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Discussion Starter · #1 · (Edited)
I am thinking to move from my 7.5x17" wheels to 8.5x20". I would like also to fill the gap between fender and tyre. Tyre option would be Nakang NS-2 245/35 (or 235/35 as a second option).

LEFT=CURRENT SET-UP
I know that I have 17MM to the fender because I am running 17MM spacers and tyre is right on the fender.
Based on current set-up, the lowest offset I could run is 30MM before pasing the fender.

96796



I have measured it a lot of times but still having some doubts basically on the suspension side.
It is very hard to measure it properly as there is not much room, that was the best photo I could take.
96797


There is more or less 40MM to the suspension before it start the curve. Less the 17MM front the spacers = 23MM (Orange line)
Biggest OEM set-up on front axle is 225/40 8x19" offset 33MM. That makes an overall wheel diameter of 663MM
245/35 8.5x20" overall wheel diameter is 680MM. That means that I would fill extra ~9MM (Green line).

Tyre would be pretty close to the suspension....
My concerns are about tyre strech while turning and also the fact that I was not able to measure it properly.

Questions:
1. Do 8.5x20" wheels fit base giulia ?
2. Do 235/35 20" or 245/35 20" tyres fit base giulia?


Cheers !
 

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I can't answer all your questions but I would say this. I have 8.5j wide 19" tyres at the front which are 235/35/19 in my base Giulia and there is plenty of room. My wheels are QF size and offset. I can go 245 if I wished. As long as you keep the rolling diameter of the 20" tyre the same as the 17" tyre, 225/50/17 which is what I had originally, I dont think you will have any issues with 8.5j assuming you keep the same offset as the QF. Others with more knowledge will be able to guide you better.
 

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Discussion Starter · #3 ·
I can't answer all your questions but I would say this. I have 8.5j wide 19" tyres at the front which are 235/35/19 in my base Giulia and there is plenty of room. My wheels are QF size and offset. I can go 245 if I wished. As long as you keep the rolling diameter of the 20" tyre the same as the 17" tyre, 225/50/17 which is what I had originally, I dont think you will have any issues with 8.5j assuming you keep the same offset as the QF. Others with more knowledge will be able to guide you better.
Thank you for the info !
So, first question would be clear.
The second one is the one as I would like to increase the rolling diameter. Could you please check the space you have to the suspension ?
As you have 19" I think we would have less error than measuring at 17"
 

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I don't have my car with me at present to measure but what you are trying to do is a "plus 3" sizing, going from 17" to 20" which is quite a lot.

For 19" , 245/35/19 is OEM size and same overall rolling diameter as 225/50/17. The aim is to keep rolling diameter always the same whilst increasing alloy wheel diameter. This is done by shorter sidewall tyres as you go to larger wheels. So if you go to 20" you chose a different tyre size to maintain the same overall rolling diameter. You want the difference to be less than 3%. See attached.
And also this calculator should help. Enter your current and new sizes plus offset, it will give you a visual and number comparison. Going to 20" will mean you will end up with very short sidewall and worse ride and if roads are bad, risk of wheel buckling if you hit potholes.


Text Font Line Number Parallel
 

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Discussion Starter · #5 ·
I don't have my car with me at present to measure but what you are trying to do is a "plus 3" sizing, going from 17" to 20" which is quite a lot.

For 19" , 245/35/19 is OEM size and same overall rolling diameter as 225/50/17. The aim is to keep rolling diameter always the same whilst increasing alloy wheel diameter. This is done by shorter sidewall tyres as you go to larger wheels. So if you go to 20" you chose a different tyre size to maintain the same overall rolling diameter. You want the difference to be less than 3%. See attached.
And also this calculator should help. Enter your current and new sizes plus offset, it will give you a visual and number comparison. Going to 20" will mean you will end up with very short sidewall and worse ride and if roads are bad, risk of wheel buckling if you hit potholes.


View attachment 96820
I have already checked all these things (I have used a tyre calculation tool also, see first post).
The biggest OEM tyre used front axle is 225/40 19" with overall rolling diameter of 663MM
245/35 20" overall rolling diameter is 680MM
235/35 20" overall rolling diameter is 673MM


96821



The main question is,
Do 245/35 20" tyres fit base giulia ?
Otherwise, Do 235/35 20" tyres fit base giulia?
 

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I have already checked all these things (I have used a tyre calculation tool also, see first post).
The biggest OEM tyre used front axle is 225/40 19" with overall rolling diameter of 663MM
245/35 20" overall rolling diameter is 680MM
235/35 20" overall rolling diameter is 673MM


View attachment 96821


The main question is,
Do 245/35 20" tyres fit base giulia ?
Otherwise, Do 235/35 20" tyres fit base giulia?
@MikeFish fitted 20" wheels but that was in a QF. You may want to search for his posts to see what tyre size he used. I don't think there is any difference in suspension shape between base and QF. I am not 100% sure though.
 
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