N!ck-z Posted October 5, 2010 Share Posted October 5, 2010 A friend of mine asked me for a recommendation on a tyre for his car and so I recommended the ultrac sessantas which he then went and bought. Today he asked me to have a look at his car as he thought the tyres were fitted incorrectly. We compared them to my car but they were both the same - and I have to admit it looked wrong but I had never noticed. They are fitted like this: I have had a search about on the web and it seems this issue has come up quite a lot in the past on other forums with the final answer (from Vredestein) confirming they are fitted correctly. My question is how is this correct??!! Obviously the engineers and designers know what they are doing, and the tyre performs excellently (I will be buying them again) but I just cant see how they work. To me (and many others it seems) it looks like both tyres would channel water in the same direction with the tyre on the right as shown above, channelling the water into the middle of the car and the tyre on the left channelling the water away from the car - thus surely producing a force in one direction? Has anybody got any thoughts theories or facts regarding this? (Just to be clear - I am not questioning the design - I am questioning simply how it works) Quote Link to comment Share on other sites More sharing options...
Zugara Posted October 5, 2010 Share Posted October 5, 2010 There should be a "rotation" or "direction" arrow on the tyre wall, have a look for it on the outside, if you canr see it then they are possibly fitted the wrong way. Quote Link to comment Share on other sites More sharing options...
marcuscollings Posted October 5, 2010 Share Posted October 5, 2010 Mate mine are the same! And I looked for the arrows and they were right so I just let it go but your right it does look funny Quote Link to comment Share on other sites More sharing options...
N!ck-z Posted October 5, 2010 Author Share Posted October 5, 2010 They are defo fitted the right way, and that is as in the pic above, I just like to know how things work and it is bugging me that this tread pattern doesnt make sense. Quote Link to comment Share on other sites More sharing options...
Zugara Posted October 5, 2010 Share Posted October 5, 2010 Looks like the water is directed to the outside, looking at that tread pattern, although it does look kinda strange. Quote Link to comment Share on other sites More sharing options...
ChrisS Posted October 5, 2010 Share Posted October 5, 2010 It seems this conversation goes on in lots of places.Here is an example. http://www.pistonheads.com/GASSING/topi ... ded?&mid=0 Quote Link to comment Share on other sites More sharing options...
rtbiscuit Posted October 5, 2010 Share Posted October 5, 2010 never really questioned it, i knew the sidewalls were right, but it did bug me that the pattern run the same way on both sides. my therotical guess and also partly based form having them on in the snow is that if they ran the same direction on both sides you might end up with a kind of archemidies screw effect and the car might slightly crab sideways across the road. the reason i suggest this is that in the snow i found when pulling away the car felt like it was moving slightly diagonally across as you pull away. the tyres bite nicely into the snow but with the deep tread it felt like it pulled the car diagonally like an archamedies screw. this maybe why they alternate the pattern to reduce this sensation in normal driving conditions. this is theory though, not based on fact. Quote Link to comment Share on other sites More sharing options...
chippychip123 Posted October 5, 2010 Share Posted October 5, 2010 They look very similar to the Yokohama parada spec 2 patteren and there not normally rotational but they do have inside and outside writen on the tyre Walls. Don't ask me how this works though Quote Link to comment Share on other sites More sharing options...
N!ck-z Posted October 5, 2010 Author Share Posted October 5, 2010 rtbiscuit - I'm a bit confused with your post - what you are explaining is exactly what I would expect in the wet. If you look at the tyre and think about which part of each groove hits the tarmac first then they are channelling the water in the same direction resulting in a diagonal force on the car. It seems many forums have discussed it and no one has found out how it works. It frustrates the hell out of me! Quote Link to comment Share on other sites More sharing options...
marcuscollings Posted October 5, 2010 Share Posted October 5, 2010 Sorry to seal this tread.... But reading the piston heads review, what should I be pumping them up to I think mine are at 35psi is this right? Quote Link to comment Share on other sites More sharing options...
rtbiscuit Posted October 5, 2010 Share Posted October 5, 2010 rtbiscuit - I'm a bit confused with your post - what you are explaining is exactly what I would expect in the wet. If you look at the tyre and think about which part of each groove hits the tarmac first then they are channelling the water in the same direction resulting in a diagonal force on the car. It seems many forums have discussed it and no one has found out how it works. It frustrates the hell out of me! ok that would explain why i felt that movement, maybe the directional movement is a happy medium. if the tyres ran in the same direction owuld they then try and pull in opposite directions and there fore make the handling odd. at least if they track diagonally the steering input would be the same regardless Quote Link to comment Share on other sites More sharing options...
N!ck-z Posted October 5, 2010 Author Share Posted October 5, 2010 my head is now hurting. That would mean that other symmetrical tread patterns would result in unstable handling , which surely cant be right.... can it??! Ive got to say though, that in the snow I have felt that drift to one side too, but in all honesty I didnt think about it until now. Ignorance is bliss I suppose. I cant remember the exact pressure but 35 psi rings a bell to me. Its on the inside of your door shut. Quote Link to comment Share on other sites More sharing options...
Husky Posted October 5, 2010 Share Posted October 5, 2010 until i get my alignment sorted i cant say for sure, but i have the biggest ones they make and mine crabs ever so slightly on harsh deceleration or acceleration. but like i say, my alignment is probably well shot by now. so ignore me Quote Link to comment Share on other sites More sharing options...
ATTAK Z Posted October 5, 2010 Share Posted October 5, 2010 For me that non directional tread pattern is just wrong .......... surely simple physics dictates that asymmetrical tread patterns should be made in left and right hand versions to balance lateral forces and to ensure that and water is directed to the outside (or inside) of the car on both sides .............. I suppose it's a cost cutting measure (twice the stock required for RHS and LHS versions) You can't swap wheels on the same axle with directional tyres such as the Falkens but it looks like you can with the Vredesteins ............ I suppose that could be classed as an advantage for the Vreds but still strange in my book Quote Link to comment Share on other sites More sharing options...
was8v Posted October 5, 2010 Share Posted October 5, 2010 As an engineer I'd say the the direction the water is pushed in will make not one jot of difference to the direction of the car! The water will move, not the car! The channels just provide a space for the water to go, meaning the rubber can contact the tarmac. The grooves are just to prevent aquaplaning - bald tyres mean a thin skim of water exists between tyre and tarmac = no grip. With grooves the weight of the car pushes the water into the grooves and rubber can contact tarmac. Fancy tread patterns really have very little effect on grip! In fact the particular tread pattern may be more related to reducing tyre noise and fashion than increasing grip. Under acceleration / braking longitudinal grooves will put more rubber in contact with the road. When turning then latitudinal grooves will provide more grip. Diagonal I suppose will be a compromise. Quote Link to comment Share on other sites More sharing options...
rtbiscuit Posted October 5, 2010 Share Posted October 5, 2010 tyre design is not my area of expertese. they know what they are doing, i go on the reviews and professional feedbacvk on tyres to base my decisions on. admittedly on my new car and the new wheels i haven't put the sessantas on i fancied a change and have given the falken 452's a go, and so far i'm quiet impressed. Quote Link to comment Share on other sites More sharing options...
N!ck-z Posted October 5, 2010 Author Share Posted October 5, 2010 As an engineer I'd say the the direction the water is pushed in will make not one jot of difference to the direction of the car! The water will move, not the car! The channels just provide a space for the water to go, meaning the rubber can contact the tarmac. The grooves are just to prevent aquaplaning - bald tyres mean a thin skim of water exists between tyre and tarmac = no grip. With grooves the weight of the car pushes the water into the grooves and rubber can contact tarmac. Fancy tread patterns really have very little effect on grip! In fact the tread pattern may be more related to reducing tyre noise and fashion than increasing grip. http://www.tyres-online.co.uk/techinfo/patterns.asp The tread on a modern car tyre is considered to be a water pump, designed to express water from between the contact patch and the road surface........................................A recent trend has been the development of high performance tyres with circumferential grooves and tread bands that offer different characteristics across the tread of a tyre - these tend to be asymmetric and directional. Another trend is for the "single tread" where the tread pattern is such that the "land" area of the tyre never breaks contact with the road and the "sea" area (the troughs) channel water away from under the tyre. Both these tyre patterns are claimed to be quieter than block type tread patterns. I would disagree about only the water moving. for sake of argument replace the water with a higher viscosity liquid and replace the tarmac with ice - the car would then move. Newtons 3rd law - every action has an equal and opposite reaction. Obviously this is an extreme to illustrate a point but I think water and tarmac at speed would affect a car. I agree with the rest though. rtbiscuit - I 100% agree, I leave it to the experts and go by the reviews, it is just my naturally inquisitive nature and engineering background that makes me want to know how everything works! Its a curse! Quote Link to comment Share on other sites More sharing options...
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