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suspension front springs

 
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alcatrazhack



Joined: 09 Jun 2005
Posts: 19
Location: Oakland, CA

PostPosted: Tue Mar 10, 2009 10:10 am    Post subject: suspension front springs Reply with quote

Hello, I haven't been on the forum for a long time, and now I finally got to work on the bike again. My hack is a ninja 500r+velorex. Mine is the third hack of such combination made by Doug Bingham.




I am thinking of springs on the front right now. I wonder what is the difference between progressive vs. straight rate. I know the meaning of both, of course; but I want to know on a hack, which one will make more sense. This is especially true that, one has to take into account that there may or may not be a passenger, and also, if we use straight rate (say, race-tech), I am not sure how we can "convert" the rider weight on a side hack to a rider weight of a solo, which is how the straight rate springs are designed for anyway.

Right now I see that .95kg/mm is the hardest you can get for a race-tech.
I wonder how it works. If it were a solo and just me, I would pick a .90kg/mm.

If I choose progressive, I wonder if it will be to soft at initially.

Of course in an ideal world, if they can develop a straight rate spring that can be adjusted at anytime by a rider, or a computer, that would be perfect. Alas, such technology is still in the fantasy land.

I also wonder about the back springs, but I probably will not get into it until I have enough money to buy a Penske double click shock first.


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Paul



Joined: 27 Jan 2005
Posts: 182
Location: Utah

PostPosted: Tue Mar 10, 2009 2:58 pm    Post subject: Re: suspension front springs Reply with quote

alcatrazhack wrote:
Right now I see that .95kg/mm is the hardest you can get for a race-tech.
I wonder how it works. If it were a solo and just me, I would pick a .90kg/mm.


Why not measure the weight on each wheel? Get three scales (a bathroom scale will probably do) and put one under each wheel. Measure with just you on the rig; then measure with a passenger in the chair. That will give you two numbers for your front wheel load - base the spring rate on those numbers.

But - if you'd use .90 for a solo, then I bet .95 will not be enough.

Progressive springs are a good idea - but they aren't very tuneable. Straight rate ones are much easier to work with.


Quote:
Of course in an ideal world, if they can develop a straight rate spring that can be adjusted at anytime by a rider, or a computer, that would be perfect. Alas, such technology is still in the fantasy land.


It already exists, it's not fantasy at all - although it's a progressive spring. It's called air. An air spring with a little on-board compressor would do exactly what you want, and probably be lighter weight as well!
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moses



Joined: 01 May 2005
Posts: 32
Location: uk

PostPosted: Mon Apr 20, 2009 11:35 pm    Post subject: spring Reply with quote

hi
i''v got uprated progressive springs on my triumph 900 and initially found them way too stiff causing suspension to return out too quick when i hit harsh bumps etc, cured this by putting heavier oil into forks which worked a treat and stopped outfit diving into floor compared to originals??? i would definately recommend them but they do require a bit of tweaking with spacers and oil viscosity etc

i'v also completed the sidecar swingarm now along with caliper brackets on new setup and it's being welded on next week along with anti roll bar etc and i'll also try to fit new shock which is going to be a trial and error job

anthony
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docmike



Joined: 27 Jan 2005
Posts: 630
Location: Eastern NC

PostPosted: Tue Apr 21, 2009 12:49 pm    Post subject: Reply with quote

Do you have any idea what rate spring is in there now?

You could measure the sag (how much suspensions drops form unloaded to loaded) My original front shock had about twice as much sag as I wanted so I doubled the spring rate.

Penske can measure spring rates on shocks, I'm sure someone could measure rate on a front spring.

Mike
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