Lowering car

[David Kemp]

Though I am a long way from it, I would like advice on lowering my Jupiter, if for nothing else sheer good looks.
What is the trade off if I simply adjust the torsion bars an inch or two lower than standard?

[Keith Clements]

Any alteration of ride height will alter the steering geometry and affect cornering.
Simply unloading the front torsion bars will cause the car to bottom on bumps. The tracking toe in will also be affected.
Lowering the rear requires mods to the torsion bars or extensive mods to mounting points like Richard Gane has done on the race car.
The easiest way to get the lower look is to fit 15 inch wheels but I did this for racing to lower the Centre of Gravity and so I could fit cheaper tyres. Even that requires careful design of the wheel offset or use of spacers to keep the contact patch in the centre of the tyre.
If you just want the car to look that way then fill it with sand☺

If you do lower the car then you should fit a sump guard if you plan to take it on anything other than a flat road. I did have plans when racing and rallying to cover the underside with ally sheet to reduce drag (but not get ground effect!) and keep all the stones from damaging the underside. On one forest stage the underside was beautifully shiny all over after the stone chips blasted the paint.

You should also uprate the shock absorbers or fit adjustable ones or fit stiffer springs. One way around this (as fitted to the Auckland Mead Jup) is to have adjustable gas assisted spring dampers , similar to what is used when towing caravans. Various people have replaced the rubber bump stops to perform a similar function. Whether you could get away with lowering the car by an 1/8th of a turn on the torsion bar is another matter. Shame they changed from the splined bar that was fitted to the prototype!
The works experimental Javelin had different drums fitted to take 15 inch wheels (may have been done later in its life though) so that may have been the next change planned for production.

[David Kemp]

Thanks, I think I will stick to stock height. With risk of repeating another subject, how did you make the 15" wheels?

[Keith Clements]

I used some wheels off a SAAB (90 I think) . The steel on these was three times as thick as the Jowett which shows why Jowett wheels crack so readily. They are also 5 stud but of a different pitch. I made a jig to drill them to the Jowett pitch circle and then welded around these holes to add strength. I fitted studs from Land Rover into the drums as these were twice as strong as the Jowett ones which often stretch. They are also twice as long allowing the fitting of spacers to get the contact patch correct.
Overdrive or higher diff ratio is necessary, unless you are just hill climbing.

[AmilcarJohn]

I think most people using 15" wheels have welded Javelin centres into other rims (SAAB, Volvo, VW or whatever). Mine actually use stronger JCC centres with SAAB rims.

Another (better) way to go is to have alloy wheels made to look like Jupiter wheels -I think that they are circa £300 a corner, so quite an investment. That way you get the strength without the excess weight.

[David Kemp]

Thank you, I will be looking at alloy wheels some time down the track, I have been warned they are not cheap. Some times I think it would be easier to change the stud pattern, the back axle would not be hard, it.s the front that would pose a problem . & that is just keeping the face distance the same from the king pin centreline.

[Keith Clements]

Alloy drums can be put on Jowett centres/bearing housing / taper so you could have whatever stud pattern you wanted.

[David Kemp]

Where would you get alloy drums from?

[Keith Clements]

I do not know how many were made. Julian Crossley was getting them done. He had a firm do the design.