Sorry to open a can of worms, but would just like to share my limited experience.
After driving my Avon (IRS) around Elvington, which I though handled well at the time and driving the Bitsablade today (Lie Axle)...
I vote for Live Axle every time.
Handling was spot on and very smooth and a real pleasure to drive.
Pat...
Live axles do well on even ground, like at Elvington. On uneven ground they get unsettled more than IRS.
An IRS setup should give better ride, IF it is set up properly.
quote:
Originally posted by Avoneer
Sorry to open a can of worms, but would just like to share my limited experience.
After driving my Avon (IRS) around Elvington, which I though handled well at the time and driving the Bitsablade today (Lie Axle)...
I vote for Live Axle every time.
Handling was spot on and very smooth and a real pleasure to drive.
Pat...
Just to add, and I't not just me, it seems a hell of a lot smoother at the back than my Avon ever did on the road.
And this car has hard GRP seats, not comfy Richfields like the Avon.
Yep - I agree Smart 51, but like everyone says, IRS has to be set up properly and probably beyond most of us locosters.
My Avon was set up out of the box, as is my Bitsablade and I can only compare the two and I know what I'd have again!
Pat...
The avon didn't have a good setup.
As they give positive camber in drop. And you need negative.
I hope mine will drive nicely as i followed the pricipals as good as possible.
Grtz
Didn't have a good setup - but it handled suprisingly well when pushed hard.
Pat...
Its my understanding that the live axle is the lighter set up as well by some margin.
well after blasting around RAF marham yesterday , the car oversteered like a mother f****r , wanting to spin everywhere , until we swapped the springs
front to rear after that it was very forgiving , giving power oversteer on demand .
Big bloody Volvo live axle gets my vote ,lol.
unfortunately the tit behind the wheel was the reason for the 100 mph spins searching for a box of neutrals .
the colway intermediates , were pretty good too .
before i sorted the spring problem , on the bumps it was pretty dangerous , now it does bottom out and i need more travel .
that said , i had no problems with the front inboard suspension , apart from not being able to find a significant amount of understeer .
Ive driven a few well set up IRS Westfields on track as well as my own fairly book live axled Locost, and what Ive found is that although the Westies
seem to grip if anything a little more and the car feels very planted and will no doubt lap quickly, they don't tend to communicate on the limit
as well as a live axle (and De Dion I suspect), and feel a bit "dead" so you don't really know how close to the limit you are.
In contrast the live axle tends to move around more with the need for minor corrections throughout the corner, and if going from an IRS car to live I
suspect it could feel a little un-nerving, but once you realise that just because its moving around a bit more doesnt mean its about to swap ends, I
think its more fun to drive on the limit and probably as quick because you can feel and therefore push to the limit more often.
Chris
[Edited on 2/9/07 by ChrisGamlin]
quote:
Originally posted by t.j.
The avon didn't have a good setup.
As they give positive camber in drop. And you need negative.
I hope mine will drive nicely as i followed the pricipals as good as possible.
Grtz
Matt @ Procomp must be having a day away from the PC!
Craig, I assume he probably means chassis "drop", not droop, ie in roll when the chassis gets lower to the ground.
quote:
Originally posted by TimC
Matt @ Procomp must be having a day away from the PC!
quote:
Originally posted by ChrisGamlin
Craig, I assume he probably means chassis "drop", not droop, ie in roll when the chassis gets lower to the ground.
Not sure if thats correct or not as I dont have any experience of the Tiger, just what I assumed from the comment made.
Hi ime not going to get drawn into individual chassis and geometry of irs.
But what Chrissgamlin says pretty much hitts the nail on the head.
When on the limits the irs setup still has a tendancy to be moving it geo around and in most of the kitcar world setups its moving in the wrong
direction for more grip.
This means that the liveaxle/dedion setup which has no/farless movement. When on the limit dose not let you down suddenly with grip it just stays
where it is and lets the tyres do what are doing. It dose not start moving the camber the wrong way or sudenly start changing the toe setup from in
to out.
It all meanns that on the limit it's more controlable as nothings moving where it shouldent. As to ride quality all you have to do is invest in
some decent dampers to suit the application. But they can be done for as little as £90 Ea to suit.
cheers matt
PS i am not saying that an irs cant be made to work . Its just that no one in the UK kit industry has done one as yet that is of any use Except the
first of the westfield irs setup done by Jenvy.
quote:
Originally posted by Avoneer
quote:
Originally posted by TimC
Matt @ Procomp must be having a day away from the PC!
Nope - i've been keeping him busy on U2U about trailing arm bushes as I value his opinion and experience as a racer etc.
Pat...
quote:
Originally posted by craig1410
quote:
Originally posted by t.j.
The avon didn't have a good setup.
As they give positive camber in drop. And you need negative.
I hope mine will drive nicely as i followed the pricipals as good as possible.
Grtz
Not sure if I'm misunderstanding you here but I would want positive camber on drop myself.
When cornering, the loaded side (outside) would compress and should gain a bit of dynamic negative camber to compensate for body roll while the unloaded, inside wheel should gain dynamic positive camber. I don't know why you would want the unloaded (dropping) wheel to gain negative camber as it would be tilting the wheel in ths same direction as the body roll and would result in just the inside shoulder of the tyre contacting the ground.
Of course when I say positive camber I'm not sure that it would actually end up with net positive camber as you would start off with static negative camber normally and the dynamic positive camber on drop might not be enough to counteract the static negative camber at ride height.
HTH,
Craig.
quote:
Originally posted by t.j.
So droop is lifting the car and compression is pushing the car down?
Some one had better make the case for IRS.... OK I had to do a bit of homework when I designed mine, but fabrication and setup is really no big deal,
no big deal at all.
You don't get the benefit of IRS in lap times because tracks are smooth and the setup is heavier than live axle. Where you win is out on real
roads with potholes & knackered tarmac. Here, a correctly setup live axle will spend a lot of time with the wheels in the air and you'll soon
suffer from compressed vertebrae!
The only part of my build I sort of tried hard with was to get unsprung weight down. I measured it using bathroom scales with the spring out -
it's 31kg on every corner, front and back. The up side of this is that I am able to run with 125lb/in springs at the rear.
I make no claims for the out & out performance of the thing - I do know it's nice & comfy!! I expect it would corner better than a live
axle setup on a poor surface but have no proof.
Bob
quote:
Originally posted by t.j.
Sorry, my fault.
As the inner top wishbone brackets are higher that the top off the rear-upright pick-up there is positive camber gain as that wheel will be loaded at cornering. So your negative camber which is needed is not getting more at cornering but less due the positive camber-gain.
I replaced the top brackets lower and made a new upright, so that my roll-centre and camber-gain is following the book pricipals.
I ment with droop, dropping the car. Sorry
So droop is lifting the car and compression is pushing the car down?
BTW: Wheel alligment? it is one big compromise!
Grtz
[Edited on 2/9/07 by t.j.]
That's the thing though - I find my live axel and hard GRP seats much smoother and comfier than the IRS on the Avon which had comfy Richfield
seats.
Might be my age???
Pat...
I'm not sure that it is as simple as, "IRS is comfy" and "live axle is hard". I think it all depends on spring and damper
settings. I've done the calculations in the Allan Staniforth book on race car suspension design and my GTS Tuning spring/damper sets with 275lb
front and 175lb rear springs are very much toward the firmly sprung end of the scale. I'm also using rod-ends at the rear and nylon bushes at the
front so I fully expect to lose my fillings every trip! Seriously though, I didn't build this car to cruise through the Alps, I built it to blast
through the Scottish country roads with my teeth gritted. Who cares if it's harsh over the bumps!!
Craig.
They were both set up lcost style though without any engineering type help and on that gorunds, that's all I have to base the differences on.
Pat...
Hi a well setup live axle will run with 120lb - 140lb springs.
And with the correct dampers for this setup ( wich no damper manufacturer offers off the shelf) you will be able to obtain virtually as good a ride on
the roads as you will with the irs.
Given that 50% of kitcars are driving around with dampers that are just not valved correctly for them in the first place kinda puts thing into
perspective. Unlike in the USA where they take thier dampers verry seriously. Verry few down at kitcar level in the UK even give them a second
thought they just order them and fit them. No balancing or checking or even finding if they are even remotley valved correctly. Its complete madness
considering we are running light weight cars where the damper plays such an important part of the package.
cheers matt
Ps sorry that turned into a rant again
Trying to turn the rant into a positive
Does anyone know,
a) can dampers be re-valved
b) who'll do it
c) can you do it at home
d) how
e) who's dampers are easiest to revalve
f) who's are closest to the sort of settings we'd like?
I've got rebuilt avo dampers originally sourced from westfield for a westfield live axle with the intention to run 220lbs at the front and
175's at the rear as a starting point.
I bought some new dampers direct from Avo a while ago. When I ordered them I told them what the car was, the axle weight and the springs I was going
to use, and they were happy to valve them accordingly. Their price was roughly the same as any other Avo supplier.
I believe that procomp will happily do the same.
I'd like to know whether Avo shocks supplied through the normal distributors can be re-valved, as I'd like to get my front ones done. (I
suppose I could ask Avo...)
David
Just to throw a spanner in the works Pat, can you really remember how your Avon handled enough to do a direct comparison between IRS and live
axle?? It must be a good few years since you last drove it. Bear in mind that they are completely different vehicles with very different engines.
I'm not saying there isn't a difference between the two, cos I've never driven a live axle seven, it's just that I don't
think I could compare the handling between two very different cars after an interval of two weeks, let alone two years.
Phil
I hear you Phil - but this car is just so much nicer to drive.
Not just me that's said it, but a few of my passengers as well.
Will take you for a blast when we end up on the same track day.
I was very pleasantly suprised.
Pat...