Recently got a 2021 and heres a list of the parts off my 2018 that fit and those that did not.

Parts that fit
-BC coilovers
-Tsudo axelback, however I did have to change the tips as I had quad tips and they would not fit the new cutout

Parts that didn't fit
- Side skirts
- Window visors
- Diffuser
- Roof spoiler - the curvature of the back window is different

Not much but hopefully it helps anyone looking to use parts from a previous 3IS

 

That's more exterior changes than I thought. Good to know!

 

So exhaust fits..... time to start looking

 

Is a 2015 suspension/exhaust compatible with an 18? Thus making it compatible with 21?

 

The cutout in the diffuser with the only issue.
The 2015 catback and axleback will bolt up to a 2018...diffuser fitment pending what exhaust it is and what diffuser it is.
If the member above got the exhaust to fit the 2021, then it would also be compatible...once again, diffuser fitment pending.

 

So you had no issues fitting a 2018 Axel back onto your 350 other than the fact that you originally had a quad exhaust tip?

Im thinking of transfering over my whole catback from a 2017 IS300 to my new 2021 IS300, not quad tips so hopefully it works out!

 

This would probably work as long as the cut-outs in the rear bumper/diffuser area can accommodate your exhaust tips.

This makes sense, as the powertrains appear to be virtually no different from before.

 

Hopefully we can continue to piece together what fits on the new platform. I've been searching for brake pads, an intake, and other bits. No one seems to have any clue as to what fits what. I immediately upgraded tires on my 2021, and have been waiting patiently since!

I've spoken directly to Tom's and they're currently developing aero and brake parts for the 2021. Spoke with Project Mu, Endless, and other JDM brands and they're also still in development.

Definitely interested to see what parts can carry over from the older models.

 

Yep powertrain, suspension, and body-in-white appear to be all the same (Lexus confirmed that last one somewhere) as well as I confirmed it through technical docs. suspension may have got some parts bin bushing swaps IIRC but nothing to write home about.

The body in white already received 2-3 revisions, latest in 2017 or 18, so I can see why Lexus would not want to spend any more money on that.

the exterior metal work should all be substantially different. if i'm not mistaken, the only parts on the outside that are the same are probably all the glass except the rear quarters. i havent looked at the IS too closely though. could be wrong.

in fact i've only ever seen two on the streets... in socal!

would be pretty neat to see a new IS based on TNGA.

 

This post was super helpful! Its nice to know that the suspension from 18+ IS350 would fit a 21'. My only question is do you have the RWD IS350 or AWD? Apparently that matters?

 

I just installed a 2014+ invidia Q300
axleback on my 2021 is 350. No fitment issues at all.

 

I was wondering if any of you guys think headers from 2017 would fit in the 2021 one since its the same powertrain?

 

The 2017 has the 2GR-FSE, whereas the 2018+ models have the 2GR-FKS, which has some differences in the exhaust manifold (namely, the manifold is integrated into the cylinder head). Does anybody know if this would affect header compatibility? I have done a little Googling and have not been able to find headers that are compatible across all the years - for example, RR Racing specifically lists their PPE headers as fitting 2014-2017 models.