215 or 225 sticky tire for a 7.5x17 wheel?

[Ernest72]

Originally Posted by TommyW

I had a coach at Laguna Seca a couple years ago that had a BRZ and liked the 215’s. I let him drive my car when it had 225’s while I rode right seat. He was due for tires soon and said he was going to 225’s after that.

Understand there are several factors that will determine what tires will work best for each car/driver

That could be old vs new tires. New shoes always feel better.

It’s only 10mm so I think you will be fine with either. I do remember that early on people who went 225 said the car lost some playfulness which means the rear had more grip. So if you want that get 225. But obviously compound of the tire would matter a great deal.

[NoHaveMSG]

Originally Posted by Ernest72

That could be old vs new tires. New shoes always feel better.

It’s only 10mm so I think you will be fine with either. I do remember that early on people who went 225 said the car lost some playfulness which means the rear had more grip. So if you want that get 225. But obviously compound of the tire would matter a great deal.

On the street is one thing, on track it is a little different. Stock the car understeers on turn in and is loose on exit even with the stock tires. Getting alignment setup right you can dial out the understeer through the whole corner and get the car to rotate better then stock even with stickier tires.

[anticubus]

Originally Posted by NoHaveMSG

On the street is one thing, on track it is a little different. Stock the car understeers on turn in and is loose on exit even with the stock tires. Getting alignment setup right you can dial out the understeer through the whole corner and get the car to rotate better then stock even with stickier tires.

Those adjustments are worth it on the street too once the fun wears off a little. As always, the understeer is to keep inexperienced drivers from spinning out in a panic situation. The loose exit is the "playfulness" the reviews rave about, and it's fun but leaves a lot on the table.

Getting an alignment and moving from the stock all-seasons to UHP 225s was the best choice I made for a mostly street driven car, except on those days when my inner 12 year old wishes I could still get a powerslide going under the speed limit.

[ZDan]

Originally Posted by Ernest72

That could be old vs new tires. New shoes always feel better.

New tires at full tread depth will not feel as responsive, worn tires usually feel much better. Particularly for tires that are not "Extreme Performance" category. My Conti ECS felt like crap at the track when new, now at half-worn they're a LOT better... Of course if tires are aged or heat-cycled out, they're going to lose a lot of grip but when and how that happens is very tire-specific. Some tires grip well all the way to the cords.

[Clark20]

Originally Posted by NoHaveMSG

On the street is one thing, on track it is a little different. Stock the car understeers on turn in and is loose on exit even with the stock tires. Getting alignment setup right you can dial out the understeer through the whole corner and get the car to rotate better then stock even with stickier tires.

What alignment specs do you think would be good to help with that turn in understeer? I'm currently running -2 camber in the front and -1.7 in the rear with zero front toe and 1/16 total toe rear. I'm running the Indyhawk 500's but I feel these are great street tires especially for the money. For autocross they don't give nearly enough grip. Im thinking about going for PS4s next or maybe RS4 in 225.

[NoHaveMSG]

Originally Posted by Clark20

What alignment specs do you think would be good to help with that turn in understeer? I'm currently running -2 camber in the front and -1.7 in the rear with zero front toe and 1/16 total toe rear. I'm running the Indyhawk 500's but I feel these are great street tires especially for the money. For autocross they don't give nearly enough grip. Im thinking about going for PS4s next or maybe RS4 in 225.

Tire temp prop is the best way to tell.

I am not a fan of the RS4, their are better options especially for autoX.

[churchx]

Clark20: your alignment already should be much better then stock of 0dg (and -1dg rear) front camber. It's common on these cars to dial by some 0.5dg more front camber then in rear for wished front-rear grip balance. Then again if it's for track or autox use, car may benefit from overall camber increase, eg. -3+ front and -2.5+ rear camber (more precise optimal values using pyrometer). For street only i wouldn't bother past what you have.

[Goingnowherefast]

Both 215 and 225 is a good fit for the wheel. Again like mentioned, the tire make/model/compound is going to be a way bigger factor than width especially for a newer driver. Personally, I'd go with the 225 with a tire like the RT660. The RT660 is a great 200TW tire that's not only budget friendly, but also they communicate very well to the driver and have a very progressive break-away point.

Additionally, the other thing I'd recommend you get a set of camber bolts in the front and max them out. Even with fully maxed out camber bolts, the car is still a bit under-steer'y which isn't a bad thing for a newer driver. Other than that, have fun!

[Clark20]

Originally Posted by churchx

Clark20: your alignment already should be much better then stock of 0dg (and -1dg rear) front camber. It's common on these cars to dial by some 0.5dg more front camber then in rear for wished front-rear grip balance. Then again if it's for track or autox use, car may benefit from overall camber increase, eg. -3+ front and -2.5+ rear camber (more precise optimal values using pyrometer). For street only i wouldn't bother past what you have.

Yeah at this point I think the only thing limiting me from vastly improving my times is my tires. I have KWV3 and raceseng cascam plates so it handles very well. I rode in a friend's car at autocross that had 245 Ps4s and I was blown away with the amount of grip, he was exactly 2.1 seconds faster than me on our best times. So at this point I'm trying to find what would be the best dual purpose tire to run with more grip than the indyhawk. I'm think about getiing ps4 in stock size or someone above mentioned the Rt660. I'm also thinking about getting it corner balanced but I'm not sure if it's worth the price. I was quoted about $650.

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[Jajanken86]

Originally Posted by Clark20

Yeah at this point I think the only thing limiting me from vastly improving my times is my tires. I have KWV3 and raceseng cascam plates so it handles very well. I rode in a friend's car at autocross that had 245 Ps4s and I was blown away with the amount of grip, he was exactly 2.1 seconds faster than me on our best times. So at this point I'm trying to find what would be the best dual purpose tire to run with more grip than the indyhawk. I'm think about getiing ps4 in stock size or someone above mentioned the Rt660. I'm also thinking about getting it corner balanced but I'm not sure if it's worth the price. I was quoted about $650.

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PS4S runs pretty narrow though. If I remember right, at stock size it is 6.8 inches wide. It'll feel really nice and can be playful if you want it to be, but nowhere near the grip it would have at size 245.

[churchx]

In quick sequential lateral transitions in autocross, maybe. On track, especially with stock NA power, 225 might even outperform 245, due lesser weight and rolling resistance. After all, it's not as if grip increases proportional to width increase, as car weight is unchanged, so car will weight down less per area on wider tire, as result contact patch area not changed that much, rather changing shape to that of shorter but wider. Also slight cons of wider tires is increased aquaplaning in wet and price. And that wide tires will benefit from also wider wheels, for tires to not gain much extra sidewall flex if on narrower wheel.
At the end i guess it all depends on priorities/goals. Maximum grip in autocross for sake of competitiveness? Wider tire, if allowed by class rules, might work better. For track & DD with NA car i'd probably go for 225.

[ZDan]

Originally Posted by Clark20

So at this point I'm trying to find what would be the best dual purpose tire to run with more grip than the indyhawk. I'm think about getiing ps4 in stock size or someone above mentioned the Rt660. I'm also thinking about getting it corner balanced but I'm not sure if it's worth the price. I was quoted about $650.

RT660 will be faster than PS4S, as will RE71R and A052.
Unless it's for classification or tire life considerations, I wouldn't bother with PS4S if going faster is the goal.

[ZDan]

Originally Posted by churchx

In quick sequential lateral transitions in autocross, maybe. On track, especially with stock NA power, 225 might even outperform 245, due lesser weight and rolling resistance.

Weight difference between 225/45-17 and 245/40-17 is only about 1 lb. (average for five top Extreme Perf tires, three were 1 lb. heavier in 245, one was 2 lb. heavier, one same weight)

Wider tires don't necessarily have greater rolling resistance, in fact they should have *less* rolling resistance due to less hysteresis from shorter/wider footprint vs. longer/narrower with more deformation. Well known in bicycling. Their problem is wider tires have more aero drag, but this is less true for cars!

I ran 225 and 245 RE71Rs during my 2018 track season, and relative performance vs. consistent benchmarks would indicate there's not much in it either way as far as lap times, with the 225 setup running 40 lb. lighter for same classification points. Unfortunately I have no back-to-back 225 vs. 245 data!

[Clark20]

So a little more information about my car... It's full bolt on E85 and I have the pp wheels wheels which are 7.5. I know if I wanted to get max performance for better times it would be best to get a separate set of wheels with some sticky RE71 or A052 etc... in 245 but for now I only want to have one set of wheels. I've done some research and it seems that having 0.5 narrower tread width than the wheel width is good for feedback/responsive. The Ps4s in stock size have a 6.8 tread width so that is 0.7 narrower than the wheel width. Should I go with the 225 which is a 7.5 tread width or just stick with the 215 which is also the same diameter as stock. How much more grip will I really gain by moving up to 225 and is it worth it in exchange for the driver response and feedback of the 215? Im thinking also that the 225 with take more advantage of the -2 camber I have because more contact patch.