Got a track related question? I'll try to answer.

[DocWalt]

XP12 dust washes off fine for me. I let XP10 dust sit for months and it's not coming off (without way too much work anyway) in the places where it literally piled up.

[CSG Mike]

Originally Posted by CSG Mike

In a purely theoretical context, draw a force vector diagram, of the rear wheels pushing the car forward for acceleration, and the front wheels exerting a tangential force for cornering. Now, tilt the drawing to simulate "oversteer" by tilting it in the force of the tangential force from the front wheels. Notice how the lateral tangential force is additive with the components of the rear force vector. Now, tilt it the other way to simulate understeer, and note how the vectors are now subtractive.

Oversteer is always faster, in a theoretical context. In a real world context, you have to be able to manage it, and most drivers will be faster with an understeery car, because they fear oversteer, and avoid it, instead of seeking to exploit it.

Quoting myself for visibility.

[Icecreamtruk]

Originally Posted by CSG Mike

In a purely theoretical context, draw a force vector diagram, of the rear wheels pushing the car forward for acceleration, and the front wheels exerting a tangential force for cornering. Now, tilt the drawing to simulate "oversteer" by tilting it in the force of the tangential force from the front wheels.

Is this what you meant mike? (sorry, no photoshop on this PC so paint will have to do).

[n0thing]

nankang ns2r 120tw 215/45r17
hawk hp+ front/rear
spc rlca
kwv3 @ recommended settings, lowered 1.5"
have oem 14mm crash bolts available for upper slotted mount hole (not sure what max camber I can achieve?)

whats the recommended alignment for track? or mixed dd/track?


thanks

[strat61caster]

Originally Posted by Icecreamtruk

Is this what you meant mike? (sorry, no photoshop on this PC so paint will have to do).

That diagram implies that your front tires (doing all the turning) has imparted some acceleration in the forward direction, not true.

From a pure free body diagram physics perspective: It's the forward facing vector has a slight angle to it as if the rear tires are slipping and providing an additional lateral cornering force. This means that less steering angle is required to generate the proper line through the corner.

Less steering angle = less rolling resistance as the tires are pointed straighter = more speed.

I'm not terribly happy with this diagram, but for a half hour in powerpoint it should get the conversation started nicely. Lots of things I'm not happy with, mainly I sized my vectors poorly and inconsistently to get the point across.

Consider this a draft and if I get bored sometime later I might make it correctly so that oversteer+ is actually comparable to the neutral turn.

I also believe Mike was using a more 'feel based' learning tool to convey the concept, not a hard free body diagram, but might as well go overboard.

[Icecreamtruk]

You know how long it would've taken me to draw all of that on paint? lol

But you get the idea, its the same I was trying to show, just look at the vectors on the center of your diagrams, same as mine so yeah,. You moved the vectors (to the right on the rear wheels), I moved the body of the car, same end result.

Anyways, thanks for going overboard, might be clearer for most people than my fail attempt at paint (if only I had photoshop here!).

[CSG Mike]

Originally Posted by strat61caster

That diagram implies that your front tires (doing all the turning) has imparted some acceleration in the forward direction, not true.

From a pure free body diagram physics perspective: It's the forward facing vector has a slight angle to it as if the rear tires are slipping and providing an additional lateral cornering force. This means that less steering angle is required to generate the proper line through the corner.

Less steering angle = less rolling resistance as the tires are pointed straighter = more speed.

I'm not terribly happy with this diagram, but for a half hour in powerpoint it should get the conversation started nicely. Lots of things I'm not happy with, mainly I sized my vectors poorly and inconsistently to get the point across.

Consider this a draft and if I get bored sometime later I might make it correctly so that oversteer+ is actually comparable to the neutral turn.

I also believe Mike was using a more 'feel based' learning tool to convey the concept, not a hard free body diagram, but might as well go overboard.

I can save you some time. Take the neutral drawing, and rotate it 5 degrees CCW for understeer, and CW for oversteer. Take the x components of the front and rear force vectors, and understeer will be destructive (subtractive), while the oversteer will be constructive (additive).

If you really want to go overboard, you shorten the front vector for understeer, and shorten the rear vector for oversteer (kinetic vs static friction). The net X component will still have the same type of difference as above. For the sake of the exercise, we assume that the tire has an equal amount of longitudinal grip as lateral grip.

[Icecreamtruk]

Question purely on driving style here. Lets try to leave car setup out of this, imagine a fairly stock twin with an oversteer tendendy (at turn-in, mid-turn and exit, everywhere basically). When you enter a turn, during trail braking, if the tail starts to step out, do you wait until the front is pointing at the right direction to correct it, do you start correcting right away, or do you correct just enough to allow the current slip angle to stay but not to increase (basically keeping the car in a stable light oversteer position).

I find that most of the time I correct oversteer right as it starts (probably out of fear) and when I realise what I just did its too late, I scrubbed a bunch of speed and destroyed my line, and go out slower and missing the apex by a feet or so. I feel like I should be letting it slide a bit longer, but is it really the way to do it?

I've tried following the "fast guys" around, but most of them are driving AWD or FWD cars, the only really quick guy on a RWD car is a miata and his lines are very tiddy, 0 oversteer everywhere, just clean laps.

Edit: Mike, I havent forgotten about that quote for the JRZs you gave me (on reddit), its still at the top of my list, probably going to make the decision on winter, I'll keep you updated as needed.

[CSG Mike]

Originally Posted by Icecreamtruk

Question purely on driving style here. Lets try to leave car setup out of this, imagine a fairly stock twin with an oversteer tendendy (at turn-in, mid-turn and exit, everywhere basically). When you enter a turn, during trail braking, if the tail starts to step out, do you wait until the front is pointing at the right direction to correct it, do you start correcting right away, or do you correct just enough to allow the current slip angle to stay but not to increase (basically keeping the car in a stable light oversteer position).

I find that most of the time I correct oversteer right as it starts (probably out of fear) and when I realise what I just did its too late, I scrubbed a bunch of speed and destroyed my line, and go out slower and missing the apex by a feet or so. I feel like I should be letting it slide a bit longer, but is it really the way to do it?

I've tried following the "fast guys" around, but most of them are driving AWD or FWD cars, the only really quick guy on a RWD car is a miata and his lines are very tiddy, 0 oversteer everywhere, just clean laps.

Edit: Mike, I havent forgotten about that quote for the JRZs you gave me (on reddit), its still at the top of my list, probably going to make the decision on winter, I'll keep you updated as needed.

A stock twin has an understeer bias, if you progressively approach the limit. However, the transition speed is slow enough, that it's easy to overcome the rear grip before the front limit is reached, by forcing it. The fastest state of cornering with a stock twin is still to just plow through a corner, except for very tight (low 2nd gear at most).

Highlighted some things for you.

You're correct, the fastest state of cornering is more elusive than most people think. You're playing with "brake steering", aka trail braking, to induce more rotation for faster cornering. That's a great start. Now also work on "throttle steering". Many would say that the car doesn't have enough power to break the rear end loose. I would respond by saying, if you're at the limiting of cornering grip, you can always break the tires loose, regardless of power output.

A rear sway will help loosen the rear so you have more opportunity to play with rotation; it's a VERY common "stepping stone" mod I have my students do before they transition into a truly balanced suspension setup.

[Apex_BRZ]

A rear sway will help loosen the rear so you have more opportunity to play with rotation; it's a VERY common "stepping stone" mod I have my students do before they transition into a truly balanced suspension setup.

Interesting. So you're saying just adding a rear sway bar will help the car be a little faster since you add rotation easier? Is there a sway bar out there you'd recommend?

Which suspension parts would you change/use to create a truly balanced setup?

[Whooosah]

How do you help braking stability? When ha rd braking from straights the car seems to squirm around a little. Not sure if this is normal under threshold braking. Makes me a little nervous to get hard on the brakes with walls close by so my lines are a bit compromised giving the walls a bit of extra space... Still on stock alignment and suspension. W5 pads. Planning to get an alignment once I get new springs and just curious if there is anything in specific to ask for.

[MaximeT]

Harder front sway bare help braking a lot. But it move balance to understeer.

If you have no brake balance troubles, it looks like you need harder suspensions than stock.

But you'll get used to the amount of move under braking. The car can't go very far braking straight.

[CSG Mike]

Originally Posted by Whooosah

How do you help braking stability? When ha rd braking from straights the car seems to squirm around a little. Not sure if this is normal under threshold braking. Makes me a little nervous to get hard on the brakes with walls close by so my lines are a bit compromised giving the walls a bit of extra space... Still on stock alignment and suspension. W5 pads. Planning to get an alignment once I get new springs and just curious if there is anything in specific to ask for.

Stay out of ABS. You may be overheating the pads; the W5 on stock rotors is a fairly entry level race setup.

[CSG Mike]

Originally Posted by Apex_BRZ

Interesting. So you're saying just adding a rear sway bar will help the car be a little faster since you add rotation easier? Is there a sway bar out there you'd recommend?

Which suspension parts would you change/use to create a truly balanced setup?

Eibach rear. CSG sell them, and it's adjustable.

A truly balanced setup is individualized to every car/setup. You'll need to schedule a consultation to discuss that; it's not cheap to do, but the results are amazing.

See this thread for an example.

http://www.ft86club.com/forums/showthread.php?t=105670

If you're interested in experimentin with high end dampers...

http://www.ft86club.com/forums/showthread.php?t=107935