h33
Pit Crew
Posts: 8
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Post by h33 on Feb 11, 2020 5:03:18 GMT -6
Hi Guys, I am new to the site so please take it easy lol. i do not know most of the terms so will be googling. I have an Bmw e30 that i am using for dirt oval track racing here in South Africa (We race anti clockwise...). My springs are as follow FL = 550 RF =450 LR = 200 RR =170 My cambers: FL = 1 Deg Pos. FR = 4.5 Deg Neg. LR =0 RR = 0 Toe : FRONT = 6 mm Toe out LR = 1 DEGREE toe in RR = 0 deg. Caster : Not sure what the caster is in FR but the wheel has been moved forward by modifying the lower control arm I have the following spacers on the wheels: LF = 25mm RF = 50mm LR = 25mm RR = 50mm Cross weight : 51.8% (left rear to right front) I tried stagger wheels at the rear.... LR=205/60/15 RR=205/65/15 ( only allowed to use normal road tyres ) I had allot of under steer in the middle of the corner so i had to climb of the gas through out the corner and then only accelerate on corner exit. ( the track seemed to be les traction than before , but i must say that i have after my last race changed to wider rims, and also installed the spacers. so i am not sure what the spacers would do on the handling and also the grip on that wheel.) Was i correct by installing the spacers? I heard that its better not to have spacers on the rear end because having the rear wheel closer to each other results in more traction.. is this true? I installed the spacers to have an more stable car.. (at least what i thought, the car did feel more stable but it didn't want to turn.) Before my last heat i turn my LF spring up with 2 turns and it seemed to have made an big difference making the car turn in better. i now had to slide it through out the turn braking the rear loose. (also i am not sure if the better handling and grip came from the track that started to dry out a bit more as the night went on). The car is straight forward with a little bit of changes, independent rear suspension, and i took the anti-roll bar out in front. Can you guys give me some pointers please. I do not have the cash to get my car setup by professionals. Any advise would be GREATLY appreciated... What is your thoughts on my setup... Thanks in advance... Read more: thedirtforum.boards.net/thread/1588/cornering-issues-understeer#ixzz6Ddr721Or
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one8
Fourth Place
Posts: 52
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Post by one8 on Feb 12, 2020 17:52:15 GMT -6
What are your total weight and corner weights? Also the rear weight percentage and tire pressures? I would swap the front springs and lower the rear air pressures as the track gets slick.
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h33
Pit Crew
Posts: 8
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Post by h33 on Feb 13, 2020 6:31:48 GMT -6
Hi,
My weights are as follow..
LF: 289.0 kg (25.3%) RF: 317.0 kg (27.7%)
LR: 276.5 kg (24.2%) RR: 261.5 kg (22.9%)
Total weight: 1144 kg
This is with me in the car (and its right hand drive)
Thank you in advance.
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one8
Fourth Place
Posts: 52
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Post by one8 on Feb 13, 2020 15:15:42 GMT -6
You definitely need to move weight around. Since you run counter(anti) clockwise. Your setup should be similar ours. I would leave the cross weight for now but you have 53% front weight. I would move that to the rear. At least 51-52% for now. Your left is only 49%. That should be around 52% also. You said you removed the front anti roll bar. Is there one on the back? We don't use anti roll bars at all. Ride heights should be about an inch (2+ cm) higher than the front.
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h33
Pit Crew
Posts: 8
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Post by h33 on Feb 14, 2020 0:05:52 GMT -6
Ok, so i will have to cut my firewall to accommodate the engine back? Currently the engine is about 1 cm clear from the firewall. Running an m30b35 engine.
Because i am sitting on the right hand side of the car. is it possible to set up the car that it has an higher weight on the left? i have tried it once but then the left hand side of the car stands higher than the right side.. Would this create problems?
my battery box is fitted on the front passenger (left) side floor. Plus my fuel tank is mounted in the far left side of the boot-lid.
There is no anti roll bar at the back...
Thank you for your info. i really appreciate it.
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h33
Pit Crew
Posts: 8
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Post by h33 on Feb 14, 2020 0:14:47 GMT -6
Sorry for all the questions.. lol
Also can you tell me what is the difference between having wheel spacers in the car and not having. I heard now from people that if you have spacers in the rear that you will loose traction? According to them the closer the rear wheels are to each other the more traction it makes? I installed them because i thought my car would be more stable through the corners..
I am in the dark with this now.. lol. Thought that i was doing good, but not so sure anymore..
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one8
Fourth Place
Posts: 52
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Post by one8 on Feb 14, 2020 7:44:20 GMT -6
I assume you have a roll cage installed? If so can you mount ballast weight in the car? We use large lead weight for ballast mounted to the roll cage in the boot or engine compartment. I would move the battery to the boot as well. As for the wheel spacers, since you are fighting an understeer I would remove all but the right rear and try that. Remember to always scale the car in race trim. Tire pressures set and fuel level at whatever you start the race with and the driver in the car.
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h33
Pit Crew
Posts: 8
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Post by h33 on Feb 17, 2020 4:05:15 GMT -6
Hi,
Yes we do have roll cages.
I took the car out on the track this weekend for some testing (left the car the same way that it was from my last race just to make sure before we start adjusting things). The track wasn't prepped so dont know if it will help but, i find it hard to get the nose to turn in at corner entry. Once i get the nose in then i have to break the rear loose and pedal it through the turn. otherwise the car goes into understeer again. i couldnt complete the practice, the motor ran an bearing in the corner. (very sad)..
Thanks for the info. i really appreciate. i will try and fix the motor and the cause and then climb back into handling issues.
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one8
Fourth Place
Posts: 52
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Post by one8 on Feb 18, 2020 10:54:27 GMT -6
Hate to hear about the motor issues. As for the understeer in the corner. You right front spring is too light. A light spring won't put the pressure onto the tire to get it to bite and turn. That's why I suggested swapping the front springs.
Good luck.
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h33
Pit Crew
Posts: 8
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Post by h33 on Feb 24, 2020 1:13:52 GMT -6
Thanks for this info one8 . I always had the harder spring in the RF position. until people told me to put it on the LF to get inside wheel to push more into the corner and pull the car through the corner. I will swop them back again. Also what I find is with the 2 low rear spring rates I do not get much weight transferred when I adjust the rear springs.. also thought about going heavier springs at the back?? Currently have LR 200 and RR 170. what do you think about LR 200 and LR 250 or 300 to keep that LF wheel on the ground? Thanks in advance.
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one8
Fourth Place
Posts: 52
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Post by one8 on Feb 24, 2020 13:37:11 GMT -6
I understand the thinking about heavier spring on the left front. But it's more effective to tune the left with Ackerman and bump steer than a spring. Again. When you enter the corner and stab the brake, if you brake, the weight transfer to the front will not be transferred to the rf wheel if the spring is too light. Since your weight is transferring to the right and forward the rf is the corner you need the stiffer spring. A heavier on the lr will help get more traction on that tire to help drive off the corner and to induce a little understeer on corner exit. How you drive the car is a huge factor also. If you try to drive the car through the corner like an asphalt car it will almost always have an understeer/oversteer issue. I drive deep into the corner, tap the brake and crank the steering wheel hard left to get the weight transferring forward and right. Don't forget about tire pressures either. If you're getting close with the setup tire pressures can do a lot to help. Understeer into the corner, add a couple of psi to the right rear. Oversteer would be the opposite. I've heard the rear suspensions on your model car have quite a bit of bump steer. I would check to make sure that's not hurting your corner entry also.
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h33
Pit Crew
Posts: 8
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Post by h33 on May 18, 2020 23:49:22 GMT -6
Hi one8,
Thank you for all the help and info you are giving me. Its really appreciated..
With this Lock Down going on one cant test our cars... (hope you guys are still safe)
Do you mind explaining to me how this is done.. I quote from your previous message "But it's more effective to tune the left with Ackerman and bump steer than a spring".
In the meantime I am putting the car on a diet. busy making fibreglass doors, bonnet, boot, and fenders.
I will also look into the bump steer issues in rear suspension thank you. as mentioned I am new to the car setup and don't even know what the difference will be between bump steer and no bump...LoL
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one8
Fourth Place
Posts: 52
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Post by one8 on May 19, 2020 14:55:09 GMT -6
Hi k33
Glad to hear you're doing well! We're doing well here. Texas hasn't been affected to bad by the virus. I hope you have you engine issues worked out.
First i would say be careful using fiberglass. If you take a hit in the door or end up rear ending someone, there will be a lot of splinters and shards flying around. We skin our doors and hoods(bonnet) with thin aluminum. Easy to pull off and bang out the dents and rivet back ob. Fire, God forbid, also is an issue with fiberglass.
Ackermam is the affect of the steering geometry on the inside wheel as you corner. When you enter the corner the car will roll to the outside which will put the inside suspension in droop. With the tie rod being a different length that the suspension control arms this causes the wheel to turn more to the inside of the corner. Too much Ackerman turns the wheel too far inside and you'll be skidding the tire across the track. Too little Ackerman and the inside tire will want to push the car to the outside of the corner. Bumpsteer is the opposite. It is when the suspension is in compression. There are a bunch of places on the web or YouTube that explain it and how to set it best for the track.
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