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Live axle to Independent suspension
sooty - 6/1/15 at 09:07 PM

Has anyone attempted converting a Raw Striker from a Live rear axle suspension to a Independent drive suspension.

thanks

snapper - 7/1/15 at 06:14 AM

A hlf way house but still excellent handling is to fit Sierra independant with a DeDion bar
The bar fits with the solid axle mounts already on the car you just have to bolt the diff to the body

jeffw - 7/1/15 at 06:22 AM

Has someone actually done a De Dion on a Striker chassis?

owelly - 7/1/15 at 07:16 AM

I converted my live rear end to a De-dion. Not on a Striker but it just used the trailing arm points of the live set-up with a frame to mount the diff.

owelly - 7/1/15 at 07:31 AM



beaver34 - 7/1/15 at 08:54 AM

whats the weight of the De-dion compared to an axle setup?

joneh - 7/1/15 at 09:26 AM

An empty English Axle isn't very heavy at all, so adding on a De-Dion and disc conversion must weigh quite a fair bit more. Don't have figures but it's def more!

Alfa145 - 7/1/15 at 01:10 PM

Seems a pointless change to me, unless you desperately need to use a sierra diff then it becomes slightly more sensible, but if that's the case you may as well go full IRS for the weight saving.

alfas - 7/1/15 at 02:47 PM

my thought was that an IRS is always heavier than a live-axle?

sooty - 7/1/15 at 04:11 PM

quote:
Originally posted by joneh
An empty English Axle isn't very heavy at all, so adding on a De-Dion and disc conversion must weigh quite a fair bit more. Don't have figures but it's def more!


That's my thoughts about weight.

I was thinking more of as suggested using a central diff (all better with LSD) with tubular swing arms similar to the fronts and maybe using FWD hubs such as MK 3 escorts.

beaver34 - 7/1/15 at 06:21 PM

Looked good from the fact for people with high power axle cars it would be cheaper to run the sierra diff than build a axle to take that power

jeffw - 7/1/15 at 06:53 PM

You would be surprised what an English Axle will take.

beaver34 - 7/1/15 at 10:01 PM

quote:
Originally posted by jeffw
You would be surprised what an English Axle will take.


More than a sierra unit?

adithorp - 7/1/15 at 10:19 PM

quote:
Originally posted by jeffw
You would be surprised what an English Axle will take... with a sacrificial gearbox before it.


Fixed that for you

owelly - 7/1/15 at 10:36 PM

My car popped two English diffs and then an Atlas which is why I went for a Sierra LSD type diff. I chose the De-dion because it was an easier conversion for my chassis and imho, the De-dion beam keeps the tyre-contact patch more consistent. I could have made my conversion a lot lighter but the steel I used was free (it was a steel lamp-post, bits of a neighbours tennis court fence and some scrap off-cuts). The De-dion beam is very light. The main weight is the diff, shafts, brakes and dampers! As pictured, my set-up weighed-in at 100kg.

[Edited on 7/1/15 by owelly]

alfas - 8/1/15 at 03:05 PM

the "problem" with the english diff isnt the power! its the torque!!!

if you have 200BHP but with a revy engine the diff will last... an orignal rover v8 (130-150BHP) will kill it sooner than later!!

sooty - 8/1/15 at 05:04 PM

One of my reasons for looking of the change from a Live axle is, when one wheel bumps this also allows the other to do so too by a certain amount and can cause hopping under power in a corner.

Where as a independent drive setup, this does not occur near as much.

Saying this from experience of my two fwd normal cars, one has independent rear suspension and the other a beam type suspension. One will hop if hitting a rut/pot hole in a corner and the other nothing as such.

Tried playing with damper settings soft/hard and no difference is seen, only if too hard the inside will lift or if too soft making conditions worse. Alot maybe due to a lack of a LSD.

alfas - 8/1/15 at 05:33 PM

first i would play with the coils...damper setting does not solve problems if the coil-rate is out of spec
than i would install a LSD to the existing diff


who built the car? ever checked the car at a wheel alignment centre?

usually a sylva has a very good live-axle setup...compared to other english-axle kitcars with similar performance you often think sitting in an IRS-car already.

it seams something generally wrong with your car?

[Edited on 8/1/15 by alfas]

sooty - 8/1/15 at 06:18 PM

Yes its been already been setup and corner weighted etc. One damper was renewed on the rear as a failure.

Some say the coils are too soft and others too stiff, yet say the fronts are ok.

All the bushes and ball joints renewed.

Agree a LSD would help, but are like Gold to find.

Rich J - 8/1/15 at 07:12 PM

Just to throw in another curveball- maybe the rebound on the dampers isn't effective in keeping the wheel in contact with the surface?

The single adjustables I have on my Striker have 8 eight clicks of adjustment but it was demonstrated to me quite easily how ineffective they became after just the first three clicks from "soft"

The rebound was so slow that the shock never recovered to it's full length quickly enough before the next bump.

Hence my signing up for the group buy on here for some double adjustables

alfas - 8/1/15 at 07:52 PM

what dampers are installed?

re-newing 1 single damper is a no-go

who re-newed the bushes and dampers? you?

what type bushes have been fitted?

whats the spring rate of your coils?

who setup the suspension? and why it was setup to the actual measurements?

what are the measurements for camber, castor and tracking

was the rear axle ( even its not adjustable) measured to? what are the values?

was corner weighing done with the weight of the driver on the seat?

jeffw - 8/1/15 at 08:10 PM

quote:
Originally posted by alfas
the "problem" with the english diff isnt the power! its the torque!!!

if you have 200BHP but with a revy engine the diff will last... an orignal rover v8 (130-150BHP) will kill it sooner than later!!


You are probable right....I'm only running 400BHP/300 lb ft through mine. What did a rover V8 kick out?

jeffw - 8/1/15 at 08:11 PM

quote:
Originally posted by adithorp
quote:
Originally posted by jeffw
You would be surprised what an English Axle will take... with a sacrificial gearbox before it.


Fixed that for you


Ohhhh how I lol....Happy New Year mate

jeffw - 8/1/15 at 08:14 PM

quote:
Originally posted by beaver34
quote:
Originally posted by jeffw
You would be surprised what an English Axle will take.


More than a sierra unit?


No, but more that you would expect.

Sam_68 - 8/1/15 at 08:17 PM

quote:
Originally posted by adithorp
quote:
Originally posted by jeffw
You would be surprised what an English Axle will take... with a sacrificial gearbox before it.


Fixed that for you


And a pair of fusible links (AKA 'tyres' ) after it.

Your transmission only takes as much torque as the tyres can transmit to the tarmac.

That's quite a lot in Jeff's case, mind you...

waggy - 17/1/15 at 01:47 AM

I thought the biggest weight factor to be considered when changing from live axle to de-dion was the change in unsprung weight, a disc braked de-dion setup would have significantly less unsprung weight than a disc converted live axle setup.

Sam_68 - 17/1/15 at 02:45 AM

quote:
Originally posted by waggy
I thought the biggest weight factor to be considered when changing from live axle to de-dion was the change in unsprung weight, a disc braked de-dion setup would have significantly less unsprung weight than a disc converted live axle setup.


Yes indeed. You'd taking the weight of the diff. and half of the weight of the driveshafts out of the unsprung weight.

Lightweight cars are very sensitive to unsprung weight, so on anything other than very smooth tracks, the slight penalty of a de Dion in overall weight is usually worth it for the much larger benefits in terms of ride grip and traction.

You need to be careful, though: because it's a structurally inconvenient shape, even a well-designed de Dion tube will weigh more than the tube of a live axle, so eroding some of the advantage, and a badly designed de Dion can actually end up with little or no advantage even in terms of unsprung weight, which makes it an almost complete waste of time...

I say almost complete, because the only other thing that a de Dion does is to decouple the axle from the torque reaction of the propshaft (and from the brakes, if you use inboard discs).

Oddified - 17/1/15 at 09:38 AM

I see the dedion axle as a half way house between a live axle and independent. If done right as mentioned above then it's less unsprung weight but it still connects one wheel to the other so any bump on one wheel still effects the other side.

If i was going to change from a live axle, i'd go full independent as either would be quite a bit of work.

Ian

Sam_68 - 17/1/15 at 10:24 AM

quote:
Originally posted by Oddified
... but it still connects one wheel to the other so any bump on one wheel still effects the other side.


If it's done right (which admittedly it seldom is) then there are ways of overcoming that in terms of transmission of bump forces.

A bump at one wheel will still affect the camber angle at the other wheel, but then you've got to balance that small disadvantage against the quite large positive factors that a de Dion will keep the wheels at a perfectly fixed angle to the road under all combinations of heave, squat and roll, and that there's no jacking effect... neither of which an independent suspension can achieve.

It's also worth remembering that we frequently ruin the main advantage of an independent suspension by bolting on a Beam Axle Conversion Kit (AKA an anti-roll bar) ...which is necessary to combat the large roll angles generated by the low roll centres you are forced to use on an independent suspension to avoid large amounts of jacking. With a beam axle, no jacking = no need for low roll centres = no need for an ARB.

I'm playing Devil's Advocate, of course - as much as I like beam axles, I'm forced to admit that you need an exceptionally good de Dion design to match a merely competent independent design - but surprisingly good things are possible if you are careful enough.

[Edited on 17/1/15 by Sam_68]

Oddified - 17/1/15 at 11:43 AM

quote:
Originally posted by Sam_68
quote:
Originally posted by Oddified
... but it still connects one wheel to the other so any bump on one wheel still effects the other side.


If it's done right (which admittedly it seldom is) then there are ways of overcoming that in terms of transmission of bump forces.

A bump at one wheel will still affect the camber angle at the other wheel, but then you've got to balance that small disadvantage against the quite large positive factors that a de Dion will keep the wheels at a perfectly fixed angle to the road under all combinations of heave, squat and roll, and that there's no jacking effect... neither of which an independent suspension can achieve.

[Edited on 17/1/15 by Sam_68]


Absolutely, but the same could be said for a live axle 'if it's done right'. A dedion 'should' have less unsprung weight but otherwise is no different to a live axle if both are done correctly. Independent suspension is a whole different world with pro's and cons to work into the design. Everything is a compromise.

Ian

Sam_68 - 17/1/15 at 12:14 PM

quote:
Originally posted by Oddified
Absolutely, but the same could be said for a live axle 'if it's done right'. A dedion 'should' have less unsprung weight but otherwise is no different to a live axle if both are done correctly.


Well, apart from being decoupled from the propshaft's torque reaction (and brake torque reaction, if you choose to use inboard discs).

Also, it's easier to build in (or add adjustability of) toe and negative camber on a de Dion than it is on a live axle.

But yes, in terms of basic geometry, they're identical.

coozer - 17/1/15 at 02:24 PM

Don't forget its inertia that kills diffs and gearboxes, the torque required to move the mass of the vehicle forward is what puts these things under stress, the less weight, the less inertia required to move the mass, the less stress on the driving parts.

So maybe beefing up the axle checking the spring and damper settings or relocating the mounting points, using a watts linkage? to improve tracking and bump??

Mate of mine has a 73 mk1 escort with a 550bhp cosworth engine. Its totaly stripped out but he's a big lad, probably wieghs about 600kg, the thing can lift the front wheels! Standard axle with group 4 half shafts and a plate LSD, single leafs and remote gas dampers.. Goes very well..

Plenty of high horsepower scorts on live axles about..

alfas - 18/1/15 at 04:32 PM

quote:
Originally posted by alfas
what dampers are installed?

re-newing 1 single damper is a no-go

who re-newed the bushes and dampers? you?

what type bushes have been fitted?

whats the spring rate of your coils?

who setup the suspension? and why it was setup to the actual measurements?

what are the measurements for camber, castor and tracking

was the rear axle ( even its not adjustable) measured to? what are the values?

was corner weighing done with the weight of the driver on the seat?



still no answers......

scootz - 18/1/15 at 05:25 PM

Would you not be better off just buying a IRS chassis? There's a fair amount of difference at the back-end of the 2 Striker variants... the tunnel measurements being the biggest PITA.

alfas - 18/1/15 at 07:18 PM

wouldnt it be easier to get the basics done correctly first?

like 4 quality dampers, correctly valved for this car. trying with different coil rates. reducing unsprung weight (in case big wheels and /or heavy alloys are fitted). new metalasitc bushes at the rear trailing arms (instead of poly“s) correctly mounted (bolts tightend when car is back on the wheels), checking if chassis is straight and the axle is properly located.

all the live-axle sylva“s i have driven (which have been min. 10cars) usually had an IRS feeling compared to other live-axled (sevenish) cars ...e.g. westfields, tigers, locosts which had a much harsher suspension.