SPRING (COIL) rate for live-axle
Discussion
What rate are your existing springs, both front and rear?
The crucial thing - unless you know what you're doing - is to work out the wheel rates (ie. spring rate x leverage) then maintain the same proportional stiffness front and rear. In other words, if your existing wheel rate is 25% stiffer at the front, then if you change the rear springs, you also need to change the front springs to give a wheel rate about 25% stiffer than the new rear.
If you soften the rear springs in isolation, you'll probably find the car understeers more as a general rule, but will snap quite abruptly into oversteer if the rear springs bottom out or if you apply a bit too much throttle.
Are your dampers already set full soft? Many people set 'Seven' type cars way too stiff. It's likely that if you have something like Spax adjustables, you'll need to be setting them full soft or one click up at the rear, and a couple of clicks firmer at the front, for road use.
Having said all that... for something like your Sylva, I'd expect rear springs of about 130lbs to be a good starting point for road use, though of course it does depend on personal preference and the types of road you are driving on.
The crucial thing - unless you know what you're doing - is to work out the wheel rates (ie. spring rate x leverage) then maintain the same proportional stiffness front and rear. In other words, if your existing wheel rate is 25% stiffer at the front, then if you change the rear springs, you also need to change the front springs to give a wheel rate about 25% stiffer than the new rear.
If you soften the rear springs in isolation, you'll probably find the car understeers more as a general rule, but will snap quite abruptly into oversteer if the rear springs bottom out or if you apply a bit too much throttle.
Are your dampers already set full soft? Many people set 'Seven' type cars way too stiff. It's likely that if you have something like Spax adjustables, you'll need to be setting them full soft or one click up at the rear, and a couple of clicks firmer at the front, for road use.
Having said all that... for something like your Sylva, I'd expect rear springs of about 130lbs to be a good starting point for road use, though of course it does depend on personal preference and the types of road you are driving on.
i forgot to tell that even the front springs are too hard. so i want to change them too.
but 1st i want to start at rear.
dampers are set on full soft. the car is running on 7x13 revolution wheels with 205/60-13 tyres.
as i bought the car 2nd hand i absolutely do not know what kind of springs are fitted, besides that they are so hard that i cannot "push" down the car by hand.
@ sam: its not my sylva
but 1st i want to start at rear.
dampers are set on full soft. the car is running on 7x13 revolution wheels with 205/60-13 tyres.
as i bought the car 2nd hand i absolutely do not know what kind of springs are fitted, besides that they are so hard that i cannot "push" down the car by hand.
@ sam: its not my sylva
Edited by Comadis on Friday 9th May 23:15
Edited by Comadis on Friday 9th May 23:17
Comadis said:
@ sam: its not my sylva
In that case, to give any kind of helpful guidance, I need to know:a) what car it is and how much it weighs.
b) The current spring rates (including anti-roll bars) and suspension leverages (if you don't know, measure them!!)
Sorry, Comadis, but I seem to recall we've been here before, with your query over silencing... if you expect people to be able to give you sensible technical advice, you need to give them the data they need to make a judgement.
It will obviously surprise you to discover that a 500kg Sylva needs different spring rates to a 1500kg saloon.
The relative spring stiffness front and rear will also vary between cars and will (should) have been carefully selected by the development engineers to work with the particular weight distribution and suspension geometry.
I stick by my previous advice, though: if the car handles OK at the moment, do not soften one end of the car in isolation. At the very least, work out the wheel rates, then soften both ends of the car by, say 20%.
Even for the best development engineers, it can be a process of experimentation, though, so expect to have to go though 3 or 4 sets of springs to find the rates you are happiest with... the best I can hope to do with the right data is to get you into the right ballpark.
hi. unfortunately i cant tell any spring rates from the ones which are fitted.
its a ginetta g4, weight is aorund 650kg. Ford Pinto fitted. no antirollbar - front suspension is from spitfire. no panhard rod on rear.
its sure that the springs arent original as the builder wanted to use it on tracks mainly. so its set so hard that the slightest bump on the road cant be absorbed from the suspension.
what do you mean with suspension leverage...how should i measure it?
my sylva is extreme "comfortable" compared to the ginetta. even driving on rough backroads makes fun. but unfortunately i´m also not able to tell you what kind of springs are fitted there.
its a ginetta g4, weight is aorund 650kg. Ford Pinto fitted. no antirollbar - front suspension is from spitfire. no panhard rod on rear.
its sure that the springs arent original as the builder wanted to use it on tracks mainly. so its set so hard that the slightest bump on the road cant be absorbed from the suspension.
what do you mean with suspension leverage...how should i measure it?
my sylva is extreme "comfortable" compared to the ginetta. even driving on rough backroads makes fun. but unfortunately i´m also not able to tell you what kind of springs are fitted there.
Edited by Comadis on Saturday 10th May 11:22
See, now we know that, there's an easy answer.
CONTACT GINETTA!!!
But FWIIW... you can tell what spring rates are fitted. You take them off and measure them.
Working out the leverages is easy to do, but difficult to explain on here. Get hold of a copy of Allan Staniforth's book 'Competition Car Suspension' (or any good book on suspension design) for details. Live axles on coil springs don't offer any leverage, so it's only the front suspension you would need to work out.
CONTACT GINETTA!!!
But FWIIW... you can tell what spring rates are fitted. You take them off and measure them.
Working out the leverages is easy to do, but difficult to explain on here. Get hold of a copy of Allan Staniforth's book 'Competition Car Suspension' (or any good book on suspension design) for details. Live axles on coil springs don't offer any leverage, so it's only the front suspension you would need to work out.
I'm astonished that Dare were unwilling to help. Perhaps it was the way you asked them?
Try the Ginetta Owners Club, the Ginetta discussion group on Yahoo, Paul Stevens or Cottage Classics. No point in re-inventing the wheel if you can avoid it.
If you genuinely can't find advice from specialists or owners, then you're back to my original suggestion... measure the existing spring rates and leverages and work from there.
From experience with 'Seven' type cars, I'd expect actual spring rates (as opposed to wheel rates) somewhere around 180lb front and 130lb rear to be a fair starting point for a car of the Ginetta's weight and balance, for road use, but on the sporting (firm) side. Maybe a wee bit stiffer at the front, since you have a boat anchor instead of an engine.
Try the Ginetta Owners Club, the Ginetta discussion group on Yahoo, Paul Stevens or Cottage Classics. No point in re-inventing the wheel if you can avoid it.
If you genuinely can't find advice from specialists or owners, then you're back to my original suggestion... measure the existing spring rates and leverages and work from there.
From experience with 'Seven' type cars, I'd expect actual spring rates (as opposed to wheel rates) somewhere around 180lb front and 130lb rear to be a fair starting point for a car of the Ginetta's weight and balance, for road use, but on the sporting (firm) side. Maybe a wee bit stiffer at the front, since you have a boat anchor instead of an engine.
contacted also cottage classics in the past. the asked me to contact dare.
dare told me they cant help and do not supply any parts for my car anymore.
strange...strange....
but how is the spring rate measured or calcualted?
by the way: the boat-anchor was the orignal suggestion from ginetta in the 80´s
its not my personal preference as these engines are heavy and look ugly..but they behave well, are undestroybale and good to work on them.
dare told me they cant help and do not supply any parts for my car anymore.
strange...strange....
but how is the spring rate measured or calcualted?
by the way: the boat-anchor was the orignal suggestion from ginetta in the 80´s
its not my personal preference as these engines are heavy and look ugly..but they behave well, are undestroybale and good to work on them.
Edited by Comadis on Saturday 10th May 12:47
Comadis said:
but how is the spring rate measured or calcualted?[/quote)
You measure the spring uncompressed, then load it with a known weight and see how much it compresses.
Springs are rated in pounds weight per inch of compression (at least here in the UK).
Most spring suppliers have machines that will do the job quickly and accurately in seconds, if you ask them nicely.
Get a copy of the Staniforth book. All the equations and methos of measurement you'll need are in there.
You measure the spring uncompressed, then load it with a known weight and see how much it compresses.
Springs are rated in pounds weight per inch of compression (at least here in the UK).
Most spring suppliers have machines that will do the job quickly and accurately in seconds, if you ask them nicely.
Get a copy of the Staniforth book. All the equations and methos of measurement you'll need are in there.
Comadis said:
...are undestroyable...
So long as you use a good quality oil, changed regularly, make sure the oil feed to the top end is in perfect working order and don't over-rev them. Otherwise they have chocolate camshafts and suffer from high bore/ring wear.as i will buy the springs in uk at rallydesign i will not have any possibility to measure the load of the actual ones....and there isnt any company nearby my home which cold measure it for me.
as the srpings are 14,90GBP i can invest in 2 differnt sets without "destroying" too much money.
will take 130lbs and evtl. 150lbs.
front ones afterwards (therefore will contact a guy who races spitfires)
as the srpings are 14,90GBP i can invest in 2 differnt sets without "destroying" too much money.
will take 130lbs and evtl. 150lbs.
front ones afterwards (therefore will contact a guy who races spitfires)
another forum, some helpfull info:
A live axle Fury. :
Fisher recommended springs for all road cars were 180lb fronts and 130lb rears. For a road/track car they go to 225lb fronts and 180lb rears.
so my idea to buy 130lbs for the rear was a perfect choice.
A live axle Fury. :
Fisher recommended springs for all road cars were 180lb fronts and 130lb rears. For a road/track car they go to 225lb fronts and 180lb rears.
so my idea to buy 130lbs for the rear was a perfect choice.
Edited by Comadis on Sunday 11th May 19:27
As well as deciding on the spring rate, you will need to know what uncompressed length you require, especially as you don't have adjustable spring seats on the dampers.
Ideally you should know the corner weights. Lets suppose the rear corners are 300lbs each. If you fit 150lb springs then (assuming the springs are fitted vertically, an allowance will need to be made if they are at an angle) the springs will be compressed 2" when fitted. You can see from this that the uncompressed length will set the ride height.
You might be able to calculate the current spring rate using this information http://www.pagedezigner.com/bluecoil/rate2.htm
Ideally you should know the corner weights. Lets suppose the rear corners are 300lbs each. If you fit 150lb springs then (assuming the springs are fitted vertically, an allowance will need to be made if they are at an angle) the springs will be compressed 2" when fitted. You can see from this that the uncompressed length will set the ride height.
You might be able to calculate the current spring rate using this information http://www.pagedezigner.com/bluecoil/rate2.htm
Edited by singlecoil on Monday 12th May 09:34
only to inform everbody here:
contacted ginetta (dare) 1 week ago: 1 time by online contact sheet, 1 time directly to their email adress with the following words:
dear sirs.i´m searching information about the original suspension setup of my G4/S4.the owner i bought it from fitted extreme hard coils all around which aren’t quite suitable for roaduse. can you supply me with info which spring rates i should use front and rear? live-axle, banjo-type, 4-link, no panhard rod. front is spitfire, no antirollbar. spax dampers all around (non height adjustable). ford OHC engine.if you need more info i´m welcome to supply it to you. the setup should be for road-use only and should result in a "comfortable" ride. thanx in advance and greets, a.
answer: NONE!!!
contacted ginetta (dare) 1 week ago: 1 time by online contact sheet, 1 time directly to their email adress with the following words:
dear sirs.i´m searching information about the original suspension setup of my G4/S4.the owner i bought it from fitted extreme hard coils all around which aren’t quite suitable for roaduse. can you supply me with info which spring rates i should use front and rear? live-axle, banjo-type, 4-link, no panhard rod. front is spitfire, no antirollbar. spax dampers all around (non height adjustable). ford OHC engine.if you need more info i´m welcome to supply it to you. the setup should be for road-use only and should result in a "comfortable" ride. thanx in advance and greets, a.
answer: NONE!!!
Edited by Comadis on Saturday 17th May 00:44
Edited by Comadis on Saturday 17th May 00:46
only to let you know:
i still have NO reply from ginetta...although i contacted them again.
sure i could phone, but i´m good in typing english, but bad in speaking english fluently.
think i will sell the car...if there is no suport from the constructor, there is no reason why a client should suport a product.
no wonder companies like TVR had to close the doors....maybe ginetta in the next 5years, too?
i still have NO reply from ginetta...although i contacted them again.
sure i could phone, but i´m good in typing english, but bad in speaking english fluently.
think i will sell the car...if there is no suport from the constructor, there is no reason why a client should suport a product.
no wonder companies like TVR had to close the doors....maybe ginetta in the next 5years, too?
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