9" rims effect on handling?

[SC-targa]

I've asked this before, but never got any responses.

I see all kinds of folks slapping on a set of 9" Fuchs with 245/45-16 tire on the back of their 911s. If you don't add a set of bigger rear torsion bars, a huge rear anti-roll bar or 951 style 8" fuchs with 225/50s on the front, won't it have awful understeer?

Don't get me wrong, I'd love a set for the looks, but do the 9" wheels and 245's buy you anything, ecept looks, over 8" rims with 225's?

Regards,

Jerry Kroeger

[IROC]

I think you're over dramatizing the situation a little, but no there won't be a tremendous difference between the 245s on 9s and 225s on 8s. There is a difference, however.

I've got 275s on the rear and 245s on the front (a 30mm difference, if you want to look at it that way) and the car is very neutral. Why not put 225s on the 7s on the front and 245s on the 9s? Or...245s on the 8s in the rear and 225s on the 7s in the front? You have lots of options, really.

Mike

[Jack Olsen]

"Awful understeer" would be overstating the difference that 2/3 of an inch of tire width makes. Remember, the area of the contact patch is essentially the same on a 245 or a 185 width tire. But the shape of the patch, and its characteristics, change as you widen the tire. Jumping from a 185 to a 245 would produce fairly dramatic results. But the difference in handling from a less-than-one-inch jump is going to be more placebo than anything else, in my opinion -- unless you're fine tuning a car and looking to shave tenths of a second off your lap times.

The widest tire that can be easily used with either the 8-inch or the 9-inch rims is a 245. The handling differences between the two wheels with the same width tire would be negligible (again, in my opinion), although there is ultimately an advantage (however small) to the wider rim.

Plus, the wider ones look cooler.

The advantages of eights are that they're less expensive, and would give you slightly less unsprung weight than a nine with the same tire.

But if your budget or rulebook allow either, then the nine is the better choice. If I were in your shoes, I'd put a set of 245's on the eights, and see how you like the difference.

[II6]

I went from 6" & 7" to 7" & 9" on my SC, and the most obvious change was a decrease in car acceleration, and better grip in corners.

understeer difference was not a big deal.

[Bob's Flat-Six]

Hi, Jerry
I went with this combo recently 7's and 9's And I don't track the car so I don't have a lot of to compair to. But I have noticed a little more understeer with the 245's over the 225's that were in the rear which would be exspected as the front 205's rubber stayed the same.
I have 26mm rear torsion bars and sport Bilsteins and HD's up front.
I will say that I like the rear being planted with the bigger rubber as it seems my SC will plow now before the rear comes around and I can control the plow better, I think?
I guess if a guy was doing a lot of track 225's up front might be worth a try if the understeer became a problem.

Also worth noting is the S03's match up pretty well in the 245/205 combo IMO as the 205's seem to run big while the 245 didn't seem to put that much more rubber on the road than the 225's. But as they wear this relationship my change as the front's were worn 30% and the rears only about 10%, But so far so good.

Jerry,
Do you track the car? That may flavor some of the responses.

[MIK911]

Jack said:
Plus, the wider ones look cooler.

The advantages of eights are that they're less expensive, and would give
you slightly less unsprung weight than a nine with the same tire.
---------------------------
1)The 'wider ones'....meaning the 9" compared to 8"? They look pretty much the same, if you're referring to the lip depth.

2)Last time i priced the two, (at Wheel Enhancement), the prices for the 16x8 and 9's were pretty much the same.

With the 8's you have the option of 225 vs 245


Mike
'86 coupe w/ 16x7,8's

[Bill Verburg]

As others have pointed ou there is no gross change in handling behavior, there is a bit more understeer but not objectionably more, if you track the extra traction is nice in fast sweepers(understeer tends to decrease as speed increases). The most noticable change is the quicker acceleration of the slightly shorter 245/45 vs 225/50.

Overall it is a very positive change.

If you find it objectionable(which I doubt) what a great excuse to get adjustable sway bars.

[Bob's Flat-Six]

And Yes as Bill stated, My understeer is felt only in hard tight turns for the most part.

[ChrisBennet]

If you are experiencing a reluctance to turn in, just trail brake some.
-Chris

[911pcars]

As Bill suggests, that's why they have adjustable sway bars. Just tighten up the rear bar or loosen the front bar and you will have less understeer. Or merely increase front tire pressure/decrease rear tire pressure. The difference between 8 and 9" is subtle, but so are so many modifications. It's the sum of those modifications that make a difference.

Sherwood