Fuchs 8" vs 9" question
 

Just wondering from those who have gone froms 8s to 9s in the rear.

I can barely tell the difference visually, if at all, between the two, but is there any noticible difference in "stickiness," especially on the track? Assuming the same tires and size, is there a considerable improvement, or is it more subtle? Thanks in advance, all!

Edward

I 've done that, and you are right. There is not much visual difference. Tire wise, my 8s had 225s whereas 9s have 245s

It's bragging rights. Like H1s vs H4s...

-Wayne

Any detailed pics of both ?
Here are some 9x16

[img]
http://forums.pelicanparts.com/uploads6/fuchs+9x16+new1128539426.jpg[/img]
http://forums.pelicanparts.com/uploa...1128539615.jpg

I'd have to agree, its the 245 of the rear that helps. Unless your going to go with a 225 up front ( with a 8"951 rim) then a better balance might be the 205-225 set up with 7's and 8's.

What? you don't need 9s to run 245s.

How? For the Toyo RA-1 DOT R tire I like to run in 245/45-16 the recommended wheel width is 8".

I know the racer's argument about sidewalls being more stretched out and that being somehow better but I think the tire manufacturer's recommendation is good enough for me.

Thanks for the input, all ...keep it coming.

But I have run 245s on my 8s with no squirreliness whatsoever. In fact, it feels really planted on the track (w/205s on 7s), and this with street tires, not r-compounds. Agreed that 9s would be better for 245s, which is why I asked the question in the first place. But if you look at 245s on 8s, there is no bulging, and the sidewalls "seem" pretty well supported. I was just wondering that given the same 245, is there a marked improvement with the 9? Thanks!

Edward

Once again the measuring rim has been mistaken for the recommended rim. Toyo has a recommended range of rim sizes. for the 245/45 x16 RA-1 comp radial this is 7.5" - 9", what they don't tell you is that max performance from a given tire will almost always be obtained by using the widest wheel in the recommended range. This last tidbit is a fact not a fairy tale

OK Bill, I was not aware of this (obviously). Can you characterize the difference in performance between a 245/45-16 DOT R tire on an 8" rim versus the same tire on a 9" rim? Thanks in advance.

Abit OT, but should I add 14mm spacers on the rears ? Would widening the track decrease oversteer ?

The wheel has geater leverage on the tire carcass, the sidewalls are effectively stiffer, the tread squirms less, the tire runs cooler and at lower slip angles. These are all good things from a performance perspective.

The bad side(to some) is that the ride is harsher.


there have been many back to back timed tests of this concept;)

Nines are obviously better. But how much better, in practice, is a valid question. I've driven both, and the differences weren't noticable at all to me. In a race between a car with 245's on 8's and one with 245's on 9's, it'd likely be other factors that would make one car faster than the other.

Thanks Bill,
should I increase stud sizes for these 15mm spacers ? or they will have enough threads to be safe ?

OK, what you say makes sense.

Where? or what do I search for. very interested.

Thanks,

Doesn't it also seem that it depends on the tire mfg?

-I had 255's on the rear of my 928s4 on cup alloys (9 or 9.5 wide) with AVS sports, and i swear they looked narrower than my previous 245's which had been dunlop sp8000's on the stock phone dials, it was more of a visual thing, but really, they looked narrower than the smaller tires??

wider rear track will increase oversteer

I think that Grassroiots my have done one recently. Some of the tire manufacturers have published this info, Michelin for sure.

ok, I will try to find those. thanks again, Bill.

One other small factor should be noted, If you have a limited slip and you go with 245's they will really grab out of the tight stuff, especially when get on it early, which will make the car want to go in a straight line not good on the street. I have 7 x 16's and 8 x 16's with 225 50's with my 60% ZF, I tried 245 and it flet like a swamp buggie with the front wheels in the air cranked the in opposite direction

Can we see more than just the wheel. :rolleyes:

A lsd will mak any set up under steer more, the higher the lockup % the more effect it has, thats why, for a mostly street driven car 40% is as high as I would want.

An even better setup is a split 40/60 lsd

Your right, when the trans was apart I had it set up at 60% thinking I would do more track time but it turns out It's alot more steet time. I can only imagin what the early turbo drivers felt when the got on it out of a short freeway sweeper....anybody still out there who can comment on the 75/76 turbo with LSD... not the 4-way/windowpane

For a Turbo. These are significantly heavier in the rear the a narrow body car that most are changing to. Still works but I like more rubber up front to match the 245.

Ahhh, that's what I was looking for ..an opinion based on having tried it. Thanks, Jack!

Thanks for all the chiming in. Obviously I'd *like* to have 9s for the aforementioned advantages, but if there's no significant *felt* benefit (at my skill level, anyhow), then I'll stop dreaming and budget for other goodies. Thanks, all!

Edward

Ahhhh ..... Bill V... do you want to rethink your answer about wider rear track will increase oversteer?

You are the admitted Grand Master on brakes and wheels.....but think this one through once more....

Wil :)

Yes, I meant to say wider rear track will increase understeer

If you're gonna run 8s and 9s, why wouldn't you just use 225 and 255 tires?

Depends on which wheel diameter you're talking about.

16's are not readily available in a 255 section width that's the appropriate size. The most common size is 255/50 which is an inch taller than appropriate. More common rear sizes are 245/45 and 245/50. The 245/45 is the right size for our application. Front choices for 225 front are 225/50 or 225/45. The 45's are usually the better choice to avoid clearance problems (shorter OD), but not as readily available as the 225/50

17's are plentiful in 225 and 255 section widths. Typical sizes are 225/45 front and 255/40 rear. Or 235/40 front and 255/40 rear, 275/40 rear. Or 245/45 front and 275/40 rear. As you can see, the choices for 17's are much broader.

Kevin it right on. IMHO the perfect wheel tire setup for a 911 narrow body is 225/45/16 on 8" 951 offsets front and 245/45/16 on 9" turbo rims rear. (of course this is what I run, so I'm biased:D )

89911 : I'd love to see the 8s at the front. Pics please - PICS !!!

Here's a thread that shows 951 8's on the front of 911s:

http://forums.pelicanparts.com/showthread.php?s=&threadid=155200&highlight=951+fr ont+wheels

-Scott

You didn't say Fuchs so :)

http://i19.photobucket.com/albums/b1...MG_0748_ps.jpg

http://i19.photobucket.com/albums/b1...MG_0745_ps.jpg

Just to add to Kevin's and 89911's comments

Unless you regear the transmission you will want to stay close to the factory design height for the tires which is ~25" &#177

Doesn't matter whether the wheels are 16, 17 or 18", when the tire height or more specifically the loaded rolling radius(which is generally not published) is increased, bag things happen to the overall gearing and percieved performance of the car.

There are good reasons to go to taller tires for a specific track, but not for overall general use.