85 Citation in C-Mod

[captain_pants]

This thread is about my adventure buying and prepping an 85 Citation FF for C-Mod competition. My original thread was located here: http://www.apexspeed.com/forums/showthread.php?t=72785 The responses in that thread convinced me that this car/class was the right direction for me, so I picked up Sho's (Previously Jim G's) yellow 85 Citation.

The first order of business was getting it home and doing a light sweep over the car for big issues that need to be fixed. I typically have about 2-4 hours a week to work on the car, with a recent big push over the July long weekend. Right away, I noticed that my legs were a good 1-2" longer than Sho's, so sitting in the car meant I was depressing the throttle/clutch unless I pulled my knee/ankle as far back as I possibly could. I could barely get my foot onto the brake pedal, and when I did I couldn't touch very much of the pedal as the steering shaft was so low and close to the brake pedal.

Over the past couple of months, I have:
- Read everything I can find about pedals, steering shafts, Apex joints, solid rivets, and the FAA aircraft repair manual.
- Re-read Carrol Smith's books, which meant a lot more to me now that I'm looking at a Formula car
- Spoken with S. Lathrop multiple times about how things should work and how they were assembled originally. Thanks a ton Steve!
- Bought the thinnest/slimmest shoes I could find, which turned out to be the RJS shoes (which feel like slippers in comparison to most of the other SFI shoes!)

Progress (in no particular order):
- Added spacers between master cylinders and frame mount to move pedals away - temp solution until I have time to make shorter pushrods over the winter
- Removed numerous sharp angle brackets from footwell - used to snag shoes while getting in/out
- Secured oil tank better - was held in by one zip tie, gravity, and a healthy dose of optimism before
- Eliminated chafe-point between left side hard coolant pipe and frame
- Added U-joint to steering shaft above feet and rotated steering rack to suit - allows MUCH more foot room to use brake pedal
- Made and added second lexan steering shaft support just behind new U-joint
- Deburred some holes in plastic sheet on sides of footwell - used to scrape knees
- Trimmed main disconnect switch post to just a couple of threads sticking past nut, and padded whole thing to protect left knee
- Padded rev limiter box and its bracket to protect right knee
- Padded front swaybar to protect shins over big bumps
- Trimmed throttle pedal narrower to reduce snagging while right-foot braking
- Expanded slot in right side throttle pedal guard to stop interference with throttle cable rod end (put cable in bending) when near full throttle
- Replaced all padding for elbows and shoulders with interlocking foam play mat material
- Zip-tied numerous cables and hoses that were chafing on each other
- Disassembled the locking/sticky Tilton bias knob and fixed it
- Audited current shock settings to ensure I have a baseline to always go back to as needed. Holy cow, adjusting rear rebound sucks! I had to turn the radio off in my garage so I could focus more on aligning the tiny wire with the hole and counting sweeps! More practice is needed before I'm ready to do that in seconds between runs...

Most of the tasks were driver comfort/safety items with a few obvious maintenance issues that appeared while poking around. It's looking good to have the car ready for our local club's test and tune event on July 23rd! My goal is to do a few drives around my driveway to get any small issues out of the way before that.

Questions:
1. How do you drain the oil in a Citation? I think Sho mentioned pulling the lower oil tank hose, but that sounds like it'll make a HUGE mess as it drains directly on the floorpan! Maybe a vacuum extractor in the oil tank?
2. How do you refill the oil? Just fill the tank (to the depth specified on the oil cap) while cold? Or do I need to run the engine and ensure the oil level is that depth when the engine pan is filled and hot?
3. Where is the thermostat on the 1.6L engine? I assume it's on the front of the engine. If so, how do you get to it without pulling the engine? I would like to replace the thermostat while I'm replacing the antifreeze with water and Amsoil Dominator Coolant Boost or Redline Water Wetter.

It's been quite a learning experience and I haven't even driven the car yet!
Corey

[Gary_T]

Hey Corey,

There is a picture in this thread:

http://www.apexspeed.com/forums/show...ent+thermostat

Shows where the thermostat lives, the very front of the head.

Gary

[JGB]

- Bought the thinnest/slimmest shoes I could find, which turned out to be the RJS shoes (which feel like slippers in comparison to most of the other SFI shoe

Hi Corey,
I'm having shoe problems well. The toes in my current shoes just slightly snag on a frame member as I move between the gas and brake. Right now I'm bending the toe back and duc taping it to be just enough shorter.
Which model of RJS did you get?
Thanks,
Jim

[captain_pants]

Thanks Garry, that's very helpful!

Jim, I got the RJS Mid-Top Race Shoe. The toes do extend a little beyond my toes though, so these may not solve your problem. The soles are probably 1/2 as stiff as any other race shoe I tried on, and the uppers are super-flexible suede with a Nomex lining.

[captain_pants]

I need to clarify my initial post and all other threads regarding this car: I am absolutely NOT critiquing the maintenance or choices of any of the previous car owners! Cars (and all mechanical things) are in a constant battle between maintenance and increasing entropy. Said another way: Stuff degrades over time/use. Our job as owners is to find the degradation before anything bad happens.

I have found nothing on the car that was done in an unsafe or unprofessional manner! I have found a few rare items that wore quietly behind the scenes without being noticed, as you needed to disassemble other things to find them. The pointy brackets I mentioned in the footwell were previously used as mounts for data logging equipment that is no longer in the car.

Most of the work I've done is due to personal preference. I'm loving that I can just change stuff (within limits) without worrying about jumping to another class. Example: I want more knee room due to the bumpy surfaces I encounter. Therefore, I've increased knee room and padded everything my legs can contact.

My goal with this thread is threefold:
1. To serve as information to others that may be considering the class (more people to race = more fun!)
2. To gather information that I may need to do a job properly, or to save me a bunch of time
3. Hopefully, a bit of entertainment for those that are already here

When I was researching CM, I found surprisingly little other than Pete's excellent SCCAforums thread. It was, frankly, discouraging. Do I need to be a master welder/craftsman to own and maintain one of these cars? That question and many others loomed over me as uncertain until I started working on the car.

So far, I haven't done anything that someone with basic hand tools and knowledge can't accomplish. The fanciest tool I've used to date was a drill press to get the holes straight through the U-joints. Other than that it's been: SAE wrenches, a Dremel-type tool, a cut-off wheel on a grinder, drill and bits, a hammer, and a cold chisel (for drilled rivet heads). That's been a refreshing change when compared to the dizzying array of tools I've used on various production cars over the years. Anyone need 23 and 24mm sockets to change the oil on a Honda rear diff?

Do people want me to continue updating this, or just keep to myself? Let me know. Either way, I'm driving the car on July 23rd and will try to post video afterwards!

[Gary_T]

I like reading it - hope to see it at Gimli in Aug (I think there is a solo that weekend too, right?).

Gary

[captain_pants]

Hi Gary, we're racing at Gimli this Sunday after you guys are all done, but the car isn't quite ready yet. That's our only event in Gimli this year.

[Gary_T]

Ah - and my car isn't ready for this weekend either.

Talk with Helmut / Murray / etc - lots of FF guys will be there with lots of experience.

[mwizard]

Corey,
Keep up the reports. It is great to hear from a new enthusiastic FF owner. It might inspire me to start reporting what i am doing with my car.
Mark

[CM/FFdriver]

Corey,

The more the merrier, any little info that could help any future CM runners would be great.

Your right in saying there very easy cars to work on, me for instance it took me 3 days to figure how to get in and out of my car (84 VD) and because the body was off I was looking right the front wheels saying "how am I going to drive this thing".

I believe the biggest thing is very driving these cars, they are so mush fun I just can't wait until the next event next weekend.

Have fun!!

Ben

[captain_pants]

Cool, thanks for the feedback.

I found the thermostat thanks to the linked pictures. It's so easily accessible that I'm kind of embarrassed to have asked. Haha, live and learn!

I'm assuming i need a 180-degree thermostat from any parts store? To fit a 1979 Ford Fiesta?

[-pru-]

I'm assuming i need a 180-degree thermostat from any parts store? To fit a 1979 Ford Fiesta?

1979 Ford Fiesta will work. I'm using a 160-degree thermostat. Whichever you choose, make sure you drill a couple of 1/16" holes in the thermostat to help bleed the cooling system.

[TeamFRD]

Something to check...
After 5 years, my throttle cable unscrewed itself while on course, of course.

Wait until you separate the chassis, engine, and trans, put it back together and it runs

[Jim Garry]

Doing that on the Citation was a breeze. With a few bolts removed the chassis/engine went one way while the transaxle went the other.

[captain_pants]

FYI for future Citation owners; oil level is to be checked just after the engine has run. Run it a little high and monitor your catch tank. When it stops puking into the catch tank - that's the right level. Measure that and repeat next time. Thanks to Steve L. for the tips.

First drive today on a very quiet country road (don't try this at home!): Whoa! I'm absolutely in love with the dogbox. I want that in every car I own! I didn't get to do more than putter around, but I can tell this is going to be a blast!

[captain_pants]

Day 1 in the car was a test and tune. The car ran like a champ all day! Coolant temps stayed stable as long as I ran the fan, even though we didn't even have time to shut the car off between runs. It just ticked off trouble-free laps like a street car. Well, except for the speed!

Wow, what an engaging car! It's like any other car I've raced, except times 2. I was on Hoosiers from 2011, which I expected to be terrible but fun to burn off. They were indeed horrible in the first run group as it was raining an 65F or so. It was a good lesson in car control and how 'friendly' the car is. It was quite neutral and confidence inspiring, even with dead tires. I struggled to stay off cones, but I'll blame the tires for that! Here's a wet run with the camera just above my helmet visor:
http://www.youtube.com/watch?v=HDHBbi3735I

Then, it stopped raining before our next run group. I went out on the same tires again, hoping they might get some heat and become less crappy. They did! Wow, this car just keeps getting better! I'm in love. I've already let my co-driver know that I'm driving my car instead of his in tomorrow's race event. Here's a video in the dry from a GoPro on the roll bar. The camera was very unhappy with this position! You can get the idea though:
http://www.youtube.com/watch?v=SYjZGIRMwFQ

It was an awesome day! My elbows have bruises from hitting the frame tubes while steering, my neck hurts a bit, and I'll be putting the tires from 2012 on the car for the event tomorrow. I also learned that using a MicroSD card in an SD adapter is a bad idea in a FF. It just vibrated the MicroSD card right out of the camera and caused problems. I'm starting to see why there are so few videos online of CM FF cars!

Now, I'm going to go wash the mud off the car and do a nut/bolt check. Then a good night's sleep before more fun tomorrow!

[CM/FFdriver]

Did you go down to First? on the turn around it sounded like it. The car and you look good though go have fun tomorrow.

PS see I told you when you drove your car for the first time, that's all your going to do

Ben

[captain_pants]

First race in the new car: (one forward facing lap, one rearward facing)
http://www.youtube.com/watch?v=WDpUKMMQw9s

Wow, I have lots to learn, including how wide the car is. I hit 11+ cones (they stopped counting at 11) on my first run. Oops.

Then, on my third run, the car was pretty loose everywhere and struggled to put down power. I made a mid-run mental note that I needed to check the swaybars once back in the pits, but it turns out I had a tire going down. It was down to 3 psi by the time I was in grid. That's pretty amazing that the car was that controllable. Luckily I brought the the 2011 tires to replace the 2012 tire that deflated!

I got a friend in the seat for fun runs. He spun and struggled with it, but loved it. He just sat in the car after the run for a minute to catch his breath and process everything that happened. One more convert? Not yet, but he's tasted the goodness.

Another friend (SoloPro instructor) commented that the car rotates around the white spot in the middle (my helmet) which is pretty high praise. I'll get him in the driver's seat another time! The local community is pretty excited about the car as it's different. The local SAE racers are checking out the details pretty closely as well.

Ben, I am still struggling with driving this car vs. driving a Street-class car. Right now I'm realizing how much learning I have ahead of me, which means that seat time in the Citation will pay off next season. But the racing is super-tight in Street class with Nationally-competitive drivers in our local series. The Citation is a pure joy to drive though, so that's kind of winning out right now. We'll see.

[ahowe]

I've never seen anyone get out of one of these cars and say, "That was horrible. I never want to do that again."

[captain_pants]

I've never seen anyone get out of one of these cars and say, "That was horrible. I never want to do that again."

Haha, good point, and probably applies to any Formula car. A few of the Formula SAE cars I've driven were ludicrously fast but had a tiny sweet spot of inputs. They were technically 'awful', but still a blast to drive.

As a sidebar; a local was talking about updrading his Toyota Corolla to a full-blown SMF car (different engine, big DOT slicks, etc) and getting a trailer. I suggested that for less money, he could just buy a CM car and go really fast. That raised his eyebrows quite a bit.

Man, I have some serious bruises on my elbows and knees now! What felt ok in my garage while making racecar noises wasn't good enough for a bumpy track... Haha, still worth it!

[S Lathrop]

Man, I have some serious bruises on my elbows and knees now! What felt ok in my garage while making racecar noises wasn't good enough for a bumpy track... Haha, still worth it!

To get more arm room in the cockpit, you can raise the steering wheel, move the wheel forward a bit and change the wheel to one with a smaller diameter.

[captain_pants]

Ah, never thought of that. Thanks! I can't go up as my knuckles are quite close to the tubes, but I can go forward 1/4" or maybe more before they'll hit. I do have long arms for my height.

Another random question: I was banging shoulders/tips of collarbones on the upper cockpit ring tubes too. (Really glad I refreshed the padding there and wrapped it around the underside too!) My immediate thought was to shave the seat back to recline a little lower/further back, but then the forward side of the cockpit ring is already just below my vision of the road 1-2 seconds in front of me at autocross speeds (30 mph and up). Maybe a small change is all that's needed?

BTW: Steve, I hope you have a sense of pride in this car, and I'm sure the other Citations. What a pleasure to drive, 30+ years after its construction. Your attention to detail and passion shows through. Bravo!

[captain_pants]

I didn't have much time since the last autocross, so I only did a nut/bolt check on the car, checked fluids, and put on the used tires I got from jbracingtires.net. The first run revealed how much nicer the car was with the newer tires - no big surprise there!

Changes I made to my setup/process at the event:

- I tightened the heck out of my shoulder straps. In cars with doors, I've preferred the shoulder straps a little loose so I could move slightly to look around the A-pillar, and I just did that without thinking in the FF. On a whim, I cranked these down tight for my second run to see if I would stop banging my shoulders on the cockpit halo - YES! Much better.

- Man up and go for it. I realized that I hadn't spun the car or went off course at all, meaning I was leaving potential time out there. Get the car dancing! This car responds in a very friendly manner - so thrash it and see what happens. We talk in our local Level 2 school about only being 80-90% certain that you can make the next element, I had to get comfortable with the car to get to that state for all of the course. I'm not there yet, but getting closer.

So much fun! I can tell I'm still conservative under braking, but am getting more and more comfortable. The car stalled going into one of the hairpins on a run, so I clearly had too much rear bias. I've dialed it forwards a few turns and it felt better. I'm a little disappointed in myself that I couldn't feel that, but I'm not blending turning and braking very aggressively yet.

I ended up about 2.6 seconds off the top PAX time, which I'm ok with at this point in my learning curve. I have a long way to go, but that'll come with practice. Here is a video compilation of 3 different angles of 2 runs. One on the nose, one on the helmet, and one rear-facing by the rear suspension:

http://www.youtube.com/watch?v=OPnvAgYGm6M

For fun runs, I managed to get two different friends in the car for a couple of runs. Yup, they liked it! The common feedback is that it is overwhelming coming from a door-slammer, but they find the car to be very predictable when things aren't going perfectly.

[captain_pants]

A few more events in and I'm really bonding with the car. What a wild ride! The part I enjoy the most is the 'playfulness' of the car. It'll drive around sideways all day if you want, and the over/understeer recovery is very nice and progressive instead of the wicked snap I've seen in so many other cars. Maybe that's the tires, maybe it's the chassis, or maybe it's the combination of the two. It just does what you ask of it, even if you ask it something stupid. It's not the tires scratching the road for traction; those are my fingertips. What a glorious feeling!

The last event had me 0.05 off FTD (taken by an awesome E Mod car) and 8th in PAX if it weren't for a cone from a big slide. It's a local event and all, but I'm pretty happy with my progress as we have a lot of very quick drivers locally in Winnipeg.

A few niggling issues have come up that I'm not sure how to fix best:

1. The clutch seems to not fully release every now and then. Pumping the clutch pedal resolves it at the moment. Other times it'll hold almost indefinitely. I noticed a tiny drop of blue fluid on the slave cylinder, but both the trans fluid (Redline light Shockproof) and brake fluid (ATE Super Blue) are blue so I'm not sure it it's the slave or the front bearing on the trans. I suspect the slave cylinder. The slave is an annular cylinder around the trans input shaft. Can these be rebuilt?

2. The car sputters pretty badly off the line unless I rev it up a few times to 'clear the carb' as someone suggested at the event. A few quick blasts to 4k-ish rpm before moving resolves the issue. Is that a normal thing or does it indicate a carb-tuning issue? Pardon my carb ignorance if this is obvious...

3. Bouncing over bumps. How can I determine if it's caused by too much or too little damping? Or maybe too little droop or bump travel? What do you change when you go to a bumpy track?

4. The chassis contacts the road over a few ruts/ridges on our site. I was planning to raise the entire car 1/4" or maybe 3/8". I understand that this is a negative for mass transfer as well as moving both roll-centers around, but I suspect that grounding out is worse than any geometry change. Thoughts?

5. The car does not stop as well as it goes or turns. I'm able to lock wheels, but at the threshold of lockup it's just ok. I need to get my datalogger on it to see if this is just driver perception or reality. No real question here; just self-doubt and me typing it out.

[S Lathrop]

A few more events in and I'm really bonding with the car. What a wild ride! The part I enjoy the most is the 'playfulness' of the car. It'll drive around sideways all day if you want, and the over/understeer recovery is very nice and progressive instead of the wicked snap I've seen in so many other cars. Maybe that's the tires, maybe it's the chassis, or maybe it's the combination of the two. It just does what you ask of it, even if you ask it something stupid. It's not the tires scratching the road for traction; those are my fingertips. What a glorious feeling!

The last event had me 0.05 off FTD (taken by an awesome E Mod car) and 8th in PAX if it weren't for a cone from a big slide. It's a local event and all, but I'm pretty happy with my progress as we have a lot of very quick drivers locally in Winnipeg.

A few niggling issues have come up that I'm not sure how to fix best:

1. The clutch seems to not fully release every now and then. Pumping the clutch pedal resolves it at the moment. Other times it'll hold almost indefinitely. I noticed a tiny drop of blue fluid on the slave cylinder, but both the trans fluid (Redline light Shockproof) and brake fluid (ATE Super Blue) are blue so I'm not sure it it's the slave or the front bearing on the trans. I suspect the slave cylinder. The slave is an annular cylinder around the trans input shaft. Can these be rebuilt?

2. The car sputters pretty badly off the line unless I rev it up a few times to 'clear the carb' as someone suggested at the event. A few quick blasts to 4k-ish rpm before moving resolves the issue. Is that a normal thing or does it indicate a carb-tuning issue? Pardon my carb ignorance if this is obvious...

3. Bouncing over bumps. How can I determine if it's caused by too much or too little damping? Or maybe too little droop or bump travel? What do you change when you go to a bumpy track?

4. The chassis contacts the road over a few ruts/ridges on our site. I was planning to raise the entire car 1/4" or maybe 3/8". I understand that this is a negative for mass transfer as well as moving both roll-centers around, but I suspect that grounding out is worse than any geometry change. Thoughts?

5. The car does not stop as well as it goes or turns. I'm able to lock wheels, but at the threshold of lockup it's just ok. I need to get my datalogger on it to see if this is just driver perception or reality. No real question here; just self-doubt and me typing it out.

1. The clutch cylinder is either a Tilton unit (most likely) or a SAAB 900. You will have to take a look to see what you have. My bet is that the cylinder is way past time for a rebuild. The master cylinder has serious age as well and may need attention. Check to see that the piston returns fully and quickly after being depressed. Check to see that the brake fluid is not foaming up from chassis vibration. This will happen with steel or aluminum reservoirs, rigidly mounted.

2. You are going to have to start thinking about jetting the car correctly. You need to be changing jets as density altitude changes. Good acceleration demands that the engine run just a bit lean. Also check float level. This is critical for good performance as well. Optimum is the brass float with a bit of solder or the plastic floats with screws epoxied in to the bottoms to increase the weight of the float a bit. The float level will need to be checked by running the engine and seeing where the level is in the bowl with the floats removed. This is critical to getting the engine to run well. Too high a float level will cause the engine to run rich and sputter coming off a corner. Too low will cause the engine to miss in the corner as the mixture goes too lean.

3. You need to be running Dynamics bump stops and get them set properly. The motion ratios are quite low with on that car so the shocks are not all that effective. But you should get then checked and have the oil changed. Also you should be checking the shock gas pressure each weekend. I am assuming that you have either Fox or Penske shocks.

4. Bump stops, this is what they are for. Run them both on the front and rear.

5. Check brake rotors. The thin rotors we used on FFs at the time were prone to ware and warp. The rotors are machined from VW Rabbit rotors. They are just thinned, usually from one side of the other. But a rotor turning machine can reproduce what you have. You are going to have to start trying various brake pads to see what you like. Not having enough heat in the pads is just as bad as too much heat for brake performance. More than likely, the pads you have are too hard and are not getting up to a good temperature and staying there. Start using temperature paint to see what you are getting and find out what the pads want for best performance. PFC pads are very temperature sensitive. The coefficient of friction between the pad and the rotor is very temperature sensitive and can change dramatically with a slight increase in temperature. On later cars we went to the LD20 size calipers and 3/8 thick rotors. But the smaller stuff might work better for you because of the very short runs.

[Jim Garry]

I sent you an email.

[Jim Garry]

The motion ratios are over .9 on both ends of the car.

[S Lathrop]

The motion ratios are over .9 on both ends of the car.

I forgot that this car has different front rockers and the rear was converted to a rocker suspension.

The bump stop comments still apply.

Don't raise the car. get the bump stops setup right.

[TedV]

#4 I always thought Jabroc or HDPE skid plates were for the scraping on the ground. I think they need to be 10mm or less thick. Need to re-read the rules. Bump rubbers ease you into a higher spring rate instead of going full solid at the end of the shock compression.

when walking the course, plan your car placement around the crap pavement high spots if you can. Some lots are more like off roading than pavement. suspension doesn't compress and the chassis will still high center on the mountains.

[R. Pare]

Steve meant to write "bump rubbers", not bump stops.

[captain_pants]

Thanks all, once again! I'll spend some quality time with the car this weekend.

Here's a video from our last event. Taken on a helmet cam then somewhat stabilized with the Deshaker app. I tag a cone on the right side at 0:31:
http://www.youtube.com/watch?v=lhyKoid_eA8

[mwizard]

Thanks all, once again! I'll spend some quality time with the car this weekend.

Here's a video from our last event. Taken on a helmet cam then somewhat stabilized with the Deshaker app. I tag a cone on the right side at 0:31:
http://www.youtube.com/watch?v=lhyKoid_eA8

Looks like seat time is working for you. I noticed braking smoke from your front tires. If you don't also get it from the rears, you may need to adjust brake bias to the rear. I did it 5 times in my car before it worked well. I guess one of the things the precious owners did not get around to.
Mark

[captain_pants]

Thanks! There will be some more time in the seat this coming weekend. It's a tough job but someone has to do it!

The going theory is that the brake pads are dead. They're very old. But you're right, I do need to do some more experimenting with bias. I've locked rears and stalled the engine before, which drove me to move a bit towards the front. The lockup in the video was just as I turned the wheel, indicating that I didn't blend the trail-braking very well.

[captain_pants]

Two more autocrosses this past weekend:
I moved the brake bias rearwards after every run and still didn't lock up a rear, so I clearly had the bias set all wrong. Maybe my 6-year-old turned the bias knob while playing racer? (Still worth it to have her 'helping' in the garage! ) Unfortunately there were no straight braking zones on the most recent course, so it wasn't a good test.

I also raised the car about 3/8" to deal with ground clearance issues. As Mr. Lathrop suggested, this dramatically changed the car's handling! I'm guessing that the rear roll center goes up a LOT faster than the front for the same change in height, as the car was quite oversteer-biased with this change. I ran out of adjustment on the swaybars so I just drove around it. I'll need to check the spare bars for a larger front or smaller rear bar. Before the next event, I'll lower the rear a bit to split the difference and see if there's a happy middle ground between bottoming and handling balance. I'm keeping good records so I can go back to the baseline for events in Lincoln or wherever.

At the end of the event I was able to put a good friend (and SoloPro instructor) in the car for some fun runs. He matched my time in two runs, if you ignore cones. That's pretty cool, if not humbling, for him to get that comfortable in just 2 runs. As per usual, no complaints from the driver!

I spoke in another thread about wanting PAX wins with the car, and I'm around 3 seconds off for now. I am definitely not optimizing my use of the car for the entire run, so I'll continue striving to improve my driving/thinking to catch up with the car's abilities. Our lot has historically favored street tires over Hoosiers in PAX, but more like a 1-second difference in PAX for a 60-second course, so that's my target.

[Purple Frog]

Number 2 rule in racing: Don't chase bad tires.

Old multicycle racing tires don't AX very well, you never get enough heat in them to bring them back to life.

In my whole career, I never had nor wanted a car where the rear brakes would lock up. In road racing it would be a formula for disaster. Maybe in A-cross you are trying to create oversteer with trail braking?

I was lead to believe most A-crossers like oversteer over understeer, if so, Steve's changes are going the right way.

[S Lathrop]

Two more autocrosses this past weekend:
I moved the brake bias rearwards after every run and still didn't lock up a rear, so I clearly had the bias set all wrong. Maybe my 6-year-old turned the bias knob while playing racer? (Still worth it to have her 'helping' in the garage! ) Unfortunately there were no straight braking zones on the most recent course, so it wasn't a good test.

I also raised the car about 3/8" to deal with ground clearance issues. As Mr. Lathrop suggested, this dramatically changed the car's handling! I'm guessing that the rear roll center goes up a LOT faster than the front for the same change in height, as the car was quite oversteer-biased with this change. I ran out of adjustment on the swaybars so I just drove around it. I'll need to check the spare bars for a larger front or smaller rear bar. Before the next event, I'll lower the rear a bit to split the difference and see if there's a happy middle ground between bottoming and handling balance. I'm keeping good records so I can go back to the baseline for events in Lincoln or wherever.

At the end of the event I was able to put a good friend (and SoloPro instructor) in the car for some fun runs. He matched my time in two runs, if you ignore cones. That's pretty cool, if not humbling, for him to get that comfortable in just 2 runs. As per usual, no complaints from the driver!

I spoke in another thread about wanting PAX wins with the car, and I'm around 3 seconds off for now. I am definitely not optimizing my use of the car for the entire run, so I'll continue striving to improve my driving/thinking to catch up with the car's abilities. Our lot has historically favored street tires over Hoosiers in PAX, but more like a 1-second difference in PAX for a 60-second course, so that's my target.

Remove the rear sway bar. Run without it, if you have to run the car that high. At worst, you might have to increase the rear spring rate 50 pounds per inch. The car, most cars for that matter, are very pitch sensitive. You might be able to correct some of the ride height issues by lowering the rear 1/16 inch or so and get a better balance. With a stiffer rear spring, you can lower the car by as much as 1/8 inch and keep it out of the ground.

Get a very accurate way to measure the ride height. changes as small as 1/32 of an inch can make a big difference. I like to use a metric scale for ride height measurements. It leads to fewer mistakes.

You are better off working with bump stops to limit down travel than simply raising the car enough to keep it out of the ground. You loose a significant amount of cornering potential by increasing the CG of the car. The negative effects of raising the ride height are equally attributable to the change in suspension geometry and change in the CG of the car. You can setup bump stops on both ends of a car so that they actually enhance overall grip.

[captain_pants]

Number 2 rule in racing: Don't chase bad tires.

These tires have ~25 runs on them. Surprisingly, the car is only a tiny bit more oversteer-y with 150-run tires from 2012. (I use these for fun runs)

This raises and interesting question: How hot is too hot for the soft R25A compound? I've had tires too hot to comfortably leave my hands on for any length of time with our quick turnaround between runs and some tire blankets.

In my whole career, I never had nor wanted a car where the rear brakes would lock up. In road racing it would be a formula for disaster. Maybe in A-cross you are trying to create oversteer with trail braking?

Certainly not! However, the fronts were locking long before the rears. I'd like the fronts to lock just before the rears.

I was lead to believe most A-crossers like oversteer over understeer, if so, Steve's changes are going the right way.

I'd prefer a neutral car, but that's an elusive beast so I'll pick a slight oversteer bias if I have a choice. I can always drive it like an old 911 - no trail-braking and get on the gas early. I definitely prefer a touch of understeer in transients so if I get behind in a slalom I'm not chasing the tail of the car.

Remove the rear sway bar. Run without it, if you have to run the car that high. At worst, you might have to increase the rear spring rate 50 pounds per inch. The car, most cars for that matter, are very pitch sensitive. You might be able to correct some of the ride height issues by lowering the rear 1/16 inch or so and get a better balance. With a stiffer rear spring, you can lower the car by as much as 1/8 inch and keep it out of the ground.

Great stuff as always! Assuming I'm 'grounding out' (see below), would raising the front further have the same effect? I'm going to try lowering the rear first, but am looking for a complete set of options.

Get a very accurate way to measure the ride height. changes as small as 1/32 of an inch can make a big difference. I like to use a metric scale for ride height measurements. It leads to fewer mistakes.

Haha, I do use a millimeter scale and convert it to inches to post here for the benefit of the average user in the USA. It's much less thinking for me while laying on the ground!

You are better off working with bump stops to limit down travel than simply raising the car enough to keep it out of the ground. You loose a significant amount of cornering potential by increasing the CG of the car. The negative effects of raising the ride height are equally attributable to the change in suspension geometry and change in the CG of the car. You can setup bump stops on both ends of a car so that they actually enhance overall grip.

I think I used the wrong term for 'bottoming' - there are depressed tire tracks from heavy-equipment testing that put my belly pan close to the center ridge with my static ground clearance of about 1" (I can't recall the exact height and don't have my setup notes, might be 1.5" static height). We're not crossing them at 90-degrees, but rather we run roughly parallel to them for a short time. Add in a little braking/accel/body roll and I have occasional contact.

Yes, I know that our lot sucks. But I'd rather race 15 days a year on that lot than not at all! The next closest autocross is an 8+ hour tow. The big show in Lincoln is about 10 hours away.

[Barry Ott]

This raises and interesting question: How hot is too hot for the soft R25A compound? I've had tires too hot to comfortably leave my hands on for any length of time with our quick turnaround between runs and some tire blankets.

Here's a clip from an email from Jeff Speer (Hoosier Product Manager):

If you are taking time temperatures with a needle pyrometer to assist with camber settings, your tire temps should be in 110 – 140 degrees for the grip levels to stay competitive.

Any temperature above this 140 degrees, the tires may get greasy.


Barry

[captain_pants]

Awesome, thanks Barry! They were definitely hotter than that for my last run. No wonder I felt like I drove better but the clock said otherwise.

[captain_pants]

A video from the previous event: http://www.youtube.com/watch?v=qw1Mk58_ivI

I'm still hunting for a good camera location. This is a GoPro suction cup mount on the outside by the driver's shoulder. I like this view but didn't realize how bad that panel vibrated until I watched the videos at home. Deshaker made it usable but it has limits.

I've lowered the rear slightly and reset the corner weights. Tomorrow I'll check sway bar options.