Wheel Sizes

[spoon]

Whats the advantages/disadvantages of changing wheel sizes (diameter/width)?

is there an ideal number for setting your car up?

ie larger diameter rims give lower profile tyres = less sidewall flex

lower diameter rims means less combined unsprung weight (with tyre)

larger width = can run softer compound tyres to increase milage etc...


just working out best track wheel size/tyre combo for my ke70 (obviously all the other factors are important too ie offset and weight differences between rims)

thanks peoples

[oldcorollas]

for track or road?

for road you are limited in the change in dimension you can run.

rims is kind of easy.. larger diameter rim = less sidewall flex (depending on tyre), less suspension effect from tyres, more overall weight, more inertia, more unsprung weight, and ability to run larger brakes.

tyre width vs grip is quite complex, although there are fancy equations to describe it.
combination of mechanical and chemical grip.
need to consider contact patch shape (width vs diameter of tyre), weight on tyre vs width (contact patch shape, comformtiy of rubber to road suface etc) etc etc.

basically it depends what surface you are usign it on.
a rough surface with little rubber on it needs more mechanical grip
a smooth surface that has been "rubbered in" can use more chemical grip

and final factor (maybe) is water removal capablity, and resistance to tyre leavign the road surface due to standing water (to do with weight vs width and pattern)

400mm wide sticky tyre on an F1 spec track might give great chemical grip, but the contact patch shape may cause instability etc etc

[eeeyan]

If you know the tyre you want to run for a specific application its sometimes easier to choose a wheel from that.

IE: For a rolla something like a 15" with a good tyre is going to be fine for most stuff depending on the application. But if your going extreme then you gotta weight it up.

[KENut]

My tip is dont increase the front track too much, or at least keep the rear track width close.

KE70's arent a long car, and increasing front track can make it quite twitchy.

Also you will want light wheels, you can easily notice the difference between heavy and light wheels on an underpowered KE!

[eeeyan]

We dont know the rest of the story yet tho KENut he might have a worked K motor or be calling it a KE70 and have a 300hp 4AGTE or he could have a breathles 30yo K motor with half a million kays. He might be going for hill climb, street, khana, track we need mroe details really.

Just FYI spoon s13 front parts will give a wider front track without going spastically twitchy depends how good you are at the limit in the handling dept. Practice makes perfect bro.

[oldcorollas]

My tip is dont increase the front track too much, or at least keep the rear track width close.

KE70's arent a long car, and increasing front track can make it quite twitchy.

Also you will want light wheels, you can easily notice the difference between heavy and light wheels on an underpowered KE!

increasing front track by offset alone will help to make any car twitchy, but increasing track via suspension components may make it more stable.

[spoon]

Car in question is a mildly modified blacktop 20v, semi s13 front setup ( custom struts, r31 skyline lcas(give similar track to xt130 arms) and kmac camber tops, 6kg springs, agx adjustable shocks, rear is t18 diff st141 discs, fe2 shocks, falcon springs, adjustable panhard, whiteline sway bar.

More interested in real world advantages of wheels-obviously the lighter the combination of wheels the better but has to have the traction when needed. Car is primarily set for circuit.

Thanks for replys so far

[spoon]

More to the point, if for example I have 2 different sets of wheels say 13" diameter and 16" diameter respectively with identical width and rolling diameter with tyres installed, which would make the better choice (money no object)?

Is there a point where the centripetal mass becomes too much to negate the use of a different size wheel? Ie spinning an equivalent weight wheel will have a different effect depending on the position of the weight on the wheel. Is the overall weight much different between the hypothetical wheels+tyres combo?

Sorry, makes sense in my head lol!