IRS Vs Solid Axle

[MGBV8]

Interesting...

https://grassrootsmotorsports.com/articles/suspension-mythbusting-solid-axle-vs-irs/

[Airwreckc]

Good to know--makes me feel better about using my Ford 8".  Thanks for posting, Carl.

[BlownMGB-V8]

Depends on what you are after. generally the solid axle will be better for straight line acceleration and the IRS will be better on uneven or rough road surfaces.

Jim

[MGBV8]

I agree with the author.  I do not believe that the IRS is superior on a road course.

[BlownMGB-V8]

I guess it depends...

Jim

[ag1234]

So ,  are most of us, using our cars primarily for road courses ? Sounds like roads in many states are becoming 1,5 caca ? How do you get a good camber curve on a solid axle ?
                                                                                 Art.

[MGBV8]

Street cars will have compromises & with IRS squat & dive things are constantly changing.  I  am certain that designing a good IRS is a giant PITA.

On the other hand my B has little body roll & not that much suspension travel.  So, the camber gain is not much of an issue.   I prefer the simplicity of the live axle.

[BlownMGB-V8]

Certainly a live axle is much less expensive and much simpler to implement than a well designed IRS, and one that squats on launch is not that well designed. Squatting means that the axle is lifted, a thing that does not contribute to maintaining tire contact. Drag racers lift the rear on launch to put more initial pressure on the tire patch, but much more commonly body height is unchanged. The TR4/6 is a notable exception.

IF the IRS is restricted in travel as the stock axle sometimes is with lowered ride height, stiff springs and shocks there may not be much of a noticeable improvement. However if the install is done in such a way to take advantage of what the IRS has to offer the results can be significant. It may take some time to tune the suspension and achieve these results.

I feel I have accomplished this now with the MG-Roadmaster and my roadster using the narrowed Jag IRS and the widened bodywork.

Carl will be driving the RM this coming weekend to attend the GCBCC show and will have the opportunity to evaluate all aspects of the car including the handling and I look forward to his feedback. The car is not fitted with sticky tires like his so it won't be any sort of direct comparison but it should be interesting nonetheless. I do have a couple of twisty local roads I can show him.

Jim

[ag1234]

Grassroots ignores the benefits of camber curves and low unsprung weights on bumpy roads.. Use aluminum Dana 36 of 44/ Vette with its connectors/ geometry =good to go.
                                                                  Art.

[DiDueColpi]

Just an FYI.
It is very easy to get a negative camber from a live axle.
Many of us old racers have done it since god was little.
You simply bend the housing, some axles will give you up to a degree of negative camber with no issues at all.
It sounds haywire beyond belief but it works very well. A worn set of side gears are your best friend.
My P1800 ES  has been run that way for 20 odd years or so with no issues.
Makes the tire guys with the free alignment checks freak out though.

Live like you mean it.
Fred

[BlownMGB-V8]

More and more I appreciate the ride that the IRS gives. My MG is now the best riding car in the fleet and most of that is due to the Jag rear suspension. It also handles pretty good.

An additional factor is that with the wider stance (It's 6" wider than stock) it can sit higher and still achieve the same cornering forces as the angle between CG and contact patch allows a higher body height due to the increased track width. This was something emphasized by GM's marketing division back in the 60's beginning with the "Wide Track Pontiac" promotion. It held true as GM sold wide and low sedans up into the mid 70's before losing their way. I can personally attest that unless you tripped the car on a curb or something it was impossible to flip one of their G-body sedans on flat level ground at speeds up to and over 60 mph. Not true of all cars sold during that era. I managed to get 'Bev' the Christine soul sister, so far up on two wheels she had gravel in the headlight trim ring one day, attempting a move that the 1970 Cutlass could and did handle with aplomb.

Jim