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Stability light bike v heavy bike. #739505
06/22/18 9:02 pm
06/22/18 9:02 pm
Joined: Jun 2015
Posts: 84
Cheshire UK.
N
Nickjaxe Offline OP
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Nickjaxe  Offline OP
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Joined: Jun 2015
Posts: 84
Cheshire UK.
Hi guys the only bike I have ever owned is the lightweight BSA 175 Bantam I have now...been riding it 2 years now.

May be down to me but I find I wobble a bit riding in slow moving traffic.

I often wonder...if I rode say a heavy 650 would the bike be more stable.

I weigh 95 kg.

Nick.


Recently bought my 1st ever motorcycle...a humble 1969 BSA Bantam B175...I am enjoying using my Bantam so much...does all I need.
My car that I use daily is an old series Landrover that I bought new 40 years ago and has just become tax free.
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Re: Stability light bike v heavy bike. [Re: Nickjaxe] #739509
06/22/18 9:18 pm
06/22/18 9:18 pm
Joined: Aug 2015
Posts: 1,240
Bolton Lancs UK
A
Andy Higham Offline
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Andy Higham  Offline
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A
Joined: Aug 2015
Posts: 1,240
Bolton Lancs UK
A light bike will be more susceptible to external influences like wind, road imperfections etc
On the other hand a lighter bike responds better to rider input

If the bike is weaving/wobbling at low speed it is a sure sign that the head races need attention


BSA B31 500cc "Stargazer"
Greeves 200cc "Blue Meanie"
Greeves 350
Greeves 360 Challenger
Suzuki GSX1100 EFE "Sorcerers Apprentice"
GM500cc sprint/LSR bike "Deofol"
Jawa 500cc "Llareggub"
2003 Aprilia RSV Mille "Lo Stregone"
'35 OK Supreme
'36 OK Supreme
Re: Stability light bike v heavy bike. [Re: Nickjaxe] #739602
06/23/18 8:23 pm
06/23/18 8:23 pm
Joined: Oct 2006
Posts: 2,803
Elburn, Ill. USA
I
Irish Swede Offline
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Irish Swede  Offline
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Posts: 2,803
Elburn, Ill. USA
Where is the crankcase and flywheel in relation to the center-line of both axles?

If the crankcase and flywheels are BELOW that line, the bike tends to be more stable.
That's why, as heavy as they are, the old rigid-frame heavyweight Harleys and Indians were so stable that
small women could handle them (especially the 80-inch flat-heads.)

This is also why bikes like the early Moto-Guzzis, the Harley Aermacchis and Douglas twins handled well: because the cylinders and crankcases were in a fore-and-aft configuration, and thus the weight was kept LOW in the frame.

The Sportster Harleys suffered handling problems because to get more ground clearance the engine was mounted higher. This raised the center of gravity, causing the problem.

Re: Stability light bike v heavy bike. [Re: Nickjaxe] #739603
06/23/18 8:25 pm
06/23/18 8:25 pm
Joined: Jun 2015
Posts: 84
Cheshire UK.
N
Nickjaxe Offline OP
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Nickjaxe  Offline OP
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Joined: Jun 2015
Posts: 84
Cheshire UK.
Hi I.S. I will look into that tomorrow...cant quite visualise it at the moment...thanks.


Recently bought my 1st ever motorcycle...a humble 1969 BSA Bantam B175...I am enjoying using my Bantam so much...does all I need.
My car that I use daily is an old series Landrover that I bought new 40 years ago and has just become tax free.
Re: Stability light bike v heavy bike. [Re: Nickjaxe] #739608
06/23/18 9:05 pm
06/23/18 9:05 pm
Joined: Aug 2005
Posts: 1,487
melbourne florida
B
bodine031 Offline
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bodine031  Offline
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melbourne florida
Tighten/service the neck bearings and air up the tyres

Re: Stability light bike v heavy bike. [Re: Nickjaxe] #739713
06/24/18 6:37 pm
06/24/18 6:37 pm
Joined: Jan 2004
Posts: 3,812
ca, us
D
DMadigan Offline
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DMadigan  Offline
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Joined: Jan 2004
Posts: 3,812
ca, us
Relative axle and crankcase height are not directly related to stability. If the CG were below the tyre contact patch the bike would be statically stable and sit upright at a stop with no input. A motorcycle is statically unstable and dynamically stable if the castor and trail parameters are correct. Very large castor and trail dimensions (such as on "choppers") are very stable and require a lot of effort to turn.
Bikes with small castor and trail (such as a trials bike) turn very easily but also tend to be unstable or "twichy" at high speed.
Larger bikes have heavier wheels and forks which make them less susceptible to outside forces by rider or road, a combination of higher gyroscopic forces and rotational inertia about the steering axis. The frequency response (how quickly it reacts to a force) is lower. Adding a steering damper will do the same. Friction dampers, like used on British bikes, have a high initial resistance to movement compared to fluid dampers which increase force with velocity (rate of turning the steering).
Loose or over tight headstock bearings will affect the steering. Loose will make the stem move around, changing the direction of forces put into the frame. Tight makes the steering "notchy", especially if the cups have dents which can happen after a lot of use on bumpy roads with straight roads.
How is your bicycle riding at slow speeds, the same or stable?

Re: Stability light bike v heavy bike. [Re: Nickjaxe] #739716
06/24/18 6:49 pm
06/24/18 6:49 pm
Joined: Jun 2015
Posts: 84
Cheshire UK.
N
Nickjaxe Offline OP
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Nickjaxe  Offline OP
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Joined: Jun 2015
Posts: 84
Cheshire UK.
Interesting DM...you ask how is my bicycle...is that pedel cycle....while since I have rode it but from memory I was quite steady at low speed on it.


Recently bought my 1st ever motorcycle...a humble 1969 BSA Bantam B175...I am enjoying using my Bantam so much...does all I need.
My car that I use daily is an old series Landrover that I bought new 40 years ago and has just become tax free.
Re: Stability light bike v heavy bike. [Re: Nickjaxe] #740058
06/27/18 6:27 pm
06/27/18 6:27 pm
Joined: Feb 2006
Posts: 688
Qld, Aust and Otago,NZ
G
Ginge Offline
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Ginge  Offline
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Joined: Feb 2006
Posts: 688
Qld, Aust and Otago,NZ
You can stabilise the bike when riding slow.

Add a little rear brake.

Blip the throttle to use the gyroscopic effect of the flywheel.

Keep your head up and look down the road further.


Ginge
Re: Stability light bike v heavy bike. [Re: Ginge] #740079
06/27/18 9:09 pm
06/27/18 9:09 pm
Joined: Jun 2015
Posts: 84
Cheshire UK.
N
Nickjaxe Offline OP
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Nickjaxe  Offline OP
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Joined: Jun 2015
Posts: 84
Cheshire UK.
Interesting Ginge...will experiment.


Recently bought my 1st ever motorcycle...a humble 1969 BSA Bantam B175...I am enjoying using my Bantam so much...does all I need.
My car that I use daily is an old series Landrover that I bought new 40 years ago and has just become tax free.
Re: Stability light bike v heavy bike. [Re: Ginge] #740223
06/29/18 11:46 am
06/29/18 11:46 am
Joined: May 2013
Posts: 4,946
Rotherham - S. Yorkshire
Allan Gill Offline

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Allan Gill  Offline

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Joined: May 2013
Posts: 4,946
Rotherham - S. Yorkshire
Originally Posted by Ginge
You can stabilise the bike when riding slow.

Add a little rear brake.



Exactly how I was taught. Keep the engine working...


beerchug
Re: Stability light bike v heavy bike. [Re: Nickjaxe] #740604
07/03/18 12:00 pm
07/03/18 12:00 pm
Joined: Jun 2015
Posts: 84
Cheshire UK.
N
Nickjaxe Offline OP
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Nickjaxe  Offline OP
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Joined: Jun 2015
Posts: 84
Cheshire UK.
I do remember this technique from my bike training days a few years ago...supprising how quickly one can forget.


Recently bought my 1st ever motorcycle...a humble 1969 BSA Bantam B175...I am enjoying using my Bantam so much...does all I need.
My car that I use daily is an old series Landrover that I bought new 40 years ago and has just become tax free.
Re: Stability light bike v heavy bike. [Re: Nickjaxe] #741092
07/07/18 11:03 pm
07/07/18 11:03 pm
Joined: Feb 2006
Posts: 688
Qld, Aust and Otago,NZ
G
Ginge Offline
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Ginge  Offline
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Joined: Feb 2006
Posts: 688
Qld, Aust and Otago,NZ
Yeah, you've got to try and maintain good riding habits I reckon. The best tip I was given was to look where you want to go, not where you are going. If you go into a corner a bit hot just lift the head and look through the corner and the bike will work with the body to self correct.

I also practice weighting the pegs differently on uneven surfaces or gravel. You can stand on the pegs which shifts Centre of Gravity down, but you can also remain seated and just press down with your legs and that is enough to shift the weight down a bit.

There is a guy called Coach Ramey that is occasionally interviewed on a podcast called Adventure Rider Radio. He has a great way of explaining how to use your body and bike together. Well worth a listen.

Sometimes when I ride for the hell of it I consciously spend some time practicing this stuff. It gives the ride some purpose apart from just riding there and back.

Bantam or Bonneville. They're all bikes.


Ginge
Re: Stability light bike v heavy bike. [Re: Nickjaxe] #741095
07/07/18 11:25 pm
07/07/18 11:25 pm
Joined: Aug 2015
Posts: 1,240
Bolton Lancs UK
A
Andy Higham Offline
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Andy Higham  Offline
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A
Joined: Aug 2015
Posts: 1,240
Bolton Lancs UK
The best advice I can give is to adjust your stance on the bike so you are relaxed, your arms are bent and your weight is distributed between your arse and feet. If the bars shake don't fight, let them.
Maybe you could find a deserted patch of tarmac and practice riding slowly in a straight line and riding in ever decreacing circles.
Its all about gaining confidence in he bike


BSA B31 500cc "Stargazer"
Greeves 200cc "Blue Meanie"
Greeves 350
Greeves 360 Challenger
Suzuki GSX1100 EFE "Sorcerers Apprentice"
GM500cc sprint/LSR bike "Deofol"
Jawa 500cc "Llareggub"
2003 Aprilia RSV Mille "Lo Stregone"
'35 OK Supreme
'36 OK Supreme

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