TRD Wheels on a 2018 BRZ

[fatoni]

Okay. I'll listen to you two guys. Ignore professional opinion and local track times and stick with narrow wheels that may be staggered or taller because that's how you go fast.

[rvoll]

Originally Posted by fatoni

Okay. I'll listen to you two guys. Ignore professional opinion and local track times and stick with narrow wheels that may be staggered or taller because that's how you go fast.

Oversimplification is the enemy of rationality in this case. If you talk to any good "professional" worth their salt, they will tell you to set your objective and then get a tire/wheel combo that meets your needs from a performance perspective. I've done a lot of tracking and will tell you that wider rims with sticky tires will do better most of the time on the track, but not all of the time. Tires change the handling characteristics of cars. OE tire widths are more maneuverable. It's a trade-off between size and shape of the contact patch vs. contact pressure (i.e., lbs per sq in). To do well on the track, you can get too wide of a tire and lose handling capability. I've done that and it is worse than terrible. After a certain point, track times decrease with wider tires. Now if you do go with wider tires with lower profiles, then you should also change the suspension because you can't get the best out of that combo without stiffening the suspension.

You don't seem to take into account that tracking a car is much different than driving a car on the street. When I tracked my cars, I had a different wheel/tire combo for the track than on the street. I rarely got more than 8,000 miles of use on track tires driven on the street given the softer compound. There comes a point when the contact pressure becomes so light you lose traction. So wider is not always better -- that's an oversimplification.

The BRZ is a light car and thus the loss of contact pressure with wider tires is problematic. Most professional don't recommend a tire more than 10% wider than stock for use on the street because it changes the handling characteristics of the car and makes the car less safe. That said, at the track, I would go with wider and stickier tires on dry pavement because sticky rubber enhances the lateral friction thereby allowing more g's on turns. That said, it actually slows straightaway speed due to friction and wind resistance.

This is a complicated topic and most of us do not have the resources to do research on a specific car. However, the BRZ/86 is an extremely well balanced car as it is and you do lose balance when making any significant changes to the handling characteristics. For street use -- even if aggressive -- putting on very wide tires does not enhance the driving capability or experience and you lose mpg in the balance. I've found that the most important change you can make is the choice of tire for you specific purpose. For example, if you live in an area that rains a lot, you don't want extra wide tires but you do want large grooves that disperse the water. Racing tires tend not to have large grooves and you'll hydroplane yourself out of existence.

All of that said, having wide tires on a lowered car looks sexy as long as it is not slammed too much. But it won't do much for your driving experience if you are serious about performance -- and it will eventually turn you into a qualified ricer.

[nikitopo]

Originally Posted by fatoni

Okay. I'll listen to you two guys. Ignore professional opinion and local track times and stick with narrow wheels that may be staggered or taller because that's how you go fast.

Overall, car modifications are quite difficult and there are many parameters. You can try a simple experiment. Drive with the stock tires/wheels, which by the way in my car were the 205/55 R16, and let the car roll with some speed without touching the gas. Then do the same with a good UHP or semi-slick tire. Personally, I have the Advan AD08R's in same dimension. You'll feel that with the sticky tires the car decelerates faster. It is like using a bit the brake. Why do you think that the stock size is not enough and you need more than this? The specific car is not that strong and not that heavy. If I really wanted more grip, then I would go for the new A052's in stock size. I've not seen a single person here using them and they have more grip even from the RE71's. There are many options and there isn't only the option to go larger.

[fatoni]

You guys are talking about a lot of things but wheel width isn't one of them

[nikitopo]

Originally Posted by fatoni

You guys are talking about a lot of things but wheel width isn't one of them

Check the wheel size specifications of the first Boxster's. They had same weight with our cars, same hp output and more torque. Wheel width was 6J × 16 in front and 7J x 16 in rear. You have more than enough wheel width in our cars and with newer sticky tires you can go leaps forward.

[mrg666]

Originally Posted by fatoni

You guys are talking about a lot of things but wheel width isn't one of them

When my car was NA, I switched to 225/45-17 tires on stock rims and that was a big improvement in handling. After FI, 225/45-17 didn't give confidence anymore and 245/40-17 was the solution. Now I have 245/40-17 on 17x8+40 wheels. I feel my car drives so much better and gives so much more confidence. Road handling, grip, acceleration, everything is better. Yeah, it doesn't do drifting easier, and that is a plus too ... for me.

Just leave them alone, there is nothing to prove here.

[nikitopo]

Originally Posted by mrg666

When my car was NA, I switched to 225/45-17 tires on stock rims and that was a big improvement in handling. After FI, 225/45-17 didn't give confidence anymore and 245/40-17 was the solution. Now I have 245/40-17 on 17x8+40 wheels. I feel my car drives so much better and gives so much more confidence. Road handling, grip, acceleration, everything is better. Yeah, it doesn't do drifting easier, and that is a plus too ... for me.

Just leave them alone, there is nothing to prove here.

When your car was NA, did you switch first to same size sticky tires and then to sticky 225s? Or just to the 225s from the primacy's? Going FI is another story. We are talking here about a stock or an almost stock car (e.g., with a header and tune).

[mrg666]

My car had Bridgestone Turanza tires from factory and I directly switched to 225 Yokohama Advan AS. If I am doing again, I would still go with 225 but not Yokohama Advan. Although they were better than stock tires, General G-max AS-05 tires I have right now are much better. For my daily driving I prefer slightly wider AS tire. There is no chance I would even consider going back to 215. I can ask you the same question, have you ever driven your car with 225's? I am sure you didn't.

[nikitopo]

Originally Posted by mrg666

My car had Bridgestone Turanza tires from factory and I directly switched to 225 Yokohama Advan AS. If I am doing again, I would still go with 225 but not Yokohama Advan. Although they were better than stock tires, General G-max AS-05 tires I have right now are much better. For my daily driving I prefer slightly wider AS tire. There is no chance I would even consider going back to 215. I can ask you the same question, have you ever driven your car with 225's? I am sure you didn't.

The Bridgestone Turanza is a standard Touring All Season tire. The Yokohama Advan AS is an Ultra High Performance All Season tire. It makes sense that you saw a difference. About your question if I've tried 225's, I can't because my car came with 205/55 R16 tires. However, there were people that changed these to 215/50 R16. They measured lap times and they didn't find any difference and then they went again back to 205/55 R16. The difference wasn't there even with the "advantage" of the smaller diameter of the 215's. The importance is to compare same tire compounds. If you compare different compounds, then yes you 'll see a difference but not because of the size.

[rvoll]

Originally Posted by fatoni

You guys are talking about a lot of things but wheel width isn't one of them

Wheel width determines the limits of tire size. Go to tire manufacturer specs and it will tell you appropriate wheel sizes for that specific tires. Go outside the bounds of those recommendations, and you could be in trouble. So yes, we are talking about what matters in wheel width. Do your research.

[mrg666]

Originally Posted by nikitopo

The Bridgestone Turanza is a standard Touring All Season tire. The Yokohama Advan AS is an Ultra High Performance All Season tire. It makes sense that you saw a difference. About your question if I've tried 225's, I can't because my car came with 205/55 R16 tires. However, there were people that changed these to 215/50 R16. They measured lap times and they didn't find any difference and then they went again back to 205/55 R16. The difference wasn't there even with the "advantage" of the smaller diameter of the 215's. The importance is to compare same tire compounds. If you compare different compounds, then yes you 'll see a difference but not because of the size.

The stock size is 215/45-17. So did you buy used to get the car with 205/55-16 tires? Anyway, there is a discussion at the following link against your arguments as to why wider tires have better grip although physics laws state that friction doesn't depend on the area. See yourself.

http://www.physlink.com/education/askexperts/ae200.cfm

So it is not only the tire compound but the asphalt surface as well that determines the traction. Grip is better with wider tires on the road with irregular surface. All performance/sports/race/track cars have generally wider tires for this reason. You are reading the wrong sections of internet.

Edit: Of course, if there is not enough power to make use of that extra grip of wider tire, the limited power is wasted. There is an optimal tire width for each car design.

[rvoll]

Originally Posted by mrg666

When my car was NA, I switched to 225/45-17 tires on stock rims and that was a big improvement in handling. After FI, 225/45-17 didn't give confidence anymore and 245/40-17 was the solution. Now I have 245/40-17 on 17x8+40 wheels. I feel my car drives so much better and gives so much more confidence. Road handling, grip, acceleration, everything is better. Yeah, it doesn't do drifting easier, and that is a plus too ... for me.

Just leave them alone, there is nothing to prove here.

I know you don't want to hear this, but many of the changes we make in cars are psychological and not real. I learned this over the years by actually testing alternatives and tracking my sports cars. When I got my first Porsche and brought it to a club track event, they played a newbie game with me to get me indoctrinated. They had me run some timed laps until I thought I was getting the most out of my car. Then they took the car from me and told me that they made some performance adjustments and wanted me to retest the car. Man, the car was amazing and I reduced my lap times. Then they told me they had done nothing to the car and it was all in my mind. I was more aggressive when I thought the car was better.

That said, your anecdotal evidence does not take into account the biggest factor in tires, the rubber compound and tread design. As humans, we are not immune to believing what we've done is better even if it isn't. We tend to reinforce our decisions rather than use rational testing to determine the results. I've done enough tire testing in club events over the years to know the best tires to reduce track times and stopping distances.

If it makes you feel better to drive with extra wide tires on a car that doesn't need it, then go for it. It's your money. But I've put tires on cars that were too wide and track times and stopping distances were reduced. You know, a lot of people think putting on noisy mufflers and CAI's and lowering your car and putting on wide wheels makes your car a lot better. We call them "ricers". But then again, if you get a psychological boost out of doing that, it's far better than taking drugs....

[mrg666]

Originally Posted by rvoll

I know you don't want to hear this, but many of the changes we make in cars are psychological and not real. I learned this over the years by actually testing alternatives and tracking my sports cars. When I got my first Porsche and brought it to a club track event, they played a newbie game with me to get me indoctrinated. They had me run some timed laps until I thought I was getting the most out of my car. Then they took the car from me and told me that they made some performance adjustments and wanted me to retest the car. Man, the car was amazing and I reduced my lap times. Then they told me they had done nothing to the car and it was all in my mind. I was more aggressive when I thought the car was better.

That said, your anecdotal evidence does not take into account the biggest factor in tires, the rubber compound and tread design. As humans, we are not immune to believing what we've done is better even if it isn't. We tend to reinforce our decisions rather than use rational testing to determine the results. I've done enough tire testing in club events over the years to know the best tires to reduce track times and stopping distances.

If it makes you feel better to drive with extra wide tires on a car that doesn't need it, then go for it. It's your money. But I've put tires on cars that were too wide and track times and stopping distances were reduced. You know, a lot of people think putting on noisy mufflers and CAI's and lowering your car and putting on wide wheels makes your car a lot better. We call them "ricers". But then again, if you get a psychological boost out of doing that, it's far better than taking drugs....

Cut the crap man! Drive with your skinny tires as much as you want. My tires are not extra wide, they are as wide as required. Save your stupid stories for yourself.

[rvoll]

Originally Posted by mrg666

The stock size is 215/45-17. So did you buy used to get the car with 205/55-16 tires? Anyway, there is a discussion at the following link against your arguments as to why wider tires have better grip although physics laws state that friction doesn't depend on the area. See yourself.

http://www.physlink.com/education/askexperts/ae200.cfm

So it is not only the tire compound but the asphalt surface as well that determines the traction. Grip is better with wider tires on the road with irregular surface. All performance/sports/race/track cars have generally wider tires for this reason. You are reading the wrong sections of internet.

Edit: Of course, if there is not enough power to make use of that extra grip of wider tire, the limited power is wasted. There is an optimal tire width for each car design.

Of course friction is a related to contact patch, pressure, and compound. However, these physics teachers (not car experts who have done significant testing). They have some assumptions that are just wrong (which proves they don't know a lot about cars). One of these assumptions is that wider tires have softer compounds. If you take the same brand, let's say Michelin Pilot Sports, they use the same exact compound on both narrower and wider tires. They also take a static, rather than a dynamic analysis of tire functionality. Narrower tires heat up more on the track which makes them stickier. Wider tires create more of an air gap between the pavement and tire as the speed increases. Turning a wider tire creates more friction and thus is not as reactive. We call this the law of unintended consequences. (And yes, I majored in math, with minors in physics and chemistry in college.)

I was young once and thought I knew everything. Now that I'm over 70, I've learned that you not only need theory, but you need actual proof that's not based upon human fallibility, but actual results.