IS250 Tyres - square set-up?

[zoricib]

My 2 year old Avon ZV7 rear tyres have started cracking badly and want to change them. Price to change the like-for-like size (245/45/17) vs matching the size on fronts (225/25/17) is massively different. Over £300 for a pair of 245s vs £150-180 for a pair of 225s. Looking mainly at premium tyres (Goodyear, Michelin, Bridgestone) with a wet driving rating of A.

So what are your thoughts? Square setup or eat up the price difference and go for OEM spec?

 

Already been in touch with Avon for a replacement but the process is very convoluted and will need new tyres anyways so I will just let it go.

[Linas.P]

245s on IS250 is completely unnecessary. For 17" wheels I would definitely go with square set-up. This further gives you an option to rotate the tyres, so it is double saving - not only cheaper tyres, but you can as well wear them more evenly, as long as you always put the best tyres to the rear.

In terms of grip 245s are absolutely not required, 225s have plenty grip, especially if you go with decent brand tyres. As well IS250 AWD comes with identical wheels and square set-up, but I believe it is running 4x235s.

I personally went for 245s instead of 255s on 18", but that is because my wheels themselves were staggered, so I could not rotate them anyway. 17" are "square" wheels, so you can absolutely go with square set-up for tyres as well. Likewise if I had 18" set-up which is square say 4x8J instead of 2x8J+8.5J, I would go 225s even on 18s. 

Looks wise consider using spacers, 15-20mm, should do. 

[zoricib]

Thanks for the quick reply Linas! Would the spacers bring the skinnier tyres to the same level as now, or would they fill the arches a bit better than with the 245s? I was considering spacers for the rear with the current tyres too, so they fill the arches a bit better.

[Linas.P]

Assuming you going from 245 to 225, it is 20mm difference, but only 10mm on each side, so 20mm spacers would make them come out 10mm closer to the wheel arch.

It is kind of matter of taste and I would say ~15mm is required to "fill" the rear arches on IS250. So if you going with 225s in the rear, then 25mm spacers would be required. I would never recommend going more than 25mm, maybe 30mm at absolute maximum. And 20mm would be recommended if you want to be on the safe side. 

Obviously, all the safety things apply. Make sure the spacers are good quality, hub centric, correct diameter lips etc. 

[zoricib]

Great! thank you Linas

[T man 545645]

I have the bigger tyres on the back, never tried the square setup. I tried diff tyres, originally came with bridgestones which i felt were not great with fast acceleration in wet, then conti's which were a bit better, since then always used eagle f1's which have been excellent. 

[Mr Vlad]

I had 245's on the rear and 225's on the front. I just stuck with standard set up. Had Bridgestone Turansa tyres which were ace in wet weather But no tyre whatever will stop aquaplaning. Take Linas's advice.

[J Henderson]

6 hours ago, Linas.P said:

Assuming you going from 245 to 225, it is 20mm difference, but only 10mm on each side, so 20mm spacers would make them come out 10mm closer to the wheel arch.

?

20mm wheel spacers increase the track by 20mm each side (40mm overall), not 10mm.

As for the original question, I would personally stick with the 245s. Whether the car needs a tyre that wide might be questionable, but the increase in wheel arch gap and harsher ride quality with a 225 would drive me crazy.

[Linas.P]

40 minutes ago, J Henderson said:

?

20mm wheel spacers increase the track by 20mm each side (40mm overall), not 10mm.

As for the original question, I would personally stick with the 245s. Whether the car needs a tyre that wide might be questionable, but the increase in wheel arch gap and harsher ride quality with a 225 would drive me crazy.

And where did I say anything to contrary. OP asked about "arch filling", not about overall track... so it will fill arch by 10mm more... and yes it will make a track 40mm wider. 

Most of the bumps are taken by the front anyway, so I can't see how having wider or narrower rear would make much difference. As well, 245 in the rear really creates weird car balance... IS250 is RWD car which always wants to understeer... So if you in the dry, then it understeers and I hate it and in the wet you just get epic tank slapper every time, because it starts sliding, but then either rear hooks-up or front loses grip. With square set-up you would just get much more predictable handling - yes it will act like rear wheel drive car, so expect oversteer, but at least you don't need to deal with both understeer and over steer depending on the situation. In short - my problem is that with staggered set-up on IS250 you get unnatural balance to the car, and it not only matters if you want to slide it (which to be honest I don't care about), but it as well makes it harder to control the car when it does slide, because it is less predictable. 

So if argument is - 245 is a safety factor... then I don't believe it is. If you ever get to the point where you are limit of grip, then you will get very unpredictable understeer from this set-up. And if you don't drive to the limit, then 225 are plenty anyway. Same goes for braking - front does 80%+ of braking anyway. Same goes for aquaplaning - narrower tyres actually reduces aquaplaning. 

[J Henderson]

15 minutes ago, Linas.P said:

And where did I say anything to contrary.

When you stated that a 20mm spacer would somehow only have a 10mm effect. The tyre size is irrelevant.

A 20mm spacer will move the wheel outwards by....20mm!

[Linas.P]

11 minutes ago, J Henderson said:

When you stated that a 20mm spacer would somehow only have a 10mm effect. The tyre size is irrelevant.

A 20mm spacer will move the wheel outwards by....20mm!

What are we talking about here? If you go from 245 to 225 and then add 20mm spacer, then end result will be that tyre sidewall will be 10mm closer to the arch than before. Now sure - if you change NOTHING ELSE and just add 20mm spacer then it will simply SPACE OUT the wheel by 20mm. But we are talking about combination of changes, 20mm narrower tyre + 20mm spacer = outside wall of the tyre 10 mm further out.  What isn't clear here?

https://www.wheel-size.com/calc/?wheel1=245-45-17X8ET45&wheel2=225-45-17X8ET25&fcl=50mm&wcl=30mm&scl=50mm&sr=0mm

Note in the summary of the changes at the bottom:

"Fenders  The tire will stick out 10 mm farther. Rim will stick out 20 mm farther. Make sure that you have enough room under the fender. If not, consider narrower tires or higher offset"

The standard rim on IS250 is 8J = 203mm, so tyre sticking out is only thing that matters, because tyre will always stick out more than the rim. And even if you go from 245 to 225, the 225 is still wider than the rim.

[J Henderson]

46 minutes ago, Linas.P said:

What are we talking about here?

Well, I was talking in absolute terms about the effect of a certain size of wheel spacer. Nothing more.

But, if we also introduce the tyre into the equation, then that's a whole different can of worms as the tyres are a variable.

Not all tyres are equal. Yeah, a 225 is a 225, but is it really just 225mm wide? In theory it is, but I'm sure you'll find many are actually wider than that in actual physical width. So, I couldn't categorically state that "the tyre" will be x amount of mm closer to the wheel arch. That would depend on tyre type/brand.

As for 225 still being wider than the wheel. I find this disputable given that not all tyres are equal. Certainly, the tyres I have on the front of my own car look slightly stretched, if anything.

Yes, 8 inches might be 203mm, but wheel width is measured internally between the tyre mounting surfaces. The actual outside width on a 8J wheel will be closer to 9".

 

[Linas.P]

25 minutes ago, J Henderson said:

But, if we also introduce the tyre into the equation, then that's a whole different can of worms...

But that was specifically what we were discussing... 

As for the rest I think you are correct on all individual things in isolation. 

225mm means - only the thread surface i.e. the part that touches the road. And indeed the side wall design could be very different, some have wheel protectors, some don't, some are round, some are more like triangle, some are very thin and flimsy, some are reinforced etc. But the thread will always be 225mm and 225mm is more than 203mm, so that is all that matters here. And on top of that there is no way you will touch and actual wheel to the arch, unless you severely lower the car (like 80mm), but you will probably scrape the bottom of the car before you scrap the wheel on the arches. In short as far as spacers are concerned, wheels width isn't an issue most of the time. 

[Mr Vlad]

Correct me if I'm wrong but aren't the wheels on the back wider than those on the front? I'm sure I've read time and time again you can't put a rear wheel on the front.

[J Henderson]

Only with 18" wheels. On the models with 17s they're the same size front and back.

[LenT]

13 hours ago, zoricib said:

Looking mainly at premium tyres (Goodyear, Michelin, Bridgestone) with a wet driving rating of A.

I have the 18” staggered setup and I’m quite happy with the Lexus tyre sizes.  But like others here, I have fitted the Goodyear Eagle F1  Asymmetric tyres mainly because my priority is overall wet road performance.

I think they have certainly delivered in that respect.  In considering your actual tyre choice, I would certainly recommend looking at the latest Asymmetric 6 version.

https://www.tyrereviews.com/Tyre/Goodyear/Eagle-F1-Asymmetric-6.htm

[Linas.P]

16 hours ago, LenT said:

I have the 18” staggered setup and I’m quite happy with the Lexus tyre sizes.  But like others here, I have fitted the Goodyear Eagle F1  Asymmetric tyres mainly because my priority is overall wet road performance.

I think they have certainly delivered in that respect.  In considering your actual tyre choice, I would certainly recommend looking at the latest Asymmetric 6 version.

https://www.tyrereviews.com/Tyre/Goodyear/Eagle-F1-Asymmetric-6.htm

Yeah - wet grip is priority for me as well. 

[normski2]

16 hours ago, LenT said:

I have the 18” staggered setup and I’m quite happy with the Lexus tyre sizes.  But like others here, I have fitted the Goodyear Eagle F1  Asymmetric tyres mainly because my priority is overall wet road performance.

I think they have certainly delivered in that respect.  In considering your actual tyre choice, I would certainly recommend looking at the latest Asymmetric 6 version.

https://www.tyrereviews.com/Tyre/Goodyear/Eagle-F1-Asymmetric-6.htm

Me too +1 to that

[Spark plug]

putting 225 instead of 245s will lower the gearing because the rolling radius will be less which will make your speedo read high and use more fuel.

[Spark plug]

22 hours ago, Mr Vlad said:

Correct me if I'm wrong but aren't the wheels on the back wider than those on the front? I'm sure I've read time and time again you can't put a rear wheel on the front.

All the wheels are 8j's the 245 tires rub on the front suspension. 

[Spark plug]

I never let my tires wear down to the 1.6mm legal limit as they are more prone to aquaplaning. and never use cheep tires.

 

[LenT]

1 hour ago, Spark plug said:

putting 225 instead of 245s will lower the gearing because the rolling radius will be less which will make your speedo read high and use more fuel.

I think that rather depends on the second figure in the equation - the aspect ratio which determines the height.

My IS wears 225/40 on the front and 255/35 on the rear - both on 18” wheels.

The second figure is the height of the tyre expressed as a percentage of the full tyre width.

So the rear wider tyres have a lower percentage which results in the two tyres having exactly the same height.  This ensures that the rolling radius remains unchanged.

1 hour ago, Spark plug said:

I never let my tires wear down to the 1.6mm legal limit as they are more prone to aquaplaning. and never use cheep tires.

Totally agree.  3mm is my limit - and it’s a depth below which most tyre manufacturers claim performance deteriorates rapidly.  

Generally, cheap tyres are cheap for a reason.  However, some ‘budget’ tyres are cheaper for different reasons.  Namely, they are made by major tyre brands - often using the same compounds and benefitting from the same technology - but they are made in a limited number of the most popular sizes, thus reducing production costs.

They don’t aspire to being ‘performance’ tyres but are perfectly acceptable for most drivers.  If cost is a real consideration, they can be worth seeking out.

[Linas.P]

3 hours ago, Spark plug said:

putting 225 instead of 245s will lower the gearing because the rolling radius will be less which will make your speedo read high and use more fuel.

In general having narrower tyres will improve the fuel consumption, so most likely it will use less fuel. Yes the tyre will be 1.6% smaller, not massive difference but it the speedometer will indicate slightly more than actual speed, which it already does anyway.

[H3XME]

Just please use this calculator: https://www.willtheyfit.com/index.php?width=245&aspect=40&diameter=18&wheelwidth=8.5&offset=50&width2=225&aspect2=40&wheel_size=18&wheel_width=8.5&offset2=30

The link is already setup for 245/40R18 18x8.5 ET50 (factory rear sizes) & 225/40R18 18x8.5 ET30 (which is what you get with 20mm spacers)

"Compared to your existing wheel, this new wheel will have an inner rim which is 20mm further away from the suspension strut. The outer rim will poke out 20mm more than before."

Good 225s are more than enough for an IS250. Square setup is the way to go when you're not pushing 400hp. 

Don't forget the base model is250 with 16" wheels came with factory 205/55R16s all round..

And this is a controversial opinion, but people who put anything bigger than 245s on this car need to learn to how to drive this car because those bigger tyres won't keep you on the road any better. If 225s can't keep you on the road, it's driver error. Over-tyring is a common problem and it actually hurts the cars performance. 

[Linas.P]

19 minutes ago, H3XME said:

Don't forget the base model is250 with 16" wheels came with factory 205/55R16s all round..

That is actually good point - I find it hard to justify anything wider than 225s, considering base spec. came with 205s and it is not like it has less power, or weighted less... same 204hp, same weight.

I do understand people put larger wheels for the looks, but what is the point of wider tyres where it doesn't need to be wider?!. If you track the car and you have some sort of amazing grip set-up, sure wider tyre is better on dry surface. But wider tyre is actually worse on wet, worse on fuel, noise and it costs more. Again if the car has 400hp+ - then sure you need it for traction (not cornering, but straight line traction), but for 204hp 225s are plenty. I maybe see the point of 245s on IS350 that has 306hp and as it obviously shares design with IS250 I can understand why Lexus has wider rears by default - so it is not so much that IS250/IS220d needs it, but more because it was cheaper to set-up suspension geometry once and fit it across the range.