Technical Dynamic tyres

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Technical Dynamic tyres

AB100

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Not ready for tyres yet on the new silver machine, but I wanted to canvass opinion anyway.


The Dynamic has 165/65R14 on 5x14 alloys. In theory I could go to a maximum wider section of 185 and perhaps drop the profile to 60.


1. Yes, I know about the economy and noise


2. I like mechanical grip and to leave wet junctions without wheelspin


Has anyone changed to a different size with any recommendation?
 
I'd just buy better tyres. Although I'm only on 13s, I changed to Michelin Energy tyres and it improved the handling so much in comparison with the Continentals. They're also much better wearing and better for fuel economy. So for me win all round!
 
Hmmm..........economical to me sounds like 'hard' rubber I always think. Not even looked what tyres are on it from new, but the junction wheel-spin irritated me.


I am happy for tyres to last 6000-8000 miles providing they stick like you know what. For me, grip is everything - economy, noise, costs are minor.


Very happy with the Uniroyals on what we laughingly call the "big car" in our house (the 100HP).
 
As we're on to wheels, I've got the chance of a set of 195/65 15's winter tyres on Stilo wheels with 43 offset.

Is there anyone adventurous there who've used this size on a Panda169 Multijet?
My crude measurements suggest that they'll fit without fouling, but if anyone else has tried it, it would be helpful. Thanks.
 
205/55 16's are way too big. They will have an effect on the speedoreadings and probably throw a tantrum in the ABS.

Also for better grip in snow you should use the narrowest advised width.



gr J


Agreed. I am considering 195/65 15's though. Still wondering if they would foul, but rough measurements suggest they'd be OK.
 
:bang: Not 205/55 16's... They are the alloysize for Stilo's.
However... The same applies to 195/65/15's. Same circumference.

gr J


I think his question is more about tyre clearance on lock. The 195/65 will have the same rolling circumference as his existing tyres but the wider tyre/wheel plus a 43mm offset could have an impact.


Would need to check the offset of the existing wheels. ET43 is more deeply dished than the 6.5x15 wheels on the 100hp which are ET30. Thus, the wheels sit closer to the suspension.
 
Also for better grip in snow you should use the narrowest advised width.



gr J


Yep - my original question concerned clearance.
But I can't really understand the comment here. I always thought that greater contact area gave better performance in snow.
Economy=Narrow.
Grip=Wide.

Be interested in others takes on this.
 
Yep - my original question concerned clearance.
But I can't really understand the comment here. I always thought that greater contact area gave better performance in snow.
Economy=Narrow.
Grip=Wide.

Be interested in others takes on this.


Never been sure of the maths myself but think the theory is based on contact pressure (weight per unit area) with a splash of myth - an old postcard of a 2cv digging into the snow whilst a fat-tyred shod exec-mobile lies floundered and spinning wheels. That's probably relevant to summer tyres though I'm not sure about winter tyres.


For my 100Hp I stuck with 195/50R15 snow tires.


Someone will come along an enlighten us soon.......


I do think you need to test the offset/steering lock clearance though. You might end up with a usable turning circle worse than the 100HP.
 
Yep - my original question concerned clearance.
But I can't really understand the comment here. I always thought that greater contact area gave better performance in snow.
Economy=Narrow.
Grip=Wide.

Be interested in others takes on this.

If you're talking deep snow or mud then narrow is better - it bites down through it better.

Assuming you're not off-roading or going out in deep snow then wider is likely to give better grip in most conditions.

There's a healthy debate on which is better in light snow - seems to be split 50/50! All I can say is a mk1/2 Panda on 135 tyres will run rings round most fat low profile shod euroblob's when it's snowy (with 4wd they will go anywhere!). (y)
 
We need physics. I'll make something up to create a massive argument:


Car weight = M
Tyre width = W
Tyre contact length = L


The contact pressure =
M
WxL


The grip is basically friction, whose resistive force is proportionate to the contact pressure. However, the friction is limited by the adhesive capabilities of the ice/snow. This is the unknown quantity.


Therefore, before embarking on any snowy journey, you need to know if it's the "wrong kind of snow".


QED.
 
:yeahthat: presure per square cm.

I have a 16" Stilo (previous car was a Stilo MW) alloy and I'm pretty sure it'll rub on the suspension. You'd need a lower ET or spacers, but then they'd probably rub on the outside.

gr J
 
The camel knows how to do it! Different material, but similar problem.

When a Canadian tracker can't go further in the snow with his boots, he puts on snowshoes.
Skis were originally invented to help hill farmers in winter, when their normal boots sank in the snow.
I would expect that light weight and wide contact area is the ideal formula, but quite happy to be shot down
 
I would expect that light weight and wide contact area is the ideal formula, but quite happy to be shot down


That's the logical thing - but you have to take into account the 'sweet spot', That is to say there is a point where the snow/ice has a perfect coefficient of 'grip'. Before and after that value the grip is lessened.


Assuming the same tyre and wheel circumference, two cars can yield the exact same pressure per contact patch:


CAR A
Weight = 700
Tyre width = 135


CAR B
Weight = 2000
Tyre width = 380
 
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Enter the nerdy engineer... :D

The contact area for a certain load is the same for any width of tyre, if the tyre pressure is the same.

Maybe tough to accept, but think about it:
It is quite OK to assume that a tyre is fully flexible, and then the area of contact is simply the load carried by the wheel divided with type pressure.

30 PSI will carry (surprise) 30 pounds per square inch. 600 pounds will thereby need 20 square inch contact area. If the thread is 5 inch wide, the lenght of the footprint will be 4 inch.
4" x 5" x 30 PSI = 600 pound.

If the tyre is increased to 10" wide, the lenght of the footprint will be reduced to 2"
 
Enter the nerdy engineer... :D

The contact area for a certain load is the same for any width of tyre, if the tyre pressure is the same.

Maybe tough to accept, but think about it:
It is quite OK to assume that a tyre is fully flexible, and then the area of contact is simply the load carried by the wheel divided with type pressure.

30 PSI will carry (surprise) 30 pounds per square inch. 600 pounds will thereby need 20 square inch contact area. If the thread is 5 inch wide, the lenght of the footprint will be 4 inch.
4" x 5" x 30 PSI = 600 pound.

If the tyre is increased to 10" wide, the lenght of the footprint will be reduced to 2"


We're not talking tyre pressures though right? We're talking pressure as weight distribution. That is pressure = force/area.


Thus, for the same rolling radius and same width tyres a 500kg car will exert less pressure than a 1000kg car (assuming the PSI in the 100kg car is higher to create the identical contact patch by offsetting the extra weight).
 
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And I always thought that the wider the tyre (with same diameter) the larger the contact area!
So the guy with snowshoes can cross snow where his boots wouldn't take him because, although he weighs the same, his contact area is larger.
Isn't that why it helps to lower tyre pressures when the going gets tough - to increase contact area with the ground?
 
And I always thought that the wider the tyre (with same diameter) the larger the contact area!
So the guy with snowshoes can cross snow where his boots wouldn't take him because, although he weighs the same, his contact area is larger.
Isn't that why it helps to lower tyre pressures when the going gets tough - to increase contact area with the ground?


Precisely. Cos you reducing contact pressure by distributing the weight over a greater area.


Same reason why when someone wearing a stiletto will hurt more when you're stamped on than wearing a sandal.


But your real issue is to question the clearance with those Stilo wheels...
 
Yep - so I checked the wheelfitment.eu site, which gave me tyre/wheel options for the Panda 169, and they range from bog standard 155/80 x 13 up to 195/60 x 16!
Possibly the 16" is for the 4x4, but they don't specify that.

Thanks for the various helps, guys. Think I'll chicken out and go for 15"s with winter rubber.
 
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