Changing the Track

[tonycharger72]

Ive seen folks that have 10" wide wheels on their Zeds who have to been running a large negative offset on the wheels for them to fit, ie........clear the spring perch,

 

For example,

You have a 10" wheel (=11" approx) with coilovers you can fit about 125mm (5") of the wheel underneath the car, the rest of it is poking out past the fender,

So you end up running a large negative offset - like (-15), for the wheel to clear the spring perch,

So the wheel offset would change from 15+(stock Zed) to

-15 approx,

 

This is a fairly large change in track,

 

Im curious as to what kinds of effects this has on steering, suspension etc.....etc when you change the track this much,

Does it have a different effect front and rear when you change the track???

[johnc]

I ran 16" x 10" wheels and had them built with a 5.5" backspace. I used different thickness spacers (1/8" rear and 1/8" through 1/2" front) to tune turn in and handling for specific tracks. A wider front track (compared to the rear) will help the car turn in and reduce understeer.

[Clifton]

I run a 15x10 on the fronts of my 71 with 5" backspace. I use a 1/4" spacer. A 15mm offset is not very much. On the 73 I have a 25mm offset wheel, 17x8. Gotta do what you gotta do to get it to fit I guess.

[tonycharger72]

There is this Zed bloke in Aus ive spoken to a few times and hes just nuts about not changing the track on cars, says i will increase my srub radius which will cause the car, when it hits bumps, to track in the direction of the bumps,

 

He gave 2 examples,

Driving down a potholed road, right front tyre hits the pothole and the car veers rightward,

&

Driving down a straight at high speeds and the car can become unstable, wheels arent doing what the steering wheel is telling them to do,

 

He just put the fear of god into me about making any changes in track from factory,

 

JohnC, you only use the spacers to effect the cars steering characterisitics and not because of clearance issues?

Just id be pretty keen to avoid spacers for clearance issues, because i want to get my car road registered and the local RTA folk frown upon them,

 

Also curious,

How much fun would it be driving around town with 10" wide wheels? would i need arms like the hulk???

[260DET]

Of course if you are going to change the track and still retain stock components there will be changes to steering feel, reaction, etc. Depends entirely on what you want from the car, what it is going to be used for.

 

Personally I like a bit more scrub radius, gives better feel which can be good when ultimate handling is the goal. Plus a wider track gives better roll stability. But you don't get something for nothing in that regard.

 

As for changing track or whatever, manufacturers do it, just look at the factory ZG changes done to improve ultimate handling. The important thing is, know what you are doing and what changes you may expect.

 

Having said all that, by increasing the track I have never experienced any significant problems on the road. Steering effort at low speeds increases though, that is for sure. Consider also wheel alignment, its all tied in together.

[johnc]

JohnC, you only use the spacers to effect the cars steering characterisitics and not because of clearance issues?

 

Yes, for steering and handling only.

[Clifton]

Also curious' date='

How much fun would it be driving around town with 10" wide wheels? would i need arms like the hulk???[/quote']

 

As long as you are moving it's not bad. The faster the easier. Trying to turn when stopped is hard, even with 8" wide wheels.

[boodlefoof]

I would personally sacrifice track width for better scrub radius myself.

[tonycharger72]

So using smaller width tyres so you can keep the track the same as factory, like use 8" rimms instead of going to 10-11" rims so as to not increase srub radius?

 

Ive been looking at the 240zg a bit (nice looking car) and even if only 8" rimms were used, there is no way in hell that the ZG used factory offset rimms (ie....the same as the stock 240-260-280z's at 15+) they look like they have small negative offsets, which would cause quite a large change in track, and from what i know the 240zg is a factory car right?

So if the good folk at Nissan do it to there zeds, assuming nothing eles has changed suspension and steering wise - does changing the track from say a 15+ offset to a -5 to 10 offset really alter the cars handling ability, or does it just change it, change it like -

Just for an example (not what would actually happen)

"now it handles better around corners, but doesnt have the same straight line stability as it did before"

 

Or when doing the ZG with its large wheels and different track did Nissan also alter other suspension and steering characteristics of the car?

[johnc]

OK, let's get back to basics...

 

In steady-state cornering track width and center of gravity height determines total lateral load transfer. Increasing track width reduces the load transfer which improves lateral acceleration capability. So:

 

1. Corner turn in is improved because load transfer is reduced and loads are more evenly distributed. The tires can produce more force to quicken turn in.

 

2. Since load transfer is decreased this allows more of the total roll resistance to be taken on the non-driving end of the car which reduces inside wheel lift. This gives more equal loads on the driving wheels for better acceleration off the corner (this is why most smart ITS 240Z racers run a wider front track then rear). This is also why some folks have trouble making a Quaife diff work in a 240Z. Too much rear roll stiffness.

 

3. Increasing track improves braking in turns (trail braking) by increasing the total lateral acceleration capability.

 

4. Increasing track width improved rough road cornering because lateral laod transfer gives a little more bump travel in the suspension before hitting the bump stops.

 

Scrub radius problems can be reduced through other means. Increasing track, especially the front, on a 240Z is well worth any sacrifice in scrub radius.

[JMortensen]

Everyone I autoxed with ran wider front track, except the 911s. When I first heard about it I thought it was a FWD thing, but nope. From Mustangs to Ford Fiestas to 510s to Z's everyone ran wider front track.

 

Nice thing for me was with adjustable front control arms I was able to screw them out to get the wider track instead of using wheel spacers and this also gave more available negative camber. The combination of track and camber definitely made my car turn in better.

[tonycharger72]

JohnC thanks for that explanation mate,

Just to clarify, are you saying that increasing the track both front and rear, but increasing the fronts by a larger proportion is what will give you the benefits listed from 1 to 4?

 

It seems to me that it would be better to actually increase the factory track as basically i will end up with a better handling car,

So why on earth is this bloke, who seems to know alot about Zeds, so deadset against changing the track in any way shape or form???

 

I still havent been able to 100% confirm exactly what the original offsets of the Zed wheels where, im pretty certain they started at 15+ for all the wheels on the 1970-78 zed's,

 

JohnC you used 10" rims with a 5.5" backspace, so a 0 offset, so that is not a huge change in track from factory really, only 15mm (of course you used spacers which changed it further, not massively though) - even by law i can change my track some 27mm, you would imagine that the good folk at the RTA would set this 27mm limited because on a street driving car the cars steering characterics wouldnt be effected that dramatically by a 27mm increase/decrease in track???

 

This is the only real first hand experience ive had,

3 different sets of tyres & wheels on my Zed with stock steering and suspension components,

1 - 14 by 5.5 rims with 195/70-14 tyres (15+ offset rim)

2 - 14 by 7 rims with 195/65-14 tyres (15+)

3 - 17 by 7 rims with 205/40-17 tyres (20+)

 

Options 1 & 2 pretty feel the same, but option3 was much different, low speed cornering was much easier, high speed turns felt like i was going to lose it alot sooner, under heavy braking i had to really hold the steering wheel tight to keep the car going in a straight line and in the wet she was slippery as hell - at 160-170kms/hr i didnt notice much of difference between any of them though

[blueovalz]

Something to throw in here as well is with large positive offsets, camber greatly effects the "feel" on uneven surfaces as well. For the street I've found that the negative camber brings the feel back to a more OEM feel during normal driving. I had to experiment with it for a while once I starting driving the car on the street, but it has helped a lot.

[tonycharger72]

What is the factory Zed scrub radius?

[johnc]

Just to clarify, are you saying that increasing the track both front and rear, but increasing the fronts by a larger proportion is what will give you the benefits listed from 1 to 4?

 

No, increasing track front and rear gives you benefits 1, 3, and 4. Increasing front track a greater amount then the rear gives you 2.

 

It seems to me that it would be better to actually increase the factory track as basically i will end up with a better handling car,

 

Assuming you've done all the other things necessary to improve the handling of your Z, then yes. Track width changes that we are talking about here are a fine tuning tool. If you haven't already got the basics done, track width changes won't be noticeable.

 

So why on earth is this bloke, who seems to know alot about Zeds, so deadset against changing the track in any way shape or form???

 

He's a street guy. Remember, "Street is Slow!"

 

JohnC you used 10" rims with a 5.5" backspace, so a 0 offset, so that is not a huge change in track from factory really, only 15mm (of course you used spacers which changed it further, not massively though)

 

You don't need massive changes to see an improvement when driving the car at 10/10ths.

[boodlefoof]

Ideally you want to build longer control arms and a revised spindle to reap the benefits of both greater track width and reduced scrub.

[tonycharger72]

"Assuming you've done all the other things necessary to improve the handling of your Z, then yes. Track width changes that we are talking about here are a fine tuning tool. If you haven't already got the basics done, track width changes won't be noticeable."

 

What are all the other things necessary to improve the handling of your Z, what are the basics???

[johnc]

What are all the other things necessary to improve the handling of your Z, what are the basics???

 

Dude, I'm NOT going to retype what's already been posted in thousands of threads on this site. Search, search, search.

[tonycharger72]

Yeah, that was a bit lazy

 

But thanks so far you advice anyway champ, been very helpful

[tonycharger72]

Had a thought............

 

Just say you use 300zx front hubs, from my searching ive heard people say that this increases your front track by 18mm (bout 3/4"), could you not then choose a wheel which then decreased the front track so you could get close enough back to stock, ie.......using a wheel with a larger than 15+ (stock zed wheel offset) offset to decrease your track,

 

For Example:

300zx hubs increase the track out by 18mm,

Then you get your hands on a set of larger positive offset wheels, say 33+ offset (original Zed offset is 15+, and you have increased the front tack by 18mm with the 300zx hubs),

So by using the larger positive offset wheels, you can actually put the track back to stock,

 

I know there are benefits to increasing the front track, but i was just curious as to whether or not the above would actually work???