18 inch wheels

[Speedy Emira]

I’m interested to know if anyone has bought a set of 18 inch wheels and maybe the 305 width tyres like the GT4s have. I understand on standard suspension it’s probably not going to be perfect due to the suspension effect of higher profile tyres.
The other thing I’d be interested to know if if the combination of tyre and rim is lower than on the 20 inch set for the same brands and models.

 

[lynchy73]

I’m interested to know if anyone has bought a set of 18 inch wheels and maybe the 305 width tyres like the GT4s have. I understand on standard suspension it’s probably not going to be perfect due to the suspension effect of higher profile tyres.
The other thing I’d be interested to know if if the combination of tyre and rim is lower than on the 20 inch set for the same brands and models.

Haven’t bought them, but there is a tuning shop in China that offers 18s for the Emira and they work with OEM brakes. 9” wide on the front, 11 on the back with 265 and 305.

 

[Nova]

I thought 18's wouldn't work as they won't clear the parking brake actuator.

 

[seriously]

Curious. What is the benefit here if you’re going to maintain the overall wheel height?

Less weight? Cheaper tires? Different suspension setup using higher profile tires?

 

[Rcktmn]

Curious. What is the benefit here if you’re going to maintain the overall wheel height?

Less weight? Cheaper tires? Different suspension setup using higher profile tires?

Smaller wheels and more tire sidewall will give you a more cushy ride. Also less likely to damage wheels on potholes and stuff. And tires are cheaper usually

 

[lynchy73]

I thought 18's wouldn't work as they won't clear the parking brake actuator.

This tuner shop says their 18s work with OEM brakes. They are custom designed to clear everything. They are wider too, 9” front and 11” rear. They run 265 and 305 tyres.

 

[Nova]

Curious. What is the benefit here if you’re going to maintain the overall wheel height?

Less weight? Cheaper tires? Different suspension setup using higher profile tires?

Others who are more knowledgeable about this can chime in, but tires with some healthy amount of side wall is better for performance driving on a race track. The flex of the tire allows it to bite the road better and absorb shocks and transitions that would cause a shorter/stiffer tire to break traction.

Take a look at the rear tire of a top fuel dragster - all that sidewall twists during acceleration to help the tire maintain traction.

 

[kitkat]

This tuner shop says their 18s work with OEM brakes. They are custom designed to clear everything. They are wider too, 9” front and 11” rear. They run 265 and 305 tyres.

Have they checked the parking brake? I checked the other day and i’m not sure many 18” wheels will work. The GT4 car probably works because I’m guessing it doesn’t have an electric parking brake.

 

[virtualmacho]

I thought 18's wouldn't work as they won't clear the parking brake actuator.

And here I am, imagining something like this until it dawns on me...

 

[Speedy Emira]

Others who are more knowledgeable about this can chime in, but tires with some healthy amount of side wall is better for performance driving on a race track. The flex of the tire allows it to bite the road better and absorb shocks and transitions that would cause a shorter/stiffer tire to break traction.

Take a look at the rear tire of a top fuel dragster - all that sidewall twists during acceleration to help the tire maintain traction.

This is what I was led to believe and for cars with a lot of power it would increase acceleration. I guess it’s like a lesser effect that a drag car tyre gives.

This thread was a bit of test to see if anyone has done it and I’d be interested to see if it improves performance in any way. There must be something in this or the GT4 would surely have 20s wouldn’t it?
I have spoken with a tuner yesterday and they said on standard suspension it is likely to corner worse and you would need coil overs to compensate on the overall stiffness.

I’d still be interested to know the wheel and tyre combination weight difference which could help like lighter wheels or CCBs.

 

[virtualmacho]

There must be something in this or the GT4 would surely have 20s wouldn’t it?

Watching the GT4 races, I would think that running over those mean looking curbs (?) are also a reason for more side wall.

 

[Speedy Emira]

Have they checked the parking brake? I checked the other day and i’m not sure many 18” wheels will work. The GT4 car probably works because I’m guessing it doesn’t have an electric parking brake.

I wonder what it has then Kitkat because they they must have something for when parked.

 

[lynchy73]

Have they checked the parking brake? I checked the other day and i’m not sure many 18” wheels will work. The GT4 car probably works because I’m guessing it doesn’t have an electric parking brake.

i will check specifically regards the parking brake. Agreed, that parking brake assembly is the highest point and there isn’t that much clearance. These pics do show the 18s fitted on what appears the standard brakes

 

[Tomwa]

18s do indeed have more sidewall, there are of course additional "flex" conditions which occur with a taller sidewall, but not all tire-sidewalls are created equal.

For a real 'race tire' it should have a stiff sidewall, you dont want the tire flopping over when you turn the wheel, you don't want the kind of squirm you'd see on a dragster, and they really only achieve those big sidewall wrinkles because of the low tire pressures they run.

For the Emira GT4, I wouldn't say that they run 18s for any 'special' reason that its entirely better from a physics or performance point of view. It could be a GT4 Class limitation on spec tires, it could be for the same reason there are people interested here, that 18's is just a more common size to find performance tires.

I know cars heavier than the Emira run 18s, like GT Classed Nissan GT-Rs. Not sure if everyone is just managing brake temps with better ducting, if the heavier cars are just resigning themselves to having poorer brake performance, HP is also limited in these classes so they dont see as high top speeds to brake from? They throw out rotors after every race because they've absolutely roasted them?

Not sure what the right combination of answers is here. But it does seem they have the stock rear e-brake tucked in under the 18. Honestly, it looks good. (Just looking at the wheel/tire package, not the biggest fan of the wheel design itself) It makes me highly tempted to find a Carbon Ceramic that could work under an 18inch wheel.

 

[Speedy Emira]

i will check specifically regards the parking brake. Agreed, that parking brake assembly is the highest point and there isn’t that much clearance. These pics do show the 18s fitted on what appears the standard brakes

I guess if you get them to fit the tyre choice would be limited.

 

[Tomwa]

I guess if you get them to fit the tyre choice would be limited.

For 18s?

Not that there is any apparent lack for 20 inch tires for road cars. But 18 is a whole different level of options.

Falken RT615K - 18's max size
Falken 660 - 19's max size
Bridgestone RE-71RS - Only 1 Size 285/30/20
Hankook Ventus R-S4 - 19 Max diameter
Toyo Proxies R1R - Max Size 18
Kumho Ecsta V730 - Max Size 19
BF Goodrich Rival S 1.5 - Max Size 19

There are some, like Advan who make some 20 sizes and of course Michelin Sport Cup 2s.

 

[Porter]

I wonder what it has then Kitkat because they they must have something for when parked.

Literally wheel chocks. Race cars typically don't have parking brakes.

 

[Speedy Emira]

Literally wheel chocks. Race cars typically don't have parking brakes.

I don't think that would pass an MOT over here.