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DEFINATIVE OFFSET THREAD - SURELY ?


Jixaman

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A bit long but here is how I calculated my wheel spacers... The sums say 20 front and back , my front arches are rolled already but with the rear spacer going up to 20 will need to do the rears too...

 

 

 

Awaiting a reply from Ewen at Clark Motorsport on his thoughts, I’m switherin about extending the arches and going with the 25 rear... Anyway, heres the calcs...

 

 

 

 

 

REAR

How will the wheel look?

Hub mounting surface is 129mm from edge of the body at farthest point.

Outside edge of wheel is 103mm from mounting surface.

DBA T3 thickness at Mounting surface = 5mm.

(129-5)-103 = 21mm to edge of body.

20mm spacer.

 

 

Will it fit the brake calliper?

Calliper mounting surface on car is 78mm from hub mounting surface.

Calliper mounting surface on calliper to widest point on calliper is 102mm.

102-78 = 24

Calliper sits out 24mm from hub face.

Centre of axle to centre of calliper mounting point on car is 118mm.

Centre of calliper mounting mounting point to outer radius of calliper is 77mm.

118+77 = 195

Brush point ends at 195mm.

Spoke on wheel at narrowest point is >= 195mm.

Wheel mounting surface to wheel spoke @ 195r = 24mm

Add DBA T3 brake disc of 5mm and wheel spoke sits 29mm out from hub.

(29-24)+20 = 25

Clearance from calliper with 20mm spacer = 25mm. Good to go...

 

 

FRONT

 

How will the wheel look?

Hub mounting surface is 115mm from edge of the body at farthest point.

Outside edge of wheel is 86mm from mounting surface.

PFC thickness at Mounting surface = 8mm.

(115-8)-86 = 21mm to edge of body.

20mm spacer.

 

Will it fit the brake calliper?

Calliper mounting surface on car is 71mm from hub mounting surface.

Calliper mounting surface on calliper to widest point on calliper is 117mm.

117-71 = 46

Calliper sits out 46mm from hub face.

Centre of axle to centre of calliper mounting point on car is 80mm.

Centre of calliper mounting mounting point to outer radius of calliper is 112mm.

80+112 = 192

Brush point ends at 192mm.

Spoke on wheel at narrowest point is >= 192mm.

Wheel mounting surface to wheel spoke @ 192r = 29mm

PFC brake disc of 8mm and wheel spoke sits 37mm out from hub.

(37-46)+20 = 11

Clearance from calliper with 20mm spacer = 11mm. Good to go...

 

 

As far as I can see the calcs look good, the only variable is the hub to body measurement as its sprung and changes depending on how the car is sitting but its the only measurement I have (I took an average of both sides).

 

 

Also noticed on BMi, doing a tyre feature 18 vs 19 inch. I will say just now, Zman Alex did tell me that for tracking to stick with an 18†setup, this feature explains why... I have 19’s... ...... .......... Can see me buying a cheap set of 18’s soon...

 

( http://www.youtube.com/watch?v=o6Glkf4jwkM&list=WLyKy40HO3pwXCe8mnuYyQZid2uS4OTshs)

 

Test car was the Z and its paused at the info bit on the tyres / rims.

 

Original was 18â€

F 225/45R18 on an 18x8.5 30 offset.

R 245/45R18 on an 18x8.5 30 offset.

 

 

Option was 19â€

F 245/35R19 on a 19x8.5 22 offset.

R 275/35R19 on a 19x9.5 22 offset.

 

The option is the same setup as what I have except for the offsets (mine are both 34) and they (BMi setup) are visibly farther out with a little bit spare (that my setup will use). The difference between the BMi setup and my wheels with the intended spacer is 8mm front and rear which I think will be touch n go but to clear the front callipers with room to spare this is the way... M, other variable here is its a different wheel so calliper clearance will be different.

 

 

 

Hope this helps, I have drawings but there more like scribbles I used to get my head round what I had to do...

 

Cheers...

Edited by glrnet
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5 things:

 

1: there are offset calculators to work out these kind of things online

2. the setup youve finished up with is a bit weak, TBH

3. theres no difference in performance or grip on an 18/19, only weight

4. What are you trying to achieve, why are you going to run spacers?

5. Are you actually asking anything here? :lol:

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1. Not confident they can tell you if the wheel will clear a calliper, spokes are cast in different shapes etc...

2. How come, all advice welcome....

3. Car companies, tire manufacturers and professional drivers differ, granted I might not notice but I'm just normal...

4. To make the wheels fit, the calcs show I need them (albeit a little smaller than I am going for but Eibach don't make those sizes)...

5. For info / discussion only...

 

:teeth:

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Furry muff, in that case I can tell you that you are right, caliper clearance can be an issue (which is why I have 75mm arch extensions :lol:) but disc information, manufacturers info and real life experience are often more reliable than calculations.

 

On the weak bit, I personally believe 9.5 ET10 and 10 ET10 is perfect for a 350Z, youre a lot on the smaller side than that, do you already have the wheels? If so, are you spacing them to make them look better? :)

 

Im a bit confused by all this, Ive had probably 20 sets of wheels for various cars and all Ive ever checked is the offset calculator, Im still not sure what you are trying to achieve here - if the wheels are going to catch the calipers then just buy lower offset wheels ........

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