Front tires

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Brian Donahue

Brian Donahue

Exhaust system
Joined
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I need to rebuild my 1973 440 Duster front suspension and replace the front tires. I just bought the car so I can only speak for what I can see on the car. The current tires are 205/60/R15, and are badly worn on the outside edges, down to the steel belts. The rear tires are 255/60/15.

Obviously I have suspension/alignment issues. I noticed in some test driving that the car likes to follow changes in the contour of the road. It will pull strongly at 40-45 mph in the direction of dips in the road. I need to replace the tires and I am considering using 50 aspect ratio instead of 60. My reasoning is two fold, the 50's will lower the front of the car another 3/4". The car does need to be lowered a bit now and I will lower the rear end as well prior to alignment. The 50 aspect will also strengthen the sidewall from flex. With all things being equal, good alignment and suspension rebuild, will the stronger sidewall (50 aspect) keep the car from pulling better than the 60 aspect sidewall?

I know I need alignment etc, but I need to set car height first and have tires I can drive to the shop with to get the alignment set. For that reason, I need to make a tire choice first as it affects height of the car.
 
That car has a severe tow issue (from whatever), and sidewalls are not why it tracks like it does.
It tracks like it does because of the tires fighting each other because of the alignment and possible front end parts issue's.

But yea, shorter usually equals more stable so just pick the tires you like and get the front end taken care of.
 
TrailBeast said:
That car has a severe tow issue (from whatever), and sidewalls are not why it tracks like it does.
It tracks like it does because of the tires fighting each other because of the alignment and possible front end parts issue's.

But yea, shorter usually equals more stable so just pick the tires you like and get the front end taken care of.
Click to expand...
Thanks, I am sure I will find plenty that will fix this in that suspension, just gotta start somewhere. Waiting to hear from K Dog as well.
 
a 205/60R15 is a good size for a big block duster. lower the front by adjusting torsion bars. check all front end components and get a custom (not stock) alignment
 
Wider tires amplify the tendency to wander, if the alignment isn't perfect. Lower profile tires will amplify the shock of hitting potholes into the chassis.
A Lower ride height will also allow hitting the bumpstops earlier,and crashing low- hanging stuff under your car into things. Stuff like headers and deep pans.
A ride height other than stock or near stock, will also make it tough or even,impossible to get any significant positive caster with the factory parts and adjusters. Lack of positive caster leads to wander and high-speed instability.
>The factory ride height is not measured the way you might think. It references the inner and outer ends of the lower control arm and specifies a difference to the ground-plane. So a true factory ride height can be correct with any size tire, by sticking to the spec.This factory "ride height" is specified so that all the other alignment parameters will fall into their sweetspots , and you,the driver, will not have anything to complain about.
Choosing tires that are not of the factory diameter,or rims not of the factory offset, messes with the scrub radius. If you get too far outside this little nugget, and you crank up the negative camber, then the car starts to wander, again.
>The alignment tech will set your alignment to the straight ahead specs.Or to the straight ahead specs you specify. But if your junk is not close to what the factory junk was, and if you then have steering issues, don't fault the tech. For the most part, those guys just slam cars thru the bay, trying to pay their bills.If you got non factory parts, or want an alignment to custom specs, you need to be aware that it takes time to get it right. And time costs money.

If you want a non-stock ride height, now I am talking the height of the front K relative to the ground-plane, then it is better to achieve this with tire diameters, than it is to fudge the T-bar adjusters. Just keep an eye on the scrub radius.
 
Marcohotrod said:
a 205/60R15 is a good size for a big block duster. lower the front by adjusting torsion bars. check all front end components and get a custom (not stock) alignment
Click to expand...
I`m running 205 65 15 on my 440/505 fastback, w/ an aftermarket front end, it doesn`t seem to follow cracks and sloping roads.
 
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