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Pro's and cons of axles and IRS?
paul v6 - 20/9/05 at 08:52 AM

As Im in the early stages of planning my next Locost, I'm in 2 minds as to what would be the better option for my final drive, an axle or IRS???
My intention is to keep weight to a minimum and will be using a bike power plant so low torqe and hopefully 150bhp. Would I be right to think an axle set up would be lighter as well as easier to install, would an escort axle handle a Bike engine?? And are there distinct handling advantages with IRS?

Many thanks

Paul

jambojeef - 20/9/05 at 09:06 AM

Hi Paul,

There have been a few posts on here about this and some people are very knowledgable!

My understanding is that a correctly set up IRS is optimal but difficult to achieve in the home work shop.

I think the general consensus owing to parts availability and comparitive ease of setup is the de-dion tube.

But then Im going for an MK style IRS set-up...!

Im not sure about how much power an escort live axle could handle tho.

Geoff

smart51 - 20/9/05 at 09:27 AM

the fact that no big car maker uses live axles anymore tells you that they are not all that good. Dual wishbone or multi-link IRS gives the best possible setup with the least compromise.

Weight? I don't know.

Setup difficulty? I have been given a rear toe and camber figure to set my VortX to. A camber gauge and spanner got that done OK. Toe in? do it the same way as the front. I guess that if you're not building a kit, you'll not know what to set it to. Then you may need to be an expert. A live axle has no "settings" so is hard to get "wrong"

Memphis Twin - 20/9/05 at 09:32 AM

Escort axles are very strong and much lighter than an IRS or De Dion arrangement. They have no trouble handling bike power, and lightweight diff noses are available (although expensive).

If light weight is your goal I wouldn't be looking at anything else!

Cheers Chris.

Russ-Turner - 20/9/05 at 09:46 AM

30kg's lighter than IRS according to what I read in another thread. Do a search on IRS and IRS wishbones, there will be loads of useful info and pics.

andyd - 20/9/05 at 10:03 AM

Isn't it the unsprung weight that determines good handling though? And don't you get less by using IRS? The saving of 30kg doesn't actually equate to that much more straight line performance but the less unsprung weight you have will make faster cornering better.

Of course I may be talking trash.

Mr G - 20/9/05 at 10:23 AM

quote:
Originally posted by Memphis Twin
Escort axles are very strong and much lighter than an IRS or De Dion arrangement. They have no trouble handling bike power, and lightweight diff noses are available (although expensive).

If light weight is your goal I wouldn't be looking at anything else!

Cheers Chris.



Hmmm i'm not so sure about the de-dion being much heavier than an escort axle, at least on a drum v's drum setup with the diff not being part of the axle your looking at roughly the same or lighter surely? The lobro shafts are fairly beefy but the tripod's are lighter.

Fluke have any figures?

[Edited on 20/9/05 by Mr G]

pdw709 - 20/9/05 at 10:30 AM

Road conditions should also be a factor.

I have always been lead to believe that on a good smooth road i.e. a race track then a live axel set up gives better overall performance + its simpler and lighter. The one draw back is that on bumpy roads then grip/setup may not be optimal.

Kind of depends what you want to do with your car, and the quality of your local council's road maintainance budget!

Phil

britishtrident - 20/9/05 at 11:46 AM

Live axle can give very good results but de Dion or IRS is better --- for a whole load of reasons I favour de Dion but there isn't much in it.

Only reasons de Dion isn't used more on road car is it infringes on boot space -- the ones that do use it tend to be from companies like Bristol, Aston Martin where cost isn't a consideration.