Spring rate TVR Vixen
Discussion
Fiscracer said:
Why would you balance the car without the driver? I've not yet driven mine driver-less.
As I said its like balancing a chair with one short leg. Let me set a little question then. If the fronts are balanced across the axle by changing the ride height L/R and (and the rears are not, driver's side heavier) and you add say 50kg of fuel behind the rear axle what is the impact on front corner weights? Even increase? Even reduction? Uneven change - up or down?
And what about the dynamic effect of fuel slosh As I said its like balancing a chair with one short leg. Let me set a little question then. If the fronts are balanced across the axle by changing the ride height L/R and (and the rears are not, driver's side heavier) and you add say 50kg of fuel behind the rear axle what is the impact on front corner weights? Even increase? Even reduction? Uneven change - up or down?
Hello All, sorry for my bad english.
Thank you for the interesting discussion, but I would like to come back to my original request.
I need replacement for my front shocks and springs.
One Info of my Vixen. The Vixen (M-frame) is converted to Rover V8.
Can someone give me a tip where I can get new front shocks and springs?
Here again the picture of my current shocks and springs. I have also attached a file, where you can see the the current dimensions of my front shocks and springs
File: ---> https://www.dropbox.com/s/fifb376vhyqhvun/Sto%C3%9...
Thank you for the interesting discussion, but I would like to come back to my original request.
I need replacement for my front shocks and springs.
One Info of my Vixen. The Vixen (M-frame) is converted to Rover V8.
Can someone give me a tip where I can get new front shocks and springs?
Here again the picture of my current shocks and springs. I have also attached a file, where you can see the the current dimensions of my front shocks and springs
File: ---> https://www.dropbox.com/s/fifb376vhyqhvun/Sto%C3%9...
asteinha said:
Hello All, sorry for my bad english.
Thank you for the interesting discussion, but I would like to come back to my original request.
I need replacement for my front shocks and springs.
One Info of my Vixen. The Vixen (M-frame) is converted to Rover V8.
Can someone give me a tip where I can get new front shocks and springs?
Here again the picture of my current shocks and springs. I have also attached a file, where you can see the the current dimensions of my front shocks and springs
File: ---> https://www.dropbox.com/s/fifb376vhyqhvun/Sto%C3%9...
You can get replacement shocks from Steve Reid. try e-mailing him.Thank you for the interesting discussion, but I would like to come back to my original request.
I need replacement for my front shocks and springs.
One Info of my Vixen. The Vixen (M-frame) is converted to Rover V8.
Can someone give me a tip where I can get new front shocks and springs?
Here again the picture of my current shocks and springs. I have also attached a file, where you can see the the current dimensions of my front shocks and springs
File: ---> https://www.dropbox.com/s/fifb376vhyqhvun/Sto%C3%9...
Toni,
I think Eletron's car used to be Rover V8 engined, and Ivanhoew's car still is (sort of).
You could ask them what they are/were using, determine the rate of your rears by the formula given previously, and calculate the correct poundage for the front springs as a relationship to the rears.
Demon Tweeks sell springs.
Alles beste,
B.
P.S. Does anybody here have any information on how to determine a wheel rate relationship between front and rear that helps avoid porpoising? I'm fairly sure this is a "per speed" calculation, and includes wheelbase. -Thanks!
I think Eletron's car used to be Rover V8 engined, and Ivanhoew's car still is (sort of).
You could ask them what they are/were using, determine the rate of your rears by the formula given previously, and calculate the correct poundage for the front springs as a relationship to the rears.
Demon Tweeks sell springs.
Alles beste,
B.
P.S. Does anybody here have any information on how to determine a wheel rate relationship between front and rear that helps avoid porpoising? I'm fairly sure this is a "per speed" calculation, and includes wheelbase. -Thanks!
not sure this will help, but i buy all my springs for the race cars from here i do call them for best price though.........
http://www.merlinmotorsport.co.uk/COILOVER-SPRINGS...
http://www.merlinmotorsport.co.uk/advanced_search_...
this page shows they supply old TVR stuff never new that till just
http://www.merlinmotorsport.co.uk/COILOVER-SPRINGS...
http://www.merlinmotorsport.co.uk/advanced_search_...
this page shows they supply old TVR stuff never new that till just
Edited by wadsapple on Thursday 10th January 21:34
Just to add my findings to this discussion:
I picked up a set of GAZ coil-overs for my 3000M which were fitted with I believe 250 lb/in springs. These are way too stiff for a road car. And the wheel frequency bears that out. This is how it's calculated using the Staniforth book, pg. 186:
Wheel frequency (CPM) = 187.7*sqrt(wheel rate/sprung weight)
I'll take the rear setup on the M-series as an example since, unlike the front, the suspension leverage is 1:1 (coil-over attached to upright). My corner weight on the rear (sprung weight) is around 500 lbs. For a 250 lb spring this gives a wheel frequency of 132 CPM. Staniforth gives these ranges:]
60-80 for comfortable road car
80-100 for "firmer and more sporting machinery"
100-125 for racing cars without wings or ground effects.
You can choose where you'd like to be, but 250 pounds (132 CPM) is way too stiff according to both Staniforth and my buttocks.
According to my research a common Spax setup is 135 front and 140 rear. For the rear this gives a more reasonable and sporting 99 CPM. TVRCCNA also claims that the factory rates for the M were 135/140 F/R. Keep in mind that if you are using a "stock" setup feel for tweaking those 40 year old springs are probably not what they used to be and the dampers are shot. Have a serious look at your bushings as well.
For a rally/road car, Staniforth says the front frequency should be around 10% lower than the rear to avoid "bucking." My car fitted with the GAZ rates has a serious bucking issue, very annoying.
Finally, imho it's better to use a softer spring that allows weight transfer than a stiff spring that can produce some unpredictable and twitchy handling. Better to control the car through sway bars (roll) and correct damping.
I picked up a set of GAZ coil-overs for my 3000M which were fitted with I believe 250 lb/in springs. These are way too stiff for a road car. And the wheel frequency bears that out. This is how it's calculated using the Staniforth book, pg. 186:
Wheel frequency (CPM) = 187.7*sqrt(wheel rate/sprung weight)
I'll take the rear setup on the M-series as an example since, unlike the front, the suspension leverage is 1:1 (coil-over attached to upright). My corner weight on the rear (sprung weight) is around 500 lbs. For a 250 lb spring this gives a wheel frequency of 132 CPM. Staniforth gives these ranges:]
60-80 for comfortable road car
80-100 for "firmer and more sporting machinery"
100-125 for racing cars without wings or ground effects.
You can choose where you'd like to be, but 250 pounds (132 CPM) is way too stiff according to both Staniforth and my buttocks.
According to my research a common Spax setup is 135 front and 140 rear. For the rear this gives a more reasonable and sporting 99 CPM. TVRCCNA also claims that the factory rates for the M were 135/140 F/R. Keep in mind that if you are using a "stock" setup feel for tweaking those 40 year old springs are probably not what they used to be and the dampers are shot. Have a serious look at your bushings as well.
For a rally/road car, Staniforth says the front frequency should be around 10% lower than the rear to avoid "bucking." My car fitted with the GAZ rates has a serious bucking issue, very annoying.
Finally, imho it's better to use a softer spring that allows weight transfer than a stiff spring that can produce some unpredictable and twitchy handling. Better to control the car through sway bars (roll) and correct damping.
So, looks like GAZ supplied the car with 275 lb. front and 200 lb rear springs springs. Front has a leverage ratio of 0.65 so using the 275 lb. spring this gives 112 CPM and 118 for the rear. If I move the rear 200 lb. springs to the front I'll get 95 CPM and then I'll shoot for 104.5 CPM in the rear which requires a 155 lb spring for the rear.
Sorry to rekindle this topic...
Car has been porpoising along a one type of road: concrete segmented dual-carriageway (A40 from Oxford to Bicester / A12 from Chelmsford to m25)
Car is set up with vixen fins-wheels on 185/65/15 tyres
22psi on front & 24psi on rear tyre pressures
2x200lbs springs on front
4x100lbs springs on rear (four shocks and four springs)
New AVO shocks all round.
dampers presently set to 7 of 14 on fronts and 3 on all rears.
Spring pre-load is quite low (therefore low ride height) but doesn't bottom-out or scrap anywhere.
Car is mainly road - but will be using it on trackdays in the coming year - non-competitive.
Anything I can adjust in the setup to remove the porpoising?
Car has been porpoising along a one type of road: concrete segmented dual-carriageway (A40 from Oxford to Bicester / A12 from Chelmsford to m25)
Car is set up with vixen fins-wheels on 185/65/15 tyres
22psi on front & 24psi on rear tyre pressures
2x200lbs springs on front
4x100lbs springs on rear (four shocks and four springs)
New AVO shocks all round.
dampers presently set to 7 of 14 on fronts and 3 on all rears.
Spring pre-load is quite low (therefore low ride height) but doesn't bottom-out or scrap anywhere.
Car is mainly road - but will be using it on trackdays in the coming year - non-competitive.
Anything I can adjust in the setup to remove the porpoising?
octanetorque said:
Sorry to rekindle this topic...
Car has been porpoising along a one type of road: concrete segmented dual-carriageway (A40 from Oxford to Bicester / A12 from Chelmsford to m25)
Car is set up with vixen fins-wheels on 185/65/15 tyres
22psi on front & 24psi on rear tyre pressures
2x200lbs springs on front
4x100lbs springs on rear (four shocks and four springs)
New AVO shocks all round.
dampers presently set to 7 of 14 on fronts and 3 on all rears.
Spring pre-load is quite low (therefore low ride height) but doesn't bottom-out or scrap anywhere.
Car is mainly road - but will be using it on trackdays in the coming year - non-competitive.
Anything I can adjust in the setup to remove the porpoising?
Exactly! Anything. In theory, anyway. Porpoising is a function of sympathetic resonant frequencies (I'm sure I'm misabusing terminology). So, if you were to stiffen either front OR rear springs or damper rates, or were to to alter your speed, the problem should go away (and return under different conditions/on a different piece of road). Car has been porpoising along a one type of road: concrete segmented dual-carriageway (A40 from Oxford to Bicester / A12 from Chelmsford to m25)
Car is set up with vixen fins-wheels on 185/65/15 tyres
22psi on front & 24psi on rear tyre pressures
2x200lbs springs on front
4x100lbs springs on rear (four shocks and four springs)
New AVO shocks all round.
dampers presently set to 7 of 14 on fronts and 3 on all rears.
Spring pre-load is quite low (therefore low ride height) but doesn't bottom-out or scrap anywhere.
Car is mainly road - but will be using it on trackdays in the coming year - non-competitive.
Anything I can adjust in the setup to remove the porpoising?
If the AVOs are adjustable, I would try changing the setting, on the rears, by a couple of increments. (Too stiff, and the car will get more unstable, in the wet.)
Best,
B.
As a very very crude rule of thumb I think if it were me I would soften the rear a couple of clicks and firm up the fronts and see how she feels.
If you have changed the shocks over to AVOs presumably you have adjustable spring platforms? Might be work getting the corners weighted and balanced, or at the very least the ride heights and front and rear tracking and cambers checked.
If you have changed the shocks over to AVOs presumably you have adjustable spring platforms? Might be work getting the corners weighted and balanced, or at the very least the ride heights and front and rear tracking and cambers checked.
tomtrout said:
As a very very crude rule of thumb I think if it were me I would soften the rear a couple of clicks and firm up the fronts and see how she feels.
If you have changed the shocks over to AVOs presumably you have adjustable spring platforms? Might be work getting the corners weighted and balanced, or at the very least the ride heights and front and rear tracking and cambers checked.
Pump up the front tyres. 26f and 24r, soften the rear end a touch.If you have changed the shocks over to AVOs presumably you have adjustable spring platforms? Might be work getting the corners weighted and balanced, or at the very least the ride heights and front and rear tracking and cambers checked.
200lb isn't excessive though I am running about 190 all round.
A lot will be personal preferences..the trouble with adjustable shocks is that it just gives you far more methods of cocking up your handling
N
tomtrout said:
As a very very crude rule of thumb I think if it were me I would soften the rear a couple of clicks and firm up the fronts and see how she feels.
If you have changed the shocks over to AVOs presumably you have adjustable spring platforms? Might be work getting the corners weighted and balanced, or at the very least the ride heights and front and rear tracking and cambers checked.
If you have changed the shocks over to AVOs presumably you have adjustable spring platforms? Might be work getting the corners weighted and balanced, or at the very least the ride heights and front and rear tracking and cambers checked.
Dollyman1850 said:
Pump up the front tyres. 26f and 24r, soften the rear end a touch.
200lb isn't excessive though I am running about 190 all round.
A lot will be personal preferences..the trouble with adjustable shocks is that it just gives you far more methods of cocking up your handling
N
I'll report back after Xmas car is receiving some engine work. Might be worth mentioning that varying speed from 50-70 didn't seem to make any noticeable difference. Even at slow speeds in traffic on those roads there is some noticeable fore-aft bucking!200lb isn't excessive though I am running about 190 all round.
A lot will be personal preferences..the trouble with adjustable shocks is that it just gives you far more methods of cocking up your handling
N
Corner weighting has been on the to-do list for a while - I'll happily up the front pressures - this just to harden up the front, yes? By soften the rear you mean springs -or- dampers, yes?
RE tracking - for modern tyres/roads etc would these setting be about right (scalped from Yahoo group: https://groups.yahoo.com/neo/groups/TVR_Pre1980/in...
Front 1/16" toe out, rear 1/16" toe in
front caster 4 degrees
one degree camber on all corners.
Any suggestions on ride height?
Final question - I understand the balance idea across the pivot bars with 4x spring & damper - for the more knowledgeable I bow before your expertise, but what would the expected difference be between 4x spring & damper and 2 spring and four damper setups?
Thanks as always - Back to the mince pies!
I run custom build Protech shocs, and are very happy with their service. Ordered a set for a custom IRS spitfire , and got them shipped the same day. And prices are resonable as well.
http://www.protechshocks.co.uk/
http://www.protechshocks.co.uk/
octanetorque said:
. . . Might be worth mentioning that varying speed from 50-70 didn't seem to make any noticeable difference. Even at slow speeds in traffic on those roads there is some noticeable fore-aft bucking. . .
In that case, while I am sure that the bucking is very unpleasant, the phenomenon cannot be "porpoising."
Best,
B.
Slow M said:
Toni,
I think Eletron's car used to be Rover V8 engined, and Ivanhoew's car still is (sort of).
You could ask them what they are/were using, determine the rate of your rears by the formula given previously, and calculate the correct poundage for the front springs as a relationship to the rears.
Demon Tweeks sell springs.
Alles beste,
B.
P.S. Does anybody here have any information on how to determine a wheel rate relationship between front and rear that helps avoid porpoising? I'm fairly sure this is a "per speed" calculation, and includes wheelbase. -Thanks!
Electron's car is currently 302 with iron heads. I'll nudge him to see if he know what springs it has (tbh I think he's running what it came with, as it's not traveled very far and I don't remember him saying he'd changed them)I think Eletron's car used to be Rover V8 engined, and Ivanhoew's car still is (sort of).
You could ask them what they are/were using, determine the rate of your rears by the formula given previously, and calculate the correct poundage for the front springs as a relationship to the rears.
Demon Tweeks sell springs.
Alles beste,
B.
P.S. Does anybody here have any information on how to determine a wheel rate relationship between front and rear that helps avoid porpoising? I'm fairly sure this is a "per speed" calculation, and includes wheelbase. -Thanks!
cheers
Nick
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