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#Post#: 70588--------------------------------------------------
Rear Parabolics - 109" Truck Cab
DIR By: NomduJour
Date: August 13, 2013, 12:34 pm
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Need to replace the seized-solid original springs on my 109
truck cab - the supposedly-UK-made GMEs from Paddock look decent
value at about £280 a set (Bearmach's UK-made ones - GB? - are
closer to £450). Obviously already discounted the Britpart ones,
Rocky Mountains seem to get varied reviews and Heystee would be
nice but are too much for something that won't see a lot of use.
However, Paddock recommend only the four-leaf rears for the 109
but don't specify a spring rate. The internet tells me that an
88 hard top has pretty much the same unladen weight over the
back axle as a 109 soft top, and as it won't see any great
weight in the back, I'd prefer to go for the option which offers
the better ride - has anyone tried the GME three-leaf parabolics
on the back of a 109 soft top or truck cab?
#Post#: 70592--------------------------------------------------
Re: Rear Parabolics - 109" Truck Cab
DIR By: Col
Date: August 13, 2013, 1:13 pm
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Hi, I have 3 leaf parabolics on my 109, I usually carry a bit of
weight as I have made a box which houses a Tirfor and rope,
shackles etc and other bits and bobs for recovery.
The ride quality is good, don't know who's make they are as they
were fitted when I had a galv chassis done. :smile1 :smile1
#Post#: 70598--------------------------------------------------
Re: Rear Parabolics - 109" Truck Cab
DIR By: niteram
Date: August 13, 2013, 3:40 pm
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not got paras yet, but as mine is a 5 door wagon, I guess the 4
leafs would be best for me as a bit heavier than pickup. I would
think the 3 leafs would do for non station wagon
#Post#: 70600--------------------------------------------------
Re: Rear Parabolics - 109" Truck Cab
DIR By: NomduJour
Date: August 13, 2013, 3:49 pm
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Thanks, might give it a go and see what happens.
Bit annoying that none of the resellers appear to know the
spring rates of the different versions they supply. Would also
be interesting to know the effects on roll stiffness given that
there are so few Series with anti-roll bars.
#Post#: 70621--------------------------------------------------
Re: Rear Parabolics - 109" Truck Cab
DIR By: estwdjhn
Date: August 13, 2013, 9:35 pm
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Call my a cynical old so-n-so, but I'd struggle to see the point
of fitting paras to the back of a 109". They ride quite well
anyway, and para's would destroy the (otherwise quite decent)
roadholding a 109" pickup/softotp has - my truck is on Std
springs and if cornered hard the front inside wheel lifts first
- I wouldn't want anything where the rear had more sway in it.
Why not save yourself a small fortune, split the springs, throw
some grease in them and put them back on? If they are like most
original sets I've had, once that's been done they have been
good for another 100,000 miles, while making the truck stand
tall and ride well.
#Post#: 70671--------------------------------------------------
Re: Rear Parabolics - 109" Truck Cab
DIR By: big-chris
Date: August 14, 2013, 7:01 am
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I have four leaf ones fitted to my LWB hard top, I fitted them
because I wanted the lift so the 9.00's fitted nice in the arch,
the four leaf springs are usually for the more heavy bodied
models e.g. ambulance, fire trucks, one ton for the additional
pay-load..... My truck does ride a little hard I must admit, I'm
sure you will be very happy with three leaves on the rear or as
John says fix your own, or spend £100 and buy a pair of standard
units.....
GME are based in Sheffield, you can buy direct but it does work
out cheaper to buy from Paddock as they buy in bulk at a better
price.....
#Post#: 70672--------------------------------------------------
Re: Rear Parabolics - 109" Truck Cab
DIR By: NomduJour
Date: August 14, 2013, 7:06 am
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[quote=estwdjhn]Call my a cynical old so-n-so, but I'd struggle
to see the point of fitting paras to the back of a 109". They
ride quite well anyway, and para's would destroy the (otherwise
quite decent) roadholding a 109" pickup/softotp has - my truck
is on Std springs and if cornered hard the front inside wheel
lifts first - I wouldn't want anything where the rear had more
sway in it[/quote]
All subjective but the first thing that comes to mind with a
worse ride than the average Series on its original springs is
the old yard tractor. Mine also has factory heavy duty rear
springs, so even if I did chuck them in a barrel of diesel for a
week they'd still be very stiff.
There's no reason to suggest that parabolics would worsen
roadholding either - assuming the same spring rate, they should
appreciably improve it by keeping the wheels in better contact
with the road - proper progressive rate and big reduction in
unsprung weight (assuming the dampers are up to it given
parabolics' lack of friction damping). Although the actual
parabolic springs themselves look like they have a lot less
lateral stiffness than a standard leaf, I wonder how much of the
perceived effect on body roll (spring rate like-for-like) is due
to the higher CofG from the inevitable 20 or 30mm lift and the
initial greater flexibility under small loads/bumps. Not sure
why someone hasn't marketed a Santana-style anti-roll bar kit.
There's a reason why most things still made with leaf springs
use parabolics.
Re GME - Owen Springs (am i right in thinking they're related to
the former British Springs?) are also up that way, but they seem
to be pricier (albeit made on-site).
#Post#: 70691--------------------------------------------------
Re: Rear Parabolics - 109" Truck Cab
DIR By: Col
Date: August 14, 2013, 11:32 am
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They are a lot more comfortable than standard springs but do
give a lot more body roll, also they tend to flex a bit more
off-road.
#Post#: 70778--------------------------------------------------
Re: Rear Parabolics - 109" Truck Cab
DIR By: estwdjhn
Date: August 14, 2013, 4:09 pm
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--- Quote from: NomduJour link ---
>
>
> All subjective but the first thing that comes to mind with a
worse ride than the average Series on its original springs is
the old yard tractor.
>
--- End Quote ---
Apples and oranges. The average series rides very poorly because
the springs are a rusty mess, and it's only used once in a blue
moon. A decent LWB series is pretty smooth riding, certainly
from the drivers seat (less so if your on a sidefacing bench in
the back in my experience).
--- Quote ---
>
> Mine also has factory heavy duty rear springs, so even if I
did chuck them in a barrel of diesel for a week they'd still be
very stiff.
>
--- End Quote ---
Split them, de-rust them, grease them. Leave the bottom leaf or
even two leaves out. Then refit. Amazing difference. That's what
my truck has, and it does it no harm at-all. IMHO a HD spring
down a couple of leaves is as good or better than the std ones.
--- Quote ---
>
> There's no reason to suggest that parabolics would worsen
roadholding either - assuming the same spring rate, they should
appreciably improve it by keeping the wheels in better contact
with the road - proper progressive rate and big reduction in
unsprung weight (assuming the dampers are up to it given
parabolics' lack of friction damping). Although the actual
parabolic springs themselves look like they have a lot less
lateral stiffness than a standard leaf, I wonder how much of the
perceived effect on body roll (spring rate like-for-like) is due
to the higher CofG from the inevitable 20 or 30mm lift and the
initial greater flexibility under small loads/bumps. Not sure
why someone hasn't marketed a Santana-style anti-roll bar kit.
>
> There's a reason why most things still made with leaf springs
use parabolics.
>
--- End Quote ---
I suspect that if you want the ultimate in handling, para's on
the front and standard leaves on the back might just work. I
really wouldn't want a motor set up the other way round.
Having had my boss follow me on his bike (which means he can
tell me what it's doing when), as my 109" is progressively
cornered harder on a dry road the following happens. This is
with the truck laden with about 1/4 ton, mainly right behind the
cab (experiments have found this is about optimal - they are a
bit skitish empty, and wallow when loaded right up)
1) Body roll increases.
2) Outside of front axle maxes out on travel (we think it hits
the bump stops, but no-one's felt like getting close enough to
check!).
3) Inside of front axle lifts
4) Back axle starts to drift sideways noticeably.
5) Outside of back axle maxes out on travel - inside wheel
starts to lift (this is only up to about 30mph - at higher
speeds the rate of drift means I've never had the bottle to
carry on locking over till the wheels lift).
This suggests to me that increasing the travel or softness of
the rear springs (para's generally do both) is most likely going
to result in the front axle just coming off the ground sooner.
I'm not sure I'd want an ARB much either - I would expect it
would make corners feel much steadier to a point, and then quite
suddenly the axles would come up and it would probably be
goodnight vienna. (I've had a series so far up on two wheels I
thought it was going over, and trust me, it's really not a good
feeling - even at only 15mph).
That said, the springs are only a small part of the story - the
biggest make or break in terms of handling is tyres - I've some
AT's on at the moment that hold the road like glue. When I had
bargrips, the backend broke out sideways long before anything
else interesting happened. I remember having a lift with Stig,
and I couldn't believe how well his motor went round corners - I
suspect now the wouldn't be a lot between his and mine, and all
that's changed on mine in the interim is the tyres (his now has
wider axles, so probably corners faster still, but hey, such is
life).
#Post#: 70782--------------------------------------------------
Re: Rear Parabolics - 109" Truck Cab
DIR By: Joskin
Date: August 14, 2013, 4:23 pm
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Must agree with JE here, if the ride on a 109 is bad its because
one or more of the components is shagged, that or someone has
fitted heavy duty springs to a motor that runs around with
little other than a dinner box and flask for ballast......
Good order standard rears and working shocks will give a pretty
reasonable ride in a 109, an 88 is a different kettle of fish
altogether.
I've tried many combinations of good bad and indifferent
springs, and IMHO I'd say the best ride "all round" (because
ultimately there's allways a comprimise somewhere) was with
paras on the front and good standards on the rear.
What suits one may infuriate another, best thing is blag a ride
in someone elses motor if you can, it could save you a fortune
or make your mind up right away :thumbs:
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