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-   -   Understeer (http://www.clubcobra.com/forums/backdraft-racing/144230-understeer.html)

bobcowan 11-15-2020 07:19 AM

Understeer
 
I took the car to the skid pad yesterday for education and fun. This is the first time I've ever driven this car in anger. The race car is broken.

The understeer was HORRIBLE! I couldn't believe how bad it was. It occurred at significantly lower speeds than you would expect. It's so bad, you can't even use throttle oversteer to rotate the car.

How have previous owners fixed this?

t walgamuth 11-15-2020 07:38 AM

smaller front sway bar or add one to the rear or make it bigger.

1795 11-15-2020 07:44 AM

Bob,

I have not experienced any significant understeer on the race track, even on corners in which I am not braking for the turn, such as the uphill esses at Watkins Glen. In most corners, I am using some degree of braking, so that would put the weight on the front tires and minimize understeer (as you well know).

Looking forward to seeing what people have to say and if it is more prevalent with one style of cobra, versus another. What tires are you using? Do you think that the understeer is related to grip, weight transfer to the front, weight distribution, alignment? Just trying to hypothesize at this point.

Good luck.

Jim

spdbrake 11-15-2020 08:09 AM

A member named Bob whom you may know posted some pointers in the BDR forum in 2007.
http://www.clubcobra.com/forums/back...ndersteer.html

But seriously...I'd PM Grey65 as he has the most experience in BDR suspensions. Club Cobra - View Profile: Grey 65

FredG 11-15-2020 12:04 PM

Grey 65
 
Agreed. I have spoken to Kevin on the phone about my front suspension, ride height and spring rates. Very knowledgeable and very helpful.

Fred





Quote:

Originally Posted by spdbrake (Post 1485284)
A member named Bob whom you may know posted some pointers in the BDR forum in 2007.
http://www.clubcobra.com/forums/back...ndersteer.html

But seriously...I'd PM Grey65 as he has the most experience in BDR suspensions. Club Cobra - View Profile: Grey 65


bobcowan 11-16-2020 08:33 AM

OK. I'll start with the basics and work up from there. I was hoping someone would say, "Oh, yeah. Common problem. Here's how to fix it." :)

On Sat, I was a bit dismayed about how poorly the car handled during the various exercises. But by Sunday afternoon I was actually kind of glad. It forced me to learn how to manage it. If the car had handled perfectly, I might not have learned as much.

FredG 11-16-2020 09:29 AM

Old Thread
 
I remember your old thread. I thought you were all dialed in.

http://www.clubcobra.com/forums/back...ght-stuff.html

Fred




Quote:

Originally Posted by bobcowan (Post 1485341)
OK. I'll start with the basics and work up from there. I was hoping someone would say, "Oh, yeah. Common problem. Here's how to fix it." :)

On Sat, I was a bit dismayed about how poorly the car handled during the various exercises. But by Sunday afternoon I was actually kind of glad. It forced me to learn how to manage it. If the car had handled perfectly, I might not have learned as much.


tocheck 11-16-2020 11:47 AM

How old are your tires?

bobcowan 11-17-2020 07:24 AM

Quote:

Originally Posted by FredG (Post 1485343)
I remember your old thread. I thought you were all dialed in.

http://www.clubcobra.com/forums/back...ght-stuff.html

For the street, it seemed to be pretty good. This is the first time I've ever driven the car in anger. Nothing like an autocross to point out the weaknesses. :)

The brakes are excellent. Got to be careful not to lock the brakes when traction is a bit iffy.

The rear is amazing. You really have to work at it to get the rear to step out. The rear just hooks up and goes. To rotate the car you have to lift, then blip the throttle. A very quick up-down-up. Otherwise it will just push the car in a straight line.

Fred

Quote:

Originally Posted by tocheck (Post 1485349)
How old are your tires?

The front are only 3 years old, 9,000 miles, Nitto NT-05; a 200 tire. The rears are new this year. Nitto NT-05, a 140 tire.

cycleguy55 11-17-2020 03:03 PM

Quote:

Originally Posted by bobcowan (Post 1485394)
The front are only 3 years old, 9,000 miles, Nitto NT-05; a 200 tire. The rears are new this year. Nitto NT-05, a 140 tire.

Older, harder tires on the front and you have understeer. Coincidence?

1795 11-17-2020 03:17 PM

The grip on the rear tires is greater than on the front (140 vs 200), which would possibly contribute as well.

tocheck 11-18-2020 08:24 AM

The width of the tire also plays a large roll.

bobcowan 11-18-2020 12:12 PM

By design, the front of the car will have less traction than the rear. That's just a given with these cars. Simply looking at the width of front vs. rear tires will give you a big clue.

My front tires are not "old", just not as new as the rears.

The difference in this car is astounding. I've put a lot of miles on more than one Cobra. A lot of track miles, too; I won 5 regional championships in a Cobra. I have a pretty god idea on how they should handle.

I have a couple of projects to finish, then I can turn my attention to the Cobra again.

t walgamuth 11-18-2020 01:35 PM

Is it a locker rear end? Maybe pushing with both rear tires is doing it.

6TNCRZY 11-18-2020 03:20 PM

Good point. A Detroit Locker or True Track diff will allow rear tires to turn at different speeds until throttle is applied which will facilitate better initial turn in.

bobcowan 11-18-2020 04:06 PM

It's a BMW limited slip IRS diff, 3.54 gears.

While I was out in the garage today, I took a quick look under the car. It has a large front bar, around 1.25'ish". The rear bar is much smaller, like 3/4" or so. I think my first step will be to disconnect the front bar and see what happens.

t walgamuth 11-18-2020 04:52 PM

Quote:

Originally Posted by bobcowan (Post 1485471)
It's a BMW limited slip IRS diff, 3.54 gears.

While I was out in the garage today, I took a quick look under the car. It has a large front bar, around 1.25'ish". The rear bar is much smaller, like 3/4" or so. I think my first step will be to disconnect the front bar and see what happens.

Be careful, the rear will want to break loose with no bar on front, perhaps.

bobcowan 11-18-2020 08:19 PM

It very well could! That might even be kinda fun. In an empty parking lot. :)

t walgamuth 11-18-2020 08:35 PM

There you go.;)

Grey 65 11-21-2020 04:56 AM

Quote:

Originally Posted by bobcowan (Post 1485394)
The front are only 3 years old, 9,000 miles, Nitto NT-05; a 200 tire. The rears are new this year. Nitto NT-05, a 140 tire.

NT-05 is a 100% crap tire.. they are sticky(ish) for maybe 2 months, then they become total blocks of ice.

What are your wheels sizes?

What are your tire sizes?

What tire pressures are you using Front and Rear?

BTW: My car is setup with a touch of oversteer (I autocross) and I do not have a rear swaybar on my car at all.


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