big-vee-twin
|
| posted on 5/2/12 at 06:41 PM |
|
|
Suspension Configuration & Adjusting
Evening All,
On my front wishbones I have 12 inch shock absorbers with 275Lb's springs. The springs are 6'' long.
My car has a Duratec lump with shortened sump. The sump is nearly touching the floor about 10mm clearance.
I haven't adjusted ride height yet but the adjuster is already 50% along the thread with the car on the deck. I'm thinking I may run out
of adjustment before I get the required ground clearance.
If this proves to be the case, will I require a longer spring so that I can start loading the spring earlier on the adjustment?
Or will I need longer, say 13 inch shockers.
The car is a GTS Locost not a Haynes.
Duratec Engine is fitted, MS2 Extra V3 is assembled and tested, engine running, car now built. IVA passed 26/02/2016
http://www.triangleltd.com
|
|
|
|
|
snowy2
|
| posted on 5/2/12 at 07:59 PM |
|
|
you could alter the top shocker mount to give either less angle to the bottom mount or closer to the bottom mount both will do as you want, reducing
the angle will affect the effective rate of the spring (increasing it towards the actual rate of the spring.)
My car has a pinto in it (a boat anchor to be honest) and the overall weight of the car is 770kg (me sat in it) 440 front and 330 rear..... my springs
are 225lb/in fronts and 150lb/in rear my rear shockers are near vertical. The car has just over 4" ground clearance.
when i got the car the previous owner was running 190lb/in rears and 250lb/in fronts and was looking to increase the springs to "improve the
handling", which to be honest wasn't great and was the wrong way to go.....softening the springs had a huge and beneficial effect on the
cars handling improving it loads.
sometimes you are the pigeon, most of the time the statue.
|
|
|
flange nut
|
| posted on 5/2/12 at 08:29 PM |
|
|
10mm clearance on the sump! What distance are your bottom chassis rails to the ground? It sounds to me like your engine is way too low in the
chassis.
[Edited on 5/2/12 by flange nut]
|
|
|
whitestu
|
| posted on 5/2/12 at 09:33 PM |
|
|
Are the bottom wishbones roughly horizontal? If so and you only have 10mm you need a shorter sump.
Stu
|
|
|
big-vee-twin
|
| posted on 5/2/12 at 09:44 PM |
|
|
The engine is not too low in the chassis, and already has a 75mm deep shortened sump from Dunnell, if it was any shorter I wouldn't have a sump
- LOL.
The chassis rails are aprox 25mm from the ground, thats why I believe its just a suspension/shock absorber issue.
Thanks for your replies so far 
Duratec Engine is fitted, MS2 Extra V3 is assembled and tested, engine running, car now built. IVA passed 26/02/2016
http://www.triangleltd.com
|
|
|
flange nut
|
| posted on 5/2/12 at 11:37 PM |
|
|
I agreed your engine isn't too low, but with only 25mm between the lower chassis and the ground something is certainly not right. As a previous
poster has asked, what angle are you front wishbones? Do they slope up from chassis to upright or down from chassis to upright? I've just
checked on the GTS web site and it seems they recommend 12 inch shocks all round for the Panther and 12 inch front and 13 inch rear for the Locost.
|
|
|
Dusty
|
| posted on 6/2/12 at 01:04 AM |
|
|
Shockers are the length recommended by GTS. In principle I don't think you should go stronger springs on the front of a seven as a first choice
when considering ride height rather than handling issues. I would tend to look at 7" or even 8" springs of the current poundage.
But................. you need more information before proceeding.
First check your shocker specifications. What are their fully open and fully closed lengths, eye to eye? What is their length currently on the car at
rest? Place a jack under the centre of the front of the car and jack up till the front lower wishbones are parallel to the ground. What is the eye to
eye length of the shocks now? Out of interest what is the chassis rail to ground clearance now?
When you have all these measurements I think you can work out if the 12" shockers are the ideal length for the chassis. A shocker has a range of
movement (extended length minus closed length minus bump stop length) which will be about 3-3.5" inches for a 12" shocker. When set up on
the car with driver in the seat and the suspension arms parallel to the ground (also should mean ride height is correct) the shocker should be about
one third compressed or two thirds extended considered from te point of view of their extended length. For a 12" shocker that is fully
compressed at 9", the rest position should be with the shocker measuring 10". This leaves 2" more compression available for bumps
and 1" extension for dips.
Before deciding on the solution to your ride height problem I think you should post up these measurements.
|
|
|
scutter
|
| posted on 6/2/12 at 08:38 AM |
|
|
I agree with Dusty, 6" does sound a little short most cars I know run 8" springs.
ATB Dan.
The less I worked, the more i liked it.
|
|
|
big-vee-twin
|
| posted on 6/2/12 at 12:40 PM |
|
|
Many Thanks, I will measure up and post in due course, I've looked at many types of shocker and they all do seem to have longer springs than the
ones which come with mine.
I've made the assumption that the suspension arrangement is ok as it came to me as a kit and Darren knows about suspension, so thats what led me
to thinking the shocker and spring is not quite right.
Duratec Engine is fitted, MS2 Extra V3 is assembled and tested, engine running, car now built. IVA passed 26/02/2016
http://www.triangleltd.com
|
|
|
big-vee-twin
|
| posted on 7/2/12 at 05:15 PM |
|
|
Afternoon all, been playing with the shockers, their length is 12 inches open and there is 3 1/2 inches of movement available unloaded and with the
weight of the car on them 2 1/2 inches.
So as you say 1 inch for dip and 2 1/2 for compression.
I have wound up the springs nearly all the way through the adjustment and so far achieved 80mm under the lowest part of the sump.
So I think as suspected, I need to swap out the 6 inch springs for 8 inch one's.
Many thanks for your advice I was starting to have kittens about ground clearance, but it looks like 100mm could be achievable with the correct length
springs.
Does any one know of a Locost supplier of coil over springs?
Duratec Engine is fitted, MS2 Extra V3 is assembled and tested, engine running, car now built. IVA passed 26/02/2016
http://www.triangleltd.com
|
|
|
flange nut
|
| posted on 7/2/12 at 06:53 PM |
|
|
Try Rally Design.
|
|
|
Dusty
|
| posted on 8/2/12 at 01:23 AM |
|
|
I'm not convinced the solution is springs but can't give a sensible answer as I'm still short on data. You don't give a figure
for either the shocker length or the sump to ground clearance when you jack the car up to wishbones parallel to the ground. Without this is is not
possible to confirm the shockers are the correct length for your car.
Your sump clearance was 10mm. You say the shocks were measured at roughly one third compression which is about correct but was this with the clearance
at 10mm or the 80mm you got at the end of play? If the former then your shocks must be topping out now you have raised the spring platforms and the
shocks are too short. You will have no shock extension to allow suspension droop to cope with negative G changes and wheels will leave the ground. If
the latter then the shocks may be OK. Can you put up the above measurements?
|
|
|
big-vee-twin
|
| posted on 8/2/12 at 09:30 AM |
|
|
The 1 inch dip, 2 1/2 inch compression was measured with the car on the ground and 80mm sump clearance.
I will check with the bottom wishbone level and come back.
Again many thanks for your help.
[Edited on 8/2/12 by big-vee-twin]
Duratec Engine is fitted, MS2 Extra V3 is assembled and tested, engine running, car now built. IVA passed 26/02/2016
http://www.triangleltd.com
|
|
|
big-vee-twin
|
| posted on 8/2/12 at 11:30 AM |
|
|
ok, have checked bottom wishbone and it is basically level (very slight drop to wheel end), top wishbone slightly rising towards wheel end
What do you think?
Thanks
Kev
Duratec Engine is fitted, MS2 Extra V3 is assembled and tested, engine running, car now built. IVA passed 26/02/2016
http://www.triangleltd.com
|
|
|
Dusty
|
| posted on 11/2/12 at 10:50 AM |
|
|
Sorry for the delay. The last figures you give sound good. The front wishbones are at sensible starting angles and the shocks extended 2/3 so ride
height is correct. So I would not be changing the shocks. Spring poundage is also about right. (Sorry for my doubts, I'm more used to dealing
with early Robin Hoods where components are much more random)
One last important point about the bottom wishbone is that the true wishbone is a straight line between the centre of the chassis bush on the inner
end and the ball joint at the outer end of the wishbone. It is this line that should be horizontal. There might be a little more ride height
designed in that you have not yet adjusted for and can gain by setting true wishbone horizontal.
When this is done you have had all the gains in sump clearance from setting ride height. Your spring platforms are way up the shockers. Going longer
at the same poundage is sensible to move the platform down to mid shock and spread the load to more coils, reducing the risk of the spring becoming
coil bound and it just looks better! Look at the shocker and the current position of the platform. A 2" longer spring will move the platform
down about 1.5". About right? But it isn't going to gain you any extra ride height.
Starting point of true wishbone horizontal is just that. A starting point! By experience/experiment you may find that the handling is improved by
small changes to ride height, up or down.
You may be able to gain further sump clearance by raising shimming the engine mounts.
|
|
|
big-vee-twin
|
| posted on 11/2/12 at 04:42 PM |
|
|
I am going to get some 8 inch springs from Rally Design, Thats where the dampers and coil kit came from in the first place, the spring platform
currenly is very near the top of the thread, so running out of adjustment.
I think when the springs are changed it will be ok, as you say there probably will be a little more to come, when I 've changed them out.
Many thanks for your help, I've learn't something about suspension which is great.
Duratec Engine is fitted, MS2 Extra V3 is assembled and tested, engine running, car now built. IVA passed 26/02/2016
http://www.triangleltd.com
|
|
|
