Lotus 69 FF: Recommendations for Suspension Setup

[halcyon]

I am working on getting a Lotus 69 FF ready for vintage racing. The car hasn’t been raced in many years, and I don’t have any setup info for the car. The car has it’s original dampers from the 70’s, so those will need to be replaced. Any recommendations on where to start with spring rates, ride heights, shock selection/design would be appreciated.

[marty7]

Set up will depend on what tyre you are running. I run the Avon ACB9. With this in mind - tyre pressures 18 PSI hot.

Castor, front is factory - wishbones set up parallel to chassis center line. Rear castor - I adjust radius rods till zero rear bump steer - what ever castor results is what I run.

Camber - 3/4 to 1 degree in at the front. 1/3 to 1/2 degree in at the rear.

Toe - 3mm toe out front per side, 1.5mm tow in at the rear. Ride height - around 50mm front and 1/2" rake. I do run more toe out at the front but most disagree, however the car goes around corners. NZ circuits have medium length straights with a lot of hairpins and high speed corners. Car is a front runner - I can put it on pole and get a win.

Dampers - I have had non adjustable Bilstien inserts fitted into the Armstrong damper bodies. Sorry I can't tell you rate or valving. I had the armstrongs dynoed and used that as a starting point for the Bilstein inserts.

Springs, 300Lb front, 20Lb rear. My car has slight tendency to oversteer on this set up. It can be tuned on the bars.

Steering - these cars ran a modified Ford Escort Rack. I have fitted the highest ratio rack and pinion so the car is catchable at speed if it starts to spin.

Bars are factory - front end is droop limited - not zero about 1/2 - 3/4 " droop at the front. Wind out all rod ends on the wishbones - I run about 1/2 inch of thread engagement - wide track the car as much as you can. As a result of this I had new driveshafts made to accommodate the additional rear track. From memory my drive shafts are about 3/4" longer than standard. And bump steer the front. Check rod ends and bearings aren't binding or worn. Slim brake discs to around 7 to 8mm.

Check bias bar is working - fit a remote adjuster. Once set up is done corner weight. Get front right , you can get away with a difference at the back. Do all set up at race weight.

[Jayeff]

Set up will depend on what tyre you are running. I run the Avon ACB9. With this in mind - tyre pressures 18 PSI hot.

Castor, front is factory - wishbones set up parallel to chassis center line. Rear castor - I adjust radius rods till zero rear bump steer - what ever castor results is what I run.

Camber - 3/4 to 1 degree in at the front. 1/3 to 1/2 degree in at the rear.

Toe - 3mm toe out front per side, 1.5mm tow in at the rear. Ride height - around 50mm front and 1/2" rake. I do run more toe out at the front but most disagree, however the car goes around corners. NZ circuits have medium length straights with a lot of hairpins and high speed corners. Car is a front runner - I can put it on pole and get a win.

Dampers - I have had non adjustable Bilstien inserts fitted into the Armstrong damper bodies. Sorry I can't tell you rate or valving. I had the armstrongs dynoed and used that as a starting point for the Bilstein inserts.

Springs, 300Lb front, 20Lb rear. My car has slight tendency to oversteer on this set up. It can be tuned on the bars.

Steering - these cars ran a modified Ford Escort Rack. I have fitted the highest ratio rack and pinion so the car is catchable at speed if it starts to spin.

Bars are factory - front end is droop limited - not zero about 1/2 - 3/4 " droop at the front. Wind out all rod ends on the wishbones - I run about 1/2 inch of thread engagement - wide track the car as much as you can. As a result of this I had new driveshafts made to accommodate the additional rear track. From memory my drive shafts are about 3/4" longer than standard. And bump steer the front. Check rod ends and bearings aren't binding or worn. Slim brake discs to around 7 to 8mm.

Check bias bar is working - fit a remote adjuster. Once set up is done corner weight. Get front right , you can get away with a difference at the back. Do all set up at race weight.

I don't think the ACB 9 tire is legal here in the US. I run the A 29, which I believe is a harder tire. Looking at your set up, I'm sure that car turns in very well. I think most people here use much higher spring rates.

Cheers,

[DanW]

I don't think the ACB 9 tire is legal here in the US. I run the A 29, which I believe is a harder tire. Looking at your set up, I'm sure that car turns in very well. I think most people here use much higher spring rates.

Cheers,

Ummm, I think the ACB9 is the tire model. There are two ACB9 compounds, A25 (marked FF) and A29. Vintage organizations specify the compound they want used. Some vintage groups require Hoosier FF treads.

[marty7]

Avon ACB9 is a reproduction of the Dunlop CR FF tyre. The Hoosier VFF is similar . I have run the Dunlop CR, Avon ACB10 and currently the ACB9. We run the harder A29 compound.

Yes in the USA many drivers run firmer springs. This may be a hang over from the days of running slicks. Logic to me says if in NZ, Australia and the UK we all run the same ACB9 tyres and we are all generally running simiar spring rates then logic would say in the East Coast USA you should be similar. I can not see that USA circuit demand higher spring rates.

I was at Montery for the 50th and Road America for the 50th spectating. West coast was running the Avon ACB9, West Coast the Hoosier VFF. I do have strong opinions on set up and race car prep. Walking around the pits a number of cars were set up wrong for those tyres at both events. Cars had been modified with 'go fast' ideas which to be honest left me shaking my head. Especially the Van Diemens. The firmer you go in springs the less compliant the car will be. It will not be as communicative. A softer car will be more forgiving. Most of us are weekend warriors. We don't get enough seat time to have some rigid set up. A forgiving predictable car wil be a quick car at our level. The Lotus 69 was originally around 225 front, 180 rear.

Soft is still quick - all you want are springs that don't allow the car to bottom under braking etc.

Make the car nice to run, then go from there.

I don't think the ACB 9 tire is legal here in the US. I run the A 29, which I believe is a harder tire. Looking at your set up, I'm sure that car turns in very well. I think most people here use much higher spring rates.

Cheers,

[halcyon]

There are some good starting points here. I appreciate the input.