[fortythirtyfive]

We finally have a more aggressive diffuser design for the 4 Series that doesn't loose the middle slats..

Bought it through Maxton with a code for around £170




The plan is to carbon skin the middle with a carbon herringbone weave, then split paint it like I used to have on my M Performance diffuser.



A lot of Maxton's designs are quite rounded looking which has put me off buying their products before, however this isn't too bad, there's some edges on a lot of areas that are sharper than their normal stuff so I took the gamble.

Fitment is a solid 8/10 - improvements would be the actual mounting areas, they seem to have designed it to push on and be left, that doesn't fill me with confidence once air builds up though so I'm going to drill some holes where the original mounting points were.

The quality seems pretty good, especially if you just want gloss black. Personally that's not my taste though so I won't be keeping it on until I've finished wrapping and painting it.

If you've ever seen their 1 Series diffusers then you'll know what to expect, it's pretty much that exact design which they borrowed from the F90.

[SimonBMW1]

Looks good. Any fitament issues. Usually you have to use heat gun etc on aftermarkets.
Your other parts on bumper look cool. Guessing its bespoke to you

[fortythirtyfive]

Originally Posted by SimonBMW1

Looks good. Any fitament issues. Usually you have to use heat gun etc on aftermarkets.
Your other parts on bumper look cool. Guessing its bespoke to you

It's made from a relatively stiff plastic but has a nice amount of flex where needed to form around the bumper, the tabs all slotted into the OEM spots.

Took some more photos today:







I have heard some horrors about diffusers and fitment before however this fitted perfectly really.

Whilst I'm not normally a big fan of Maxton's designs there is one thing you can bag with them and that's quality fitment, they're quite a big company now with in-house designers who model products on actual cars, just wish they would offer carbon products for the BMW range like they do on other cars, it would save me some hassle of carbon skinning it lol.

[fortythirtyfive]

Originally Posted by SimonBMW1

Looks good. Any fitament issues. Usually you have to use heat gun etc on aftermarkets.
Your other parts on bumper look cool. Guessing its bespoke to you

Oh and yeah, I started making rear extension pieces a long while ago, this was the final design I settled on. It's essentially the F82 kit but modelled to flow with our rear bumpers.

As I wasn't hitting MOQ a one off build cost was around £400.. sadly the factory I used went on to use the design and are now selling it on Aliexpress. I can't fully recall what it was listed as but they had a yellow F30 on the listing photo if that helps, I think they were pricing them at around £280. Fitment isn't good though as it was only ever a concept, you have to do some drilling into your bumper and a bit of cutting into the carbon piece.

[fortythirtyfive]

Got some time today to make a rough edit of how it'll look painted..

[eff32fl]

Looks pretty snazzy! I really like the more aggressive look. If I can get someone to lay carbon over it I'm definitely interested in buying one. The existing M Performance and clones aren't aggressive enough imo.

This is the link?

https://maxtondesign.com/product-eng-20407-Rear-Valance-BMW-4-Coupe-Gran-Coupe-M-Pack-F32-F36-Version-with-exhaust-on-both-sides.html?country=1143020186

[fortythirtyfive]

Originally Posted by eff32fl

Looks pretty snazzy! I really like the more aggressive look. If I can get someone to lay carbon over it I'm definitely interested in buying one. The existing M Performance and clones aren't aggressive enough imo.

This is the link?

https://maxtondesign.com/product-eng...try=1143020186

That's the one, they do actually make quality carbon pieces now but unfortunately this isn't one they offer it on. I think they had a big investment over the past 1-2 years as they were originally just a small depot near me, they would only sell plastic and "carbon look" products, now they've got huge operations around Europe with enclave facilities.

It's definitely possible though, I'm planning on just doing the middle but there's definitely plenty of people offering carbon skinning services in the US.

[Oksamit78]

Originally Posted by fortythirtyfive

...but there's definitely plenty of people offering carbon skinning services in the US.

If you have the contacts of those (US vendors) readily available, do you mind sharing (or DM)? I have a "project" in mind, but can't justify CF skinning the parts at home. Thanks!

[eff32fl]

Originally Posted by Oksamit78

If you have the contacts of those (US vendors) readily available, do you mind sharing (or DM)? I have a "project" in mind, but can't justify CF skinning the parts at home. Thanks!

Ocarbon.com is one in the USA and they do really good work looking at their IG. They have various types and colors available.

I also asked Maxton if this diffuser was available in carbon hoping they'd be willing to do a custom job for a fee but no dice.

[fortythirtyfive]

Originally Posted by eff32fl

Ocarbon.com is one in the USA and they do really good work looking at their IG. They have various types and colors available.

I also asked Maxton if this diffuser was available in carbon hoping they'd be willing to do a custom job for a fee but no dice.

I tried starting the middle last night but hit a slight issue, because I'm using herringbone weave the fabric is pretty rigid as it meets in the middle.. I was also totally out of vacuum bagging sealant which I didn't realise until I had begun

I did think of a better plan later on though, the underside has a really clean negative mold, I'm hoping to use release agent on it and create an impression that I can lift out and stick on the other side.

[fortythirtyfive]

Annoyingly I didn't spot the centre line wiggled near the bottom, I kept correcting it earlier on but I guess each adjustment on the sides threw it out again.

It's in with mould release so hopefully I can just trim the sides down, bond it on and then get this sucker painted finally!

[eff32fl]

Originally Posted by fortythirtyfive

Annoyingly I didn't spot the centre line wiggled near the bottom, I kept correcting it earlier on but I guess each adjustment on the sides threw it out again.

It's in with mould release so hopefully I can just trim the sides down, bond it on and then get this sucker painted finally!

Are you just skinning the outside of the diffuser?

[fortythirtyfive]

Originally Posted by eff32fl

Are you just skinning the outside of the diffuser?

Just the middle bit, I wanna keep the paint scheme I had before with only the middle being black; except it'll be carbon this time.

[Oksamit78]

Originally Posted by fortythirtyfive

I did think of a better plan later on though, the underside has a really clean negative mold, I'm hoping to use release agent on it and create an impression that I can lift out and stick on the other side.

As always - amazing job with CF.

However, I have a question... You are making the skin using a back side as negative mold, but how are you planning to stick the skin to the outside without fit-up issues? All the ribs/fangs are now "reduced" by being offset uniformly inwards off the mold surface. Additionally, the diffuser is made out of material that has thickness to it... I'd imagine 1.5 - 2 mm, so all the surfaces on the back side are already offset inwards (including the ribs/fangs)...

To further explain, I've tried to sketch an example of horizontal section (parallel to the ground) using a 2 mm thickness of diffuser and 1 mm of skin made on inside. See images:

Skinning


Skinning zoomed on Middle rib:


CF skin shifted to the outside


Zoomed on middle rib


Zoomed on other rib


All geometry features were exaggerated to show possible interference... I don't imagine the fairly rigid skin could be stretched or can it be stretched with heat?

The skin you are creating would work if there were no ribs in the diffuser, imho.

With your skill set in CF skinning I'd reconsider and do attempt the skinning on outside surface, to be honest.

[fortythirtyfive]

Originally Posted by Oksamit78

As always - amazing job with CF.

However, I have a question... You are making the skin using a back side as negative mold, but how are you planning to stick the skin to the outside without fit-up issues? All the ribs/fangs are now "reduced" by being offset uniformly inwards off the mold surface. Additionally, the diffuser is made out of material that has thickness to it... I'd imagine 1.5 - 2 mm, so all the surfaces on the back side are already offset inwards (including the ribs/fangs)...

To further explain, I've tried to sketch an example of horizontal section (parallel to the ground) using a 2 mm thickness of diffuser and 1 mm of skin made on inside. See images:

All geometry features were exaggerated to show possible interference... I don't imagine the fairly rigid skin could be stretched or can it be stretched with heat?

The skin you are creating would work if there were no ribs in the diffuser, imho.

With your skill set in CF skinning I'd reconsider and do attempt the skinning on outside surface, to be honest.

Yeah this was something I took into account when making the plan, I didn't reinforce it with anymore fabric other than the cosmetic layer to keep it paper thin, by the time I add a composite bonding agent it'll have made it stand off a little, I was banking on the fact it could bend almost in so plenty of flex to fit, those those ribs are proving to be an absolute nightmare though, the gaps are far too tight for one piece; the tension pulls the fabric out creating a void each time.

The new plan is to make it using one piece of fabric for the flat side and the ribs will have to be secondary cuts of fabric laid in before vacuum forming it, basically just how you would with pre-preg.

As it'll be thicker this time I'll definitely be going from the front. I have also noticed how much brighter the carbon is when its been squashed in a mould (the filament strands lay flatter with less excess resin) so now I'm considering making a top side mould for my hood and starting it again I was having some resin issues before and it would look HD in-comparison to what it is right now.. it's just SO much sanding and like $450 in materials down the drain.

Hand laid:


From a mould:


Can't help but think I often shoot myself in the foot haha

[Oksamit78]

Originally Posted by fortythirtyfive

From a mould:


Can't help but think I often shoot myself in the foot haha

Yeah, the HD of strands out of mold is very noticeable compared to the skinning from outside...
So, now all you need - the stamping die for GTS hood from BMW factory/supplier and you are good to go to mass produce hood skin inserts.

1. How do you plan to produce a fairly rigid top side mould off the GTS hood?
2. The skin then would be attached to the hood using epoxy and edges be "blended in" with body filler? I know it wouldn't be nice to the eye, but producing a CF skin overlay that is glue able to the hood without any additional body work could be a cool thing to offer for purchase.

[fortythirtyfive]

Originally Posted by Oksamit78

Yeah, the HD of strands out of mold is very noticeable compared to the skinning from outside...
So, now all you need - the stamping die for GTS hood from BMW factory/supplier and you are good to go to mass produce hood skin inserts.

1. How do you plan to produce a fairly rigid top side mould off the GTS hood?
2. The skin then would be attached to the hood using epoxy and edges be "blended in" with body filler? I know it wouldn't be nice to the eye, but producing a CF skin overlay that is glue able to the hood without any additional body work could be a cool thing to offer for purchase.

For the purpose of what I want to achieve with mine I'm hoping to replicate the mould just by creating an extra top layer, then coating the underside in release agent and sandwiching the actual carbon layer in-between.

For anyone with the facility and space to do so they could definitely do it! A guy who goes by the name of Dan Pritchard has done it on his Porsche. He's even made custom bumpers and diffusers using spray foam for modelling.





As for rigidity it's just a case of layering heavier gsm fabrics or even throwing plain weave in there, it's a much stiffer weave compared to twill.

Adhering it would be a job for something like Methacrylate adhesive. As you mentioned though the edges want to be kept thin or at least tapered by a bodyshop for blending. The only other thing to watch out for when bonding carbon to aluminium is galvanic corrosion, even when sealed the moisture from heat cycling will eventually attack the two ruining the finish, you can either lay down fibreglass before your carbon fabric to insulate any reaction or put down a good enough layer of resin before your fabric touches the metal surface, the latter would need to cure slightly so that it forms a barrier.

[tumorrow]

Nice diffuser but Where did you get those rear carbon bumper canards?

[Oksamit78]

These look similar:
https://www.aliexpress.com/item/1005...Cquery_from%3A

[fortythirtyfive]

Yep thats pretty much them - I had a design file that I was playing with and I ended up giving it up to a factory in China as they were going to build some carbon ones for me, instead they ghosted me and as I presumed began making them for everyone lol.

I bought a set through a friend as they refused to deal with me having done a runner lol, they don't actually use the finished design though so if you do buy a set through them you'll need drill new holes in both the carbon and bumper to mount them, then you'll need to create some recesses for the existing bumper screws to sit inside of; otherwise you'll have a 4mm gap between the trim and underside of your bumper.

Oh and the resin system they're using sucks, it's super cloudy leaving the carbon with a blue tint. It's impregnated through the fabric too so you can't just sand it off and re-lacquer it.

Doesn't look like they sold many though so I very much doubt they'll correct any of the design / material issues they have - if you really want a set go for them, but you'll need to hack them up to make them fit and the finish was enough for me to bin my set.

[tumorrow]

Originally Posted by fortythirtyfive

Yep thats pretty much them - I had a design file that I was playing with and I ended up giving it up to a factory in China as they were going to build some carbon ones for me, instead they ghosted me and as I presumed began making them for everyone lol.

I bought a set through a friend as they refused to deal with me having done a runner lol, they don't actually use the finished design though so if you do buy a set through them you'll need drill new holes in both the carbon and bumper to mount them, then you'll need to create some recesses for the existing bumper screws to sit inside of; otherwise you'll have a 4mm gap between the trim and underside of your bumper.

Oh and the resin system they're using sucks, it's super cloudy leaving the carbon with a blue tint. It's impregnated through the fabric too so you can't just sand it off and re-lacquer it.

Doesn't look like they sold many though so I very much doubt they'll correct any of the design / material issues they have - if you really want a set go for them, but you'll need to hack them up to make them fit and the finish was enough for me to bin my set.

How much for your exact ones? They look sick hahaha. Did you do them yourself, if so they’re nice.

[fortythirtyfive]

Originally Posted by tumorrow

How much for your exact ones? They look sick hahaha. Did you do them yourself, if so they’re nice.

The ones I have I paid £300 in total after shipping and taxes, they'll be the same though as I'm fairly sure my friend bought them from the same reseller.