Effects of wheel size and dimensions and stuff......

[TRDmod]

ok, i have st205, u all know that:)

i have 17inch 8 inch wheel, speedline ...

my main purpose is circuit, i dont care bout the looks,

i want to get extremely lightweight wheels, mostlikely 16 inch the original diameter that the car came with

now, quesitons

firstly, what is the WIDEST wheel i can put in a 205, also, i wanna know effects in terms of width versus thin, also, the effects and difference of the smalle rdiameter.........

i want to basically know what ppl have found by going back to the 16 inch, im told that it gives more grip on the circuit than the 17 inches...and according to some articles , i do agree.b ut never tried it, so wanna know if i should buy the new wheels......

i wanna know the widest tyres and wheels i can put, it will be 16 inch i will be buying ..... i wann a know difference in effects from my current wheel size to the 16 inch

thanks

[fangsport]

excuse me for sounding ignorant, but why do you want the widest tyre?

surely the tyre with the most grip would suffice?

[JT]

i have 17inch 8 inch wheel, speedline ...

my main purpose is circuit

Which circuit and what racing?

Have you weighed your current wheels with and without a tire? No point getting lightweight wheels if you don't even know how heavy your current ones are.

i want to get extremely lightweight wheels, mostlikely 16 inch the original diameter that the car came with

now, quesitons

firstly, what is the WIDEST wheel i can put in a 205, also, i wanna know effects in terms of width versus thin, also, the effects and difference of the smalle rdiameter.........

You can find out what width wheel and tires will fit by having a look under the guards. Get out a tape measure and a calculator. Check the clearances from lock to lock. Also depends on how much suspension travel and the current height of the car.

i want to basically know what ppl have found by going back to the 16 inch, im told that it gives more grip on the circuit than the 17 inches...and according to some articles , i do agree.b ut never tried it, so wanna know if i should buy the new wheels......

i wanna know the widest tyres and wheels i can put, it will be 16 inch i will be buying ..... i wann a know difference in effects from my current wheel size to the 16 inch

thanks

Have a read here: http://www.eng-tips.com/viewthread.cfm?qid=56923&page=1

[Caveman]

The width of your tyre doesn't have an effect on grip levels as the equation of friction doesn't involve surface area, only the coefficient of friction and the weight of the car. If you want to grip better the only thing you can do is get a stickier tyre.

A wider tyre however will wear slower but will take longer to warm up on the track.

[Perky]

The width of your tyre doesn't have an effect on grip levels as the equation of friction doesn't involve surface area, only the coefficient of friction and the weight of the car.

Aha! Or so you would think.

This is true as far as it goes, but the equation to which you refer is not a general description of the behaviour of two surfaces in contact but only of one aspect of that relationship. For a constrained set of materials and conditions -- namely hard (that is: inelastic) surfaces -- it is quite easy to model behaviour using the coefficient of friction. Though even in these cases we have to deal with two coefficients (static and kinetic). For elastic surfaces, like rubber tyres, the relationship is a lot more complicated and frictional coefficients are not so easy to understand.

The main issue, I take it, involves the deformation of the rubber by the road surface. This contributes to friction by dissipating energy and so increasing the force required to move the surfaces relative to one another. But, as a result of the shape of the road surface there is an upper limit to the amount of deformation possible. Once the variations in the road surface have been filled by the rubber, they can produce no more deformation even if the force on the rubber is increased (by making the car heavier). However, if the contact area is increased there can be more deformation and so more friction, even if the physical qualities of the rubber remain the same (same compound).

There are other factors that further complicate the physics of the tyre-road interface -- such as transitions between static and kinetic friction, the changing properties of rubber with varying temperature and the molecular physics of 'stickiness' -- which I won't pretend to understand. The point is that a simple model of static friction will not allow us to explain how tyres work and, for a number of complicated reasons, you can sometimes increase grip by fitting wider tyres.

This has the potential to become a controversial thread with a lot of anecdotes thrown around. It would be good if contributors could support their claims with physical explanations.

[Caveman]

Perky it seems you understanding to physics is superiour to mine, i'll give you that

I do understand you arguement and it is true but hampered by these effects.

a) They take longer to warm
b) They are harder to clear water from
c) Decrease the aerodynaics of the car

I would just fit a good set of 215's. These tyres are plenty thick enough and esp in 4WD where you'll just have understeer anyway.

[Stealer Of Souls]

Here's something I heard. I can't prove it personally, but there was an article or two on Autospeed.com.au about it...
Wider tyres will provide better lateral grip (sideways, ie during turns), but reduced longitudinal grip (front to rear, ie accel/deccel). Vice Versa for narrower tyres.

Also check what width rims you are getting, this will limit width of tyres to some degree.

I think you asked something about diameters too. Small diameter would result in lower top end, but should provide a bit faster acceleration (due to reduced rotational inertia requirements). Vice versa for bigger diameter...


I guess your best bet is to just try some rims and tyres. Then you can see what you like best, and what you feels suits your driving style best.
Personally I'd aim for the narrowest practical size tyre possible, to maximise longitudinal grip (if that's true), and then try to get the stiffest sidewalls and softest compound you can.

Also, this'll all depend a bit on your suspension setup. No point putting on race rubber if the suspensions just gonna give up.

[Kiddy]

The widest tyres you can have on the 7" is 235, but it would look like a bleeming off roader. 215 would be the best option. Give you a little bit of curb protection and a bit more rubber to hold it down.

[THA SHZ]

The widest tyres you can have on the 7" is 235, but it would look like a bleeming off roader. 215 would be the best option. Give you a little bit of curb protection and a bit more rubber to hold it down.

please enlighten me how a 235 goes on a 7 inch wide rim ! If u do this eventually once u get it on , and it will be a mission , then it is going to flower out the sides causing worse handling as the tyre isnt doin wot its designed to do . The widest u should go on a 7 inch wide is a 215 , but wot rim width are ur 16 's tht u are lookin at gettin ?

[Stealer Of Souls]

please enlighten me how a 235 goes on a 7 inch wide rim ! If u do this eventually once u get it on , and it will be a mission , then it is going to flower out the sides causing worse handling as the tyre isnt doin wot its designed to do . The widest u should go on a 7 inch wide is a 215 , but wot rim width are ur 16 's tht u are lookin at gettin ?

He never said it would be a good idea! lol.

Yeah. I agree. The best practical size would be 215. Anything larger and you'll start to lose turn in response (although the ride will be luxurious!) and linearity in handling during cornering.

[TRDmod]

what do you mean TURN IN RESPONSE

would difference would 225 and 215 have in terms of grip, responce and handling performance?

i mean if 17 inch rims isnt too bad then iw ont change but should i get 235s/40/17 or stick to 225/45/17 or go to 215s?

[TRDmod]

reading that website doesnt help, everyone jsut has opinions, i mean doesnt answer my questions, alot of jargon that is not quite easy to understand, so ifanyone understands them, mind my ignorance and please translate in laymans...

basically, :-

should i stick with 225 45 17, or 235 40 17, or 215 width tyre?? why, and what effects should it have

predominantly, my track would be PUKEKOHE, as i am a beginner and do not have time to trqavel to taupo and etc......

or should i opt for 16 inch rims, standard to the car? any suggestionsl, i mean what effects in terms of handling, which would give me more control on the track where the tyre faces maximum lateral and longitudinal forces....i mean top speed above 200 only lasts seconds on pukekohe which is alreayd a fast track, but then again, i dont want my car to be unstable at that speed cos well, pretty obvious id ont wanna die! but then agian, someone said that 215 is most practical, Y? is it most practical.....turn in response?
whats that

[Stealer Of Souls]

Sorry...

Turn in.
Have you ever driven an old VL commodore. They're an amazing car. When going in a straight line you can literally wiggle the steering wheel through something like 30 degrees back and forth and the body of the car will only wobble a little, but generally continue going straight.
Compare that to a car like my AE85.5 Levin. With it's harder springs, and stiffer sway bars. You can only wiggle the steering wheel a tiny amount before the car starts to wiggle.

Turn in response is firstly about how quickly the car responds to steering input. In the VL you'll turn the wheel and the car will "delay" for a bit before it actually starts to turn. On the flip side, turning the wheel in my Levin makes the car almost immediately start turning.


In the case of wider tyres, the 235 on a 7in rim will be 'balloning' out at the side wall, think puffing your cheeks out, and this will mean that the tyre will flex a lot in the sidewall. The will result in a reduced turn in response (tyre must finish flexing before you will feel the turn occuring).
On the other hand the 215's sidewalls will be more vertical and will have less flex in them, and therefore give a better feel during turn in.
--> This is for a SET rim width. If you used a wider rim you can have a wider tyre.
The other issue with over wide tyres (especially), but relates to all tyres is what they do in the middle of the corner. An over-wide tyre might lose grip more suddenly as the sidewall flexes over a bump. But I'm not sure how obvious this would be.


In terms of grip (assuming identical brand/design/type of tyre eg bridgestone grid II but either 215/225/235, and the correct rim size for each) the overall grip is the same. You will notice that you can corner harder on the wider tyre, but your braking performance will suffer, as will a full power launch. But since you won't be on the edge of braking performance it won't really matter, and since you won't be launching at full noise that won't be an issue either.

Personally, if you've got some okay tyres on the car right now, try them first. Don't go nuts, but give them a good going over. Get used to how the car handles now and then change the tyres. You've got 8in rims at the moment, so over time try all the widths you mentioned, 215/225/235.
Then you can try 16s.

Also. Are you going to street drive your car as well. This will dictate whether you need a second set of rims. The best option is a second set (find out what you like and buy a set to match) with some serious semi-race tyres on them.
Toyo RA-1
Yokohama A032R
Dunlop (damn can't remember name)


I'm afraid I can't be of much more help...

[vvega]

The width of your tyre doesn't have an effect on grip levels as the equation of friction doesn't involve surface area, only the coefficient of friction and the weight of the car.

Aha! Or so you would think.

This is true as far as it goes, but the equation to which you refer is not a general description of the behaviour of two surfaces in contact but only of one aspect of that relationship. For a constrained set of materials and conditions -- namely hard (that is: inelastic) surfaces -- it is quite easy to model behaviour using the coefficient of friction. Though even in these cases we have to deal with two coefficients (static and kinetic). For elastic surfaces, like rubber tyres, the relationship is a lot more complicated and frictional coefficients are not so easy to understand.



The main issue, I take it, involves the deformation of the rubber by the road surface. This contributes to friction by dissipating energy and so increasing the force required to move the surfaces relative to one another. But, as a result of the shape of the road surface there is an upper limit to the amount of deformation possible. Once the variations in the road surface have been filled by the rubber, they can produce no more deformation even if the force on the rubber is increased (by making the car heavier). However, if the contact area is increased there can be more deformation and so more friction, even if the physical qualities of the rubber remain the same (same compound).

There are other factors that further complicate the physics of the tyre-road interface -- such as transitions between static and kinetic friction, the changing properties of rubber with varying temperature and the molecular physics of 'stickiness' -- which I won't pretend to understand. The point is that a simple model of static friction will not allow us to explain how tyres work and, for a number of complicated reasons, you can sometimes increase grip by fitting wider tyres.

This has the potential to become a controversial thread with a lot of anecdotes thrown around. It would be good if contributors could support their claims with physical explanations.

great argument
when it comes to tyre grip real world trial and error is best
prolem been that there such a dynamic equasion with so many varibles its sometimed eazier to go with a proven package...
if your serious about doing this you need to do it as a procees
change one aspect at a time and measure the differance.... this way you will see what macthes not only your car but your driving style as well
i hope this helps

v

[TRDWGN]

There is a set of factory 16in ST205 mags (the 3spoke style with centre cap) at JPC in Takanini AK for around $250 for a set of 4, in great condition too from memory

[TRDmod]

ok, this is beginning to give me a good idea on what to do....how bout to giv eyou guys more capability of helping i tel you what happens now

i go to puke....pukekohe sorry, not puke, .....anyways

i feel first of all that the 'turn in response' is really good, very instant, in fact its exceptional, i feel that its better than driving on the standard 16s the car came with cos i drove one thats factory and it feels very different....

on the track, its also good, very good response.....i got told that my rims are 8 inch accordin to tyre shops, lots of them said that its 8 inch so i take it that its 8 inch.....

on the track, what i find, enterin the front straight in pukekohe, that i can be accelerating more during the turn, as its a long stroking turn but, i can feel my tyre giving way due to the lateral sideways force and must regulate my 'foot on accelerator action' otherwise i will lose it.....also the first bend before the first s bend, i find that i am gong way to slow for that too and my tyres are definately being out driven by anything....my brakes are only out driven and fade on the straight after a few laps, everywhere else does not seem to have a huge impact on the brakes....im upgrading my brakes soon so thats not in issues...

by the sounds of it, i wont have the problem of having rims too small for my tyre cos my rim is ok for 235 as it is 8 inch.......

any other feedback?
cos i like the turn in response to be prompt and quick, like a formula one steering, u know, a little turn is alot, i like that response...but i am also concerened wit grip....

thanks for more feedback.....

[Stealer Of Souls]

It's not surprising that the 17s give you a better turn in response. The sidewalls on a 17in tyre will generally be stiffer than a 16in tyre.

Take care when evaluating turn in, power steering can give a false sense of action some times. (but not normally).

You may find on the corner before the straight that a narrower tyre may allow you to put more power down, and with a bit of an adjustment to the entry you can probably carry a similar amount of speed into the corner. This should give a faster exit... In theory... Only way to know is to try it.

I think that most people will agree you're going about this right. Keep up with the 17s you've got until they are wearing a bit and then try something else. You might find that switching manufacturers will give you a good result to. Ask at the tyre shops what they would recommend for your application. Hopefully someone at your local will be a weekend racer and will give really good advice.

[TRDmod]

i went to a place in howick

the guy seems to know alot bout this stuff, he races personally...a civic and evo 7
well, he told me, that these are the points of having diff sizes.

17inch i currently have:
acceleration will be comprimised cos its bigger, more weight and inertia.
high spe3eds very smooth, but cornering lets say puke S BEND, i will find it easy to lose grip somewhere along the line there cos the tyre has such low pro that the rubber cant flex enough to grip...

16 inch:

lighter, and a lil more flex which means that better grip all along the turns. better accel cos its lighter.

he suggested that 16 inch and good tyres is the key to what i want
he quoted me 1000 each for 16 by 8 inch, he said i would get maximum grip with that size without comprimising the accel too mcuh as it is already so light the wheels, and good braking due to the wider tyres.

the brand is volk racing, one piece forged. F#ck its light!

[Stealer Of Souls]

That sounds like a good idea. I agree with what he says comparing to what I know (except for wider tyres better for braking - but he's the one with the race experience so I'd bow to him).
What sort of Volks are they? And what sort of rubber? $1000 sounds like quite a good price for some of the "top-of-the-line" rims. But I've got no experience with that range of stuff (I've only shopped for run of the mill stuff).