What offset is better for a Gemini

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Dyllan1
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What offset is better for a Gemini

Post by Dyllan1 »

Does anyone know if
Gestalt 19 inch wheels will these fit a Gemini with a offset of 7.5 or 8
Or will both off sets fit?
RedGemCoupe
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Post by RedGemCoupe »

You could probably make them fit by pumping the guards although it would most likely not be legal.

In QLD you can only increase the track of the vehicle by 13mm per side.
Standard Gemini offset is 30mm positive so legally you shouldn't be able to go any less than a 17mm positive offset. (The smaller the offset the wider the track of the vehicle.)

I have seen a Gemini with 19's and from a distance it looks like the car is running on the rims. There is virtually no side wall on the tyre.
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06EMInick
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Post by 06EMInick »

7.5 or 8 is the width it is not the offset.

You're considering buying 19s, so I don't really want to help you anymore.

kthxbi
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Dyllan1
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Post by Dyllan1 »

Ok well I have 17s ATM and they got 205/40s on them and they have no sidewal at all but yeah I'll just pump the guards might have to change the lowered springs as well I guess
There's a car on car sales
He wants 40g for it and it's rotory he has the same wheels and they don't look like there hitting the guards so I'll trial fit 19s I guess
lukes_tg
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Post by lukes_tg »

noticed why no one has bought it? because those rims a homo as f*#k yet people are still putting them on???
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t3/t4 haltech powered forged 4ze1 gemini in the build
DryftKult
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Post by DryftKult »

work miesters or simmons fr18's

just a side note, but I have heard and confirmed that tempe tyres have bought all the tooling from simmons and are now producing simmons fr series wheels but using billet centers!!!

2400 with tyres, any offset you want.
Germinator
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Post by Germinator »

Just a side note, apart from it seeming like you thought width of the rim was the offset:

Offset for any given rim is relative to the width of the rim you are questioning. There is no 'right' general offset without also knowing the width of the rim.
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RedGemCoupe
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Post by RedGemCoupe »

The offset of a vehicle's wheel is the distance between the centerline of the wheel and the plane of the hub-mounting surface of the wheel.
[from wikipedia]
So it is relative to the centre line of the wheel.

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Germinator
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Post by Germinator »

Correct, so as the rim width changes the offset required to clear between the inside edge of the rim and suspension/steering components will also change. Therefore a 6 inch wide rim with +30mm offset will place the inside rim edge in a different position to a 8 inch wide rim with +30mm offset.

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The most important figure is the backspace needed. Hand me that backspace measurement and I'll tell you what offset you need to look for.
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06EMInick
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Post by 06EMInick »

Dyllan1 wrote: There's a car on car sales
He wants 40g for it and it's rotory he has the same wheels and they don't look like there hitting the guards so I'll trial fit 19s I guess
It looks like a Rollerskate.
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RedGemCoupe
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Post by RedGemCoupe »

Does anyone know the maximum backspace for standard Gemini offset?
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troyrotor
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Post by troyrotor »

to get an idea on how much offset changes due to the width of the tyre.

My 13 inch rims 6.5inches wide have an ofset of 8.
My 18s are 7.5inches wide with an ofset of 40.
They both have the same tyre diametre and sit in the exact same spot in the wheel arch.

So with a 1inch increase in width the ofset has changed by 32mm which is over an inch.
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leviathan937
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Post by leviathan937 »

troyrotor wrote:to get an idea on how much offset changes due to the width of the tyre.

My 13 inch rims 6.5inches wide have an ofset of 8.
My 18s are 7.5inches wide with an ofset of 40.
They both have the same tyre diametre and sit in the exact same spot in the wheel arch.

So with a 1inch increase in width the ofset has changed by 32mm which is over an inch.
That is also relative to the diameter of the rim, 17x6 will fit with the +30 offset (same as standard (or is it +35? i can't remember)) a smaller diameter might not (will not) fit if it is much wider than standard because it will foul the shock, (hence the +8 offset on your 13x6.5s)

using the same as standard offset with a wider rim will make both sides of the wheel equally wider, to an extent, the bigger the rim diameter the more likely it is to fit with as close to standard offset.
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Germinator
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Post by Germinator »

It's probably a whole lot easier to work with backspace than offset. You can easily measure backspace by fitting a known wheel rim and getting under the car with a steel rule to measure clearance from the shock to the rim lip. Once you know that distance and know the specs of the wheel you just measured it's easy to select a suitable offset for any other rim width.

Measuring the offset of an unmarked offset rim with known width is easy too. Just lay the rim face down on the ground and grab a length of wood or steel that sits neatly on the opposite rim edges (if it sits on the tyre, shorten it to clear) then measure between the length and the mount face of the rim, that's the backspace. From that figure it's easy to work out what any other rim width/offset combination will clear the shock by (or touch and bend the shock by) as well as to figure out the offset.
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Germinator
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Post by Germinator »

Lets start by using a standard rim...

if we go with a 13"x5" with +35mm offset, backspace is 111mm.

13"x6.5 with an offset of et8 will have a backspace of 103mm. (8mm further away from the shock absorber)


18"x7.5 with an offset of +40mm will have a backspace of 148mm. (37mm closer to the shock absorber) With such a large positive offset number, these are definitely FWD rims and I doubt they would clear the shock absorber when the front wheel is jacked up off the ground.

17"x6" et30 have a backspace of 118 (7mm closer to the shock absorber)


17"x6" et35 have a backspace of 123 (12mm closer to the shock absorber)
A reasonable test is to measure the clearance between the rim edge and the shock absorber when the wheel is fitted at it's fully jacked up point. You should be ideally looking at 10mm clearance, certainly not less than 5mm.


Now it isn't JUST a case of getting offset right for proper suspension part clearance if you want to keep things legal, there is also the question of track change allowance. You can't narrow the track at all so if you want to run FWD high number offset rims you're probably going to find you have reduced the track so it's illegal from that aspect as well as highly likely to be touching the shock absorber.
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