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Old 08-30-2009, 08:23 PM   #1
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Default Understeer with full height foams

I've been trying to deal with this problem for some time and couldn't figure it out.

My home track runs 3 qualifiers early in the day and a main later. For qualifiers I use tires with least amount of materials (Just enough to last maybe 7 or 8 minutes at best) and setup the car to handle well that way.

Thing is, I have to put full height foams on the car for the mains (20+ minutes) and even if I set up the car exactly the way it was when qualifying (ride height, cambers front and back, and droop values), the car always ends up understeering badly.

Why's this? We only have a 15 to 30 minutes break between the last qualifier and the main so I can't chase setups around again after I put bigger foams on. What is there that I am overlooking?
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Old 08-30-2009, 11:04 PM   #2
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Originally Posted by PrimeAKF11 View Post
I've been trying to deal with this problem for some time and couldn't figure it out.

My home track runs 3 qualifiers early in the day and a main later. For qualifiers I use tires with least amount of materials (Just enough to last maybe 7 or 8 minutes at best) and setup the car to handle well that way.

Thing is, I have to put full height foams on the car for the mains (20+ minutes) and even if I set up the car exactly the way it was when qualifying (ride height, cambers front and back, and droop values), the car always ends up understeering badly.

Why's this? We only have a 15 to 30 minutes break between the last qualifier and the main so I can't chase setups around again after I put bigger foams on. What is there that I am overlooking?
maybe you need harder tires
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Old 08-30-2009, 11:43 PM   #3
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Thick foams have a lot of flex and will cause the car understeer. As it wear thinner you will get better grip. If you need to run thick foam try to put a thin layer of CA around the tires and the rim which will cause the tire to be a little stiffer. Not too much as too much will take away corner grip. And make sure you don't get any CA on the tire surface. And a little more camber will help too.
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Old 08-31-2009, 12:03 AM   #4
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try a tire additive... if its legal in your race..

that way you'll have grip on the first few laps when tires are still at starting diameter
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Old 08-31-2009, 12:34 AM   #5
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try a tire additive... if its legal in your race..

that way you'll have grip on the first few laps when tires are still at starting diameter
That is a gooood idea.
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Old 08-31-2009, 05:23 AM   #6
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Experiment with some simple main set-ups. Tire additives can be really inconsistent when it come to running them outside(dust, dirt etc).

If your mains are generally only 15 to 20 mins long try and figure out the minimum diameter tire that you would need to run for the mains. I would venture a guess of around 59mm fronts and 61 mm rears.

You probably won't have to make dramatic set-up changes for larger tires except perhaps running one shore harder on the rear tires. Mains are all about some compromise as well. At some point in the race... the car will "come in" be patient until that point.
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Old 08-31-2009, 06:31 AM   #7
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Hello
Do you respekt the Tire Diameter-difference between front and rear? Try with new Tires at front 1mm less.
LM
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Old 08-31-2009, 06:50 AM   #8
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Hello
Do you respekt the Tire Diameter-difference between front and rear? Try with new Tires at front 1mm less.
LM
Yes I did. I had 1.5mm split in the beginning and at the end of a 25 minutes main yesterday the split was 1.2mm or so.

I gotta figure this out somehow.. my lap times would have gone down at least half a second if the car steered like it did when qualifying .
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Old 08-31-2009, 08:28 AM   #9
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Originally Posted by PrimeAKF11 View Post
Yes I did. I had 1.5mm split in the beginning and at the end of a 25 minutes main yesterday the split was 1.2mm or so.

I gotta figure this out somehow.. my lap times would have gone down at least half a second if the car steered like it did when qualifying .

What size were the tires at the end of the main? When I run the 25 mins mains I start out @ 60 front 62 rear. For the 15-20 mins mains I run 59 front 61 rear. You could always try running a harder rear left tire than the rest of the car. It takes the most abuse from the sweeper and we have alot of right hand turns at the track. Setting the right camber plays a huge role in tire wear too, as stated above.

Its funny, Quinn Moon and I were having this exact conversation yesterday before the mains.
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Old 08-31-2009, 08:36 AM   #10
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Hmmm I see. It was like 61.5 front and 63 rear. I think I am doing OK when it comes to tire wear (still had 1.2mm split between front and back after the race so the rear tires wore only 0.3mm more than the fronts in those 25 minutes) but the understeer really gotta go.

I can try harder rear tires but then I'm afraid that the car might get loose when the tires wear down to qualifying sizes.
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Old 08-31-2009, 09:33 AM   #11
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Hmmm I see. It was like 61.5 front and 63 rear. I think I am doing OK when it comes to tire wear (still had 1.2mm split between front and back after the race so the rear tires wore only 0.3mm more than the fronts in those 25 minutes) but the understeer really gotta go.

I can try harder rear tires but then I'm afraid that the car might get loose when the tires wear down to qualifying sizes.
After the main how much tire did you have left? If you had a lot left figure out what you dont need and start the tire smaller next time. Just remember to set the min. height at that tire size. On bigger tires the car will push at first and then the car comes in and you can drive it hard again.
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Old 08-31-2009, 10:02 AM   #12
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Remember you want the car to come off the track after the main with your tires spent. If you come off the track with plenty of tire left. Then you started the main with too much tire.
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Old 08-31-2009, 10:08 AM   #13
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try softer front tire
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Old 08-31-2009, 10:51 AM   #14
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Remember you want the car to come off the track after the main with your tires spent. If you come off the track with plenty of tire left. Then you started the main with too much tire.
Exactly..Ive ran at the track he's talking about and dont see a 63mm tire being needed for 25 minutes.
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Old 08-31-2009, 01:12 PM   #15
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i havent run my rs09 yet but my rs08 handle the same way in your situation. even if u maintain that ride height, that new/bigger tires just doesnt match your setting and driving style. its hard to explain here, just try something between the high and low of those two tires.

i used to run RayJ setup strategy, less hassle and its a game of being in control after a certain point. if theres something u overlooked, i think its the fun
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