To lower or not to lower ?

[Aristotle]

Can report much fun is being had in new to me 1500 Spitfire, only bashing round the lanes so far as I get used to and learn about robustness of the device but so far so good.

I even ventured to the local Tesco for the weekly food and wine ration, parking in a spot where I could admire the outline from afar as I wandered back laden with provisions.

Seen from afar (for the first time really) she seemed quite high at the front and in coming back home trawled the forum for guidance on ride height and found the advice that the lower wishbones should be parallel with the ground.

Mine (see photo) are at quite an angle - outboard much lower than inboard end.

So my question is - how is standard ride height determined and is there a standard ride height I could measure to - to identify if and by how much the height might be out ?

 

 

 

[Mjit]

"Lower wishbones parallel with the road" is a theoretical ideal, as it means as you bounce along the road the bottom of the vertical link goes up and down it does it with the minimum of in and out movement, so you maintain the maximum contact patch of the tyre to the road (rather then rolling onto the shoulders).

Of course that needs the rest of the suspension geometry to be built for that, you'd ideally want both upper and lower wishbones to be parallel so you don't get any rocking from the top wishbone either.  And then you need the steering rack to be in the correct place to minimise bump steer.  And then...  In reality that's more race car talk though, not cheap assed 1970s British sports cars cobbled together from parts first designed for a cheap family saloon in the 1950s.

Your car doesn't look especially odd - though those springs don't look like they've been on the car since it rolled off the production line so you might have standard length but stiffer front springs.  They would compress less under the static weight of the car so increase the ride height/push the lower wishbone further away from parallel.  Not sure there's really a way to tell without stripping them down (others will confirm/correct) but if they are your options are:

a) Different springs, either standard rate or uprated/shortened ones.
b) Different dampers with adjustable lower spring pans so you can adjust how compressed the spring is unloaded, which effects how long it is when fitted/loaded with the weight of the car, which effects the ride height.

I have b) on my car so my ride height measurements wouldn't help you know if you're are normal or not.

Edited September 27, 2023 by Mjit

[johny]

This is the diagram in the Vitesse/GT6 manual and the associated data puts the camber as a little bit positive so looks about the right set up for the road...

[JohnD]

Aristotle,

As above, a shorter but stiffer spring can lower the car and provide less positive camber. but there is another adjustment.

The shims, between the lower wishbone brackets and the chassis rail, Pt.No. 122022.    There is length on the stud for six or more of the shims, when there will  be one-three from the factory.   About six will give you about 2 degrees of negative, if combined with a shorter spring, and/or adjustable spring seats, but Canley's (I nicked the diagram from them, so they deserve a plug!) can sell you them for £2.20 each, so a cheap mod.   OR, make them, from alloy plate!

John

[Pete Lewis]

and any geometry checks have the old 150lbs on each seat to set the static ride height before you measure or adjust anything 

you obviously have replacement springs and shockers fitted  the originals are long gone so there is pleanty of possible

spring lengths and shocker platforms to be incorrect 

front spring fitted lengths are in the manual 
pete

[Aristotle]

On 27/09/2023 at 11:23, Mjit said:

not cheap assed 1970s British sports cars cobbled together from parts first designed for a cheap family saloon in the 1950s.

Love that.

[Aristotle]

Thanks to all for your advice.

Having checked both Haynes and the BL Manual it's obvious there's more ground clearance than they quote.

Haynes says 4.4 inches and BL Manual says 4.4 to 5 inches - - I've actually got 7.25 inches reducing gradually towards the rear.

So I guess it can come down at least a couples if inches.

Pete, I'll check the manual for the standard length of springs and check with what's on the car, I am though drawn to Mjit's solution of adjustables.

Once done (and after much cogitating) I'll check the camber as it does look like there's lots of positive applied and now examined more closely there is more wear on the outside edge of the tyres than the inside.

Any further suggestions gratefully accepted - - - good fun this !

 

 

[Aristotle]

2 hours ago, Pete Lewis said:

and any geometry checks have the old 150lbs on each seat to set the static ride height before you measure or adjust anything 

Pete, I don't have a clue what this means.

[Pete Lewis]

do you happen to have  a workshop manual   have alook at Triumph Car Service manuals - Vitessesteve  doesnt have specific 1500 spit but the base data for spitfire doesnt change much 

for any toe/amber/castor/suspension geometry on pretty much all the small chassis cars 

the data says you must set the car to its base static ride height  and to do that DIY is add 150lbs to each seat

(or get rentacrowd in ) this sets the car in its average ride condition as on the road 

some GT6 do have unladen figures 

Pete

Edited September 28, 2023 by Pete Lewis

[Aristotle]

30 minutes ago, Pete Lewis said:

do you happen to have  a workshop manual   have alook at Triumph Car Service manuals - Vitessesteve  doesnt have specific 1500 spit but the base data for spitfire doesnt change much 

for any toe/amber/castor/suspension geometry on pretty much all the small chassis cars 

the data says you must set the car to its base static ride height  and to do that DIY is add 150lbs to each seat

(or get rentacrowd in ) this sets the car in its average ride condition as on the road 

some GT6 do have unladen figures 

Pete

Aaaah - the light of awakening breaks over the snowy top and enlightens the dimwit living below.

Thank you.

[JohnD]

There is a further factor that might be lifting you too high.

 Some time ago, someone was selling a batch of dampers as "For Triumph Herald/GT6/Vitesse".   In fact, they weren't as the spring seat was an inch or more too high.     I'm sorry, I can't tell you how high, above the trunnion, the seat should be - perhaps some online searching, here or elsewhere, will find it.

Good luck.

John

[Aristotle]

1 hour ago, JohnD said:

There is a further factor that might be lifting you too high.

 Some time ago, someone was selling a batch of dampers as "For Triumph Herald/GT6/Vitesse".   In fact, they weren't as the spring seat was an inch or more too high.     I'm sorry, I can't tell you how high, above the trunnion, the seat should be - perhaps some online searching, here or elsewhere, will find it.

Good luck.

John

John thank you,

"Some time ago" would need to be about 8/10 years ago as previous owner took the thing apart and rebuilt it about then - took him a couple of years.

He (allegedly) amongst other things rebuilt the suspension front and back and the general condition suggests whilst not "perfick" it's in fair nick.

He MOT'd it every year and mostly came out only in fair weather and the MOT record shows it as only having done 300 odd miles per year since, the front springs were renewed when it was rebuilt.

Looking at it in the round and as Mjit would have it for a "cheap assed 1970s British sports cars cobbled together from parts first designed for a cheap family saloon in the 1950s" it's a usable beast - but it's strange it's so high at the front.

My only thought is perhaps it was deliberate as the PO's drive fell away very sharply and I could imagine at the 4.4 inch standard ground clearance it may not have made it over the ridge - so to speak.

Thank you all again, I'm enjoying the fettling.

 

[Pete Lewis]

i will look up the fitted spring length  so you can do a simple tape measure check

but the manuals out in the conservatory and its cold and dark just now Ha !

Pete

[JohnD]

Aristotle,  that time scale is perfectly reasonable!

John

[Pete Lewis]

spitfire std spring fitted lengths

wsm shows two springs   209685  @ 198 +- 2.29mm

                                            210566  @ 188 +- 2.29mm

does not say what the two springs are from 

does say when using HD springs both side have packer 125441 fitted under the top plate    no idea why

im sure when club sold red  springs they were quite uprated 

on club shop they state springs are +20% and should be fitted to adjustable spring pan base shockers 

Pete

Edited September 29, 2023 by Pete Lewis

[Aristotle]

3 hours ago, Pete Lewis said:

spitfire std spring fitted lengths

wsm shows two springs   209685  @ 198 +- 2.29mm

                                            210566  @ 188 +- 2.29mm

does not say what the two springs are from 

does say when using HD springs both side have packer 125441 fitted under the top plate    no idea why

im sure when club sold red  springs they were quite uprated 

on club shop they state springs are +20% and should be fitted to adjustable spring pan base shockers 

Pete

Thank you, trust the trek into the conservatory was not too onerous - I always find that places where I keep "stuff" are dangerous to go into as family members usually find me out or in there hours later, body locked into crouched position - transfixed by some tome or other from times gone by. They usually bring me round with strong alcohol. Some say I do it on purpose. Will report back on my progress although it's not getting done soonest - at least now I have a plan of action. 

[Aristotle]

On 29/09/2023 at 09:29, Pete Lewis said:

spitfire std spring fitted lengths

wsm shows two springs   209685  @ 198 +- 2.29mm

                                            210566  @ 188 +- 2.29mm

does not say what the two springs are from 

does say when using HD springs both side have packer 125441 fitted under the top plate    no idea why

im sure when club sold red  springs they were quite uprated 

on club shop they state springs are +20% and should be fitted to adjustable spring pan base shockers 

Pete

Crept into the crypt (garage) where Spitfire resides after some days painting fascia ends on chez Aristotle and trying to solve a problem why the rev counter on boat had packed up - one looks good the other is still "packed up".

Approached front suspension with tape measure, torch and cloth dampened with WD40.

Wiped over bottom of shockers and legend S62-2290, 3-43 appeared on both sides. so I'll Google that when I get a mo.

More interesting is spring length both are approx 235 to 240mm - - - a bit more than Pete's measurements of "standard spring fitted lengths of 188 to 198mm.

So - let us say the standard fitted height is 188mm mine are a touch over 2 inches longer give or take an elderly gents wobbly hand.

Would that translate into a two inch higher riding height ?

Without taking stuff apart can't discern any packing plates it looks like just spring with no packing.

 With more fascia's to paint and boat to fettle for it's winter ashore this won't get done now till deep midwinter - so it looks like a set of adjustables or standard 188mm springs will be fitted.

Advice on my reasoning or opinions on fixed or adjustable gratefully accepted. 

[Pete Lewis]

so what you need is the dimension of the spring pan from the eye bolt  

who has that then ???

Pete

[JohnD]

Would that translate into a two inch higher riding height ?

not quite.   You need either Pythagoras, or trigonometry!  Because the spring is at an angle, it's extra length will cause less extra height.

[Aristotle]

3 hours ago, JohnD said:

it's extra length will cause less extra height.

Ermm, so if I read that correctly if I take off the the existing spring and (say I could) weld on another couple of inches to the spring making it longer the car would ride lower than it does now ?

If I read these things correctly and please understand I am a bear of very little brain - - as the top of the spring sits in a fixed point on the frame and the bottom locates in the lower wishbone which moves up and down with the motion of the car - - - wouldn't a shorter spring mean the bottom wishbone moves upwards - reducing the ride height ?

 

[Steve P]

If you make the spring longer then keep fixed spring plates shocks then it would be even higher, or you may have to compress it to get it to fit in the first place.

I would go for standard fitment springs if it was mine. Yours are obviously either for another model or meant to be used with adjustable spring plate shocks.

Steve.

[johny]

If you want to adjust ride height by much you really need shocks like this where as you can see theres adjustment for different length springs plus the bottom mounting also unscrews to change overall length. This means that what ever spring you use the damper can be kept in the right place (should sit about a 1/3 of the way down its travel so not to bottom out for the biggest bumps and rebounds) but still allow the vehicle to be raised or lowered. Doing anything else is a bodge...

 

Edited October 4, 2023 by johny

[Pete Lewis]

if you are only doing normal casual driving its probably (without checking) more economical to 

fit std springs and std shockers ,as adjustable are a pretty steep wallet emptier 

full kit from JP  £79 +vat etc.

what you need to find is this just the springs are tooooo long or the pans are in the wrong place ...or both

James Paddock Limited - Triumph Stag, Spitfire, TR6, TR7, GT6, Vitesse, Herald Parts and Spares Specialists. FRONT SHOCKS & SPRINGS KIT MK1V + 1500(GSA366K-2)

 

[JohnD]

20 hours ago, Aristotle said:

Ermm, so if I read that correctly if I take off the the existing spring and (say I could) weld on another couple of inches to the spring making it longer the car would ride lower than it does now ?

If I read these things correctly and please understand I am a bear of very little brain - - as the top of the spring sits in a fixed point on the frame and the bottom locates in the lower wishbone which moves up and down with the motion of the car - - - wouldn't a shorter spring mean the bottom wishbone moves upwards - reducing the ride height ?

 

No!   make the spring longer and the car will ride higher, but not as much as the spring was longer!

 Spring length = SQR[ Ride height^2 + Distance from the vertical of spring^2] - Pythagoras

 

OR Trig.  Tangent A = Ride height/spring length  Here's a table of the tangents of Angle A: Tangent Table Chart of all Angles from Zero Degree to 90 Degrees (basic-mathematics.com)

Good luck!

John

 

 

Edited October 4, 2023 by JohnD

[Mjit]

DOES the spring length actually change the ride height?

Surely the maximum distance between the spring top and bottom plates is fixed by the maximum extention of the damper, which is how an assembled spring/damper would be sat on the bench.  Fit them to a car and the weight of the car will compress the spring to a degree - but how much is more down to the spring rate than length isn't it?

Too early to think.