Front and Rear Weight Bias

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Blobber
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Front and Rear Weight Bias

#1 Post by Blobber » Thu May 28, 2015 10:44 am

I've just put my RZV500 through an MOT test and was advised that unusually for a bike like this there was a weight bias to the rear. The way of changing this I guess is to either jack the rear height up or lower the front, to shift the weight bias more to the front.

The bike has FZR1000 Genesis forks/front wheel 17" and a Nitron adjustable length shock with a YZF600 Thundercat rear wheel 17".

Ive already got the shock at max length and the fork tubes coming through the top of the yokes by approx 10mm.

What I'm not sure of is what is wrong with the bike. Is it the front too high or back too low. Unfortunately I didnt take any reference measurements prior to modification. Anyone have any useful dimensions so I can check where the issue is.
Thanks
Trevor
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Bikes:
RZV500R FZR1000 forks wheels JL pipes
RD350LC N2

begbie
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Re: Front and Rear Weight Bias

#2 Post by begbie » Thu May 28, 2015 11:34 am

When you say Issue, Is that just that its not 50/50 or do you have a handling problem.
If its a few percent between the front rear weight bias, forget about it, It will make no difference what so ever getting it spot on. As soon as theres a rider on board, it changes, You move around, Its dynamic.
Last edited by begbie on Thu May 28, 2015 2:42 pm, edited 1 time in total.

Blobber
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Re: Front and Rear Weight Bias

#3 Post by Blobber » Thu May 28, 2015 11:40 am

The weight bias was checked with the MOT tester sat on the bike in a riding position and the back was I think 5 kg heavier than the front. He expected it to be the other way round.
The handling is really good but just thought it could be improved based on what the guy said.
For piece of mind I'd like to just check a few reference dimensions if someone has any.......
Bikes:
RZV500R FZR1000 forks wheels JL pipes
RD350LC N2

rd84
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Re: Front and Rear Weight Bias

#4 Post by rd84 » Thu May 28, 2015 3:25 pm

Hi

My bike is 45% front 55% rear unloaded - the bike is a standard 47X

Cheers
Paul

Blobber
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Re: Front and Rear Weight Bias

#5 Post by Blobber » Fri May 29, 2015 4:24 am

So it sounds like the weight bias on my bike is similar to standard.
Does anyone have reference dimensions say from the floor to the front and rear indicators?
Cheers
Bikes:
RZV500R FZR1000 forks wheels JL pipes
RD350LC N2

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solo 2
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Re: Front and Rear Weight Bias

#6 Post by solo 2 » Fri May 29, 2015 9:38 am

5Kg is less than 2% of the weight of the bike with rider, so it's not out by much. Was the bike topped up on fluids, this will make a difference, especially fuel. Was the tester sitting bolt upright, or properly sat like you were giving er' bullets. If it really concerns you jack the back end up a bit, puts more front bias and it will turn faster, but at the expense of some stability.

Blobber
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Re: Front and Rear Weight Bias

#7 Post by Blobber » Fri May 29, 2015 12:22 pm

The guy was sitting like he was riding and holding the handlebars. Fuel tank and oil tank were pretty full. I think what he was saying was that modern bikes have the weight slightly biased to the front and with my upgrades the handling may be improved by doing the same. Unfortunately I am out of rear adjustment as Nitron shock is as long as it will wind out. That was a bit disappointing really as I thought a decent range of adjustment would be possible with this unit.

My only option to play with it is to lower the front by having the forks sticking out the yokes.
Bikes:
RZV500R FZR1000 forks wheels JL pipes
RD350LC N2

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Rick Lance
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Re: Front and Rear Weight Bias

#8 Post by Rick Lance » Fri May 29, 2015 12:42 pm

Add two links to you chain length and bring the wheel farther back in the axle slot. Moving the rear wheel farther away from the center of gravity will transfer more weight to the front end and improve handling. Be aware that this will also affect the leverage on the rear shock spring and make the suspension softer somewhat and could require a stiffer spring, depending on where you are now, spring rate wise.
There's nothing wrong with lowering the front end when using modern rims and rubber. Stock geometry is no longer advisable and you will notice an improvement with turn in with no downside in stability.
If I disagree with everyone, that doesn't make me right. If I take the side of only one, it doesn't end the fight. If my position's strong enough from exposure to the light, you may see things my way when we share the same highway.

Blobber
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Re: Front and Rear Weight Bias

#9 Post by Blobber » Fri May 29, 2015 12:49 pm

Thanks Rick, I will try lowing the front by maybe 10mm and see what that feels like.
Bikes:
RZV500R FZR1000 forks wheels JL pipes
RD350LC N2

Jeppe500
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Re: Front and Rear Weight Bias

#10 Post by Jeppe500 » Mon Jun 01, 2015 2:38 am

[quote="Blobber"]Thanks Rick, I will try lowing the front by maybe 10mm and see what that feels like.[

Hi Blobber
I've lower the frontend on my bike, and of course raised the rear.
The yokes are stickning up quite a bit now.
Handling with 17"-rims is really good with no issues.
[URL=http://s1120.photobucket.com/user/ ... .jpg[/img][/url]
//Jeppe

Blobber
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Re: Front and Rear Weight Bias

#11 Post by Blobber » Mon Jun 01, 2015 4:58 am

Hi Jeppe - very nice bike, out of interest could you measure the distance from the floor to the bottom of the front and rear indicators.
Much appreciated.

Cheers
Trevor
Bikes:
RZV500R FZR1000 forks wheels JL pipes
RD350LC N2

Jeppe500
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Re: Front and Rear Weight Bias

#12 Post by Jeppe500 » Mon Jun 01, 2015 12:16 pm

Blobber wrote:Hi Jeppe - very nice bike, out of interest could you measure the distance from the floor to the bottom of the front and rear indicators.
Much appreciated.

Cheers
Trevor
Thank's !
For your info the front and rearend are from a Yamaha YZF750.
When I did the 17-rims conversion I raised the rear for compensate for the smaller wheel by move the front mountingholes for the reardamper. Have been lower the frontend bit by bit.
As is now I can't go any lower.

Did go pass the bike and took same measures.
Distance from floor to center of centerpin of the indicators are approx - front 69 cm and rear 74,5cm.

Never had checked what my bikes weight front to rear.

Hope it helps // Jeppe
Last edited by Jeppe500 on Mon Jun 01, 2015 12:25 pm, edited 1 time in total.

Blobber
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Re: Front and Rear Weight Bias

#13 Post by Blobber » Mon Jun 01, 2015 12:24 pm

Thanks Jeppe will check yours against mine as a reference and see how they compare
Trevor
Bikes:
RZV500R FZR1000 forks wheels JL pipes
RD350LC N2

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