Best Tire Size for Stock Rims
 

I'm getting ready to order some Michelin PSS for my stock rims as I can't really afford wheels this year. Will going to a 225/45/17 tire provide me any benefit over the stock size? Or will it just create more sidewall flex? I am running RCE springs and sways and a bunch of whiteline bushings.

Thanks

I'm guessing it will create more sidewall flex, at least that's my guess. I was wondering the same thing.

The Mich' PSS have a pretty stiff sidewall. If you haven't done any testing of sidewall stiffness personally, you may not even notice this jump in size.

I think that the added contact patch, along with the better grip compound found in the PSS, will more than make up for any sidewall wiggle. I am trying to make the decision as well. My choices are 225/45 or 235/40 considering availablity, price, and weight.

My priorities are: larger contact patch, weight, then cost (but I wont go to the top tier, even in road tire compounds, the money vs. performance for my needs doesn't compute). Direzza II's, BFG Rivals, or 'Kook RS-3's, the PSS were nice on my 350z, but there are some that are comparable for much less.

Eric G

Are you considering 235 for the stock rims?

225/45-17 is 1.3% larger
235/40-17 is 1% smaller
235/45-17 is 2.9% larger
245/40-17 is 0.3% larger

Good thread because many of us will go this route for sound reasons.
I wish there were some pics of those sizes on the OEM rims to see what they look like fitted?

The stock tyres start complaining far too soon. There are lots of reasons being given to justify their being fitted but for me they are an achillies heel that needs to be fixed and I don't think I can wait until they are knackered.
I get my adrenalin fix by sometimes legally taking roundabouts, turns and corners quickly, followed by a quick burst to the speed limit. Then look in the mirror to see how far back the guy is that was just up my clacker.
I want to do that so it looks and sounds like normal driving not with the tyres making noises like it's on the edge, which it isn't.

Tyre choice is vital. I don't want an expensive tyre that shreds itself to give exceptional grip. I want a good all round tyre that lasts, is good in the wet, looks good and is a bargain. The last bit[price] is flexible but the others aren't.

Personally, I'd stick with OEM 215. Your speedometer will be more accurate. If you're looking for maximum grip, you shouldn't be looking at Michelin PSS tires to begin with. I doubt you'd feel a difference between 215 and 225 under 95% of your driving conditions.

The speedo is already inaccurate and reads about 4-5% above the actual speed. So even the 235/45-17 will have it reading over by 1-2% but be more accurate than stock.

My concern with wider tyres on 7" rims is whether they will take away anything from the reaction of the steering by moving in relation to the rim?
Stiffer sidewalls will help counter that but at the cost of the ride.

Proof of this? Not saying you're wrong but I've never heard of this.

I also agree about the 225 tires being too wide for 7" wide wheels.

I've had Azenis 215's (great old sticky street tire before this new gen of street-stickies) on by old Contour SVT/Mondeo for daily driving, and had no problems with speedo issues and had an excellent drive quality. Great sticky tire for a wonderful, albeit front wheel drive, chassis.

My tire choice is also based upon SCCA autocross rules for Road Tire classing. I would like the stick without much concern for speedo corrections, however I do spend much time on the miata.net tire calculator when selecting tires and switching wheel/tire combos.

Eric G

It's almost universal but you get confirmation from the radar speed courtesy screens they set up sometimes. You could also get confirmation on the roads that are marked every km or mile for the air traffic cops to monitor our speed.
The easiest though is to take a GPS in the car which should accurately read the speed and compare the readings.

The reason here and in most other countries probably, is that it's illegal for a speedo to read under but it can read up to 10% over. So they set them in the middle to be safe at 5% over and any variations will be about that point.

How do they wear and is the price getting up there?

I went with PSS in stock size 215/45/17. I was concerned that the wider 225 size on the rim would decrease steering response. I love the tires. They are good even in colder weather in the 40s. 225/45 is the widest you can safely go with a 7 inch wide rim.

225 isnt too big for 7 inch width stock E36 M3 wheels are 7.5inches and have stock 235/40/17 the 215s are a drop stretched if you hadnt noticed.

i did some math and the the size is like 45% of 215 is 96MM 225/40/17 would be best fitment cause 40% of 225 is 90mm and 45% of 225 is 101mm

im probably going with a 225/40/17 thinking about continental DW summer tires i hear good things. good tractin in wet and dry good tread life and they are roughly 120$ per tire which isnt bad.

maybe a tire guru can chime in see if im correct or not.

I am also running Michelin Pilot super sports in factory size (215/45/17). A tremendous improvement. Not only is it a stickier tire but the tread is 0.2" wider.