Effect of wider tires on alignment.

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Colt45ws

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Or rather if wider tires and wheels affects how it should be set.
Im asking because I have 255/45R18 on 18x9 Mustang fanblades and I notice I have to rotate every couple thousand because I seriously chew the inside edge of the tread on the front. Stock would have been P225/60R16 on 16x7. Im not talking about the physical alignment but how it is perceived by the tire. Im thinking the wider wheel is amplifying the camber and/or caster. Im just guessing here. Something that I had noticed while ago, but couldnt figure out was the Marauders are spec'd with less caster and more camber than mine which would be a base CV. Of course the range they give is so wide (+-0.75*) an MM could be set like mine and be 'in spec'. But anyway, Im wondering if that might be because they received wider tires. If it might be beneficial to have my car set to something close to the Marauder settings.
Base:
Caster 6.2*
Camber -0.4*
Marauder:
Caster 5.8*
Camber -0.5*
Police: (just 'cause)
Caster 6.0*
Camber -0.7
 
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What I found, normally the wider tyres need less negative camber and more toe-in in order to wear evenly.

You may check your toe and camber against the spec and adjust it to the maximum recommended setting and see if the problem still there.
 
Don't take the manufacturer specs too seriously as they are for normal recommended size tires. Since you deviate from the beaten path, why don't you experiment and start with zero camber and toe. Make small increment or decrement changes and see how that affects handling and tire wear. Then stick to what works for you. Do the same for the rear tires. Note that you should be in the driver's seat (and any other equivalent weight in the correct seat if you usually have a passenger) when the adjustments are changed.
 
I said the same thing, can't believe that's right.

In my experience the settings have to be tuned to the tires and driver. A really good shop knows this and will help you tweak them. If they don't get it then you need to try another.

Needless to say those bushings and such need to be extra tight and fresh as the tires are now loading them way beyond specs.
 
Originally Posted By: Colt45ws
Why do you think they would spec so much caster then?


Caster is generally spec'd to provide good steering return. I'm not sure of the technical term, but this is where the steering wheel returns to its straight ahead position without help from the driver.

What this actually does is add negative camber as the steering wheel is turned. Since your problem seems to be the inside shoulder, this is obviously contributing to it.

- and thanks for posting the alignment sheet, as there are a couple of items of interest there.

My experience is that any time the camber gets over a degree, there may be wear problems. If the toe is small, then you'll only get one sided wear (as you described). But if the toe is large, you'll also get irregular wear (some call this cupping wear, but I really don't like the term as this type of wear is usually diagnosed as coming from bad shocks or an out of balance condition.)

The spec sheet shows that the allowable tolerance for camber can generate camber over a degree.

But this spec sheet shows the problem I have to published alignment specs - the tolerance is too wide! These are the same tolerances that were allowable 40 years ago. Surely they can do better now! And my experince is that vehicles on the outer edges of these tolerances have tire wear problems. I think the tolerances should be half of what is published.

To put this in perspective: The spec sheet shows the tolerance for toe to be ±0.17°. BMW's tolerance is ±0.06°. So are the specs for the big rigs (the tractor in a tractor/trailer 18 wheeler!)

So I think you need to get the vehicle into the alignment shop and see what you have.
 
Originally Posted By: Colt45ws
Why do you think they would spec so much caster then?


Highway cruising.

You're barking up the right tree.
 
Well I was hoping to get it in someplace Friday; however, I woke early today and couldnt get back to sleep. So, I took it over there. Turns out they are booked solid until next Friday, so I have an appointment.
 
With wider tires less camber would be a good idea as stated above IMHO. The closer to 0° the better with wide tires/wheels or non-standard offsets. I wouldn't worry too much about the caster; that said, it should be kept near the manufacturer's specs. The cross caster and cross camber are more important; I would recommend less than +/-0.20° for both cross camber & cross caster, with a slightly positive cross camber and a slightly negative cross camber being ideal if 0° cannot be achieved.
The specs call for -0.15° toe on the base CV and the police model. The Marauder calls for -0.13°. Too much negative toe tends to wear the tires on the inside. RWD vehicles usually need positive toe (toe-in); it is unusual for them to call for negative toe (toe-out). I would also set the toe at 0.00° as stated above and go from there. You never know, it might even need a little bit of positive toe.
Another good point stated above is that the manufacturer's tolerances are too wide. In my shop we try align within the following tolerances: cross camber +/-0.20°; cross caster for manual steering +/-0.20°; cross caster for power steering +/-0.40°; and total toe +/-0.02° from spec. i.e., if the spec calls for a total toe of +0.24°; it must be between 0.22° & 0.26°.
 
Any one of those specs will be fine.
What is most important is to have both sides EVEN!
And don't go crazy with excessive toe in/out.
A hair toe in is good.
 
Got it in today. Camber was only about -1.5° on both sides. [Sarcasm]Not that far out at all. I wonder how they wore so fast.[/Sarcasm]
They cranked them to -0.6°. So we shall see what it does going forward.
 
Originally Posted By: Colt45ws
Got it in today. Camber was only about -1.5° on both sides. [Sarcasm]Not that far out at all. I wonder how they wore so fast.[/Sarcasm]
They cranked them to -0.6°. So we shall see what it does going forward.

The wear is determined more by the toe rather than camber, so make sure the toe is correct.
 
There was no feathering or anything like that. Wear was pretty much even from out side until the last tread block. When I finally took of my last set of tires off they had been in their positions for 5000 miles. The middle was 4/32 and the inside tread block was flat gone.
 
Originally Posted By: kr_bitog

The wear is determined more by the toe rather than camber, so make sure the toe is correct.


Not True...

Both Camber and Toe are Tire Wear Angles.

Hope this helps, Jim
 
Originally Posted By: AstroTurf
Originally Posted By: kr_bitog

The wear is determined more by the toe rather than camber, so make sure the toe is correct.

Not True...
Both Camber and Toe are Tire Wear Angles.
Hope this helps, Jim


Actually, camber affects the even-ness of wear, not the wear rate. Toe greatly affects the wear rate and is a multiplier for other mis-alignment conditions such as camber.

So I think KR is correct. Toe is the most important alignment parameter, but camber and caster should not be ignored.
 
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Originally Posted By: CapriRacer
Originally Posted By: AstroTurf
Originally Posted By: kr_bitog

The wear is determined more by the toe rather than camber, so make sure the toe is correct.

Not True...
Both Camber and Toe are Tire Wear Angles.
Hope this helps, Jim


Actually, camber affects the even-ness of wear, not the wear rate. Toe greatly affects the wear rate and is a multiplier for other mis-alignment conditions such as camber.

So I think KR is correct. Toe is the most important alignment parameter, but camber and caster should not be ignored.


That School of Thought holds true for 99.9% of the repair facilities with alignment equipment.

For the other 0.01% of the Professional Alignment Shops it does not.

Set the Toe and Go, Set the Toe and Go...

Glad it was finally corrected for the OP, Jim
 
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