AP1, RE-71R, stock sizes or all 225?
06-27-2018, 05:38 PM
#1
AP1, RE-71R, stock sizes or all 225?
Time to order tires and I'm going with the Re-71's. Most of my driving will be back and forth to autocrosses, not a daily driver. Vast majority of events are old airport runways so there is almost always a tight turn around. Huge mix of old asphalt, some new asphalt and old rough concrete. I've only had the car for less than a month with 8 year old 960 run flats so I have no concept of the impact of squaring up the tires vs. staying staggered. Suspension is 100% stock. Any advice is appreciated.
06-27-2018, 06:45 PM
#2
Wow, this is like my 3rd day of adding to and re-using this post in a row. Hope it is helpful.
I had an AP1 in the B Street for the last 2.5 years. I just sold it and bought an AP2 which I haven't gotten to an autocross yet. The car's balance was good and was really fun on stock sizes. 16s are also significantly cheaper than 17s. This is great for focusing on seat time.
I did 205/225's for my first set of RE71R's on the car completely stock. It was a really fun setup and I learned a lot from driving it. I thought the balance was great. I wore them out in about 8k street miles and a bunch of autocross events. If you do not plan to buy a good front swaybar before wearing out that set of tires, I recommend going this way. I also drove on 225 square for a while before buying the sway bar. The setup was fun, forces you to learn to catch oversteer, and teaches you what a "loose" car feels like. It is not bad but is not balanced. More on that below.
All of that being said, the best setup in stock class will be 225/50/16 RE71R's all around with a Karcepts front sway bar. I still suggest focus solely on improving your driving for the first year. As for mods, you will need a bit of driving skill to actually start feeling where you can improve the car.
Buy the front sway bar once you experience the problem that it attempts to solve. I believe you will learn more in the process doing it this way as opposed to throwing parts at it. Drive it stock on good tires, keep it idiot proof. Your only means of tuning are improving your driving and changing tire pressures. I did this for over a year and used known good drivers to measure my progress. Take someone who places at nationals and see how far off you are from them. They will be consistently near the top at local events and should give you a pretty good idea based on the delta between you two. Be honest with yourself. Once you are truly close and/or seriously experience and feel something about the car you want changed, consider making the change. Until then, driving is what will net you the biggest difference and most satisfaction.
If you have enough grip and drive hard enough, you will start to lift the inside rear tire. I drove my ap1 on 225 RE71's all around for a bit before truly experiencing this. I solved the problem by putting on the Karcepts big front sway bar. It was definitely oversteery but taught me a lot and was pretty fun. I think I only spun it once on that setup. I actually didn't realize how much it tended towards oversteer until I got the front bar and wasn't correcting nearly as much. That taught me what a car feels like when it is too loose.
I had an AP1 in the B Street for the last 2.5 years. I just sold it and bought an AP2 which I haven't gotten to an autocross yet. The car's balance was good and was really fun on stock sizes. 16s are also significantly cheaper than 17s. This is great for focusing on seat time.
I did 205/225's for my first set of RE71R's on the car completely stock. It was a really fun setup and I learned a lot from driving it. I thought the balance was great. I wore them out in about 8k street miles and a bunch of autocross events. If you do not plan to buy a good front swaybar before wearing out that set of tires, I recommend going this way. I also drove on 225 square for a while before buying the sway bar. The setup was fun, forces you to learn to catch oversteer, and teaches you what a "loose" car feels like. It is not bad but is not balanced. More on that below.
All of that being said, the best setup in stock class will be 225/50/16 RE71R's all around with a Karcepts front sway bar. I still suggest focus solely on improving your driving for the first year. As for mods, you will need a bit of driving skill to actually start feeling where you can improve the car.
Buy the front sway bar once you experience the problem that it attempts to solve. I believe you will learn more in the process doing it this way as opposed to throwing parts at it. Drive it stock on good tires, keep it idiot proof. Your only means of tuning are improving your driving and changing tire pressures. I did this for over a year and used known good drivers to measure my progress. Take someone who places at nationals and see how far off you are from them. They will be consistently near the top at local events and should give you a pretty good idea based on the delta between you two. Be honest with yourself. Once you are truly close and/or seriously experience and feel something about the car you want changed, consider making the change. Until then, driving is what will net you the biggest difference and most satisfaction.
If you have enough grip and drive hard enough, you will start to lift the inside rear tire. I drove my ap1 on 225 RE71's all around for a bit before truly experiencing this. I solved the problem by putting on the Karcepts big front sway bar. It was definitely oversteery but taught me a lot and was pretty fun. I think I only spun it once on that setup. I actually didn't realize how much it tended towards oversteer until I got the front bar and wasn't correcting nearly as much. That taught me what a car feels like when it is too loose.
06-27-2018, 07:45 PM
#3
^Ditto I saw your comment in a different but very similar thread.
My own version of the monologue:
If you go 225 square you may want a bigger front sway bar. As you may have read, the AP1 is a bit more on the twitchy side even with the stock staggered tire sizes; a combination of higher rear spring rates and sway bar stiffness and greater bump steer in the rear subframe geometry. When you go non staggered you increase the relative front grip which means during high turning forces the rear becomes more likely to lose grip and slide out, leading to more over steer. Depending on driving style and experience I think you may feel the car is perfectly fine without a big front sway bar. I personally don't have experience with 225 square without a big front sway bar so I can't directly comment on that setup however I have some experience with a friend's '01 AP1 B street car (225 square and Karcepts FSB) and my own car is an '00 AP1 with 255 square and stock suspension (half assed STR setup). I personally think my AP1 with 255 square and stock suspension is very predictable and fairly easy to drive. However I have the suspicion that the 255 tires in the rear has toned down some of the twitchiness purely due to significantly increased grip alone. My buddy's B street AP1 still feels a little bit twitchier in the rear than my car even though he is running massively increased front sway bar stiffness. On the other hand, the larger front sway bar means his car is much more responsive in transitions than my car. And on the subject of the 255 rears over powering the twitchiness, where my car was fairly controllable in the dry and warm days, during two really wet and cold autocross days I had the time of my life trying to keep the car straight. I feel that wet and cold conditions exaggerates bad driving with the lower grip. I would say that I could still predict when the rear end was going to come out however it felt like I was constantly fighting the car. I imagine this is actually more extreme than 225 square on stock suspension. So while my experience isn't directly applicable to the setup you're going for, I would imagine it's fairly universal to say that you should expect more trailing/lift off over steer. When you let off the throttle slightly you will feel the front start turning in more and the rear becoming a little lighter. This shouldn't be a sudden transition if you are driving smart. I seem to also have a little bit of on-throttle push. So I'd still say that the attitude of the car is fairly controllable with throttle modulation. The only thing I don't like about my car is the lazziness between transitions, likely because I need a bigger FSB. I also occasionally get that weird kind of turn in over steer if you throw a car into a corner too suddenly and the front feels like it bites and the rear becomes loose. I'd like to say this is usually due to my bad driving (too twitchy and sudden with inputs) but I imagine (and I've been told) a stiffer front sway bar would allow me to get away with this some more due to increased front roll stiffness balancing out the excess front bite/roll and allowing the rear to grip more in turn with the reduced dive.
I would also go with Jub's advice. Start with tires only first. The car isn't absolutely undriveable without the front sway bar but probably will be more punishing. Gradually find the limits of this setup and once you've identified what is working and what you would like to change, then try out the front sway bar to see if you can start pushing a little bit more. For me I was fairly happy with even the stock suspension at first, but as I started to push harder I realized that the front just felt too lazy. This is also probably more prevalent for me since I'm running more tire.
My own version of the monologue:
If you go 225 square you may want a bigger front sway bar. As you may have read, the AP1 is a bit more on the twitchy side even with the stock staggered tire sizes; a combination of higher rear spring rates and sway bar stiffness and greater bump steer in the rear subframe geometry. When you go non staggered you increase the relative front grip which means during high turning forces the rear becomes more likely to lose grip and slide out, leading to more over steer. Depending on driving style and experience I think you may feel the car is perfectly fine without a big front sway bar. I personally don't have experience with 225 square without a big front sway bar so I can't directly comment on that setup however I have some experience with a friend's '01 AP1 B street car (225 square and Karcepts FSB) and my own car is an '00 AP1 with 255 square and stock suspension (half assed STR setup). I personally think my AP1 with 255 square and stock suspension is very predictable and fairly easy to drive. However I have the suspicion that the 255 tires in the rear has toned down some of the twitchiness purely due to significantly increased grip alone. My buddy's B street AP1 still feels a little bit twitchier in the rear than my car even though he is running massively increased front sway bar stiffness. On the other hand, the larger front sway bar means his car is much more responsive in transitions than my car. And on the subject of the 255 rears over powering the twitchiness, where my car was fairly controllable in the dry and warm days, during two really wet and cold autocross days I had the time of my life trying to keep the car straight. I feel that wet and cold conditions exaggerates bad driving with the lower grip. I would say that I could still predict when the rear end was going to come out however it felt like I was constantly fighting the car. I imagine this is actually more extreme than 225 square on stock suspension. So while my experience isn't directly applicable to the setup you're going for, I would imagine it's fairly universal to say that you should expect more trailing/lift off over steer. When you let off the throttle slightly you will feel the front start turning in more and the rear becoming a little lighter. This shouldn't be a sudden transition if you are driving smart. I seem to also have a little bit of on-throttle push. So I'd still say that the attitude of the car is fairly controllable with throttle modulation. The only thing I don't like about my car is the lazziness between transitions, likely because I need a bigger FSB. I also occasionally get that weird kind of turn in over steer if you throw a car into a corner too suddenly and the front feels like it bites and the rear becomes loose. I'd like to say this is usually due to my bad driving (too twitchy and sudden with inputs) but I imagine (and I've been told) a stiffer front sway bar would allow me to get away with this some more due to increased front roll stiffness balancing out the excess front bite/roll and allowing the rear to grip more in turn with the reduced dive.
I would also go with Jub's advice. Start with tires only first. The car isn't absolutely undriveable without the front sway bar but probably will be more punishing. Gradually find the limits of this setup and once you've identified what is working and what you would like to change, then try out the front sway bar to see if you can start pushing a little bit more. For me I was fairly happy with even the stock suspension at first, but as I started to push harder I realized that the front just felt too lazy. This is also probably more prevalent for me since I'm running more tire.
06-27-2018, 08:01 PM
#4
What about the 205/45-16? It is 1" narrower section width, but only 1/2" narrower tread width. But it is 1.7" less in diameter, lowering the car over 0.8". Might scrape over driveways...but may not be slower.
There is a BFG Rival S 1.5 in 215/45-16. It has the same tread width as the RE71r 225/50 but is 1" less diameter lowering the car 1/2".
The car is allowed to use wheels 1" larger or smaller: "B. Wheel (rim) diameter may be increased or decreased 1” from the standard part. This change may be applied to the front, rear, or both axles."
That would let you run 17" sizes on slightly narrower wheels than an AP2. It would also let you run the BFG Rival S 245/40-15. There is also a 225/45-15. If you can find wheels that will clear the brakes, they have little or no penalty in width but are 1.7" to 2.3" less in diameter than what an AP2 would run, lowering the as much as an inch or more.
Seat time rather that trick wheels is probably the right story for 2018 though.
There is a BFG Rival S 1.5 in 215/45-16. It has the same tread width as the RE71r 225/50 but is 1" less diameter lowering the car 1/2".
The car is allowed to use wheels 1" larger or smaller: "B. Wheel (rim) diameter may be increased or decreased 1” from the standard part. This change may be applied to the front, rear, or both axles."
That would let you run 17" sizes on slightly narrower wheels than an AP2. It would also let you run the BFG Rival S 245/40-15. There is also a 225/45-15. If you can find wheels that will clear the brakes, they have little or no penalty in width but are 1.7" to 2.3" less in diameter than what an AP2 would run, lowering the as much as an inch or more.
Seat time rather that trick wheels is probably the right story for 2018 though.
06-28-2018, 04:15 AM
#5
Doesn't a 225 on a 6.5" rim just give terrible feedback? I'm running 245 on a 9" wheel because I was concerned 255's would be too vague. If you do run that set up, you would certainly want a larger bar, but I don't think I would like the turn in response with that wide of a tire on a narrow rim.
06-28-2018, 04:59 AM
#6
As someone who ran a MY00 stock for two years, I'd like to clarify that the early AP1, and probably even the later (02-03) AP1 are factory tuned for understeer, not oversteer. However, the rear suffers from somewhat significant bumpsteer which can make the rear end get loose over bumpy surfaces or sudden front/rear transitions. My point is that you fix rear bumpsteer by changing the rear suspension geometry (rear BSK) or you stiffen the rear suspension to limit toe change. Going to a bigger front bar is only going to add more understeer.
When I got the S2000 I wanted to learn to drive a more neutral to loose car as that seems like the fast way around most tracks - and if you are up for the challenge, then I'd recommend going 225 square. Since you've said you're interested in autocross, so what if you lose the rear end a few times in the beginning as you learn? It's as safe an environment as you'll find. Plus, I think the difference in the overall balance of your car will be less than most think. When I went square to 255 I was worried the car would become loose, but the reality is that it just picked up front grip, especially under braking.
Lastly, this isn't a lifetime decision - it's just a set of tires
Focus on seat time, experiment with suspension settings and tire pressures, and have some fun out there!
When I got the S2000 I wanted to learn to drive a more neutral to loose car as that seems like the fast way around most tracks - and if you are up for the challenge, then I'd recommend going 225 square. Since you've said you're interested in autocross, so what if you lose the rear end a few times in the beginning as you learn? It's as safe an environment as you'll find. Plus, I think the difference in the overall balance of your car will be less than most think. When I went square to 255 I was worried the car would become loose, but the reality is that it just picked up front grip, especially under braking.
Lastly, this isn't a lifetime decision - it's just a set of tires
Focus on seat time, experiment with suspension settings and tire pressures, and have some fun out there!
06-28-2018, 07:27 AM
#7
Doesn't a 225 on a 6.5" rim just give terrible feedback? I'm running 245 on a 9" wheel because I was concerned 255's would be too vague. If you do run that set up, you would certainly want a larger bar, but I don't think I would like the turn in response with that wide of a tire on a narrow rim.
Note that S2000s aren't the pointy end of the spear in B/Street generally, although locally one might be fastest. An an AP1 will always be at a disadvantage to an AP2, especially an AP2v2 which also has EBD, a bigger intake and throttle body, and loses the air pump.
The goal is to have fun and improve your skills. The 225 tires on your OEM rims will be fine. I believe all S2ks benefit in autocrosses from a stiff front bar, and IMHO the Karcepts is the best (and the one I have). When the AP1 is new (I picked up mine in Sept 1999) people autocrossed with either a bigger front bar or large rear tires. The rules were different then as was tire availability in 16" wheel sizes.
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06-28-2018, 03:57 PM
#8
Thanks for the responses. I plan on keeping the car stock for now so it seems like the consensus is staggered and that is what I shall do. Since I need to break the on-off switch gas pedal habit I don't want to loosen the rear of the car at all. The main reason I was thinking of going larger on the fronts is the number of runway sites we use with the always painful turn around that I didn't want to constantly possibly push through.
Although not about tires, but about front bars) I'll hijack my own thread. Instead of a larger front bar I've seen discussion of a using a smaller rear bar (AP 2) or disconnecting the rear. Pros and cons instead of the cost of the larger front bar in the context of no other suspension changes. I promised my wife I wouldn't get crazy like with my prior CSP Miata.
Although not about tires, but about front bars) I'll hijack my own thread. Instead of a larger front bar I've seen discussion of a using a smaller rear bar (AP 2) or disconnecting the rear. Pros and cons instead of the cost of the larger front bar in the context of no other suspension changes. I promised my wife I wouldn't get crazy like with my prior CSP Miata.
06-28-2018, 04:47 PM
#9
Why do you think the consensus is staggered? STR is 255-17 square. B and A Street are typically 245/255 only because 255 won't clear the front fender on Street class rules. I think you will find most track S2000s use a square setup.
06-28-2018, 05:36 PM
#10
IMO non staggered is the way to go with this car, especially autocross. For me the stock AP1 tire sizes felt adequate at first until I found out what I could get away with using a non staggered setup, just all around more turn in. Then I realized the oem staggered setup kind of understeered. The only thing I can say that the OEM tire size does better is maybe a very minutely faster/ more precise steering response. I'd say it's a very small difference and the trade off with wider tires in the front is a firmer steering response which I appreciate. That's also my car with 255 in front. The difference in steering response will probably be minimal with 225s. And while 225 will be kinda pinched and muffin topped on the OEM AP1 front wheel, a good extreme performance summer tire like the RE71R should have stiff enough side walls that it isn't that big of a deal. At least when I drove my buddy's B street AP1 it didn't even cross my mind that the front steering response felt squishy or vague.