billyboy

Here's a local honda driven by a young, fearless tyro, pretty much typical of the usual attitude they develop and evident in over the 50 years of racing production fwds. When you start rabbiting on about droop and toe set-up on one...and then try to relate it to one of these cars, well, there's very little similarity beyond four wheels.


How many thousand miles do you think you're doing at a track day, lol? If there's street tyres involved, he'll probably have sold the car before the tyres are shot.

By some quirk, there's all the ones you have plus many more sticky tires here and even more again where the OP is living than the US, without exception, they all lose time after a few cycles, some will be reasonable, others will drop off a cliff and be more at home with the flintstones. They're all still usable though, the only thing you'd be doing continually running them, is testing mechanical longevity.

Depending on the machine, how low the car is and tyre diameter you can run into troubles with the attachments not clearing bodywork.

j9fd3s

iTrader: (3)

oh i don't know, the chassis setup on our integra was almost the same as the setup on the FC, except backwards.

Valkyrie

The car or tire isn't bottoming, the shock is. The rear shock only has 2.36 inches of stroke available from full droop to full bump. For some reason.

I've got -2 in the front and -1 in the rear, although I could have sworn I asked them to max it out in the rear... ***** don't listen. Would it be good to just use the same on both axles?

They left it with a 1.4 degree gap between left and right. Sigh... I would have preferred more since I want more feedback. Steering feels light having come from an MR-2. At one point I noticed the rack had actually moved and had come out of the bushing. I replaced one of the bushings, but not the other (supposedly the other one was out of production, although I don't believe that). I should check it again just to make sure it's in place.

Before I bought the car, I noticed the shocks seemed way too soft. Even at full hard, they don't have enough damping for their springs. They were full order shocks from some Asian brand. I'm probably going to buy some HKS coilovers designed for the track (16 kg spring rate). Sad, seeing as how few miles are on them.

I will do that eventually. I actually know a place where I could get a blade-type adjustable front, but I don't want to throw money at go-fast bits until I've sorted out technical issues.
for tire pressures, just set them all to something, hoosier has a chart of tire size to vehicle weight, just use that and then don't touch em. tires are springs.

Yeah, there's zero sense in having pyrometer readings if you don't write them down. I should probably get a clip board...

Valkyrie

I have seen this guy before... very entertaining.

That RX-8's sound is glorious.

I know someone who runs 36 kg (2000 lb!) springs on a 750-kg Civic (with a bit of aero). I suspect they'd be just as fast with half the spring rate if they used the rear bars and simply corrected the bump steer/roll center.

ZDan

What what WHAT?!
Whoever said anything about fwd cars?
I mentioned toe experiences with my 240Z and (AP1) S2000. Not totally dissimilar to the FD. Actually the FD acts more like the 240Z than the AP1 (which has the rear toe change with bump issue stupidly designed in).

Generally I get on the order of 100 track miles per day, ~200 track miles per two-day event with the time-trials club I run with.

For a lot of people who do track days, having tires that are within a tenth of optimal condition is not that important. If a tire "falls off the cliff" beyond its optimal life, that's one thing, but many track tires you can use, as I said, practically to the cords.

But ANYway, even if tire life is not a concern at all, I still say that it's a ****-poor use of tires to pit the one against the other down every straightaway, and in the corners more rear toe-in means the outside rear is having to operate at a larger slip angle for the same total lateral grip.
That's kind of a philosophical viewpoint, I wouldn't even bring it up if I hadn't found a lot of rear toe-in to suck in actual practice, again in the Z and the AP1. I have not experimented with it in the FD, don't see any need to.

IMO, a lot of rear toe-in is a band-aid that, in my experience, doesn't even provide the advertised benefit of "more stability". It just makes the car not want to turn in as eagerly, and can even give straight-line instability in rain and over bumps/undulations in the tarmac.


I wouldn't be going on about this if I hadn't had such profoundly negative experiences with running a lot of rear toe, and I have yet to experience any negative effects from running toe-in numbers nearer to zero.

j9fd3s

iTrader: (3)

i just take a picture of the pyrometer with my phone. you need to do something that works for you, with the key being that you need to do something.

the civic has a motion ratio that isn't 1:1. and the weight distribution is like 70/30. we're running 1100 in the miata, and we came up from like 950 or something and both drivers really liked it, which actually should be our test

j9fd3s

iTrader: (3)

i sometimes wonder if some of our suspension truisms, like having zero bump-steer, are just not applicable. the FD and S2000 both have bump-steer designed into them on purpose. and both cars are a far cry from a primitive car that didn't have the rest of the basic geometry right.

ZDan

240z basic geometry isn't terrible. Rear roll center is high, and there's a lot of designed-in rear toe-in (not adjustable due to Chapman strut design), not enough front camber (also fixed for stock car due to McP struts), but again, with minor mods it's a pretty brilliant car to drive at the track.
I slotted the shock towers all around for more negative camber, lengthened the front control arms for more front camber, and ran offset Al/delrin inner control arm bushings for still more negative camber up front and for toe adjustability in back (knocked it down from ~0.6° total to ~0.2° total).

No word of a lie, the FD handles a lot more like my 240Z than the AP1 S2000. The FD and Z are very linear and easy/fun to hang the back end out. The AP1 has so much toe change with bump that you end up losing a lot of time when you get the back end out. With the FD and Z I can stay in it and they both just behave a lot more predictably and linearly while hanging it out.

There's no way the FD has anything like the rear toe-change/bumpsteer with stroke that the AP1 S2000 has. Anybody have toe curves for the FD?

Valkyrie

Taking a picture isn't going to do much good unless you have a pyrometer that automatically records the three spots on all four tires. I only have a simple one.


Knowing him, using springs that stiff is just a bandaid for something else, whether in terms of geometry or driving technique (although he is fast).
Even on a Civic, 36K is the equivalent of using something like 24K springs on a car with McPherson struts. It's batshit crazy.

Valkyrie

Wouldn't changing the fore/aft angle of the strut change roll steer? Theoretically, at least...

I noticed that my FD was MUCH more forgiving with oversteer than my MR2. I guess that stands to reason... Haha.

j9fd3s

iTrader: (3)

so find the hottest tire and then just work on that one, and then when that one looks good, work on the second hottest one.

billyboy

Apologies, always thought they were wrong wheel drive and hence you're out of your mind comparing! A friend made and sold forced induction kits for them when they first came out and was none too impressed with the development mule's handling to put it mildly, so always assumed fwd. I can't remember the last time I saw one on the street here even, pitiful sales locally.

On the understeer issue, seem to recall 3 (maybe 4?) options on rear bars stock over the years and a short-lived different front bar before they went back to the original one. Might be a task finding any early FD parts on yahoo now though, if trying for the 17mm bar!

Valkyrie

I gave the rears a half-turn and for whatever reason, I went half a second faster. My rear tires also got closer to their operating temperature (120 > 140), which probably gave me a bit more grip.

I also tried giving the fronts half a turn of toe out, but that didn't seem to make much of a difference since the threads on the stock tie rods are so much finer. In the case of the rears, they've very coarse threads, so a full turn gave it WAY too much toe in, visually speaking. I turned them back half a turn and they looked to be about 4 mm or so.

My fronts are still a little cold. I wonder if a bit more toe out will get them up to temperature and help with turn-in?

I need about another degree of rear camber since the temperatures are fairly even across the face (although I suspect that three spots across the tread gives you misleading information...). The fronts are just about right, but I could probably use a little more camber.

j9fd3s

iTrader: (3)

if your temps are low across the board run more tire pressure. unless the tires are dead, heat cycled out, if this is the case they will not heat up correctly no matter what you do

ZDan

140F? That seems very low...

What's the relationship between your cold (like, stone cold at beginning of day, before getting on track) and hot pressures? Hot pressures should be something like 8 to 10psi higher

Also, are you just getting faster? I don't think the toe change gave you 20F higher rear tire temperatures which made you half a second faster...

I wouldn't be making adjustments like this at the track without having done the geometry calculations (or doing it experimentally and measuring) to *know* how much toe change you get for a given number of turns..

I wouldn't use tire scrub from increased toe (either way) to try to get more temp into the tires at either end of the car...

If the tires are really that cool after lapping, either they are just too big or you're not driving fast enough!

Yeah, optimum setup for lap times the inside of the tread will be ~5-10F warmer than the outside. Why would you suspect that taking temps at three points across the tread should give misleading info? Of course you can take 4, 5 or more points but three should suffice.

ZDan

I don't think that increasing pressures should increase tire temperatures.
More pressure, less deformation, less hysteresis, reduced heat into the tires.

Nabu

Very interesting topic and nice write-ups from you guys.

Subscribed.

Valkyrie

To some extent, but not that much... Keep in mind the tires are cooling off every second after you stop flooring it! These are street tires. Also, the car is very light and has no aero. I don't think 140 is that low by the time I've actually measured them.

They're the stock 17-inch sizes. I could go faster but I need more damping. The car is pretty severely underdamped IMO. It also needs a bit more spring and stroke. A clutch-patch LSD would also be helpful... Oh, and a rear wing.

Because taking temps in roughly the same area can give wildly different temperatures sometimes.

Lots of times I'll take the temps again to make sure I wrote them in the right direction and they end up being much more even...

Natey

iTrader: (19)

I didn't read this whole thread so apologies if it's already been said or if I'm disagreeing with anyone, but
I ran Pettit's "Long Track" alignment for a few years and it was all good. I felt like I could turn some pretty quick laps... UNTIL I went back to bone stock OEM specs (but a little lower & stiffer from the coilovers) and now I feel so much more confident. I'm having a hard time believing that I stuck with the old specs for so long. The car tracks perfectly straight now and seems so much more planted on long sweepers. It seems 100% neutral once it begins to let loose, which is definitely something I love. The Pettit specs could turn-in on a dime and give you 8 cents change, but on longer corners, it'd get a little sketchy - for me at least - about 60mph or so.

Try OEM alignment on your next trackday. I'm no professional driver, so maybe the Pettit specs are over my head, but I usually run in the expert class so I'm not granny-footin' either. I'm thinking maybe there's a good reason Mazda set up the car how they did.

Anyway, my tail happy days are over. My car grips like a 14year old on pornhub.

Valkyrie

If you changed your suspension at the same time you changed your alignment, you really can't compare the two alignments. The stock alignment doesn't have enough negative camber.

On an unrelated note, I'm wondering if the reason my car is kind of squirrely under heavy braking is because the idiots at the shop that did my corner weight adjustment used massive amounts of preload instead of just adjusting the ride height like they're supposed to (my coilovers have seperate preload and ride height adjustment). So I ended up with much more preload on one side than the other. I already took the preload out of one rear corner (while maintaining ride height), but the other side has slightly different preload.

j9fd3s

iTrader: (3)

measure it sometime. if your temps are a little low, and the pressure is at a book value, increasing pressure increases temp.

certainly it works like you say on the street. there is either a temperature to pressure curve, where temp is high at both ends and low in the middle, or the street and the track are different enough that the street wisdom does not apply.

all bets are off if the tire is heat cycled out though, it will give you crazy readings and let you chase your tail

Valkyrie

In my experience it's pretty hard to actually use too little pressure on the track.

I started with 26 psi cold, which went up to 32 hot, and I kept letting air out (because the pyrometer said the centers were a little higher than the outside), and then I'd do another stint, and the pressures would be almost back to where I left them. Next time I might start them at 23 or 24 psi cold.

Of course, my car does weight almost 200 kg less than stock.




OTOH, my conclusion regarding a baseline alignment is basically "as much negative camber as the car will give you, 5-6 degrees of caster, zero or a little bit of toe out in the front, and as little toe in in the rear as you can get away with."

Natey

iTrader: (19)

I didn't change anything. The coilovers were there with the Pettit alignment too. I track my car pretty much every weekend.
I might not advertise that to everyone on the forum like some boy racers around here do, but it's true. Unless YOU have been to the track on the stock alignment then I say you're running too much camber in the rear and blowing through tires faster than you need.

Valkyrie

If you only drive on the track, more camber will actually help your tires last longer...

BLUE TII

iTrader: (9)

Right up to the point at which you have too much negative camber...