area then the studded tyres are justified in the morning. A lot will depend on local conditions and whether you cycle on main roads but I presume the forecast is for the weather conditions at the local weather station and won't take into account shady or wet spots.

UPDATE:
I've checked the forecast on the Met Office website:
http://www.metoffice.gov.uk/public/weat ... rification
This gave a minimum of 1 deg so quite accurate but still not freezing.
I have two doctors, my left leg and my right leg. (G. M. Trevelyan)
PS I always wondered why the YHA HQ was called Trevelyan House. :)

irc
Posts: 4530
Joined: 3 Dec 2008, 2:22pm
Location: glasgow

Re: Black ice

Postby irc » 20 Jan 2017, 4:51pm

Good studded tyres will allow you to ride uphill on water ice. During the bad winter of 2010 I was cycling around the local river. I could ride up frozen paths that were impossible to walk up.

I had Schwable Ice Spikers. Really draggy tyres but will go through any snow or ice.

User avatar
pedalsheep
Posts: 1004
Joined: 11 Aug 2009, 7:57pm

Re: Black ice

Postby pedalsheep » 20 Jan 2017, 5:24pm

An indoor/outdoor digital thermometer will give you an accurate reading of local temperature. The met office forecast 3 degrees for us (Isle of Wight) but the thermometer said -1.9 when I got up which was born out by the ice in the bird bath and the frost on the roof. Temperatures have been consistently 4-5 degrees lower than forecast for the last week or two.
'Why cycling for joy is not the most popular pastime on earth is still a mystery to me.'
Frank J Urry, Salute to Cycling, 1956.

User avatar
mjr
Posts: 13073
Joined: 20 Jun 2011, 7:06pm
Location: Norfolk or Somerset, mostly
Contact:

Re: Black ice

Postby mjr » 20 Jan 2017, 5:26pm

horizon wrote:My point is that I don't recall the forecast being below 3 deg overnight but I don't know how to check this (any ideas?). My rule of thumb is that if the forecast or actual temperature falls below 3 deg overnight for your area then the studded tyres are justified in the morning. A lot will depend on local conditions and whether you cycle on main roads but I presume the forecast is for the weather conditions at the local weather station and won't take into account shady or wet spots.

Look at "minimum ground temperature" on forecasts like http://www.weatheronline.co.uk/weather/ ... NOREGION=1

Typically, it's at least 4°c below the air temperature given in the main forecasts, plus you can usually deduct another couple of degrees in winter for the countryside outside the given town.
MJR, mostly pedalling 3-speed roadsters. KL+West Norfolk BUG incl social easy rides http://www.klwnbug.co.uk
All the above is CC-By-SA and no other implied copyright license to Cycle magazine.

User avatar
horizon
Posts: 9211
Joined: 9 Jan 2007, 11:24am
Location: Cornwall

Re: Black ice

Postby horizon » 20 Jan 2017, 5:47pm

mjr wrote:
Typically, it's at least 4°c below the air temperature given in the main forecasts, plus you can usually deduct another couple of degrees in winter for the countryside outside the given town.


That's really great - it's what the OP (and we) really needed to know. It also answers pedalsheep's point above that the forecast was too high. I had often noticed severe frosts (ice on car windscreens) with a forecast of say 2 or 3 deg.
I have two doctors, my left leg and my right leg. (G. M. Trevelyan)
PS I always wondered why the YHA HQ was called Trevelyan House. :)