heavy85

Replacing bearings in the R200 and see there is no shoulder to press the pinion ball bearing up against. I dont have a FSM so does anyone know how you gauge how far to press the bearing in? PS - I'm installing an OBX at the same time and it's a real POS. Looks like it was machined with a blow torch but that's a different story. PPS - R200 bearings are just about unobtanium Thanks Cameron

I say you need to pick your goals and budget. R compounds will be fast but wear fast and are not very robust to user error (i.e. lockem up and you flatspot them). 140 treadwear street tires are still relatively fast but last forever, give really good driver feedback, and are really quite durable to surviving user error. If this is your first attempt at racing I highly recommend starting on 140 street tires. I used to run slicks - not R comps but true slicks and they feel more numb and easy to flatspot and ruin and they wear fast. Last year I switched to a different class running street tires and am so glad I did. I'm running Bridgestone RE-01 (since been replaced with RE-11) and have ~11 track days, ~5000 street miles, and two parking lot autox on them and they still have something rediculous like 4/32" minimum tread left. I plan to run four more track days then switch to Hancook RS3 street tires for the first race this season. After reading much feedback is seems they are one of the faster street tires and as a bonus are by far the cheapest. Hancook RS3, Bridgestone RE-11, Dunlap Star Spec are all the top end street tires and I'm sure would work well for you. Also need to consider the rules and what class you'll be in. If you have some racing experience and want to be fast the hot ticket is the Hoosier R6 R-compound but expect to spend $$$$$. Cameron

So if short vs long steering arms don't significantly affect ackerman then what are the major advantages of each beyond the obvious fast steering vs easier to steer? Figured this fits here since steering arms control toe. Cameron

Continuing the discussion ... does this mean changing back to the stock length steering arms (vs the shorter one's I have now) would be a good change? Cameron

The calipers are now two years old with about 20 track days on them. I put new seals in roughly halfway though. Both the brand new and now the replacement seals seems to produce the same result. I'm planning to rebuild them again just for preventative maintenance but dont expect this will change anything. I think I'll have to take apart the factory safety valve / tee to see if there is anything inside. Seeing how they bleed just fine it's hard to imagine a restriction could be causing this though. Cameron

If there wasn't a difference why now on two rotors in a row have the right rotor shown much more signs of heat? The left side shows just very minor spider cracking that you have to look close to even see. At this rate I could probable get two seasons, ~20 track days, out of a single left rotor. The right rotors have very visible spider cracks all around plus several large cracks. I'm about to replace the right rotor for the second time due to the larger cracks growing beyond my comfort level. Interesting theory on pad release - I do trail brake a lot but it's hard to imagine that little extra bit of pressure would add that much more heat in the grand scheme of things since pressure and therefore torque and therefore heat generation is relatively low at that point. Cameron

Due to location of bleeder screws the calipers are not the same left to right so you cant swap them. I got the hats for two piece rotors and caliper mounting bracket from I think it was JSK Innovations. I'm using 1 1/4 x 12.75 vented rotors. Interesting that the FR on a typical passenger car is usually worn more but I cant see why it would be that way other than the caliper is further from the master so the lines are slightly longer to the right front than to the left front. I dont see where this would make a difference unless one was plugged. Since I can bleed both it doesn't seem that anything is too plugged. Cameron

It's nothing obvious. I bleed them after every track day so it's not air for sure. Nothing visually wrong with the lines. I actually closely inspect about everything after each track day and I've never seen anything to explain the difference but I've noticed the symptoms for quite a while. Don't think it's pistons because they were recently rebuilt and just by nature of them it's highly unlikely and they acted this way before the caliper rebuild. Only thing I can think of is the factory safety switch / tee block where the front brake lines split. I've never had that apart. What's in it? Cameron

I'm noticing the right front brakes are getting hotter than the left front. This is judged by the burned paint on the spindle on the right vs the unburnt paint on the left plus the left rotor only has very fine spider cracks where the right has many more and they are larger. There is slightly more pad wear on the right but not significant. Most all tracks I run are clockwise so if anything I would think the left front would work harder but that does not seem to be the case. Since I'm in the middle of the winter teardown and detailed inspections I would like to improve this if possible for next year. Up front I'm running Outlaw calipers, vented rotors, and 15/16 master. Any ideas why the right front would be running hotter than the left? Thanks Cameron

I have been thinking more precisely how the car behaves plus watched in-car videos. Here is goes. Typical turn starts by braking hard then ease off while turning in (I tend to trail brake a lot). As soon as it takes a set start to ease on the throttle. Keep easing on the throttle to try to hit the track out point without moving the steering wheel. I can easily modulate the throttle to move the front end around. More throttle and more the front end washes out, less throttle the less it washes out. I typically cant hit WOT until I'm nearly straight. This is if all goes well, if I apply too much throttle too fast the rear steps out dorifto style. In general this is fine and controllable but I think I should be able to hit WOT without having to wait for the wheel to be nearly straight. I dont have THAT much power as it's just a completely stock LS1. This is where I'm thinking more front grip and better diff may help. So any more thoughts on the factory LSD vs the OBX for this application? Obviously throttle will transfer weight off the front tires thus giving them less grip but I think there is a set-up that could perform better in this scenario than what I have now if I could find it. Cameron PS on the debate: back in FSAE in college the rule of thumb was that smaller rims and taller sidewall produced a relatively flat and wide slip angle curve so was very forgiving while bigger rims with shorter sidewall produced more peak grip but with a very narrow range of usable slip angles. We used the small rim combo since we weren't pro drivers. This may also explain some of the reversion in Carrol Smith from the anti-ackerman to ackerman set-up as cars have migrated to larger and larger diameter rims over the years.

Wider rear tires are not in the works at least for now (running the Rota group buy rims) but I'm working on adding a spoiler below the rear wing and some additional front end aero work. Since I have 375 up front I was thinking of swapping those to the rear but then have to decide on rate to replace the front with. Removing the rear bar helped so I dont want to upset the balance too far but I think I really need better front grip. Maybe I'll get excel working and try the magic number spreadsheet ... maybe. I keep thinking about droop limiters and even bought cables last year just haven't had time to try. You have any pics of your droop limiter set-up? As far as the slip angle debate goes I think JohnC is right - it depends. To the best of my reasoning standing in the shower last night I think there are four primary contributors to the 'depends'. 1. Track width. The wider the more ackerman could help do to the smaller 'ideal' diameter the inside tire has to travel. This is probably insignificant in my guess. 2. Radius of the turn. Tighter the radius the more ackerman will help since the relative angle of the inside tire will be more than a larger radius turn. 3. Front end load transfer. The more the load transfer the more the outside tire will be at a higher ideal slip angle than the inside tire favoring less ackerman. 4. Tire's ideal slip angle. Higher ideal slip angle favors less ackerman similar to #3. This may partially explain Caroll Smith change from anti-ackerman to ackerman as bias tires (older technology) favor higher slip angles where radials like a tidier smaller slip angle. Were those Benneton cars on bias or radials back then? Cameron

Not in my experience. Do tell. Rear toe is to help calm the back end down during heavy braking which it does quite well. The front end, well to be honest I've never realized much difference with front toe. It's there due to copycat more than anything. Maybe it's but insensitive butt-o-meter but I've never really found much use for it one way or another. I'm interested to hear in more detail your comments. Thanks Cameron

The LSD seems fine. I just took it out and it's the pinion bearings that are fubar. So I need to replace the bearings for sure but which diff would be the best choice - the factory clutch or the OBX for this applicaion? Also appreciate any thoughts on the spring choices. I run either 245/45-17 RE01 street tires on the Rota group by rims or 15x10 with 23x9.5-15 slicks. Street tires I'm running 2.5 camber front and about 1 rear. Slicks being bias need much less camber about 1.5 / .75. Both were tuned by tire temps and wear. 1/8 toe out front and 1/8 toe in rear. Caster I don't know but I added ~1/2" spacer in the T/C rod to effectively lengthen it and add some caster. 3/4" 'bumpsteer' spacers. Front LCA pivot moved up 5/8-3/4" don't remember exactly. Bumpsteer adjustable tie-rod ends. Some chassis reinforcement (see my pics). I wonder if I can get more front traction that will help as well. Theory is if the oversteer is setup earlier mid turn when the front is pushing then as I add throttle the rear looses side traction (friction circle) and snaps out. It's all bench racing for now as the season in us colder climates doesn't start until April or May. Shoot some ideas at me.

I'm actually fairly happy with how my car behaves now. It's relatively fast and very controllable at the limit. However in the quest for lower lap times I want to make a few changes over the winter break. Already planning some aero mods and time permitting duall masters so now it's time to figure out the rest of the setup. I'm running 375/300 springs big 1 1/8 ish (need to measure) front bar and no rear bar (removing rear bar was a good improvement). Koni 'race' single adjustables and a bunch of other stuff. LS1 powered approx 2600 lb race weight and approx 50/50 dist. The front end pushes at the limit but the back end has a habit of getting squirely putting the power down on track out. Pics show the back end squats at launch and since the rear bar was removed I get quite a bit of rear travel. So I'm thinking of swapping the 375s to the rear and going 424ish in the front. The rear increase to help grip under power by limiting travel and the front increase basically to keep up. My '88 factory LSD is also dead. It still drives fine but is LOUD and goes crunch when I spin he diff. I think it's just the side bearings not the LSD itself but well see. So I'm also considering diff changes while I'm in there. Any opinions on if a gear type (read OBX I'm too cheap for a quaif) diff would help put power down better? Any thought would be good. This is for a track only car. Mostly 2 miles tracks but an occasional trip to Road America. Thanks Cameron

I powdercoated some pieces and they haven't chipped at all. Very durable. Paint sucks but is cheap. Zero rust has worked well on my floorboards but chips very easily in my wheelwells. If it were me I would powdercoat. Locally you can take a box full of parts and for a couple hundred bucks they will strip and powdercoat. Cameron

If you just want wheel bearing replaced it's quite easy. Couple hours at the most but if you want bushings replaced and therefore have to pull the slindle pin it could get painfull. I can't tell you how many hours it took to gouge out the spindle pins but it was a LOT. Cameron

Any update after another year of tuning?

Interesting to hear about the GY being faster. Just to be clear to other readers ... if there are any ... bias ply FA Hoosiers work quite well and last a good long time. They may not be the fastest but do work well, it's just the radial version that I cant get to work. The Avon's were somewhat quicker than the Hoosiers but they were fast last race of '09 then first race of '10 they were utterly worthlessly slow. Just sitting in the garage for 6 months and they went to hell. The Avons are kind of odd tires as the center bulges out - like a balloon - since there's little structure in the center of the tread plus they feel gummy to the touch. Not sticky but more like a pencil eraser. Neither of these causes any issues they just are MUCH different than your typical tire. The 'fast' guys around here all pretty much run A6 both on the racetrack and in the parking lots. I've never tried and A6 so have no direct comparison to the slicks. I was impressed though with how sticky the A6's are as a guy had four tires mounted on rims strapped to his trailer. These were Miata size tires/wheels stacked four high sidewall to sidewall. When he picked up the top tire, the whole stack lifted off the ground. Nothing but the stickiness of the tires was holding them together. We actually had to pry them apart. Now that's sticky! I have noticed that the A6 heat cycle out and loose ~2 seconds on a 1:20 racetrack as they age. I'll have to call Jon Berget in the spring to see if he has any A6 or GY that fit 15x10 rims and give them a shot ... assuming I dont just run street tire class all year again. 140 street tires are fun IMHO if you've never run on them but a heavily modified car has no home for them in most club's rules. Cameron

This is an old thread - my last post three up was over a year ago but while I'm here I'll add. I tried the FA Hoosier Radials again this year after upping springs to 375 / 300 and they lasted 2.5 20 minute sessions before they were trashed with a LOT of cord showing on the outer ~20%. I'm not convinced it's camber control because I had zero issues with bias ply, either Hoosier or Avon, and my RE-01 street tires don't roll over at all. Not sure what it takes to make the Radials work but I haven't figured it out and am giving up trying. Cameron

I bought some acrylic sheet to build a spoiler to add under the wing, now trying to decide 1) how far forward to mount it - it seems the examples I've seen were pretty far back, 2) how long to make it, 3) angle of attack - obviously will be adjustable but need to get to determine where the adjustable range should be, 4) should I just cover the middle or go ahead all the way to the sides? Any more thoughts? I've also decide to lower the front spoiler to keep the air out instead of splitter. Any ideas for material to make it out of? I would like a hard plastic to add onto the existing spoiler. Cameron

Looking at the Porsche example I'm contemplating starting the spoiler at the base of the rear window instead of all the way back on the rear edge. Could easily tie it into the existing wing supports. Maybe match it to the angle of the bottom of the wing? This would all be to help support air getting under the wing plus any side benefit of the spoiler itself. I'm not sure though since the air wasn't (not sure if it is now or not) staying attached I wonder if there just isn't much air down there in the first place due to the shape of the Z? If so VGs may help. Still more pondering to do. Cameron

Studying what little details I could find it looks like the C6.R Corvette GT2 car uses many of the same principles as NASCAR that Jon mentioned. Particularly seeing the airflow over the wheels and shape of the fenders. You can see the 'fender floors' used there as well but I cant tell where they lead to?? http://www.racecar-engineering.com/articles/sportscar/385795/corvette-c6-r-gt2-technical-review.html Cameron PS - I'm really liking the wing + spoiler idea, now need to figure out what that spoiler may look like. My search fu is weak and I cant find the old article where the 'ideal' Z spoiler angle and length was determined. Anyone have a link to that?

Update on the wing. The first year I noticed outside of the mounts it appeared the air was staying mostly attached to the underside. Could tell by the dirty water trails from running in the rain. However the center section appeared to leave spots on the bottom telling me the air wasn't flowing nicely under it. So I made taller extensions. Basically moved the rear ones to the front and made new rear ones to keep the same angle. Also added a 1/2" aluminum angle gurney strip to the top side. My lap times improved this year buts it's hard to say for sure how much the wing adjustments made. During a track day I ran the first session at min angle and the second at max angle. I dropped 1.5 sec off best lap time. Now some may have been the track improved but i'm confident at least some of that was due to steeper wing angle. This is what has me looking more into aero in the other thread. Cameron

Already have a strip in front of front tires but still wonder if the rears even matter in the grand scheme of things. I like the spoiler and wing idea. Never thought of it really. Jon - where have you seen this used effectively? Another way to think of it, short of an effective splitter is there any other practical way to get more downforce on the front end? This is really just a sounding board so keep the thoughts coming. PS - I'll let Jon develop the air damn splitter thingy.

My airdam is relatively low but there is still some air that goes underneath plus brake cooling air that is piped into the wheel needs to go somewhere. Reason it comes to mind is the area behind the front wheels is sloped down under the car with the fender on the side to trap the air and direct it under the floor ... causing lift. At least that's my theory. This is where the blue windtunnel car with the fender liner and skirt angling out would push this air out the sides, creating a negative (relative to air over the top of the car) pressure behind the skirt. I dont know if this would be negative relative to atmosphere but at least lower pressure than air going over the top, creating downforce. This is where a skirt design and / or the floor behind the tires w/ the cut-out in the fender makes a lot of sense to me. The Camaro tank angles up nicely and fills the center of the valence very well, but the sides directly behind the tires are just a direct shot all the way back. This is where I wonder if holes in the valence or fender liners with a lip to trip the air hitting the front side of the rear tires would help get the air out before it 'piles up' in the valence? Maybe it's insignificant, I dont know. Realize this is a balance which is why I asked. I've got the basics covered (wing, airdam, blocked front end, hood vents, etc) but want to take lap times down a notch and think aero may be a cost effective way to make some gains. I'm between 0.3 and 0.5 sec off two separate track records in my class so I'm close but need just a little more. Sure a $1,000 mac daddy wing would trump any of this but that's not real cost effective, at least for what I'm looking for. Cameron