Tag Archives: tires

Comparing forward and conventional driver seating

Watching the Canadian GP on the idiot box while waiting to walk down to the phone store and pay the bill. Aside from Hamilton running away and hiding from the rest of the field it is a good race to watch with lots of close racing all up and down the order. And in a few minutes the Cup race from Pocono starts.

You have heard the saying about a picture being worth a thousand words, and my usual post is about half that. So instead of talking about the difference in the driving position I marked the body with the rear of the conventional driving position to go with the previously marked far forward driving position.You can easily see how far forward the driver gets moved
The forward mark is the same one I used before, same piece of tape even. The rear mark is what I get by putting my feet behind the original firewall. That tiny piece of tape was the inside edge of my butt marker from when this body was going to be a front engine bucket with two seats. Yes, my butt is that narrow, the outside edge is the edge of the floor where the body turns up. And moving my butt that far forward only changed the weight bias from 63% rear to 60% rear without the 0.25″ floor pan under said butt.

OK F1 race just ended and Hamilton finished like 20 seconds ahead. Except for the usual first lap/early race carnage most of the attrition was brake failure except for one engine vibration retirement to keep from scattering the engine on the track. So now I switched to the Cup race at Pocono which is still in Stage 1 and drivers are already complaining about brakes going away, which partly shows why I want to make sure I can get enough tire to make good use of the big brakes on the TGS2. I know with the rear weight bias the front brakes won’t get as much use as they would with the front engine, and the rear brakes will see much higher temperatures than with the front engine.

And Junior just missed a shift and damaged the engine. And now it has been a few laps and Jimmy Johnson and Jamie McMurray both just had brake failure in the same turn, same lap to crash within feet of each other with McMurray catching fire from the impact damage. Jimmy absolutely nailed the wall, almost knocking it down. He got out under his own power but had to catch his breath a bit before taking the mandatory ambulance ride, while McMurray was in such a hurry to get out of his burning car he didn’t disconnect the AC hose and was walking around after the wreck with part of it hanging off the back of his helmet. Race has been red flagged because of the mess in turn 1, when Jimmy hit a lot of parts and pieces fell off the car and fluids ran on the track.

And Ryan Blaney just beat Kevin Harvick to the checkered flag. Sorry I got hung up with watching the race and forgot to report on it, but if you were interested in the race you would watch it I guess. And to add fuel to the Ford v Chevy wars, Harvick did the 3-2 instead of 3-4 shift and his Ford was fine but the Chevys all blew up in the same situation. And a Ford won.

I just saw an interesting use for coal, a carved anthracite trophy at Pocono. I don’t know if the eagle is made from coal but what is under it is.

And it’s time for me to walk to the phone store and pay the bill.

Apologies for the radio silence

This has been A Week. Excuse me this has been A Week. I spent all day Monday on DART or DCTA buses or trains to do that echocardiogram thing. But I did see an interesting car.
I think this was a NASA (other NASA) event car

I got to watch my heart beating again while they did the echo, which was cool.

Tuesday was go to the lab rat and get the 24 hour BP monitor and the jug to collect my urine for the next 24 hours, and also I got hit by a huge blast of grass pollen, so bad that when my allergy pill took effect I fell out of my chair trying to do a post which I discarded because it made even less sense than that post I did while dehydrated and tipsy. And how can I tell you how much fun it is to tote a jug of your own urine around? Next paragraph. Anyway I didn’t hit anything valuable or breakable on the way down out of the chair, so I counted my lucky stars and decided to sleep it off in bed for the next 2 hours, which didn’t prevent me from falling asleep early that night

Wednesday was get rid of the half-full gallon jug of urine, and the damnable blood pressure monitor that was squeezing my arm to death. The jug got a lot of stares on the bus with the biohazard sticker and the “Danger Acid” sticker. Then it took 2 tries to draw blood. I think the needle went through the vein because no blood would come out with the needle in and when they took the needle out it wouldn’t stop bleeding. Then I got stabbed in the other arm. After lunch I went to a place that does a 45 minute leg and foot massage with a 15 minute back massage for $30. I felt much better after that than I usually do after the full hour on a full body massage. Then I was going to get a haircut, but there was a wreck on the Tollway that made a normal 20 minute bus ride almost twice as long, which made me miss my connecting bus which got me to the stylist after my stylist already left for home. So my head is still shaggy. “How shaggy?” you ask. Well my back hairs go all the way up my neck and the only way to tell head and back hair apart is the back hair is going white already, and slightly more wavy than my head hair. And my character in Shadowrun just integrates the back hair into his regular hair style, flattop all the way back and down like a horse’s mane.

And during down time I did some more research and changed the race tires again, for a set of Formula Atlantic tires. Good grip for a car about the same size and weight as the Mid-Bucket and I can find wheels that fit the tires and the bolt circle of my car. Amazingly it is way easier to find 15 X 14 wheels with a 5 X 4.5 bolt circle than 16 X 12 wheels. So the front wheels will be 15 X 10, the rears 15 X 14 and I may be able to get the car balanced without adding an antiroll bar.

And it is almost dinner time and I need to get cleaned up.

I found bigs and littles I can race and run on the street

At least until it rains, then all bets are off.

The tires (by Hankook) are not that bad in the wet, but put them on a 1600 pound car with brakes that can stop a much heavier car even without power assist and then add water in typical TX thunderstorm amounts and with a car that is naturally tail-happy… Wet weather driving will be done quite cautiously.

The main problem I’m having now is getting the right size wheels for the tires I chose, especially the front ones. You wouldn’t think 15 X 6 wheels would be so hard to find at a reasonable price, but they are. The rear wheels are comparatively easy, but where it really gets hard is getting both wheels in the same style and in compatible offset. In fact I’m having so much trouble finding the compatible offset I’m strongly considering using wheel spacers up front to make the mounted offset compatible.

That’s just for the street, for racing I don’t give a flying fig if the fronts match the rears as long as the widths and offsets are right and the wheels are light enough. And it is looking like the race slick wheels are not going to match styles at all, the front tires are 22/6.0-15S while the rears are 23.5/10-15S in a softer, more grippy compound. I’m definitely swapping at least the rear springs and shocks when I race SCCA so that I get a better balanced car. That and I’ll need to lower the car anyway as the race slicks are about an inch taller than the street tires which would totally screw up the undercar aerodynamics unless I dropped the rear back down to match the front. And since I’m swapping one set of shocks and springs anyway it won’t take but a few minutes longer to swap both sets. The time consuming part would get done beforehand as I adjust the ride height and set the damping on the shocks before labeling which corner they go on and putting them in some kind of carrying case.

And I have good company in having issues with controlling which way the car is going. Even the best hike the inside front wheel .

And on that note I close this post and bid you farewell.

I give up

I couldn’t do it. There was no way to get the oversteer out of the Mid-Bucket without going to bigs and not-so-bigs. The extreme rear weight bias just was too much for all my tricks and tweaks. I can’t fight physics and no matter what I did I still ended up with oversteer at the limit. Sometimes it was only hang the tail out and go slow oversteer, but most of the time it was understeer up to a point, balanced and then snapping loose and driving backwards off the road.

Now running racing slicks is no problem, bigs and littles is a common setup for mid-engine race cars. Lots of choices that would be balanced at the limit. Just-driving-around tires I also have solved as this is a common setup for hot rods. No, where this is a problem is street tire autocrossing, the thing I’m building this car for. Naturally.

If I stay with 15″ rims I’m pretty much boned as the 245/40 size is pretty much the widest tire I can get in ≥200 UTQG wear rating. I can use that in the rear and run a 195/50 front and get balance but not ultimate grip. My competition will be running 335 wide in the front, and even wider in the back. Granted I’m driving <1600 pounds and they're almost twice that, but still I'm going to be down on grip overall compared to the competition.

The next size up in rims with performance tires is 17", which gives me a whole lot more choice in sizes. The downside is I lose the automatic lowering for racing because the 17" rim increases the diameter of the tire by 2", it's just physics. For the same width and profile the 17" rim is always going to be 2" taller than a 15" rim. I'm still going to be a tiny bit shorter than my street tires on 15" rims, but not by much. And the thought comes to mind that if I'm going to have to use tall tires to race on why do I need to get just driving around tires? I'm not going to be driving a traditional Bucket so why run traditional street wheel and tire sizes? The treadwear requirements for the street tire autocross make the tires usable for daily driving, so why not drive them on the street?

And I'm starting to repeat myself while I type (I deleted 2 whole paragraphs) so this is a good time to quit.

Billed @€0.02, Opus the Unkillable

So much done, so little accomplished

I was out of the house almost 7 hours today. I had a 20 minute procedure done in Lewisville and spent just over 6.5 hours getting to and from it. And I had to skip lunch because I was constantly running around to catch a bus or train with never enough time to stop to buy food. So, I had a lot of time to sit and think about things, and when I wasn’t thinking about things I was thinking about my second-favorite subject, the Mid-Bucket.

The big thing weighing on my mind about the bucket is getting rid of its inherent oversteer. There’s just way too much weight on the rear axle for 4 equal-size tires, and not enough tire selection in 15″ rims any more to be able to correct it with bigs and littles without giving up a ton of front grip. While I realize that excessive front grip is the problem, my philosophy is don’t give away what you have too much of in relation, get more of what you don’t have enough of. So, while I’m willing to find larger rear tires to get more rear grip, I’m completely unwilling to get smaller front tires to get less front grip. This is a race car, you always, always, ALWAYS want more, especially more grip. It may be a race car that I’m going to drive to the race and (hopefully) drive home, but it’s still intended to race and win.

Before I get back to the bigs and littles there are ways to keep the tire size “square” (same on all 4 corners) and reduce oversteer without completely killing the front grip. That can be done with restricting wheel travel on the front while getting absurd amounts of travel on rebound on the rear with long travel shocks and bump stops that only allow the same amount of compression as the front suspension, so that as the car rolls over on the outer tires the inside rear tire is still carrying a lot of weight because it still hasn’t extended the spring fully.

Another way is aero loading the rear more. That one is a little more tricky as rear grip will vary as the square of speed, so the car will still be loose at low speeds but potentially plowing tight as the car goes faster. This is not the way to go. Obviously I’m going to go for as much downforce as I can get, but balanced, and after I get the mechanical grip balanced, not before and definitely not “instead of”.

And I keep falling asleep on the keyboard so Nighty-Night…

I didn’t want to do it this way, but I have a working tire pump now.

Well I had two pumps, one that failed somewhere in the piston and the other one that had a rotting hose from the pump to the chuck. I only have to send one back, so I put all the bad parts in the return box and assembled all the good parts into a working pump. I then used that pump to get my tires back up to the minimum 70 pounds per square inch to prevent pinch flats on potholes.

And after I did that I felt like Superman™ so I tried to mount the tires to the wheels I had just mocked up that afternoon. It was a struggle, but as you can see:
Wheel reduced from a scale 10 inches to a scale 8

I got the front edge even with the bead on the tire, but I need to pump the tire so the back side matches the front.
Back side sticks out a little bit, don't it.

It’s hard to see from that angle, so this is easier.
See all that white? Not supposed to be visible.

So what I do now is talk to my diabetic friends about getting some used needles and syringes to pump up the tires to meet the beads of the rim.

And there’s something good coming on Science Channel, so I have created enough with the words and pictures, Opus the Unkillable