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Correct tyre for a 18x7.5


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#1 MrSober88

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Posted 03 November 2016 - 09:42 AM

Hi Guys,

 

Trying to find out some info on what tyre size I should be using for a rim I have lying around that I am thinking about putting on the S-Edition, I have a set of Buddy Club P1's in 18x7.5 and thinking about putting these on my S-Edition that comes stock with the 17x7 225/55R17.

 

Using calculators it seems the best fit is 245/45R18 but not sure if this is too wide as I can't really find that info. The other option I was looking at was a 235/45R18.

 

As far as I have found out online the offset of the stock STI's are +48 and from the ad I bought the Buddy's from say they are +48 also. 

Any help would be greatly appreciated. 



#2 MrSober88

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Posted 03 November 2016 - 09:55 AM

Also what is the stock load rating for the Forester?



#3 Robert

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Posted 03 November 2016 - 10:36 AM

The s edition rims already have oversized tyres

The best fit for a 7 inch rim is 215
7.5 is 225 that's what I run on my 7.5 inch rim

As for the profile of the tyre a 225/45r18 would look pretty nice
I'm pretty sure that's the usual specs for a foz
No point having rubber band tyres

As for the load rating I'm not sure, it will be on the tyre place card in the door jam

#4 MrSober88

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Posted 03 November 2016 - 10:57 AM

Cheers for that, I will have to take a look when I get home.

 

Good to know as I wasn't all that sure on what size it should be, Hopefully its around 95 or I won't be able to get the tyre I was looking at.



#5 Beckers

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Posted 03 November 2016 - 05:11 PM

I got sum SG9 sti rims, they are also 18 X 7.5.

The RE003 in 225/40/18's fit really well, but the ride will be quite hard.

This size was the perfect upgrade from the 225/45/17's I had before.



#6 RX25SE

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Posted 03 November 2016 - 10:35 PM

As above, 225 is a good width for a 7.5 inch rim. Use one of the online tyre size calculators to work out how the different sizes effect diameter compared to the standard size, aim to keep diameter within 3% if possible.
The tyre placard on the vehicle will list original size, load and speed ratings. You can exceed load and speed ratings, but you can't legally go under.

235 and above is too wide for a 7.5.

If I told you I was a compulsive liar, would you believe me?

 


#7 MrSober88

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Posted 04 November 2016 - 10:38 AM

I got sum SG9 sti rims, they are also 18 X 7.5.

The RE003 in 225/40/18's fit really well, but the ride will be quite hard.

This size was the perfect upgrade from the 225/45/17's I had before.

 

225/40R18 would be a -6.2% difference which is a little to much as my stock ones are 225/55/r17 

 

I am looking at the 225/45R18 in the RE003's but this is a -2.89% which sounds like the goods. 

 

 

As above, 225 is a good width for a 7.5 inch rim. Use one of the online tyre size calculators to work out how the different sizes effect diameter compared to the standard size, aim to keep diameter within 3% if possible.
The tyre placard on the vehicle will list original size, load and speed ratings. You can exceed load and speed ratings, but you can't legally go under.

235 and above is too wide for a 7.5.

 

Yeah I have been looking at a lot of them to work out what would work well. At the moment the 225/45R18 seems to be the one I should go for. 

 

Can anyone explain how the 235/45/R18 is a different circumference than the 225/45R18? I can understand how a wider tyre affects the circumference.

 

 

They can get me the RE003's in 225/45R18 for $690 with the buy 3 get 1 free deal. This is cheaper than the stock size.



#8 RX25SE

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Posted 04 November 2016 - 11:13 AM

The 45 is aspect ratio.
It means the sidewall height is a percentage of tread width.

If the aspect ratio and rim diameter remain constant, as the tread width increases, so does the overall diameter.

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#9 MrSober88

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Posted 07 November 2016 - 11:13 AM

The 45 is aspect ratio.
It means the sidewall height is a percentage of tread width.

If the aspect ratio and rim diameter remain constant, as the tread width increases, so does the overall diameter.

 

Thanks for clearing that up for me, I could not get my head around it lol.






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