Suspension Settings

[graves]

With limited equipment, ie no optical gauges etc how does one measure and then set caster and toe angles. I have rebuilt my Rover cooper and took part in my first sprint last october at a VERY wet Lyydon. I am entered for a sprint at Brands in a couple of weeks and am keen to dial out some of the strange handling characteristics i was experienceing with the newly put together car!!

[tim williams]

Without proper gauges its damn difficult to do.

For a nit of an idea get some string and tie it round the car so that it goes round all 4 wheels that will give you an idea if things arent pointing in the right direction.

i.e. the string should touch the front and back of the wheels, if it doesn't then something isn't aligned quite right.

but its very very worth while getting a pro to set ip up.

[selbymsport]

what strange handling?
Questions : tyres used and presures? damper type/make, roll cage type, ie bolt or weld in, anti roll bar fitted? suspension joints- rubber/plastic or spherical?

[miniman]

There's a handy home setup tip from Cooperman in this thread

He also wrote a great handling article which is on my site here

HTH

[graves]

Thanks for the info, and the thread. I shall try the 1meter Angle on each wheel trick to set the toe. I beleive 0deg is recommended up front. As for caster, i have managed to source an electronic inclinometer, i was thinking of using two equal length peices of flat bar bolted to the top and botton wishbone points on the upright. With the bars facing towards the front of the car i can put the inclinometer accross the two ends. The angular diference between the ends of the bar will be my caster?? Very hard to explain with text!!

Perculiar handling can be defined by:
1. Massive understeer - very wet, maybe front set too hard?
2. Does not track in a traight line - Tracking out, or crabbing?
3. Turns better one direction than the other - Caster different for each wheel?

Thanks again

[Cooperman]

miniman said:

There's a handy home setup tip from Cooperman in this thread He also wrote a great handling article which is on my site here HTH

Thanks for the reference James.

Almost always you'll find strange handling on a re-built Mini is caused by the rear suspension not being set up correctly. The rear end MUST toe in by betweem 3/16" AND 1/8" and must have zero to slight negative camber. Set this up before looking at the front settings (as James says, I think I covered it in the article I did for him.
The castor angles on the front should be 3 degrees, but to set this needs a castor gauge and I always go to my local friendly tyre shop who happen to have one. One of the problems with this setting is the tolerances on the body and front sub-frame. For example, on my 1964 rally car to get the wheels in the same position relative to each side, one castor is 2.75 degrees and the other is 3.1 degrees. It doesn't seem to matter too much in handling terms and of more importance is the zero toe-in on the front wheels.
Of course, ride height and damper settings are important. Always remember that if you stiffen up one end, you increase the roadholding at the other end (that's a bit simplistic, but the principle applies).
The other think to check is that the front and rear wheels are in line. If they are not you adjust this by shimming or grinding away the rear radius arm brackets. Don't forget, however, the track on the rear is narrower than the front track.
I hope all this helps. Come back to me if you need any more info. as there are lots of other small things which need to be right, like tyre pressures, front camber, etc.

Peter

[graves]

selbymsport said:

what strange handling? Questions : tyres used and presures? damper type/make, roll cage type, ie bolt or weld in, anti roll bar fitted? suspension joints- rubber/plastic or spherical?

Tires are Yokos 5?? (road tires), i ran with 30psi all round, dampers are spax on back with koni up frt, how do you adjust Koni??, Roll cage is bolt in SD with welded in frt legs at floor with door bars. No anti roll bars. All suspension joints are uprated bush, subframes are solid mounted. Adj camber rr swing arms, 1.5 deg frt lwr arm and adj tie rod.

[graves]

Cooperman said:

The rear end MUST toe in by betweem 3/16" AND 1/8" Peter

Peter, thanks for the info, you quote a length not an angle for Rr toe, where is this measurement taken from? Schoolboy stuff i know!!

[Cooperman]

[redacted]

[selbymsport]

graves said:

selbymsport said: what strange handling? Questions : tyres used and presures? damper type/make, roll cage type, ie bolt or weld in, anti roll bar fitted? suspension joints- rubber/plastic or spherical? Tires are Yokos 5?? (road tires), i ran with 30psi all round, dampers are spax on back with koni up frt, how do you adjust Koni??, Roll cage is bolt in SD with welded in frt legs at floor with door bars. No anti roll bars. All suspension joints are uprated bush, subframes are solid mounted. Adj camber rr swing arms, 1.5 deg frt lwr arm and adj tie rod.

Are you driving the car to the sprints or transporting it? If you are transporting it you can afford to be a bit more adventurous with the settings. The target is oversteer when lifting off the throttle with as near to neutral drift when the throttle is squeezed again. To start with set the ride height, low as possible without interference of the body. Once you have set the ride height you can start to adjust the geometry, you can set the caster by using the caster gain method, i.e. turn steering wheel one turn and measure camber then one turn in other direction and add, x the result by 1.4 and this will give you your caster angle (or very near) set this to 6 degrees to start with. You will probably have to shorten your tie bars. As you lower the car your negative camber will increase. If your bottom arms are fixed 1.5 at std ride height you will probably find a small increase, this is a plus. Font tracking set to zero to 20 minutes inclusive out.
The rear camber set to 1.5 to 1.7 degress negative and the tracking to toe OUT 30 minutes (1/2 degree). Also I would try using higher tyre pressure. The rear Konis may be adjusted by pushing out the rubber bump stop using the two small hole in the top of the damper, the fully closing the damper and turning the rod to feel it locate in a drive slot from the extra travel you have given it by removing the bump stop, clock wise increases stiffness. This is basic starting point, but you must set up on a flat floor. Anything you measure will be coming from the Datum which is the ground your car is sitting on. I hope this info is of help to you
Regards selbymsport

[selbymsport]

I've just realised that Peter has advised you to run toe in at the rear, this conflicts with my advice and will be confusing you. With due respect to Peter toe in is Ok for a rally car but for tarmac use it will just cause understeer. On our circuit car we use up to 1.5 degrees toe out to induce rear end steer when off the throttle and when at full power through the turn the car will be three wheeling ie rear inside wheel off the ground. A circiut like Thruxton or Castle Combe requires more to out than most as there are no straights so the rear inside wheel is doing very little work. Without a rear anti roll bar the reaction of throttle off oversteer will be gentle not the immediate reaction we like on circuit so is ok for a novice.

[jellison]

Just had 1.5 Wood Pickett 1.5 deg camber kit fitted to the front and real of Cooper (S) can anyone tell me what the tie bars should be set for with respect to tow in?

[graves]

[quote=selbymsport]
Are you driving the car to the sprints or transporting it?

you can set the caster by using the caster gain method, i.e. turn steering wheel one turn and measure camber then one turn in other direction and add, x the result by 1.4 and this will give you your caster angle (or very near) set this to 6 degrees to start with. You will probably have to shorten your tie bars. [quote=selbymsport]

Thankyou very much for the reply, it makes very interesting reading. I shall be trailering the car to events, predominantly for financial reasons, i dont insure, tax or mot the car. The handling characteristics you describe sound good for the type of use the car will have, i will install the setup you describe. I am very interested in the Camber Gain technique you describe, to reiterate

1. Start with car on flat ground with wheels pointing directly forward.
2. Turn steering wheel 360deg in one direction.
3. Measure Camber
4. Return to straight ahead.
5.Turn steering wheel 360 deg in other direction
6. Measure camber
7. Add two camber values together and multiply by 1.4
8. Caster value!!

[selbymsport]

Spot on Graves, good luck on your next outing hope you find the new setup an improvement