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Car + snow stupid question Watch

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    (Original post by Nuffles)
    As much as this is true, the Highway code states that you should put it in reverse when pointing downhill and in first when pointing uphill. What you say is very true (although reverse in my car is about the same ratio as first, if not lower) but either can be accepted as good practice. I think we can all agree that not leaving it in gear at all is foolish :rolleyes:
    I was speaking entirely from a technical perspective and not from a Highway Code perspective. On most cars, afaik, reverse is equal to about 2nd gear. I presume the mention in the highway code of selecting the 'opposite' gear to the way you are facing goes back to primitive ignition systems, and is intended to eliminate the risk of an unarrested rollaway bump starting the engine?

    Personally, in real life I'd rather select the gear which I know has the lowest ratio (and therefore has the lowest risk of a rollaway) than follow the letter of the Highway Code
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    (Original post by gbduo)
    I have winter tyres on my car. Best £300 I ever spent.

    They are amazing, a revelation not just in the snow, but they work better below 7C in wet, dry, ice, snow, perfect for our winters. I have not tried them in the snow yet as scared of inexperienced people on summer tyres ploughing into me as I stop 10x quicker than they do...

    I think winter tyres should be law, especially in the North.
    I run michelin Alpins in the winter and Advans in the summer

    I generally despair at the level of driving ability people around here seem to show when it's snowing. Then again I grew up in the shetland islands and routinely drive 300 miles a week in the winter in heavy snow and ice in my trusty peugeot 206 :p: and I have a racing license, so I generally despair at people's skid control abilities anyway.
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    (Original post by gbduo)
    I have winter tyres on my car. Best £300 I ever spent.

    They are amazing, a revelation not just in the snow, but they work better below 7C in wet, dry, ice, snow, perfect for our winters. I have not tried them in the snow yet as scared of inexperienced people on summer tyres ploughing into me as I stop 10x quicker than they do...

    I think winter tyres should be law, especially in the North.
    Saw this video the other day, am definately going to look into getting a set now:



    The performance on snow and ice is obviously a factor, however the main thing that too many people fail to realise is that below about 7C the rubber on normal tyres becomes too firm to be effective and this can have a dramatic impact on stopping distances (even in conditions that some people might think would be completely safe - e.g cold but bone dry day)
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    (Original post by TheFatController)
    Saw this video the other day, am definately going to look into getting a set now:



    The performance on snow and ice is obviously a factor, however the main thing that too many people fail to realise is that below about 7C the rubber on normal tyres becomes too firm to be effective and this can have a dramatic impact on stopping distances (even in conditions that some people might think would be completely safe - e.g cold but bone dry day)
    Good luck! There is a UK wide shortage at the moment, not getting any more stock till January, but you can ring around.

    I have Kumho I-Zen KW27 (205/55/R16) and Kumho I-Zen KW17 (225/50/R16) on my car and have just been out in the snow. Put it this way, I overtook a 4x4 on summer tyres which was struggling up a snow when I was in a high performance RWD sports car.

    They make the world of difference in the snow and ice. But as you say, the water clearing ability is incredible, when it is cold and wet they just grip and in low temperatures they are equally as good.

    Anything around 4C and you start to really see and feel the difference.

    They are so worth the money. I have two set of rims though, so one set has summer tyres and the other has my winter tyres on.

    I used Event Tyres to fit my wheels, excellent service.

    Graham
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    (Original post by gbduo)
    Good luck! There is a UK wide shortage at the moment, not getting any more stock till January, but you can ring around.

    I have Kumho X-Zen KW27 (205/55/R16) and Kumho X-Zen KW17 (225/50/R16) on my car and have just been out in the snow. Put it this way, I overtook a 4x4 on summer tyres which was struggling up a snow when I was in a high performance RWD sports car.

    They make the world of difference in the snow and ice. But as you say, the water clearing ability is incredible, when it is cold and wet they just grip and in low temperatures they are equally as good.

    Anything around 4C and you start to really see and feel the difference.

    They are so worth the money. I have two set of rims though, so one set has summer tyres and the other has my winter tyres on.

    I used Event Tyres to fit my wheels, excellent service.

    Graham
    Yeah, I'm only using my car for practise atm anyway (still on L plates) so waiting until January isn't really an issue.

    The one problem with winter tyres than I can see is that if they lasted until summertime, and there was a heatwave, people would be driving around with less effective tyres (much like you would be with summer tyres in winter). I have heard suggestions that people should get a spare set of cheap wheels just to put winter tyres on - this sounds like it may be the best solution.
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    (Original post by TheFatController)
    Yeah, I'm only using my car for practise atm anyway (still on L plates) so waiting until January isn't really an issue.

    The one problem with winter tyres than I can see is that if they lasted until summertime, and there was a heatwave, people would be driving around with less effective tyres (much like you would be with summer tyres in winter). I have heard suggestions that people should get a spare set of cheap wheels just to put winter tyres on - this sounds like it may be the best solution.
    A lot of tyre fitters will fit your summer tyres they take off for free when it comes to spring.

    But yeh, two sets of rims is the easiest solution.
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    (Original post by TheFatController)
    I was speaking entirely from a technical perspective and not from a Highway Code perspective. On most cars, afaik, reverse is equal to about 2nd gear. I presume the mention in the highway code of selecting the 'opposite' gear to the way you are facing goes back to primitive ignition systems, and is intended to eliminate the risk of an unarrested rollaway bump starting the engine?

    Personally, in real life I'd rather select the gear which I know has the lowest ratio (and therefore has the lowest risk of a rollaway) than follow the letter of the Highway Code
    I can't see why reverse would be the same ratio as second, otherwise it would be much harder to pull away in and leave you with a higher top speed when what you want is a low ratio to minimise the risk of stalling and to give more precision at lower speeds. All the cars I've driven (probably around 10 or 12) have had a reverse gear with a similar ratio to that of first. You'd have to have a very primitive ignition system for an engine to bump start itself with no ignition. You still need ignition to send power the fuel pump and the coil and this system was common place when the highway code was written in the 60s and 70s.
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    (Original post by Nuffles)
    You'd have to have a very primitive ignition system for an engine to bump start itself with no ignition. You still need ignition to send power the fuel pump and the coil and this system was common place when the highway code was written in the 60s and 70s.
    Well the reason I suggested this is that I can only assume that this is the reason why the highway code has the thing about using the opposite gear direction to the direction you are going to roll away in - I can't think of any other reason why it would be beneficial to select reverse when pointing downhill instead of first.
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    (Original post by TheFatController)
    Well the reason I suggested this is that I can only assume that this is the reason why the highway code has the thing about using the opposite gear direction to the direction you are going to roll away in - I can't think of any other reason why it would be beneficial to select reverse when pointing downhill instead of first.
    Well I always put it the car in the opposite gear as to how the car was facing because I always thought that if the handbrake did fail the car would stop straight away as their would be transmission lock. In a downhill facing gear the engine could turn over theoretically.

    I guess when engines back in the 60s had MUCH less compression that they do now, this was entirely possible.
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    (Original post by gbduo)
    Well I always put it the car in the opposite gear as to how the car was facing because I always thought that if the handbrake did fail the car would stop straight away as their would be transmission lock. In a downhill facing gear the engine could turn over theoretically.

    I guess when engines back in the 60s had MUCH less compression that they do now, this was entirely possible.
    That's the point though, I don't think it would lock up the transmission any more than using a gear that runs the same way that the car is facing - in order to do that you'd need a ****** brake or an auto box with an actual physically transmission lock.
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    (Original post by TheFatController)
    That's the point though, I don't think it would lock up the transmission any more than using a gear that runs the same way that the car is facing - in order to do that you'd need a ****** brake or an auto box with an actual physically transmission lock.
    Well theoretically/logically it must do. The transmission is opposing the motion the car wants to go in.

    You slam the gearbox into reverse at 30 mph and come back to me with the result! Then try and say it is not a lock!

    I am not saying that is the reason the highway code does it, but it is the only thing that makes sense to me. Especially as I say, cars back in the 60s had much lower compression ratios than they do now. Around 6:1 for petrol. Most petrols are up over 10:1 now. Obviously that is logarithmic as well in terms of pressure increase so quite a jump in peak pressures that the car would have to overcome to roll down the hill.
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    As far as I'm aware convention is the only thing determining the direction of rotation of an engine - obviously valves etc. will affect the ability of it to run, but in terms of turning over and effectively acting as a compressor there's no particular reason for it to turn in the direction it will when you start it, so whether it's a forward or reverse gear shouldn't make any difference (though obviously ratio will). In fact I think a lot of large marine diesels can run in either direction to avoid the need for a gearbox - I'm sure Graham can confirm if that's the case!
    Also I have once had my car roll through TDC. Admittedly it was on a steep hill and very slow, but it did manage to turn over.
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    Turn your wheels towards the kerb is possible
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    (Original post by gbduo)
    Well theoretically/logically it must do. The transmission is opposing the motion the car wants to go in.

    You slam the gearbox into reverse at 30 mph and come back to me with the result! Then try and say it is not a lock!

    I am not saying that is the reason the highway code does it, but it is the only thing that makes sense to me. Especially as I say, cars back in the 60s had much lower compression ratios than they do now. Around 6:1 for petrol. Most petrols are up over 10:1 now. Obviously that is logarithmic as well in terms of pressure increase so quite a jump in peak pressures that the car would have to overcome to roll down the hill.
    You just wouldn't be able to engage reverse gear at 30mph. That's not beacuse of a lock, that's beacuse the gear the operates reverse is spinning in the other direction at speed to the other gears, and therefore the teeth cannot engage. You'll get a horrible noise and I imagine you would do damage to the teeth as well.

    If you park facing downhill in reverse, it's not a transmission lock that holds you back, but the compression of the engine. If you were to stop the engine and kill the ignition, put the car into reverse and up on a ramp and then exert enough energy on the wheels (I use this analogy because I cannot think of a hill steep enough to allow a car to roll away in either first or reverse) in a forward direction, you would be able to turn the engine over backwards (although obviously not start it). As CurlyBen says, an engine can turn over backwards all day if you use external force, it just won't be able to run under its own steam backwards.

    The only transmissions that have 'locks' per se are auto boxes with Park (where a physical lug locks the tranmission in place - this is why you shouldn't leave an auto in park at traffic lights!), or vehicles such as Land Rovers which have transmission handbrakes.
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    (Original post by CurlyBen)
    As far as I'm aware convention is the only thing determining the direction of rotation of an engine - obviously valves etc. will affect the ability of it to run, but in terms of turning over and effectively acting as a compressor there's no particular reason for it to turn in the direction it will when you start it, so whether it's a forward or reverse gear shouldn't make any difference (though obviously ratio will). In fact I think a lot of large marine diesels can run in either direction to avoid the need for a gearbox - I'm sure Graham can confirm if that's the case!
    Also I have once had my car roll through TDC. Admittedly it was on a steep hill and very slow, but it did manage to turn over.
    They can, but they are specially designed to do so with reversible camshafts. The engines do not produce as much power in reverse and can only rev to 1/3 power. So yeh, they can run in reverse largely because they are 2 stroke but they don't like it very much. Plus you have to stop the engine from going forward, start it spinning the other way, inject the fuel at the right time, it is incredibly complicated bit of engineering!
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    (Original post by TheFatController)
    You just wouldn't be able to engage reverse gear at 30mph. That's not beacuse of a lock, that's beacuse the gear the operates reverse is spinning in the other direction at speed to the other gears, and therefore the teeth cannot engage. You'll get a horrible noise and I imagine you would do damage to the teeth as well.

    If you park facing downhill in reverse, it's not a transmission lock that holds you back, but the compression of the engine. If you were to stop the engine and kill the ignition, put the car into reverse and up on a ramp and then exert enough energy on the wheels (I use this analogy because I cannot think of a hill steep enough to allow a car to roll away in either first or reverse) in a forward direction, you would be able to turn the engine over backwards (although obviously not start it). As CurlyBen says, an engine can turn over backwards all day if you use external force, it just won't be able to run under its own steam backwards.

    The only transmissions that have 'locks' per se are auto boxes with Park (where a physical lug locks the tranmission in place - this is why you shouldn't leave an auto in park at traffic lights!), or vehicles such as Land Rovers which have transmission handbrakes.
    Ooo yeh true. Bugger. I blame the snow for my stupidity!
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    (Original post by Juno)
    Well, at least I can read
    I can read thanks

    O and at least I know how a car works before dishing out advice. Now go do some cleaning :rolleyes:
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    snow driving really isnt that hard. there are too many retards in this country who seemingly mess up in the snow and just dont learn. youd think after several attempts at getting up a hill, people would realise that 7000 rpm doesnt work, but no they just carry on!

    oh and the snow can provide some great fun to play in with a car too!!
    http://www.youtube.com/watch?v=yPZubvi-8vI
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    Just after i learned to drive it snowed and i spent a whole night drifting around an empty car park. Some would say its antisocial behaviour, and the police would have probably cautioned me if i'd been caught. But once I skidded while on a roundabout and I managed to control it and avoid an accident. In Scandinavian countries you have to learn to control skids and do extreme driving as part of the test, its a good skill to have.
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    (Original post by Nuffles)
    As much as this is true, the Highway code states that you should put it in reverse when pointing downhill and in first when pointing uphill.
    Just because the highway code states something different doesn't mean the truth isn't valid. If the highway code's vague explanations that causes all of these bad drivers.
 
 
 
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