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Hi all,

 

I've recently purchased a set of staggered alloys, they are 8j for the fronts and 8.5j for the rears.

 

My guess was 225/45/18 and 245/45/18? But, I'm completely guessing here. Also, I will be lowering the car on Tanabe TNF112 springs, which is 33mm at the front and 23mm at the rear.

 

I'm starting to think it's more like 40 or 35 profile...

 

Any idea on what the factory tyre sizes I should be getting for them? I've done a lot of searching on here and also Club Lexus, but to no avail.

 

Thanks in advance.

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These wheels are for IS250/350 and the tyre size was 225/40/18 and 255/40/18. Now because you fitting them on GS which has more space in wheel arches, you may as well have 45s. Besides I would always favour 245/45/18 over 255/40/18 - GS300 simply does not have enough power to really justify 255 tyre. Now because you are lowering the car this may change a bit i.e. I am not sure how much space there will be after it so 40 or 35 may be a way to go. 

You can as well go wider at the front - 235 should fit all else being equal... or at least that would be the case before lowering. Why wider at the front and narrower at the rear... that is because at least on IS250 car gets very unnatural balance and tends to understeer despite being RWD car, having square set-up would be more natural for the handling, but because you have staggered alloys that isn't really possible. So the next best thing in my opinion would be bringing tyre width closer together towards square set-up -  235/245. This should give nice neutral balance and maximise grip.  

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Hi,

At least in my GS450h from 2008, the standard tire size is 245/40 R 18 W (other allowed: 235/40R18, 225/45R18)

Rim: 8Jx18 ET45, 5x114.3, center hole 60.1mm

Check the clearance to brake calibers, especially in front... not all aftermarket rims will fit...

BR.Sami

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6 minutes ago, Sami Tilander said:

Hi,

At least in my GS450h from 2008, the standard tire size is 245/40 R 18 W (other allowed: 235/40R18, 225/45R18)

Rim: 8Jx18 ET45, 5x114.3, center hole 60.1mm

Check the clearance to brake calibers, especially in front... not all aftermarket rims will fit...

BR.Sami

G-Spider / Baransu are OEM Lexus wheels and fitment is identical of most Lexus models (GS/IS/RC/ES), I think only different fitments used are on newer LS/LC and on CT.

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26 minutes ago, Sami Tilander said:

Hi,

At least in my GS450h from 2008, the standard tire size is 245/40 R 18 W (other allowed: 235/40R18, 225/45R18)

Rim: 8Jx18 ET45, 5x114.3, center hole 60.1mm

Check the clearance to brake calibers, especially in front... not all aftermarket rims will fit...

BR.Sami

Those are non staggered wheels I'm afraid.

 

Mine are as follows:

 

Rears - 18 x 8.5j and ET50

Fronts - 18 x 8j and ET45

 

In the past, I've had BMW's with 225 front and 255 rear when they are staggered. But I've no idea what these should be. Perhaps I'll need to ring Lexus who can advise based on part number or model.

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1 hour ago, Linas.P said:

These wheels are for IS250/350 and the tyre size was 225/40/18 and 255/40/18. Now because you fitting them on GS which has more space in wheel arches, you may as well have 45s. Besides I would always favour 245/45/18 over 255/40/18 - GS300 simply does not have enough power to really justify 255 tyre. Now because you are lowering the car this may change a bit i.e. I am not sure how much space there will be after it so 40 or 35 may be a way to go. 

You can as well go wider at the front - 235 should fit all else being equal... or at least that would be the case before lowering. Why wider at the front and narrower at the rear... that is because at least on IS250 car gets very unnatural balance and tends to understeer despite being RWD car, having square set-up would be more natural for the handling, but because you have staggered alloys that isn't really possible. So the next best thing in my opinion would be bringing tyre width closer together towards square set-up -  235/245. This should give nice neutral balance and maximise grip.  

Very informative, thanks. I would rather have the 45 profile, purely from a comfort and durability perspective too.

 

In regards to the fronts, I'll look into the price difference between the 225 and 235 as well as the rolling radius calculator against the stock wheels.

 

Perhaps I need to lower first to ascertain the arch gap?

 

I will also check the calculator of the rolling radius, as I don't want the speedo to have too much error.

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10 minutes ago, JDM-Fiend said:

Very informative, thanks. I would rather have the 45 profile, purely from a comfort and durability perspective too.

 

In regards to the fronts, I'll look into the price difference between the 225 and 235 as well as the rolling radius calculator against the stock wheels.

 

Perhaps I need to lower first to ascertain the arch gap?

 

I will also check the calculator of the rolling radius, as I don't want the speedo to have too much error.

Indeed - lowering first and then measuring what you can fit would be wise.

My understanding is that speedo works of driving wheels, as such size of front tyres does not matter. Difference between 245/45/18 and 255/40/18 is small (-2.6%). From my experience on IS250 speedometer shows almost exactly 10% more, so presumably similar in GS (in most cars it is 5-10%). Even if it is less (say 5% over) you would have some margin left to spare and if anything speedometer will be closer to actual speed. 

image.thumb.png.608d0a11bb6ec8e48c77e7430b18c788.png

Other benefit of 245 over 255 is as well lower fuel consumption, obviously marginal difference, but positive nonetheless. And they wear more evenly with 225. Whereas if you have 225/255, the rears may still have 40% of thread left by the time you need to change fronts, putting yourself in tricky situation - should you replace tyres which are still good to keep all the same, or should you replace fronts and leave part worn tyres on the rear, inducing more oversteer than desirable. 

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3 hours ago, Linas.P said:

Indeed - lowering first and then measuring what you can fit would be wise.

My understanding is that speedo works of driving wheels, as such size of front tyres does not matter. Difference between 245/45/18 and 255/40/18 is small (-2.6%). From my experience on IS250 speedometer shows almost exactly 10% more, so presumably similar in GS (in most cars it is 5-10%). Even if it is less (say 5% over) you would have some margin left to spare and if anything speedometer will be closer to actual speed. 

image.thumb.png.608d0a11bb6ec8e48c77e7430b18c788.png

Other benefit of 245 over 255 is as well lower fuel consumption, obviously marginal difference, but positive nonetheless. And they wear more evenly with 225. Whereas if you have 225/255, the rears may still have 40% of thread left by the time you need to change fronts, putting yourself in tricky situation - should you replace tyres which are still good to keep all the same, or should you replace fronts and leave part worn tyres on the rear, inducing more oversteer than desirable. 

That makes sense about the driving wheels and the speed.

I'm considering the following:

Fronts:

image.thumb.png.f2365f202e5c398db9ba517debeab3db.png

image.thumb.png.5da8dde71542260b2d66fe6b93cb6c2c.png

Rears:

image.thumb.png.f74fec6b3187ca3d079414a535633b7d.png
image.thumb.png.709d5b65f0bd8c6afe68fa7aefb30ed5.png

 

They seem to be fairly close to stock overall and will allow me to lower the minimal amount I've decided on, with very little hassle.

Thanks again!

 

 

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