Dunlop CG 4/5 castor camber king pin gauge kit.

[CooperTune]

After years of looking for this kit I was able to find a complete kit that has never been used and is complete. I had found the Dunlop toe gauge and a set of turn tables years ago. The new kit is a pleasure to use and is a fine addition to my tool collection. I was surprised to find setting both tie rods to the same length can give very different castor reading on either side of car.

I have read about Miglia racers using very high castor numbers 6/7 degrees. I think std is around 3/4 degrees. I understand that castor has to do with self straightening. Can anyone tell me how the increase improves handling in race cars?

As long as I'm asking, I'm setting up a Sport Pac with 6X12 wheels with 165/12 tires. Currently using 3/4 degree negative camber front 1/2 degree neg. rear camber. Zero toe rear 5 minutes out front and 3.5 degrees castor. This is a street driven car that gets some fast street use a couple of times a year at the Dragon.

I realize MK 1 s did not have 12s Steve (CTR)

[rich@minispares.com]

the c/g kit is a think of beauty and is still very highly prised by racers as it does such a good job of setting the cars up

miglias use a high castor setting as it means that the steering becomes more heavy and less nervous, this is an advantage due to them running an open diff and a lot of power on the tyres they use.

its not too hard heaving one around for twenty minute, particularly when you are not really giving the car much steering input - unless your doing something wrong you wont be turning the wheel much more than a quarter of a turn of lock either way

a road car would be horrific with that much

[Spider]

By dialing in more Cater Angle you can dial in less Camber but get the same advantage while corning with less disadvantage.

With Caster, as the wheels steer, the Outside Wheel will go Negative in Camber Angle, and the Inside Wheel Positive. Have high Negative Camber dialed in means that (in a straight ahead position), you've got less braking / acceleration grip, though with the unequal lengths of the arms, these angles change but big amounts in any case, but at a static zero to -0.5 deg you'll get the best tyre contact under brakes and also under the go pedal.

The steering will get heavier of course and you also need to check clearance between the wheel arch and the tyre when dialing in more Caster.

Your mention of setting the rack ends to the same length will also set the bump-steer the same on both sides but it can't affect the caster. This actually shows a short coming with 99.99% of wheel alignment tools that they measure camber at two steering angles and then it's calculated, rather than being a true direct Caster Measurement, none the less, the Dunlop Gauges are a good simple, fast easy to use bit of kit. I had one with the Race Car and I've been kicking myself since for selling it with the car.

[dutchacme]

By David Vizards adagium, don’t try to make the rear stick less try to make the front stick more. If you turn your steering wheel you will notice that the out-side side wheel will go up and the inside wheel will go down. Increasing castor will make that the inside will go up higher and the outside go lower. Approaching maximum cornering (>1.1G for CR65’s) the outside wheel will get so much weight transfer that it cannot return proportionally more lateral force. With more castor the outside wheel will reach this moment that the lateral force goes into the force plateau later. While the inside wheel as you wish will push harder on the ground and provide a bit more lateral force.
With weight scales or a weight jack you can see how much difference this makes, measure the weights with the wheels straight ahead and measure it with the steering wheel half a turn.
Castor should be seen in connection with the king pin inclination. From a point of preventing premature weight transfer in cornering, more king pin inclination is also be beneficial. All these aluminium hubs on winning historic Mini racing cars….

[Spider]

By David Vizards adagium, don’t try to make the rear stick less try to make the front stick more. If you turn your steering wheel you will notice that the out-side side wheel will go up and the inside wheel will go down. Increasing castor will make that the inside will go up higher and the outside go lower. Approaching maximum cornering (>1.1G for CR65’s) the outside wheel will get so much weight transfer that it cannot return proportionally more lateral force. With more castor the outside wheel will reach this moment that the lateral force goes into the force plateau later. While the inside wheel as you wish will push harder on the ground and provide a bit more lateral force.
With weight scales or a weight jack you can see how much difference this makes, measure the weights with the wheels straight ahead and measure it with the steering wheel half a turn.
Castor should be seen in connection with the king pin inclination. From a point of preventing premature weight transfer in cornering, more king pin inclination is also be beneficial. All these aluminium hubs on winning historic Mini racing cars….

[dutchacme]

Spider, much appreciated.

Forgot to mention, with hydro arms and the stiffer rubber doughnuts up-front the increased castor benefits will be even more noticeable. This is a tricky mechanism, normally stiffer springs will create more weight transfer, which is not wanted, however the lift of the outside wheel and the pushing down of the inside will just outpace the increased weight transfer due to the increased stiffness.

Wim

[LuisM]

Interesting inputs!
Now i understand why some appendix k racers seem to run 7 degrees castor!

Cheers, Luis

[CooperTune]

I am loving this thing it is quick and easy to use. I have not wanted to give up the space to build a set up rack. A couple of 2"X 16" staging boards 12' long leveled roughly a foot off the floor. When done I should be able to roll forward onto turn tables and back onto electronic scales. I have already had 5/8" thick aluminium disc machined and drilled which I use as set up wheels. Looking forward to making all minis I work on drive and handle better. Steve (CTR)

[CooperTune]

I'm now able to do a castor check on every car I work on. So far none checked were within 2 degrees on either side. Funny part is every one checked so far have had adjustable tie rods / strut rods. I have always felt adjustable suspension was a chance to get it wrong with out the proper tools and the knowledge to use them. Steve (CTR)

[rich@minispares.com]

I'm now able to do a castor check on every car I work on. So far none checked were within 2 degrees on either side. Funny part is every one checked so far have had adjustable tie rods / strut rods. I have always felt adjustable suspension was a chance to get it wrong with out the proper tools and the knowledge to use them. Steve (CTR)

ive set loads of cars up, and they are very rarely correct, the biggest discrepancy I have seen on a car (set up by a mini 'expert') was a variance of 6 degrees side to side.....

unfortunately most people only see adjustable tie bars as a means to move the wheels back in the arches to stop the tyres rubbing on the bodywork, with no consideration given to the effect on the handling.


mind you


the last car I set up (a monster turbo powered car) had slack bottom arms (the adjust nuts had come loose on the bottom arms!) and the fat washers where missing from the ends of the tie bars, so the nuts had been pulling through the thin cupped washers - another couple of weeks I think they would have pulled right the way through!

[ivor badger 2]

I'm now able to do a castor check on every car I work on. So far none checked were within 2 degrees on either side. Funny part is every one checked so far have had adjustable tie rods / strut rods. I have always felt adjustable suspension was a chance to get it wrong with out the proper tools and the knowledge to use them. Steve (CTR)

Colin Chapman was once dug up about the lack of adjustable suspension on racing cars he sold. " Of course we don't make it adjustable, have you seen the mess people can make of Webers with a screwdriver."

[andy1071]

By David Vizards adagium, don’t try to make the rear stick less try to make the front stick more. If you turn your steering wheel you will notice that the out-side side wheel will go up and the inside wheel will go down. Increasing castor will make that the inside will go up higher and the outside go lower. Approaching maximum cornering (>1.1G for CR65’s) the outside wheel will get so much weight transfer that it cannot return proportionally more lateral force. With more castor the outside wheel will reach this moment that the lateral force goes into the force plateau later. While the inside wheel as you wish will push harder on the ground and provide a bit more lateral force.
With weight scales or a weight jack you can see how much difference this makes, measure the weights with the wheels straight ahead and measure it with the steering wheel half a turn.
Castor should be seen in connection with the king pin inclination. From a point of preventing premature weight transfer in cornering, more king pin inclination is also be beneficial. All these aluminium hubs on winning historic Mini racing cars….

Increasing the castor angle will lift the outside wheel more, and lower the inside wheel more.
This will tend to increase the roll angle (all other things being equal).
It will also affect the understeer/oversteer balance.

Lateral weight transfer is more a function of roll centre height and centre of gravity height ("roll couple" / "roll moment").

Minis are known for bump steer. Maybe one of the effects of increased castor is to lower the track-rod end.
-I haven't put the Mini suspension geometry into any suspension analysis software, so I can't confirm this.

I would think that the increase in castor has more effect on the tyre behaviour, so I would think this is the main reason for increasing it.