Sometimes, thats all that matters

 

I am unsure of whether to post this here or in the STU thread...

DaveMac, I have been meaning to PM you with a question, but perhaps it would be appropriate for more people to be able to comment/read on the matter:

I remember a post where you stated that you didn't like low offset front wheels because it messed up the front roll center IIRC. Can you please explain just how this affects handling and feel in practical terms?
I am curious because I am running the common reverse-stagger +18 effective front offset using 20mm spacers and +38 rear in order to fit 17x9.5 RPF1s (basically imitating Jung's STU setup).
I know reverse stagger is common practice with Japanese Road Racing Evos for what has been described as "better turn in", but after driving Donour's RS (non-staggered offsets and 8.5" wheel STU car) his steering felt MUCH lighter and more responsive than mine on my GSR.
Besides suspension settings, a less stretched tire,and the GSR/RS differences, do you think the offset could be a factor?

I addressed Dave Mac because it's his comment that got me thinking about this, but anyone else please speak up on your experience/feelings about this.

 

If you run less offset in the front, that has one added benefit, it widens your front track that helps improve front end grip. If anything on a Macphereson strut setup it'll help bring the roll center slightly closer to the CG. On the flip side, it increases your scrub radius which in turn will take more effort to turn the steering wheel. Add to the fact that your unsprung weight with your larger (heavier) rims compared to Donour's, which also adds to more effort in steering the car. But I'll let the experts chime in ...

 

Ah, those are good points and make sense. Thanks Suraj.
You already mentioned a key distinction that I omitted: the difference between steering feel and grip. While Donour's steering felt lighter and more responsive, it also felt looser.

 

Just one quick thing - a narrower wheel/tire will FEEL more responsive and lighter on initial turn-in, but the wider wheel/tire will have more ultimate grip.

Think about it this way - picture the difference between responsiveness of a steamroller or an ice skate . . .

If you could have the centerline of the wheel right at the pivot point of the spindle, that would yeild ultimate feel and responsivenes. . . but unfortunately with wide wheels we run into inside wheel well clearance issues. . .

 

Dennis Grant's theory describes "ideal" a different way. In a full frame car in a class that doesn't allow extensive stripping and ballasting, you are almost always going to have a car that is significantly heavier on one side than the other with driver. Thus, you will always have a car that will turn better in one direction than another. You can't really help this. What you can do it make it's cornering balance (oversteer/understeer) the same for both left and right hand turns. Let's assume yoru car is 60% nose heavy - well, then you want the front left to have 60% of the total left side weight, and the rear left to have 40%. You want the front right to have 60% of the total right side weight and the rear right to have 40% or the total right side weight. That way whether you are turning left or right, the suspension will compress in the front and rear at the same rate. . .

Does this make sense? Can anyone explain why this may not work out? Having not read the in depth suspension design books, this makes common sense to me . . .

To be completely honest, I touched the click adjustments on my dampeners for the first time EVER just within the past month . . . I just set them close to where they were on a similar car and left them. The car has handled decently and I've been working on lots of other areas to get faster - driver, aero, weight, powerband, stickers . . . well most of that stuff is done so it's time to fine-tune what is there. . .

I don't "know" most of it, as in I haven't proven it by testing myself. All I have to go by is what I've read and what others have told me. That's what this thread is about - to try to get as much input from as many sources as possible and then we can each make up our minds what we think is "right".

 

Thanks. Yeah, that's what I was thinking, but I was just curious about the effects of the low offset front wheels/reverse stagger.

 

Do most of you agree that with a coilover you should go with stiffer spring rates
in the rear like the evo comes from the factory? I have kw v3's and am thinking
of changing the 9k front and 8k rear around. Leaving the rear sway bar stock and
doing the front swaybar mod. Any suggestions?

 

Yes, stiffer out back with a rear sway bar. Front sway is sufficient.

 

I am not sure about the bars, especially because they should depend on the cars handling after the spring rates are established, but yes, I definitely agree that higher rates in the back than the front are generally desireable for optimal handling.
Swap them front to rear and see how you like it then.

 

ok so swap the spring first, then see if the sway bars are needed. I have some
bushings and whiteline front roll control going in, so I guess I will do it then.

 

It makes sense to do it all at once from a labor/time perspective, but personally I try to only make one change at a time so I can see how each change in parts or adjustment affects handling.
If you do multiple things at once, you will definitely notice that it handles "different." But what is "different" isn't quite "different" how you want it? How will you know how to make it "different" better? Especially with something that will probably affect handling as much as swapping springs f/r and RCA kit, I personally would definitely only do one at a time to see how each change affects handling.
Just my $.02

 

Uuri-

Regarding the front wheel offsets and front to rear stagger. I run a 17x9 Volk TE28 with a 35mm offset front and rear. Last year I did not run spacers at all, just a lot of caster (4.4 degrees). This year I added 15mm spacers to the front effectively changing the front track by 30mm. I found that the car still has great turn in and the steady state grip was increased. Knowing that the wider front track can effect the roll center I changed the way I added negative camber. I did most of the adjustment on the top of the camber plates and not with the camber bolts on the bottom of the strut. I'm running -2.7 degrees BTW and I have very even wear on my tires. I think that by adjusting the camber this way you can help mitigate some of the negative effects of the front track width change. This is what has worked for me, it's the exact setup I ran at the DC Pro Solo.

 

Thank you very much Dave. Excellent info! I'll have to explore that on my own setup.