[Franciskano]

Hello, my i30 Tyres are 225/45 R17.

Can I replace it by a 225/50 R17?

Will I loose warranty, stability or anything else?

Thanks

[accim]

You won't lose your warranty (well maybe if the dealer was an idiot you would, but I doubt). The car might be slightly less stable (the tires are little bit higher, but I doubt you'll feel it) but where I live, you must have that size approved and registered in the papers otherwise cops might give you a "ticket" (AU$ 600-700) if they find out.

You might have problems with speedometer, because it will show you less speed than your actual one. Don't know how precise the speedometer is with R17 tires, but let's say it's absolutely accurate (it's impossible it is, but let's say that it is) - than when you are traveling at speed 60 mph, the speedometer will show some 58 mph.. So..you'll always have to pay attention to drive 2-3 mph "less" (according to your speedometer) if you don't want ticket for speeding  8)

If I were you, I would put 225/45 on, although, I think if you would put 225/50/17, the speedometer would be about 99% accurate (now it's showing 3-5mph more than it should)

Check this out http://www.miata.net/garage/tirecalc.html

[Blue]

i think that's a pretty good call Accim...

My two cents... and I am NOT a tyre boffin....

Given that the i30 comes standard with a 15 inch rim... I think extending the profile (50 vs 45) of a 17 inch rim would be pushing it...
I don't think there is enough difference for it to become dangerous, but you MAY experience tyre rub... MAY!

[Dazzler]

Sounds like you guys have it covered...

But Franciskano  might like to check this out...

http://www.miata.net/garage/tirecalc.html

[snowcherry]

i'm really sorry but i don't get it 

is the 17" (stocks) showing a faster reading on the speedo that the 15" stocks?
i tried googling but that didn't help matters

[accim]

I've tested the speed with 185/65/15 and at 100 kph (by speedometer), you are actually going I don't know exactly but around 95 kph..

Later, I've tested the same thing with 205/55/16 and when driving (according to your speedometer) 100 kph, you are actually driving 96,5 kph. Don't know how it is with 225/45/17, but it's probably around 98 (the actual speed you are driving).

The reason for that is the fact that tires and rims size 185/65/15 make more revs per mile than 205/55/16 and even more than 225/45/17 - because they are smaller (the 185/65 ones)

185/65/15 compared to 205 and 225.

Specification  Sidewall  Radius  Diameter  Circumference  Revs/Mile  Difference
185/65-15         4.7in  12.2in    24.5in         76.9in        824        0.0%
205/55-16         4.4in  12.4in    24.9in         78.2in        811        1.7%
225/45-17         4.0in  12.5in    25.0in         78.5in        808        2.1%

http://www.miata.net/garage/tirecalc.html

I think with 225/45/17 you get the most accurate info about your actual speed. Sometimes good, sometimes bad. If you have 185/65/15 your speedometer is showing you almost 5kph more than you are actually divining, so when the cops stop you, it's not as bad as you thought it will be 

[Blue]

i'm really sorry but i don't get it  

is the 17" (stocks) showing a faster reading on the speedo that the 15" stocks?
i tried googling but that didn't help matters

Not necessarily Snowcherry.  I will try to help you get it...

17 vs 15 isn't the issue. Circumference of the tyre is.  Increasing wheel diameter doesn't necessarily increase the circumference of the tyre.
Think of a doughnut.  If you take some dough out of the middle, making the hole bigger (essentially allowing it to fit a bigger wheel), the outside DOESN'T any get bigger.  In that case the speed will read the same.

If the overall circumference of the outside tyre measurement changes though, then yes, a bigger circumference will make the speedo read slower, a smaller circumference will make it read faster.

Usually manufacturers are aware of this and will decrease their stock tyre aspect ratios as the inner diameter gets bigger (15 to 16 to 17, say).
Decreasing the ratio (height to width of the rubber) keeps the overall circumference pretty close to the other wheel/tyre combo's available. There will be some slight difference to speedo readings, but not much.  
If the circumference does change significantly manufacturers normally change the output of the speedo sensor to compensate.

The real problem comes when the 18 year old boy racer puts 21 inch wheels on a car designed for 14 inch ones, and doesn't compensate the speedo sensor.  (Ah... maybe that's why they ALL break the speed limit ALL the time !!)

In Oz I think new cars are permitted to have up to (around) an 8% HIGH speedo error. On something like the i30 with three standard wheel sizes, that margin gives a lot of room to play with wheels and ratios, without having to mess with speedo outputs.

For info (I don't know if you know or not) the tyre numbers above that look like 225/45 17... means 225mm wide, height of the tyre wall is 45% of the width of the tyre, and the inner diameter is 17 inches. Yes... a MIX of Metric and imperial measurements !!!  See here for more info.
As an example, on the OZ i30's the three stock tyre sizes are 195/65 15. 205/55 16. 225/45 17 - See what I was saying earlier? As the rims get bigger and wider, the tyre ratios come down.

(Now you can see that in the thread example, 50% of 225mm is taller than 45% of 225mm - thereby increasing the overall circumference. Hence the speedo warning Accim gave in his reply.)

Most new cars (if not all) have some error in the speedo.
To see how much error your new car's speedo has, borrow someones GPS (if you don't have one) and set it to show speed. Check it against the snowmobile's speedo.  The GPS will be near enough to spot on (nature of how they work), your speedo SHOULD be within 8%.  My Toyota is spot on, the i30 reads about 3-4% high (SLX Stock 16 inchers).

Hope that helps...

Blue.

[karhung]

Read this and you will understand a whole lot more about wheels and tyres.

A bit long tho!!!!!

http://www.carbibles.com/tire_bible.html

[Franciskano]

Thanks everybody.

In my country (Brazil), the i30 was released in september 2009 and all versions comes with the 225/45 R17" tyres.

It was some kind of marketing because of the beautiful wheels, but they forgot that our streets have more holes than the moon.

That´s why I want to replace my 225/45 R17 for a 225/50 R17.

[Blue]

 but they forgot that our streets have more holes than the moon.

Ha, not unlike here Francis, you often find pot holes with old VW Beetles stuck in the bottom of them !

Not as bad as these though !

[accim]

Pff..than maybe if 225/45/17 is a bit hard for you, try 205/55/16..but you'll have to buy new rims and the car won't look as pretty 

[snowcherry]

accim and Blue - two great replies for me thank you!
i've read them through and understand the general concept of it now at least, though the finer points still largely escape me. i was initially concerned my 17's would be causing me to be 'speeding' but i guess not

it is interesting though
karhung - thank you for that link to but i've decided to save that one for now when it doesn't make me glaze over 

[2i30s]

my scangauge tells me that I'm doing three ks slower than my speedo actually reads,I've got 225/45 /17.i haven't checked that figure with stock 15" rims and tyres maybee another owner with a scangauge and 15s can answer that.

[Blue]

my scangauge tells me that I'm doing three ks slower than my speedo actually reads,I've got 225/45 /17.i haven't checked that figure with stock 15" rims and tyres maybee another owner with a scangauge and 15s can answer that.

Near enough to the same as mine (against GPS) on 205/55 16's.

[2i30s]

my stock rim and tyre standing beside my 17s doesn't look much different.[but thats not a very good way to check over all diameter]

[Franciskano]

LoL!

I can´t buy new rims because i´ve spent a lot of money in the car.

Just ilustrating, in Brazil de i30 costs R$65.000,00 (about U$35.000,00) and the minimun wage is U$240,00...

I was going to replace the 225/45 17" with the 225/50 17" but a doubt appeared:

If I have to use the Spare Wheel, it will have a smaller diameter than the 225/50 17". Will it be a problem?

tks again!

[accim]

It's definitely not recommended to have different diameter..i totally forgot about it.. What size of spare one do you have? Probably 195/65/15 or 185/65/15 or maybe even smaller?

Quite expensive i30's you have over there and such low wages..our min. wages are around US $ 580 and i30's are much cheaper.. Now you can get one (basic) for US $ 17,500..

[Franciskano]

The hyundai mechanic said that if I replace the tyres, the spare wheel won´t be a problem, because it is recommended to drive just few miles with it (maximun 80km/h).

A i30 Club member (Brazil), replaced the tyres and said that the i30 got almost as confortable as the Azera he also has.

[felipe3k]

Guys, altought it does not explain the absurd price of the i30 here in Brazil, the ones they sell here are pretty much FULL, in other words, they come with all the optionals you can have in a Hyundai... 8 airbags, full ABS ESP, power sunroof, 2.0l 150hp engine, 17" inch wheels, Digital Air Conditioning, Digital radio, full leather, Automatic Gearbox....
I repeat, it DOES NOT justifies the price, but then again, Hyundai here in Brazil is still considered to be a "luxury" car... and its imported.


Por sinal, tambem to pensando em mudar meus Pneus...
de 225/45 pra 225/50.... na realidade to querendo ir pra 18"... acho que vai preencher melhor a caixa de rodas.

[Franciskano]

Felipe, be careful to not alter much the diameter of the wheels, it has to be no more than 3,5% bigger or you will alter too much the car aspects, as CPU and safety.
If you replace the 225/45 R17 for any R18, it will become harder than before.
The ideal (and safe) replacement is 225/45 R17 >> 225/50 R17.
Are you a i30 Clube member? (http://i30brasil.forumeiros.com)

ADMIN EDIT: GUYS - ENGLISH ONLY PLEASE!

[felipe3k]

Franciskano,

ADMIN EDIT: GUYS - ENGLISH ONLY PLEASE!

Hey franciskano...
Yeah i just logged it, but havent found anything there yet... maybe im looking in the wrong place....
Anyways, i got what you said about the 18"...
thanks:!!!