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Ride Heights


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Poll: Ride Height Poll (64 member(s) have cast votes)

What ride height do you typically run? (inches)

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#1 John Woods

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Posted Mar 04 2014 - 01:27 PM

Lately interest in how ride height effects performance and handling led to finding modern F1 cars typically sit at about 32mm front and up to 100mm at the rear. No doubt aero is big factor with this much rake.

Known for awhile 67s were running up in range of 3.5in to maybe 5in?
But why? Easy sailing over bumpy roads?
What performance and handling benefits might be available when tuning ride height on non-aero cars?
Also note from photos of the period regardless of chassis ride height the bodies of formula cars often appear very low to the ground and have very little rake.

How is ride height tuned for performance and handling?

#2 Lee200

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Posted Mar 04 2014 - 03:35 PM

General answer is simple.  The lower the ride height, the better the performance as that lowers the CG.

GPL doesn't model actual bumps so as long as the car doesn't bottom out on jumps, go as low as you can.

Real world cars have to take into account road bumps and dips so they may have to ride higher.

Edited by Lee200, Mar 04 2014 - 03:36 PM.


#3 David Wright Lo67

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Posted Mar 04 2014 - 03:41 PM

Racing cars of this period had soft suspension.  This requires a high ride height if you don't want the cars to bottom.  The wisdom was softer springing gave more grip.  This may have been in the context of bumpier tracks than are the norm today.  Downforce is also a key factor behind suspensions getting stiffer after this period.

Fuel had a noticeable effect on the ride height.  Ride height would vary by about an inch from full tanks to empty.  So you might start a race with a 3" ride height and finish it with a 4" ride height.  Also the forward location of the fuel relative to the centre of gravity meant that the cars would have more rake at the start of the race than at the end.

Edited by David Wright Lo67, Mar 04 2014 - 03:49 PM.


#4 Lee200

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Posted Mar 04 2014 - 03:47 PM

David, that is my understanding too.  Softer springs allow the suspension to be more "compliant" which means that the tire stays in better contact with the road surface.  After all, a tire off the ground provides no grip at all!  :)

And certainly the road circuits and even tracks of years ago were more bumpy that what F1 has today.

#5 John Woods

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Posted Mar 04 2014 - 04:29 PM

Thinking the poll should have spec'd front and rear check boxes. Just thought of that.
So why in Grand Prix Legends go higher than 2.5in F/R?
Lately been experimenting all over the place and as usual don't know what's happening.

Edited by John Woods, Mar 04 2014 - 04:34 PM.


#6 Pete Gaimari

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Posted Mar 04 2014 - 05:41 PM

When looking at the real cars you'll see the half shafts are level with the ground. I setup all my cars to look like that. I see very little difference in lap times no matter how the ride height is set. So, I go for what looks proper, and keeps the car from bottoming out. Which btw doesn't have to be off jumps.

Depending on the car, it will be 3.25-3.75.

#7 Michkov

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Posted Mar 04 2014 - 11:57 PM

In GPL I usually run as low as I can get without too much bottoming out under uphill passages.
In reality though you want to run the cars a bit further of the ground due to bumps, the soft suspensions also physical limitations. The Eagles upper wishbones go through the exhausts if you run it in the lowest rear height in GPL for example. Another reason for running higher ride height is to give the air more space between the car and ground. So raising the height should make you faster as the drag would decrease. I haven't tried this yet with the 66 or 69 mod yet

#8 Fat Rich

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Posted Mar 05 2014 - 03:47 AM

When GPL first came out you could run the cars really low, about 1" if I remember correctly. But they patched it to stop people exploiting it, the cars handling was horrible and unpredictable because sometimes you were on the springs, sometimes the bump rubbers. Fast though.

On smooth flat circuits like Monza I'll run pretty low with smaller bump stops, but if I go too low I seem to lose traction presumably because the suspension bottoms out. I'll jack the car up for circuits like Nurburgring and Monaco, softer damping too to try and keep the wheels on the ground when the car goes light over crests.

Maybe the hotlappers don't bother and just run the car as low as possible?

Edited by Fat Rich, Mar 05 2014 - 03:47 AM.


#9 Saiph

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Posted Mar 05 2014 - 06:26 AM

I'm a hotlapper (and TotalRanker)  mainly, and I voted for 3.0-3.5 inches. I like a car to feel consistent at all tracks, so I tend to find a single setup which works everywhere, perhaps with some adjustment to the gearing for very fast or slow tracks. There are some nasty bumps at some tracks which can catch you out and put you in a spin, so despite the fact that I like stiffer setups for responsiveness, I run a little added ride height (Edit: and higher bump rubbers) to avoid grounding. Obviously at unusual tracks such as Avus, with the banked turn, I have to make extra adjustments, but generally stiff springs and dampers, with a little extra ride height suits me fine at most places.

At smoother tracks I have tried running as low as possible to see if it helped my handling and lap times, but to be honest I didn't find any perceptible difference, so I reverted to my normal setups.

Edited by Saiph, Mar 05 2014 - 06:27 AM.


#10 John Woods

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Posted Mar 05 2014 - 09:34 AM

Spent some time this morning looking for ride height tuning tips. Here's some links and quotes from this very incomplete search. (Sites are for circle trackers and one for simracers).

http://www.merlinpp....height-info.php
The ride height affects the role center, which in turn determines how the weight will move. Accurate setting of the ride height keeps this dynamic transfer predictable and consistent.

http://www.circletrack.com/chassistech/ctrp_1009_setting_ride_height_and_corner_weight/
So, ride heights in the front are more critical for maintaining camber angles.

http://needlesslyobs...e-height-right/
The biggest hammer in our toolbox for setting the car’s behaviour is its ride height.

Tuning understeer balance with rake

Now we know that we want to get the car as close to the ground as possible, but what about using ride height to tune car behaviour?  Looking at our five points above, we see that the first two are affected by the car’s ride height as a whole, but the last three are relatively independent at the front and rear of the car.  Thus, we should lower the end of the car we want to stick.  If there’s too much understeer, lower the front; if there’s too much oversteer, lower the rear.  (This is all relative, of course; if we have too much oversteer but the rear’s as low as we can get it without scraping the track, we can achieve the same effect by raising the front.)  The height of the rear suspension relative to the front is called rake — positive rake means that the car’s nose is pointed down; negative rake is the opposite.

Changing the rake of the car also affects its centre of gravity; increasing rake moves the CG slightly forward, putting more load on the front wheels.  Once again, this increases relative grip at the front of the car, decreasing understeer (or increasing oversteer, if you prefer).

http://www.racelinec...SetupGuide.html

A. The higher the CG is above the ground the more weight will transfer to the outside tires in a corner...Raising or lowering the CG can impact suspension geometry such as rear axle steer or camber gain in the front suspension.

B. Let the front roll center fall where it may in order for the front suspension to have good camber curves. Use the rear roll center to tune your race car's handling. Elevating the rear roll center tends to make the car looser (overseer) in the mid portion of the corner when the centrifugal force is highest.

#11 Fat Rich

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Posted Mar 05 2014 - 11:56 AM

View PostJohn Woods, on Mar 05 2014 - 09:34 AM, said:

Tuning understeer balance with rake

Now we know that we want to get the car as close to the ground as possible, but what about using ride height to tune car behaviour?  Looking at our five points above, we see that the first two are affected by the car’s ride height as a whole, but the last three are relatively independent at the front and rear of the car.  Thus, we should lower the end of the car we want to stick.  If there’s too much understeer, lower the front; if there’s too much oversteer, lower the rear.  (This is all relative, of course; if we have too much oversteer but the rear’s as low as we can get it without scraping the track, we can achieve the same effect by raising the front.)  The height of the rear suspension relative to the front is called rake — positive rake means that the car’s nose is pointed down; negative rake is the opposite.

I think this is particularly true on modern race cars where the front wing or splitter will work significantly better if it's close to the ground, similarly rear diffusers work better close to the ground too. And the rake of the car helps create low pressure under the cars, which is why skirts worked so well because they stopped the air getting in at the sides - instant suction. However on a cigar shaped 60s car I think the rake / ride height will have far less effect.

View PostJohn Woods, on Mar 05 2014 - 09:34 AM, said:

Changing the rake of the car also affects its centre of gravity; increasing rake moves the CG slightly forward, putting more load on the front wheels.  Once again, this increases relative grip at the front of the car, decreasing understeer (or increasing oversteer, if you prefer).


I think this is utter nonsense unless your car is five storeys high! I could try to do the maths and work out just how much further forward the centre of gravity will go by increasing the rake of the car, it would be fractions of a millimetre. As an example, if you take a 12" ruler, stand it on it's end then tilt it somewhat, the centre of gravity will indeed move forward by a useful amount. However, lay the same ruler down length ways and lift one end a few millimetres, there's no way the centre of gravity moves much and you can test that by balancing it a pencil and giving it a tilt.

Some interesting stuff about camber changes though.

Edited by Fat Rich, Mar 05 2014 - 11:58 AM.


#12 John Woods

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Posted Mar 05 2014 - 03:52 PM

Does positive rake, (nose lower), make weight transfer/CG toward front "easier" and transfer to rear "less easy"? (Like forward is downhill and to the rear is uphill)?

#13 Fat Rich

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Posted Mar 06 2014 - 03:53 AM

View PostJohn Woods, on Mar 05 2014 - 03:52 PM, said:

Does positive rake, (nose lower), make weight transfer/CG toward front "easier" and transfer to rear "less easy"? (Like forward is downhill and to the rear is uphill)?

Pretty negligible effect I would think unless you've got a very top heavy car,  you'll get better results adjusting the dampers and springs.

A very top heavy car:



The only reason I can think for suggesting the CG moves forward significantly with more rake is that is what it feels like, more grip at the front (in an aero car) less at the back.  I think Indycar and Nascar can actually move weight around if I'm understanding Weight Jacking correctly, then they probably adjust ride heights as part of that new weight distribution to keep the car pitched the way they want. But oval racing and setups aren't something I know much about.

#14 John Woods

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Posted Mar 06 2014 - 02:13 PM

Top Gear's example of a ruler stood on end?
;)

Just spent a few minutes here checking out suspension geometry animations:http://www.racecartuner.com/

Plus found this earlier, which is copied to notepad from somewhere, (will try to remember...its about setting up Spitfires for performance handling, (hahaha), but maybe applies to roll centers and roll axis in general?):

"Some lowering and stiffening is good, but too much makes things worse. Too much lowering generates poor suspension geometry that lowers the roll center too much, thereby lengthening the lever arm between the roll center and the c.g. to increase the roll moment that increases lateral weight transfer due to body roll and increases changes in suspension geometry to actually make handling worse (note however that simply reducing overall wheel/tire diameter beneficially lowers the c.g. and roll centers without changing the linkage geometry). Moreover, too much lowering leaves inadequate ground clearance for everyday use. Too much stiffness actually reduces grip and makes for an uncomfortable ride. Too much change in stiffness at one end of the car relative to the other, or stiffness not matched to the static weight distribution of the car, will lead to excessive understeer or oversteer. The right amount of lowering and stiffening can optimize the geometry of the suspension links so that the car transfers less weight for a given amount of roll, as well as rolls less in response to a given set of forces to help maintain better tire geometry for good grip."

Edited by John Woods, Mar 06 2014 - 02:18 PM.


#15 John Woods

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Posted Mar 07 2014 - 03:52 PM

Okay, I'm going long...

Imagine the center of gravity of a car. For GPL cars, this is nominally 12in above the track surface and for the 67 Lotus approximately down below the driver's roll bar...a little forward of that with fuel and driver.
Imagine the longitudinal roll axis, which is a tune-able line between the front and rear suspensions.
Now imagine a vertical line thru the CG that intersects the roll axis. This line represents a lever and fulcrum action between the roll axis and the CG that occurs dynamically when the car is in motion.
There is a perfect length to this line, which when a car is tuned to it the car will behave very well, because the weight proportional lever will effect the front and back the same way. If the line is too long, (big lever and roll axis set too low), the tub will roll too much. If too short, (little lever and axis too high), it will not roll enough.
If the roll axis inclines with rear higher than the front, the rear will feel tight to the driver.
When the pivot line is too long, the car will pitch and squat too much or too little depending on which end of the car is of interest.

Editorial request: Please insert question mark in place of every period, especially the last few sentences. Thanks.

#16 Pete Gaimari

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Posted Mar 07 2014 - 06:07 PM

You're missing the point John. We're simulating a 67 F1 car in GPL. Should we make the car what it wasn't, or should we drive the car as it was, and do the best we can with it?

I choose the latter.

#17 Fat Rich

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Posted Mar 08 2014 - 04:06 AM

View PostJohn Woods, on Mar 07 2014 - 03:52 PM, said:

Editorial request: Please insert question mark in place of every period, especially the last few sentences. Thanks.

??????????????????????????? :P ;)

View PostJohn Woods, on Mar 07 2014 - 03:52 PM, said:

......There is a perfect length to this line, which when a car is tuned to it the car will behave very well, because the weight proportional lever will effect the front and back the same way. If the line is too long, (big lever and roll axis set too low), the tub will roll too much. If too short, (little lever and axis too high), it will not roll enough......


I'm sure you always want it as short as possible. Having the CG too high and the car rolling around uses up suspension travel that could be dealing with bumps and risks putting the car on the packers which would equal a big loss of grip. The only reason to raise the ride height in a racing car is to keep it off the packers in braking and acceleration zones, or to stop it bottoming out on track (and with an aero car it's even more important to keep the ride height as constant as possible and in the zone where the floor and diffusers do their thing most efficiently). Also your information about ride height affecting camber is well worth looking into too, more modern racing cars are designed to run lower but I would think they knew about that kind of thing by the late 60s and designed the suspension geometry to cope with low ride heights.

View PostJohn Woods, on Mar 07 2014 - 03:52 PM, said:

If the roll axis inclines with rear higher than the front, the rear will feel tight to the driver.


I would expect the rear of the car to feel looser, but generally on our GPL cars I'd be surprised if you feel much difference adjusting the rake. It's something that works well with flatter bottomed cars as it turns the whole car into a giant venturi and can also affect the aerodynamics of the top of the car in a good way. But our cigar shaped cars are exactly the wrong shape for that, the air easily rushes around the radiused sides so there's no chance for low pressure to form. Plus I'm pretty sure I read somewhere these old cars actually generated a little bit of lift at high speeds.

Edited by Fat Rich, Mar 08 2014 - 04:14 AM.


#18 John Woods

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Posted Mar 08 2014 - 10:51 AM

Hey Pete, Howdy Howdy,
Well...so, Saturday morning. Not much to do. Thanks for the tee-up.
;)

Taking your comments one-by-one:
1. I have a point? Guessing others agree too often seems more like a dim bulb with random occassional gone-off blinding flashes of micro-speck intergalactic brilliance that no one understands, especially me. (Remember the GPL Time Analog Clock Emulator? Whoa-boy was that fun).
2. Simulating? In my fantasy world driving a GPL car is as real as it gets. "IT IS REAL!," (as on-line racers like to remind us all).
3. Drive the car as it wasn't or was? Got me there...had to think about that a bit.
Here's the problem with making those kind of choices, in my view. First, we don't know what it was, (the more I learn about the hands-on experts, the more I think they didn't know a whole lot back then either. After all, with every new car and new season they were starting from scratch). Second, we don't know what it is and are not sure what happens when we tweak things. Third, all we have to go on is guesses about what it was and guesses about what it is, so we have no choice but to rely on theory and the math about our guesses about what things were compounded by theories, math, and guesses about what things are.

Haven't we agreed on those points before?

So the two choices I see are, drive the default setups and don't worry about it, or my preference, suffer endless confusion and error trying to figure it all out.

Fat Rich,
Yes, agee the line should be short as when it is too long it weirds everything out, and understand that in theory the perfect roll axis should be horizontal, should intersect the CG at the mid-point between the front and rear roll centers, and the levers should apply same force to all four wheels. But as I understand, this practically never happens, the CG is never at the mid-point, the levers to the front and back are never equal, and the roll axis is never flat.
So I was thinking, (or still guessing), when the rear roll center is too much higher than the front, the rear will roll less, making the car tight even tho, as you state, it may feel loose, (still not sure about this), because the front is rolling more?

Edited by John Woods, Mar 08 2014 - 10:52 AM.


#19 Pete Gaimari

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Posted Mar 08 2014 - 11:00 AM

Well, in no way am I suggesting to drive the default setups. They have no more meaning than using beta testers lap times for the GPL rank.

This thread is about ride heights. This is something we can compare to the real cars by looking at the half shafts. Set them level with the ground, and we are close to what the real cars used.

#20 Fat Rich

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Posted Mar 08 2014 - 11:21 AM

View PostJohn Woods, on Mar 08 2014 - 10:51 AM, said:

......

Fat Rich,
Yes, agee the line should be short as when it is too long it weirds everything out, and understand that in theory the perfect roll axis should be horizontal, should intersect the CG at the mid-point between the front and rear roll centers, and the levers should apply same force to all four wheels. But as I understand, this practically never happens, the CG is never at the mid-point, the levers to the front and back are never equal, and the roll axis is never flat.
So I was thinking, (or still guessing), when the rear roll center is too much higher than the front, the rear will roll less, making the car tight even tho, as you state, it may feel loose, (still not sure about this), because the front is rolling more?

I think you're over thinking this stuff when talking about levers and roll axis directions and whether they're level or not, it's making my head go squirrelly (like when I read your V.R. Metaphysical Aesthetics :dontgetit: :) ). Also the balance of the car shouldn't change that much when one end of the car is higher than the other unless chassis flex is calculated in GPL's physics engine, even then I think it would be minimal

On a car without a flat bottom (ground effect out of the equation) it's probably fine just to get everything as low as possible. Springs, dampers and roll bars (sway bars if you prefer) will have much more effect on the handling of the car. I just use the ride height to raise the car a little on bumpy / jumpy tracks like Nordschleife to keep the car off the bump rubbers where possible.

But if increasing the rake of the car makes you go faster, that's all that matters! :up:

I couldn't feel any difference.

Edited by Fat Rich, Mar 08 2014 - 11:22 AM.





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