Advanced Suspension Geometry and Design

Re: Advanced Suspension Geometry and Design

Cosworth — Tue, 05 Apr 2016 23:13:34 -0500

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NoCoast
So is this a benefit of progressive springs/dampers as well?

No, you can achieve that with any kind of shock valving, progressive, digressive, linear or regressive (penke's lol). Progressive springs have no business in racing otherwise WRC/WTCC/F3/etc. wouldnt still be running linear stuff. I have them in my DMS and they're shite... the "soft" part gets compressed right away from the preload or weight of the car, and my Reigers have a longer but softer spring.

Re: Advanced Suspension Geometry and Design

NoCoast — Tue, 05 Apr 2016 09:44:11 -0500

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Cosworth
The only thing suspension wise that can help is the fact that they have more wheel travel and can afford to run softer springs than before and therefore more grip. Otherwise its all brakes.

So is this a benefit of progressive springs/dampers as well?

Re: Advanced Suspension Geometry and Design

Cosworth — Mon, 04 Apr 2016 16:42:55 -0500

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MConte05
Call me stupid, but why would that make a difference? All the braking force is generated through the tires right? If they were using Michilens back in 2006 vs DMACK DMG2+, but the same size tire as in 2016 (215 width) then shouldn't be too much of a difference? Pastrana seemed to be suggesting it was the way the new 2016 car was designed from the ground up, not so much a better brake pad or tire.

Because a higher bite pad will always give the impression of better brake setup because less pedal force is required. And for a driver that immediately says better car, even if the distances are the same. Doesnt really matter what Pastrana suggests, of course he's going to talk wonders of the new car. But back then they had a GrN setup with stock m/c and GrN spacer, which is incredibly hard brake pedal, along with DS3000 pads, its nearly impossible to get brake look up. Now with a pedal box and better pads, its much easier to extract more out of the brakes.

The only thing suspension wise that can help is the fact that they have more wheel travel and can afford to run softer springs than before and therefore more grip. Otherwise its all brakes.

Re: Advanced Suspension Geometry and Design

MConte05 — Mon, 04 Apr 2016 14:18:29 -0500

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Cosworth

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MConte05
...the biggest change was just how incredible the straight line braking was compared to the 06 car ... but the braking was where a lot of time was gained. What part of the geometry could be changed to improve that?
Nothing to do with suspension geometry, in 2006 they were still running the old shitty Ferodo DS3000, then in 2009 I introduced them to PFC, and I know in 2012 they were still using them while I was in UK cause I'd get calls sometimes, but now I think they went to Endless pads.

All the antidives and prodive geometries are great but do very little to inline -G.

Call me stupid, but why would that make a difference? All the braking force is generated through the tires right? If they were using Michilens back in 2006 vs DMACK DMG2+, but the same size tire as in 2016 (215 width) then shouldn't be too much of a difference? Pastrana seemed to be suggesting it was the way the new 2016 car was designed from the ground up, not so much a better brake pad or tire.

Re: Advanced Suspension Geometry and Design

Cosworth — Mon, 04 Apr 2016 13:25:19 -0500

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MConte05
...the biggest change was just how incredible the straight line braking was compared to the 06 car ... but the braking was where a lot of time was gained. What part of the geometry could be changed to improve that?

Nothing to do with suspension geometry, in 2006 they were still running the old shitty Ferodo DS3000, then in 2009 I introduced them to PFC, and I know in 2012 they were still using them while I was in UK cause I'd get calls sometimes, but now I think they went to Endless pads.

All the antidives and prodive geometries are great but do very little to inline -G.

Re: Advanced Suspension Geometry and Design

john vanlandingham — Tue, 29 Mar 2016 16:27:48 -0500

Quote
MConte05
So I'm resurrecting this thread. Some interesting stuff, some great links (ordered some books last night) and some good discussion.

As some of you know, my leggy shell is done for, and starting to look into building up a car. Got a lead on a clean GD shell for cheap, most all my stuff will bolt up to it (only 1/4 of the leggy is ruined) and I plan on building up the car in accordance of the new National Limited Open rules. Which basically puts restrictions the majority of the suspension components. Things like subframes must remain stock, stock hubs must be used, stock mounting points must be retained, the rear strut mounting can be raised up to 3" for those GR subie guys.

My question here is, what could be done to maximize or improve the subaru geometry? I plan on buying the bilstein tubes and doing my own ears and turning. I can design up and fabricate custom control arms, as well as strut mounts. Would adding a lot of caster through a custom control arm and mount amount to anything? Any geometry that could be corrected through well designed lateral links and trailing links in the rear?

I got to spend a lot of time under SRTUSA's 06-07 car last week and was really surprised to see how much of it was stock. Truly was a group N car that just had some nice engine bits and a dogbox trans. Off the shelf parts everywhere. Cusco trailing arms, stock STI front arms, stock hubs, etc. compared to the 2016 car that is basically an entirely new car from the firewall forward. In talking with Pastrana how his new 2016 car compared to the 06 car, he mentioned that besides the obvious power increase, the biggest change was just how incredible the straight line braking was compared to the 06 car. That the sideways grip was still similar, but the braking was where a lot of time was gained. What part of the geometry could be changed to improve that?

Still learning more and more about the suspension geometry and how things play together with an eye to try and improve a new shell to the limit of the rules.

Its a shame about the Le-gassy..
Those GD are more or less the same as any other Subie, just seems like a LOT heavier and slightly different execution of the rear top mount...just to annoy people...

Who knows really what can be done regarding actual geometry...Not much..More casyer would be nice to a point, but you retain the stock knuckles--especially in the rear and you're kinda locked in..
One thing I did for Colin Bombara out East to try and mitigate some of the bad bending load on the rear ears was I made him a spherical bearing top mount, a nice strong one...BIG bearing..
The idea was as the suspension goes up and the arc of the knuckle/hub begins to "go over the top of the arc" with a bearing, the bearing can rotate and no bind up like a solid rubber thing will..
It stopped the bending which was pretty bad...Of course this is more of an issue with struts with 210 travel cause the knuckle/hub moves higher in the arc...

Now as for you getting some of the Bilsteins, I am assuming you are meaning their so called universal 50s, yes?

You better do some planning because as far as I know as of maybe 5 minutes ago they have only a few obscure parts and unfortunately for some, no lower tubes....
And I think I just cleaned them out of the last of the fronts and rears which they had remaining which would be the thing for a GD and that's only because I have so many tubes......Evidently I have moved 90% of what they have sold of these....

So some hurdles ahead..

I am negotiating with them about some design changes and just how they are marketing them--as well as their fixed valving choices some of which they will never sell cause they're flat ODD>

Re: Advanced Suspension Geometry and Design

MConte05 — Tue, 29 Mar 2016 13:22:53 -0500

So I'm resurrecting this thread. Some interesting stuff, some great links (ordered some books last night) and some good discussion.

As some of you know, my leggy shell is done for, and starting to look into building up a car. Got a lead on a clean GD shell for cheap, most all my stuff will bolt up to it (only 1/4 of the leggy is ruined) and I plan on building up the car in accordance of the new National Limited Open rules. Which basically puts restrictions the majority of the suspension components. Things like subframes must remain stock, stock hubs must be used, stock mounting points must be retained, the rear strut mounting can be raised up to 3" for those GR subie guys.

My question here is, what could be done to maximize or improve the subaru geometry? I plan on buying the bilstein tubes and doing my own ears and turning. I can design up and fabricate custom control arms, as well as strut mounts. Would adding a lot of caster through a custom control arm and mount amount to anything? Any geometry that could be corrected through well designed lateral links and trailing links in the rear?

I got to spend a lot of time under SRTUSA's 06-07 car last week and was really surprised to see how much of it was stock. Truly was a group N car that just had some nice engine bits and a dogbox trans. Off the shelf parts everywhere. Cusco trailing arms, stock STI front arms, stock hubs, etc. compared to the 2016 car that is basically an entirely new car from the firewall forward. In talking with Pastrana how his new 2016 car compared to the 06 car, he mentioned that besides the obvious power increase, the biggest change was just how incredible the straight line braking was compared to the 06 car. That the sideways grip was still similar, but the braking was where a lot of time was gained. What part of the geometry could be changed to improve that?

Still learning more and more about the suspension geometry and how things play together with an eye to try and improve a new shell to the limit of the rules.

Re: Advanced Suspension Geometry and Design

Iowa999 — Mon, 31 Mar 2014 16:51:59 -0500

Here's another issue that might motivate the angling of the shock across the top of the axle, as on WRC cars (besides anti-dive from torque on the hub and getting more room for long-travel shocks): by having the shock not be a perfect radius from the axle, there will be much less side-force on the shock during braking. This force becomes the force that tries to extend the shock, instead, when the shock comes across on top of the axle.

Maybe fancy rally shocks (lubricated by male reproductive juice, in some cases) don't suffer from "stiction" when side-forces are applied, so maybe this is a useless point. But I thought I'd bring it up since I found it on a napkin at lunch.

Re: Advanced Suspension Geometry and Design

Iowa999 — Sat, 29 Mar 2014 22:58:54 -0500

Oops. Yeah. You'd get anti-dive from the shock's angle. I was thinking of the typical LCA angle.

Re: Advanced Suspension Geometry and Design

Mad Matt F — Sat, 29 Mar 2014 22:02:42 -0500

Oui. re the angle. as I so eloquently tried to say something to that effect.

my point was the long travel in a short space.

but in the case of angled ahead, does the brake torque not cause a moment that pulls the spring/shock apart in effect causing anti dive with a compliant spring for bump?

Re: Advanced Suspension Geometry and Design

Iowa999 — Sat, 29 Mar 2014 20:07:12 -0500

Isn't that the opposite of Dubya Are See? They're angling the shock behind the axle to get anti-dive and anti-squat, while WRC fronts have the shock in front the axle for pre-dive and, therefore, compliance under braking.

Or did I miss the point?

Re: Advanced Suspension Geometry and Design

Mad Matt F — Sat, 29 Mar 2014 14:37:39 -0500

Hmmm

Google kills another hour...

http://www.google.com/patents/US4105222

I won't post the whole text... you can go to the link

but tid bit from a 1978 patent... looks like "modern" Dubya Arrr Seee, cept behind instead of in front of the driveshaft...

Abstract
An independent strut-type suspension system for a front wheel drive vehicle, wherein the shock absorber is secured at the lower end thereof to the steering knuckle at an angle such that it extends rearwardly of the drive shaft and below the center line thereof, providing a low overall height profile, coupled with anti-dive and anti-lift characteristics, with a coil spring mounted eccentrically around the shock absorber to diminish bending moments on the shock absorber.

Bla bla bla

Re: Advanced Suspension Geometry and Design

Pete — Sun, 23 Mar 2014 08:07:41 -0500

Which FWD trailing arms are we talking about? I can think of a few designs that are far from static in their toe or camber curve.

Re: Advanced Suspension Geometry and Design

Reamer — Sat, 22 Mar 2014 16:00:37 -0500

I believe I got my rear susp sorted out bump wise ive moved things around and it seems to do what paper says it should do. I need to sort out the rear shock and spring combo and I think it is ready to throw dirt.

Re: Advanced Suspension Geometry and Design

Reamer — Sat, 22 Mar 2014 15:57:10 -0500

I mean $1800 Trick diff controller married to a $3500 ecu. T/C kickin it dirt style! My bad.

I was told it was corrected in the shock package. Do you have any thing on what they actually did for valving to fix this? I can buy there rear shocks for a small fee. But would rather revalve what I have if I could find out what it needs.

Over thinking is prolly correct but if someone fast ever gets behind the wheel of my ride they should be happy with how it drives. Plus my next rally isnt until STPR so what else should I do except Test at my compound that I dont have, tinker with susp crap and car diets! The cars down to 3130lb need to lose another 250lbs! I could prolly drop 50 off myself but the car still needs to weigh 2900lb with out me.

It is lighter then sp rules so im in the ball park if the car had a driver it could prolly run up towards the front of RA rallies.

Re: Advanced Suspension Geometry and Design

Iowa999 — Sat, 22 Mar 2014 15:46:01 -0500

Trailing arms make the system a tad more difficult to model on a napkin, but they also make it more important to do so, because of how the trailing arm shifts the entire wheel back during bump. What you often find is that the slight difference in the lengths of the so-called camber arm and toe arm causes most of the toe change to be due to the rearward shift of the wheel due to the trailing arm, instead of mere non-parallelness of the two lower arms.

In any event, the solution is often as simple as swamping to a taller-stalk ball-joint on one of the two lower arms. By making the two lower arms (more) non-parallel, you can swap a car from having a negative to a positive bump-toe curve. The only issue is whether the off-the-shelf versions of said long-stalk ball-joints will stand up to the beating of rally.

Re: Advanced Suspension Geometry and Design

Cosworth — Sat, 22 Mar 2014 15:28:58 -0500

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john vanlandingham
Paulino mio, do you know what bushes or what those car listed had in their links?

Aluminum bushes inserted into the OEM arms on cars like R2's and Heims on the more Group Aish type of cars.

Re: Advanced Suspension Geometry and Design

Cosworth — Sat, 22 Mar 2014 15:26:36 -0500

You boys are over thinking this, these are FWD cars with trailing arm rear suspension setups that have nearly zero travel, and there's no rear bump steer. So a static 5mm toe in, is a dynamic 5mm tow in. Now this doesn't mean it will work well for your cars.

As for the SP cars, they don't have trick diffs, its all stock. And the newer ones with the handicapped rear suspension, its been long fixed with shock valving. The cars handle just as well as the previous. Just not as light. They are actually pretty good, because in Group N they have put the evo out of business.

I cant attach those setup sheets I have, they're PDF's and this board wants images. Anyone know how can I upload these things here. I have Citroen and Peugeot stuff.

Re: Advanced Suspension Geometry and Design

Reamer — Sat, 22 Mar 2014 15:07:23 -0500

Yes. Thats what ive read also. Paul is saying 4mm in at ride hieght. That makes sense to me to make the rear more stable entering.

The stock 08 is junk for this and this very well could be the issue me and other with 08 are seeing. The rear bump steer at snodrift on my car was going the opposite direction. In on compression and out on droop. Lots out on droop. So my theory is when you get hard on brakes and get the ass light the car will step out in the rear super easy. This was shown in Osullivan's test crash. His may have been cold brakes. I feel he is more talented then that and could of corrected if it were just brakes. because of piss poor rear susp design 2 things cought him out and he couldnt save it.

It looks like Subaru wanted a bolt in rear susp. Where all the arms will bolt onto one cradle and they can take that cradle and fit it into any chassis they want. Makes sense for production line but horrible for the racer.

What vsc and I coppied was get rid of the short front trailing arm. Make a longer tie rod to correct bump steer. A stock rear tie rod is 10" long mine is now 14.5" long. My bump is super close now. I cant even guess how far off stock is over 4" shorter and way off from where it needs to be located to get zero bump. The stock trailing arm is so much shorter the tire pulls foward so much on droop the tire almost hits the front of the wheel well. Jack the back of an 08 up and watch the tire swing foward a mile. That has to be inconsistant feeling to drive.

I am super impressed with how SP teams have figured out how to make these cars fast. Then again Cline runs within 1/2 sec mile speeds with a bone stock sti, stock ecu stock diffs and diff controller from a 100k 05. with miss matched front rear susp. Running against vsc built sp cars with anti lag and trick diffs. Wonder how fast Van way or Roberts would be if they were in an 07. My guess is way faster.

Re: Advanced Suspension Geometry and Design

Iowa999 — Sat, 22 Mar 2014 12:59:38 -0500

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Reamer
You guys just dont get what im typing.

I do.

One of the best designs that I've seen has a flat (at zero) bump-toe curve in the front, with the suggested starting value of zero toe. In the rear, the curve was nearly linear, with toe-out in bump and toe-in in rebound. At static ride-height, toe was set to about .04 in (on each side). At full squat, toe was zero; at full droop, it was about .08 in (on each side).

The logic is simple. You want rear toe-in when the butt of the car rises under braking. You want near-zero rear toe when the butt sink under power. You always want the front near zero so the car is predictable.

Re: Advanced Suspension Geometry and Design

john vanlandingham — Sat, 22 Mar 2014 12:07:42 -0500

Quote
Reamer
You guys just dont get what im typing. Thats fine. I did say I set my toe at zero at 7" ride hieght.This was to sort the brain while watching bump guage. I dont know where I will end up setting static toe I will figure that after some testing.

Im sure the toe on a wrc could be 5mm in at ride height. Chances are its near zero or zero at full bump witch means its ganging TOE OUT. Im also sure there figuring where there toe is at insane full droop. Im not saying my car should have zero or what static toe.

Im saying what car builders want the toe to do during travel. You know what its doing ALL the time while driving. Im sure me and all the other articles could be wrong just dont keep mixing static toe with what the tire does in travel. The articles I was searching were for baja trucks. I figure they will have there shit sorted better then the zero info you can find on rallycars. Paul could post some Citron set up sheets so maybe we could learn soemthing. Im sure there for the machanic not the engineers that designed the susp.

This is what this is for to sort out the shit so we can all go faster.

OK, and that is what Paulino had in mind when he started the thread: Look at what way cool stuff is, compare what we have and then look at the numbers and designs..compare and contrast..

And I know he's as frustrated as I am with all the auto-cross bullshit where the idiots spring their cars so stiffly that vey likely the only compliance they get is from bodyshell torsional twist (bearing in mind that many of the fools have stock bodyshells with no cage, or a bolt in junk Auto-powerz shit that does nothing to stiffen the shell) So those fools can set the non-moving suspension and then wank forever about it.
Our suspension moves a whole lot constantly, and as you show, some stuff moves around a shock about..
I'll post up a whole slew of old Ford Group A stuff...cause some of that is close to production---unlike cars built under the World rally Car rules where everything is purpose built and perfected.
First I have some cleaning to do.

Re: Advanced Suspension Geometry and Design

Reamer — Sat, 22 Mar 2014 11:29:20 -0500

You guys just dont get what im typing. Thats fine. I did say I set my toe at zero at 7" ride hieght.This was to sort the brain while watching bump guage. I dont know where I will end up setting static toe I will figure that after some testing.

Im sure the toe on a wrc could be 5mm in at ride height. Chances are its near zero or zero at full bump witch means its ganging TOE OUT. Im also sure there figuring where there toe is at insane full droop. Im not saying my car should have zero or what static toe.

Im saying what car builders want the toe to do during travel. You know what its doing ALL the time while driving. Im sure me and all the other articles could be wrong just dont keep mixing static toe with what the tire does in travel. The articles I was searching were for baja trucks. I figure they will have there shit sorted better then the zero info you can find on rallycars. Paul could post some Citron set up sheets so maybe we could learn soemthing. Im sure there for the machanic not the engineers that designed the susp.

This is what this is for to sort out the shit so we can all go faster.

Re: Advanced Suspension Geometry and Design

john vanlandingham — Fri, 21 Mar 2014 21:56:34 -0500

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Cosworth

Quote
simoniac
I believe the toe-out mantra in the cone crushing crowd is derived from the theory that they're almost always turning and hardly ever going in a straight line (and never at speed). So toe-out on a loaded rear wheel actually means that you're asking that rear wheel to do a little steering for you.
You're right Simon, this idiocy of doing toe out is specifically related to the lower speeds they run at. Less speed means less weight transfer for turn in rotation.

As for rally, I have some Citroen setup sheets that calls for 5mm toe in at the back of the C2 R2Max and DS3 R3T.

The idiocy is unfortunately multiplied by the fact that those type of guys write endlessly of it and like a disease it has spread and infected a Continent, and they are too full of themselves and their 32 classes so everybody is a wiener sport that they forget that it is not something that Moses brought down from the mountain carved in stone tablets....

Paulino mio, do you know what bushes or what those car listed had in their links?

Re: Advanced Suspension Geometry and Design

Cosworth — Fri, 21 Mar 2014 20:40:49 -0500

Quote
simoniac
I believe the toe-out mantra in the cone crushing crowd is derived from the theory that they're almost always turning and hardly ever going in a straight line (and never at speed). So toe-out on a loaded rear wheel actually means that you're asking that rear wheel to do a little steering for you.

You're right Simon, this idiocy of doing toe out is specifically related to the lower speeds they run at. Less speed means less weight transfer for turn in rotation.

As for rally, I have some Citroen setup sheets that calls for 5mm toe in at the back of the C2 R2Max and DS3 R3T.

Re: Advanced Suspension Geometry and Design

Reamer — Fri, 21 Mar 2014 18:11:06 -0500

Im sure it is in cone crushing also. These numbers I got came straight from an engineer who developed the rear susp on Higgins 2013 car. I finaly talked to some body there that was willing to tell a few secrets. I guess seeing there now working on the 2015 car they dont care so much about there old stuff. They even got some used susp at a not so bad price considering there so much new.

Re: Advanced Suspension Geometry and Design

simoniac — Fri, 21 Mar 2014 17:07:43 -0500

I believe the toe-out mantra in the cone crushing crowd is derived from the theory that they're almost always turning and hardly ever going in a straight line (and never at speed). So toe-out on a loaded rear wheel actually means that you're asking that rear wheel to do a little steering for you.

Re: Advanced Suspension Geometry and Design

Reamer — Fri, 21 Mar 2014 13:18:45 -0500

I had 1/8" static then it went to zero then to in 1/8". Not good. John im talking what the toe does in travel not staic at ride hieght. I agree when tires are light they dont do much. This is also when the issue im having creeps up the most. The tire was moving crazy amounts in the wrong direction. I was just posting a article on bump and what most car builder want there bump to be at. Nothing about static toe in or out.

I reset my toe to zero at 7" ride hieght then I moved the outer tie rod down 3/8" and got the numbers Vermont sports car told me I should be looking for. Its crazy how much 3/8" shim changes the hole charictoristic of how the wheel travels. The wheel now is going from 1/8" in at full droop to about .40 out at full compression. It barely moves the guage from 7" to full compression.

Re: Advanced Suspension Geometry and Design

NoCoast — Fri, 21 Mar 2014 12:33:42 -0500

So you have 1/8 static toe, 1/8 more under compression. Sounds about right, maybe go zero static and see how that feels.

Re: Advanced Suspension Geometry and Design

john vanlandingham — Fri, 21 Mar 2014 12:28:30 -0500

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Reamer

Every thing ive read says you want zero to a little tow out to make the driver feel more stable on entry.

A LOT of what I have read ONLY IN AMERICA, and primarily from practitioners of the most useless glorified wank-off branch of motorsport where guys obsess about minute, pointless trivialities, and I am of course referring to amateur auto-cross and SCCA A-M "Improved Touring" say toe OUT.

Nowhere else anywhere do I see people blabbering incessantly about toe-out.
ONLY (well 99%) in the most amateur of amateur "sports" with the biggest wankers in all the world (as far as I can tell)..

Logically it makes no sense. Think of vectors...direction of force Car goes this way -------->
Force goes this way <------------ look at a RIGHT control arm in rubber from above represented by this 7I forward is ^ so force goes V , rubber moves and the arm goes into this 7 wheel goes from this I to this /

It naturally is going to toe OUT some... so set it IN at static unladen height and iit will move OUTWARD....do we need to set it OUT to begin with? No.

Besides another reason to discount the 99% of drivel written HERE, 90% written by girly-men auto-crossers is WE are not driving around in a parking lot at 20-35 mph.

Find RALLY-SPECIFIC information.....

Note: only time the suspension is at full droop is when the wheel are in the air...toe is pretty unimportant then, as is camber..

Worry about the toe and camber when stuff is in "the average position"---where it is 90% of the time. basically from static unladen ride height and maybe 5 inches UP....

Re: Advanced Suspension Geometry and Design

Reamer — Fri, 21 Mar 2014 10:02:38 -0500

I had a chance yesterday to check some bump steer on the rear susp. Not sure if this is my issue but it was going the wrong direction. My car was towing out 1/4" at full droop and towing in 1/8" full compression. This is per side so from 7" ride height to full compression it was towing in 1/4".

Every thing ive read says you want zero to a little tow out to make the driver feel more stable on entry.

Heres a article I found seems like a pretty good read

Bump Steer…it isn’t just Front suspension, it can be rear.