Wheels offsets help

[fennyLET]

Rite. I get rather confused about wheel offsets and so on.

Ive put coilover's at the rear on my Astra so ive now goto be abit carefull what offset wheels i use.

I just tryed on a E49 offset wheel with a 195 wide tyre on and that doesnt hit.

So what offset would i need to run say either a 205 or 215 wide tyre? If i put them on the wheel i just tryed. I think it will rub on the spring's.

Reason is. I want to buy another set of wheels for the Astra and i dont want to end up with some that dont fit.
Im not too worryed about the fronts as my mate is going to mod my F/G wings so they are abit wider.

Cheers all

[Cheddar]

I'm pretty sure that if the wheel and tyre's 205 wide then you'd need 10mm less offset (39) and if its 215 then it'll be 29 offset

[fennyLET]

I may be wrong but i didnt think say 205 was in mm? I thought it was all todo with %. Like the profile is so many % of the width ect.... Cheers anyway. Thats abit of help

[Cheddar]

Yeah they measure the width in metric (mm) and the diameter of the alloy in inches just to confuse everyone! ET49 means that there's 49mm between where you put the nuts in and the centre of the wheel if thats makes sense so the smaller the offset the further out the wheel will be.
The % is like you say used for the profiles.

[fennyLET]

Googled and found this.



The offset of a wheel is what locates the tire and wheel assembly in relation to the suspension. More specifically, it is the measured distance between the hub mounting surface and the center line of the rim. Below is an explanation of the various types of offsets which are pictured in the above graphic.

Positive Offset
A positive offset occurs when the hub mounting surface is on the street side (the side you see) of the center line of the rim. Most factory rims will have this type of offset.

Zero Offset
When the hub mounting surface is centered within the rim, it is known as a zero offset.

Negative Offset
If the hub mounting surface is on the brake side of the center line of the rim, it is considered a negative offset or “deep dish”.

Note that extensive negative offset can potentially cause increased steering wheel kick-back and place additional stresses on the vehicle's entire suspension.

[fennyLET]

Yeah they measure the width in metric (mm) and the diameter of the alloy in inches just to confuse everyone! ET49 means that there's 49mm between where you put the nuts in and the centre of the wheel if thats makes sense so the smaller the offset the further out the wheel will be.
The % is like you say used for the profiles.

Cool, cheers mate.

So to run 215 wide tyres i will need ET29 wheels?

I guess it will then throw it 20mm out (Poke out the arches?)

[Cheddar]

Yeah thats the trouble, as soon as you start mucking about changing the offset your handling will go up the creek.
Actually i've cocked that up, if you put a 215 tyre on it'll be 20mm wider but only 10mm each side so you could have a offset of et39 with a 215.
I'm confusing myself now

[MikeWarner]

I'm pretty sure that if the wheel and tyre's 205 wide then you'd need 10mm less offset (39) and if its 215 then it'll be 29 offset

No - the wheels gets 5mm wider on each side, so you only need to reduce offset by 5mm. However, that isn't alway the best strategy, as the outside may start rubbing before the inside. A typical size with 205s would be et45 irrc (a common size).

[fennyLET]

This is going to be a rite pain to sort out! Why o why do i have to do things the hard way lmao

[MikeWarner]

On a mk3, Et45 7" wide with 205-40-17 should fit fine (and a safe bet imho).

[TINTIN]

On a mk3, Et45 7" wide with 205-40-17 should fit fine (and a safe bet imho).

Is that including the factor of his coil overs?

[fennyLET]

Problem is.... Ive now got rear coilovers. So say the shock is now 2.5" across insted of 1.5".

The springs sit closer to the hib than what the old shocks did. Hence my little problem lol

The front wont be a problem.

[MikeWarner]

Yeah - but I would recommend trying some first if he can. Maybe get under the car and see how much clearance is currently available. You can always space things out a bit with spacers, but you can't space things inwards, so going for a higher offset is safer if you are unsure of fitment.

[TINTIN]

Problem is.... Ive now got rear coilovers. So say the shock is now 2.5" across insted of 1.5".

The springs sit closer to the hib than what the old shocks did. Hence my little problem lol

The front wont be a problem.

You just have to be bloody awkward dont yalmao

[fennyLET]

On the ET49s with 195s. You cant quite get your little finger behind them. But there is enough room. So with 205s or 215s i would need less offset? like 205/ET43? 215s/ET39?

[fennyLET]

You just have to be bloody awkward dont yalmao

sorry lmaolmao

[MikeWarner]

But you have to be careful to not hit the outer arch too. lol

[TINTIN]

On the ET49s with 195s. You cant quite get your little finger behind them. But there is enough room. So with 205s or 215s i would need less offset? like 205/ET43? 215s/ET39?

Hover pads like Harrier jump jets maybe, lol

[MSG]

As for handling with larger offsets, you will soon adapt to the car's new handling characteristics, takes a few days to sink in, but also one has to remember larger offset can also impose a lot larger load on the front wheel bearings due to the way they are set up in the hub, particularly FWD cars can suffer from excessive wear due to increased loading and my Calibra now whines when moving, I am used to it now and probably will need to change my bearings soon, but its only a silly whine that I can live with for now and as it gets worst I will need to take action as the bearings can disintegrate at high speed!

[fennyLET]

But you have to be careful to not hit the outer arch too. lol

I know lmao This is the problem

Hover pads like Harrier jump jets maybe, lol

Would it still be clased as a car

As for handling with larger offsets, you will soon adapt to the car's new handling characteristics, takes a few days to sink in, but also one has to remember larger offset can also impose a lot larger load on the front wheel bearings due to the way they are set up in the hub, particularly FWD cars can suffer from excessive wear due to increased loading and my Calibra now whines when moving, I am used to it now and probably will need to change my bearings soon, but its only a silly whine that I can live with for now and as it gets worst I will need to take action as the bearings can disintegrate at high speed!

ALOT has changed on the car anyway so ive got to get used the handerling again anyway so thats no biggy
I did read about the "extra load" bit and yes, perticulary FWD car's

I wonder if when i buy some and if they are new that they will sell me two different offset wheels would be handy lmao

[TINTIN]

Hover car for the win!

[fennyLET]

lmao would be quite cool but no thanks lmao

[TINTIN]

Spoil sport

[fennyLET]

So.... im still none the wiser on what offset i should go for lmao

195/55/15 et49 does fit.
So what do i need to run either 205 or 215 tyres on 17" wheels?

[MikeWarner]

In your situation, I'd go for the narrower, the 205s.