245/275 on OEM Wheels??

[mgwatson48]

I know this has been beaten to death here but I'm about to pull the trigger on some 245 front 275 rear conti extremecontact DWs... My question is directed to those running these exact tire sizes on their OEM wheels: DO you loose A LOT of the turn-in compared to the 225 fronts? and is the grip noticeably better??

Also, does anyone have any closeup pics of these tire sizes on the OEM wheels? I'd like to see how much "meat" hangs over the lip and what the 275s look like from the rear

Thanks!

[runnerx]

I am running 245/275 on OE wheels but they are dunlop star spec. and no issue at all.

[mgwatson48]

How was the cars turn-in with the wider fronts?

Does the car feel any sloppier?

[runnerx]

turn in is not as snappy as before but I love the extra grip it gives. I have GC track school kit installed. No rubbing at stock ride height; however, any lower would start to rub when the steering is fully locked. This is just with the Dunlops I have, Conti could be very different.

[mgwatson48]

All I needed to know! Thanks runner.

[03BeastCharmer]

Here is a picture of my old ride on 245/275 Star Specs on OEM wheels.

[BIMMERGUY91]

Originally Posted by mgwatson48

I know this has been beaten to death here but I'm about to pull the trigger on some 245 front 275 rear conti extremecontact DWs... My question is directed to those running these exact tire sizes on their OEM wheels: DO you loose A LOT of the turn-in compared to the 225 fronts? and is the grip noticeably better??

Also, does anyone have any closeup pics of these tire sizes on the OEM wheels? I'd like to see how much "meat" hangs over the lip and what the 275s look like from the rear

Thanks!

Ill do you one better. I am running these exact tires size brand everything on my oem wheels. The grip is much better and you dont really lose much turn in. Go look at my pics here http://www.zpost.com/forums/showthread.php?t=666194 to see how they look.

[The HACK]

I'm going to answer this in my usual unnecessarily long and vague fashion. Take from it what you will.

First, a little anecdote. For a while I ran 245/275s on my street rims (Toyo R1-R on my replica Alpinas). That was my exclusive setup for about a year (2007-ish), and I'd go to track with it as well as drive regularly on the street on that setup. R1-Rs are phenomenally grippy for a "street" tire, by the way. Then my carpool buddy at the time decided to buy an E46 M3. And he's particular with the tires, the car came with 18" rims riding on PS1s with about 10,000 miles on them. He wanted to buy PS2s for his 19" rims and Advan Neova AD08's for his 18"s, so he GAVE me the 18" PS1s off of the 18" rim for free.

Who am I to turn down free tires.

So in order to preserve the R1-Rs, I mounted the PS1s (225/255 per stock E46 M3 specs) on the stock rims and drove it on the street and left the R1-Rs on the Alpina Replicas and used them exclusively for the track. When I drove the car with PS1s installed on stocker rims I was downright SHOCKED at how much more responsive the steering was. It wasn't just a little bit better, the front end almost felt telepathic. The response was so good that it made the front end feel "dart-y." Now, this is inline with what I experienced before on my E46 323Ci, when I switched from 225s all around to 245s all around. Steering feel, or response to steering changes, feels more muted or not as crisp.

That is, until I had the 323Ci properly aligned. After putting about 2 degrees of negative camber up front, the front end came back alive. I don't know what it is and can only speculate, but it appears to me the wider front tires likes more negative camber or a combination of negative camber AND less toe-in. Sure enough, after I had my MZ4 Coupe properly aligned and corner balanced, the car felt much better with the wider 245 tires up front. But by that time I'm running 245/275s on both sets of rims (the Alpina replicas now running Falken RT-615Ks and the stockers running Nitto NT-01). So I can't tell you if my current alignment setting will make the car feel even THAT much better on 225s up front.

As for grip, I'm going to go counter to conventional wisdom and say that, unless you're overheating the tires, wider tires doesn't give you more grip. Wider tires will allow you a bigger surface area to dissipate heat, so unless you're having problem with grip up front due to heat, running 245s won't necessarily gain you more grip in the turns than say, a 225. Where 245s will come in handy is on the track when you're wringing every ounce of grip available out of the tires, where the 225s will start losing time due to the tires operating outside of it's optimum tire temp while the 245s will still have enough surface area to dissipate heat fast. And the nature of the rubber is, the more you push it outside of its optimum tire temp, the faster it gets hotter (due to kinetic friction generating more heat than static friction) and therefore the quicker it goes away.

The only caveat to the above theory is that, wider tires in combination with larger negative camber and some toe-out will actually allow you to keep a more optimum contact patch in the middle of the turn due to the nature of an inflated rubber constrained by 2 rigid ribs, and that the same combination of camber and toe also allows heat to spread out more evenly on a wider tire.

So, if you're still reading...The summary version is, wider tires will rob some steering response, and it won't necessarily provide better grip through turns. What it will do for you though, is provide better heat dissipation for track use, and also better contact patch management through the use of additional camber and toe-out.

Simple version: If you're on stock camber and not going to the track, you'll actually lose some performance by going wider.

Lastly, and this is something I've confirmed with multiple sources within the racing industry...Most experienced racers will only run as wide as necessary, not possible. In fact, I spoke with the fine folks that aligned and CB'ed my MZ4 Coupe, and they race in SCCA AX and had the budget to test extensively their setup for their stripped and caged RX7. Turns out they run a narrower tire than what their competition runs, and they had room to run a 10mm wider tire but testing shows that they're 1/2 second faster on average on the narrower tire.

Go figure.

[XMetal]

Originally Posted by runnerx

I am running 245/275 on OE wheels but they are dunlop star spec. and no issue at all.

What's the exact sizes that you're running? Thinking about this exact setup on my next set. Thanks.

[runnerx]

This is why I enjoy reading Hack's post! Learnt a lot from his posts... Thanks Hack for the detailed explanation.

[runnerx]

Originally Posted by XMetal

What's the exact sizes that you're running? Thinking about this exact setup on my next set. Thanks.

245/40/18
275/35/18

[k2pilot]

I'm rocking 245/275's on stockers, not only that, I'm also on the stock aspect ratio (45F/40R), I just didn't want to reduce the rolling diameter of the wheel. Main thing I noticed was a big reduction in gas mileage, i think the ideal size is a 235/45/18 in the front and 265/40/18 in the rear, unfortunately most good tires don't come in a 265/40/18.

Also it's putting a bit more strain on my power steering pump.

[mgwatson48]

Great response Hack!! Definitely something to think about because my favorite part of the car is the quick turn in. Interesting!

[XMetal]

Originally Posted by k2pilot

I'm rocking 245/275's on stockers, not only that, I'm also on the stock aspect ratio (45F/40R), I just didn't want to reduce the rolling diameter of the wheel. Main thing I noticed was a big reduction in gas mileage, i think the ideal size is a 235/45/18 in the front and 265/40/18 in the rear, unfortunately most good tires don't come in a 265/40/18.

Also it's putting a bit more strain on my power steering pump.

I'm not sure why 245/45/18 & 275/40/18 have such a large reduction in gas mileage since these sizes are nearly an inch taller in rolling diameter compared to OE sizes. If any, I would have expected it to increase your gas mileage, not the other way around. The only logical explanation would be the wider contact patch caused an increase in rolling resistance

[schwank]

Ive been running 245/275 direzzas on the track for a few years, and stock sizes on the street (I have two sets of stock rims...) the car feels much lighter and more nimble with the 225's on the front I also find my car is dirtier on the street if I run the 245's lol

[SmartBastard]

I had 245/265 on OEM wheels and it felt a lil bit weird. It was floating around the road pretty bad. When I switched the same tires to a 1" wider rims it was a night and day difference.

[Kgolf31]

Once again, awesome post Hack.

I have 235/45 and 265/40 RS3 Tires mounted on OEM wheels and they take up most of the wheel. I believe 245/275 is extending the limits of what the wheel can hold, and from there you get the side-wall flex that in turn goes to sloppy steering...IMO.

I have yet to run on the tires yet...so we'll see how they compare to OEM Spec 225/255 T1Rs I have on now for DD

[DaveL--2mnycars]

Originally Posted by The HACK

I'm going to answer this in my usual unnecessarily long and vague fashion. Take from it what you will.





...
So, if you're still reading...The summary version is, wider tires will rob some steering response, and it won't necessarily provide better grip through turns. What it will do for you though, is provide better heat dissipation for track use, and also better contact patch management through the use of additional camber and toe-out.

Simple version: If you're on stock camber and not going to the track, you'll actually lose some performance by going wider.

Lastly, and this is something I've confirmed with multiple sources within the racing industry...Most experienced racers will only run as wide as necessary, not possible. In fact, I spoke with the fine folks that aligned and CB'ed my MZ4 Coupe, and they race in SCCA AX and had the budget to test extensively their setup for their stripped and caged RX7. Turns out they run a narrower tire than what their competition runs, and they had room to run a 10mm wider tire but testing shows that they're 1/2 second faster on average on the narrower tire.

Go figure.

I truly appreciate your response. You've taught me something! Much appreciated.

DaveL
Toronto