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yambabe
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Joined: 12 Jul 2004
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PostPosted: 20:41 - 04 Feb 2007    Post subject: Bottoms down...... Reply with quote
New phenomenon noticed today. Each time I went to set off from a standstill I felt the back end of the bike drop a bit.

What's that all about then?
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Shaun
Likes 'em bent



Joined: 17 May 2003
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PostPosted: 20:48 - 04 Feb 2007    Post subject: Reply with quote
The weight being transferred to the rear as you accelerate, obvious init. Razz
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CoronaBoner
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Joined: 04 Jul 2005
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PostPosted: 20:48 - 04 Feb 2007    Post subject: Reply with quote
It means your getting quicker at pulling away, maybe your confidence is rising with this good weather we have been having.

Soon you will pulling away on the back wheel Cool
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yambabe
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Joined: 12 Jul 2004
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PostPosted: 20:57 - 04 Feb 2007    Post subject: Reply with quote
Shaun wrote:
The weight being transferred to the rear as you accelerate, obvious init. Razz


Never noticed it on the Eliminator though. John says it's because that was a shaftie and the Zephyr is chain driven, but he won't tell me WHY that makes a difference!

I reckon maybe it could just be that the suspension on the Eliminator was shit?
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Itchy
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Joined: 07 Apr 2005
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PostPosted: 21:03 - 04 Feb 2007    Post subject: Reply with quote
Chain snatch? , not ridden any of your bikes , but GS500Es had it pretty bad, infact many bikes I've ridden seems to have it , too used to bigger bikes which don't give a damn about min revs before letting the cluch out,

me NTV has such a badly adjusted clutch and idle speed you can set off purely on the clutch !
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stinkwheel
Bovine Proctologist



Joined: 12 Jul 2004
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PostPosted: 21:23 - 04 Feb 2007    Post subject: Reply with quote
You know Newtons law "Every action has an equal and opposite reaction"?

Look at the shaft, it rotates round the long axis of the bike. As such, it is trying to flip the bike round sideways. It can't do this because it is firmly bolted down in that direction so it lifts the wheel instead (you would feel this as the wheel 'chattering' but it's only noticeable if you give it some serious welly) .

The chain rotates round the short axis of the bike. It is trying to rotate the rest of the bike backwards round the back wheel. As a result, the bike tends to squat down under acceleration.
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G
The Voice of Reason



Joined: 02 Feb 2002
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PostPosted: 21:25 - 04 Feb 2007    Post subject: Reply with quote
Try letting the clutch out a little with the brake on (just slipping a bit) - you'll find it does the same thing.
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yambabe
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Joined: 12 Jul 2004
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PostPosted: 21:28 - 04 Feb 2007    Post subject: Reply with quote
stinkwheel wrote:

Look at the shaft, it rotates round the long axis of the bike. As such, it is trying to flip the bike round sideways. It can't do this because it is firmly bolted down in that direction so it lifts the wheel instead (you would feel this as the wheel 'chattering' but it's only noticeable if you give it some serious welly) .



Ah now that actually does make some sort of sense. Is that what's happening when I feel the back wheel "hop" as I put the power back on to come out of corners and roundabouts on the shaftie then?
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Finglonga
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Joined: 27 Jul 2004
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PostPosted: 21:44 - 04 Feb 2007    Post subject: Reply with quote
On the 1150GS when you accelerate the bike does the opposite of what your expecting, instead of squatting down it lifts up. Shocked Took a while to get used too. Wink
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G
The Voice of Reason



Joined: 02 Feb 2002
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PostPosted: 21:47 - 04 Feb 2007    Post subject: Reply with quote
Different suspension geometry can change 'anti squat' properties.
People that are much better on track can 'tune' this to help the bike handling - so that the rear gets best grip by pushing out just the right amount coming out of a corner on the power.
I believe technically a bike should actually lift at the rear when accelerating if it weren't for the general anti-squat properties of the suspension and transmission.
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stinkwheel
Bovine Proctologist



Joined: 12 Jul 2004
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PostPosted: 21:49 - 04 Feb 2007    Post subject: Reply with quote
babyyam wrote:

Ah now that actually does make some sort of sense. Is that what's happening when I feel the back wheel "hop" as I put the power back on to come out of corners and roundabouts on the shaftie then?


Exactly. This is why the whole 'Can't wheelie/countersteer a shaftie' debate on bikersweb originated (as well as certain wind-up merchants who didn't have enough work to do).

As Fingalonga pointed out, the exception to this rule is the BMW. They have a single sided swingarm with the shaft running inside it and some clever monkey business with angles on the rear suspension that stops shaft drive torque reaction.
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The last post was made 18 years, 357 days ago. Instead of replying here, would creating a new thread be more useful?
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