front wheels / steering feel - 986 Forum - The Community for Porsche Boxster & Cayman Owners

jaykay · 06-27-2012, 06:10 AM

What set/up changes could I make to get more front end and steering feel at speed?

Right now I find myself loosing confidence in higher speed turns in as I can't feel what the front tires are doing...as in where am I traction wise

The front end also feels very light under acceleration with steering feel dropping away ...

thstone · 06-29-2012, 03:46 PM

My guess is that you're feeling the understeer in the car - that is, in the middle of the turn, you turn the wheel but nothing much happens, the car neither turns more or less. Essentially, its plowing at that point and is unresponsive to more tire angle.

What tires and alignment settings do you have?

First, I'd suggest a sticky street tire like the Kumho Ecsta XS or Hankook RS-3 or similar that has a UTQG of 180-200. That will give you more front bite.

Second, get a performance or track alignment and have the camber is set to max negative. This will keep more tire on the ground through the corners when you're pushing it and thus, you'll feel more grip.

2003S · 06-29-2012, 04:31 PM

What's the tire pressure up front? I'd look at that first. If its high, lowering it could adjust the under steer some degree. You could run a few PSI lower in the front than in the rear. If you're already doing this, then disregard.

stephen wilson · 06-30-2012, 06:27 AM

It's hard to "diagnose" over the Internet, but I'll take a stab.

When does the front feel light under acceleration? At lower speeds, or high speed?

The loss of front end feel sounds normal to me. There will be some aerodynamic lift, and every steering input is magnified because of the greater distance travel per second. You will still feel the loss of traction in the normal manner, the steering will get light, and the car will be unable to turn at the desired radius, with additional steering input having no effect. (assuming an understeering car, a car with high-speed oversteer is much more exciting! ) I think the main problem is that you can't get away with grossly overstepping the limits like you can in lower speed corners and still "save it".

san rensho · 06-30-2012, 10:41 AM

Quote:

Originally Posted by 2003S

What's the tire pressure up front? I'd look at that first. If its high, lowering it could adjust the under steer some degree. You could run a few PSI lower in the front than in the rear. If you're already doing this, then disregard.

Not really. To get rid of understeer, higher pressure in the front, lower pressure in the rears. I run 36 front, 32 rear on my car and it feels much better.

blue2000s · 06-30-2012, 10:51 AM

Quote:

Originally Posted by jaykay

What set/up changes could I make to get more front end and steering feel at speed?

Right now I find myself loosing confidence in higher speed turns in as I can't feel what the front tires are doing...as in where am I traction wise

The front end also feels very light under acceleration with steering feel dropping away ...

What speed? At well over legal speeds this car should feel completely stable and controllable. When is the last time you had an alignment and looked at your tires?

2003S · 06-30-2012, 12:14 PM

Quote:

Originally Posted by san rensho

Not really. To get rid of understeer, higher pressure in the front, lower pressure in the rears. I run 36 front, 32 rear on my car and it feels much better.

Do I have it backwards? I thought lower pressure up front would increase traction... (within reason of course)

The owner's manual recommends 29 front / 36 rear, I thought this was to dial out understeer, and make the front wheels grab a little more...

stephen wilson · 06-30-2012, 03:46 PM

How tire pressures affect handling balance can be very car-specific. If the tires are "rolling over", more pressure may reduce understeer. If the resulting increased tire spring rate is dominant, it will increase understeer. In either case, the change tends to be minor.

FWIW, on the street with 18" wheels on my 987, I've found lower front tire pressures to reduce understeer. YMMV!

san rensho · 06-30-2012, 04:34 PM

Our cars are engineered for understeer. Understeer is the safest for those who aren't used to high performance driving. To make our cars turn, you have to dial out the understeer. fFrst step is tire pressure, higher pressure in the front and lower in the rear will definitely make a big difference. Next is to get as much negative camber in the front, although the stock limit is about -1, and aim for 0 toe. Then, in the rear, try to REDUCE the very heavy (stock around 2 deg) negative camber. You won't be able to get out much because as you reduce the camber, it affects rear toe and you won't be able to get toe to an acceptable number.

You probably have to go to an alignment shop the sets up race cars because most commercial alignment shops won't set alignment to specs outside of the "target" numbers.

thstone · 06-30-2012, 04:46 PM

The stock tire pressures help to create the understeer that Porsche desired (as san rensho explained). First, try making the pressures equal all around. If still too much understeer, then go in the opposite direction (high in the front, lower in the rear) and see if that helps to get rid of it.

Stephen Wilson was also correct in that you need to keep the pressures high enough to avoid rolling the tire over too far.

stephen wilson · 07-01-2012, 04:48 AM

I guess I'll have to try a larger change in raising the front tire pressures, and re-evaluate my results. I only tried 2 PSI changes, not feeling comfortable with less than 27 in the front.

I went up one size on the front, to 245/40 and 265/40, and it works wonders, while retaining a wear-friendly alignment. This is for street use, I don't track the car at this time.

LAP1DOUG · 07-01-2012, 05:21 AM

Quote:

Originally Posted by stephen wilson

I guess I'll have to try a larger change in raising the front tire pressures, and re-evaluate my results. I only tried 2 PSI changes, not feeling comfortable with less than 27 in the front.

I went up one size on the front, to 245/40 and 265/40, and it works wonders, while retaining a wear-friendly alignment. This is for street use, I don't track the car at this time.

It sounds like you are definitely on the right path with decreasing the front to rear stagger.

Every tire has an ideal camber and pressure for optimum grip, and anything off of this can be used to adjust steer characteristics front to rear, but you should keep in mind that you are compromising ultimate grip for balance when you go that way. As Carroll Smith taught us, it's better to work on making the loose end grip, then trying to "unstick" the end that is working.

In my experience, for most street tires, the total range of pressure adjustment should be around 32 psig - 37 psig. Anything more or less than this is a big compromise in performance.

The alignment advice given above is very good for maximizing the stock suspension. After that, you need GT3 type front arms and sway bars to improve grip and balance. Welcome to the slippery slope...

stephen wilson · 07-01-2012, 06:04 AM

Quote:

Originally Posted by LAP1DOUG

As Carroll Smith taught us, it's better to work on making the loose end grip, then trying to "unstick" the end that is working.

Agreed, that's why I adjusted the front pressures only, in an attemp to improve the end that's not working. Results can be more difficult to judge on the street, since there is only certain places where the balance can be "tested", and conditions vary from day to day. I may try a back-to-back test; run my favorite corner with high pressure, pull to the side to bleed some off, and try it again.

jaykay · 07-04-2012, 01:23 PM

Thanks all for the advice....I am missing out on track days this summer hopeful I will get back.....yes it's quite impossible to test without track time. I do feel the whole front end get way too light under acceleration out of an uphill turn. The steering gets twichty can the car can be upset with minor surface bumps. The front end feels like its rolling/floating too much such that can't feel it

I had though I was going too high at 33F cold but will try higher
I do feel the tread blocks starting to "mush" probably from heat rather than the tire folding under....more on the rear...not smooth slides but like the rubber giving up and recovering...very disconcerting

I am on pilot sports and stock alignment as I am still learning; the set up works in the rain but not high speed in the dry

Guess it is really about driver physche to a large degree

stephen wilson · 07-06-2012, 08:18 AM

Well, so much for my first tire pressure "test". I tried running 35/37, and the PSM kept killing the engine on every left-hand turn, as if I was losing traction. I guess the increased rolling radius with my larger diameter front tire is starting to confuse the traction control. I'll have to see if something like 32 all around will work, and not confuse my computers!

Adj. sway bars would be ideal, I just don't want to spend that money right now. Too many other projects....