[kingbuzzo]

It was the style at the time...



Clarence is always an issue...especially with the wagon trails we have for roads around here...good luck!

[HWYSTR455]

Nice Steve, always enjoy seeing pics of your car!

Bet the 300# leafs help control squat!


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[Steve C.]

Thanks.

Help control squat and no rear sway bar is needed.

At the time I purchased the CalTracs Traction Bars those were the Landrum leafsprings John Calvert was recommending with their use.
Now today today its Calvert’s Split Mono Leafsprings.


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[b-man]

1970 called…..

Seriously guys anyone can jack up the rear suspension to the moon and anything’s gonna ‘fit’.

It takes some careful figuring to get something that actually does fit without having to raise up the car.

[Steve C.]

Landrum Performance Springs / Technical Information


https://landrumspring.com/leaf-sprin...l-information/


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[ta man]

Originally Posted by HWYSTR455

Nice Steve, always enjoy seeing pics of your car!

Bet the 300# leafs help control squat!


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I need to find a picture of my car launching, I have Calvert split monos and Caltracs and the rear body of the car actually rises as the rearend is forced down. I may have a video somewhere.

[Steve C.]

Comments from this thread might be of interest....

https://forums.maxperformanceinc.com...d.php?t=864002



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[HWYSTR455]

Pretty sure my multi-leafs are #220 but would have to check.

Wasn't sure if they were going to be too much but am now thinking not!


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[thepontiacman]

Thanks to everyone for all the help.

His car won Best Muscle Car at a recent show.


Sent from my moto g power 5G - 2023 using Tapatalk

[HWYSTR455]

Originally Posted by thepontiacman

Thanks to everyone for all the help.

His car won Best Muscle Car at a recent show.


Sent from my moto g power 5G - 2023 using Tapatalk

Very nice! Post a pic!

[thepontiacman]

More pics

[R 70 Judge]

Originally Posted by HWYSTR455

If you run a wider tire on a narrow(er) wheel, that 'bulge' takes away from what you can fit, not to mention it's not safe. It is possible for the tire to roll off the wheel. Also, on a dip or bump as the suspension compresses, the bulge can contact the lip and blow a tire.

If you run a 'bulge', you actually can only fit a narrower tire than without a bulge.

An option that helps is you can roll the lips, but more prefer not to do that.

Several things need to be known before trying to fit the widest possible tire on a 2nd gen F:

The 'baseline' wheel size on a 2nd gen F is 15x8 with zero offset. Or, in other terms, 4" back space. (EDIT: or 4.5")

Some wheel manufacturers measure width differently, so it's important to know that.

The distance to the wheel lip from the rear end flange is closer to the lip on the passenger side than the driver's side. So measure both sides.

When doing offset calculations, understand it's not just the fender lip that you need to watch, it's also the leaf. In some cases, the leaf buckle.

Tire 'squirm' can make contact even though they clear at stand still. Like around turns.

In general, you can't go more than 4" outboard on the wheel due to fender lip contact. That accounts for squirm/tire roll. (and no bulge). So when going to an aftermarket wheel, changes to width should be made towards the inside.

On like 74-up, there's also the seat belt bulge that can make contact. Might be '75-up or so.

b-man is correct, 'section widths' do vary, and you have to check/take into account. Keep in mind that measurement does not take into account for bulge when running a tire on 'unapproved' widths.

You should be able to do a 275/60-15 on a 15x8 wheel with 4.5 backspacing. A 15x9 with 5 or so backspacing would be a better choice though. And, it will depend more so on the tire.

That is not taking into account if you added disc brakes to an OE width rear.

The Herb Adams VSE catalog (should be able to find one) outlines much of this and is a good reference.

Just to say, it is possible to go too wide on a tire. As the contact patch increases, the corner weight gets distributed over a larger area and will not have as much downforce.

Just look how 10.5 cars can hook so well.

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Great info here

It’s surprising how big of a tire you can cram into a f-body. This is a 30x12.5 ET Street biasply tire.

[OLDFLM72]

That's how you tuck a wide tire! Not the 80's stink bug stance with the tires hanging 2 inches outside the fender lip. I did that with my car in high school (1985)! Haha

ps. It tucks a 295/40/18 on an 18x10 now fwiw.

[HWYSTR455]

Originally Posted by OLDFLM72

That's how you tuck a wide tire! Not the 80's stink bug stance with the tires hanging 2 inches outside the fender lip. I did that with my car in high school (1985)! Haha

ps. It tucks a 295/40/18 on an 18x10 now fwiw.

That's my current setup, 18x10 6" backspacing, 295/40/18. It will fit a 305 but I couldn't find a matching front tire for it. If I could have gotten an 18x11 with 7 - 7.5" backspacing I could have went with a 325.

This is with no weight in the car, it was gutted, but gives you an idea.

I did roll the lips, and have a 265/40/18 on the front with a 18x9 with 5" backspacing, and could have gotten a 275 up there, but couldn't get one in the series that I wanted.

The tires are from like 2002, so I will be shopping once I get it back from paint jail. Should be in a few weeks.


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[zippy]

Originally Posted by HWYSTR455

The distance to the wheel lip from the rear end flange is closer to the lip on the passenger side than the driver's side. So measure both sides.


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You meaning Hub flange to wheel opening lip? My TA, the drivers side sticks out further from the wheel lip than the pass. 275/4518. But have had to roll the DS rear inner fender to minimze tire rubing Pass side fine. Is that common for them (axles) to not be centered in firebirds?

[HWYSTR455]

Originally Posted by zippy

You meaning Hub flange to wheel opening lip? My TA, the drivers side sticks out further from the wheel lip than the pass. 275/4518. But have had to roll the DS rear inner fender to minimze tire rubing Pass side fine. Is that common for them (axles) to not be centered in firebirds?

My understanding is in order to maintain the same axle length on both sides the housing was offset to the passenger side, but maybe I have the side mixed up?

The reason it needs to be offset is due to the pinion to ring gear relationship. The offset allows the centerline of the pinion to be on the same plane/centerline as the rest of the driveline.

So the side the ring gear is on the housing is further to the outside the body.

The choice GM had to make was, make 2 diff length axles ($$$) or offset the housing.

Others may have more detailed info on this than I do, but i came across this at one point trying to fit the largest wheel/tire combo as possible (in the early 80s).


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[HWYSTR455]

Yup, I got the sides mixed up...


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[Steve C.]

Very common with 2nd generation Camaro and firebird where the rear-end is offset to one side.

Ride height topic for 2nd Gen if interested....

https://forums.maxperformanceinc.com...ht=ride+height

( AMA Specifications in my post #10 )

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[R 70 Judge]

Just so you know, a 15x10 with 5.5” backspacing fits as well. I’ll try to get a picture of how these look on my car. They are Billet Specialties Single Bead Lock Win Lites. 15x10 5.5” BS rear with MT 275/60/15 ET Street R Radials.

The fronts are 15x4 1.625” BS. I did some research and the 15x4 2.25” BS sucks the wheel too far into the wheel well for my liking. I even spoke to tech at Billet Specialties and they said the same and recommended the 1.625” BS.

[hojs69]

Here are 315 / 35 x 17 rear tires on one of my sons.