Hi,

I'm about to get an E46 325i that came with 18 inch BMW 135 style rims. The tyres are at the end of their lifespan.

I plan to downsize to 17 inch as I believe that the 325i originally came with 16 or 17 inch depending on the package from BMW, and also save on long term cost for cheaper tyres due to its smaller size. Plan to get PS4.

I believe the stock setup is front 17x7.5 ET41 225/45 R17, rear 17x8.5 ET50 245/40 R17. Main priority is comfortable enough for a daily driver, as well as saving some cost from tyre changes.

I have several questions:

1. How big is the difference in terms of comfort and handling when downsizing from 18 to 17 inch? The general consensus is less handling but more comfort, but to what extent in terms of real world experience.
Pretty noticeable difference because you'd increase your tire sidewall by about 1-1.2cm, assuming your current 18 tire has about the same rolling diameter as your target 17 size. As for handling sacrifice, there's a lot of misconception that the thinner the tires the better the handling which is not entirely true! Past certain points, too thin profile actually makes the handling more nervous especially in the wet and on uneven surfaces. You need some level of flexing from the tires to absorb uneven surfaces and allows the tires to dig in into the asphalt. For me I feel the best to get good handling performance is around 9.8-10.7cm sidewall height. This range also still gives reasonable comfort for daily cars. The sizes you mentioned for your 17 do fall in this range so I believe those are perfect.

2. If I were to get new rims, do they come only in 1 same size for all 4 pieces or do they come staggered already?
Can be same or staggered

3. Do I need to follow the respective 17x7.5 and 17x8.5 sizes or can all 4 wheels be the same at 17x7.5 for example. If they only come in the same sizes for all 4 rims, can I still put staggered tyre sizes (225/45 front and 245/40 rear) and won't face any issues?
You can use all same up to 17x8.5. Can use all same tire size 225/45/17 or 245/40/17. 245/40/17 is about 3mm thinner profile though, so will be slightly harder but should give better handling response. You can also use staggered tire sizes on equal rim sizes provided still with the recommended fitment range for the tires. For example 225 width can fit 7.5-8.5jj rims while 245 can fit 8-9jj rims.

4. Any alternative wheel/tyre sizes recommendation?
Same explanation as no.3 above. Alternative tire size you may fit 235/45/17 which is 0.5cm taller than 225/45/17 so will give even more comfort but tire price a bit higher

5. Are there any good shops/recommendations around KL? So far I've seen some recommendations for KeanLeeHin and King of Rims. Is it better for me to get the new rims and tyres first, then only sell the 18 inch rims myself or do they accept trade-ins at a good price point?
I don't have specifically recommended shops coz usually I just browse in mudah or facebook whenever selling the models I am want. Trade in can but usually they will low ball your rims. Better try sell yourself if you can.

6. I've seen some recommendations for brands like Advanti, Konig and Lenso; cheap/affordable but durable. I believe my current rims should be able to cover the cost of getting these new ones right? Any particular recommendation for brands or models for my car?
Depends on what rims you have. If fake then very cheap, 18 can be just around 1k or less. If original BMW, then can fetch good price, maybe even more than new Advanti/Konig/Lenso.

Feel free to provide more feedback or advice as I'm very inexperienced in regards to this. Thanks for all the help!

Thanks a lot for your feedback as usual!

Btw, what's your personal opinion on staggered vs square setups?

After asking around from wheel/rim shops, I realised that it's not as easy to find the correct fitment for 17 inch. They don't have any Advanti/Lenso/Konig rims which has pcd 5x120 for 17".

The first one seems decent, but will ET34 have any issues with fitment/rubbing?

Is it better to order online to ship from overseas to get original Konig/Advanti/Motegi?

What about BMW Taiwan replicas? Feels like this route is quite risky.

Nope, do not know the current offset. But from searching online, the safe minimum should be ET35++.

I'll probably be getting used original BMW rims, not sure how to verify if it's real originals but it says made in Austria on the back. Willing to spend extra for new original OEMs, but every shop seems to not have PCD 5x120 for 17 inch. Can't find much on mudah and Facebook market either. There's one selling for 1.7k but no response from seller.

Searched for online rim ships that ship overseas but Konig Rennflow is out of stock and the estimated delivery arrival is at least a month away.

Any other reputable brand suggestions besides Konig, Advanti, and Lenso? Preferably more spokes design.