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Absolute Newbie Aftermarket Tire/Wheel/Offset Questions :newbie:

To enhance tire grip for occasional autocross and improved cosmetic appeal, I am changing from the OEM 6.0” wide front tires to Avanti ST-1 15” X 7” 35 mm offset wheels. I am also changing from the OEM 6.5” wide rear tires to Avanti ST-1 15” X 7” 15” 35 mm offset wheels. The new Avanti wheels also have a 73mm Center Bore.

So, by my calculations ---which very well could be wrong, having never done this before--- the additional rim width would change my wheel offset to 47.7 mm front, 41.35mm rear. If my calculation is correct ----and if it is not correct, feel free to give me the correct numbers --- both front and rear offsets are so close to the OEM wheels that handling should be very minimally impacted, if at all.

Is there any advantage of reducing wheel offset below OEM original, other than visual, by putting the tires closer to the fender/outside of the car?

In a similar vein, how will my (maximum) 1” increase in wheel width over the OEM stock wheels impact on SCCA sanctioned or other autocross class participation”

Problem Number two:

OEM stock wheels have a Center Bore of 54.1 mm. Avanti ST 1 wheels have a 73mm Center Bore. I am correct that for optimal performance I will need to install 73/54.1 mm hubcentric rings? Do I need any special lug nuts or studs in order for the hubcentric rings to perform optimally.

Any/All feedback is appreciated!

Thanks In Advance!

Paul
 

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Most if not all aftermarket wheels use conical lug nuts. They are different from the OEM flat face lug nuts. You need to purchase a set. They are not interchangeable.

You are absolutely correct you do need hubcentric rings if you wish to avoid issues with vibration from unbalanced uncentered wheels. They are cheap and easy to come by.

Effect of offset in the range you are talking you are not going to notice.
 

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Paul,
Offsets do make a difference for better or worse in my case. I like the factory offset because the car is more lively and responsive but the wider offsets look better.
I have tested both my factory wheels and my after market (offset of 37) back to back on several occasions and felt a profound difference.
Please check out the thread I made below where I expressed my thoughts in detail. Offsets also changes the handling characteristics, please research scrub radius.

http://www.spyderchat.com/forums/showthread.php?44695-OZ-Ultraleggera-does-it-work
 

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Does anyone know the scrub radius of the spyder?

If you want to know what the difference in offset would feel like, get some spacers and put them on your current setup.
 
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