John P
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| posted on 28/8/07 at 07:08 PM |
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DeDion or IRS - What's the Cost / Benefit
Nearly finished tack welding my McSorley 7+4 chassis which I had intended fitting with a DeDion rear to Rorty’s design.
Having a small re-think and before finalising the rear end am considering whether I should go with the Rorty IRS instead but looks like it could be
somewhat more expensive, especially since I was made redundant and no longer have easy access to a fabrication shop.
What’s the general feeling? Is the IRS much more expensive to build and is it worth it for normal fast road work with perhaps a very occasional
track day?
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speedyxjs
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| posted on 28/8/07 at 07:13 PM |
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I dont know much about DeDion but i can see how irs can be expensive, especially if your donor has it.
How long can i resist the temptation to drop a V8 in?
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jacko
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| posted on 28/8/07 at 07:15 PM |
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IF i made a car i would go dedion but i have a Indy for know with irs
Jacko
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t.j.
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| posted on 28/8/07 at 07:15 PM |
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I'm building the IRS.
Not only the driving benefits but IRS is easier to make adjustable.
Grtz
Please feel free to correct my bad English, i'm still learning. Your Dutch is awfull! :-)
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snoopy
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| posted on 28/8/07 at 07:22 PM |
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de dion always gets my vote and always has done 
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Dangle_kt
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| posted on 28/8/07 at 07:55 PM |
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sorry I'm still learning, I know what IRS is, but does a de dion go with a live axel?
Sorry for ignorance!
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Mr Rob
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| posted on 28/8/07 at 07:56 PM |
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Sorry for newbe question but DeDion has the solid rear axel and IRS is independant rear suspension? just checking, it can seem like you all speak
another language at times.
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jacko
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| posted on 28/8/07 at 08:00 PM |
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If you look in jroberts photo archives there is a dedion axel
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ch1ll1
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| posted on 28/8/07 at 08:16 PM |
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jroberts sell the kits,
and its a very good quality kit also !
put one on mine at the start of the year,
no probs yet !
even my welding has held together
paul
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mark chandler
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| posted on 28/8/07 at 10:10 PM |
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My IRS cost a few pounds to make, its 1" tube chassis tube, 6 rose joints and 8 bushes.
The uprights are chopped 1/4" flat bent and welded to shape with the wheel bearing carrier let in and welded.
Dedion needs 8 bushes and 2 rose joints, 2" steel and fabrication of the bearing carriers so the difference is only 4 rose joints @ £4 each
although the 2" tube for a dedion will cost the extra.
So no real cost difference at all if you do it yourself.
Regards Mark
 
Rescued attachment NSR_suspension22Jan2005.JPG
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RK
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| posted on 29/8/07 at 11:26 PM |
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As a mechanically challenged person, I would have gone de dion if it was an option for my frame, but I went MX5 IRS. Can't figure it out yet, so
I don't know what to think. I know IRS is more adjustable, but that's just more to go wrong as far as I'm concerned. I want the car
for Sunday drives and a bit of gymkhana/autocross so performance won't matter to me.
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MikeRJ
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| posted on 30/8/07 at 10:32 AM |
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A well designed IRS can work very well, but if you are building one from scratch with little experience it's probably easier to create a poor
handling IRS system than it is to create a reasonable De-dion system.
Also if you already have a chassis designed for a live axle, the de-dion will require very little modification (primarily diff mounting brackets and
possibly strengthening of the chassis around the diff mounts). An IRS will pretty much require the back end to be cut off and rebuilt.
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Bluemoon
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| posted on 30/8/07 at 12:35 PM |
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I came to the conclusion that De-dion is the best option for track use, and IRS for road... but both are very good if set up correctly.
As to ease of manufacture and cost I don't know!
Cheers
Dan
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procomp
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| posted on 30/8/07 at 12:59 PM |
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Hi why would the dedion be best for track use when the live axle can be used and installed so much lighter.
Yes assuming you can get an axle.
cheers matt
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iank
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| posted on 30/8/07 at 01:36 PM |
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quote:
Originally posted by procomp
Hi why would the dedion be best for track use when the live axle can be used and installed so much lighter.
Yes assuming you can get an axle.
cheers matt
Depends on the race series regulations I suppose 
De Dion carries less un-sprung weight, but more weight overall - but you knew that already. Whether this actually makes a difference +/- each choice
for track use I don't know. Since it's fabricated it's also probably easier to set camber/toe-in on a de-dion than on a live axle
(I've seen midget live axles physically 'adjusted' to do this though  )
De-dion also takes more power (assuming sierra diff vs. escort axle) than a locost live axle - not an issue in locost racing I suspect 
--
Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
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procomp
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| posted on 31/8/07 at 06:57 AM |
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Hi yep if using the english axle NOT the atlas. The unsprung weight is no problem just requires dampers with the right valving to do it.
Adjusting the toe and camber on an axle is no problem. all our kits come with this done as std.
As to overall weight most setups using a sierra diff will be 25-35 kg heavier than a english axle setup.
Also back to the original question. the axles cost about £75 but installing the setup means verry little extra cost. So is also the easiest and
cheapest option. Untill you decide to go for a full disc and Lsd setup then it can get a bit more expencive but still cheaper than a IRS setup.
cheers matt
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Bluemoon
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| posted on 31/8/07 at 10:06 AM |
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Hi Matt, didn't consider live axle, but this should compare o.k to the de-deion and is a lot simpler (but as pointed out unsprung weight needs
to be considered). But it's also not perfect, but then none of them are!
But for occasional track use, but mostly road use I would choose IRS, as you get a better ride, and use the sierra running gear... But it's down
to the individual preference!
Dan
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sgraber
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| posted on 1/9/07 at 02:14 PM |
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quote:
Originally posted by MikeRJ
A well designed IRS can work very well, but if you are building one from scratch with little experience it's probably easier to create a poor
handling IRS system than it is to create a reasonable De-dion system.
Also if you already have a chassis designed for a live axle, the de-dion will require very little modification (primarily diff mounting brackets and
possibly strengthening of the chassis around the diff mounts). An IRS will pretty much require the back end to be cut off and rebuilt.
Hear Hear, Mike!
For the average builder - and if you are asking about which suspension type is better: you definitely fall into this category - the deDion will be
loads easier to bring into a decent state of tune.
Please read what Clive Roberts (former designer of the suspension for Caterham) has to say about it here: http://7faq.com/owbase/ow.asp?deDionOrIRS
/>
Nnote that at the end he now includes a mention about IRS being better, but realize that this is a person whose life is dedicated to designing these
types of things. And he has a lifes worth of experience to draw upon. The "average" Joe simply does not have the resources (time, funding,
test facilities) to make a really bitchin' IRS... (MY OPINION of course). You may get one that functions in a fairly effective manner, but most
home designed ones are evil at the limit. Just think about how many millions of dollars are spent by the big manufacturers on their IRS designs....
In a car as light as these, and where quite honestly you are not trying to achieve a saloon quality ride right? the best thing you can do is keep both
wheels perpendicular to the ground. A deDion/Live will do that under all conditions.
Steve Graber
http://www.grabercars.com/
"Quickness through lightness"
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