Tire setup choice

[AB M2C]

Hi all,
I'm trying to decide what tire setup I want to run next and am at a bit of a cross-roads. My car is wide-bodied so I have plenty of room to run either of these options, but not sure what will be best.

First option(s): Run a square setup. This is what I'm leaning toward to make the car (hopefully) more predictable, but I would run either a 275, 285, or 295 square setup. I guess: is more grip/ wider tire always going to win here? Or are there large downsides weight wise to running a wider tire? What is the best trade off?

Second option(s): run a staggered setup. In this case I could really put anything from a 255 up front to a 295, and anything from a 275 to a 315 in the back. I'm considering this only because I could up the grip everywhere substantially, though I don't want to make the car have crazy amounts of grip up front an not enough in back or vis versa. (This car and many others do come from the factory with staggered tire sizes so maybe theres something to it?)

For reference: This is a track specific car though I I'm not racing it in any specific series (so I'm not looking to fit into any regulations as a plus side) Has all the basic m3 suspension mods, diff, coil overs, ht-10 brake pads but other wise stock brakes (hopefully will go BBK soon). Car is putting out upwards of 500 whp.

I'm really looking to just to run faster times on the track, and putting the widebody on was really to enable me to run much bigger tires, so now I just need to decide what tire setup I want to do!

Any help is much appreciated!

[R1wheelieforfun]

Originally Posted by ThatOneKid

Hi all,
I'm trying to decide what tire setup I want to run next and am at a bit of a cross-roads. My car is wide-bodied so I have plenty of room to run either of these options, but not sure what will be best.

First option(s): Run a square setup. This is what I'm leaning toward to make the car (hopefully) more predictable, but I would run either a 275, 285, or 295 square setup. I guess: is more grip/ wider tire always going to win here? Or are there large downsides weight wise to running a wider tire? What is the best trade off?

Second option(s): run a staggered setup. In this case I could really put anything from a 255 up front to a 295, and anything from a 275 to a 315 in the back. I'm considering this only because I could up the grip everywhere substantially, though I don't want to make the car have crazy amounts of grip up front an not enough in back or vis versa. (This car and many others do come from the factory with staggered tire sizes so maybe theres something to it?)

For reference: This is a track specific car though I I'm not racing it in any specific series (so I'm not looking to fit into any regulations as a plus side) Has all the basic m3 suspension mods, diff, coil overs, ht-10 brake pads but other wise stock brakes (hopefully will go BBK soon). Car is putting out upwards of 500 whp.

I'm really looking to just to run faster times on the track, and putting the widebody on was really to enable me to run much bigger tires, so now I just need to decide what tire setup I want to do!

Any help is much appreciated!

I'm in the same boat. I put the ER Widebody kit on at the end of the season last fall. Prior to that I'm running 18x8.5 ARC8s (Square) with 245's RE71's. I spoke with Apex, they said I could stuff a 265 on the 8.5" wide ARC8's, but they'd suggest sticking with a 255 for optimal sidewall stiffness. So, with lack of funding currently for a whole new set of wheels/rubber, and the season coming up in a few months I think my move for now is going to be to grab a set of R888R's in 255 square. Once the funding comes, I'll scoop a set larger set of wheels. Here is what Apex said I have for options, and most of which likely looking at a rear fender mod such as N5tuner or the likes...

90mm studs on the front:
ARC8's- Square: 18x9.5 ET58 275/35 w/considerable rear fender roll
OR
FL5 wheels- Square: 18.5x10 ET40 would enable a square 285/35 or larger even. This would require widebody rear end.

My hopes are to have one of these later setups by midsummer and run a true slick on these and save the 8.5" wide ARC8's for backup or mixed use set. Dedicated track car here too, but just for time attack (this year) and HPDE.

What are you thinking for rims, make/model/size?

[AB M2C]

Originally Posted by R1wheelieforfun

What are you thinking for rims, make/model/size?

I was pretty set on a monoblock wheel either by BBS or BC forged. But lately I'm thinking I'll go with the Apex FL-5 wheel. They're almost the same weight and like half the price. FL-5's would be 18x10.5 for et22, and 18x11 et44 in the back.

Monoblock forged wheels are obviously going to be stiffer, stronger, and lighter, but for the money I just don't know if they're worth it.

[BimmerAg]

With 500whp I wouldn't worry too much about the added weight from the tires. A square setup will likely be a little more biased towards oversteer if you have that much power, and if you're running different size wheels then there's no benefit as far as rotating for better wear. I think it comes down to what are your goals? If you want the absolute fastest lap times then get the most tire you can at either end and then tune suspension for handling balance. If you just wanna have fun, a square setup will give you a little more playful rear end, and will probably be a little cheaper.

[John_01]

With a high power setup, something like 265/35 front, 295/30 would be ideal IMO.
A square setup with 265/35 all round would also be good if using R-comps. In that case you will cook the stock brakes before the R-comp tires overheat.

There is also the question of whether the cooling system on the car will cope with longer periods at full throttle. The suspension setup and driver skills will also need to be up to the task. IMO, part of the choice probably depends how fast you want to go. Square 265/35 set of R-comps will be still very capable, and may be a more economical and realistic option.

[AB M2C]

Originally Posted by John_01

With a high power setup, something like 265/35 front, 295/30 would be ideal IMO.
A square setup with 265/35 all round would also be good if using R-comps. In that case you will cook the stock brakes before the R-comp tires overheat.

There is also the question of whether the cooling system on the car will cope with longer periods at full throttle. The suspension setup and driver skills will also need to be up to the task. IMO, part of the choice probably depends how fast you want to go. Square 265/35 set of R-comps will be still very capable, and may be a more economical and realistic option.

Thanks for the reply. I think that's an interesting choice tire wise. I have the ER double oil cooler setup so I'm not worried about over-heating the motor. Brakes are high up on my list to replace, because they do get cooked, and thats not exactly fun. Though the real reason I'm worried about tire weight is that is going to be the biggest thing to cause extra brake fade.

I'll be honest though I think you're not quite on the money with a 265 square setup. I have Proxes r888 in a 255 right now and they are not good enough to hold down that amount of power. I've throw around the idea of going to a full slick setup, however I like the slip angles and recovery the toyo's provide.

Because of this a 275 I've decided is the skinniest I want to run whether it be square or just in the rear.

One thing I'm excited about doing this year (kind of nerdy) is re-tuning my suspension. I'll need to stiffen it up substantially with the wider width, but how much? I don't know. Only one way to figure it out though!

[bionicbelly]

You might think about trying a better brake pad before going to a bigger brake set up. Something like G-LOC 18's or Carbotech XP20's. They won't go away on you. Add some cooling, and you should be golden.
I am with you on the 888's too. They are definitely fun to drive on. I did some testing with toyo RR's and R7's, and the R7's were 3.5 seconds a lap faster than the toyo's, but such a nice controlable slide on the toyo's make them my dick around tire.

[OkieSnuffBox]

Originally Posted by ThatOneKid

Thanks for the reply. I think that's an interesting choice tire wise. I have the ER double oil cooler setup so I'm not worried about over-heating the motor. Brakes are high up on my list to replace, because they do get cooked, and thats not exactly fun. Though the real reason I'm worried about tire weight is that is going to be the biggest thing to cause extra brake fade.

I'll be honest though I think you're not quite on the money with a 265 square setup. I have Proxes r888 in a 255 right now and they are not good enough to hold down that amount of power. I've throw around the idea of going to a full slick setup, however I like the slip angles and recovery the toyo's provide.

Because of this a 275 I've decided is the skinniest I want to run whether it be square or just in the rear.

One thing I'm excited about doing this year (kind of nerdy) is re-tuning my suspension. I'll need to stiffen it up substantially with the wider width, but how much? I don't know. Only one way to figure it out though!

The extra weight of the tires is essentially meaningless when you consider a 3300+lb car with 500whp.

The front brakes need ducting and you need REAL pads on the car. HT-10s are not real track pads.

DTC-60 at minimum, but I'm partial to Carbotechs myself. Great feel and longevity. Another bonus is you "can" use them on the street if you can deal with the noise and dust, but they don't eat your rotors like other pads......AND the dust is non-corrosive, so it doesn't eat the finish on your wheels and paint.


Also you didn't mention fluid, you need at least Motul RBF 660 in the car.

[bbnks2]

Originally Posted by OkieSnuffBox

The extra weight of the tires is essentially meaningless when you consider a 3300+lb car with 500whp.

The front brakes need ducting and you need REAL pads on the car. HT-10s are not real track pads.

DTC-60 at minimum, but I'm partial to Carbotechs myself. Great feel and longevity. Another bonus is you "can" use them on the street if you can deal with the noise and dust, but they don't eat your rotors like other pads......AND the dust is non-corrosive, so it doesn't eat the finish on your wheels and paint.


Also you didn't mention fluid, you need at least Motul RBF 660 in the car.

I agree. People complain about stock brake setup and they are running shitty pads like Stoptech "sport." $70 Stoptech pads, or pads like hawk HP+, literally provide LESS braking coefficient than stock pads. They stuck. Put a real race pad on the car and vent your brakes.

Run the widest tire setup you can (as much poke as possible). As you increase grip braking G's you'll need higher coefficient pads to maintain the same brake feel and stopping power. My car generates .9-1.1 g's of braking force with 200tw 255s and PFC-08 pads. With 275 R-comps up front I can generate 1.1g's consistently and I've seen as much as 1.2-1.3g's. That is damn impressive and all with the shitty stock calipers and ENDURANCE oriented track pads. PFC makes much higher coefficient pads that don't last as long but would provide better "bite."

[AB M2C]

Originally Posted by OkieSnuffBox

The extra weight of the tires is essentially meaningless when you consider a 3300+lb car with 500whp.

The front brakes need ducting and you need REAL pads on the car. HT-10s are not real track pads.

DTC-60 at minimum, but I'm partial to Carbotechs myself. Great feel and longevity. Another bonus is you "can" use them on the street if you can deal with the noise and dust, but they don't eat your rotors like other pads......AND the dust is non-corrosive, so it doesn't eat the finish on your wheels and paint.


Also you didn't mention fluid, you need at least Motul RBF 660 in the car.

I don't know if you're quite right thinking that stopping unsprung weight is non-consequential compared to sprung weight (same concept as why you don't want heavier unsprung weight for acceleration, I might be wrong about that though, which would make my whole point of going for a lighter setup moot). I do run Motul RBF 660. So should be good on fluid. And thanks for the brake advice I'll pick up a pair of the carbotechs and see what i think!

Anywho can we please get away from brakes as that is not why I started this thread. Looking for tire size advice and suggestions. Thanks.

[OkieSnuffBox]

I wouldn't mind staggered on a car with that much HP, other than not being able to rotate. That's really the more important question, is being able to rotate tires to get a bit more life more important than having more rear grip to tame the amount of power you have.

That's something YOU have to decide.

As for your obsession with tire weight, GRM did a test a few years ago that showed even on a Miata it doesn't matter (time wise) and that a BMW went faster each time they added more grip with a larger, heavier wheel setup.

[bbnks2]

Originally Posted by OkieSnuffBox

I wouldn't mind staggered on a car with that much HP, other than not being able to rotate. That's really the more important question, is being able to rotate tires to get a bit more life more important than having more rear grip to tame the amount of power you have.

That's something YOU have to decide.

As for your obsession with tire weight, GRM did a test a few years ago that showed even on a Miata it doesn't matter (time wise) and that a BMW went faster each time they added more grip with a larger, heavier wheel setup.

Staggered also means a different front and rear wheelbase... staggered is going to effect the cars balance and handling and not just the cars ability to lay down power.

[AB M2C]

Originally Posted by bbnks2

Staggered also means a different front and rear wheelbase... staggered is going to effect the cars balance and handling and not just the cars ability to lay down power.

Ya I mean that statement is really the focus of the question I'm asking. Thanks for putting it in much easier to understand words.

[OkieSnuffBox]

Originally Posted by bbnks2

Staggered also means a different front and rear wheelbase... staggered is going to effect the cars balance and handling and not just the cars ability to lay down power.

Wheelbase? No. Track width? You could argue roll centers and such.

We aren't talking about roundy-round cars where the car is literally built to turn.

Please explain how wider rear tires change the front hub to rear hub centerline.

This will be interesting.

[bbnks2]

Originally Posted by OkieSnuffBox

Wheelbase? No. Track width? You could argue roll centers and such.

We aren't talking about roundy-round cars where the car is literally built to turn.

Please explain how wider rear tires change the front hub to rear hub centerline.

This will be interesting.

Yes, I meant track width.

[bionicbelly]

Originally Posted by OkieSnuffBox

Wheelbase? No. Track width? You could argue roll centers and such.

We aren't talking about roundy-round cars where the car is literally built to turn.

Please explain how wider rear tires change the front hub to rear hub centerline.

This will be interesting.

[bionicbelly]

Originally Posted by ThatOneKid

Ya I mean that statement is really the focus of the question I'm asking. Thanks for putting it in much easier to understand words.

This is just my .02 cents worth, but a square set up is always easier to work with, better for tires, and better to drive. We drive different kinds of cars, to be sure, (I am more of a low hp, corner speed kinda guy) So with the kind of HP you have, a staggered set up may well be better, but in my experience, a square set up will be more balanced, breakaway/slip more controlled, and you can rotate tires which saves a significant amount of money.

If I were in your situation, I would put as much tire under the front as possible, then whatever that happens to be, put it on the rear as well.

The reason the stock wheel sizes are the way they are is to artificially induce understeer, which is the safest way to set up a car. frustrating as shit to drive hard though.

[AB M2C]

Update on this:

I decided to go with a 285-30-18 setup on 18x10.5's squared Went with the hankook ventus z221 C70.

I've never run this tire, but it was one of the few high performance non-slick tires in the size I was looking for.

I may switch to r7's in the same size or an r888r in a 295-30-18 later this season but we'll see. (I don't think the 295's will fit on the front, clearances are crazy tight with how wide the track is on the car). Having said that the only place I get rub is at full left lock and then its only because the oil cooler vent into the wheel well sticks out a little bit. I have the ER twin cooler setup though, so I repositioned both about an inch forward of where I had them, so the wheel has no chance of denting the fins.

When compressed and turning at sharper angles I'll most likely get a little bit of rub on the front fenders, but other than that I seem good to go.

Now to change up the spring rates to account for the extra width! I'm also interested in sway bar suggestions, if anyone thinks I should change those up for higher spring rates and the wider trackwidth of the car?