0.o slow 1.6

For the rears.

Stinkycheezmonky

To clarify, 1.) do you mean wider rather than narrower, or wider THAN THE FRONTS? and 2.) do you have any track experience? If anything, I'm considering going down in size in the rear, and know several others that have as well. Oversteer in a Honda is the fast way around, assuming its within reason (and sometimes when its not ).

JBrettHowell

Compliments of Perry Bennett Photography:
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With over 200 lb-ft and 200 hp on tap, even with a Quaife and some tweaking on the suspension to help plant the inside front tire, we need the 275's to get the power down coming out of the corners. When it rains we pull boost to try to keep from just spinning the wheels.

I'm sure the 275's have much to do with the less precise feel of the car. That was sort of the point of sharing the experience - different setups on the same chassis produce markedly different experiences for the driver. Still, if we can figure out how to get the car to turn in more like the ST car, that would be gravy.

powerneedy

weird to think you cant plant the power down with only 200ish? I had almost 100 more whp and ran v710's 225's on my built jrsc/lht setup and it had plenty on tractions out of the corners... maybe throttle control? maybe some more suspension tweeking?

JBrettHowell

You are correct Powerneedy - that the solution to dealing with the tire spin issue is/was modulating the throttle (which was no easy task for the ham-fisted yours truly), but we've got it to the point now where we can pretty much use everything Dave's car has to dig out of the corner (which is great fun). Could it be "driven" on 225s? Yes. Would the times be as quick? Almost certainly no.

meb58

Make the rear track wider...if you can within the rules...this will help turn-in...

JBrettHowell

We are just barely able to tuck the 225's as it is, but that is interesting information. I guess it makes sense now that I think about it.

Thanks.

meb58

...more rear roll resistance...I've experimented with track changes quite a bit...couple hundred thousand miles on a few makes. The magnitude of the change is of course affect by other tuning but it does work.

And, I've come under lots of fire for writing the following, but it is pure physics. all else equal, wider rear track = more rear roll resistance which = more turn-un oversteer BUT! we get more grip in steady state because the tires can perform more work...the later is more apparent when making the front track wider on a nose heavy front driver. you might have to tinker with spring rates a little to extract all that is possible but it does work.

JBrettHowell

I could see how a wider rear track would increase the outside rear wheel's leverage and help plant the inside front wheel better...

meb58

Yes, and without the drama that ulitmately follows with too much rear bar...but in principle roll resistance works the same, across the car.

almost forgot...if you have a mulit-link rear set up you might have to add in a little more neg camber. A wider track almost always softens the camber curve...just be aware of this...this may not affect your setup.

solo-x

You gotta see the torque curve from Dave's car. The peak numbers aren't spectacular, it's how early the power comes on that will blow your mind. At any rate, v710's put power down better, but Hoosiers are faster overall. If your car had a longer wheelbase and weighed more/was more front heavy, that would affect it too. And at peak lateral acceleration, putting 165whp down in 2nd can be a challenge even on a longer wheelbase car.

Funny that you guys mention vague turn in with the 275's on Dave's car. What backspace are you running on the front wheels? If you aren't using a front bar and some pretty hefty front spring rates, you might have some issues coming from that as well. My car turns in razor sharp. Fast enough that it can cause problems. Those problems are further compounded by the stock Torsen tightening the line if you roll on the throttle. More then one cone has been clobbered due to that.

How well are you managing heat on those 275's? I noticed that the A6's got really vague when they got too hot.

JBrettHowell

The numbers are something like 180 lb/ft of torque at like 2800 rpm and it just builds gradually from there. I liken full throttle to someone smacking the seat back with a 5 lb sledge. But learning to squeeze the throttle rather than dropping it has been an adjustment (this thing is nothing like the Pebble).

4.5"? Dave was pretty mindful about getting as much of the wheel under the fender as possible. Although his long term plans include inboard suspension bits and the 275's tucked under stock fenders (I'm pretty sure it can be done with Street Modified allowances...and if it CAN be done, then I'm confident Dave can do it).

Si front bar with 900 lb/in springs. ST rear bar with 675? lb/in rear springs. Yeah, I know it sounds backwards, but with the staggered tires it works.

Egg zachary what I experienced in the ST car...turned in so well that it took a couple of runs for me to adjust to it and not have to keep making adjustments to take wheel out of the car mid corner.

We water them between runs with two of us...on warm days. We did not do any watering at the Dixie tour, but it was friggin' cold.

I like the feedback though. Thanks, and keep it coming.

The Destroyer

Just so im understanding, you are saying you have lower rates (in relation to the rear) in the front with a front sway? Or vice versa?

Brett sorry I didnt pick up on your rhetorical question.

tazeat

Holy hell, that's got to be a blast. My NA B18C1 has the 200whp... but I only hit 133 lb/ft of torque.... At just over 8 grand and it's a bit heavier I'm sure .

meb58

Trying to help through a forum is difficult...how how high or low is the front end? I ask this question because it is fundamental and can affect front end traction...

JBrettHowell

Understood...I appreciate everyone's willingness to chime in. Thanks.

Here is a pretty good pic of the car under full throttle at speed (while still accelerating, it's already going at a pretty good clip, so the car is pretty settled). I can find a pic of the car sitting still if you need it.

Keep in mind that there is a great deal of material cut from the front fender, so don't be thrown by the apparent fender gap. It's just about the same height (maybe about .5" higher) than the ST civics we run with here in Atlanta.

If this question was directed at me, we have 900 lb/in springs in front with an Si swaybar, and 675 lb/in springs in the rear with a ST bar. Balance is awesome, just the turn in is a little bit vague (we've tuned out most of the wheelspin issues we struggled with last year).

meb58

Big rear rates are in vogue in some circles but since the mass of most front drivers is up front that's where the bigger rates go. I used a similar arrangement in my Mini but the rates were lower by about half

JBrettHowell,

Can you add a little more rake to that set up? I don't have lots of time but although a higher RC relative to the CofG will load tires faster, weight transfered during steady state is less. So, if you set you car up with a little more rear rake you might find turn-in to be a little crisper. I do know that some folks like a lower back end in a range of honda set ups...not arguing against or for it...just that a little more rake may help.

From my experience...ride height and wheel base considerations are fundamental...meaning, the most basic of tuning.

solo-x

Yeah, Dave's attention to detail is quite remarkable, so I'd be surprised if 4.5" is the actual backspace number. I'm at 5.75" of backspacing on mine. That said, scrub radius might be a big part of this.

Those spring rates and bars sound pretty close to me. I'd probably throw the hollow DA GSR front bar on instead of the Si bar, but that's really getting into splitting hairs territory.

Try a tick more front toe out?

If it's not scrub radius, you guys are overheating the tires. Put a pyrometer on em just after a run. If they're over 130*, there is a really good chance that you're overheating them on course.

The Destroyer

Wasnt directed at you, but seeing as solo-x said his were close, im assuming his setup is very similar.

Stinkycheezmonky

Meb, why do you keep placing such an emphasis on the setting up for crispness of turn-in?

L8apex

Hold on. I've always thought that increasing wheel track essentially "softens" the suspension. Please pardon my lack of familairty with the proper terms. Moving the wheels further out moves the contact patches away from the pivot point of the suspension, increasing the motion ratio (?).

So with a spring rate of, say 500in/lbs, that's essentially the pressure applied at the spring perch, even less at the contact patch, and even less than that if you move that contact patch further away from the centerline of the car/control arm pivot point. Therefore, softer.

Same principle applies to swaybars. Please correct my logic if I am mistaken. Or is there a practical factor that I'm missing?

I've always thought that, generally, you adjust one end of the car for a certain handling trait, then you make the OPPOSITE adjustment at the other end of the car to get the same basic effect, ie. increase negative camber at the front for more oversteer is the same as decreasing negative camber at the rear.

So increasing rear traction (with wider rear tires) has the general effect of decreasing front traction (relatively), which is not what you'd want in a FF platform.

JBrettHowell

I think he was just responding to my crying about the interest in ways to enhance turn in on Dave's car.

I took that to mean widening the rear track along with an increase in spring rate to counter the "softening" effect.

Stinkycheezmonky

Then in this particular case it makes sense. I've seen him bring it up on more than one occasion though.

L8apex

Ok, given that you've increased the spring rate to compensate for the contact patches being further out, still seems kind of a weird by-product of this change that it helps plant the front wheels better. Wouldn't widening the front track be a more direct modification for better planting the front wheels.

But I forgot what the original topic was about and just realized that this is a bit off tangent. Move along...

meb58

All else equal, make rear track wider will increase roll resistance and therefore oversteer...but if a wider track affects the motion ratio on your particular setup you have to get back to orginal wheel rate to experience the increase in roll resistance.


Re crispness upon turn-in...was part of the OP's question...I think???

Also...we look at making the rear track wider in this way, make the front track a little more narrow...