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Old 08-09-2010, 09:11 AM   #16
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Hi, I race indoors in the UK on a low/medium grip carpet track. My car is an Xray 009 with Sorex 28R tires.

Its summer here and i'm having strange handling issues and i've come to the conclusion that the heat is causing the problem and has been for some time. My car also has a lot of power, even with a 13.5 because of having a SP esc with the latest firmware which also exagerates the problem.

When I take out the front screws from the top deck (which you're not really supposed to do as per Xray manual on carpet) the car has horrendous snap oversteer on entry and mid corner, which is why i'm also sure tire temps have hit the roof, because it's no where near as bad in the winter. Even with all screws in barring the front post, the car is better but the problem is less. General setup changes to the car don't solve it, unless I stick on new tires that last 2 runs and then the snap returns!

My tire temps are - FrLeft 83F - FrRight 86F --- RrLeft 83F - RrRight 83F.
To me this seems too high for Sorex 28R tires. I want to stick with this tire, as a lot use it at my club and at the big events its the tire of choice. What setup changes would drastically cool the tires down, other than changing the tire to a higher temp version like 32Rs?
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.
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Old 08-09-2010, 09:54 AM   #17
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By the sound of it he has problems off power which does not necessarily have anything to do with tires. That being said, Sorex tires are exactly like that, they have good grip for a little while when new and then are useless. We had the same problem at our track and changed to Sweep 24 with aqua inserts and fixed it.
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Old 08-09-2010, 10:00 AM   #18
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If you ant to make your car much easier to drive just simply only sauce the inner half or 1/4 of your front tire. It works great as a tuning option. I have barely every sauced more than 3/4 of my front tire.
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Old 08-09-2010, 11:56 AM   #19
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Maybe you should post your problem on Paul Lemieux's thread... if anyone can help you he would be the one
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Old 08-09-2010, 12:08 PM   #20
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Aside form what i posted in the 09 thread; try a diff set of the same tires or rotate them. I spent an hour once trying to figure out why i had a similar problem. tires are very critical.
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Old 08-09-2010, 01:34 PM   #21
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This will sound extreme, but after going thru 2 T2 '009 EU cars, which I could never get to perform decent, I went back to a T2 '008 and had a great deal of success. Never could get the 009 to work for me even when duplicating setups or radical adjustments, or having Paul hands on the car. JMO
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Old 08-09-2010, 04:29 PM   #22
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If you ant to make your car much easier to drive just simply only sauce the inner half or 1/4 of your front tire. It works great as a tuning option. I have barely every sauced more than 3/4 of my front tire.
You're right, but I find doing half the front tires with additive to last about 7 laps and then the car turns back into an old Porsche 911 Turbo!
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Old 08-09-2010, 04:30 PM   #23
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This will sound extreme, but after going thru 2 T2 '009 EU cars, which I could never get to perform decent, I went back to a T2 '008 and had a great deal of success. Never could get the 009 to work for me even when duplicating setups or radical adjustments, or having Paul hands on the car. JMO
LOL. Funny you say that as I recently put the 009 chassis on to make it a 009 converted from a 008! - To be honest, I had the same overriding problem with the 008.
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Old 08-09-2010, 04:50 PM   #24
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By the sound of it he has problems off power which does not necessarily have anything to do with tires. That being said, Sorex tires are exactly like that, they have good grip for a little while when new and then are useless. We had the same problem at our track and changed to Sweep 24 with aqua inserts and fixed it.
Heres the thing - when I had the 008, I had really woeful issues on the Sorex 28R with grey medium inserts at the carpet wars events in the UK, as that was the only tire allowed. After a few months of trial and error, I got the car to handle absolutely brilliantly on them and (im not joking) they are still in my box at 6 months old. The car handles all day without weird handling still on those very tires.

A few months back, I decided to buy a Mamba Max Pro and at the same time the car couldn't do good laptimes. I kept using it for a few weeks thinking the old sorex greys coudn't take the power, so I put on Sorex JB 28rs as they have more grip. The difference between the JBs and the Greys is the JBs have a bigger air gap and are softer, whilst the greys are firmer and have a smaller air gap. I figured out after a few weeks that the esc had so much torque that it was spinning the tires up out of every corner and whilst it didn't look that bad driving it, I was told by someone that they could hear it and indeed that was causing the bad laptimes, not the old tires. In the meantime I stuck with the Sorex JBs.

It seems to me, whilst the JBs have a better laptime in the region of 2 tenths, they go out shape as the dreaded line of death appears on the inside of the tire after 4 runs. Also, this concides with the start of the snap oversteer off throttle characteristics. I'm wondering for the sake of maybe 0.150 per lap, its better going back to the greys so I can at least have them work for months, rather than one good day as what happens is the insert is so flush against the tire that the tires isn't being allowed to pull away from the insert in corners so there is never any line going down the tire and they wear brilliantly without loosing a lot of grip. I use the JB inserts because everyone else uses them in club meetings and I didnt want to be disadvantaged (;-)

I'm thinking that maybe, the Sorex JBs are simply good for 1 race meeting (or 3 heats) before the car snaps all over the place, as my car is good on brand new Sorex JB tires, but for a short amount of time. I'm seriously considering reverting back to the greys in the sake of loosing a few tenths. Now I just have to remmeber what that setup was (;-)

Last edited by maxg123456; 08-09-2010 at 05:04 PM.
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Old 08-09-2010, 05:27 PM   #25
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Well I never did any carpet racing or used your current tires but on asphalt I only started having issues when the tire reached 120+ degrees. If a tire is over heating you can usually see the rubber pealing off the tire a little.

Maybe the rubber just has a little to much flex after the tire gets worked in a bit? Could you trying using foam that gives you less of an air gap?
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Old 08-09-2010, 06:46 PM   #26
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It would be unlikly to be the tires (make sure you are running same inserts as every one else tho)

I would try looking else where:

Are you running a gear diff in rear?

my 009 did the same thing, and it turned out to mainly a weight positioning thing on the chassis, try putting weight more forward or back.

if running a gear diff rear, try a ball diff.

Also try spool up front if not already.

try playing with roll centres, even try the opposite to what the book says (trust me)

try thicker oil in shocks all round.

less drag brake

try them all
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Old 08-10-2010, 02:54 AM   #27
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It would be unlikly to be the tires (make sure you are running same inserts as every one else tho)

I would try looking else where:

Are you running a gear diff in rear?

my 009 did the same thing, and it turned out to mainly a weight positioning thing on the chassis, try putting weight more forward or back.

if running a gear diff rear, try a ball diff.

Also try spool up front if not already.

try playing with roll centres, even try the opposite to what the book says (trust me)

try thicker oil in shocks all round.

less drag brake

try them all
Hi, I've been running a ball diff. In regards to the weight thing, I got the idea from Paul Lemieux to move the front and rear arms furthest back in order to get full forwards weight on the car, as thats supposed to give more stability (less transfer to the front off throttle). That was a bit better, but my laptime was definately compromised a lot, so I scrapped that.

Now you mention the gear diff, I already bought one of those to try out for when the car is much better to drive. Im interested why you mention the gear diff can cause the off throttle problem?

I use a spool as per xray 009 carpet setup.

I'm liking the thicker oil idea, as i've got that ready for the next race
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Old 08-10-2010, 03:22 AM   #28
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Originally Posted by maxg123456 View Post
Hi, I've been running a ball diff. In regards to the weight thing, I got the idea from Paul Lemieux to move the front and rear arms furthest back in order to get full forwards weight on the car, as thats supposed to give more stability (less transfer to the front off throttle). That was a bit better, but my laptime was definately compromised a lot, so I scrapped that.

Now you mention the gear diff, I already bought one of those to try out for when the car is much better to drive. Im interested why you mention the gear diff can cause the off throttle problem?

I use a spool as per xray 009 carpet setup.

I'm liking the thicker oil idea, as i've got that ready for the next race
if it gets worse throughout the race then it's tyres/additive IMO.
either your additive routine isn't quite right (additive is gone after a few minutes) or you're doing something weird in terms of weight transfer. What droop are you running fr and rear ?
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Old 08-10-2010, 07:38 AM   #29
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if it gets worse throughout the race then it's tyres/additive IMO.
either your additive routine isn't quite right (additive is gone after a few minutes) or you're doing something weird in terms of weight transfer. What droop are you running fr and rear ?
I clean the tires first, then 15-20 minutes before running I apply LRP carpet additive for rubber tires. before I go out to the track I dry off with kitchen roll. I usually do downstops at 6 front - 5 rear. I vary the front sometimes with 6.5, because it makes the car feel nicer to drive. I have tried as much as 7 at rear and believe it or not, the car still flicks even though its less.

Springs -
F 2.8 (tried 3.0, car is even worse)
R 2.6 (tried softer and car snaps but later)
Anti Roll bars - F 1.4 R 1.2/1.3
Shock positions standard for xray 009
Rear links - i've tried everything but the car has the same inherant problem.
Bodyshell - Mazda Speed 6
Stock Carpet top deck.

Heres one, what about if I put thicker Oil in the front shocks,
like 550cst ft - 350cst rr?
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Old 08-10-2010, 08:05 AM   #30
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Quote:
Originally Posted by maxg123456 View Post
I clean the tires first, then 15-20 minutes before running I apply LRP carpet additive for rubber tires. before I go out to the track I dry off with kitchen roll. I usually do downstops at 6 front - 5 rear. I vary the front sometimes with 6.5, because it makes the car feel nicer to drive. I have tried as much as 7 at rear and believe it or not, the car still flicks even though its less.

Springs -
F 2.8 (tried 3.0, car is even worse)
R 2.6 (tried softer and car snaps but later)
Anti Roll bars - F 1.4 R 1.2/1.3
Shock positions standard for xray 009
Rear links - i've tried everything but the car has the same inherant problem.
Bodyshell - Mazda Speed 6
Stock Carpet top deck.

Heres one, what about if I put thicker Oil in the front shocks,
like 550cst ft - 350cst rr?
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.
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