My XR, as per Loren's request
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My XR, as per Loren's request
From the other thread:
To save the time of navigating your way to my fquick page, here are a summary of the XR's specs:
wet curb weight w/driver: ~3400 lbs.
power: 215 rwhp / 240 rwtq
Engine:
mostly stock 2.3T
.60/.48 T3 Cosworth turbo
FMIC, BOV, MBC
mildly ported head, ported/gutted intakes, mildly ported turbo manifold
3" full exhaust
Turbocoupe LA3 ecu, "big" VAM.
Drivetrain:
stock T9 5 speed
3.15 geared LSD diff w/custom cradle
Suspension & chassis:
urethane bushings front & rear
stock IRS with solid mounted diff & solid mounted beam
Spax -25mm springs, Spax adjustable dampers
Rapido 28.5mm front / 19mm rear sway bars
JVAB front discs (11.3" x 1.25" two-piece rotors, Wilwood 4 piston calipers)
SSBC rear disc conversion
OMP front strut brace
Wheels & tires:
16x7 ET35 ARE 5 stars (16.5 lbs), 205/45/16 Yokohama AVID H4s
17x7 ET45 Team Dynamics PR2s (16.3 lbs), 215/40/17 Continental ContiExtremeContacts
15x7 ET20 Enkei 92s (14.8 lbs), 205/50/15 Khumo V700s (well abused)
Whatcha think Loren?
I've debated going to race rubber for my XR for auto-x events, but have kept running street tires (whatever's on the car is what I run). Truth be told, I'm not all that good a driver IMHO, but I feel that I'm kinda fighting a losing battle with street tires on the XR simply because I really can't get that big a tire under the car to handle the size/weight of the car and amount of power it's making (215s are about the max without going to coilovers and rolling/cutting fenders). So what to do? Dial back the power? Strip out the interior? Drop the coin for coilovers? Cut the fenders? Or maybe just get some stickier tires under the thing? For the time being, I've decided to run something a bit stickier than the 400 tread rated Continentals.
I might just do that. But I really only mentioned my situation as more fodder for this discussion. My point being that a 205/50 street tire on a Miata is not the same as a 205/50 street tire on my XR (though that is what I'll run when running a set of 15s). If all things were equal in terms of having tires that performed at the same level, I suspect I'd need to be running something like a 225 or maybe even a 245 (which some of the more serious auto-x XR owners do) to have comparable traction to that Miata (or Cayman, or M3, or whatever).
BTW, what are we calling street tires anyway? I see folks calling DOT rated R compounds as "street tires", but to me those things are way too close to being dedicated race compound tires. So when I hear folks saying "I run street tires", I wonder what that really means. I figure once the tread rating gets below 200, you're in race tire territory. Am I wrong?
BTW, what are we calling street tires anyway? I see folks calling DOT rated R compounds as "street tires", but to me those things are way too close to being dedicated race compound tires. So when I hear folks saying "I run street tires", I wonder what that really means. I figure once the tread rating gets below 200, you're in race tire territory. Am I wrong?
Can't even make a comparison between your car and a Miata without knowing what specific vintage of Miata you're talking about (I'm pretty familiar with Miatas, so I could fill in those blanks) and without knowing the details of your car (which I'm too lazy to look up, and your car probably has significant mods in a few areas).
For their Street Touring autocross classes, SCCA calls a street tire anything with 140 treadwear or greater. Many clubs go with that. Some don't. The 24 Hours of LeMons race series uses 190 as their lower limit.
Most people agree that a DOT rating doesn't really make a tire a "street tire", regardless of the fact that SCCA allows any DOT approved tire to compete in their Stock autocross classes or in Showroom Stock for road racing.
DOT "R tires" aren't just "close" to being dedicated race tire compounds, they ARE. But, tire tech has taken major strides in the past 5 years or so. The Falken Azenis was the shit 10 years ago. It was an awesome "real" street tire. Now, there are tires that are WAY grippier and better than that, and some of them even have treadwear of 200 or greater. (Star Specs are rated 200, I believe)
Of course, while the current crop of ultra high performance street tires is probably faster than R tires were 15-20 years ago... the R tires have gotten better, too. On a 60-second course, there's probably at least a second's difference between the average R tire and an similarly sized "top tier" street tire. 2 seconds if the R tires are Hoosiers and the car is well-driven.
For their Street Touring autocross classes, SCCA calls a street tire anything with 140 treadwear or greater. Many clubs go with that. Some don't. The 24 Hours of LeMons race series uses 190 as their lower limit.
Most people agree that a DOT rating doesn't really make a tire a "street tire", regardless of the fact that SCCA allows any DOT approved tire to compete in their Stock autocross classes or in Showroom Stock for road racing.
DOT "R tires" aren't just "close" to being dedicated race tire compounds, they ARE. But, tire tech has taken major strides in the past 5 years or so. The Falken Azenis was the shit 10 years ago. It was an awesome "real" street tire. Now, there are tires that are WAY grippier and better than that, and some of them even have treadwear of 200 or greater. (Star Specs are rated 200, I believe)
Of course, while the current crop of ultra high performance street tires is probably faster than R tires were 15-20 years ago... the R tires have gotten better, too. On a 60-second course, there's probably at least a second's difference between the average R tire and an similarly sized "top tier" street tire. 2 seconds if the R tires are Hoosiers and the car is well-driven.
True enough. Not being able to compare my car with XYZ is exactly right, even though we may in fact be running the exact same tire. Right now I'm planning to run street tires again (205/45/16 Yokohama H4s) at the next auto-x I do in December (with GCAC).
(I'm not sure what specs you might want, but you can probably find what you might wanna see by clicking my signature pic.)
Ah... there's that magic traction fairy dust Hoosier uses at work.
(I'm not sure what specs you might want, but you can probably find what you might wanna see by clicking my signature pic.)
Ah... there's that magic traction fairy dust Hoosier uses at work.
wet curb weight w/driver: ~3400 lbs.
power: 215 rwhp / 240 rwtq
Engine:
mostly stock 2.3T
.60/.48 T3 Cosworth turbo
FMIC, BOV, MBC
mildly ported head, ported/gutted intakes, mildly ported turbo manifold
3" full exhaust
Turbocoupe LA3 ecu, "big" VAM.
Drivetrain:
stock T9 5 speed
3.15 geared LSD diff w/custom cradle
Suspension & chassis:
urethane bushings front & rear
stock IRS with solid mounted diff & solid mounted beam
Spax -25mm springs, Spax adjustable dampers
Rapido 28.5mm front / 19mm rear sway bars
JVAB front discs (11.3" x 1.25" two-piece rotors, Wilwood 4 piston calipers)
SSBC rear disc conversion
OMP front strut brace
Wheels & tires:
16x7 ET35 ARE 5 stars (16.5 lbs), 205/45/16 Yokohama AVID H4s
17x7 ET45 Team Dynamics PR2s (16.3 lbs), 215/40/17 Continental ContiExtremeContacts
15x7 ET20 Enkei 92s (14.8 lbs), 205/50/15 Khumo V700s (well abused)
Whatcha think Loren?
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I think you're a little under-tired at 205. 225's would fit nicely on your 15x7's... will they clear fenders and suspension?
I think you'd be pretty happy with the tires I put on the front of the Yaris recently: 225/45-15 Hankook RS3. They're legitimate street tires, but would probably hook up as well or better than 205-width V700's. They're that good. A little pricey for street tires, something like $120 each. But, cheaper than race rubber... and nearly as grippy. I can't comment on how well they last, I sold the car they were on after doing two autocrosses.
Why such a tall diff ratio? That's probably not going to be the best choice for autocross... though you'll probably NEVER have to worry about shifting up to 3rd. What's it do, about 70 in 2nd?
Compare to a mild forced induction Miata:
2300# + 200# driver = 2500#
180 hp
13.9# / hp vs your 15.8# / hp
A Miata with that level of power would do okay on 205's, and a little better with 225's.
So, I'd guess that you probably don't need more tire so much for the power that you're making, but more due to the weight of the car. If you want the car to turn, it needs more rubber.
Beyond that, there's a lot of car setup. You didn't mention what your spring rates were or your alignment specs. But, even without worrying about that, between alignment, shock settings, tire pressure and swaybar adjustments (they are adjustable, right?), you've got a LOT of fine tuning available. That can be good or bad depending on how consistent of a driver you are and whether or not you can decide the best adjustments to make.
I think you'd be pretty happy with the tires I put on the front of the Yaris recently: 225/45-15 Hankook RS3. They're legitimate street tires, but would probably hook up as well or better than 205-width V700's. They're that good. A little pricey for street tires, something like $120 each. But, cheaper than race rubber... and nearly as grippy. I can't comment on how well they last, I sold the car they were on after doing two autocrosses.
Why such a tall diff ratio? That's probably not going to be the best choice for autocross... though you'll probably NEVER have to worry about shifting up to 3rd. What's it do, about 70 in 2nd?
Compare to a mild forced induction Miata:
2300# + 200# driver = 2500#
180 hp
13.9# / hp vs your 15.8# / hp
A Miata with that level of power would do okay on 205's, and a little better with 225's.
So, I'd guess that you probably don't need more tire so much for the power that you're making, but more due to the weight of the car. If you want the car to turn, it needs more rubber.
Beyond that, there's a lot of car setup. You didn't mention what your spring rates were or your alignment specs. But, even without worrying about that, between alignment, shock settings, tire pressure and swaybar adjustments (they are adjustable, right?), you've got a LOT of fine tuning available. That can be good or bad depending on how consistent of a driver you are and whether or not you can decide the best adjustments to make.
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Part of problem I'm facing is that as with most cars, my XR is a compromise in many ways (budget, expectations, usage, appearance, etc.), which in turn compromises its ability to excel at any one thing. For example, as it sits, I can (and do) put the kids' seats in it and do daily driver duty or take to a local cruie/meet/show, then take it auto-x'ing (or rally-x'ing) in the exact same configuration, including not even swapping tires. Being a pragmatist, I've always sorta been a run-whatcha-brung kinda guy. It's only recently that I've considered doing something like running different tires for an event. I'm pretty realistic that I'm never going to be super competitive (especially based on the kinds of mods I've done and SCCA's classifications), but I'd like to get the most out of the car and the experience.
With regard to suspension setup, I've got some adjustability in it, but not much. The dampers are single adjustables (like Koni yellows). Front camber & toe are set to 1.5* negative, 1/8" toe-in, though the arms are not adjustable themselves. Same with the rear... shims is the only choice, currently set to ~2.5* negative, ~1/4" toe-in. The sway bars are not adjustable. The Spax spring rates are progressive rate, but the actual rates are unknown as Spax doesn't publish them.
All of that said, you're right that there is room to work with the dampers and tire pressures. I actually haven't had much time tuning this particular set up since getting it installed just before moving from Seattle 18 months ago. Also, since I've always been a run-whatcha-brung guy, I'm still learning about making on-the-spot changes to improve things... I haven't been all that successful so far. However, with previous suspension setups that I was running with similar spring rates camber/toe settings, and sway bars, but no adjustable dampers, I was able to wheel the XR to be semi-competitive on street tires (usually mid-pack). I honestly think the car has much more potential that I have ability to show.
As for the diff ratio, it was a decision made based on time constraints; I couldn't source a 3.91 diff in the time I had available to do the diff converison. And actually, it will hit 80 in 2nd before hitting redline, and is mathematically geared to do 189mph in 5th at redline. Great for cruising I75 where it loafs along at 80mph@2850rpm, but I find myself in first or downshifting to first at auto-x and the recently rally-x event. Otherwise, if I short shift it, it falls out of boost (sub 2800rpm). I do now have a 3.91 diff and will be swapping it in (when I get the time), which should make a huge amount of difference in both driving events and generally having fun.
You can actually, but it's not simple, easy, or cheap. If you're willing to let the tires stick out of the fenderwells and run springs hard enough to essentially eliminate suspension compression, you're probably good to go. Or you can run coilovers and roll and pull the fenders a good bit. In fact, there are a couple folks running 275s now, but they do stick out. And there is a nationally competitive DSP XR that took the DSP National Championship in 2009, and he was running 225/40/17s in front and 285/35/18s in the rear. But that car is heavily modified, on coilovers, with bolt on flares, and the tires still stuck out a hair:
The trick for me is that I'm trying to make the car do a bit of everything semi-competently; though the daily driver aspect is becoming much much less important. My plans are to eventually go with a set of custom JVAB coilovers, adjustable front arms, reinforced beam, relocate the rear shock mounts, maybe convert the fronts to a compression strut design, a 6 point roll bar/cage, and a couple other mods. I really want something that can handle the kind of rough stuff I might find in stage rally, but will also handle an auto-x and street duty (if I want). A tall order, but I think I can make it work with good choices and a compromise of expectations.
With regard to suspension setup, I've got some adjustability in it, but not much. The dampers are single adjustables (like Koni yellows). Front camber & toe are set to 1.5* negative, 1/8" toe-in, though the arms are not adjustable themselves. Same with the rear... shims is the only choice, currently set to ~2.5* negative, ~1/4" toe-in. The sway bars are not adjustable. The Spax spring rates are progressive rate, but the actual rates are unknown as Spax doesn't publish them.
All of that said, you're right that there is room to work with the dampers and tire pressures. I actually haven't had much time tuning this particular set up since getting it installed just before moving from Seattle 18 months ago. Also, since I've always been a run-whatcha-brung guy, I'm still learning about making on-the-spot changes to improve things... I haven't been all that successful so far. However, with previous suspension setups that I was running with similar spring rates camber/toe settings, and sway bars, but no adjustable dampers, I was able to wheel the XR to be semi-competitive on street tires (usually mid-pack). I honestly think the car has much more potential that I have ability to show.
As for the diff ratio, it was a decision made based on time constraints; I couldn't source a 3.91 diff in the time I had available to do the diff converison. And actually, it will hit 80 in 2nd before hitting redline, and is mathematically geared to do 189mph in 5th at redline. Great for cruising I75 where it loafs along at 80mph@2850rpm, but I find myself in first or downshifting to first at auto-x and the recently rally-x event. Otherwise, if I short shift it, it falls out of boost (sub 2800rpm). I do now have a 3.91 diff and will be swapping it in (when I get the time), which should make a huge amount of difference in both driving events and generally having fun.
The trick for me is that I'm trying to make the car do a bit of everything semi-competently; though the daily driver aspect is becoming much much less important. My plans are to eventually go with a set of custom JVAB coilovers, adjustable front arms, reinforced beam, relocate the rear shock mounts, maybe convert the fronts to a compression strut design, a 6 point roll bar/cage, and a couple other mods. I really want something that can handle the kind of rough stuff I might find in stage rally, but will also handle an auto-x and street duty (if I want). A tall order, but I think I can make it work with good choices and a compromise of expectations.
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BTW, I might be able to fit a 225/45/15 if I find wheels with just the right offset (not an easy feat) and I trim the fiberglass Cosworth arches (which I'm totally willing to do). The V700s were a hand-me-down from my brother's drifting days, so they were free. And I'm not even sure the 15" wheels I have will still fit since I haven't tried them since doing the "big" front disc conversion. I might have to rely on running one of the sets of 16s I have.
I've heard good things about the RS3s, so I will take a good look at them. I had very good luck with a set of 215/45/16 Falken Azenis RT215s I had, which is my metric for comparison, so I'm sure I can find something equally capable. In the mean time, I've also got a set of unmounted 205/40/16 RT615s and Goumba's got some 225/50/16s I hope to pick up soon, so I may try running those in the near future.
I've heard good things about the RS3s, so I will take a good look at them. I had very good luck with a set of 215/45/16 Falken Azenis RT215s I had, which is my metric for comparison, so I'm sure I can find something equally capable. In the mean time, I've also got a set of unmounted 205/40/16 RT615s and Goumba's got some 225/50/16s I hope to pick up soon, so I may try running those in the near future.
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I don't mind if the tires stick out a bit. I do mind limiting suspension travel though. Too much body roll in turns is bad. Very little suspension travel is also not good in my opinion. I really haven't measured up my xr or researched wheel and tire sizing. I'll have a game plan before I start working on it though.
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Unless there's something weird about your car, I would suggest a bit more front camber. The alignment you have sounds like one that would keep the back end planted solidly. Ample camber and lots of toe-in. The rear should be rock stable all the time... and the front will likely push badly at the limit. Does that sound about right?
More front camber. Less rear toe if you can get it. You really only need enough rear toe in to be able to say that you have some. 1/16-1/8" is plenty. Same with the front toe, really. If the car isn't bad about being twitchy (the Yaris was), you can even try zero toe in front.
That and some tires, set the shocks on the soft side and start playing. Don't get too wrapped up in what you can change on the car. If you keep changing things all the time, you end up chasing a moving target as a driver. You'll have a really hard time figuring out how to drive it if it's different every time!
Goumba, repeat after me: "Body roll is not all bad". The body roll itself is almost NEVER the problem. Check your shocks. Worn out shocks or shocks that are just plain crappy shocks from the factory are usually the problem. Some of the best handling cars in the world (look at a stock Miata or an Elise) have really soft springs and LOTS of body roll. They just have good shocks to keep that body roll well-controlled.
More front camber. Less rear toe if you can get it. You really only need enough rear toe in to be able to say that you have some. 1/16-1/8" is plenty. Same with the front toe, really. If the car isn't bad about being twitchy (the Yaris was), you can even try zero toe in front.
That and some tires, set the shocks on the soft side and start playing. Don't get too wrapped up in what you can change on the car. If you keep changing things all the time, you end up chasing a moving target as a driver. You'll have a really hard time figuring out how to drive it if it's different every time!
Goumba, repeat after me: "Body roll is not all bad". The body roll itself is almost NEVER the problem. Check your shocks. Worn out shocks or shocks that are just plain crappy shocks from the factory are usually the problem. Some of the best handling cars in the world (look at a stock Miata or an Elise) have really soft springs and LOTS of body roll. They just have good shocks to keep that body roll well-controlled.
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I agree that not all body roll is bad. I wasn't trying to imply that it was. I was baisicly getting at the point of the correct spring rate for an application. Too stiff allows little travel. On the opposite end, too soft you get too much squat, dive, and roll. Since one of the concerns here is rubbing under mostly roll, I didn't bother to mention squat and dive. If I am to set my car to allow the suspension to travel a decent amount, of couse I'm going to expect a certain amour of roll. That's especially good in order to transfer weight on the loaded outside wheels for extra grip. I am completely aware of all this. When tire clearence is an issue, too much roll/travel is obviously bad. Also, I don't like long tranition time in slaloms and things of the sort. Proper damping of a spring/corner is always a must. I think that damping is way too overlooked and underrated by the masses.
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Loren, you talk like a guy who knows stuff... I like that. You're absolutely right about about figuring out how to drive it if it's different every time; that's exactly what I've been up against the last 4 or 5 times I've taken it out. For better or for worse, I keep coming back to the fact that the way I know how to drive it fastest is how it's set up 99% of the time: for the street.
BTW, I just double checked the camber/toe settings and adjustability. I apparently mentally blocked out that the front camber & caster are not adjustable actually, even with shimming (which is why adjustable arms are high on my priority list). Basically, camber is determined by arm length and ride height (i.e. lowering springs increase negative camber). So to increase the current 1.5* negative camber would require cutting the front springs, which I was considering doing anyway. This might explain why the car felt more responsive with the previous -45mm springs.
But, I have to say that the car is actually pretty darn neutral as is, with maybe just a touch of understeer. But by firming up the rear dampers, I was able to make downright (snap) oversteer happy, successfully spinning on every run at the last GCAC auto-x event. The car will go where pointed, and when the gearing is right any understeer is easily corrected with a bit of extra throttle or re-applying the weight transfer (with a little steering wheel giggling). I think a bit more front camber would be welcome, and I think I could afford to lose some rear toe-in without consequence. I like a little toe-in for stability at highway speeds, 70-90mph, as I do drive I75 often and for moderate distances (60-100 miles).
BTW, I just double checked the camber/toe settings and adjustability. I apparently mentally blocked out that the front camber & caster are not adjustable actually, even with shimming (which is why adjustable arms are high on my priority list). Basically, camber is determined by arm length and ride height (i.e. lowering springs increase negative camber). So to increase the current 1.5* negative camber would require cutting the front springs, which I was considering doing anyway. This might explain why the car felt more responsive with the previous -45mm springs.
But, I have to say that the car is actually pretty darn neutral as is, with maybe just a touch of understeer. But by firming up the rear dampers, I was able to make downright (snap) oversteer happy, successfully spinning on every run at the last GCAC auto-x event. The car will go where pointed, and when the gearing is right any understeer is easily corrected with a bit of extra throttle or re-applying the weight transfer (with a little steering wheel giggling). I think a bit more front camber would be welcome, and I think I could afford to lose some rear toe-in without consequence. I like a little toe-in for stability at highway speeds, 70-90mph, as I do drive I75 often and for moderate distances (60-100 miles).
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A little bit of rear toe-in is good. But I think 1/4" is "a lot". You don't need that much.
If getting more front camber is difficult, try reducing the rear camber to find balance.
I wouldn't cut the springs or otherwise lower the front more than it already is. It's likely that your spring rates are probably already too low for your reduced ride height. But, consider this...
If you have -1.5 degrees of static camber and your suspension gains a 1/4 degree negative for every inch of compression... if you have 3" of suspension travel left, when you're cornering hard right now, you have -2.75 degrees of dynamic camber.
If you LOWER the car by another inch, you're at -1.75 degrees of static camber. Great. But, you've gained NOTHING at full cornering load. You'll still have the same maximum dynamic camber. Cutting the springs would gain you nothing in that regard.
Sounds like you might be pretty close to balanced, though. Maybe leave the alignment alone and play with shock settings some more. Don't go for perfection, just for consistent and predictable. Find something that works "well enough" and then leave it alone for at least a few events. If you're able to get the car to go from understeer to oversteer by just adjusting the rear shocks, you're probably in good shape... just need to tweak the shocks.
That, or your tires completely suck and you're just fooling yourself.
If getting more front camber is difficult, try reducing the rear camber to find balance.
I wouldn't cut the springs or otherwise lower the front more than it already is. It's likely that your spring rates are probably already too low for your reduced ride height. But, consider this...
If you have -1.5 degrees of static camber and your suspension gains a 1/4 degree negative for every inch of compression... if you have 3" of suspension travel left, when you're cornering hard right now, you have -2.75 degrees of dynamic camber.
If you LOWER the car by another inch, you're at -1.75 degrees of static camber. Great. But, you've gained NOTHING at full cornering load. You'll still have the same maximum dynamic camber. Cutting the springs would gain you nothing in that regard.
Sounds like you might be pretty close to balanced, though. Maybe leave the alignment alone and play with shock settings some more. Don't go for perfection, just for consistent and predictable. Find something that works "well enough" and then leave it alone for at least a few events. If you're able to get the car to go from understeer to oversteer by just adjusting the rear shocks, you're probably in good shape... just need to tweak the shocks.
That, or your tires completely suck and you're just fooling yourself.
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