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-   -   Understeer (http://www.clubcobra.com/forums/backdraft-racing/81921-understeer.html)

Rwillia4 09-01-2007 10:32 PM

Understeer
 
I have a ton of understeer, it just wants to dig. Front and rear tires are at 28psi. I could be going in the corners to hot but it just doesn't want to change direction. I'm going to lower the rear pressure to 24 psi and try again. Anyone else have this problem? Any suggestions?

mobilenuke 09-01-2007 10:35 PM

Front springs?
 
What lb front/rear springs are you running?

jeff

Rwillia4 09-01-2007 11:57 PM

I have the M3 race setup , I'm not sure of the Lb rating

lovehamr 09-02-2007 12:35 AM

What tires? Unless they are race slicks that pressure is way to low and may be allowing the tire to roll under onto the sidewall. Have you taken any tire temps?

Steve

Rwillia4 09-02-2007 01:14 AM

They are the Nittos. And the car is only 2500# so tire load it not that great. Currently the walls are no where close to the edge of their traction area (as seen by the scuffs) in the fronts or backs. No roll of the sidewall has been noted. Just a push.

Steve- do you have a better way to get more neutral?

dlampe 09-02-2007 08:47 AM

If they are 17 in, you really need to start at 30 -32 pounds and check them hot with a target of 36-37 pounds. If they are 15in then the target heat range is 30 pounds as a general rule. If that doesn't help, you will need more swaybar in the back or less in the front, heaveir springs in the back or less in the front. You might try more pressure in the rear but if it is severe, thats probably not going to get the job done.

Bailey 09-02-2007 10:08 AM

Hey Rob,
For perspective my street wheels and tires are at 24fr 26 rear, and the DOT track 17s are at 22fr and 24rear. Tire pressure and alignment play a big role with these cars, and also pressure differential between front and rear. BDR also offers a set of stiffer springs if you are interested. My car with the M3 bits still felt like a sponge. The springs really woke up the beast, no regrets.
Good luck and enjoy the ride,
Richard Bailey

bobcowan 09-02-2007 12:11 PM

Bailey is on target.

I use 17 street and track tires. Cold air temps are 24-26 psi. Which allows the hot tire pressures to be around 32psi. Optimal pressure and camber can only be truly determined with a tire pyrometer. I bought one off e-bay for $40.

Carefull Alignment is the key to good handeling. All the right race parts won't perform well if alignment and ride height is off. Too much toe in will really cause an understeer.

Have you checked bump steer? If your springs are soft and you have a lot of bump steer, as soon as the nose dives your toe in will be significant.

Do you have sway bars? Less front bar or more rear bar will help improve understeer.

Rwillia4 09-02-2007 04:04 PM

I have the 17's, race springs and, sway bars front and rear. I play with the tire pressure some more to see what. The alignment is in specs along with getting the ride height as low as possible with respect to the camber spec. I think the toe is 1.5-2 degrees.

Bob- Bump steer? what is that and how can I check it?

Steve- Are the race springs ABOVE the $4500 race package?

thanks for all the help

SkipB 09-03-2007 01:06 PM

Rwillia4

Introduce right foot to gas pedal and eliminate all your understeer very quickly. But, get ready to catch the rear end coming around behind you.

SkipB

Rwillia4 09-03-2007 10:39 PM

Skip,
I am fully aware of the right foot modulation :), even then it is still a pig and wants to snap right back to understeer. I'm still trying to decrease my overall radius thru turns.

cycleguy55 11-15-2020 04:21 PM

Quote:

Originally Posted by Rwillia4 (Post 774260)
I have the M3 race setup , I'm not sure of the Lb rating

What's the F/R weight of your car vs the target F/R weight that setup is designed for? Between the springs and sway bar you may have too much roll stiffness in the front. If so, you'll need to reduce it in the front, increase it in the rear, or both.

6TNCRZY 11-16-2020 07:50 AM

If you want the front to bite on sharp turn ins, you need negative camber on the front, -1* or more. More rear roll stiffness will help too.

MKS427 11-16-2020 03:42 PM

Factory Five recommends 22psi cold for 17" tires. It really helped just for street driving. On the Nitto NT-01s you will see triangles on the sidewall close to the tread. When you are scuffing close to the tip of the triangle, you are close to optimal pressure.

t walgamuth 11-18-2020 11:36 AM

I tend to agree with the fellow who recommended 24 front and 26 rear as a start point.

spdbrake 11-18-2020 12:33 PM

Btw guys you're replying to a 13 year old thread. Bob Cowan started another thread this week in the BDR forums with the same title though.

t walgamuth 11-18-2020 01:33 PM

What a dirty trick!

;)


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