Ride height: Positive Rake vs. Negative Rake
Jun 13, 2007, 06:11 AM
#46
Let's get back on track guys; the most effective and widely used(autocross/road racing) set up has been 18 x 9.5 allowing you to run 285/35 tires available through the leading r-compound manufacturers(kuhmo Hoosiers). The problem is you have to run spacers in the front to keep your tires from rubbing on the coil perches under heavy loads, as they are (on most common coilovers like Jic,KW,Megans,Ohlins unless you go with shorter front springs) parallel to your tire sidewalls. I know some might argue that you can run 17" or an 18" wheel with perfect offset but at what cost ? One is you would have to go custom and you are also limited by tire size and availability and 285 on shorter 18" tires and stiffer sidewalls is a winner no matter how you look at it. My point is that most succesfull autocrossers have ran the 18 x 9.5 or 10 wheels with the spacers that are required to make them fit(front) with no rubbing without a problem and no failures of bearings under harsh autocross cornering loads and conditions. For the rear no spacers are needed as the fenders are the problem they need to be rolled and pulled in conjonction with some decent negative camber to work. Front spacers 10-15mm have been put to the test without any danger for long period of time street and track on the evo( I, myself have them street/track for almost two years now and so far not a problem) and if it gives you your peace of mind run them only at the track.
Jun 13, 2007, 08:32 AM
#47
Wow...those are some fat-*** tires! I won't be going that big. I know it will give me better traction, but this car is mostly a DD, and occasionally a HPDE machine.
I was thinking of going with the 18 x 9 when enough money comes in, but going with a 255/40/18 size tire. For now, I'll probably go with the stock rim and 245/45/17's. Still not sure on the tire though. Probably the Falkens, but I've also been looking at the Kumho MX, Bridgestone RE050 PP, and even perhaps ADVAN sports.
In general, I'm not wanting to have to roll fenders, or use spacers. Just a preference. I know I won't have the "best" setup for autox, but I'm sure the car will do fine ; )
Getting back to the chassis/suspension talk--I plan on leaving front where it is, getting the whiteline roll center and precision steering kit, and a rear perrin sway bar (25mm).
I was thinking of going with the 18 x 9 when enough money comes in, but going with a 255/40/18 size tire. For now, I'll probably go with the stock rim and 245/45/17's. Still not sure on the tire though. Probably the Falkens, but I've also been looking at the Kumho MX, Bridgestone RE050 PP, and even perhaps ADVAN sports.
In general, I'm not wanting to have to roll fenders, or use spacers. Just a preference. I know I won't have the "best" setup for autox, but I'm sure the car will do fine ; )
Getting back to the chassis/suspension talk--I plan on leaving front where it is, getting the whiteline roll center and precision steering kit, and a rear perrin sway bar (25mm).
Jun 13, 2007, 09:16 AM
#48
That's fine as we all started with DD and progress from there, I was just stating what the common competitive set up requires and spacers were part of it. 18 x 9 would not be a smart upgrade as 285 would not properly fit on them when the competitive bugs finally bites you. On the stocker 255/40 seems like a reasonable street/ track double dutty tire. As far as tire brand is concerned the rt-615 are a cheap performer but the bridgstone are grippier but the toyo ra-1 are a weapon of choice if you are willing to go with dot r-comp that are still reasonably street driveable in summer conditions.
Jun 13, 2007, 09:35 AM
#49
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I'd like to offer some thoughts from a newbie to the CT9A suspension world. Feel free to **** on them, but be gentle...please. 
I've recently lowered my Evo on KW3 coilovers. Before doing so I carefully measured the OEM front and rear ride heights at all four corners. What I found is a consistent F/R ratio of about 1.03 within a hundredth of degree...meaning of course that the front right side of the car sits 1.03 times as high as the rear right side of the car...and visa versa for the left side of the car. When I lowered the car I chose to maintain that ratio with the gut feeling that, after 7+ years of Mitsubishi Evo engineers fine tuning the CT9A suspension on the Mokazaki proving grounds outside Nagoya, maybe they learned something about the dynamics of the car. Yeah sure they're limited to a ride height that lends itself to public roads in all of their international markets, but it's not like the Evo doesn't handle well of the showroom floor. I just chose to keep that stock ratio, knowing that the Evo is a nose heavy car, because of the factory R&D. I'm not opposed to tinkering with the suspension settings, I'm just offering some initial input.
BTW the car handles great. Center roll correction kit is on deck.
I've recently lowered my Evo on KW3 coilovers. Before doing so I carefully measured the OEM front and rear ride heights at all four corners. What I found is a consistent F/R ratio of about 1.03 within a hundredth of degree...meaning of course that the front right side of the car sits 1.03 times as high as the rear right side of the car...and visa versa for the left side of the car. When I lowered the car I chose to maintain that ratio with the gut feeling that, after 7+ years of Mitsubishi Evo engineers fine tuning the CT9A suspension on the Mokazaki proving grounds outside Nagoya, maybe they learned something about the dynamics of the car. Yeah sure they're limited to a ride height that lends itself to public roads in all of their international markets, but it's not like the Evo doesn't handle well of the showroom floor. I just chose to keep that stock ratio, knowing that the Evo is a nose heavy car, because of the factory R&D. I'm not opposed to tinkering with the suspension settings, I'm just offering some initial input.
BTW the car handles great. Center roll correction kit is on deck.
Jun 13, 2007, 10:27 AM
#50
Let's get back on track guys; the most effective and widely used(autocross/road racing) set up has been 18 x 9.5 allowing you to run 285/35 tires available through the leading r-compound manufacturers(kuhmo Hoosiers). The problem is you have to run spacers in the front to keep your tires from rubbing on the coil perches under heavy loads, as they are (on most common coilovers like Jic,KW,Megans,Ohlins unless you go with shorter front springs) parallel to your tire sidewalls. I know some might argue that you can run 17" or an 18" wheel with perfect offset but at what cost ? One is you would have to go custom and you are also limited by tire size and availability and 285 on shorter 18" tires and stiffer sidewalls is a winner no matter how you look at it. My point is that most succesfull autocrossers have ran the 18 x 9.5 or 10 wheels with the spacers that are required to make them fit(front) with no rubbing without a problem and no failures of bearings under harsh autocross cornering loads and conditions. For the rear no spacers are needed as the fenders are the problem they need to be rolled and pulled in conjonction with some decent negative camber to work. Front spacers 10-15mm have been put to the test without any danger for long period of time street and track on the evo( I, myself have them street/track for almost two years now and so far not a problem) and if it gives you your peace of mind run them only at the track.
I run 18x9.5 with 285 Hoosiers. My wheels were custom made specific offsets but I still run 7mm spacers in the front.
I ran 255's for a few years and I also progressed to the 285's. If you race a lot you will most definitely feel the need to run 285's or 275's eventually.
Jun 14, 2007, 06:59 AM
#52
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I'm beginning to have a hard time understanding why everyone is getting jammed up about running spacers. As long as the parts are hubcentric and there is proper lug nut thread engagement (probably 1d (8 threads) to 1.5d (12 threads)) there should not be any major issues.
Think about running wider wheels. Add in a low offset and you are def increasing load on the wheel bearings with just the wheels alone.
I run them on my car for autocross, but have no reason to use them on the street. I've got a couple friends running 1" spacers in the front for quite a few street miles, autox and track events and nobody's had any issues.
Somebody please point us to some actual data/problems. And don't go pointing to that rx-7 thread where all 4 wheels fall off.
Jun 15, 2007, 07:27 AM
#54
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Great info on this thread 
. Running spacers or just getting a rim with an offset that moves the rim center further from the hub is essentially the same difference other than 1 is 1 piece and the other is 2 pieces. Also, a wider rim usually adds more rotating mass which on the front end will worsen the 60/40 ratio, only by a bit but more is definately not better. Running a wider rear tire than the front may help in keeping a little more traction in the rear plus adding an extra few lbs. I plan on adding spacers but not sure is 15mm may cause rubbing issues. I plan on adding spacers front and rear...possibly 15mm front and 10mm rear for a wider track all around.
. Running spacers or just getting a rim with an offset that moves the rim center further from the hub is essentially the same difference other than 1 is 1 piece and the other is 2 pieces. Also, a wider rim usually adds more rotating mass which on the front end will worsen the 60/40 ratio, only by a bit but more is definately not better. Running a wider rear tire than the front may help in keeping a little more traction in the rear plus adding an extra few lbs. I plan on adding spacers but not sure is 15mm may cause rubbing issues. I plan on adding spacers front and rear...possibly 15mm front and 10mm rear for a wider track all around.
Dec 17, 2007, 02:02 PM
#57
You have to make sure (if running springs) your shock valving is appropriate for the lowering spring rates you're about to run. From experience, the stockers(KYB as I do not have any first hand experience with the Bilsteins) are not to happy with stiffer springs and the handling deteriorated although body roll was reduced.
You can not lower much, if any without having a way to correct the roll center that goes underground as a result of the geometry change. So, if you want to lower correctly invest in some roll center correction kit.
Make sure you get a proper alignment after all is done.
Dec 17, 2007, 02:25 PM
#58
Lowering (for handling) is a modification that requires supporting mods just like upgrading a turbo does.
So like Madmax said...if you're going to lower the car...a forward rake will aid with downforce at the front of the vehicle for better turn in, but at the same time if the chassis's geometry isn't correct than you'll do more harm than good (assuming more downforce is something that was originally wanted).
Lower the car, make the car flat relatative to the ground. Upgrade the ball joints, tie rod ends, steering rack position, and perhaps the rear assist link bushings with parts that will correct for the lowered car's new geometry.
So in english, if you're going to lower the car most prefer to do so with coilovers, as opposed to simply using springs. But whichever way better suits you is up to you. Once that has been decided, I would do the front roll center correction kit, the precision steering kit, and the rear bump steer correction kit.
So like Madmax said...if you're going to lower the car...a forward rake will aid with downforce at the front of the vehicle for better turn in, but at the same time if the chassis's geometry isn't correct than you'll do more harm than good (assuming more downforce is something that was originally wanted).
Lower the car, make the car flat relatative to the ground. Upgrade the ball joints, tie rod ends, steering rack position, and perhaps the rear assist link bushings with parts that will correct for the lowered car's new geometry.
So in english, if you're going to lower the car most prefer to do so with coilovers, as opposed to simply using springs. But whichever way better suits you is up to you. Once that has been decided, I would do the front roll center correction kit, the precision steering kit, and the rear bump steer correction kit.
Dec 17, 2007, 04:57 PM
#59
Lowering (for handling) is a modification that requires supporting mods just like upgrading a turbo does.
So like Madmax said...if you're going to lower the car...a forward rake will aid with downforce at the front of the vehicle for better turn in, but at the same time if the chassis's geometry isn't correct than you'll do more harm than good (assuming more downforce is something that was originally wanted).
Lower the car, make the car flat relatative to the ground. Upgrade the ball joints, tie rod ends, steering rack position, and perhaps the rear assist link bushings with parts that will correct for the lowered car's new geometry.
So in english, if you're going to lower the car most prefer to do so with coilovers, as opposed to simply using springs. But whichever way better suits you is up to you. Once that has been decided, I would do the front roll center correction kit, the precision steering kit, and the rear bump steer correction kit.
So like Madmax said...if you're going to lower the car...a forward rake will aid with downforce at the front of the vehicle for better turn in, but at the same time if the chassis's geometry isn't correct than you'll do more harm than good (assuming more downforce is something that was originally wanted).
Lower the car, make the car flat relatative to the ground. Upgrade the ball joints, tie rod ends, steering rack position, and perhaps the rear assist link bushings with parts that will correct for the lowered car's new geometry.
So in english, if you're going to lower the car most prefer to do so with coilovers, as opposed to simply using springs. But whichever way better suits you is up to you. Once that has been decided, I would do the front roll center correction kit, the precision steering kit, and the rear bump steer correction kit.
Also, the true point of lowering is taking advantage of lower CG and having less drag and lift is an added bonus not the other way around. Like mentioned before, always raise the RC back above ground.
The other upgrades mentioned in your post, although highly beneficial are not a must when lowering as they are not negatively affected by the lowering as the roll center
.
