alistairolsen
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| posted on 30/5/10 at 02:39 PM |
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Motorbike Suspension
Im looking to run a live axle much like the locost arrangement in the back of a current project.
Unfortunately Im short of height above the axle so Ill have to hang the bottom shock mount off the rear of the 4 bar brackets at the bottom.
This will allow a coilover length of around 11 inches ideally.
I wondered about using motorcycle dampers, obviously not the modern sportsbike units as they tend to be far too stiff and short, but are there any
applications which are 8-11 inches long with ~200lbs springs??
My Build Thread
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MikeCapon
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| posted on 1/6/10 at 07:32 AM |
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Hi Alistair,
I have some info on this which may be of help.
Most twin shock units found on older and recent retro style bikes are around the 300 - 330mm mark. However the springs are generally in the 90 - 120
lbs/in range. You could look at changing the springs but you should be aware that the spring IDs on many OE twin shock units are not standard (
1.9" or 2.25" ). They are often smaller than 1.9" and a good few are tapered. This makes finding alternative springs a bit
tricky.
There may be some quad units that would do the trick. I have a database with most of this info. If you can specify the following I'll see what I
can find for you. I'll need open length, stroke (open length - closed length) and the spring rate you're looking for.
There are a few performance quads which are supplied OE with double adjustable units. Lots of these are changed before the quads are used as they are
rarely as good (for quad use) as the aftermarket stuff. These may be suitable as well as cheap/available.
Cheers,
Mike
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alistairolsen
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| posted on 1/6/10 at 12:02 PM |
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Well i haven't done the mounts yet, so anything from about 9-13 inches could be accommodated I guess.
Working on that basis I suspect i wont get more than 3 inches of travel, but the more the better really!
As far as rate goes, its a front engined rwd car with a similar layout to a locost and an all up weight of 800kg so I would guess around 225lbs
wouldn't be tooo far away.
Cheers!
My Build Thread
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Marcus
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| posted on 1/6/10 at 08:46 PM |
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Hmm, we went with bike shocks for the first Locost build, we turned up some new spring seats and fitted 1.9" springs. The ride was verrrry
bouncy, I don't think the shocks were up to it. They must have been valved for vry low rate springs. In the end, they lasted a year to be
replaced with Gaz units, the difference was amazing and the ride improved no end.
I wouldn't do it again.
Marcus
Because kits are for girls!!
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MikeCapon
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| posted on 2/6/10 at 07:30 AM |
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Morning all,
I've had a trawl through my info and sadly there's not a lot of units that fulfil the criteria.
I have discounted very old bikes as the only units kicking around will be very tired, probably completely useless.
Iv'e attached a small list of bikes/quads that are closeish to what you have asked for.
The one unit that may be worth a go is from the Triumph Rocket III.
Marcus, you're probably right in guessing that changing the springs was too much for the shocks damping capacity. If you up a spring rate the
damping should be increased to suit. As most of these type of shocks only use a spring around the 100-120 lbs in mark a Locost is likely to finish up
being under damped.
The other thing to watch for is simply worn out or otherwise non functioning units. Pulling the spring off and testing by hand will at least eliminate
the completely duff ones.
Lastly the "trick" quad shocks I was talking about are much too long, around 400mm open with 110mm of stroke.
HTH,
Mike
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alistairolsen
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| posted on 2/6/10 at 10:07 AM |
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Thanks a lot for that! Where on earth did you get a database of that detail?
Can you tell me offhand what the details are for the rear spring/shock on a Ducati 748?
Cheers
[Edited on 2/6/10 by alistairolsen]
My Build Thread
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MikeCapon
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| posted on 2/6/10 at 10:51 AM |
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It was/is my job/passion.....
Duke 748 94-99
Open length 305
Stroke 65
Eye fittings top + bottom 10mm X 22mm wide
Spring 400 lbs/in
If you want anything more specific please let me know.
Cheers,
Mike
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