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Re: Back on 225/45/16s with a huge improvement
[Re: ]
#1125854
04/11/2010 14:07
04/11/2010 14:07
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Marko_hr
Unregistered
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Marko_hr
Unregistered
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Oh thank God!! Finally my chance to excel. I do hope I don't blow it!
The grip is lateral resistance to slip: How much lateral force you can exert on the tyre before it skids. The grip is roughly calculated as the total downward force multiplied by the coefficient of static friction (whatever), so the area of surface contact doesn't directly come into the calculation.
In other words, with a larger contact area, the force exerted per unit area is reduced, so the grip per unit area is also reduced proportionately. The total remains the same.
I'm not an expert on the subject, but the basic physics principes You mentioned are true, just there's something missing - the rubber (as any other material) has it limits, so it doesn't matter if you distribute a given force over small or vast surface, as long as you don't exceed the limits of the material, and it starts to shear... In theory, a wider tyre should give better ultimate cornering grip, IF the car suspension is set up properly to keep the wheel perpendicular (or with minimum negative camber), limiting the contact patch deformation. In practice, many road cars have suspension geometry that gives positive camber under body roll (favoring "predictable" understeery handling), reducing the contact patch. One should test the two dimensions, (same manufacturer and model) back to back, on the same car, to make a final judgement.
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Re: Back on 225/45/16s with a huge improvement
[Re: Nigel]
#1125880
04/11/2010 14:34
04/11/2010 14:34
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Joined: Aug 2006
Posts: 1,845 Darlo / Leeds
Darlo_Nick
My life on the forum
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My life on the forum
Joined: Aug 2006
Posts: 1,845
Darlo / Leeds
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This topic has come up a few times now and each time it has made my brain hurt!!
So on our cars we would never realistically notice the different between 205 and 225 tyres.
But with more extreme examples;
F1 cars have wide tyres to produce a contact area that is wide and short, to increase cornering grip.
Drag cars have tall and relatively narrow tyres to produce a contact area that is narrow and long, to improve traction in a straight line.
Is that basically correct?
Instagram : Nick16vt
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Re: Back on 225/45/16s with a huge improvement
[Re: Joe78]
#1126039
04/11/2010 19:49
04/11/2010 19:49
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yosko
Unregistered
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yosko
Unregistered
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225's has abut 10% less traction,due to 10% wider tyre. the forces on car is equal only torque will be 1,2% more for 225 but its unsignificant.
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Re: Back on 225/45/16s with a huge improvement
[Re: Darlo_Nick]
#1126041
04/11/2010 20:04
04/11/2010 20:04
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Joined: Mar 2009
Posts: 3,091 Leicestershire
Joe78
OP
I need some sleep
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OP
I need some sleep
Joined: Mar 2009
Posts: 3,091
Leicestershire
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This topic has come up a few times now and each time it has made my brain hurt!!
So on our cars we would never realistically notice the different between 205 and 225 tyres.
But with more extreme examples;
F1 cars have wide tyres to produce a contact area that is wide and short, to increase cornering grip.
Drag cars have tall and relatively narrow tyres to produce a contact area that is narrow and long, to improve traction in a straight line.
Is that basically correct? This makes perfect sense to someone like me,thanks nick. None of this p=f/a malarkey. Thanks guys and sorry for opening a can of worms. I'm sure some of you enjoyed the chance to show off though
Last edited by Joe78; 05/11/2010 03:57.
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Re: Back on 225/45/16s with a huge improvement
[Re: ]
#1126056
04/11/2010 20:53
04/11/2010 20:53
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Joined: Dec 2005
Posts: 17,367 Staffordshire
Nigel
Forum veteran
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Forum veteran
Joined: Dec 2005
Posts: 17,367
Staffordshire
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225's has abut 10% less traction,due to 10% wider tyre. Nooooo a 225 tyre has a wider contact patch, but it is shorter, so there is almost exactly the same traction (there will be a slight difference, but it is nowhere near 10%)
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Re: Back on 225/45/16s with a huge improvement
[Re: Nigel]
#1126149
05/11/2010 01:50
05/11/2010 01:50
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Mollymoo
Unregistered
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Mollymoo
Unregistered
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In fact my maths and my english were off, I said radius when I should have said diameter, silly mistake which totally alters what I am saying.
Mathematically the difference is actually 23mm, not 22.5mm as I erroneously stated.
A 225/45/16 tyre has an overall diameter of 608.9mm - 406.4mm of wheel + 202.5mm of sidewall (225 x 0.45 x 2)
A 205/55/16 (I assume a typo in your post when stating 205/50/16) tyre has an overall diameter of 631.9mm - 406.4mm of wheel + 225.5mm of sidewall (205 x 0.55 x 2)
giving an overall difference of 23mm which will affect your speedo. A figure of 5mph misread for every 25mm in diameter is often bandied about, though I have never seen any proof to back that up.
Last edited by Mollymoo; 05/11/2010 01:51.
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Re: Back on 225/45/16s with a huge improvement
[Re: ]
#1126174
05/11/2010 07:40
05/11/2010 07:40
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Joined: Dec 2005
Posts: 17,367 Staffordshire
Nigel
Forum veteran
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Forum veteran
Joined: Dec 2005
Posts: 17,367
Staffordshire
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(I assume a typo in your post when stating 205/50/16) Not a typo - the correct tyre for the 20vt is 205/50 - a 55 profile is too high This is why your calculations are showing a bigger difference than mine
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Re: Back on 225/45/16s with a huge improvement
[Re: Nigel]
#1126200
05/11/2010 10:29
05/11/2010 10:29
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Ianchat
Unregistered
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Ianchat
Unregistered
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With these calculations you must also bare in mind that they will always be indicative only as the max in service dimension will be around 10mm greater than the nominal. So you get the idea that the difference between the two sizes could in practise be less than the differences you may see between two tyres of the same size, especially as the nominal width of a 205/50 is from memory 214mm. As previous posters have pointed out, this difference is unlikely to be perceptible across the whole system.
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Re: Back on 225/45/16s with a huge improvement
[Re: Nigel]
#1126233
05/11/2010 12:07
05/11/2010 12:07
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Mollymoo
Unregistered
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Mollymoo
Unregistered
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OP states a 55 profile tyre not a 50, hence all calculations based on his information
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Re: Back on 225/45/16s with a huge improvement
[Re: ]
#1126237
05/11/2010 12:26
05/11/2010 12:26
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Joined: Dec 2005
Posts: 17,367 Staffordshire
Nigel
Forum veteran
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Forum veteran
Joined: Dec 2005
Posts: 17,367
Staffordshire
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OP states a 55 profile tyre not a 50, hence all calculations based on his information Good point - hadn't spotted that. However, it means that the OP has been running on incorrect tyres, which gives another reason for the 225s feeling lots better - far less sidewall deflection
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Re: Back on 225/45/16s with a huge improvement
[Re: Nigel]
#1126246
05/11/2010 12:57
05/11/2010 12:57
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Mollymoo
Unregistered
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Mollymoo
Unregistered
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OP states a 55 profile tyre not a 50, hence all calculations based on his information Good point - hadn't spotted that. However, it means that the OP has been running on incorrect tyres, which gives another reason for the 225s feeling lots better - far less sidewall deflection Very, very true, whatever he has been doing he has had the wrong tyre on, so is almost guaranteed to see benefits to changing
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Re: Back on 225/45/16s with a huge improvement
[Re: ]
#1126258
05/11/2010 13:48
05/11/2010 13:48
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Marko_hr
Unregistered
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Marko_hr
Unregistered
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OP states a 55 profile tyre not a 50, hence all calculations based on his information Coupe 16vT with "Plus" trim came from the factory with 205/55 tyres on 16x6,5 rims. I've seen no other version use this dimension though "Plus" trim on 16v/16vT models is different to 20vT "Plus" - only leather seats, climate control and alloys IIRC
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Re: Back on 225/45/16s with a huge improvement
[Re: Joe78]
#1127003
07/11/2010 13:10
07/11/2010 13:10
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Joined: Feb 2006
Posts: 5,390 Essex
Trappy
Forum is my life
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Forum is my life
Joined: Feb 2006
Posts: 5,390
Essex
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Surely a wider tyre has a greater contact patch with the road, and therefore more grip? I'm probably wrong but you'd think that'd be the case. If it's not then would anyone explaining why? (somebodys chance to show off)
The contact patch of a tyre is totally (and exclusively) dependant on the pressure of air inside the tyre and the weight bearing down on it. The 20vT has around 900kgs on the front wheels (450kgs pr 990lbs each). We all know that the fronts should have 39psi. If you want to see what our contact patch is in inches, then you can't be far off in diving the weight by the psi right? 990/ 39= 25.38". Carrying on my admitedly simple calculatiing, lets look at 205 vs 225 tyres. 225 width= 8.86" 205 width= 8.07" Divide the 25.38" patch by the width and we have contact patches of 225= 8.86" x 2.86" 205= 8.07" x 3.15" Because the pressure and the weight are the same, the contact patch is the same, only the shape of the patch changes. The ONLY way you can change the area of the contact patch, is to changes the pressure or the weight on the tyre. Other differencesLower profiled, wider tyres will improve turn-in response at the expense of ride quality because of less give in the sidewall. Lower profiled, wider tyres lose some of the 'self righting' of a thinner tyre. Lower profiled, wider tyres reduce the feedback from the road, making it harder to feel the break-away point and on the limit balance. Lower profiled, wider tyres have better heat disperal properties. One last benefit of a thicker profile must be the ability to absorb bumps on poor road surfaces, keeping more tyre in contact with the ground. Of course it goes without saying that generally lower profiled, wider tyres come from better ranges offering better compounds that WILL affect grip.
F****** b****** thing...
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Re: Back on 225/45/16s with a huge improvement
[Re: Trappy]
#1127282
08/11/2010 01:00
08/11/2010 01:00
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Mollymoo
Unregistered
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Mollymoo
Unregistered
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Surely a wider tyre has a greater contact patch with the road, and therefore more grip? I'm probably wrong but you'd think that'd be the case. If it's not then would anyone explaining why? (somebodys chance to show off)
The contact patch of a tyre is totally (and exclusively) dependant on the pressure of air inside the tyre and the weight bearing down on it. The 20vT has around 900kgs on the front wheels (450kgs pr 990lbs each). We all know that the fronts should have 39psi. If you want to see what our contact patch is in inches, then you can't be far off in diving the weight by the psi right? 990/ 39= 25.38". Carrying on my admitedly simple calculatiing, lets look at 205 vs 225 tyres. 225 width= 8.86" 205 width= 8.07" Divide the 25.38" patch by the width and we have contact patches of 225= 8.86" x 2.86" 205= 8.07" x 3.15" Because the pressure and the weight are the same, the contact patch is the same, only the shape of the patch changes. The ONLY way you can change the area of the contact patch, is to changes the pressure or the weight on the tyre. Other differencesLower profiled, wider tyres will improve turn-in response at the expense of ride quality because of less give in the sidewall. Lower profiled, wider tyres lose some of the 'self righting' of a thinner tyre. Lower profiled, wider tyres reduce the feedback from the road, making it harder to feel the break-away point and on the limit balance. Lower profiled, wider tyres have better heat disperal properties. One last benefit of a thicker profile must be the ability to absorb bumps on poor road surfaces, keeping more tyre in contact with the ground. Of course it goes without saying that generally lower profiled, wider tyres come from better ranges offering better compounds that WILL affect grip. Great explanation and I certainly dont know anywhere near enough about this subject to comment on the scientific basis of what you are saying. I do however have a question. Your calculations lead us to the conclusion that a tyre that is 8" wide only has a contact area with the road that is only 3" front to back? Surely that isnt the case? A tyre certainly looks to be in contact with the road for more than 3" front to back
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Re: Back on 225/45/16s with a huge improvement
[Re: Joe78]
#1127374
08/11/2010 13:06
08/11/2010 13:06
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Orion
Unregistered
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Orion
Unregistered
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Also I used to ride motorcycles a lot and the more power the bike has, the fatter the tyres got. Must be a reason for it. If not grip, then what? Well, that's mainly for powering away and not cornering. Fatter motorcycle tires have a larger contact patch when not inclined. To the handling it is actually worse to have a fatter tire. The fatter the tire, the more you need to lean the bike to maintain a certain speed in a corner. More lean is less ground clearance, so the highest speed possible would be theoretically reduced by a fatter tire - although the difference between a 180 and a 190 wouldn't be too big. A 240 wide tire on the other hand is strictly for posers, a decent 190 or 200 tire can handle all the torque a motorcycle engine can produce - even turbocharged ones. Grip and traction, two totally different vectorial thingamajings many people seem to blend into the grip denominator.
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Re: Back on 225/45/16s with a huge improvement
[Re: ]
#1127422
08/11/2010 14:31
08/11/2010 14:31
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Joined: Nov 2007
Posts: 2,084 Pontypool
mr_tickle
Club member 1455
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Club member 1455
Competition Level
Joined: Nov 2007
Posts: 2,084
Pontypool
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Yous is all rong! wat you need is them phat tyres innint! everyone noes that phatter is better - it is just sience. My mates car goze like its on rails and hes has huge phat tirz!!
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Re: Back on 225/45/16s with a huge improvement
[Re: Kayjey]
#1128116
10/11/2010 09:03
10/11/2010 09:03
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Marko_hr
Unregistered
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Marko_hr
Unregistered
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Sorry, The 16vT Plus came with size 205/50 ZR 16.
The 16v Plus came with 205/55 ZR 15 A friend of mine bought 16vT from Italy (second hand), and it came with 205/55r16 on stock 4-spoke rims. I thought it was a bit large dimension, but then I've read on this site it was the correct dimension. As the song says, "...don't believe half of what you see and none of what you hear." so correct is 205/50r16, it makes sense!
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Re: Back on 225/45/16s with a huge improvement
[Re: ]
#1128159
10/11/2010 12:12
10/11/2010 12:12
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DaveM
Unregistered
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DaveM
Unregistered
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The dangers of copy+paste This has an interesting (and detailed) take on the tyre width / pressure / contact patch debate: http://performancesimulations.com/fact-or-fiction-tires-1.htmI think it concludes wider tyres have a slightly bigger contact patch but the relationship is far from linear.
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Re: Back on 225/45/16s with a huge improvement
[Re: Joe78]
#1207288
27/04/2011 11:08
27/04/2011 11:08
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The_Squirrel
Unregistered
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The_Squirrel
Unregistered
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Just to add another spice to the mix how would 225/40/16 work on a coupe ? For some reason on toyos these are £10 a tyre cheaper than 225/45/16s so wondering how these would handle and grip
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Re: Back on 225/45/16s with a huge improvement
[Re: MCMike]
#1207342
27/04/2011 13:33
27/04/2011 13:33
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Joined: Feb 2006
Posts: 395 Sweden
Rask
Making a profit
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Making a profit
Joined: Feb 2006
Posts: 395
Sweden
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Looking really nice! What color code did you use? What process (preperation work, type of spray metod ?)
Last edited by Rask; 27/04/2011 13:53.
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Re: Back on 225/45/16s with a huge improvement
[Re: ]
#1207351
27/04/2011 13:59
27/04/2011 13:59
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Joined: Feb 2006
Posts: 395 Sweden
Rask
Making a profit
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Making a profit
Joined: Feb 2006
Posts: 395
Sweden
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Just to add another spice to the mix how would 225/40/16 work on a coupe ? For some reason on toyos these are £10 a tyre cheaper than 225/45/16s so wondering how these would handle and grip More up to the tire brand rather than the tire size. Good brand, nice ride and handling. One of my old P-Zero tires were from 1998, the rest from 2002-2005, when I replaced them with Hankooks last year it made a tremendous difference to the noise, ride and handling. The one drawback is that the new tires are a bit "dirtier", wider tires results in more splashing on the body sides of the car.
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Re: Back on 225/45/16s with a huge improvement
[Re: Rask]
#1207535
27/04/2011 21:04
27/04/2011 21:04
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alx
Unregistered
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alx
Unregistered
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The one drawback is that the new tires are a bit "dirtier", wider tires results in more splashing on the body sides of the car.
I suggest LE-red mud flaps
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Re: Back on 225/45/16s with a huge improvement
[Re: Joe78]
#1207651
28/04/2011 00:27
28/04/2011 00:27
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Joined: Dec 2005
Posts: 3,694 Midlands
MCMike
Club member 2095
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Club member 2095
Forum is my job
Joined: Dec 2005
Posts: 3,694
Midlands
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Hi - I cleaned, filled, sanded & primed the wheels then used Ford Nimbus Grey topcoat with laquer on top to finish.
1972 Triumph Stag 1984 Alfasud TI 1999 Fiat Coupe Turbo LE 2005 350Z
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Re: Back on 225/45/16s with a huge improvement
[Re: Joe78]
#1207710
28/04/2011 08:15
28/04/2011 08:15
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shinyshoes
Unregistered
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shinyshoes
Unregistered
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Any issues with the paint bubbling on the fronts from brake heat? Had that on a set of 20VT rims i did for the 16
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