205 or 215 for 17in wheels - Daily Driver and Autox

[RAAMaudio]

By the way, I have been reading and using rules of different orgs for decades so pretty familiar with interpreting them but sometimes a rule or two is not quite clear so have to ask the director to make sure following them correctly.

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Street Prepared class:

Allowed:

IC change as long as nothing cut to fit it.
Bypass valve (see note below)
Down pipe
Engine mount

Not allowed:

BOV or pop off valve change (have to determine if this car is considered to have one of these but more likely ours is a considered a bypass valve which is legal)

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Your class is Street Prepared unless the BOV/bypass is considered BOV then is so it would mean Street Modified which is a pretty wide open class.

I do not always agree on some of the rules but they are there to keep things as even as they can in each class and stock the ST is likely to be bumped up a class next year, any dominant car normally is.

My advice, mod your car anyway you want then run the class it falls into and accept whatever results you get.

BUT, race against all the classes in your mind, I always do that and have great fun

 

[mercdank]

Wow, thanks for your input! I know I started reading all the mod rules and got confused, your comments definitely help.

 

[RAAMaudio]

Glad I can help and will do so more if needed, I will go over the rules for any organization and help make sense of them if possible. As mentioned some are rather hard to understand and some do not seem to make any sense at all but the complexity of fitting so many different cars into so many different classes and making them competitive is a very daunting task to say the least.

 

[Zissou]

I am more inclined to run 205 on 8's 215 on 8.5 and 225 on 9's for the maximum performance but that is for road course use.

For auto cross you can change that up quite a bit but you want to use tires designed with that in mind, it is why the 215 Dunlops are working well for FORZDA2 and likely the best tire for your needs, quite a bit lower cost than the Yoko and probably faster as well.

Oh professor RAAM I have questions about tires too!

My assumption was that a wider tire = more grip and there is only a range of width tires than can fit on a given wheel. So going with a wider wheel means getting a wider tire to match. It appears that is not the case, as I'm seeing the popularity in running our narrow tires on wide wheels. That seemed backwards to me; more weight from the wheels without getting wider tires. Does a given 205 wide tire stretch out if it's mounted on a wider wheel? What's the deal here?

I had been thinking of going 215 wide on stock wheels, or maybe 225/235/245 on 7.5" or 8" wheels as in my mind wider tire = more surface area touching the road. I like the looks of the tire being flush or wider than the wheel, but am I going to lose performance due to what I assume is a decrease in sidewall stiffness?

Thanks!

 

[RAAMaudio]

Picking a tire and wheel combination is rather a complex formula if you look at each aspect involved but luckily most of this has been figured out at a very high level of competence and we just need to plug in a few variables to sort out which is best for our particular needs.

The more info the more closely one can determine what is best for your use of the vehicle.

If you can answer these questions as realistically as possible the recommended options are easier to work out.
The questions may not be in the best order but all are pertinent.

1) Intend on buying new wheels now or later?
2) Interested in the absolute grip no matter the cost and how long they last?
3) Mainly need summer tires or all season or truly 4 season tires?
4) Interested more into how it all looks on the car more than ultimate performance?
5) Budget?
6) Autocross, HPDE, etc plans?

EDITED: Fugure mod plans?

This is a good start, there may be more info needed or more exacting depending on your particular needs, wants, etc.....

 

[AMontgomery]

Adding to what RAAM said with a bit of explanation on the physics:

Buy the widest rim you can fit for your desired modifications (though weight of the rim plays into this step significantly)

Pick your desired characteristics: Straight Line grip or lateral grip? More linear grip is achieved with a squishy fat tire that is slightly wider than the tire it is mounted on (think top fuel drag cars). Lateral grip, and more importantly the individual characteristics that make up lateral grip (turn-in effort, tire communication, etc) are achieved by a stiff sidewall and a sticky compound. A narrower tire on a wider rim yields a stiffer sidewall. A thicker constructed sidewall is stiffer also. So combine a super stiff sidewall (like an AD08R or Star II) stretched over a wider rim would yield more lateral grip but at the cost of a much more communicative (read harsh) ride.

Now, in my case, the AD08R I'm running is slightly wider than the stock Potenzas, however, the Potenza has a much weaker sidewall than the AD08R, so I'm actually a bit stiffer than the stretched Potenza, meaning they have the same or better lateral communication and grip as the stockers while having better linear grip.

It's all in what you want your car to do, and if your racing organization has certain guidelines.

 

[15performanceblue]

Adding to what RAAM said with a bit of explanation on the physics:

Buy the widest rim you can fit for your desired modifications (though weight of the rim plays into this step significantly)

Pick your desired characteristics: Straight Line grip or lateral grip? More linear grip is achieved with a squishy fat tire that is slightly wider than the tire it is mounted on (think top fuel drag cars). Lateral grip, and more importantly the individual characteristics that make up lateral grip (turn-in effort, tire communication, etc) are achieved by a stiff sidewall and a sticky compound. A narrower tire on a wider rim yields a stiffer sidewall. A thicker constructed sidewall is stiffer also. So combine a super stiff sidewall (like an AD08R or Star II) stretched over a wider rim would yield more lateral grip but at the cost of a much more communicative (read harsh) ride.

Now, in my case, the AD08R I'm running is slightly wider than the stock Potenzas, however, the Potenza has a much weaker sidewall than the AD08R, so I'm actually a bit stiffer than the stretched Potenza, meaning they have the same or better lateral communication and grip as the stockers while having better linear grip.

It's all in what you want your car to do, and if your racing organization has certain guidelines.

you and [MENTION=636]RAAMaudio[/MENTION] make awesome points. I have been through every tire thread I could think of...I really want to buy rims and tires next spring, but Moving into a house around that time and making the big step with the girlfriend (Ring time) Wont allow me to do both. Ha. So I am most likely going to get just tires, and keep the stock rims. I need GRIP! I want 215/40/17, but I need a straight line grippy tire. Which the stocks potenzas cant even come close to giving me grip, and they are like 7/10 tread wise. So a good recommendation of tires that will help the ride at least feel a little better, and will allow me good traction would be awesome!

 

[AMontgomery]

What are your current mods? A 215/40 Star II or AD08R wouldn't even chirp in a 1-2 shift on a stage 1. I would figure a stage 3 would be about like stock on the stock Potenzas for straight line acceleration.

 

[15performanceblue]

What are your current mods? A 215/40 Star II or AD08R wouldn't even chirp in a 1-2 shift on a stage 1. I would figure a stage 3 would be about like stock on the stock Potenzas for straight line acceleration.

I am stage 3 with out the intercooler, E30 tuned. Vdyno says 330WTQ. 230WHP. if that gives you an idea.

 

[FORZDA 2]

.......So a good recommendation of tires that will help the ride at least feel a little better, and will allow me good traction would be awesome!

You have changed the requirements. If you want a tire that will "help the ride" AND give "good traction", they are practically mutually exclusive. I see you live in Michigan so you need a tire that's good in shit weather. I recommend the Kumho 205/40x17 Ecsta 4X. It will "help the ride" and give "good" traction, but for road use only.

The Dunlop Star Specs will howl at speed and ride like shit, but will grip like glue. There's no such thing as a tire that does it all.

 

[15performanceblue]

You have changed the requirements. If you want a tire that will "help the ride" AND give "good traction", they are practically mutually exclusive. I see you live in Michigan so you need a tire that's good in shit weather. I recommend the Kumho 205/40x17 Ecsta 4X. It will "help the ride" and give "good" traction, but for road use only.

The Dunlop Star Specs will howl at speed and ride like shit, but will grip like glue. There's no such thing as a tire that does it all.

True, I guess I just want a little less bumpy. So taller would be ok with me. I do live in MI, but I have snow tires for that. I just need a max performance summer tire with a bigger side wall and wider for a little more traction.

 

[AMontgomery]

It would be worth checking to see what class you would be in if you became competitive in autocross. Your mods certainly take you out of the mostly stock classes, so a higher class may not have the treadwear requirements that the lower classes do. That would open up the AD08R which is fantastic.

If you want to improve the ride, the easiest place to do that is by replacing the dampers/shocks with less compression and rebound damping. The stockers are overly stiff leading to an artificially sporty and harsh ride. The correct balance of damping, springs, and bracing will yield a better ride and a better handling car.

 

[RAAMaudio]

Some great advice here

I have BC coilovers with stiffer springs, firmer but more flexible suspension bushings, 225 Rival S tires and the ride is far better than stock and really surprisingly quieter and rides much better than the stock tires or the 205/45/17 Mich PS3 A/S I had on before.

 

[15performanceblue]

It would be worth checking to see what class you would be in if you became competitive in autocross. Your mods certainly take you out of the mostly stock classes, so a higher class may not have the treadwear requirements that the lower classes do. That would open up the AD08R which is fantastic.

If you want to improve the ride, the easiest place to do that is by replacing the dampers/shocks with less compression and rebound damping. The stockers are overly stiff leading to an artificially sporty and harsh ride. The correct balance of damping, springs, and bracing will yield a better ride and a better handling car.

I appreciate the response and help! I am going to eventually go Coilovers, but again the house and the Ring for the girlfriend total kill the budget for car parts. Which is why I will most likly be sticking with the stock 17's just a wider and stickier tire so I can at least get traction in 2nd gear. Ha. Autocross is honestly probably out of the question. I used to autocross in my 2.4 swapped first gen neon. That was a blast, and the FIST could NEVER top that. So I honestly, don't think it would be worth it to spend the money on tires, and not have nearly as much fun.

 

[pelotonracer2]

It seems that some of the better performing tires that will fit our vehicles tend to be the bigger 215/40R17 size instead of the stock with 205 width. I have been able to find some offerings in the stock tire size, but they are either too aggressive IE for track or autocross use only, or they are not aggressive enough to offer a performance increase over the stock Potenza RE050As.

I do autocross events pretty regularly, my last one was the 9/27, and I have one on 10/18, and then again on 10/25, and another 11/14. I also drive about 70 miles a day in my daily commute, not including extra driving I do for my business which can mean I put easily over 100 miles a day on the car in highway and city traffic.

I am looking for a tire that will give me decent street life, something like 15,000 miles before I have to replace them, and also be significantly better than the stock Potenzas for autocross. I plan on staying with a 17x7 wheel, so 205 and 215 width are what I am looking for. I have been able to narrow it down to these few below. I would really like some feedback or even suggestions for other tires that you think would be appropriate for daily and autox.

205/40R17

• Michelin Pilot Sport AS/3 (after seeing the thread on here about their total failure at the slalom, they are no longer in consideration)
• Falken Azenis RT-615K - these seem like a good balance
• Toyo Proxes R888 - example of too aggressive for daily use, but good tires nonetheless
• Nitto NT01 - again, too aggressive for daily, but a very good tire

215/40/R17

• Dunlop Direzza ZII Star Spec - very nice balance of track and daily, this is a highly considered option
• Yokohama Advan Neova AD08R - another very nicely balanced tire, this is also in the running

Please comment and if you have any other suggestions I would really like to hear them. Thank you for reading.

I love my 215/40-17 DII Star Specs. I'm on my second set although the original ones were not star spec DIIs. They lasted around 23,000 miles. I never even rotated them (I didn't care at the time). I myself, personally, would only run them on a 17x7.5" wheelset though. Grip is EXCEPTIONAL, lateral stability and turn in response is fantastic also. They hook up off the line fairly well if I launch correctly. They are a bit "noisy" on the highway but I don't even notice it now.