The spring rates we set in the garage. We know the mass on the spring, so we know the spring frequency. The wheelrate may well be lower than the springrate, but the basic frequency will remain. So you can still tune by frequency (since it is a more meaningful than spring or wheel rates).

Quote from Bob Smith :

The spring rates we set in the garage. We know the mass on the spring, so we know the spring frequency. The wheelrate may well be lower than the springrate, but the basic frequency will remain. So you can still tune by frequency (since it is a more meaningful than spring or wheel rates).

Now this may be a shot in the dark, but I have followed racing for a looooong time, and one thing that sticks in my head, is that theres a rough formula that either 0.25lbs of air pressure is the equilivant of 25lbs of spring rate or a full pound, not 100% sure. But either way, there is something to this. Has anyone seen air pressure alter any of the graphs in F1perf? Or the *.xls sheets? I still havent figured out all the areas in either of those 2 areas, but if I do I will see if it holds merit.

A tyre can be thought of as a spring (or rather lots of springs), and yes increasing the air pressure inside the tyre will stiffen it. Essentially suspension is really a dual-system combination between spring compression and tyre flex, but that gets complicated. On road cars it no so much of an issue, but on Formula style cars it gets more important since the tyre is providing much more of the give than the springs are.

In short tyres are bloody complicated, construction and pressure affects stability, grib, heating, wear, etc, so it's just something you have to play with.

Oh there are some graphs about on this forum somewhere showing how pressure affects grip.

Quote from Bob Smith :

The spring rates we set in the garage. We know the mass on the spring, so we know the spring frequency. The wheelrate may well be lower than the springrate, but the basic frequency will remain. So you can still tune by frequency (since it is a more meaningful than spring or wheel rates).

But we don't know the sprung and unsprung weights.

Yes we do. Available from RAF outputs.

Quote from Bob Smith :

http://www.teamassociated.com/ ... arc/Handling.5.html#34216

What are D1 and D2 in the diagram in the link above? I don't think we can get those distances easily.

d1 - bodymount to springmount
d2 - bodymount to wheelmount

which means the quotient is 1 on all the cars lfs has to offer so we might just as well forget about it

Quote from Shotglass :

d1 - bodymount to springmount
d2 - bodymount to wheelmount

which means the quotient is 1 on all the cars lfs has to offer so we might just as well forget about it

Do we need this if we know the SAI tho?

sai is short for ?

Steering Axis Inclination

or the angle of the strut from vertical for the layman. McPherson strut anyway. Angle of the upright for double wishbone.

How does the SAI affect the springs? I would imagine more inclination makes stiffer springs? But then does that also affect frequency?

(yes, I sometimes ask setup questions too )

Forgot to post my findings so far. Had GTR at Westhill, was running about 2:02.xx. Had GearRatCalc, 1 *.xls spread converted to work with the car, a hot lap analyzed by F1perf Calc, and now run consistent 1:35.xx laps over 10 laps or so. I believe the top time is 1:29.xx, and I think the rest is patience, practice, and luck. Took awhile to figure it all out, but after I made the changes suggested by all the programs, it was about the 2nd lap the times plummeted.
Good work to you guys who made all those little progs. Outstanding that they helped the way they did.

PS Bob, based on the graph in your Adv Setup Guide, if Im setting the clutch pack power at 38%, am I wasting power under acceleration? Should I finess the throttle a tad bit more?

Quote from Bob Smith :

How does the SAI affect the springs? I would imagine more inclination makes stiffer springs? But then does that also affect frequency?

(yes, I sometimes ask setup questions too )

higher spring angle = less compression per wheel movement = easier to compress

Quote from MagicMarker27 :

PS Bob, based on the graph in your Adv Setup Guide, if Im setting the clutch pack power at 38%, am I wasting power under acceleration? Should I finess the throttle a tad bit more?

Well, so long as the inner tyre never turns red in forces view under power, more power locking won't improve acceleration. I think with the GTRs I run around 50% myself. But of course there's no point going all out for being able to put the power down, if you can't handle the car. Making setups isn't just about extracting the maximum potential from the car, but about making you get as much from the car as you can.

Quote from Shotglass :

higher spring angle = less compression per wheel movement = easier to compress

That's right, as you lean the upright over the effective rate of the spring (and therefore frequency) increases. Also the distance between the hub and the upright in the vertical plane affects effective spring rate and therefore frequency.

I've got the equations in my book (race and rally sourcebook by staniforth) at home. Let me know if you want me to post an example.

Quote from Bob Smith :

Well, so long as the inner tyre never turns red in forces view under power, more power locking won't improve acceleration. I think with the GTRs I run around 50% myself. But of course there's no point going all out for being able to put the power down, if you can't handle the car. Making setups isn't just about extracting the maximum potential from the car, but about making you get as much from the car as you can.

I like your way of thinking.

Let me see if I understand it correct though. If I drop the torque lock up as low as it will go, then the rear end will lock up almost instantly with wheel spin, and the higher number means I could loop the car and both tires will never lock up. Just want to make sure Im going the right way, and Im a tad bit lazy right now to start the game and check the views. :tired: Long day of work and sailing.

Yes, with a low power lock, it will be very easy to spin one wheel under power, and acceleration will be reduced. With a high power lock, it will be difficult to spin one wheel, but when a wheel does spin, it is more likely to be both of them (which could cause a slide).

The additional force on one side of the vehicle provided by a high power lock will also help push the vehicle round.

That's why road cars, if they have an LSD, have limited locking. Even on a track car I reckon anything over about 75% power locking is gonna make for some interesting moments on the exit of corners - rwd anyway.

Quote from Gentlefoot :

That's why road cars, if they have an LSD, have limited locking. Even on a track car I reckon anything over about 75% power locking is gonna make for some interesting moments on the exit of corners - rwd anyway.

Well, being a type "A" personality, things like that entice me. You'd be suprised at the things I've done with our version of your Lorrys'...

Quote from Bob Smith :

Yes, with a low power lock, it will be very easy to spin one wheel under power, and acceleration will be reduced. With a high power lock, it will be difficult to spin one wheel, but when a wheel does spin, it is more likely to be both of them (which could cause a slide).

The additional force on one side of the vehicle provided by a high power lock will also help push the vehicle round.

See, I did understand this backwards. I thought lower %'s meant that was the percentage the "other" wheel had to spin before the lsd would catch the other. My version would have meant that @ 50 Mph and 75%, the inside tire would need to be turning 37Mph slower than the outside before lock up would occur. 25% would need about 12 Mph.

Yeah - the percentages generally refer to the amount of locking. i.e. a 75% locking diff will allow 25% of slip.

So the balancing act is between traction on exit of corners and snatchy power oversteer. You'd probably want to avoid a high locking % when the important corners on the track have maybe a slight dip on the exit that encourages the rear wheels to spin up.

Quote from Gentlefoot :

That's why road cars, if they have an LSD, have limited locking. Even on a track car I reckon anything over about 75% power locking is gonna make for some interesting moments on the exit of corners - rwd anyway.

I've read cars at Le Mans use 60/40 (power/coast) - although which class I'm not sure. That's the highest figures I've ever seen in use (ignoring locked diffs in certain styles of racing).

I almost bought a Kaaz plate diff for my Golf but I couldn't get hold of one in the end and bought a Quaiffe ATB instead. The Kaaz had 70% locking! I guess you can get away with higher lock on FWD

But yeah - I believe Le Mans cars would want to 'soften' the settings a bit baring in mind the length of stints the drivers do and the risk of coming across a slower car if you're in an LMP1

btw I know oval racers who weld up their open diffs! 100% lock but damn cheap.

I used to run my FZR with a 40/80 split. But then I was a mouser so I needed the exit control and the engine braking.

I raced the FZR pretty much exlusivly and the setups I got for it where pretty nuetral to cope with the Mousing aspect. What I did find with it was that it was very susceptable to tyre pressure differential. If the front pressure was higher than the rear you had a more controllable rear but less stopping power. Lower front pressure you got more stopping power (Increases contact patch) but a much more twitchy rear.

I was still working on the the new patch suspension settings when I had to give up racing so I can't really add anything useful there. But from memory I used to run a fairly soft rear with bump emphasied on the front to keep the rear from stopping out. Again Anti-roll with the new patch still needed a bit of looking at but I did generally run more anti roll on the front that on the rear. Quite alot more. But then that as also track dependant. Ast-Nat I was running 100-50 front rear split on the anti-roll.

Also with mousing I had the rear toe-in dialled up to keep the arse from stepping out under power. But I was finding that I was taking that out gradually with the new patch.

Just another little observation--for my rally sets, I use a full 80% power lock and very little coast lock--only 10-15%. This is basically what you want for drifting, if any drifters are reading this. High power lock means that, once the rear wheels break loose, holding the throttle down will keep them spinning (the opposite extreme, an open diff will always prevent at least one wheel from spinning). Low coast lock means that easing off the throttle will quickly stop the drift and get you back under control.

The disadvantage of course is that the broad range of locking makes the car sensitve to slight throttle changes. If you can't control the car upon releasing the throttle, increasing the coast lock can make it easier.

Quote from Gentlefoot :

Yeah - the percentages generally refer to the amount of locking. i.e. a 75% locking diff will allow 25% of slip.

So the balancing act is between traction on exit of corners and snatchy power oversteer. You'd probably want to avoid a high locking % when the important corners on the track have maybe a slight dip on the exit that encourages the rear wheels to spin up.

In your opinon, if Im running Blackwood Gp in the FZR with a lsd set at 40/60, what am I expecting? When I had it at 50/80 I could not turn easy, such as the end of the back straight. Also in that corner under braking, the car would not turn. I have run many many laps there, and have had it set at 50/80 and can turn 1:08.xx laps pretty regularly. All things being equal, including my driving, what would say 20/40 lead to? Or 70/30? Having to modulate the throttle more while exiting or accel. away from the apex? I have seen what the hotlap sets are, and can not get a handle on the locks. I know Bob always says run what makes it comfortable to drive, and I have, even understanding what subtle changes in the rebound and bumps have done for cornering grip. Is it really just a lack of experience that I cant run 1:06.xx on that track, or is it more along setups still? I also run about 9/18 on downforce. Hot laps sets are lower, but when you reduce downforce you also have to make susp changes to compensate for the reductions. Not sure what Im actually looking for for an answer, maybe more or less Im just looking to get some feedback from others that have been where Im at now, and to see where to turn to next.