[Resjudicata]

Originally Posted by Jenner

I'm running 21"s on my M8 Convertible. I did the wheels/tires first then lowered on H&R after. So I can speak to both.

First off anything more than 21" and 30 profile is insane. 22" and 25 just DON'T do it. I don't care how good it might look its a heavy car and you are going to ruin the ride and probably end up with bend rims and flat tires with the smallest potholes.

The ride quality changes MUCH more with smaller sidewall than with the lowering springs. Stock springs and stock tires the car was TOO soft for me and I ran in sport plus suspension all the time. Adding the lowering springs didn't change the ride quality for the worse, but it did make it so that the 3 suspension modes actually feel different now.

If your roads are shit up there then I wouldn't do it. It's a heavy car and the stiffness of the 30 size tire profile (even when based on the width of wide tires) really takes out what I call a "suspension element" which is the flex in the sidewall of the tire.

That said the huge fat stock sidewall makes the M8 look much less aggressive and much more old man (to me). The 21" with the 30 looks like a sports car. If you want a true GT car that you can glide along the highway in for hours upon hours keep the stock size sidewalls. If you want a firmer, slightly harsher ride, more aggressive look with less "floating" feeling then go to the 21s. I prefer my cars to be stiffer so for me it works but again the jump from 35 to 30 was much harsher than the jump from stock springs to H&R springs.

Also note you cannot easily put higher than 30 sidewalls on the 21s because the AWD system will get out of sync. One guy here did it and broke his front axle twice. The tire sizes you want are 285/30/21 and 295/30/21 which is an exact match for stock.

You could play around with slightly wider front and rears to increase the sidewall a little bit but then you have to be careful with offsets and/or limit the amount you can lower or use spacers etc. I went with a very aggressive offset and super wide wheels to get deep concave on both front and rear wheels plus I knew I wanted to lower. But keep in mind you need to stay within 3% of the stock total wheel/tire diameters for each front and rear AND you need to keep the % difference between the front and rear tire within 2% (factory tire is 1% larger rear diameter than front) to keep the AWD bias happy.

This is probably more info than you are asking for at this time, but feel free to PM me with any specific questions before you order anything.

I'll have pictures coming soon. My M8 is in the shop still getting wrapped in Satin Frozen Vanilla. It was delayed due to a huge snow storm that hit right before the holidays and they resumed working on it today.

Since I don't have pics of my convertible on 21"s heres a M8 Coupe on different wheels than mine in 21" with the same offsets and widths and lowered to give you an idea of how good lowered & 21 looks on this car:
https://ferradawheels.com/pf/smoking-m8/

IMHO it really changes the character/attitude of the car to be much more aggressive looking and sporty than the default which is more luxury cruiser/tourer.

Increasing the size of sidewalls will never make a wheel look like a bigger one. It has the opposite effect and makes the wheel look smaller! I am not sure if you typed that out backwards or I am misunderstanding you intent. The M8 would look really weird with bigger sidewalls than stock.

Yeah I didn't type it clearly but you got my drift. I was trying to make it a floaty softer ride. Non run flat swap for run flats too.
The exact opposite of yours and the OP post, but similar in upsize in that the overall diameter of 21" with small sidewalls is similar size to 20" with larger softer sidewalls.

I was looking to turn the GT car into a soft sedan. You're looking to turn the GT into a Race car.