All right, I'm posting this as a bored injurneer looking to unnerstand something, not as a guy looking for advice on what to do for his first rally car or such. So if we could skip all the exhortations to just do something stock and get on stage - 'cause, I know that's a good sentiment, but I can't really get on stage while I'm at work.

Hokay. So what works and why? I know on this gravel crap there's not much grip compared to tarmac, so not much body roll, and not much camber change, but it's not zero, but aside from purpose built things (RS200, McRae R4, etc) double wishbones seem to not work. Why? Just wheel travel? Similarly, Subaru in the last gasps of the factory WRC thingie seem to have gone from multi link rear to struts - same damn thing?

Trailing arms seem to work, strut rears seem to work, live axles seem to work (though maybe not as well?) so does it just get to a kind of thing that it doesn't matter so long as it can move?

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mekilljoydammit
aside from purpose built things (RS200, McRae R4, etc) double wishbones seem to not work. Why? Just wheel travel?

I think it's a matter of re-engineering.

struts are easy - use stock/near-stock mounting points, and you're only really limited by the length of shock and the lower ball joint.

thinking in particular of the honda front double wishbones, right off the bat you've got a second ball joint that may limit travel. In addition, since the double wishbones allow a lower belt-line, you may have less room for a shock (shorter shock -> shorter travel). Not to mention the potential (at the extreme ends of the travel) for the wishbones to start trying to occupy the same space as other suspension components.

getting lots of travel out of a production double-a-arm car is probably not impossible - but it is likely a lot of engineering effort.

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Trailing arms seem to work, strut rears seem to work, live axles seem to work (though maybe not as well?) so does it just get to a kind of thing that it doesn't matter so long as it can move?

pics of both the WRC DS3 and Fiesta at full droop (mmmm, positive camber) would seem to indicate that wheel travel is more important than most other suspension parameters.

Sure, with enough time and effort, one could get a lot of travel out of the double wishbones - but if the "benefits" of double wishbones aren't that important, is it worth the effort?

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KF7RWG
http://www.utahrallygroup.com

Well, one of the things that occured to me as a problem with struts is stiction and bending the suckers; there was all that roller bearing trickery to solve it in WRC until it got banned for example. I just like the idea of the R4 thingy keeping all the expensive shocks away from where they'd get scraped off on things. But I suppose there, the rest of the crap on the corner gets expensive too anyway...

I find it odd that you say there is less roll, there is still a pretty tremendous amount of movement through the corner. They still dive hard under braking, roll through the corner and squat pretty good coming out.



Granted counter steer goofs it all up, but there is plenty of movement.
edit just to put in another cool pic




Edited 1 time(s). Last edit at 05/04/2012 03:26PM by aj_johnson.

Well, when I say "less roll" I'm kind of meaning "compared to slicks on pavement"... but as you put it, maybe there's more than I was thinking. In which case camber gain would be good... unless rally tires don't give a damn about camber.

Never underestimate the roll of rules on what gets used on a car in racing.

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In the long run reality always wins.

I'd love if someone could explain the effects of castor on a rally car. The sidewalls of the rally tires being as stiff as they are, coupled with the lighter side loads on the tire in an ideal corner and the counter steer prolly negate the effects of camber.

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mekilljoydammit
Well, one of the things that occured to me as a problem with struts is stiction and bending the suckers; there was all that roller bearing trickery to solve it in WRC until it got banned for example.

Elaborate whatchoo talkin here?

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John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

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john vanlandingham

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mekilljoydammit
Well, one of the things that occured to me as a problem with struts is stiction and bending the suckers; there was all that roller bearing trickery to solve it in WRC until it got banned for example.

Elaborate whatchoo talkin here?

Well, the bushings in the inverted struts ain't really frictionless, especially when they're being loaded sideways, yaknow? Grease and shit has some initial resistance to movement or changing directions and shit... no I don't have numbers or whatnot. So, at some point in the 00s, the works guys started going to struts with roller bearings. Remember that blog thingie about the privateer running a customer Fuckus? He mentions that. In the last year or two they got banned in rallying everywhere though. Proflex still has pictars of them on their site at http://www.proflex-shockabsorbers.com/subpages/link2.htm

The big boys thought it enough of a concern to bother... apparently touring car racing still uses the roller bearing struts, and think of them as necessary, but budgets are pretty high there. A wanky thing to be concerned about in any rally venue in North America, but on the other hand, no strut (some other sort of suspension that is to say) no stiction.

Roller bearings do nothing about bending shit, obviously... for that I was saying in terms of bending wishbones vs. bending struts.

I do not think, nor have I read/heard anything about linear roller bearings being banned.. they're not that 'spensive, the just are crazy huge overkill.
Which my not work too well in dirty environment.

Where'd you hear this? You may have mis-heard.

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John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

That they were banned... I think I may be mistaken about them being banned in WRC, I'm not sure; coulda swortn. I am seeing mention of them being banned in Group N, and Rally America mentions them in the Open section of the rulebook.

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mekilljoydammit
That they were banned... I think I may be mistaken about them being banned in WRC, I'm not sure; coulda swortn. I am seeing mention of them being banned in Group N, and Rally America mentions them in the Open section of the rulebook.

Are you serious?

I can't imagine RA banning anything just cause it costs a lot of money?
Make no sense.

Please, you search.

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John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

In the 2012 RA rulebook pdf doohicky... 10.2.A.6.d : The use of roller bearings for linear guidance of the shaft within shock absorbers and/or MacPherson struts is prohibited. Guidance of the shaft within the body of the shock absorber or strut must be via solid bushings.

Maybe the priority was more copying FIA than saving costs? I dunno, but I'm pretty sure it just showed up in the 2012 book for RA; I don't remember seeing it before that. Proflex is saying FIA banned roller bearing struts in '08 in Gr.N.

I've heard quite a few drivers talk non-stop about dialing in the suspension setup and finding that perfect point or not being willing to share their perfect setup. Watching these guys on stage is usually a total joke.
I've seen people who don't appear to give a shit and just wing stuff on at a pretty decent neutral setting and kick serious ass.
Reliability is the main driving factor in any suspension change in the rear of a car. Or gearing/diff options. The rest is wanking off.

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Grant Hughes

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mekilljoydammit
In the 2012 RA rulebook pdf doohicky... 10.2.A.6.d : The use of roller bearings for linear guidance of the shaft within shock absorbers and/or MacPherson struts is prohibited. Guidance of the shaft within the body of the shock absorber or strut must be via solid bushings.

Maybe the priority was more copying FIA than saving costs? I dunno, but I'm pretty sure it just showed up in the 2012 book for RA; I don't remember seeing it before that. Proflex is saying FIA banned roller bearing struts in '08 in Gr.N.

OMG.. , no OMFG

Once again supposed, self described "ex spurts" write things that opens cans-o-worms. Why do they does this shit? Has nobody involved in this "rule" ever looked inside modern shit?

Solid. Well some folk use or tell others to use things like this:


Illegal, they aren't solid, they have holes and those holes have some nylon/delrin/whatever but it isn't bronze.


Some struts come with these


These are not "solid" either. They are steel with a copper flash, then a lead/tin/indium overlay...

Hell it might be only JVAB Soooper Bitchin Suspenders are legal since I use SAE660 solid bronze bushings...


We could pick apart the working guidance of the shaft....

but its lake, I have no patience.

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John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.