RIE
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| posted on 9/7/12 at 09:09 PM |
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Fury: IRS vs Live Axle
I know what the differences are between the two setups, but not what they translate to when you drive. Can anyone tell me pros and cons of a live axle
Fury compared to the IRS version? I'm considering looking at a built live axled-Fury.
Cheers
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FuryRebuild
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| posted on 9/7/12 at 09:50 PM |
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I have an early IRS. You get improved grip at the rear end; the motion of the wheels isn't tied together. Moreover, the diff is fixed to the
chassis so there's less weight coupled to the action of your wheels going up and down. This also translates to your propshaft not having to move
up and down do it keeps the mass more in the right places.
On a production car it generally leads to a better ride as well, but in a fury that's set up for horsing about, ride quality isn't
something you should be caring about.
It's more complex in it's construction - it requires a diff carrier, separate drive shafts, different hubs, etc. all to do the work that
the fixed axle could do in one arrangement.
I like my IRS, but don't worry - a well sorted live axle car will drive very well and handle well enough.
When all you have is a hammer, everything around you is a nail.
www.furyrebuild.co.uk
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daniel mason
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| posted on 9/7/12 at 10:03 PM |
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im sure the live axle cars are a fair bit lighter though? most caterhams run de-dion back axle and not irs and they seem to run rather well!
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MK9R
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| posted on 9/7/12 at 10:37 PM |
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Live axle is lighter. The sierra diff is a horrible heavy lump, although the freelander diff is a lighter option for IRS, all depending on what engine
it runs. You are more limited with spring and damper settings on the live axle ass there is less travel to play with, especially the lowered race
chassis.. My race fury is live axle and it still cuts it with the IRS cars, so dont let it put you off. Look at everything else on the car, dont let
the live or IRS question sway your judgement
[Edited on 9/7/12 by MK9R]
[Edited on 9/7/12 by MK9R]
Cheers Austen
RGB car number 9
www.austengreenway.co.uk
www.automatedtechnologygroup.co.uk
www.trackace.co.uk
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phelpsa
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| posted on 9/7/12 at 11:03 PM |
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quote:
Originally posted by MK9R
Live axle is lighter. The sierra diff is a horrible heavy lump, although the freelander diff is a lighter option for IRS, all depending on what engine
it runs. You are more limited with spring and damper settings on the live axle ass there is less travel to play with, especially the lowered race
chassis.. My race fury is live axle and it still cuts it with the IRS cars, so dont let it put you off. Look at everything else on the car, dont let
the live or IRS question sway your judgement
[Edited on 9/7/12 by MK9R]
[Edited on 9/7/12 by MK9R]
Are you sure the freelander diff is lighter? I had had been led to believe it was actually heavier.
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MK9R
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| posted on 10/7/12 at 05:06 AM |
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quote:
Originally posted by phelpsa
quote:
Originally posted by MK9R
Live axle is lighter. The sierra diff is a horrible heavy lump, although the freelander diff is a lighter option for IRS, all depending on what engine
it runs. You are more limited with spring and damper settings on the live axle ass there is less travel to play with, especially the lowered race
chassis.. My race fury is live axle and it still cuts it with the IRS cars, so dont let it put you off. Look at everything else on the car, dont let
the live or IRS question sway your judgement
[Edited on 9/7/12 by MK9R]
[Edited on 9/7/12 by MK9R]
Are you sure the freelander diff is lighter? I had had been led to believe it was actually heavier.
freelander diff casing is aluminium, weighs far less than a sierra. Only comes in 1:3.21 ratio though
[Edited on 10/7/12 by MK9R]
[Edited on 10/7/12 by MK9R]
Cheers Austen
RGB car number 9
www.austengreenway.co.uk
www.automatedtechnologygroup.co.uk
www.trackace.co.uk
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jeffw
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| posted on 10/7/12 at 05:13 AM |
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The primary difference is that a live axle car always has the rear axle setup correctly (difficult not to) and is therefore a predictable handling
car. An IRS car can easily be setup incorrectly and be very wayward. Ultimately, in a well setup IRS car, it will be faster if the surface is less
than racetrack smooth.
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phelpsa
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| posted on 10/7/12 at 06:50 AM |
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quote:
Originally posted by MK9R
quote:
Originally posted by phelpsa
quote:
Originally posted by MK9R
Live axle is lighter. The sierra diff is a horrible heavy lump, although the freelander diff is a lighter option for IRS, all depending on what engine
it runs. You are more limited with spring and damper settings on the live axle ass there is less travel to play with, especially the lowered race
chassis.. My race fury is live axle and it still cuts it with the IRS cars, so dont let it put you off. Look at everything else on the car, dont let
the live or IRS question sway your judgement
[Edited on 9/7/12 by MK9R]
[Edited on 9/7/12 by MK9R]
Are you sure the freelander diff is lighter? I had had been led to believe it was actually heavier.
freelander diff casing is aluminium, weighs far less than a sierra. Only comes in 1:3.21 ratio though
[Edited on 10/7/12 by MK9R]
[Edited on 10/7/12 by MK9R]
The sierra diff casing is Ali too. Do you have the weights for the two?
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MK9R
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| posted on 10/7/12 at 06:54 AM |
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Sorry no weights, just going on how they feel after having them side by side on the bench.
Cheers Austen
RGB car number 9
www.austengreenway.co.uk
www.automatedtechnologygroup.co.uk
www.trackace.co.uk
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phelpsa
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| posted on 10/7/12 at 06:57 AM |
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quote:
Originally posted by MK9R
Sorry no weights, just going on how they feel after having them side by side on the bench.
Ok no problem. The ratio is too high for me anyway :-/
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MK9R
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| posted on 10/7/12 at 06:58 AM |
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quick search shows freelander at 17kg, sierra at 28kg (inc lobro)
Cheers Austen
RGB car number 9
www.austengreenway.co.uk
www.automatedtechnologygroup.co.uk
www.trackace.co.uk
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MikeRJ
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| posted on 10/7/12 at 07:47 AM |
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quote:
Originally posted by MK9R
Live axle is lighter.
That would depend on the live axle in question. An Atlas or Koln axle is unlikely to be lighter, but an English axle is probably lighter than the
entire IRS and extra chassis members required. However I'm not sure if the unsprung weight would be less.
You also need to consider power capabilities; the sierra diff might be a heavy lump but it's a fair bit stronger than an English axle.
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MK9R
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| posted on 10/7/12 at 07:53 AM |
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Should have said English, overal lighter but unsprung weight is heavier, although you can save 5kg with an alu nose for the axle.
Cheers Austen
RGB car number 9
www.austengreenway.co.uk
www.automatedtechnologygroup.co.uk
www.trackace.co.uk
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jeffw
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| posted on 10/7/12 at 08:01 AM |
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quote:
Originally posted by MikeRJ
quote:
Originally posted by MK9R
Live axle is lighter.
That would depend on the live axle in question. An Atlas or Koln axle is unlikely to be lighter, but an English axle is probably lighter than the
entire IRS and extra chassis members required. However I'm not sure if the unsprung weight would be less.
You also need to consider power capabilities; the sierra diff might be a heavy lump but it's a fair bit stronger than an English axle.
I'm running 310BHP through an english axle without an issue (so far)
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jimgiblett
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| posted on 10/7/12 at 08:42 AM |
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There are two variants of Fury IRS. The earlier version single lower wishbones and IIRC Golf struts and the later double wishbone setup. The earlier
versions came recommended with far to high spring settings which made them fine on the track but IMHO way too hard for the road. As said, on track LA
cars can hold their own well against the IRS cars but for everyday driving I prefer the later IRS cars. A friend of mine had his chassis modified
from the early IRS to the later double wishbone setup and he commented that it transformed the car for road use (cost him c£600 IIRC).
Sierra parts whilst getting rarer are far more common than escort. If I was to build again (BEC off course) I would go late IRS with Freelander diff.
If car engined I would go sierra.
- Jim
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RIE
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| posted on 10/7/12 at 11:49 AM |
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Thanks all, lots of useful info as always.
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unijacko67
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| posted on 13/7/12 at 05:21 PM |
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quote:
Originally posted by jeffw
quote:
Originally posted by MikeRJ
quote:
Originally posted by MK9R
Live axle is lighter.
That would depend on the live axle in question. An Atlas or Koln axle is unlikely to be lighter, but an English axle is probably lighter than the
entire IRS and extra chassis members required. However I'm not sure if the unsprung weight would be less.
You also need to consider power capabilities; the sierra diff might be a heavy lump but it's a fair bit stronger than an English axle.
I'm running 310BHP through an english axle without an issue (so far)
It`s good to here 310 bhp and no problem with english axle. The light weight of these car`s must help and put less strain on the drivetrain. No
snapped shafts either? could I ask what tyre width your using. Cheers.
http://www.kittenkitcar.co.uk
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daniel mason
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| posted on 13/7/12 at 06:34 PM |
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im sure its the torque rather than the power which damages gearboxes and diffs
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unijacko67
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| posted on 13/7/12 at 08:30 PM |
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quote:
Originally posted by daniel mason
im sure its the torque rather than the power which damages gearboxes and diffs
Well it must be mainly down to grip that damages things cos if you rev the nutt's of it on the axle stands in the garage it wouldn't
really harm anything. lol
http://www.kittenkitcar.co.uk
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MRLuke
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| posted on 14/7/12 at 06:16 PM |
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I would say it is the reaction force that does it.
So it's a mix of torque weight and grip. Also sudden loadings (shock) ruins them as well. Much the same as a gearbox.
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