live axle handling ?
Discussion
Of late I have been driving a bit faster and I've noticed that on fast curves, the rear end seems to lose its stability after the suspension has settled. Its almost like the geometry changes quite dramatically when the suspension is compressed. Just when you need the confidence in the middle of a fast sweeper, she gives me a little squirm and the car moves around a bit.
Is this just the nature of a live axle versus an independent suspension? I wonder is the inside wheel "toeing in" under compression?
I'm new to Caterhams and find it just a bit unnerving. The "A" arm bushing is fine.
Should I firm up the rear shock settings a bit?
Is this just the nature of a live axle versus an independent suspension? I wonder is the inside wheel "toeing in" under compression?
I'm new to Caterhams and find it just a bit unnerving. The "A" arm bushing is fine.
Should I firm up the rear shock settings a bit?
Because the entire rear axle is basically a hollow, rigid tube with a wheel at each end, the rear axle geometry is fixed. The toe and camber can't change.
If the bushes are fine (in the 'A' frame, radius arms and damper eyelets) then I'd look elsewhere. What tyre pressures are you using? Do you have bilstein or spax shock absorbers? Is the chassis 15mm higher at the rear than at the front?
I'll also add that live axle cars are renowned for hopping and skipping over bumps slightly and it is a thing you get used to (even exploit)
If the bushes are fine (in the 'A' frame, radius arms and damper eyelets) then I'd look elsewhere. What tyre pressures are you using? Do you have bilstein or spax shock absorbers? Is the chassis 15mm higher at the rear than at the front?
I'll also add that live axle cars are renowned for hopping and skipping over bumps slightly and it is a thing you get used to (even exploit)
Twobone,
One particular issue to caterham/lotus sevens is due to the lower damper mount be in the wrong orientation. IE the bottom eye/bolt is inline with the axle tube. What this does is as the axle goes into roll the small amount of movement in the rubber lower bush is used up, if the car continues to roll the now non compliant bush puts a bending force into the damper rod/body. This will cause severe internal friction in the damper causing the damper to effectively go solid in bump damping. What this does on the road is the car will roll/settle into a steady state on a smooth road but if any further roll or bump is encountered the axle will be severely effected.
The way around this is to use a damper with a spherical joint in the lower eye allowing free movement in roll.
Cheers
Chris
One particular issue to caterham/lotus sevens is due to the lower damper mount be in the wrong orientation. IE the bottom eye/bolt is inline with the axle tube. What this does is as the axle goes into roll the small amount of movement in the rubber lower bush is used up, if the car continues to roll the now non compliant bush puts a bending force into the damper rod/body. This will cause severe internal friction in the damper causing the damper to effectively go solid in bump damping. What this does on the road is the car will roll/settle into a steady state on a smooth road but if any further roll or bump is encountered the axle will be severely effected.
The way around this is to use a damper with a spherical joint in the lower eye allowing free movement in roll.
Cheers
Chris
only as an idea...as i dont own a caterham:
i recently cmae across driving a seven (non caterham) with live axle.
it tends to oversteer dramatically, even those seven type is not prone to do this.
it turned out that the front suspension was set wrong:
the initial load of the front coilovers was set too much.
reduced the load, by lowering the coil-platform and here we go....the oversteer was reduced.
i recently cmae across driving a seven (non caterham) with live axle.
it tends to oversteer dramatically, even those seven type is not prone to do this.
it turned out that the front suspension was set wrong:
the initial load of the front coilovers was set too much.
reduced the load, by lowering the coil-platform and here we go....the oversteer was reduced.
Yup - did that 11yrs ago on a live axle 7 I had then - made it much better over bumpy B roads too.
BDA said:
Twobone,
One particular issue to caterham/lotus sevens is due to the lower damper mount be in the wrong orientation. IE the bottom eye/bolt is inline with the axle tube. What this does is as the axle goes into roll the small amount of movement in the rubber lower bush is used up, if the car continues to roll the now non compliant bush puts a bending force into the damper rod/body. This will cause severe internal friction in the damper causing the damper to effectively go solid in bump damping. What this does on the road is the car will roll/settle into a steady state on a smooth road but if any further roll or bump is encountered the axle will be severely effected.
The way around this is to use a damper with a spherical joint in the lower eye allowing free movement in roll.
Cheers
Chris
One particular issue to caterham/lotus sevens is due to the lower damper mount be in the wrong orientation. IE the bottom eye/bolt is inline with the axle tube. What this does is as the axle goes into roll the small amount of movement in the rubber lower bush is used up, if the car continues to roll the now non compliant bush puts a bending force into the damper rod/body. This will cause severe internal friction in the damper causing the damper to effectively go solid in bump damping. What this does on the road is the car will roll/settle into a steady state on a smooth road but if any further roll or bump is encountered the axle will be severely effected.
The way around this is to use a damper with a spherical joint in the lower eye allowing free movement in roll.
Cheers
Chris
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