scottm078

hi guys, i have a question about wheel backspacing and offset. ive done searches and done a lot of reading but somethings i just dont get..lol. i would like to put on the rims in the link. i plan on doing the c5 brake upgrade and dont plan on lowering the car unless there is a huge fender gap but the car will be street driven and dont want it too low. eventually ill swap the rear with a 4th gen or equivalent. i would like to not use spacers in the front. i know id probably have to get custom wheels made. since this is a future mod im just brainstorming right now. if i go with 18x8.5 front and 18x10 rear what would the backspacing and offset have to be so i wouldnt have to use spacers?

http://www.corvette-wheels.com/c6-chrome.html

p.s. thank you for all your help in advance, love this site.

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iTrader: (14)

4.75" to 5" in the front.

6 to 6.5 on the rear. You may have to do some hammering in the rear, the front of the well and the bumpstop area to fit 6.5. 6 will put the wheel just about flush with the outside of the car. Personally, i say do the 6.5.

scottm078

86ta thank you for the reply. on the rear you said youd go 6.5. if 6 is putting the tire about flush with the outside wouldnt 6.5 stick it out past that or is it the other way around?

//<86TA>\\

iTrader: (14)

no, the more back spacing, the deeper in the wheel well the wheel will site.

6.5 will put the wheel about 1/2" +/- in from the side of the car.

"backspacing" is the distance from the mounting surface of the wheel, to the inside lip of the wheel.

"offset" is the difference from the actual center of the wheel to the mounting surface, positive would place the mounting surface further from the wheel well, negative would bring the mounting surface closer to the wheel well.

i have 18x8's with 4.5" of BS in the front with the c5 brake upgrade, and i would not want to see them any further outboard. they are about perfect, so add .5 to the wheel, to the inside of the wheel, and you get 5" of BS.

rears, i had the same 18x8 wheels, and they sat in the wheels perfectly, when i had them widened to 12", i have all the extra material added to the inside making 8.5" of backspacing. the car is now mini-tubbed to fit them

scottm078

thank you for the reply and explanation. im starting to get it now. i guess where i get messed up is the offset. should i keep that close to stock for a c6 wheel? if i get the wheel with that much backspacing wouldnt i have to change the offset to balance the wheel out? i dont know if there is a proper backspacing to offset ratio or a formula to follow or anything.

//<86TA>\\

iTrader: (14)

backspacing and offset are just different ways of measuring wheels, you dont usually use both. I gave you the BS needed, that BS also correlates to a offset, if you then change the offset, the backspacing changes too.

with 4.75" of front backspacing, the offset is ~"0" because the wheel mounting point is in the center of the wheel. with 5" of bs, the offset would be positive 6.35 mm, or 1/4 inch, because the mounting surface is 1/4" from the center of the wheel

the rears, 6.5" of bs are 25.4mm positive offset, because the mounting surface it 1" (25.4mm) off center.

make sence yet

BTW, wheels generally measure an inch or so wider than their advertised width, since the advertised width is the distance between the bead seats, no the overall width. The diamater is the same way, so a 18x8 wheel actually measured something like 19x9 overall dimensions. thats why the offset may seem a little off to you.

scottm078

after i read and reread what you just wrote it all of a sudden clicked. i was wondering why the offset changed when the width changed. im not normally this slow at picking up things..lol. thank you for taking the time to help me understand this.

//<86TA>\\

iTrader: (14)

no problem