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Author Topic: Gear Changing  (Read 4643 times)

Gear Changing
on: April 08, 2006, 20:20:52 PM
I remember a thread on here a while back about changing gear without using the clutch. Someone said it was better for the car, but I forget the explantion why.

I *think* it was somthing to do with if you dont use the clutch you have to get the timing perfect (more or less) whereas using the clutch you can missjudge it and not know you have which causes strain on the engine.

If someone could explain in as much technical detail as possible, thatd be great !
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  • Offline Chris

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Gear Changing
Reply #1 on: April 08, 2006, 20:38:35 PM
i think we could talk forever about why changing gear without using the clutch on a modern car is bad idea...

But basically everytime you get it wrong, you are tuning your gearbox into a lathe and grinding the teeth off.  thats the main reason.
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Gear Changing
Reply #2 on: April 08, 2006, 20:56:07 PM
The origional thread was about older cars. I realise when you do get it wrong its bad...but when you get it right its actaully better than using the clutch IIRC.
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  • Offline Chris

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Gear Changing
Reply #3 on: April 08, 2006, 21:01:44 PM
Well anything under about 20 years old is a bad idea to do it on IMO - i used to do it regularly on my Mk1 A reg R5, and it was a simple task, but doing it on my 97 R reg nexia is a nightmare!

but yeah, get it right and you save wear on the clutch and gearbox/synchromesh, as everything is moving in "harmony", if you like.

Get it wrong, and you do damage as nothing will fit together :lol:
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Gear Changing
Reply #4 on: April 08, 2006, 21:11:17 PM
Quote from: Chris

but yeah, get it right and you save wear on the clutch and gearbox/synchromesh, as everything is moving in "harmony", if you like.


Can you explain that bit in detail - as technical as possible, please !
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  • Offline Chris

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Gear Changing
Reply #5 on: April 08, 2006, 21:56:20 PM
well Im not all that knowledgebale on synchromeshes tbh...

But as for the clutch - a clutch is simply two plates.  One on the gearbox side, one on the engine side.  Usually to change gear you push the clutch pedal in, to seperate the two plates.  this then allows the synchro and the the rest of the box of tricks to change gear smoothly - i dont know how it does it, it could be magic for all i care as Im never gonna take a gearbox apart.  but doing all that causes wear, as the synchro, the tailshaft, the engine and the two plates of the clutch will be moving at different speeds.  take the foot off the clutch and *BAM* everything wears as it changes to the correct speed.

Leave the clutch in, and if you get the engine speed/road speed etc correct, you can change gear without altering the speeds.

Im sure i will be corrected shortly :lol:
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  • Offline Serious

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Re:Gear Changing
Reply #6 on: April 08, 2006, 23:27:08 PM
A good basic description of how a synchromesh gearbox works. starts off with a mesh gearbox and then describes the synchro mechanisim...

http://auto.howstuffworks.com/transmission3.htm
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  • Offline madmax

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Re:Gear Changing
Reply #7 on: April 08, 2006, 23:29:18 PM
sounds about right to me so far
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  • Offline Pete

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Re:Gear Changing
Reply #8 on: April 08, 2006, 23:35:45 PM
A syncro is designed to take two parts rotating at different speeds and bring them together in such a way that the parts are moving at equal speeds before the dogs engage, so when you change gears youre not forcing two metal parts together, they connect smoothly.

In simple terms the syncros are like conical clutchs that are located on the collar assemblies, which also have baulk rings that prevent the gears engaging until the two sides are rotating at equal speeds.

These things are designed to last thousands and thousands of miles, youd do more damage trying to force gears in than you would using a box correctly, unless you know exactly what youre doing.
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  • Offline Serious

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Re:Gear Changing
Reply #9 on: April 08, 2006, 23:47:26 PM
Which basically means that unless you are a pro, or the next thing to it, its best not to bother if you have a modern gearbox.
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Gear Changing
Reply #10 on: April 08, 2006, 23:51:02 PM
I can do it on an older 10+ y/o gearbox with no hesitation upshifting. Not that it serves any purpose other than playing lotto with your gearbox. Downshifting is much harder. Of course both are much easier on a motorbike. :)

Not recommended for any practical reason, and may cause your car to burst into rainbow colored flames.
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Gear Changing
Reply #11 on: April 09, 2006, 01:27:21 AM
As technical as it needs to be.....

A synchro is there to marry the speed of the gearbox and engine, making every thing run smoothly

Not using the clutch = no synchro = gears at different speeds = stel shavings in your gearbox where the gears used to be!
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