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Live-Axle, De-Dion, IRS...
scootz - 9/9/10 at 07:39 PM

Anyone want to have a stab at the pro's and con's of each different set-up?

Only as it applies to real-world road-use...

nick205 - 9/9/10 at 07:46 PM

I'll bite...

Live Axle:
+ Relatively easy to achieve good geometry
+ Simple and effective
- High unsprung weight
- Can be upset on uneven surfaces

IRS:
+ Low(er) unsprung mass
+ Better ride on uneven surfaces
- Much harder to achieve a good design as more variables

De-Dion:
Somewhere between the two above?

mcerd1 - 9/9/10 at 07:47 PM

^^ and you get a torque reaction with a live axle that causes the body to roll when you let you foot off the clutch (as the axle reacts against the chassis throught the springs)
on dedion and IRS the diff is mounted to the chassis so the reaction is just another load in the chassis (i.e. no body roll)


on nice flat surfaces its easy to setup dedion and IRS and the wheels stay nice and flat to the ground regardles of what the body does above it
as the body rolls on an IRS the camber of the wheels changes...

here's dax's explanation:



have a read of this: http://www.carbibles.com/suspension_bible.html



[Edited on 9/9/2010 by mcerd1]

fesycresy - 9/9/10 at 07:54 PM

Have a read of this.

De Dion vs IRS

scootz - 9/9/10 at 08:12 PM

Cheers guys!

StevieB - 9/9/10 at 08:33 PM

I'm interested in the same subject at the moment.

I had been pondering whether to retain a live axle in my midget, with a conversion to 5 link or do an IRS conversion. deDion puts an interesting alternative in the mix which should be a simpler conversion than IRS.

However, would it really make a big difference to the car over retaining a live axle?

scootz - 9/9/10 at 08:45 PM

It's that 'real-world' aspect that I'm most interested in... competition use is one thing, but would I really notice the difference between the 3 whilst back-road scratching?

interestedparty - 9/9/10 at 09:03 PM

quote:
Originally posted by scootz
It's that 'real-world' aspect that I'm most interested in... competition use is one thing, but would I really notice the difference between the 3 whilst back-road scratching?


You would certainly notice the difference between the live axle and the other two, mostly in how bad the thump was when you went over a ridge or similar, and if you were generating some sideways force at the same time, you might even jump sideways a bit (can be fun, though)

mangogrooveworkshop - 9/9/10 at 09:59 PM

Still crash them the same.......

twybrow - 9/9/10 at 10:55 PM

My live axle is incredibly compliant and rides very well over rough surfaces (better than my tin top). It is all in the setup, a well setup live axle will feel a damned sight nicer than a poorly setup IRS.

MikeR - 10/9/10 at 05:07 AM

I believe that comment has been echo'd by procomp a number of times. What was surprising for me was the lack of weight difference between de-dion and live axle. I've gone de-dion and weighed everything (i posted this ages ago). There isn't a huge amount in it - although some benefit.

procomp - 10/9/10 at 10:41 AM

Hi

As said above its all in the setup. The trouble is that most Kit manufacturers who fit a live axle just throw it in the back end with no thought to geometry and then supply dampers that would be more suited to a JCB.

In the real world if you take a little care with the geometry and use a set of dampers that are valved to suit the application you can achieve a very nice compliant ride on the roads. And still have all the advantages available when on the track.

Cheers Matt

scootz - 10/9/10 at 10:45 AM

Cheers all...

PS - Would you sat that an LSD unit was worth the £500 for a road going live-axle car Matt, or not really?

MikeR - 10/9/10 at 11:19 AM

say no, say no, say no, pleeeeease ..... i don't need another excuse to delay / slow down my build!

twybrow - 15/9/10 at 09:53 PM

My LSD transformed my live axle. It took a while to get used to the back slipping, rather than spinning up a rear wheel, but you gain a whole new level to the driving experience. I am no driving god, but I just love the way you can get the car moving on the exit from a corner!