on a flared car, do spaced wheels adversly effect handling
why do guys run no spacers in ax but run spacers on the street
i am planning to run 16x7s up front with 225s with flares, and looking ahead this will be my winter project
i am lookin for the low down on running spacers and handling issues for street use

I had a conversation with my race shop in which I was told that they fine tune cars by adding spacers to one end or the other.

I believe that as the track widened on that axle it added traction to that axle.

so front spacers should add front grip.

I am only passing along what I've been told (and I'm not 100% I'm remebering correctly about adding grip with track)

I haven't used it as a tuning technique myself as I've been learing roll bars, spring rates, diffs, and tire pressures... enough for my amateur level without changing track.

brant

more steering effort. and a larger scrub radius.

Yeap!

and you might have to add more toe in to counter the leverage effect of the spacers.
funny thing is that your steering effort a stand still or low speed might be easier, 'cause the tire will roll along an arc instead of twisting on the tread.

and the steering feed-back might be more sensitive.

Just guessing, but, without spacers use on the street would probably cause a lot of inner wheel rub due to full lock steering inputs in parking lots, etc. ?
Tom

I asked the same question at the WCR08
and got the same answer from the same guys.

The Scrub Radius becomes affected, if your on the street and want to fill out the flairs, go ahead and add the spacers. On the track it will have an adverse effect from when the alignment and geometry was set up.

Troy is " the man" he didn't Kill my clutch but came close, He and a few of the guys all said the same thing, try it and see what, and how it performs.

Until I can put the 8's in front and 9's in the rear, spacers will have to be.

Tony

that clutch had it's work cut out for it, puutin along 'bout 60mph in 4th gear and nail'n the throttle to 'bout what 120 ish rpm were 5,800 last i looked, and all that happened in a couple of heart beats.

oh and the top was off!



i'm gonna have to build one!

Adding front spacers will help widen the track. This will in turn reduce the amount of weight transferred in a turn. It will however on a strut car increase the scrub radius which can increase steering effort. You can increase the caster to counteract the effects a little, but going to far will make the steering floppy.

I'm running 9's front and rear. I notice more bump steer (but not much more) and it takes some grunt to parallel park, even with the big stock wheel. With a tiny wheel it might become nearly impossible to turn the wheels while stopped. If I had a choice I'd have narrower wheels in the front, but I got a deal on the wheels and that's how they came. (thanks markb!)


Edit: Well, the real question was about spacers, and I forgot to mention that yes, I needed 1" spacers to get the wheel to not hit the strut. I can turn full lock to lock, but they do still rub on the inside at full lock. It's amazing how much room there is for wheel in there with GT flares.

At an AX you do not want them as it will have an effect on the steering input. Your times will be slower.... I know this from experience. PUshing the wheels out in the rear widens the track for greater stability but in the front it is mostly for looks... On the track I take them off as your pivot point on the wheels is now different and throws things off.

wow, lot's of you "old timers" posting. Just like the old days...

yeah I know, I haven't been around for awhile

I've run up to 10 inch wide front wheels up front. The result was very high steering effort & an unfixable push in your average AX turn. A rough calculation was a scrub radius of 3.5 inches. Large/moderate steering inputs cause the tires to "shuffle" sideways rather than roll in a smooth arc. Live & learn.

To keep it simple, I found that a standard offset (with about 5 inch backspace) 8 inch wide Fuch is as wide as I can go. A 7 inch wide Fuch has the same backspace as the 8. A one inch spacer on a 7 would give the same scrub radius as an 8 inch wheel.
This set up is tunable from a handling set up aspect but the steering effort is higher.

Edit.
Make that a .5 inch spacer.

on the street, i run 7x15 cookie cutters with 225 tires and 1 1/4" spacers.

on the track, i run 7x15 cookie cutters with 9" GoodYear racing slicks and 1" spacers.


funny thing, steering is actually *easier* with the goodyear slicks! i had the car perfectly balanced with the old 1.7L motor.
now that i added the 3.6L, i'm having a lot of understeer in slow corners. i'm currently working on dialing that out.
Andy

andy what sway bar do you run up front?
so i guesse i will be looking at a understeer with 11/4 spacers up front
how does this effect a high speed corner, is there still a push?

not really. wider track means better grip, so that should give you more grip in the front, not understeer ...

i've got understeer now because the added weight of the /6 motor gives it more grip in the rear and in tight corners, when you hit the gas coming out of them, you're moving even more weight to the rear, so the front gets light = understeer.

i run the 22mm tarett bar up front and the stock bar in the rear, 911 carrera torsion bars up front, 250lbs springs in the rear. koni adjustable shocks all around ...
Andy

have you tried running with out the rear bar? or do you need it at higher speed?

tough to balance a car when you get so much weight transfer to the rear on accelaration

Removing the rear bar would make it worse. You want to soften the front and stiffen the rear to correct understeer.

Ok, this is a good topic. I had been planning on buying a set of the Rota Fox wheels. These seems to be sold as 17x7.5 +35ET for the front and 17x9 +16ET for the rear. I like the idea of running the same wheel and tire size all around to allow for more rotation options. I "think" you can buy the rota as a set of four 17x9 instead of the mixed sizes. So this bring up the topic of "what is the impact of running 17x9 both front and rear". I don't know what to do. Here is what is important to me in priority order...

1. Handling at track
2. Handling at autocross
3. Tire wear/rotation options
4. Ease of low speed turning

The car is going to have a full cage, 3.2 six for power, 911 front end and stock 911 torsion bars. Tarrett front swap bar, most likely no rear bar, but will have mounts for the rear. Koni all around and whatever rear spring rate that make sense. Basically similar to Andy, but with a slightly smaller motor.

What should I do?

Shunning a debate, my experience has shown quite a different result in general terms. Increasing the scrub radius (track) also increases the gain from caster which increases (cross) weight transfer (the inside tire will droop more). Adding yet more caster will amplify the effect. That's how it has worked for me.

Andys

my setup is pretty close now, with the front bar on full soft, i still get some understeer, but with the front bar disconnected, i get oversteer ...

so, i'm getting close ...
Andy

I just did spacers on my daily driver, you can tell a difference. The front tires argue less when driven hard and the car turns in better. Plus there is less body roll. You have to weigh the consequences when doing things like this. On a strut car it will increase scrub radius.

an additional thought.

a wider track should increase the lever arm on the spring
(which ever spring you choose: torsion/coil)

and effectively "soften" the spring rate

brant

But the wider track will allow less weight transfer, so the effect will be minimal. Think of it this way. With your feet together you can easily be knocked over. Spread your legs out and you become more stable.

From my experience, the benefits outweight the potential drawbacks ...

I've been running spacers on my GT flared car for 7 years now, both on the street and on the track.
Andy

This year I moved my tires from one set of wheels to another, the only effect being to increase offset at front (28mm wider track) and lower rotational weight all around.

I don't claim to be a professional, but I couldn't tell any difference in the balance of the car at autocross.

This comes from Mr FTD against all the big power 911's

Rich

That's one theory.....
Mine tightens the line as I roll on the power. We have some weight transfer, but no understeer.
We can compare notes on the concrete at Marina next weekend.