11" ET44 vs GT4 11" ET30

[SYT_Shadow]

There's something I struggle to understand and I'm hoping someone can set me straight.

Apex did a lot of testing back in the day and came up with the perfect rear fitment for F8X cars: 11" ET44

Meanwhile, the OEM GT4 wheel fits the rear F8X cars and is 11" ET30


What gives? 14mm offset difference is massive. I don't see how 11" ET44 is the max wheel width on inner and outer clearance yet people are fitting the 11" ET30 wheel.

[RSXDC5]

Originally Posted by SYT_Shadow

There's something I struggle to understand and I'm hoping someone can set me straight.

Apex did a lot of testing back in the day and came up with the perfect rear fitment for F8X cars: 11" ET44

Meanwhile, the OEM GT4 wheel fits the rear F8X cars and is 11" ET30


What gives? 14mm offset difference is massive. I don't see how 11" ET44 is the max wheel width on inner and outer clearance yet people are fitting the 11" ET30 wheel.

I believe it was the +30 offset that allowed them to use their biggest spacer up front to enable wheel/tire rotations. That said, the approach is crap, bad front and rear fitment. Your front scrub radius is massive with a ~25/30mm spacer, and your max rear fitment is super compromised on the outside with a +30 in play.

Apex's fitment was also fairly conservative. I'm a 11.5 +44 rear and have never rubbed once in 5yrs, under any circumstance (i.e. with a fully loaded car, on track, etc.)

[F80Speed77]

I was going to say that GT4 is a spec tire so they are probably running something that measures to a 295 or so on that wheel.

[fanatic1]

Lowered on MCS coils and running -2.7°, with 18x11 ET44 and this was the result. Partially due to running oversize Perelli DH, but seriously considering those 18x11 ET30s. Friend is running similar ride height and camber and ET30s are working well for him.

Not real excited about the front spacer required to rotate, but can’t image the front spacer required for ET44.

My take away, ET44 is best for stock suspension/alignment settings

[SYT_Shadow]

Originally Posted by fanatic1

Lowered on MCS coils and running -2.7°, with 18x11 ET44 and this was the result. Partially due to running oversize Perelli DH, but seriously considering those 18x11 ET30s. Friend is running similar ride height and camber and ET30s are working well for him.

Not real excited about the front spacer required to rotate, but can’t image the front spacer required for ET44.

My take away, ET44 is best for stock suspension/alignment settings

Thanks for the pics. But couldn't you accomplish lower ETs by just using a spacer in the rear? A wide slick would seem to fit better in a ET44 wheel than 14mm offset to the outside

[fanatic1]

Originally Posted by SYT_Shadow

Thanks for the pics. But couldn't you accomplish lower ETs by just using a spacer in the rear? A wide slick would seem to fit better in a ET44 wheel than 14mm offset to the outside

Was thinking the same thing, a 10mm rear spacer would’ve likely cleared the inside and probably been good on the outside as well. I guess that would be effective ET34, close enough to a ET30 for me to give it a go and ET30 = less spacer up front - rotatable is must for me

[SYT_Shadow]

Originally Posted by fanatic1

Was thinking the same thing, a 10mm rear spacer would’ve likely cleared the inside and probably been good on the outside as well. I guess that would be effective ET34, close enough to a ET30 for me to give it a go and ET30 = less spacer up front - rotatable is must for me

You think you could have fit a 10mm spacer and still been good on the outside?

[fanatic1]

Originally Posted by SYT_Shadow

You think you could have fit a 10mm spacer and still been good on the outside?

Pretty sure, yes on 10mm. Gonna try to fit effective 14mm spacer to see if ET30 will clear, gonna be close.

[SYT_Shadow]

Originally Posted by fanatic1

Pretty sure, yes on 10mm. Gonna try to fit effective 14mm spacer to see if ET30 will clear, gonna be close.

thank you

[fanatic1]

Suspense builds for Saturday, will see if Porsche club event last weekend makes a difference. Starting to like this track as seat time here increases. Can’t say I’m new to SoCal tracks any longer.

[SYT_Shadow]

Originally Posted by fanatic1

Suspense builds for Saturday, will see if Porsche club event last weekend makes a difference. Starting to like this track as seat time here increases. Can’t say I’m new to SoCal tracks any longer.

Do you have that spacer in the rear?

[RSXDC5]

Originally Posted by fanatic1

Pretty sure, yes on 10mm. Gonna try to fit effective 14mm spacer to see if ET30 will clear, gonna be close.

I think a crucial piece of info is that you were trying to fit a 325/30 on an 18x11 +44 @ -2.7 rear camber. Comparing against my personal setup, you run -0.7 rear camber more than me, why not dial out some rear camber and get a wider rear wheel (the wider rear should help with sidewall deflection)...then apply a small spacer if needed.

Also of note, the 18x11 +30 gt4 wheel works in the rear because bmw was forced to compensate for crap fitment by reducing all suspension arm length by around an inch. My f80 friend with Ohlins ttx shared his original gt4 wheel fitment (315/30/18 r888r) pics with me and it literally pokes out by an inch or so...he had to get the e90 version of his SPL arms to allow fitment.

[fanatic1]

Originally Posted by RSXDC5

I think a crucial piece of info is that you were trying to fit a 325/30 on an 18x11 +44 @ -2.7 rear camber. Comparing against my personal setup, you run -0.7 rear camber more than me, why not dial out some rear camber and get a wider rear wheel (the wider rear should help with sidewall deflection)...then apply a small spacer if needed.

Also of note, the 18x11 +30 gt4 wheel works in the rear because bmw was forced to compensate for crap fitment by reducing all suspension arm length by around an inch. My f80 friend with Ohlins ttx shared his original gt4 wheel fitment (315/30/18 r888r) pics with me and it literally pokes out by an inch or so...he had to get the e90 version of his SPL arms to allow fitment.

Will try and get pics this weekend, but reasonably sure it (18x11 ET30) will fit my car with stock suspension bits with track alignment, could be wrong

[fanatic1]

Originally Posted by SYT_Shadow

Do you have that spacer in the rear?

Not yet, forgot I moved Apex ET44 to storage

[fanatic1]

18x11 ET30 with Yoko 295/30/18

It does fit, but it will rub under full compression on this F80 - which has similar alignment specs to mine in the rear

[SYT_Shadow]

Originally Posted by fanatic1

18x11 ET30 with Yoko 295/30/18

It does fit, but it will rub under full compression on this F80 - which has similar alignment specs to mine in the rear

So you'd be better served with ET44 it seems

[fanatic1]

Originally Posted by SYT_Shadow

So you'd be better served with ET44 it seems

Not too excited about the spacer required in the front to rotate those ET44, but yes in rear with a smallish spacer

Probably ideal would be something approximately ET35 as ET30 barely rubs

[Gomeler]

What are your concerns over the spacer? Only ask as I've got like 10 hours on the track with a 25mm spacer up front. Besides the aforementioned front scrub radius and the expectation that there might be a little more tire wear up front, the car seems to handle quite nicely with the benefit of tire rotations being an option.

I do notice that my fronts wear slightly faster than the rears, but I wasn't too surprised by this. 3600lb car and two heavy braking zones is asking a lot of the fronts, in addition to normal cornering duty.

[SYT_Shadow]

Originally Posted by Gomeler

What are your concerns over the spacer? Only ask as I've got like 10 hours on the track with a 25mm spacer up front. Besides the aforementioned front scrub radius and the expectation that there might be a little more tire wear up front, the car seems to handle quite nicely with the benefit of tire rotations being an option.

I do notice that my fronts wear slightly faster than the rears, but I wasn't too surprised by this. 3600lb car and two heavy braking zones is asking a lot of the fronts, in addition to normal cornering duty.

Yup, all of these cars wear fronts more than rears. That's why square tire/wheel setups are so important.

Remember the GT4 runs 25mm spacer up front without issues

[fanatic1]

Originally Posted by Gomeler

What are your concerns over the spacer? Only ask as I've got like 10 hours on the track with a 25mm spacer up front. Besides the aforementioned front scrub radius and the expectation that there might be a little more tire wear up front, the car seems to handle quite nicely with the benefit of tire rotations being an option.

I do notice that my fronts wear slightly faster than the rears, but I wasn't too surprised by this. 3600lb car and two heavy braking zones is asking a lot of the fronts, in addition to normal cornering duty.

Probably unfounded, but have broken several studs, but never on front axle with spacers.

[erictrainer]

Originally Posted by fanatic1

18x11 ET30 with Yoko 295/30/18

It does fit, but it will rub under full compression on this F80 - which has similar alignment specs to mine in the rear

FWIW The M4 has a little bit more room in the rear than the M3. Might not be an issue at all.

[SYT_Shadow]

Originally Posted by erictrainer

FWIW The M4 has a little bit more room in the rear than the M3. Might not be an issue at all.

I thought it was the other way around, 3mm more on the M3