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Tire and tuning questions and observations


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#1 cookie4524

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Posted 27 July 2020 - 02:43 PM

Ive been doing quite a bit of testing at my local track, and here are some things ive noticed. First thing is that the track was rubbered up.

Softer tires, natural/treated, often were looser than harder tires like wonder medium or even wonder xhard in some cases

Having the ride hight being at the minimum legal amount allows the car to corner so much better than at twice the height.

Some tires would "errrt" when full brake is applied, usually wonder rubbers at medium or hard with full width tires

There is a strong correlation between speed, down force,tire hardness, and size. In my case, my group f wing car loved the wx narrows, i could hold it wide open the whole track. However, it would chatter like crazy with an wx that were full width

My questions are, how can i improve handling at higher ride heights? Are adjustable bushings that benificial to being able to use larger, or smaller tires in order to keep the ride hight lower? Are softer tires actually looser, and harder tires more grippy? How much do people narrow their tires? Will i ever stop asking questions?
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Sean Mikuen
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#2 mreibman

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Posted 27 July 2020 - 03:21 PM

There's about 50,000 answers to all those questions. However, the last one is the most important, "Will I ever stop asking questions? " and the answer to that is, you shouldn't stop asking.

 

I am far from an expert on the specifics, but I can tell you in general, the answer to all the above is "It depends."

 

yesterday, on an ogilvie king, I was running a "vintage" 1992 Ted Matkowski plurimeter with a rusty hawk 7 motor.... turning laps just a hair over 4 seconds. I hooked another racer up with the fraternal twin to the car, and we put a c-can group 12 in it... he ran 4.3 seconds. The biggest issue? He put orange parma MX tires that were probably .790 on his car. My car had some kind of .765 "full hub" parma tires, but they had been narrowed so the set screw was clearly visible and accessible.

 

I ran on yellow lane, blipped for the leadon, and punched the rest of the track.

He ran on blue lane, blipped every turn, and his car still couldn't stay on too well. We got a couple laps with smaller tires, but one had a stripped set screw and flew off... but for that short run, the car handled much better.

 

All this being said, here's some generic answers for you:

- cars handle best with the lowest possible center of gravity.

- chassis are generally designed to use a particular diameter of tire, so try to keep to that tire size.

- In general, a softer tire will have more grip than a harder tire - assuming a clean track. On a track that's "rubbered up" as you say, the rubber on the track is helping your tire's job, so you can probably get along with less grip.

- In general, a narrower tire will give you more speed, but at the expense of grip. If you tend to lose grip in the corners, then a narrower tire will probably not be your friend.

- Hub size can also make a difference even with identical tire compounds and diameter. Bigger hub = faster straightaway, but less grip in corners. YMMV.

- downforce, you mention.... move the body forward on the chassis for more front downforce. Move the body backwards for more rear downforce. Bend the spoiler - that's the easiest change.

 

Start there.... I wrote something up for the local raceway with a little more info, but again, your mileage may vary.


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#3 Dominator

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Posted 27 July 2020 - 07:56 PM

Speed and handling for wing cars comes from the body.  Between height, length, and position on the chassis depending on the wheel base (measured from the center of the guide post to the center of the rear axle).    You can message Jason Holmes on here or try giving the guys at PJ Raceway a call in NY.  Ask to speak to Chubby or Doug and they can get you in the right direction. 

 

I don't race wings but I believe one of the most popular bodies is the Red Fox Fox Tail body.  The koford peugot w/rib is also still a favorite I believe depending on the class.


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#4 cookie4524

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Posted 27 July 2020 - 08:05 PM

Speed and handling for wing cars comes from the body.  Between height, length, and position on the chassis depending on the wheel base (measured from the center of the guide post to the center of the rear axle).    You can message Jason Holmes on here or try giving the guys at PJ Raceway a call in NY.  Ask to speak to Chubby or Doug and they can get you in the right direction. 
 
I don't race wings but I believe one of the most popular bodies is the Red Fox Fox Tail body.  The koford peugot w/rib is also still a favorite I believe depending on the class.

For sure, although most of what i was trying out is on flexi stuff, gtp lmp nascar. My group f it was just more noticable.
Sean Mikuen
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#5 Dominator

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Posted 28 July 2020 - 05:17 PM

For the flexi type cars its important to add reinforcement to the body pin holes but to also not take away flex.

Some or most use lean bullet proofing straps. This holds up well.
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#6 cookie4524

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Posted 05 August 2020 - 10:58 PM

Tonight was race night with indy cars, and myself and another racer were very close in the lead for a good 5 segments or so, then seemingly at the same time both of our cars slowed down significantly. We went from running about 4.28 to running 4.45 or higher. Everybody else seemed to be running what they normally were. What could be a cause of this besides crash damage? Unlikely its the motors, as we out our motors in at different times and have different amount of laps on them. The only two things i can think of is tires, and ride height. We were both running hard, narrowed ties, and the only ones running that tire. My guess says that over the course of practice and race, it just picked up enough glue to slow it down. Or both or our cars were too low as the race went on, and the cars started arcing. Although i did not see any.

Both my hypothesis can be easily tested though, as long as the track isnt too changed by next time im on it
Sean Mikuen
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#7 Dominator

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Posted Yesterday, 07:41 AM

Could be from the track getting more bite which does happen.  It could be from the tire size being dramatically smaller from when you started.  Depending on the track/car/type of tire you are running will dictate how fast the tires wear.  Harder tires like wonder rubber will last longer and generally wear less.  At Retro Palooza My coupe and Can Am used .008-.010 of rubber.  Not bad for pushing hard on a Gerding King and minimal rubber lose.  F1 I burnt off a little more at .012-.014. 

 

For lower end cars usually you don't have to narrow tires unless it's a spec tire and you need to free the car up.  Try some JK wonder 8713 ppw (wonder) or 8703 ppw (small hub wonder) next time you try the indy car.   Medium Thunders are also a great tire to start with and perhaps the most commonly used tire in retro racing. 


A motor is only as fast as the chassis it's in.
 
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#8 cookie4524

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Posted Yesterday, 01:42 PM

Could be from the track getting more bite which does happen.  It could be from the tire size being dramatically smaller from when you started.  Depending on the track/car/type of tire you are running will dictate how fast the tires wear.  Harder tires like wonder rubber will last longer and generally wear less.  At Retro Palooza My coupe and Can Am used .008-.010 of rubber.  Not bad for pushing hard on a Gerding King and minimal rubber lose.  F1 I burnt off a little more at .012-.014. 
 
For lower end cars usually you don't have to narrow tires unless it's a spec tire and you need to free the car up.  Try some JK wonder 8713 ppw (wonder) or 8703 ppw (small hub wonder) next time you try the indy car.   Medium Thunders are also a great tire to start with and perhaps the most commonly used tire in retro racing. 


The indy is the jk c21 chassis, not a retro. Im running koford WH narrowed .760s on the .615 hub. And thats from progressing from natural, to treated, to wonder medium, soft and hard from alpha, jk, and now koford. I dont think its the tire diameter though, as i ran .710s and was still getting very fast laps with the same gearing. Ill be there later today, so ill be able to do plenty of testing
Sean Mikuen
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