GS450 - Tyre sizes - Eh?

[Steven Lockey]

Ok, never knowingly had the options of different radius tyres on a car before and I need to replace all four tyres, so 
once again I come looking for wisdom!

So according to the web, these sizes fit my gs450h:

• 235/45 R17
• 245/40 R18
• 235/45 R19
• 245/35 R19
• 245/35 R20

So, I know what he numbers mean, what I don't know is what affect that will have. 

As for the radius, I assume a small radius would give better acceleration but worse fuel economy particularly at high speed.
Are there any other factors?

I assume all 4 should be the same side for standard road use?

Any specific tyre suggestions would also be appreciated. Found a few that look good for around £75 each but not sure if its worth
paying a bit more for better ones or if there are cheaper ones that are just as good.

Thanks in advance!

[Odysseus]

Not sure if I’ve understood your post correctly, but if your question is what tyres you buy, my answer would be the ones that fit your wheels!

On my GS450H with standard wheels the only option in your list that would fit is the 18 inch 245/40 R18.

Unless you have wheels of different sizes with the correct offsets and bolt patterns for a GS coming out of your ears, just buy tyres to fit your existing wheels.


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[Upex]

Agreed.

If you're not changing wheels, just the tyres, the radius R number must match and the width needs to be within that which the rim width can take.

I've not tried it on my GS, but I suspect that going to a smaller R number would add more cushioning for a smoother ride, but youll have more body roll and rock, I suspect likely noticeable more so on a heavy car as she is especially dropping to a 17.

You can vary the 18 size a little, perhaps to a 240/45/18, which is 3.1% larger in circumference so pushing limits of change without impacting speedo etc (3% max is recommended) but that would give you a thinner larger wheel, so more economy at speed, but little less rubber in road and more side wall for a softer ride. Depends on what you're going for i guess.

Re cheap or expensive, there are some great cheap tyres on market and some real ditchfinders. Heard lots on here about landsail and I've used marshal's on 4 cars and they been great. Have used top end Contis and others to, and to be fair, didnt notice much difference other than to my wallet 😬

I buy tyres on wet grip and noise rating now, pick the best value I can find where I need them for those ratings. Pay an extra £10 for a better wet/noise, yes, pay twice the price for a 1bd reduction, no thanks.

Good hunting 😉

[royoftherovers]

5 hours ago, Steven Lockey said:

Ok, never knowingly had the options of different radius tyres on a car before and I need to replace all four tyres, so 
once again I come looking for wisdom!

So according to the web, these sizes fit my gs450h:

• 235/45 R17
• 245/40 R18
• 235/45 R19
• 245/35 R19
• 245/35 R20

So, I know what he numbers mean, what I don't know is what affect that will have. 

As for the radius, I assume a small radius would give better acceleration but worse fuel economy particularly at high speed.
Are there any other factors?

I assume all 4 should be the same side for standard road use?

Any specific tyre suggestions would also be appreciated. Found a few that look good for around £75 each but not sure if its worth
paying a bit more for better ones or if there are cheaper ones that are just as good.

Thanks in advance!

Hi Steve,

1. Check your Handbook not the web.

2. if your GS450H is 2007, I would avoid large rims (19/20) and low profile (35/40/45) as they tend to give a hard and uncomfortable ride and can lead to kerbing the wheel rims.

3. My tyres are Kumho All Seasons at approx £85 each and on 225/50/17R tyres giving a smooth,quiet and comfortable ride. 

Do let us all know what you decide.

[Mihanicos]

The original tyres fitted on my car are 245/40/R18.

If 17 inch diameter is indeed an option, I would recommend it.  Larger diameters indicate a lower profile which in turn means a higher speed rating of the tyres and that means shorter wear.

Avoid Y, W, Z speeds, they wear out in no time.  

Opt out for V speed  ( 140 mph ), you get much higher mileage out of them. I use Hankook all season, V speed, absolutely silent, smooth as silk with exceptional grip in any weather.

Chris.

 

[johnatg]

The R letter has nothing to do with the tyre size - it represents 'radial' which refers to the tyre construction. (All car tyres are radial these days but once upon a time you also got cross-plies and the R was introduced into the size code to distinguish radials)

The final number in size is the wheel diameter - the tyre inner diameter. (not radius)

You only have options on tyre diameter if you have different sets of wheels - if, as is likely, your wheels are 18" you need 18" tyres unless you are prepared to splash out on new wheels.

Buy the same size tyres as fitted now.

I agree with the points raised by Chris in the post above - but be careful. Lexus specify tyres of a particular speed rating - usually W or Y. You don't need those ratings for use in the UK at least, but if you change from Lexus spec (eg to V) you should check with your insurance company - they probably won't mind but it is a 'modification' - so check. Actually it can be hard to find V rated tyres in the sizes mentioned - at least the larger ones.

[Steven Lockey]

Thanks all, had a fresh set of Bridgestone All-Season Weather Control A005 fitted at 245/40R18 as I did a lot of reading about tyres and they basically did really well on everything but snow and I'm in the south of england so no worries!

Car feels much nicer when taking sharp bends now. Back end isn't slipping out at all unless I force it, even then the TCS kicks in and tells me I'm been naughty! 🙂

Between that and the mufflers actually been attached to the exhaust , feels like a different car again! I was pretty happy before but as I sort out the various minor
issues with this car, I like it more and more. 

Set me back £550 but worth it imho. Also they are rated for been really long lasting which is another good thing.

Now lets just hope the full service/MOT doesn't find anything major!

[royoftherovers]

5 minutes ago, Steven Lockey said:

Thanks all, had a fresh set of Bridgestone All-Season Weather Control A005 fitted at 245/40R18 as I did a lot of reading about tyres and they basically did really well on everything but snow and I'm in the south of england so no worries!

Car feels much nicer when taking sharp bends now. Back end isn't slipping out at all unless I force it, even then the TCS kicks in and tells me I'm been naughty! 🙂

Between that and the mufflers actually been attached to the exhaust , feels like a different car again! I was pretty happy before but as I sort out the various minor
issues with this car, I like it more and more. 

Set me back £550 but worth it imho. Also they are rated for been really long lasting which is another good thing.

Now lets just hope the full service/MOT doesn't find anything major!

I`d be interested in knowing what mileage you do in fact obtain from those 40 profile tyres Steve.

[Werewolf1976]

On 7/28/2020 at 1:27 AM, Steven Lockey said:

Ok, never knowingly had the options of different radius tyres on a car before and I need to replace all four tyres, so 
once again I come looking for wisdom!

So according to the web, these sizes fit my gs450h:

• 235/45 R17
• 245/40 R18
• 235/45 R19
• 245/35 R19
• 245/35 R20

So, I know what he numbers mean, what I don't know is what affect that will have. 

As for the radius, I assume a small radius would give better acceleration but worse fuel economy particularly at high speed.
Are there any other factors?

I assume all 4 should be the same side for standard road use?

Any specific tyre suggestions would also be appreciated. Found a few that look good for around £75 each but not sure if its worth
paying a bit more for better ones or if there are cheaper ones that are just as good.

Thanks in advance!

Try this - it let's you visualise the difference in a tyre

https://tiresize.com/comparison/

Certain size seem 'specific' to OEM specs and unfortunately seems to cost more

You can vary size a bit but you will effectively gain or lose sidewall. 

Try 225/50 17 vs 235/45 17 if you want an example of what I'm taking about

 

[Steven Lockey]

Thanks that helps visualise it nicely.