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Old 08-10-2010, 09:41 AM   #31
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Originally Posted by niznai View Post
I thought you would have done this already. The shocks would have been the first thing to look at.

The idea to move the suspension arms as far back as possible is just wrong. You suffer from more weight on the front already (hence the liftoff oversteer). If anything, you should have gone the other way, i.e. move as much weight as possible on the rear by moving the arms as forward as possible. But that is a last resort move at any rate.

Given the above setup, I would say go for denser oil up front (if you have 400-450 up front that should be a good starting point with 350 in the rear).

If not happy go one thicker up front, leave rear alone.

Stay with the spring rate you have now, two holes open front and rear, change to one hole if not happy.

Get rid of the rear anti roll bar.

Try without front anti roll bar, if you feel you need it, put it back.

Next check you rear droop, make sure it's next to nothing.


About tires.

Sorex can be like that. It happened to me too. I had tires that lasted a long time, I had tires that only lasted a couple of nights. I am not sure what the problem is, but I suspect inconsistent manufacturing. All this happened over two years of racing under constant conditions. My car setup was never changed, the carpet was the same, the tires used were all 24R, medium grey inserts.

One thing I noticed, the inserts swell considerably at the end of their life. they expand 2mm in width and become softer. At that stage you need to chuck them out.

If you have a line of wear you have too much camber. That doesn't mean the camber value is too high, but that you're not using the camber correctly. Remember, camber is useful so the tire has full contact when the car leans into a corner. If you develop a wear line on your tires taht means your tire is only in contact along that line around corners and pushing hard against it. You either need to let your car roll more (which defeats the setting I suggested above in that you need to allow for more droop, so the opposite wheel does not lift off or the car starts drifting) or you need to change (decrease) the camber intake and/or static camber.

All this goes out the window of course if anything changes in the track conditions as we have noticed recently at our club. We have started running a GTA class and their control tires polish the carpet so well, every other class has traction problems.

Back to the drawing board.
I've PM'ed Paul Lemieux about my issue and i'll paste the response in case anyone else gets my issue. It seems like quite a lot do. Regarding the suspension arms, I don't get why you see it as being wrong, as having more weight forward will 'help' stop weight being tranferred to the front off throttle. Having more weight rearward would induce weight transfer to the front off throttle.

I sounds crazy but when I took off the rear bar before, the car actually hooked even more lol! - I also don't think its a good idea to have such an unbalanced car because the car can have weird handling. I'll try harder front shock oil and keep the rear the same, so I can learn what is happening as I make each change.

I do my camber as the middle of the tire wears when I use a new set. I have got it so the middle shine comes off. 2 degrees. Thanks for the tire tips. I do tend to keep the inserts and use with invidual sets of Sorex tires with Speedmind dish wheels. This saves me around 10.00 for each set of 4 tires.

Last edited by maxg123456; 08-10-2010 at 10:13 AM.
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Old 08-10-2010, 10:14 AM   #32
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You seem to be getting a lot of odd and conflcting advice about how to tune the car's handling...

First of all, taking static weight off the back of the car will have no significant effect on weight transfer to the front under braking. Weight transfer (it's less misleading to think of it as load transfer) is 99% a factor of the acceleration/braking/cornering forces. The amount of increased weight on the front end due to the car pitching and rolling is insignificant.

Fundamentally, the end of the car with more static mass on it will have better grip.

Next thought is on the phenomenon of a "stiffer" setting giving the car more grip. What it does is control the contact patch of the tyre better, which can generate more grip. Or, it makes the car more responsive, which can be mistaken for more grip.

It's entirely normal for a car to have more grip with the anti-roll bar fitted, if the rear end rolls excessively without it.

The same with droop. More droop will give more grip. But because decreasing the droop makes the car more responsive, that can be confused with more grip.

Also, the "death groove" on the inside edge of tyres is nothing to do with camber angles. It's to do with the undersized inserts in tyres, which allow the tyre carcass to move freely and bend over on the inside edge when cornering. Don't worry about it.

To increase rear grip on turn-in off-power you should be increasing static weight on the rear end, increasing rear droop, decreasing pitch sensitivity under braking, and decreasing roll sensitivity on the front end amongst a number of other things. Small increments at a time and no great imbalance between front and rear.

That being said, I'm not much of a fan of XRAYs, and I think you would be surprised at how much difference a change of car would make.
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Old 08-10-2010, 10:25 AM   #33
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Originally Posted by maxg123456 View Post
I've PM'ed Paul Lemieux about my issue and i'll paste the response in case anyone else gets my issue. It seems like quite a lot do. Regarding the suspension arms, I don't get why you see it as being wrong, as having more weight forward will 'help' stop weight being tranferred to the front off throttle. Having more weight rearward would induce weight transfer to the front off throttle.
No. What you're doing is permanently transferring more weight to the front which does not preclude transferring even more on liftoff. Unloaded rear will have less traction and on liftoff it will have next to no grip, hence it will overtake the front.

The problem of liftoff oversteering is very well known in the real world of FWD cars which all suffer from it. It is corrected with lower rear ride height, higher rear roll centre and heavier front damping. This is what you have to do.

One other point I didn't yet make because I thought it goes without saying is that you need to make sure the rear diff works correctly so you don't actually have a FWD car.

Quote:
Originally Posted by maxg123456 View Post
I sounds crazy but when I took off the rear bar before, the car actually hooked even more lol! - I also don't think its a good idea to have such an unbalanced car because the car can have weird handling. I'll try harder front shock oil and keep the rear the same, so I can learn what is happening as I make each change.
I don't see what is unbalanced. Roll bars take away grip and should be used only after everything else has been tuned to the full extent.

Mod guys (10.5) at our track don't use any roll bars on their Xrays and they carry blistering speed through corners. Ultimately I think it is a matter of taste (basically I think you can do without if you set up the car correctly).

About balance, I would try to make sure the car is correctly balanced front to rear and left to right (I suppose you've done that already).


Quote:
Originally Posted by maxg123456 View Post
I do my camber as the middle of the tire wears when I use a new set. I have got it so the middle shine comes off. 2 degrees. Thanks for the tire tips. I do tend to keep the inserts and use with invidual sets of Sorex tires with Speedmind dish wheels.
Again, camber is not a means of curing big problems but rather of getting that extra tiny bit of grip. Don't try to use it otherwise (like a guy at our track who is running about 12 deg of negative camber on the rear becasue his car oversteers madly otherwise). You won't get anywhere that way.

If you look in the Xray setup book you will see there is an order of adjustment for every scenario. Start at #1 and work your way up. Don't give up if you don't get results straight away. Go one step at a time in small steps and keep at it whilst trying to understand what happens. From experience, I have noticed most cars with the kit/box setup are pretty much 90% there. Choose the right tires and there is little else you need to do. Notable exceptions I have seen are the TC5 and the Schumacher MI4 (I am talking about carpet med-low grip). And just to give you some idea, I have seen even Corally cars meant for foam on asphalt performing brilliantly with tires on carpet which they were not designed to do at all (with a 3.5mm chassis stiff like a brick). There's a good lesson there, I think.

To solve once and for all your tire problem, I recommend you do this test. Put the test tires on the car, bring them to operating temperature and slam the brakes at full speed. See what happens as you change different combinations of tires and inserts. Choose the ones that stop the car in the shortest distance because they have the best grip. It's not the most scientific test, but it's the best you can do (and potentially the most relevant to all the conditions at the track where you actually race) with what you already have in your pit box and it cost nothing to do. Then go back and start setting up the car for these tires.

I think you'll be surprised.

Good luck.

Later edit:

Sosidge explained it a lot better and types faster.
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Old 08-10-2010, 11:23 AM   #34
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Originally Posted by sosidge View Post
You seem to be getting a lot of odd and conflcting advice about how to tune the car's handling...

First of all, taking static weight off the back of the car will have no significant effect on weight transfer to the front under braking. Weight transfer (it's less misleading to think of it as load transfer) is 99% a factor of the acceleration/braking/cornering forces. The amount of increased weight on the front end due to the car pitching and rolling is insignificant.

Fundamentally, the end of the car with more static mass on it will have better grip.

Next thought is on the phenomenon of a "stiffer" setting giving the car more grip. What it does is control the contact patch of the tyre better, which can generate more grip. Or, it makes the car more responsive, which can be mistaken for more grip.

It's entirely normal for a car to have more grip with the anti-roll bar fitted, if the rear end rolls excessively without it.

The same with droop. More droop will give more grip. But because decreasing the droop makes the car more responsive, that can be confused with more grip.

Also, the "death groove" on the inside edge of tyres is nothing to do with camber angles. It's to do with the undersized inserts in tyres, which allow the tyre carcass to move freely and bend over on the inside edge when cornering. Don't worry about it.

To increase rear grip on turn-in off-power you should be increasing static weight on the rear end, increasing rear droop, decreasing pitch sensitivity under braking, and decreasing roll sensitivity on the front end amongst a number of other things. Small increments at a time and no great imbalance between front and rear.

That being said, I'm not much of a fan of XRAYs, and I think you would be surprised at how much difference a change of car would make.
On the weight side of things, I was actually informed by Paul Lemieux that having more weight at the front for more stability and he explained it the way I did, which was why I put it on my car. To be perfectly honest, I think the stock weight layout of the car is spot on and has been designed in such a way. I agree about the weight on a particular end of the car having more grip from experience, however it turns the other way when that end starts to slide. I do know about setup, but I feel getting advice from others might nudge me in the right direction.

On the spring side of things, I find the laptimes are near identical if I go up or down on the spring rate. I don't find harder faster or visa-versa. What I do find is excessive roll to be a big issue though. Its about having right amount of roll. I've tried no roll bars and the car is an absolute disaster.
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Old 08-16-2010, 04:08 AM   #35
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I have had the exact same problem with my 009 but using 32r's i tried loads of different adjustments to no avail. What has worked for me is pro squat in the rear and turn the speed controller settings down a touch especially the punch.
Hi Bilko, I saw your advice and added it to my other changes and it definately helped. Having less acceleration made the car stay good throughout a race distance and I FTD'd.

I also thickened front oil to 650, rear 450. I put the Rear toe in at 3.5deg, raised front roll centre, widened front end by 2mm, lowered rear shocks 1 down from stock and moved front and rear wheelbase positions back so the weight was further forward. The car was great for the way I drive, needing the rear end to stick into tight corners. The car still managed to carry great corner speed.
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