Leaf spring de-cambering

[Mike Bell]

I'm likely to need to de-camber some rear springs for the Gp1 car. Refuse to fit lowering blocks! The springs I have are tapered single leaf, so I guess easier to do than multi leaf ones?

Searching the 'net, looks like there is (or was) a forge in Islington that does such work, or is it something that can be done with a hydraulic press- or local blacksmith?

[GORDON STREETER]

We used to do them ourselves on the Hotrods years ago by removing them and either putting a bend just after the front eye or just leaving them under pressure for a time.
When the Escort Mexico Challenge was on years ago and were supposed to be standard I was involved with one of the cars that was left standing loaded up with about 4 ton of weights on the inside of the car/boot/engine bay for a month! and looking at the ride height of some of the other entrants we weren't alone

[grantp]

Originally Posted by GORDON STREETER

We used to do them ourselves on the Hotrods years ago by removing them and either putting a bend just after the front eye or just leaving them under pressure for a time.
When the Escort Mexico Challenge was on years ago and were supposed to be standard I was involved with one of the cars that was left standing loaded up with about 4 ton of weights on the inside of the car/boot/engine bay for a month! and looking at the ride height of some of the other entrants we weren't alone

The '68 Escort GT I owned back in the early 70 had rear springs that seemed to be inverted. But they were original.

Given that the car had never been a competition car of any kind I just assumed it was possible that one could buy rather soft versions of the standard springs. Possibly by accident of course. They were obviously available on the production line ...

[Mike Bell]

Not sure what happens if you invert a spring- if multi leaf surely the only leaf that will be left doing any work will be the main one? I suppose if they are clamped together the rest will be helping, but not in the intended fashion.

Putting a kink / dog leg at one end is possible, and have seen pics of RS2000 springs like that. Need to be careful though to keep axle nose in line with prop, and with it's non adjustable radius arms / tramp bars the RS axle will need springs to be level at centre to keep this correct.

It appears that new 'single leafs' for mk2 escorts are set at stage rally height, but I have a set of period ones that are much less cambered. I'm going to talk to the spring specialists if they are still about and see what's involved.

[GORDON STREETER]

We also used to angle the diff nose down from horizontal to help counteract axle tramp.
If it's horizontal (or angled up) the pinion tries to climb up the crown wheel and the spring pulls it back causing the "tramp".
Of course properly designed anti tramp bars are the way to go but if not they "fight" against the spring in the wrong way and can cause the car to handle worse.

[zefarelly]

Is there any theory behind radius arms/tramp bars?. The mk1 Tina ones are shorter than the axle/spring eye dimension so I've often wondered if they hinder rather than help . . .I've never run them, but can If I want as they're homologated.

It 'looks' like the rad arm of the U bolt plate to spring eye bolt should work better.

I have single leaf capri springs and I think they've just been flattened a bit. with a 1" block, they seem solid enough, after 10 years there's no wear to suggest movement.

[Mike Bell]

Originally Posted by zefarelly

Is there any theory behind radius arms/tramp bars?. The mk1 Tina ones are shorter than the axle/spring eye dimension so I've often wondered if they hinder rather than help . . .I've never run them, but can If I want as they're homologated.

It 'looks' like the rad arm of the U bolt plate to spring eye bolt should work better.

I have single leaf capri springs and I think they've just been flattened a bit. with a 1" block, they seem solid enough, after 10 years there's no wear to suggest movement.

Yes, tramp bars really need to have same dimension for pivot points! Ultimately I guess the spring twists to absorb the difference if not, with help from some compliance in bushes as well. Sounds like you have same springs as escort, but presumably narrowed to fit Cortina. It's the 'flattening bit' that I want to achieve. Have heard of some people just using a hydraulic press in middle while ends are held. May have a go while H&S aren't watching.....

[zefarelly]

the cortinas use capri 2.8i springs, they go straight on, everyone uses them.

part of the reason for never fitting tramp bars was if they're wrong they'd surely upset the feel more than not having any? my car doesn't hardly ever tramp, just spins up the wheels and goes sideways!

[Tel 911S]

Originally Posted by zefarelly

the cortinas use capri 2.8i springs, they go straight on, everyone uses them.

part of the reason for never fitting tramp bars was if they're wrong they'd surely upset the feel more than not having any? my car doesn't hardly ever tramp, just spins up the wheels and goes sideways!

You may not get tramp , but the torque will wind up the spring & stiffen it causing lack of grip . It will nearly always handle better & have more traction with the radius bars fitted .

As for the diff angle , have always found that fitting with the nose down gives best results . And the propshaft should not run in a straight line , but have an equal angle at each end [ from the box & onto the diff ].
Link to propshaft explanation /

http://www.hurst-drivelines.com/file...roc_111606.pdf

[zefarelly]

That makes sense.

prop angles not a problem as the cars effectively standard, I have some wedges to tiop the nose of the diff down a bit, I'll try them

I'm not keen on altering too much as I was quite happy with performance and reliability up until September!

BoT . . . . there is a company in London, old school place . . .Brost Forge, apparently they're very good Mike.

Brost Forge Ltd Repair, re-temper and reinforce leaf springs.
Telephone 020 7607 2311.

[Moosehead]

Obviously not close to you Mike, but I use 'Jones' Springs' in the West Midlands. They can either modify existing springs or make a set to suit, cambered, de-cambered, reverse eye etc. Reasonable prices and usually pretty quick turnaround.

[Mike Bell]

Brost and Jones are the two firms I had decided on, so thanks for confirmation, Guys!

[morninggents]

Originally Posted by GORDON STREETER

We also used to angle the diff nose down from horizontal to help counteract axle tramp.
If it's horizontal (or angled up) the pinion tries to climb up the crown wheel and the spring pulls it back causing the "tramp".

I'm fairly certain the early Lotus Cortinas had them as standard.Adout 10 cm long, same width as spring and tapering from about 9 or 10mm at the back to 2mm at the front.

[GORDON STREETER]

Originally Posted by Tel 911S

As for the diff angle , have always found that fitting with the nose down gives best results . And the propshaft should not run in a straight line , but have an equal angle at each end [ from the box & onto the diff ].

So we were right 45 years ago

[Tel 911S]

Originally Posted by GORDON STREETER

So we were right 45 years ago

There is no substitute for experience .

[Dave Brand]

Originally Posted by zefarelly

part of the reason for never fitting tramp bars was if they're wrong they'd surely upset the feel more than not having any? my car doesn't hardly ever tramp, just spins up the wheels and goes sideways!

A long, long time ago I had MK1 Cortina GTs. The earlier one, without tramp bars, suffered from horrendous axle tramp if you hit a bump while accelerating, but if you gave it plenty of welly exiting a sharp bend (not that I ever did that on the road!) the rear would slide out nicely! The later (Aeroflow) had tramp bars - no tramp, but no slides under power, either, as it would just lift the inside rear wheel which, with no LSD, meant no power to the wheels.

[zefarelly]

I tink I'd rather deal with a little tramp than lift a rear wheel!

[Mike Bell]

I think tramp bars work their best work in a straight line with car on an even keel. I'm not sure cars like the discussed Cortinas and Escorts have enough torque to really wind up the axle, but on bumpy roads they may have some benefit.

If their geometry is not in sync with the axle I reckon that they act like an anti roll bar, so when car rolls it is prone to lifting the inside rear wheel. A case of one mod leading to another- an LSD.....

[GORDON STREETER]

On my old Anglia I made up some anti tramp bars that I ran for the first 2 races of the season that seemed to work OK, however I was doing the Qualy for the next meeting at C Combe when one of the bars broke after a few laps and was hitting the ground so I had to pull in early.
I decided to remove them both and do the race without them and bingo the car handled much better and I won with the fastest lap.
So they are not always the way to go if not worked out properly.

[grantp]

Originally Posted by Mike Bell

Not sure what happens if you invert a spring- if multi leaf surely the only leaf that will be left doing any work will be the main one? I suppose if they are clamped together the rest will be helping, but not in the intended fashion.

What I meant Mike was that they looked like they were concave rather than convex. Or, at best, flat.

The previous owner, by his account, used the car to commute from his house on the outskirts of Guildford to the station and back. He worked in the City. Hardly got the engine warm I would think. Probably why a ring broke at around 40k miles.

Twice a year, being of French origin, he said he thrashed it to the South of France and back on holiday. Perhaps he took a lot of luggage? Given what it was I think "thrashed" may not have been so fast but may have involved some dodgy road surfaces back in the 60s.

[esper]

Originally Posted by zefarelly

I tink I'd rather deal with a little tramp than lift a rear wheel!

Do you give a second answer yourself : soft leafsprings and no trampbar?

[zefarelly]

If it aint broke . . .

they're a bolt on bit so I may just try them and remove when I don't like them . . . more dead weight to carry around anyway. Also, as MIke pointed out, little pushrod motors aren't renowned for snapping halfshafts!

BoT ( before John clips us round the ear) I've seen leaf springs bent at the front so they adopt an odd S shape , not sure why, mine are just flattened out, which, to my mind would suggest they'd be more progressive ?

[Dave Brand]

Originally Posted by Mike Bell

If their geometry is not in sync with the axle I reckon that they act like an anti roll bar, so when car rolls it is prone to lifting the inside rear wheel. A case of one mod leading to another- an LSD.....

I can't remember the exact set-up on the Cortina, but I'm pretty sure that they would be subjected to torsional loads under roll conditions, thus effectively increasing roll stiffness.

[zefarelly]

and back to MIkes original subject ( which I've hijacked) the Escort system is very similar.

this looks right, in theory ?

http://www.teamdeville.co.uk/img/big/100_1499.jpg

[terence]

As the (whisper it) MGB is allowed to use single leaf, were Escorts homologated too late for using a single leaf arrangement as were Capri, s etc?