ultimate tarmac suspension for 1303

[judgie]

going to be reworking the suspension on the 03 race ready for a proper attack on the hill climbs next year.
want to move awau from the anti roll bar doing the work of locating the tca. Also means i have quick eseay adjustment of castor and anti roll bar.
what i cant decide on is weather to go for a compresion strut or tension strut.
think with the heavy braking, hard cornering i would be better with a compresion strut but a tension strut would be eseay to mount.
I see the j-sports track car has a tension strut with seperate anti roll bar but thats a track car on nice smooth tarmac.
Allready running rose joints on the inner tca mount so the struts will be rose jointed through out.
Also want to make up new steering arms that have rose joints insted of ball joints, makes setting the ride hoight and bump steer very eseay then as you can space the outter ends up tih spacers to get the steering arms leval with the floor at ride hieght.
on the rear i want to get away from as many bushes as poss with out going to a uniball rear end, imho the rear suspension works very well with the torsion bars giving a nice rising rate but the rubber bushes allow to much flex with wide sticky rubber.
also want a adjustable rear anti roll bar which i thik will run over the top of the gearbox.
have thought about moving the rear shocks to on top of the trailering arm to give me a bit more ground clearnace over kerbs, have cought them before!
so any ideas or have i missed anything ?
cheers rob

[evilC]

Originally Posted by judgie

going to be reworking the suspension on the 03 race ready for a proper attack on the hill climbs next year.
want to move awau from the anti roll bar doing the work of locating the tca. Also means i have quick eseay adjustment of castor and anti roll bar.
what i cant decide on is weather to go for a compresion strut or tension strut.
think with the heavy braking, hard cornering i would be better with a compresion strut but a tension strut would be eseay to mount.
I see the j-sports track car has a tension strut with seperate anti roll bar but thats a track car on nice smooth tarmac.
Allready running rose joints on the inner tca mount so the struts will be rose jointed through out.
Also want to make up new steering arms that have rose joints insted of ball joints, makes setting the ride hoight and bump steer very eseay then as you can space the outter ends up tih spacers to get the steering arms leval with the floor at ride hieght.
on the rear i want to get away from as many bushes as poss with out going to a uniball rear end, imho the rear suspension works very well with the torsion bars giving a nice rising rate but the rubber bushes allow to much flex with wide sticky rubber.
also want a adjustable rear anti roll bar which i thik will run over the top of the gearbox.
have thought about moving the rear shocks to on top of the trailering arm to give me a bit more ground clearnace over kerbs, have cought them before!
so any ideas or have i missed anything ?
cheers rob

Hi Rob,
I have avocated a compression strut for the caster and TCA location for some time. My arguement is:
1) The AR bar set in bushes gives fixed caster and too much flex under braking and severe bump loads.
2) The anti-dive and pitch is limited when it is controlled at the front by the AR bar or tension strut.
3) The front of the frame head although stiff is not as stiff as the tunnel around the Nap hat.
4) With a vertically adjustable inner link on the Nap hat tunnel the anti-dive can be quite significant and it puts all the inner links up and out of the way of potential damage.

Rose joints throughout are a must to maximise control. You won't be worried about road vibrations into the frame will you?

Be careful about spacing the steering trackrod rose joints up too far as you start to put a bending moment into the fixing bolt. Also, you will need rose joints with a large tilting (setting) angle to cope with the large variations to be encountered.

Wally has I believe recently used a Porsche rear TB housing bearing that reduces the permissible flex to stiffen the rear.

The rear AR bar I have is only slightly adjustable with a rising rate (for the same reasons as the TB rate) and that is located under the gearbox. Where would you fix the AR bar if it were over the gearbox as there is no chassis?

The top fixing for the relocated dampers has the same problem as the AR bar insofar as there is little chassis to fix to. Unless you use the same mount and shorten the dampers. What about locating the bottom mount behind the axle to increase the stroke and thus slow the required response time? I have always found that the high frequency damper response falls off much quicker that the slow frequency response.

Just an tanner's worth

Clive

[judgie]

my thoughts excatly on the front end, a compersion strut just seems to make more sense.
on the rear i'm going to be putting a new cage in over the winter which will tie in the frame horns to the cage. wouldn't take much to put mounts for the anti roll bar onto the rear stays. would like to keep everthing above the frame horns for clearance as i want to fit a flat floor/sump gaurd with a working defusser.
also been thinking about replaceing the floor pans so i can get the floor flat ie; no lowered section for the seats. if i can work it so i can have a compleatly flat floor from the splitter to the rear defusser it can only help.

[evilC]

Putting a flat floor in should not cause too many difficulties as you don't need the rear passenger footwells. You might have to consider some stiffening on the topside because it will flex and drum.
How do you get a diffuser to work at the rear with a flat four engine?

Clive

[judgie]

rear defusser is going to be a tricky one and is the reason i'm going to be running a rear bumper on the car next year. hopefully i can use the extra space that the bumper will give me to allow a small upswept tail to the flat floor. think i will make the floors from alloy sheet as nothing is mounted to the floors now. the seat is on tubes from the tunnel to heater channels and the peddal box is going on some bars from the tunnel to heater channels when i swap it to a bias box.
looking at the exige i have in the work shop the rear defusser only rises by about 25mm towards the rear, i should be able to get more than that.
any way back to the suspension. on the rear i waws thnking about putting the shocks on the rearmost part of the trailing arm and fabing some mounts up from the cage rear brace. that way the shock is as close to the wheel as poss, will also allow me to use a shorter shock which will be lighter[ offsetting the wieght from the mounts but more importanly reducing sprung wieght] still not worked out how to do the rear anti roll bar yet.