Best semi slick sizes for my wheels
06-01-14, 07:36 PM
#1
Best semi slick sizes for my wheels
I haven't been updating my build thread but I am preparing my car for track days.
I was going to buy a separate set of wheels and tires for the track but I want to see what I can do with my wheels and stock body before deciding on whether my setup is satisfactory or to go widebody and wider wheels and tires.
At the moment this is what I have and the cars feels a bit understeery on the street but haven't taken it to the track yet:
Front: 18x9.5 +38 255/35
Rear: 18x10 +38 265/35
These are the sizes I thought might be OK at the track:
a) 255/35/18s all around
b) 265/35/18s all around (along with a pair of 18x10 +38 wheels to match the rear)
c) 255/35/18s at front and 295/30/18s rear (closest diameter tires, 10" wide wheels may be too narrow for 295s and not sure if they will rub).
Anyone running similar setup at the track? And what are you experiences with it? Any other tire sizes I should consider?
I am leaning towards option C but if 295s would cause problems then option B would be my next choice. Just need to check with track day regulars before I order semi slicks.
I was going to buy a separate set of wheels and tires for the track but I want to see what I can do with my wheels and stock body before deciding on whether my setup is satisfactory or to go widebody and wider wheels and tires.
At the moment this is what I have and the cars feels a bit understeery on the street but haven't taken it to the track yet:
Front: 18x9.5 +38 255/35
Rear: 18x10 +38 265/35
These are the sizes I thought might be OK at the track:
a) 255/35/18s all around
b) 265/35/18s all around (along with a pair of 18x10 +38 wheels to match the rear)
c) 255/35/18s at front and 295/30/18s rear (closest diameter tires, 10" wide wheels may be too narrow for 295s and not sure if they will rub).
Anyone running similar setup at the track? And what are you experiences with it? Any other tire sizes I should consider?
I am leaning towards option C but if 295s would cause problems then option B would be my next choice. Just need to check with track day regulars before I order semi slicks.
06-02-14, 08:44 AM
#2
What brand/model tire are you planning to use? I would recommend using a tire that's about 1/2 inch smaller than your wheel width to give you a little stretch for sidewall strength. However, if you are looking at rcomps like Hoosiers, those tires can vary almost 1/2 inch even with the same section width number.
Have you used semi slicks/rcomps before? If not, I would suggest starting out with a sticky street tire for a few events and then eventually moving up to a rcomp.
Have you used semi slicks/rcomps before? If not, I would suggest starting out with a sticky street tire for a few events and then eventually moving up to a rcomp.
06-02-14, 10:08 AM
#3
What brand/model tire are you planning to use? I would recommend using a tire that's about 1/2 inch smaller than your wheel width to give you a little stretch for sidewall strength. However, if you are looking at rcomps like Hoosiers, those tires can vary almost 1/2 inch even with the same section width number.
Have you used semi slicks/rcomps before? If not, I would suggest starting out with a sticky street tire for a few events and then eventually moving up to a rcomp.
Have you used semi slicks/rcomps before? If not, I would suggest starting out with a sticky street tire for a few events and then eventually moving up to a rcomp.
At the moment I have Pirelli P-Zero tyres (in the sizes mentioned in OT), they are ok once warmed up but would prefer something like Toyo R888 or Advan A048 etc.
06-02-14, 10:32 AM
#4
Ok, not what I would call semi-slicks, but at least we have a basis now to start. 
If you look at the Toyo R888, in a 295 size, they have a tread with of around 11.2". IMO, not ideal for a 10" rim. The 265 has a tread with around 9.6" which would be good for a 10" wheel. The 255 is basically the same width so you would have to go down a few sizes if you wanted a little stretch on the front 9.5" wheels.
Advan's are about the same width.. IMO in general, a 295 on a 10" wheel is not going to be ideal for track performance. So I would recommend removing that as an option. I wouldn't be bad, but you'll likely not have the sidewall stiffness you might desire.
If you look at the Toyo R888, in a 295 size, they have a tread with of around 11.2". IMO, not ideal for a 10" rim. The 265 has a tread with around 9.6" which would be good for a 10" wheel. The 255 is basically the same width so you would have to go down a few sizes if you wanted a little stretch on the front 9.5" wheels.
Advan's are about the same width.. IMO in general, a 295 on a 10" wheel is not going to be ideal for track performance. So I would recommend removing that as an option. I wouldn't be bad, but you'll likely not have the sidewall stiffness you might desire.
06-02-14, 11:31 AM
#5
Ok, not what I would call semi-slicks, but at least we have a basis now to start.
If you look at the Toyo R888, in a 295 size, they have a tread with of around 11.2". IMO, not ideal for a 10" rim. The 265 has a tread with around 9.6" which would be good for a 10" wheel. The 255 is basically the same width so you would have to go down a few sizes if you wanted a little stretch on the front 9.5" wheels.
Advan's are about the same width.. IMO in general, a 295 on a 10" wheel is not going to be ideal for track performance. So I would recommend removing that as an option. I wouldn't be bad, but you'll likely not have the sidewall stiffness you might desire.
If you look at the Toyo R888, in a 295 size, they have a tread with of around 11.2". IMO, not ideal for a 10" rim. The 265 has a tread with around 9.6" which would be good for a 10" wheel. The 255 is basically the same width so you would have to go down a few sizes if you wanted a little stretch on the front 9.5" wheels.
Advan's are about the same width.. IMO in general, a 295 on a 10" wheel is not going to be ideal for track performance. So I would recommend removing that as an option. I wouldn't be bad, but you'll likely not have the sidewall stiffness you might desire.
http://i28.photobucket.com/albums/c2...S/100_7275.jpg
https://www.rx7club.com/attachments/...-fitment-1-jpg
https://www.rx7club.com/attachments/...-fitment-3-jpg
But I get what you're saying. I will look into 265s for the front with the 9.5" wheels I have or 265s with a new pair of 10" wheels. Just want to get the best possible sizes without having to try 10 different combinations. And start fine tuning the car for my local track.
06-02-14, 11:48 AM
#6
Don't get me wrong, they will work and on the street would be a perfectly fine setup. On the track if you are looking to maximize your performance, you'd want a smaller tire on that size rim. Doesn't mean you couldn't run it, you just may not be getting the most of the tire. If you aren't competing, it may not be that big of a deal.
06-02-14, 02:34 PM
#7
In that case 265s all around would be my best option, 255s are similar in diameter to stock tires but sidewalls are a touch too thin for my liking. Do you know if 265s with 18x10 +38 in front will fit? 255s with 9.5s and rolled fenders seem like the limit without drifter style negative camber...
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06-02-14, 08:52 PM
#8
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In that case 265s all around would be my best option, 255s are similar in diameter to stock tires but sidewalls are a touch too thin for my liking. Do you know if 265s with 18x10 +38 in front will fit? 255s with 9.5s and rolled fenders seem like the limit without drifter style negative camber...
Toyo R888 also makes a 255/35/18 tires, tread width is 9.5". I would run that on the 10" wide wheel. you can easily fit that tire. it would also be a great fitment as the turn in and grip with it being slightly stretched is a great feeling.
some pics of a 18x10 +38 265/35/18 front looks like. I personally would run a 255 35 18, these tires were super cheap when I purchased them....like 600 shipped cheap
so I figured why not. a 265/35/18 front tire is a taller tire and might rub the fender liner a little. nothing to worry too much about it, but does rub a little in the beginning. I vote for the 255/35/18 size all around.
06-03-14, 04:42 AM
#9
My car has a GTX35R, so I was concerned about rear traction at corners. That was the reason I was looking for 295s. But I think there won't be much difference between 255s and 265s if I am to go that way.
Maybe it's the illusion caused by front 255s and rear 265s on my car which makes the 255s look thin and narrow. Also when I drive my car the front feels skittish and understeery due to thinner and harder sidewalls but this may have to do with wider rear tires.
On the contrary Eric's setup looks mighty fat with 255s. This is 255s all around with 10" wide wheels:
Maybe it's the illusion caused by front 255s and rear 265s on my car which makes the 255s look thin and narrow. Also when I drive my car the front feels skittish and understeery due to thinner and harder sidewalls but this may have to do with wider rear tires.
On the contrary Eric's setup looks mighty fat with 255s. This is 255s all around with 10" wide wheels:
06-03-14, 08:05 AM
#10
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My car has a GTX35R, so I was concerned about rear traction at corners. That was the reason I was looking for 295s. But I think there won't be much difference between 255s and 265s if I am to go that way.
Maybe it's the illusion caused by front 255s and rear 265s on my car which makes the 255s look thin and narrow. Also when I drive my car the front feels skittish and understeery due to thinner and harder sidewalls but this may have to do with wider rear tires.
On the contrary Eric's setup looks mighty fat with 255s. This is 255s all around with 10" wide wheels:
Maybe it's the illusion caused by front 255s and rear 265s on my car which makes the 255s look thin and narrow. Also when I drive my car the front feels skittish and understeery due to thinner and harder sidewalls but this may have to do with wider rear tires.
On the contrary Eric's setup looks mighty fat with 255s. This is 255s all around with 10" wide wheels:
I have a GT3574R and don't have any problems with traction, although I am 6,500ft above sea level.
Going wider actually hurts traction. you are changing the contact patch from more portrait to landscape.
If you want to get better traction I would go with this set up.
255/35/18 front tire on a 18x10" wheel, in the rear go with a 17x10 +38 255/40/17 and lower PSI. cheaper on tires as well, you have better traction in the rear with a portrait tire contact patch, and you have great grip in the front with a slightly stretched tire on an 18" wheel.
06-03-14, 12:07 PM
#11
Maybe it's the illusion caused by front 255s and rear 265s on my car which makes the 255s look thin and narrow. Also when I drive my car the front feels skittish and understeery due to thinner and harder sidewalls but this may have to do with wider rear tires.
On the contrary Eric's setup looks mighty fat with 255s. This is 255s all around with 10" wide wheels:
On the contrary Eric's setup looks mighty fat with 255s. This is 255s all around with 10" wide wheels:
What is your current suspension setup and alignment if you are having understeering tendencies? Is the understeering on corner entry, apex or track out?
I will say that I find it odd that you mention the understeering tendency, yet you are contemplating putting "more" rubber in the rear.
06-03-14, 03:48 PM
#12
I have a GT3574R and don't have any problems with traction, although I am 6,500ft above sea level.
Going wider actually hurts traction. you are changing the contact patch from more portrait to landscape.
If you want to get better traction I would go with this set up.
255/35/18 front tire on a 18x10" wheel, in the rear go with a 17x10 +38 255/40/17 and lower PSI. cheaper on tires as well, you have better traction in the rear with a portrait tire contact patch, and you have great grip in the front with a slightly stretched tire on an 18" wheel.
Going wider actually hurts traction. you are changing the contact patch from more portrait to landscape.
If you want to get better traction I would go with this set up.
255/35/18 front tire on a 18x10" wheel, in the rear go with a 17x10 +38 255/40/17 and lower PSI. cheaper on tires as well, you have better traction in the rear with a portrait tire contact patch, and you have great grip in the front with a slightly stretched tire on an 18" wheel.
06-03-14, 04:02 PM
#13
Within reason, a 9.5" wheel is going to look like a 9.5" wheel regardless of the tire size. So yes, even the same tire is going to "look" bigger on a bigger wheel (i.e. the 10" wheel on the other car).
What is your current suspension setup and alignment if you are having understeering tendencies? Is the understeering on corner entry, apex or track out?
I will say that I find it odd that you mention the understeering tendency, yet you are contemplating putting "more" rubber in the rear.
What is your current suspension setup and alignment if you are having understeering tendencies? Is the understeering on corner entry, apex or track out?
I will say that I find it odd that you mention the understeering tendency, yet you are contemplating putting "more" rubber in the rear.
I have SuperPro and Mazdaspeed/Mazda Comp bushings on order.
The understeer oh the street happens on tighter corners on corner entry or when I start accelerating, front side of the car is pushed out of the corner like front tires just dont hook up.
The wider rear tire question was for traction and sizing question was for both avoiding understeer and track performance but you are right they are all related and got a little mixed up in the topic.
I know I can get around the handling issues in many ways like sway bars, wheel allignment, wider body/tires etc. Just thought more track oriented tyres like R888s are a good place to start since I already need them. I am just trying to get the correct sizes since some of you guys have plenty of track experice with the rx7.
06-03-14, 06:33 PM
#15
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Typical set up for most cars is whatever the weight distribution is on the car, that should be roughly what you run tire wise. I say roughly because you can vary a little in either direction based off what set up you created.
an rx7 is 50/50 weight distribution, so a square set up works well. Porsche's run wider rear tires because they are closer to a 40/60 weight distribution. I think on some models due to the really high WHP, they run even wider rear tires to promote a little understeer from factory.
If you lose traction going straight line, typically draggers run the widest tire they can get to temperature, they also run the smallest wheel diameter, they deflate the PSI and gain the portrait landscape tire patch for better traction forward.
A 295 width on an 18" wheel actually hurts straightline traction, because you just changed the contact patch to a skinny wide patch, and you cannot lower the PSI due to the small sidewalls, and they typically are stiff sidewalls, but 295's do amazing when you start turning, and you can put the power down better going around a turn. trade offs.
this is what I mean by lowering PSI and gaining contact patch.
Pressure
skinny tire vrs. wider tire
wide vrs. skinnier wheels with same tire width
an rx7 is 50/50 weight distribution, so a square set up works well. Porsche's run wider rear tires because they are closer to a 40/60 weight distribution. I think on some models due to the really high WHP, they run even wider rear tires to promote a little understeer from factory.
If you lose traction going straight line, typically draggers run the widest tire they can get to temperature, they also run the smallest wheel diameter, they deflate the PSI and gain the portrait landscape tire patch for better traction forward.
A 295 width on an 18" wheel actually hurts straightline traction, because you just changed the contact patch to a skinny wide patch, and you cannot lower the PSI due to the small sidewalls, and they typically are stiff sidewalls, but 295's do amazing when you start turning, and you can put the power down better going around a turn. trade offs.
this is what I mean by lowering PSI and gaining contact patch.
Pressure
skinny tire vrs. wider tire
wide vrs. skinnier wheels with same tire width
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