The discussion on spring rate got me thinking about the whole front suspension -- isn't the geometry all wrong? The roll centre is basically at the same height as the rear and the tie bar geometry is good for anti-squat but not for anti-dive.
Would a system that turns the bottom arm round so the tie bar is a compression strut and mounted the pivot point lower to lower the roll centre be better? -- a bit like the Metro/MGF? Anyone any ideas how feasible this is -- many years ago an obscure car mag built a grass track Mini with the bottom arm mounted in a bit of box section welded under the bottom edge of the subframe which wasn't very elegant and probably gets into the ground clearance. Any of you F1 chaps go any ideas?

I've seen a Mini 7 racer (I think) with the front tie bar mount lowered on a piece of box section to produce some anti-dive.

I also remember a kit car which used the tie bar in compression rather than tension. The name McIntyre or Macintosh rings a bell but I can't be sure.

Using the same subframe front and rear will give roll centres at roughly the same heights depending on how you set the ride heights and wishbone angles but because the centres of gravity will be at different heights there will be different roll moments front and rear. I'm not sure what the overall effect on the handling will be.

It was the Macintosh M1 http://www.westhouse.plus.com/m1.htm

Deleted as this will only confuse my new post

I think that the Macintosh had unique double A-arm front suspension so I assume it was designed to optimise geometry.
An alternative approach was the Nimbus which used a Vauxhall front suspension subframe with a compression strut -- Chevette?? -- but the front track ended up significantly wider than the rear.
I think squat and dive are worked out by projecting the arm mountings in side view forwards/back to a vertical dropped from the C of G with the distance of the intersect below the C of G height representing the % squat or dive -- on this basis the front end has -- for want of a better phrase -- diddly squat anti-dive.
I'd never realised the subframes were at different angles -- I thought they were mounted with the bottom edge parallel to the road assuming the car sits level. Also I appreciate that lowering the front roll centre increases the front roll couple and may require an anti-roll bar to control -- perhaps part of West's roll bar calcs promised somewhere on another thread.
Must search out Staniforths Suspension book for another read.

yup projecting the axis of rotation in side view is the way to do it and I have, the descrepancies come from when the car is using a live axle or independant suspension as to where the virtual swing arm is drawn on the driven wheels and , one is from the centerline of the wheel the other from the contact patch.

not all books share this information, staniforths book altho good and describes it in plan english doesnt really talk much about anti squat/dive

I have done some calcs recently using my predicited new spring rates from going coil over and for myself a front roll bar would apear to be benficial to get the front tires working more and hopefullly increase the grip. Also interestingly it then means the weight from the front unloaded tire is then applied to the rear making them more even and hopefully aid in traction out the corners

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My next to last post edited to read correct values after recalculating

From my calcs, rear RC on my car was 2.9 inches and fairly well controlled only going alittle ary when in droop and roll, front is yet to be re-claculated.
In terms of anti squat/dive, the front and rear subframes on a coupe are mounted at vastly different angles, I have re read my souces on anti squat and it makes alot more sense now, For my particular rideheight /tyre combination My coupe has 2% anti-squat on the rear, and my rough drawin gof the front show a tiny bit of anti dive, values are irrelavant till a more acurate drawing/measurements done

My new rear suspension intially had no antisquat, but I have had a play this weekend with both my RC programe and Side profile drawing and have now incorperated a little anti squat, Anti squat does compromise geometry, but kept to small amounts the effects can be made negliable which is what I hope to achieve



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So -- does the difference in alignment of the subframes make a significant difference to the roll axis front to rear allowing for the ride height diffences and ....... can you feel the effect of 2% squat?
I supppose what I'm really getting at is whether its worth going with the "theory" and messing around with the front suspension geometry or staying with the geometry set by the standard subframes and tuning via srping damper rates plus perhaps a front anti-roll bar?
Any thoughts?

          and lost    There are far too many smart people on here!     

^^^ ^^^




Its the height of the pickup points relative to teh axle line that are used to determine your roll axis, the effect of the angle is a bit hard to explain in words prehaps a drawing is needed to help,


Well achieving anti squat from IRS [Indpendant rear suspension] is quite difficult, as the toque reaction mainly goes through the engine/gearbox/chassis on the GTM, certainly my car does not squat alot when drag racing so the 2% anti squat must be helping a little the new setup has got a little more than that



Im thinking on mine an antiroll bar may be quite benificial, making the front tires work more and will help stop unloading the rear tires and meaning I can get more traction.

As if by magic......


http://www.16vminiclub.com/forums/viewtopic.php?t=16068

Th guy that's selling that anti roll bar states that he's installed a k series in a Mini in a narrowed Metro frame -- how does that work?

i have only just relised something very important.


Steve you talking about the geometry on a libra!, as im talking coupe in regards to subframe mounting angles. but still the talk of finding % of antisquat etc is the same its just my numbers are for a coupe obviously

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On this thread I'm talking Coupe -- look at my gallery piccy and you'll see I'm one of the lucky ones who has both a Coupe and a Libra -- the 2 with the very similar reg numbers thanks to my friendly local DVLA office in Chelmsford.

Ah yes i remember the pic now

Ill try and draw some pics to explain things when i have a free moment and looking for something to do will help explain a anti squat etc

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