So I have a Mini r52 Cooper S and currently I have bridgestone potenza re71rs on. I drove my father's BMW m240i for the past day or so which is supposed to have a superior chassis, right? My dad's car had the stock pilot super sports but it couldn't grip as hard as my Mini, when I tried to turn at the same speeds as I did in my mini I got some under steer. I was shocked at the difference especially since I was under the assumption that a two series would make a better track car, so is this down to the tires? How much of a difference does it make?

 

I think it's a combination of things. You are overestimating the 2 series chassis and underestimating the RE71Rs. There's a reason those are the go-to autocross tire, and it's not for the quiet ride and water evacuation.

I haven't driven your father's car but I've driven a previous gen 135i with Msport suspension and I thought it was a joke. Don't get me wrong, I fell madly in love with the engine, but the suspension was certainly engineered and spec'd for comfort over handling.

 

Curb weight makes a difference too --- the M240i sits at 3,400 pounds.

 

You're probably right. I did get the re71rs for the grip, but shouldn't the two series have a superior chassis than the Mini atleast? That being said though, it does feel like the mini can get through tight s turns and hairpins quicker and more easily than the m240i. It just feels more agile, idk.

 

Your MINI is very capable. Your tires are Extreme Summer tires treadwear 200 and grip very well in the dry. The MINI benefits from having the best tires when doing performance driving. Extreme Summer tires are good for track or autocross and wear fast, they are typically loud, firm riding and somewhat good for wet.

Rule of thumb- when you have a very good car that is capable- tires make a huge difference but compromises are made since all out performance and livable daily street manners are at opposite ends of the spectrum.

The BMW M240i comes with OEM Michelin Pilot Super Sport tires- Max Summer treadwear 300, very good street tires but not as grippy as Extreme Summer tires. These are for daily driving- good performance with low noise, comfortable ride quality and good wet grip with longer treadlife than any Extreme Summer tire.

 

While I haven't driven an m240i, I can speak to RE71Rs on an R53. When I switched from Federal SS595 on mini s-lites to RPF1 wrapped in RE71rs, it felt like I was driving a completely different car. The acceleration is noticeably faster probably due to the lighter rotational mass. The turn in is crisper and quicker too, with more feedback. Somehow, the torque steer decreased too. My only gripe is I can't rotate the car as easily anymore. So yeah, to answer your question, in my experience, tires make a huge difference.

 

My buddy(Who I have run with many years down on the Dragon, he with his modded R53) now with an M240i and I in my highly modded R50 on RE-71R’s ran the Dragon together. He struggled to hang with the mighty Justa. He immediately went out and bought RE-71R’s! He is now closer, but not quite as quick. Lol

 

Drove a justa once, even though it was an r56 with an auto gearbox, thing was still real fun. For some reason it seems on these tight twisty roads that having less power and needing to wring the engine out is more fun than driving a more powerful car.

 

I guess I've been underestimating my car my friends make fun of me and call it a "slow" car, which I guess it is in a straight line, but I've never driven anything more fun in the corners. I even prefer it to a lot of more expensive newer cars because it just feels more connected to the road. How many g's would my car pull around a skidpad? I know the m240i does something like 0.94, so would the mini pull closer to 1g or more?

 

I noticed this as well, although I can still get it to rotate but its harder, the car feels more neutral and balanced with these tires, I love it.

 

Having some adjustment in my suspension allows me to dial in more or less understeer with changing conditions of track, autox course or Dragon. Tires are another part of this suspension and a big part of the on road grip!
My current adjustments:

-large adjustment; 25mm rear sway bar

-medium adjustment; KONI Yellows front and rear

-smaller adjustment: tires air pressures

 

My saying has always been there is only 4 things between my butt and the road. That is why we should always put value and not skimp on tires. We can all make 500hp and do any suspension mod in the world but a cheap tire or a non performance tire just takes you 3 steps back.
I've never had good luck or feel from Bridgestone so I don't use them or recommend.

Also always be aware of tire reviews have very little value. Simple thought is people often will review a tire and say how great it is, but fact is they have been driving around on worn out tires so any new tire is always going to feel better. Or they just went from runflats to non runflats and same thing they'll think their new tires are Sooo great when they are just not runflats.