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Project S2000: Phase 2, More Grip

By Khiem Dinh

Khiem Dinh is an engineer for Honeywell Turbo Technologies at the time of this writing.  All statements and opinions expressed by Khiem Dinh are solely those of Khiem Dinh and not reflective of Honeywell Turbo Technologies.

"Where has Project S2000 been" do you say?  I've been having fun and driving the piss out of it.  I had completed Phase 1 of the build which was to make a fast, reliable, and uncompromised daily driven street car that could be driven at the track without fear of breaking anything.  Well, the car is no longer my daily driver, so I have decided to commence on to Phase 2.  A Porsche GT3RS is my philosophical car build benchmark.; while it CAN be driven on the street, it's not exactly a car that you would want to daily drive as it introduces compromises to DD duties in order to improve track performance.  Phase 2, Step 1 = more grip and protecting the engine against increased lateral Gs.

The Bridgestone Potenza RE-11s have served me very well as a dual purpose tire.  After four track days, five dozen auto-x runs, and 22k miles, they are toast.  As I now only drive the car about 100 miles a month aside from any track days or weekend canyon cruises, another set of RE-11s would last me anywhere from 10-15 years before I used up the tread. 

I didn't rotate the tires from my last alignment where I increased the rear toe-in to 3/16".  The added toe-in did a number on the inside of the rear tires (also at -2.8 degrees of camber).  The pair of front tires show nearly even wear across the tread even with -2.0 camber and zero toe.  This just goes to show that toe generally kills tires much more quickly than camber.

I imagine the rubber would dry rot before the tread wore out.  So what's the logical course of action? Get stickier tires of course!  Enter the Nitto NT01.

For anyone who has spent time around track days, they know of the Nitto NT01 as the R-compound that can be driven to the track.  If they only last me 5k miles, that's perfect for me.  I opted to go with a tire size of 235/40/17.  Say what?!  But…. But…. But….  Everyone uses 245 or 255 on S2000s!  Let's step back and review for a bit.  I'm running 17x9 Volk RE30s in a +63 offset to maximize fender clearance.  I also chose the Bridgestone Potenza RE-11s in 245/40 to minimize the chance of having to roll the fenders, relocate tabs, mess with the fender liner, etc.  Research said a 255/40 on the +63 would probably only require some minor fender work, but I also planned on getting the StopTech big brake kit on the front.  I knew after researching more, a +53 offset at the minimum would be required in the RE30 wheel to clear the brakes.  Using a KICS 10mm spacer effectively turned my +63 offset wheels into +53.  I added another 3mm spacer as the wheel, while it cleared the calipers, was too close for comfort.  So now I’m effectively at +50 offset which spells a lot of trouble to fit a 255 wide tire.  Sure enough, after installing the StopTechs, I checked the tire-to-fender clearance by taking out the front shock and compressing the suspension until the tire hit the fender.  With the RE-11s in 245/40 size, the shoulder of the tire just touched the tab holding the fender liner.  With some light persuasion with a hammer and 2X4, I bent up the tab a touch just to provide a bit more clearance.

The Nitto NT01 only comes in 235/40 or 255/40.  I knew the 255 would not fit without modifications leaving me with the 235 as the go-to option.  But all is not as bad as it seems.  Why?  My research (there's that word again…) showed that Bridgestone tires are known to run narrow to average width while Nittos are known to run wider.  So how does the 235/40 NT01 stack up with the 245/40 RE-11?

 

They look to be the same width as far as I can tell.  Perfect!

 

 

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Comments
sobe_death
sobe_deathlink
Monday, October 29, 2012 1:00 AM
30 RUNS?! At an Autocross?! How many people normally show up to one of these events?
Slowd16
Slowd16link
Monday, October 29, 2012 5:26 AM
"each wheel has a toe-in of ~0.316 degrees, or a total of 0.632 degrees between the two."
That was a ton of toe in. I have only 0.14 degrees total toe on my s2k and car feels very balanced
spdracerut
spdracerutlink
Monday, October 29, 2012 6:13 AM
@Slowd16, yeah, I think 3/16" is more recommended for AP1s than AP2s. I just got a FSM, and the recommended toe-in on the rear of the AP1 is about double that of the AP2. But, I think a lot of AP2 guys run 3/16" because they go to a non-staggered tire setup and do not adjust the spring rates to compensate. A lot of guys typically just play with sway bars and slap on a big rear wing to keep the rear planted in addition to the rear toe-in.
spdracerut
spdracerutlink
Monday, October 29, 2012 6:32 AM
@sobe, the Speed Ventures auto-x is run somewhat like a test and tune; there is no official timing. The one downside to that is you don't know if peoples' runs were clean or not. So the times I posted in the article are not necessarily all clean. Speed Ventures typically has 3 run groups and run each group for roughly a half hour. So if you stay the whole day, you can typically get in 4-5 sessions. On this day, there were only about 40 cars and the first session only had a handful. DWood went in the first session and basically got in ~10 runs in a row. It's a good thing I have the oil cooler on there with the fan as the car got no cooling airflow in looping right back to the start line. By the second session which I ran, more cars had shown up and I got in around 7 runs or so. If we would have stayed to the end of the day, we probably could have gotten 30-40 runs each. Sometimes, about 80 cars show up which cuts your number of runs in half.
Sootfoot
Sootfootlink
Monday, October 29, 2012 6:38 AM
re- + search = driving the piss out of your s2000 at the track. Awesome fun! I've found similar results comparing various tire sizes. I hope my results are as good as yours!
JDMized
JDMizedlink
Tuesday, October 30, 2012 4:46 PM
Khiem, how about getting wider front fenders since the car now is for track duty? Down force makes some affordable fiberglass fenders....
I kept reading Robert Walker blog a while back (www.maxrev.net) and he kept going back and forth between the 245/255 setup, non staggered.
spdracerut
spdracerutlink
Tuesday, October 30, 2012 8:02 PM
Well, I still drive it once a week to work :) To go to a 255 wide tire, I'd really need to go to a 9.5" wide wheel to optimize the fitment. The nice thing about this tire is the shorter sidewall compared to a 255. With a 255 on this 9" wheel, the sidewalls would bulge a bit. Plus, the sidewalls are already on the soft side. So the taller sidewall on the 255 along with the less than optimal fitment will make it a bit slower to react to steering inputs. Along with over fenders, I'd have to tweak the fender liners too, and the rear tabs. Stuff I don't really feel like dealing with. And up to this point, everything I've done is reversible besides the brake dust shields. Though, I admit, that's going to change.... but anyways, there are other things much higher on my priority list to do and my day job doesn't pay enough to do everything I want to do :)
John
Johnlink
Thursday, November 15, 2012 10:06 PM
Hi, do you run a surge tank in this car at all? or do you just never let it run below 1/4?
spdracerut
spdracerutlink
Friday, November 16, 2012 4:02 PM
I never go below 1/4. Usually, I'll do one more session when at the half tank mark
DaGou
DaGoulink
Wednesday, December 05, 2012 6:11 PM
Hey Khiem, great write up as usual! First I agree, lucky dog to get 30 runs at a Auto-X, everything is better in Cally. 30 runs is like my whole freaking season! Second you have compelled me to get an BlackTrax oil pan. However I am going to have them weld in some bungs for a future supercharger oil return and one for my current catch can. The 235 245 sizes on the two brands blows me away too. I really had no idea some tires run big and some run small. Lastly have you though of a rear diffuser for added down force? I think it is effective, less "ricey" then a big wing, and just more subtle. Alloy Craft makes a nice one that through my "research" does not cost an arm and a leg.
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