17" ARC8 on Z4M

[philipw]

Hi All,

Looking to pickup a set of Apex ARC8's for my coupe except the set-up I want is not very common so looking for your advice. The set-up I want is pictured below and is a square set-up with 255 x 40 x 17 fitted to 17 x 9 x et30. Must haves are a concave look on both front/rear and to keep the front/rear track width differential within 10mm preferably (currently using 12mm front spacers to achieve on the stock wheels). For camber, I am running -1.65 on the front & -1 on the rear with neutral toe all round.

From checking on willtheyfit, I have found out the following

Front with 255 x 40 x 17
The track width on the front will increase by 24.7mm to 1510.7mm Drop of 12mm & 0.7mm closer to strut.
Rear with 255 x 40 x 17
Track width will increase by 2mm to 1518mm. Drop of 12.7mm and same position from strut

I figured it would be a good idea to test fit the rear 224M wheel on the front as it has same offset and width as the apex wheel. Caliper clearance looked good and the top of the wheel did not protrude outside of the fender. I think I can get away with it without needing to buy camber plates, thoughts?

 

[mr wilks]

Look at the second pic down, I can't see how the outer edge of front tyre won't foul the arch liner on any spirited driving that involves a bend & even reasonable speed , throw in some compression & it's goodnight Vienna for the liners.
245 on front would help

 

[philipw]

Look at the second pic down, I can't see how the outer edge of front tyre won't foul the arch liner on any spirited driving that involves a bend & even reasonable speed , throw in some compression & it's goodnight Vienna for the liners.
245 on front would help

Yes good point, I certainly don't want that. I had hoped that the reduction in overall diameter would have helped to prevent this.

 

[mr wilks]

Look at the second pic down, I can't see how the outer edge of front tyre won't foul the arch liner on any spirited driving that involves a bend & even reasonable speed , throw in some compression & it's goodnight Vienna for the liners.
245 on front would help

Yes good point, I certainly don't want that. I had hoped that the reduction in overall diameter would have helped to prevent this.

Worth noting that the proposed 255 40 17 9j et30 would have approx 10mm more clearance than the rear 224 does with 255 40 18 on , its in your favour but even then i wouldn't expect to avoid rub at certain times of driving

 

[TomK]

https://support.apexraceparts.com/hc/en-us/articles/360003718253-E85-86-Z4M-Wheel-Tire-Fitment-Guide

 

[mmm-five]

Would a 17" wheel clear the front brakes?

 

[TomK]

Of course, see above. Loads run them.

 

[mr wilks]

Would a 17" wheel clear the front brakes?

Yep I fitted a set of 17inch momo arrows to a ZM as a temporary set.
Cleared calipers no probs

 

[BTZ461]

Would a 17" wheel clear the front brakes?

From memory 17 inch diameter, depending on ET, MAY preclude going bananas in the BBK kit department further down the track (forgive the pun). Apex ARC8 in 17 inch give excellent bang for the buck on our Z cars. And gives you the ability to muck about with all sorts of tyre sizings, so a comprise solution is more readily available.

 

[TomK]

Would a 17" wheel clear the front brakes?

From memory 17 inch diameter, depending on ET, MAY preclude going bananas in the BBK kit department further down the track (forgive the pun). Apex ARC8 in 17 inch give excellent bang for the buck on our Z cars. And gives you the ability to muck about with all sorts of tyre sizings, so a comprise solution is more readily available.

Assuming et and width being the same a 17"arc 8 would have no more trouble than an 18" with pretty much all bbks on the market for the z4m I'd say, the barrel size is huge compared to say a 224 oe M wheel.
A 17" with my 368mm discs might be tight though, may work, not sure anyone's tried it?

 

[BTZ461]

Oouff nice. We are fitting 345mmx28 drilled CSL discs and the bigger 335 calipers to our humble Si coupe, behind a set of Apex Arc8's in 18x9F and 18x10R. Painted the calipers M blue. Just got to get ontuit soon......and hoping for the same effect ie fill the gap behind the wheel.

 

[philipw]

Thanks all for the feedback. One of my main concerns was with the brake caliper clearance since I use aftermarket items. The barrel of the stock front wheel appears to curve inwards when approaching the spokes however the rear wheel does not have this issue (see photos). From what I have seen from photos the Apex wheels seem to maintain a flat barrel section to as close as possible to the spokes so should not be an issue. Thanks Tom for the link, seems it is possible without too many modifications, I will contact Apex to get their guidance.

 

[philipw]

Well dang, Apex say to avoid the 17s, just no way to be sure that the caliper will clear them. As the photo shows, only 10mm clearance with the OEM rear wheels from caliper to barrel.

Now looking at 18 x 9 x et30 with 245 x 40 x 18 and 18 x 9.5 x et30 with 265 x 35 x 18. Both are profile 3 with the concave look and the track width differential is still reasonable at <15mm.

 

[TomK]

I'm pretty surprised tbh, I suspect they are just being overly cautious which is fair enough.
I would take a measurement of the barrel on your 224 where caliper clearance is an issue and ask them to provide the corresponding dimension of the arc 8.
My original ap caliper on 356mm discs was very tight (a few mm) with a 224 barrel, with the arc 8 I would say there was at least 2or 3 cm maybe more.

 

[Warming]

Superb looking wheels! Seems to be very popular in the US. Hopefully more sets will make it over here soon.
I would go for less than 9J on the fronts (just from an aesthetic view), but it's up to you on how wide a tyre you intended to have.

 

[philipw]

So finally an update. I tried everything I could to find a set of 17s that would fit over the DB9 calipers but after submitting a drawing of them to Apex, there was no chance that they would fit within the barrel.

So I bought a set of 18s last November and just got round to fitting them today. Couldn't be happier with how they fit, did not have to go too extreme with front camber to make them fit with just 2 degrees up front. I think a 245 front tyre would clear the wheel liners but did not want to chance it at the time. Planning to put a set of 5mm spacers on the rear as the front track width is currently 20mm wider than the rear.

For alignment, I always go with toe out on the front for that crisp turn in and I have to say with cup 2 tyres, it is next level! Rear camber is 1.50 thanks to a set of ECS camber arms with a small amount of toe in as straight line high speed stability is compromised a bit with toe out on the front.

 

[Ed Doe]

I was just about to post my wheel specs for comparison - although 8.5j front I'm contemplating spacers to increase the track, and have no issues with arch liner rubbing currently.

But now I've read to the end I see you've sorted it anyway - car looks absolutely fab! I assume you track it based on the geo, square setup and bbk?

Pic of mine - because Apex wheels are the best :lol:

 

[philipw]

Thanks Ed. I remember seeing your car last year at Redish and was impressed with the EC9 design but decided to go with the more common ARC8 style.

I went for 18x9" ET30 & 18x9.5" ET35 to get the concave look front & rear with 235/40/18 & 265/35/18.
Front track 1535mm & rear is 1519mm without spacers. Might leave it without rear spacers to leave the offset as the turn in is awesome but does highlight the limits of the Bilstein B12 suspension it has. When rapidly changing direction, roll is noticeable so an H&R anti roll bar kit & KW V3 will have to be the next mods!

Yep I have been using it for track work for the past couple of years, very simple modifications (B12, BBK with RSL29, vibra technics mounts, Gruppe M, RTAB limiters, ECS rear camber arms) so far as mods are expensive and preventative maintenance must come first! I found that sorting out the spring rates and fixing the geometry yielded the biggest benefits, standard geometry is set-up for understeer from my experience.

 

[Ed Doe]

Thanks Ed. I remember seeing your car last year at Redish and was impressed with the EC9 design but decided to go with the more common ARC8 style.

I went for 18x9" ET30 & 18x9.5" ET35 to get the concave look front & rear with 235/40/18 & 265/35/18.
Front track 1535mm & rear is 1519mm without spacers. Might leave it without rear spacers to leave the offset as the turn in is awesome but does highlight the limits of the Bilstein B12 suspension it has. When rapidly changing direction, roll is noticeable so an H&R anti roll bar kit & KW V3 will have to be the next mods!

Yep I have been using it for track work for the past couple of years, very simple modifications (B12, BBK with RSL29, vibra technics mounts, Gruppe M, RTAB limiters, ECS rear camber arms) so far as mods are expensive and preventative maintenance must come first! I found that sorting out the spring rates and fixing the geometry yielded the biggest benefits, standard geometry is set-up for understeer from my experience.

Ah yes, that would have been whilst my engine was in bits after the last trackday.... :lol:

I can't really complain as a lot of the mods on my car were done before I bought it, but I do wish the fronts were wider, the 8.5j just doesn't have enough concavity and I definitely reckon a 9j would fit (I'm sure the us boys are running 9j fronts with a bit of camber which again isn't an issue for me either!) Always loved the arc-8s and probably would have bought those out of choice (in bronze - I reckon they'd look ace on carbon Black!), but that being said, in the metal the ec-7s have grown on me.

The previous owners seem to have all spent small fortunes with centre gravity motorsport getting the car corner weighted and geo setup. To my tastes though there's still a little too much push, so I'm hoping to spend some time eventually finessing this aspect... Time is at a premium though at the moment with a 12week old baby now, so in the grand scheme I'm just grateful for the odd drive right now :lol:

You planning any trackdays this year? I'm hoping to get up to donny for an evening slot at some point late summer, subject to availability etc. Might pop onto a cheeky brands hatch day at some point too, again time permitting!

 

[philipw]

Thanks Ed. I remember seeing your car last year at Redish and was impressed with the EC9 design but decided to go with the more common ARC8 style.

I went for 18x9" ET30 & 18x9.5" ET35 to get the concave look front & rear with 235/40/18 & 265/35/18.
Front track 1535mm & rear is 1519mm without spacers. Might leave it without rear spacers to leave the offset as the turn in is awesome but does highlight the limits of the Bilstein B12 suspension it has. When rapidly changing direction, roll is noticeable so an H&R anti roll bar kit & KW V3 will have to be the next mods!

Yep I have been using it for track work for the past couple of years, very simple modifications (B12, BBK with RSL29, vibra technics mounts, Gruppe M, RTAB limiters, ECS rear camber arms) so far as mods are expensive and preventative maintenance must come first! I found that sorting out the spring rates and fixing the geometry yielded the biggest benefits, standard geometry is set-up for understeer from my experience.

Ah yes, that would have been whilst my engine was in bits after the last trackday.... :lol:

I can't really complain as a lot of the mods on my car were done before I bought it, but I do wish the fronts were wider, the 8.5j just doesn't have enough concavity and I definitely reckon a 9j would fit (I'm sure the us boys are running 9j fronts with a bit of camber which again isn't an issue for me either!) Always loved the arc-8s and probably would have bought those out of choice (in bronze - I reckon they'd look ace on carbon Black!), but that being said, in the metal the ec-7s have grown on me.

The previous owners seem to have all spent small fortunes with centre gravity motorsport getting the car corner weighted and geo setup. To my tastes though there's still a little too much push, so I'm hoping to spend some time eventually finessing this aspect... Time is at a premium though at the moment with a 12week old baby now, so in the grand scheme I'm just grateful for the odd drive right now :lol:

You planning any trackdays this year? I'm hoping to get up to donny for an evening slot at some point late summer, subject to availability etc. Might pop onto a cheeky brands hatch day at some point too, again time permitting!

Oh dear, that is unfortunate! The top end is my next fear but if it goes then its an excuse to fit Shrick cams and maybe a carbon air box should funds stretch!

So far so good with the 9J on front, no rubbing with road driving but track use will highlight any issues. I was very tempted with the matte Bronze colour but wasn't brave enough to buy them as the penalty for not liking them would be severe! Hope you manage to get out on track at some point this year, I have Thruxton booked for June so looking forward to seeing how it drives with the lighter rims