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View Full Version : Question on F/R Tire Sizes


SuperG
04-27-2006, 12:09 PM
I had planned on using 275's up front and 315's in back, when it was suggested the rears will induce push (understeer). So first of all, how do most Cobras (mine is a '97) handle in stock trim...over or understeer (I guess the latter)? Second, do you agree that over/understeer is a relative term? That is, if my car oversteers through a particular turn at say, 50 mph, and I remedy the situation with something like wider tires in the rear, either over or understeer will now occur at a higher speed through the same turn?

I have no idea how the car truly handles at high speeds. I have taken slow turns and sharp turns at higher than normal speeds and felt very stable...perhaps that suggests a good balance and I stick to the same tire sizes front and back (then again, I have 245/265 F/R).

Any help is much appreciated!

Cobra-R
04-29-2006, 10:51 PM
Gary,
These cars have way more capabilities than 95% of us, with that said, yes they are set up to favor understeer. There is alot a good driver can do to drive around a understeering car on the track (Driving at the cars limits arent going to happen on the street) Late apex's, trail braking, slow in....fast out are a few of them. If you want to put more tire on the car, do it and enjoy it. You can almost never go wrong getting a larger contact patch with the pavement. :thumbsup:

Brian

SuperG
04-30-2006, 01:24 AM
Gary,
These cars have way more capabilities than 95% of us, with that said, yes they are set up to favor understeer. There is alot a good driver can do to drive around a understeering car on the track (Driving at the cars limits arent going to happen on the street) Late apex's, trail braking, slow in....fast out are a few of them. If you want to put more tire on the car, do it and enjoy it. You can almost never go wrong getting a larger contact patch with the pavement. :thumbsup:

Brian
Yeah, until now, the largest tires I ever had in my life were 245's, although on the track only 225's!! So I really look forward to using the 315's on the track (perhaps on the street for looks!). But if for some reason the car feels funky, I happen to have mor tires ready for use, so I can try a few combinations.

Bartman01
04-30-2006, 02:21 AM
If your car has understeer (front pushes wide in the turn), then adding more rear grip will only add to the problem. Mustangs (along with 99% of all passenger vehicles) are set up from the factory with slight to bad understeer, since this is 'safer' for the general public. Your Cobra is no exception. In stock trim, it will tend to understeer. Adding more rear grip via wider tires will add to this problem. Having more rear grip also makes it harder to induce throttle oversteer to correct the understeer (breaking traction on the rear tires to line them back up with the front).

Over/under steer is not linear - the faster you take a turn, the more likely the car will push or understeer.

Personal recomendation:
Knock yourself out for street/show use.
For track days (not drag days), stick to the same size all around for better handling.

BTW - I just went from 245's to 275's (on a 9 inch wide rim) all around, and have noticeably better traction.

SuperG
05-01-2006, 08:19 AM
If your car has understeer (front pushes wide in the turn), then adding more rear grip will only add to the problem. Mustangs (along with 99% of all passenger vehicles) are set up from the factory with slight to bad understeer, since this is 'safer' for the general public. Your Cobra is no exception. In stock trim, it will tend to understeer. Adding more rear grip via wider tires will add to this problem. Having more rear grip also makes it harder to induce throttle oversteer to correct the understeer (breaking traction on the rear tires to line them back up with the front).

Over/under steer is not linear - the faster you take a turn, the more likely the car will push or understeer.

Personal recomendation:
Knock yourself out for street/show use.
For track days (not drag days), stick to the same size all around for better handling.

BTW - I just went from 245's to 275's (on a 9 inch wide rim) all around, and have noticeably better traction.
Hey Bart! You know, you are probably right, and I began planning for 275's all around...but I have these 315's and they look so BAD A$$ I gotta use them!! So maybe if/when I am comfortable on the track and really begin stressing te car around the turns, I will need to reduce the understeer in such a way the rears have to stay??!!