[JLMounce]

Originally Posted by jhein

Thanks for all the replies. All very good. So it seems like street tires of any sort won't really solve this. Suspension changes would help but with potentially significant mods. Caltracs would be a fairly minor modification that's reversible. But since my car is street, not strip, just wondering how that would impact other street driving behavior, especially cornering? They say it's not compatible with the factory sway bar. It seems like if you trimmed the ends it would fit. Is there any other reason not to use the Caltracs and the sway bar? Does the Caltracs have anti-sway properties?

In general, the modifications and add-ons necessary to make a leaf spring work for straight line traction reduces it's handling prowess.

The problem with leaf springs is that they act as the suspension forward links, lateral movement control and a spring all in one. They actually do a pretty damn good job of being a jack of all trades, up until the point that they don't.

I've never run one, but theoretically, running a watts link or panhard bar with your leaf setup may help straight line traction. It takes one of the jobs away from the leaf springs and in doing so, allows the leaf to be a better spring and a better link. The propeller bolt of the watts link also takes over as the roll center (at least until bind occurs) and that is really helpful when it comes to putting power down on corner exit. If you look at vintage TA style race cars that are required by rules to run their original style leafs, almost all of them will have a panhard bar or watts link installed as well.

A Fays 2 Watts link is a completely bolt on deal and is reversible. I don't know that it's going to be as good as a cal-trac and it's certainly not going to be as good as a 4 link or torque arm.

I will say that most of the 4 link kits available are going to largely be reversible as well. The Ridetech system bolts the cradle to the frame rails and does not require physical welding to the car. Just a couple tabs that get welded on to the top of the axle tubes. This is fairly easily reversible if you're worried about that.

If you decide to go to larger wheels, that opens you up to a lot more tire options, specifically tires designed for autocross. The Falken Azenis RT615K+ is a 200 tread wear tire that will provide quite a bit more grip than what is available in 15" sizes. I had these on my previous 17" wheels and traction was really good. They aren't as comfortable as the NT555G2's are, but it's a competition tire with stiff sidewalls...some trade-offs are always necessary.

I recommend that tire, specifically because it's designed to last a bit longer. There are autocross tires with more stick, but they'll wear faster.

[jhein]

Originally Posted by JLMounce

In general, the modifications and add-ons necessary to make a leaf spring work for straight line traction reduces it's handling prowess.

The problem with leaf springs is that they act as the suspension forward links, lateral movement control and a spring all in one. They actually do a pretty damn good job of being a jack of all trades, up until the point that they don't.

I've never run one, but theoretically, running a watts link or panhard bar with your leaf setup may help straight line traction. It takes one of the jobs away from the leaf springs and in doing so, allows the leaf to be a better spring and a better link. The propeller bolt of the watts link also takes over as the roll center (at least until bind occurs) and that is really helpful when it comes to putting power down on corner exit. If you look at vintage TA style race cars that are required by rules to run their original style leafs, almost all of them will have a panhard bar or watts link installed as well.

A Fays 2 Watts link is a completely bolt on deal and is reversible. I don't know that it's going to be as good as a cal-trac and it's certainly not going to be as good as a 4 link or torque arm.

I will say that most of the 4 link kits available are going to largely be reversible as well. The Ridetech system bolts the cradle to the frame rails and does not require physical welding to the car. Just a couple tabs that get welded on to the top of the axle tubes. This is fairly easily reversible if you're worried about that.

If you decide to go to larger wheels, that opens you up to a lot more tire options, specifically tires designed for autocross. The Falken Azenis RT615K+ is a 200 tread wear tire that will provide quite a bit more grip than what is available in 15" sizes. I had these on my previous 17" wheels and traction was really good. They aren't as comfortable as the NT555G2's are, but it's a competition tire with stiff sidewalls...some trade-offs are always necessary.

I recommend that tire, specifically because it's designed to last a bit longer. There are autocross tires with more stick, but they'll wear faster.

That Falken tire looks fantastic but I don't see a size that will work for me.

[JLMounce]

Originally Posted by jhein

That Falken tire looks fantastic but I don't see a size that will work for me.

You would be required to move to a 17" wheel or larger to run this type of tire. You should be able to run a 9" wide wheel in the back, you'd run a 275/40/17, which is close to a 26" tall tire. If you can only run an 8" wheel, you'd run the 245/45/17 which is the same height.

I put this together quickly on my lunch however. It's a "good enough" plot of the anti-squat line on my car. If you know your total vehicle weights and front and rear weights it's fairly easy to plot.

My car weighs 2000 lbs on the front and 1402 lbs on the rear for a total of 3402 lbs. My car has a measured wheel base of 107". If you take 1402 x 107 you end up with 150014. Divide that by total vehicle weight of 3402 and you get 44.10 which is inches from your front centerline. This give your your center of gravity position behind the front wheels, but does not give you it's height.

The easiest way to do this and how most people do so is to use the height of the cam. There is a formula to arrive at the exact height but it involves taking weight measurements front and rear, the independently lifting the car 10" front and rear and taking measurements again. For most purposes, using cam height is good enough.

You'll see the CG as the top most blue dot on my car door. The lower blue dot is the location of the forward spring eye on the leaf spring. This is your forward link and where all torque is being applied to push your car.

Now you can draw a line from the centerline of the bottom of the tire, up to your CG and see where your forward link is in relation to the anti-squat line. Notice on mine that my forward link is below the AS line. Not by a lot, but definitely below. This would be a percentage of AS below 100%. Lets' call it 97% here.

What this means practically is that my suspension will allow a bit of squat under power. This increases the suspensions ability to deal with uneven pavement, bumps, or even acceleration off corner. However because the suspension is allowing some squat, available power to the wheels is reduced and some traction is lost.

Notice that with a leaf spring, the physical mounting point determines your anti-squat, unlike a link style suspension. What that means is you can play around with your anti-squat by changing the relationship of the mounting point to the AS line. If you lower the front of the car, this will tend to increase AS. If you raise the rear, especially in relation to the front, your AS will increase.

Drag cars will run AS percentages between 120%-150% or so, depending on the type of suspension, tire used etc. It's not an end all be all here, but it gives you an idea of what you're up against with a leaf. All of this also assumes that you aren't overpowering the leaf and causing axle wrap. The wave that forms in the leaf pack when this occurs loads and unloads the tires. In this situation you'll either blow the tires off completely, or induce wheel hop. That's one of the things the cal-trac is aiding in. It's also adding some separation of the suspension, making it act like it's got more AS percentage.

On a performance street car that cares about more than going fast in a straight line, having AS percentages below 100 is pretty typical. This becomes somewhat neutral and provides off corner traction, braking stability and less oversteer.

Might be worth taking 20 minutes and plotting this on your car. Might be eye opening to see where it is.

[jhein]

Originally Posted by JLMounce

You would be required to move to a 17" wheel or larger to run this type of tire. You should be able to run a 9" wide wheel in the back, you'd run a 275/40/17, which is close to a 26" tall tire. If you can only run an 8" wheel, you'd run the 245/45/17 which is the same height.

I put this together quickly on my lunch however. It's a "good enough" plot of the anti-squat line on my car. If you know your total vehicle weights and front and rear weights it's fairly easy to plot.

My car weighs 2000 lbs on the front and 1402 lbs on the rear for a total of 3402 lbs. My car has a measured wheel base of 107". If you take 1402 x 107 you end up with 150014. Divide that by total vehicle weight of 3402 and you get 44.10 which is inches from your front centerline. This give your your center of gravity position behind the front wheels, but does not give you it's height.

The easiest way to do this and how most people do so is to use the height of the cam. There is a formula to arrive at the exact height but it involves taking weight measurements front and rear, the independently lifting the car 10" front and rear and taking measurements again. For most purposes, using cam height is good enough.

You'll see the CG as the top most blue dot on my car door. The lower blue dot is the location of the forward spring eye on the leaf spring. This is your forward link and where all torque is being applied to push your car.

Now you can draw a line from the centerline of the bottom of the tire, up to your CG and see where your forward link is in relation to the anti-squat line. Notice on mine that my forward link is below the AS line. Not by a lot, but definitely below. This would be a percentage of AS below 100%. Lets' call it 97% here.

What this means practically is that my suspension will allow a bit of squat under power. This increases the suspensions ability to deal with uneven pavement, bumps, or even acceleration off corner. However because the suspension is allowing some squat, available power to the wheels is reduced and some traction is lost.

Notice that with a leaf spring, the physical mounting point determines your anti-squat, unlike a link style suspension. What that means is you can play around with your anti-squat by changing the relationship of the mounting point to the AS line. If you lower the front of the car, this will tend to increase AS. If you raise the rear, especially in relation to the front, your AS will increase.

Drag cars will run AS percentages between 120%-150% or so, depending on the type of suspension, tire used etc. It's not an end all be all here, but it gives you an idea of what you're up against with a leaf. All of this also assumes that you aren't overpowering the leaf and causing axle wrap. The wave that forms in the leaf pack when this occurs loads and unloads the tires. In this situation you'll either blow the tires off completely, or induce wheel hop. That's one of the things the cal-trac is aiding in. It's also adding some separation of the suspension, making it act like it's got more AS percentage.

On a performance street car that cares about more than going fast in a straight line, having AS percentages below 100 is pretty typical. This becomes somewhat neutral and provides off corner traction, braking stability and less oversteer.

Might be worth taking 20 minutes and plotting this on your car. Might be eye opening to see where it is.

Attachment 655598

Very interesting. I'll have to go weight my car and plot that out.

As for the tires, a 25.6 inch tire is pretty small. I know we're talking about performance here but I wouldn't like that look.

[JLMounce]

Originally Posted by jhein

Very interesting. I'll have to go weight my car and plot that out.

As for the tires, a 25.6 inch tire is pretty small. I know we're talking about performance here but I wouldn't like that look.

Yeah I went back and realized you're running a 27" tire. There's only a single 27" tire offering in the Azenis line which is a 295/40/18. So you'd need an 18" wheel, which honestly is a better size currently. There's far more tire options in 18" wheels than there are 17" wheels now.

I'm fairly certain a 10" wheel with a 295 tire is possible on a stock tub 2nd gen, but you'd have to measure it out if you went that route. The problem is that there's no sizing like that available for the fronts.

Honestly, you're in enough of a quagmire here based on the look you're after as well as what you are and aren't willing to modify, that you're going to have to choose between longer lasting street tires that don't provide the level of traction you're after, or drag radials that provide the traction you're after, but need replaced often.

Edit: Completely forgot about these for 2nd gens.

https://www.pro-touringf-body.com/pr...squat-brackets

PTFB and Global West both make an anti-squat front eye mount for the leaf springs. The PTFB version raises the front eye 7/8" of an inch. It will lower the rear about 1/2" further though. Might be worth a call over to PTFB and see what they have to say about your current issues.

[twilightTA]

I’m running 17”s on my 77 TA. I had the Nitto NT555 tires and switched to Continental ExtremeContact Sports. More expensive but they perform a ton better than the Nittos did.