NASCAR Suspension

Anybody know the motion ratios for a Winston Cup car suspension? I have been playing around with setups in NR2003 and I am pretty sure that the roll couple calculation shown in the setup screen is way wrong. They appear to be using a front motion ratio of around 0.9 (spring motion / wheel motion) and a rear ratio of around 0.5, but the pictures I have seen of NASCAR suspensions seem to indicate that those two numbers should be reversed. Thanks in advance for any information you can provide.

Reversed sounds about right (0.5 front, near 1.0 rear). On Mon, 21 Apr 2003, Haqsau wrote:

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> Anybody know the motion ratios for a Winston Cup car suspension? I have > been playing around with setups in NR2003 and I am pretty sure that the roll > couple calculation shown in the setup screen is way wrong. They appear to > be using a front motion ratio of around 0.9 (spring motion / wheel motion) > and a rear ratio of around 0.5, but the pictures I have seen of NASCAR > suspensions seem to indicate that those two numbers should be reversed. > Thanks in advance for any information you can provide. > > > > >

Thanks. The reason I was looking into this is because the typical setup included with the game shows a roll couple of about 91% in the garage screen, and typical setups that I have downloaded show around 96%. I don't believe a car would be driveable with that much front roll stiffness, but I could be wrong. If I use motion ratios like the numbers you give they appear to be more like around the 75% to 80% range, which makes a lot more sense. "Doug Milliken" <[email hidden]> wrote in message news:[email hidden]... > > Reversed sounds about right (0.5 front, near 1.0 rear). > >

I motion that Jeff Gordon be suspended. "Haqsau" <[email hidden]> wrote in message news:b811ih$5748g$[email hidden]... > Anybody know the motion ratios for a Winston Cup car suspension? I motion that Jeff Gordon be suspended, but I don't know the ratio.. > been playing around with setups in NR2003 and I am pretty sure that theroll

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> couple calculation shown in the setup screen is way wrong. They appear to > be using a front motion ratio of around 0.9 (spring motion / wheel motion) > and a rear ratio of around 0.5, but the pictures I have seen of NASCAR > suspensions seem to indicate that those two numbers should be reversed. > Thanks in advance for any information you can provide. > > >

I'm pretty sure that the car would be drivable with 100% of the roll torque taken on the front wheels, but depending on weight distribution and other things it might push pretty badly... (and would be really tough to set up for a long run). Would be hard to get that configuration mechanically, the rear springs add some roll stiffness no matter how soft they are. I don't think that NASCAR would like to see anyone show up with just one rear spring over the center of the axle<grin>. 100% front has been tried (with other mechanical arrangements), in other kinds of race cars, sometimes quite successfully. All the above discusses the spring & anti-roll bar contributions ONLY (no discussion of roll-center height). On Mon, 21 Apr 2003, Haqsau wrote:

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> Thanks. The reason I was looking into this is because the typical setup > included with the game shows a roll couple of about 91% in the garage > screen, and typical setups that I have downloaded show around 96%. I don't > believe a car would be driveable with that much front roll stiffness, but I > could be wrong. If I use motion ratios like the numbers you give they > appear to be more like around the 75% to 80% range, which makes a lot more > sense. > > > "Doug Milliken" <[email hidden]> wrote in message > news:[email hidden]... > > > > Reversed sounds about right (0.5 front, near 1.0 rear). > > > > > > > >

Read - learn - fix - release. -- ed_ "Haqsau" said: > Thanks. The reason I was looking into this is because the typical setup > included with the game shows a roll couple of about 91% in the garage > screen, and typical setups that I have downloaded show around 96%. I don't > believe a car would be driveable with that much front roll stiffness, but I > could be wrong. If I use motion ratios like the numbers you give they > appear to be more like around the 75% to 80% range, which makes a lot more > sense. > > > "Doug Milliken" wrote: > > > > Reversed sounds about right (0.5 front, near 1.0 rear). > > >>>On Mon, 21 Apr 2003, Haqsau wrote: >>> >>> Anybody know the motion ratios for a Winston Cup car suspension? I have >>> been playing around with setups in NR2003 and I am pretty sure that the roll >>> couple calculation shown in the setup screen is way wrong. They appear to >>> be using a front motion ratio of around 0.9 (spring motion / wheel motion) >>> and a rear ratio of around 0.5, but the pictures I have seen of NASCAR >>> suspensions seem to indicate that those two numbers should be reversed. >>> Thanks in advance for any information you can provide.

The display in the garage is really more of what should be called "front roll stiffness distribution". Basically it's a measure of the percentage of roll stiffness of your suspension (as determined by spring and anti-roll bar selection) that comes from the front suspension. Unlike a true "roll couple distribution" measurement, this value is independent of roll center height (which in the game is fixed in the front, and adjustable in the rear via the track bar). - Eric "Ed Solheim" <[email hidden]> wrote in message news:1051022035.15073@gurney...

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> Read - learn - fix - release. > > -- > ed_ > > "Haqsau" said: > > > Thanks. The reason I was looking into this is because the typical

setup > > included with the game shows a roll couple of about 91% in thegarage > > screen, and typical setups that I have downloaded show around 96%.I > don't > > believe a car would be driveable with that much front rollstiffness, but > I > > could be wrong. If I use motion ratios like the numbers you givethey > > appear to be more like around the 75% to 80% range, which makes alot more > > sense.

That image brings up a good point - the motion ratio for the rear springs is not actually the same in roll as it is in vertical motion. In fact looking at a model I have, I would guess the rear springs have about a 0.5 motion ratio in roll, since they are mounted about halfway between the driveshaft and the tire centerline in rear view. The example case I am trying to match is with the front springs set to 700, rear to 300, and bars to 0. In the NR2003 garage screen this gives me a front roll couple of 85%. So now if the front motion ratio is 0.77 and the rear is 0.5 I get the same results as Papy. I can accept 0.5 for the rear based on the above considerations, but 0.77 doesn't seem right for the front, that would require fairly long arms and narrow tires, neither of which they have. "Doug Milliken" <[email hidden]> wrote in message news:[email hidden]... > > > Would be hard to get that configuration mechanically, the rear springs add > some roll stiffness no matter how soft they are. I don't think that > NASCAR would like to see anyone show up with just one rear spring over the > center of the axle<grin>.

That's what I thought front roll couple meant anyway. The thing I am trying to figure out is this: it has been widely said, even in Papy manuals (N4 manual for example) and online help, that one normally wants a front roll couple of 70% to 80%. Yet the Fast and Jasper setups are typically around 90% (according to the garage display), and some very fast setups that I have downloaded are more like 96%. Further, when I try to get down to even 80% I end up with spring and bar sizes that are very unrealistic. There is very good documentation of what typical spring and bar sizes are, both online and in the old N4 manual, and when I plug these in I am once again up in the 90% range, according to the garage display. I'm just trying to figure out where the disconnect is. I thought maybe it was due to motion ratios but now I'm not so sure. One thing that does not appear to be accounted for is the roll stiffness that is inherent to the rear suspension design. According to RCVD the rear trailing arms are attached solidly to the axle, which means the suspension assembly itself has some torsional stiffness in roll. Is this accounted for in the garage roll couple calculation? Is it accounted for in your handling model? If the answer to the first question is no and the answer to the second question is yes then it all makes sense. If not, then I think there is still a disconnect somewhere. "Eric Busch" <[email hidden]> wrote in message news:b84hvt$k77$[email hidden]...

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> The display in the garage is really more of what should be called "front > roll stiffness distribution". Basically it's a measure of the > percentage of roll stiffness of your suspension (as determined by spring > and anti-roll bar selection) that comes from the front suspension. > Unlike a true "roll couple distribution" measurement, this value is > independent of roll center height (which in the game is fixed in the > front, and adjustable in the rear via the track bar). > > - Eric

As I stated earlier, the real disconnect is that for NR2003 the value displayed in the box really isn't a measure of front roll couple. Front roll couple is dependent on roll stiffness, but it is also largely dependent on the front and rear roll center heights. The value displayed in NR2003's garage is not, and you can see this difference for yourself in the game. As you change the anti-roll bars and springs you'll see the displayed value change as expected, but if you change the track bar height (the front roll center is fixed) you'll see that it doesn't affect the displayed value at all. The recommended value is a holdover from NR2002 (it simply was never updated for NR2003), so don't worry too much that it doesn't match. For what it's measuring, it matches up quite closely with a real Winston Cup car. - Eric "Haqsau" <[email hidden]> wrote in message news:b86h5l$6rq7n$[email hidden]... > That's what I thought front roll couple meant anyway. The thing I amtrying > to figure out is this: it has been widely said, even in Papy manuals(N4 > manual for example) and online help, that one normally wants a frontroll > couple of 70% to 80%. Yet the Fast and Jasper setups are typicallyaround > 90% (according to the garage display), and some very fast setups thatI have > downloaded are more like 96%. Further, when I try to get down to even80% I > end up with spring and bar sizes that are very unrealistic. There isvery > good documentation of what typical spring and bar sizes are, bothonline and > in the old N4 manual, and when I plug these in I am once again up inthe 90% > range, according to the garage display. I'm just trying to figure outwhere > the disconnect is. I thought maybe it was due to motion ratios butnow I'm > not so sure. One thing that does not appear to be accounted for isthe roll > stiffness that is inherent to the rear suspension design. Accordingto RCVD > the rear trailing arms are attached solidly to the axle, which meansthe > suspension assembly itself has some torsional stiffness in roll. Isthis > accounted for in the garage roll couple calculation? Is it accountedfor in > your handling model? If the answer to the first question is no andthe > answer to the second question is yes then it all makes sense. If not,then > I think there is still a disconnect somewhere.

We like "Total Lateral Load Transfer Distribution (TLLTD)" for the combination of "springs/bars/aux-roll-stiffness" and "RCH effects". See RCVD page 679 (bottom)--avoids a lot of confusion. Auxillary roll stiffness might be, for example the windup of a NASCAR rear axle (acting like an anti-roll bar). -- Doug Milliken www.millikenresearch.com/olley.html <-- new book here On Wed, 23 Apr 2003, Eric Busch wrote:

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> As I stated earlier, the real disconnect is that for NR2003 the value > displayed in the box really isn't a measure of front roll couple. Front > roll couple is dependent on roll stiffness, but it is also largely > dependent on the front and rear roll center heights. The value > displayed in NR2003's garage is not, and you can see this difference for > yourself in the game. As you change the anti-roll bars and springs > you'll see the displayed value change as expected, but if you change the > track bar height (the front roll center is fixed) you'll see that it > doesn't affect the displayed value at all. The recommended value is a > holdover from NR2002 (it simply was never updated for NR2003), so don't > worry too much that it doesn't match. For what it's measuring, it > matches up quite closely with a real Winston Cup car. > > - Eric > > > "Haqsau" <[email hidden]> wrote in message > news:b86h5l$6rq7n$[email hidden]... > > That's what I thought front roll couple meant anyway. The thing I am > trying > > to figure out is this: it has been widely said, even in Papy manuals > (N4 > > manual for example) and online help, that one normally wants a front > roll > > couple of 70% to 80%. Yet the Fast and Jasper setups are typically > around > > 90% (according to the garage display), and some very fast setups that > I have > > downloaded are more like 96%. Further, when I try to get down to even > 80% I > > end up with spring and bar sizes that are very unrealistic. There is > very > > good documentation of what typical spring and bar sizes are, both > online and > > in the old N4 manual, and when I plug these in I am once again up in > the 90% > > range, according to the garage display. I'm just trying to figure out > where > > the disconnect is. I thought maybe it was due to motion ratios but > now I'm > > not so sure. One thing that does not appear to be accounted for is > the roll > > stiffness that is inherent to the rear suspension design. According > to RCVD > > the rear trailing arms are attached solidly to the axle, which means > the > > suspension assembly itself has some torsional stiffness in roll. Is > this > > accounted for in the garage roll couple calculation? Is it accounted > for in > > your handling model? If the answer to the first question is no and > the > > answer to the second question is yes then it all makes sense. If not, > then > > I think there is still a disconnect somewhere. > > > >

Manuel Daskalos of Jasper Motorsports had suggested displaying the arguably more useful front LLTD percentage, but unfortunately it was never implemented for NR2003. - Eric "Doug Milliken" <[email hidden]> wrote in message news:[email hidden]... > > We like "Total Lateral Load Transfer Distribution (TLLTD)" for > the combination of "springs/bars/aux-roll-stiffness" and "RCHeffects". > See RCVD page 679 (bottom)--avoids a lot of confusion. > > Auxillary roll stiffness might be, for example the windup of a NASCAR > rear axle (acting like an anti-roll bar).

I would say it depends on your driving style and what the rest of your set-up is. I can tell you that some drivers in Winston Cup run big front bars and some run smaller front bars. I would say as a rule of thumb a roll gradient between .9 and 1.2 degrees is a resonable range. RSD numbers typically range from 82% on the softside and 88% on the highside. Alot of your FARB selection depends on you spring selection. Your spring selection depends on several factors such as track surface, aerodynamic pitch attitude and some but to a much lesser extent RSD, and fore/aft and squash wedging concerns.

To add to my earlier comments, the rear truck arms add to the effective roll stiffness of the rear of the car. The only data I have seems to suggest it is about 20 percent of the rears total roll resistance. This changes depending on what style of connection you use for your truck arm bushings (monoballs, small rubber bushings or big rubber bushings). It is true that LLTD is a more encompassing element of the cars handling. WC stock cars being panhard bar solid axle rear end cars have the distinction to having a large percentage on their roll stiffness distribution being to the front. This is of course is due to the high roll center position in the rear. In other words, most of the weight transfer across the front end is across bars and springs where as most of the weight transfer across the rear is across the solid geometry of the rear panhard bar. Therefor, RSD is not a tell tale sign of overall LLTD. In fact, it goes to show you why large bar changes often result in a very little change in actual balance of the car(although they do offer transient handling and driver feel changes). In my experience, typical dynamic LLTD values occure around -1% to +3 percent of the nose weight percentage value.

Typical motion ratios vary depend on how a given team decides to mount their spring buckets and shock mounts in the front. But in general these are the numbers that I see commonly on different cars that have been roamed. In ride: LF spring .54, RF spring .51, Rear springs .85 Front shocks .75 Rear shocks 1.05 In roll: front sway bar .785 rear springs (35" spread) front springs (IFS calcs) rear shocks .585 These can vary depend on different styles of cars, car parts and geometry styles.