Re: Clare - are smaller car tires easier to balance than SUV tires?

On Wed, 12 Jun 2019 21:37:49 -0400, Clare Snyder wrote:


Thanks Clare as I never mounted and balanced a tire so fast on purpose, not even taking time to clean the wheel or even remove the old weights until AFTER I put it on the static balance stand.
These tires are Lexani LXTR 203 model tires, of size P185/65R14 with load range 86 and speed range H (traction A, temperature A, and treadwear 500), where I don't know WHAT specific thing makes these so easy to balance, but they're so easy that something is very different.
I was surprised that I skipped a bunch of steps, and yet, the wheel _still_ didn't cause any perceptible vibration, according to the driver, even as it's a front wheel drive vehicle with the tire being the driver side front tire.
I had told the owner to take it to Costco for the $5 wheel balancing, but that wasn't even necessary, even as I skipped a bunch of balancing steps.
The old tires on her car were model "Grand Prix" of size P185/65R14 load range 86 and speed of T (traction A, temperature B, and treadwear 500) which seem to be wearing on both edges, where here are the front two tires of this FWD vehicle with the tires set up in the appropriate position. <
https://i.postimg.cc/JzvTyjKg/mount18.jpg

I had previously replaced her passenger front tire due to this gouge <
https://i.postimg.cc/4dTBPZDQ/mount19.jpg

Where the driver front tire wore into the steel belts which jutted out <
https://i.postimg.cc/85Bwn9DQ/mount20.jpg

She needed to be somewhere so I was in such a rush, that I didn't even _see_ the yellow (weight) dot when I mounted the valve stem to the red (uniformity) dot: <
https://i.postimg.cc/7L8HPbtb/mount16.jpg

Where I only noticed the yellow dot when I looked at this picture! <
https://i.postimg.cc/kG1M7cLd/mount15.jpg

Back to how easy it was to statically balance these tires, not only did this tiny car have the only four-lug wheel I've ever worked on, but popping the first bead of this tiny 14-inch P185 tire was so simple that it took only a couple of pumps and about triple that to break the second bead.
Removing the third bead and fourth bead was, likewise, surprisingly simple. Popping on the fifth bead was almost entirely done by hand, it was that easy, where only the sixth bead took any effort whatsoever that required a force that any teenager could exert.
With two wheel weights already on the rim, and by match mounting the red dot (I didn't even _see_ that yellow dot until I looked at the picture afterward), the balance was spot on in the middle of the bubble level.
So I didn't even remove the _old_ wheel weights, which I normally would have done as part of the wheel prep after breaking the bead and removing the old tire. I didn't even replace the valve stem, as I recently used up the four valve stems I had bought after speaking to you about getting the bolt-in kind so I didn't have any available.
The tires have been waiting for her outside in the mud and rain, so I simply bounced and blew out the leaves and crud where I would have cleaned the tires more had I more time, where I might have noticed that yellow dot which was slightly worn away from being outside all winter.

Funny you mention the Hankook's where I just snapped this for you! <
https://i.postimg.cc/zGVtXxwK/mount17.jpg

Those are Hancook Optimo H724 model tires of size P225/75R15, with the load range of 102 and speed range of S (traction A, temperature B, and treadwear 500), which were MUCH HARDER to mount and dismount and harder to balance too, it seems.
I'm planning on mounting and balancing them this weekend on an SUV which keeps wearing out the front tires which I have to get alignment tools to check the camber mostly since they're wearing on the outside edge.
When I mount those thick-sided Hancooks, on steel wheels, I will mount by the _yellow_ (minimum weight) dot for the first time, instead of by the red (maximum runout) dot, as I recall you recommended for when there's no match mounting mark on the rims.
Thanks for being helpful where you're just about the only guy on this newsgroup who knows anything about this subject matter, which I greatly appreciate your advice, and where I try to remember it all over the years, where I'm starting to lose count of how many tires I've done in the past five years with the crappy Harbor Freight tools (they work, but they suck).
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On 13/6/19 2:32 pm, Arlen G. Holder wrote:

You can check the camber all you like but the answer is more likely in the SAI angles and you will be able to do SFA about that. Quiz the owner about type of use instead. If it is all city and suburban driving, tyre wear on the outside of the tread can be considered 100% normal. Turn the wheels to a high level of lock and the obvious will confront you. The type of feathering will tell you what the actual cause is.

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Xeno


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On Fri, 14 Jun 2019 12:58:31 +1000, Xeno wrote:

Hi Xeno, I typed up a super detailed response, after viewing every second of those three videos, where the first and last seem to have the same graphics, and the middle (whiteboard) one was a bit different - and where that wheelcam shot of the tire literally bending away from the rim - and the temperature methods of determining footprint on hard cornering were illuminating.
I hate losing data, but I lost it when the PC rebooted, so suffice to say I appreciate the videos, from which I learned good stuff, particularly about that "scrub radius".
I didn't find a lot on the net about "camber scrub", and those videos didn't cover specific tire wear on the slow speed (less than 40mph) constantly lock-to-lock turns we perform on the mountain, where the goal is how to modify the set up for the vehicle in a compromise to minimize that 'camber scrub' on FWD and RWD vehicles without adversely affecting straight-line handling.

Everyone says you need a perfectly flat garage floor, which, as far as I know, mine is pretty flat based on putting a level on it - but I don't really know how flat is flat enough.
Given that a millimeter or two of height adjustment in any one corner might be necessary for most garages, I guess your suggestion above adds two nice-to-have tools to the home DIY alignment check mix... o Steering wheel centering lock o Some kind of way to put the 4 wheels on a wormscrew-adjusted plate
Googling found the first, but the second was in the thousand dollar range.
Are there good redneck solutions for leveling the four tires?
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On 15/6/19 2:55 am, Arlen G. Holder wrote:

Yes, I learnt a couple of points from those videos too so it seems you can teach old dogs new tricks. I have found, in order to gain a better appreciation of steering geometry and suspension systems, one needs to look at those places that are extreme. In this case, it's in motor racing.

You won't. Information on it is scarce since it is an undesired effect. However, if you look at what the wheel is doing vis a vis camber during high angle (note - not high speed) cornering, then you can visualise the issue. Note too that tread blocks have a limited degree of flexibility and, as such, are likely to exceed that during high angle cornering resulting in tread scrubbing.

The reality is that you are faced with a *compromise* and there are many such in steering and suspension geometry. Any gain in the tyre wear scenario will negatively affect high speed. If you happen to see a Porsche Cayenne in a parking lot with its wheels turned at a high angle, the camber angle displayed will amaze you. I know it amazed me. Of course, when you realise that vehicle's suspension is *optimised* for high speed and high power operation in a very narrow band either side of straight ahead, it all makes sense.

A level will only give you a localised point. You need something that can verify any point in the garage floor against a common datum point. These can be used for that purpose and aren't expensive; https://www.bosch-do-it.com/au/en/diy/tools/pll-360-set-3165140562898-199931.jsp Or you could hire one for a day just to verify your garage floor. A professional one of these should have been used when the floor was poured and leveled anyway.

Most wheel aligners that I have used come with ramps that have the added benefit of raising the vehicle a couple of feet off the floor. Ramps, even without the aligner heads, provide a relatively easy means of leveling the required work area. They don't even need to be raised more than an inch or two. If the floor area is really out of whack, two or four ramps made of wood of varying thicknesses might suffice. You can even check the level easily these days with laser levels as I mentioned above. My brother has one of the professional units since he is a concreter but cheaper DIY versions, like the one in the link, should suffice for this purpose.
--

Xeno


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On Sat, 15 Jun 2019 14:14:27 +1000, Xeno wrote:

Hi Xeno,
While I don't race, our conditions are "extreme" enough, in that constant incessant repeated nearly full back-to-back wheel locks are causing "something" to scrape away rubber, so this "camber scrub" is intriguing.
I snapped this photo of tires that I mounted about a month ago, which only have about 1000 miles on them, where they clearly show this pattern which "might" be what you've been referring to as "camber scrub". <
https://i.postimg.cc/zvvyL2tq/mount24.jpg

Does _that_ feathering look like what you're referring to as "camber scrub"?
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On 16/6/19 4:31 pm, Arlen G. Holder wrote:

That is also considered *extreme* even though you aren't doing it fast.

It does indeed! Same kind of feathering I'm getting on my Toyota's front tyres - a feathering that you can easily feel in the early stages as you run your hands for and aft along that section of tread area. Now try to imagine what those tread blocks are doing as they roll around in a tight circle with heaps of camber gain. It's not pretty and, worse, there is SFA you can do about it.
BTW, positive caster will accentuate the camber scrub. Caster is generally not a tyre wearing angle. However, the more caster your steering has, the more camber *change* you will get when turning the steering. Positive caster will give you a beneficial gain in terms of handling. You will get more camber gain (more +ve) on the inside wheel but the outside wheel will experience camber *loss* and become more vertical or even negative. Since the more vertical tyre is on the outside, the tread will get more grip with reduced slip angle aided by weight transfer. This is great for cornering at speed. However when travelling at slow speeds, weight transfer is not as significant and the camber angle on the inside wheel, the one at the tightest lock, heads towards positive extremes. It is, in effect, riding heavily on the outer edge of the tread and this is where, and why, the damage is being done. The tread blocks have only so much flex before they are forced to break contact with the road and slide. You've seen the evidence of what that does.
Caster specifications are usually given as a range, say between 1 and 2 degrees with a side to side variation limit. All you can really do to mitigate the effect is to set your caster to the low end of the specified range.
--

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On Sun, 16 Jun 2019 20:40:34 +1000, Xeno wrote:

Thanks for that information, where the one correction I need to make is that you can only feel this feathering running your hand "*backward*" (clockwise) over the outside quarter of the tread pattern. <
https://i.postimg.cc/zvvyL2tq/mount24.jpg

If you run your hand toward the front (counterclockwise), you can't feel the feathering because each "lip" is downward. <
https://i.postimg.cc/vTZLmZrN/mount25.jpg

When you run your hand toward the rear of the vehicle, each lip is upward. <
https://i.postimg.cc/X7hcV3ps/mount26.jpg

That's the oddity. The feathering is only one way. <
https://i.postimg.cc/KYhPMN7L/mount27.jpg

It's reproducible for years - so it's always the same. That one-way lip feathering should be diagnostic, should it not? <
https://i.postimg.cc/Wzyrb6bd/mount28.jpg
> BTW, positive caster will accentuate the camber scrub. Caster is

Hmmmmmmmm.... maybe I can consider lessening positive caster a teeny bit?

This is very useful information, as all our lock-to-lock cornering is at 30mph to 40mph ... never faster because I ran a test last week where anything over 40mph is impossible to do even remotely safely, as all the turns are blind turns and the file miles of 9% twisty road can't even be twenty feet wide at the maximum (I should measure it but it's something like that, as it's too narrow for the county to center stripe it legally).

I need to study more - where your conclusion is spot on perfect but where I don't get the individual steps only because I think of alignment as being 'static' so to speak. I know it changes - but my brain doesn't know 'how' it changes under those slow speed lock-to-lock downhill (or uphill) turns.

Yes. That's for sure. The outer tread blocks "feather" such that you can feel it, and barely see it, after about 1000 miles. The only thing I can do, is change the alignment or rotate every 1000 miles (but even rotation won't stop it - it just evens it out with the rears).

That's EXACTLY what I'll do! I have to admit I need to read, and re-read and re-read again what you wrote above, as my brain needs to work in step-by-step fashion.
You didn't skip a step but I don't quite "believe" in my brain all the steps, if you know what I mean. It's not that I don't believe you, but that my brain has to understand EACH step before moving to the next step when it comes to UNDERSTANDING why this happens. (It's kind of like a series of math equations where I need to understand every step.)
On the other hand, once there is a conclusion, I can EXPERIMENT easily, which is how a lot of cars get fixed (by throwing parts at the problems without understanding them). So I will change the caster.
I have an alignment shop which runs a sale for $30 off to drop the $160 price to $130 who lessened my bimmer's rear camber from negative 2 degrees to almost 0 degrees - where if I go to him - I can ask for the least caster in the spec.
Better yet, I need to buy the tools to do that caster change myself - but that's a topic for a different thread since I have to MEASURE it first.
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Arlen G. Holder wrote: "maybe I can consider lessening positive caster a teeny bit? "
At the risk of slightly less self-centering.
If anything, I'd accept slightly more edge wear and max the caster, within specs. Most cars I've driven since 1980 have video-game steering feel - not safe in my estimation!
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On 17/6/19 6:53 am, snipped-for-privacy@gmail.com wrote:

It really is a case of trying it and seeing. Most cars now have power steering and loss of feel is because of that in many cases. I have to say that road feel with power steering has been vastly improved over those vehicles from the 80s and before. The engineers have a much better understanding of the feedback mechanisms involved.
I have come to accept more edge wear with my car. As I said in a previous post, I still get 60,000 kilometres out of a set of tyres with regular rotation.
--

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Xeno wrote: " It really is a case of trying it and seeing. Most cars now have power steering and loss of feel is because of that in many cases. I have to say that road feel with power steering has been vastly improved over those vehicles from the 80s and before. The engineers have a much better understanding of the feedback mechanisms involved.
I have come to accept more edge wear with my car. As I said in a previous post, I still get 60,000 kilometres out of a set of tyres with regular rotation. "
Actually, two developments have led to a slight *decrease* in road feel and steering heft:
(1) The adoption of EPS(electric power steering. During the first five years of the spread of EPS, engineers inadvertantly built so much boost into the new motors that some cars had trouble with returnability of the front wheels!
I also made the mistake of buying the car that, at least in the U.S., had the WORST EPS experience ever - the 2011-14 Hyundai Sonata. It, and the 2011-14 Elantra, were Korea's first foray into electric steering, and it was, to put it best, a DISASTER. The cars would steer themselves! Some customers successfully had dealers plug into the cars' OBD, access the steering menus, and select a 'harder' steeering mode(less assist boost) which helped matter somewhat, unless, like my Sonata trim level, they had...
(2)Wider, lower profile tires. This is the other primary reason for vague/light steering feel, even if more road feel. Wider tires in general react quicker to driver steering inputs, and sometimes also react to road imperfections(tugging, tramlining).
Unfortunately, wide tires with 'wagon-wheel' rims are now the fad, so the only ways to overcome light steering are A, less steering assist, or B, higher directional angles (SAI and/or Caster).
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On 17/6/19 9:57 pm, snipped-for-privacy@gmail.com wrote:

My first Toyota had EPS and it was as vague as hell. It also had a tendency to wander. My current Toyota is way better. Someone at Toyota has learnt a lesson.

Wider tyres actually have less road feel. That is because of the reduced effects of *pneumatic trail*. Wider tyres, while they have higher grip, reach their adhesion limits much more suddenly. Skinny tyres with a longitudinal contact patch are much more forgiving and give the alert driver plenty of advance warning of exceeding the limits of the slip angle.

--

Xeno


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Xeno wrote: " Wider tyres actually have less road feel. That is because of the reduced effects of *pneumatic trail*. Wider tyres, while they have higher grip, reach their adhesion limits much more suddenly. Skinny tyres with a longitudinal contact patch are much more forgiving and give the alert driver plenty of advance warning of exceeding the limits of the slip angle. "
So basically I knew it all along: Wide low profile tires serve no practical - read: consumer! - value off the race track. Except for aesthetics - show as much wheel/rim and as little sidewall as possible. <facepalm>
As for your earlier Toyota experience with EPS, it echoes the same experience I had with my 2005 Chevy Malibu(Epsilon chassis). The steering in that thing had next to no weight off center, and no connection to the road. Even with relatively 'higher' profile 65-series 15 tires.
Again, the common denominator behind vague/numb steering complaints with electric power steering is just too damn much BOOST. Pound per pound, given the same vehicle, an EPS motor will provide more steering assist than conventional (hydraulic) PS.
My current car thankfully has three EPS modes, including sport, which turns down the amount of assist the motor gives the driver. Normal is, normal, and 'Comfort' makes it easy enough to blow on the steering wheel to turn it. :D
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On 18/6/19 8:14 am, snipped-for-privacy@gmail.com wrote:

At a given tyre pressure and vehicle mass, the wide and narrow tyres will have the same contact patch area. So no gain there. What does happen is that the contact patch becomes wider. A wide contact patch provides adequate cornering force at smaller slip angles but they reduce self aligning torque because of the reduced pneumatic trail. Therefore natural stbility and steering feel is commensurately reduced. There is a practical width of tyre for every vehicle but *cosmetic appearance* trumps this so people want the look of wider low profile tyres. There is also a section profile that is optimum for both ride comfort and handling allowing the tyre to form part of the *springing*. IIRC, this was about 70. at a section of 65, the ride gets more harsh and continues to do so the lower the section profile gets.

With much less power robbed from the engine. Hydraulic systems always have a parasitic drag since you're always pumping fluid - even though there is no pressure being applied.
I don't think it is just boost alone though. I recall early 70s brake boosters with their sudden boost making low speed and parking movements difficult. In that scenario, in vehicles of the 80s and 90s, the reaction disc in the booster was modified to give more progressive brake feel. At full brake application the full booster force was applied but at low force brake applications it was much more moderated. Steering has the same principle applied in that the more force you apply to the steering, the more assistance is provided - a dynamic system. Also, they provide more assistance at low speed, less assistance at higher speeds now as well. The algorithms used are getting quite tricky. ;-)

--

Xeno


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Xeno wrote: " At a given tyre pressure and vehicle mass, the wide and narrow tyres will have the same contact patch area. So no gain there. What does happen is that the contact patch becomes wider. A wide contact patch provides adequate cornering force at smaller slip angles but they reduce self aligning torque because of the reduced pneumatic trail. Therefore natural stbility and steering feel is commensurately reduced. There is a practical width of tyre for every vehicle but *cosmetic appearance* trumps this so people want the look of wider low profile tyres. There is also a section profile that is optimum for both ride comfort and handling allowing the tyre to form part of the *springing*. IIRC, this was about 70. at a section of 65, the ride gets more harsh and continues to do so the lower the section profile gets. "
Agreed, and makes perfect sense!
I'd say the lowest profile I'd go for is 65-series.
Even if the contact patch for, say, a 70 and a 40 series tire is approx. the same area, that patch should be parallel, not perpendicular, to direction of travel. That should be common sense, and flies in the face of all the aftermarket modders who want to throw 40-series bling 20" rims on a '85 Caprice or some such that was specifically engineered to work with 70-75- series tires and a specific rim diameter(typically 15 or 16") and width.
By the way, the Sonata I drove that 'steered itself' exacerbated matters due to its 55-series tires on 17" rims - a Limited. Thing had a reasonable steering heft, yet somehow felt like driving on ICE, even on a dry highway on a sunny day. The steering wheel would slowly start tuggin to one side, and I'd start applying counter forcd, and then the steering wheel would snap quickly too far thr other way, causing the wander. It was a 'sticky' feeling, sort of.
I wish I'd kept the car, and just had gone to the dealer to minus-size down to 60 or 65series tires on 16 or 15" rims. Combined with the reduced-assist Sport mode, the 'ghost' in the EPS would have been even less of an issue.
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On Monday, June 17, 2019 at 10:15:38 PM UTC-5, snipped-for-privacy@gmail.com wrote:

How about self balancing tires? innovativebalancing.com
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snipped-for-privacy@gmail.com wrote in

I have used them, they are ok, but with everything the draw back is the inside of the tire has to be dry and clean, and you will get a starting bounce in the morning at start up. It is better than not ballancing truck tires at all. KB
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On 17/6/19 6:41 am, Arlen G. Holder wrote:

Not really. You are only driving in the one direction so the feathering will only be in one direction. If it were in both directions, it wouldn't be feathering, it would be *scalloping*, a diagnosis for a different cause.

You could experiment with it. After all, caster is not the only driver of steering returnability but you need to be very judicious in doing so noting that steering will be less precise, possibly more vague. Regardless, any caster reduction will be only part of the story since the primary cause, SAI, is well out of your control as it is a designed in feature.

I was going to suggest you run wide arcs around the bends but it seems that's not even possible.

It's what the tread is doing at the contact patch that is the critical issue here and that is damn difficult to visualise. Start with the forces acting on a tyre contact patch and you will see what I mean;
http://racingcardynamics.com/racing-tires-lateral-force/
In particular, this diagram;
http://racingcardynamics.com/wp-content/uploads/2014/10/Figure3.jpg
In your case, that contact patch centre of pressure will be off to the outside and not even. See the curved path? No small wonder that tread block deformation occurs.
Once I started to understand the forces creating slip angles, then I began to get the bigger picture on tyre wear and, more importantly, handling. https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcQKH0LYwk36kSkAbeliaY0KXsTCwozgQQBfvgC77M7U1oj7bpK3ow
Again note the curved path through the contact patch while cornering. That is the start point to understanding the concept as that is a result of the combination of forces acting at that pint..

I am presented with that same fait acompli with my car. My case is not as bad as yours as I get ~60,000 kilometres per set of tyres anyway, even with camber scrub issues.

You aren't Robinson Crusoe in that respect. It has taken me years to come to the level of understanding of steering I now have. I have a greater understanding of steering and handling now than had when I was teaching the topic at a technical college. I have found traditional texts on the topic aren't sufficient to give one the depth of understanding required - seek instead engineering texts on the topic and those devoted to motor racing. Those who work at the extremes of handling seem to have a better idea of what's happening at that contact patch.

I probably did. There is a whole section there on what actually happens when that tread passes through the contact patch. I cannot find a suitable diagram that provides, in and of itself, a decent explanation save for those on slip angle forces linked above because, as you have noted, it is difficult to picture in your mind what is going on.

I know what you mean. It has taken me a long time and a lot of reading about steering geometry before I had enough of an understanding how it all works.

A lot of cars have *money* wasted on them following that process. Far better to understand system operation and then experiment around the causes of the problem in order to effect a better *compromise* that mitigates your issue. As has been noted, you will not likely be able to cure your issue since it is a result of steering geometry compromise favouring highway operation but you now have a more precise start point.

You might want to discuss with him your issue and why you want to change the spec. Get him onside.

--

Xeno


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