Quote:
maybe... but I'd recommend dropping to 185/60s on that rim.

I've used various wheel tyre combos including
- 205/60*13's on 6" and 7" wheels,
- 185/60*14 on 6" wheels, and
- 195/60*14's on 6 and 7" wheels.

a 185/60 works really nice on a 6" wheel. And 195s and above seem happier on 7s - to me anyway. Just in the way they respond to steering input and 'seat of the pants' feel.

I guess you have to find a happy compromise for each application. And that's probably the difference between race engineers and mugs like me. There seems to be about 10,000,000 ways to skin this cat.

funny thing is, I could have fitted these 14*7"s under the gaurds without the flares...but they were quite pumped beforehand anyway

Quote:Yes, all the luxury cars use double a-arm suspension. It's technically better, one main reason is that camber can be controlled throughout the compression and expansion of the suspension.

On the other hand, Porsche 911 still uses McPherson struts, with world-class roadholding and (in the newer ones) very good handling.

The new Corvette is using double a-arms with transverse leaf.

Harry,
Stability, yes better cornering.
I remember when I first got the SSS back on the road after its restoration, with its little 12X 5's and thought -if I don't do something about increasing the track here I'll stick it on its lid in no time!Put the 13x 6's and 175/60/13's and a totally different car.
The rest I'm going to dijest this over a beer tonight....
One question does come to mind immediately though and that is if your're comfortable with the level of grip that you've got (on radial r's) are you better to opt for a 6'' rim rather than go 7's?
Cheers
Dave

hmmm, that's interesting. Like I said its a bit of a black art to me, and I'm still very much a learner on geometry topics like scrub and roll centre and how to use them to your advantage. What i've said above pretty much exhausts my knowledge on the subject. The only other stuff I know is that more +ve scrub increases steering effort,and places more load on the smaller outer wheel bearing.

Maybe conventional (cross ply) tyres, which I assume the old Shellsport cars ran, react differently to this factor than radials?

I'm sure Feral, Tsillay, Stirlingmac and some others here would know more about it.
told ya - Tsillay already confirmed it while i was typing this post (if that's what you call what i do to the keyboard)

What i expected before putting the wide offset wheels on was better cornering performance because of the increased track. When you mention stability, do you mean when cornering? Because I can confirm that straight line stability suffers, most notably under braking. The car ducks and dives around quite a bit on uneven ground, and if you happen to touch a ripple strip while braking you better have a good grip on the wheel!

Cornering stability did 'seem' to be increased, but I think that was more down to the increased +ve scrub introducing some understeer initially. Probably because it reduced the amount of lateral grip the front tyres were able to generate. Its only with hindsight that I was able to put that understeer down to the wheel tyre and +ve scrub. I got the balance back by fitting a smaller front sway bar and experimenting with toe/castor settings at the track.

When i fitted the larger diametre 195/60*14" wheel/tyre combo with significantly reduced offset, I had heaps of oversteer. And noticeably improved cornering speed too. I had to go back to the larger front bar and soften off the rear bar as much as I could. Running more fuel load helped too - when you are limited in suspension adjustability you have to get creative Obviously it was generating more front end grip for some reason, and I went looking for why...

Which reminds me, one other thing i forgot to mention about how you can change the scrub radius is with rolling diametre of the wheel/tyre combo... Increasing rolling diametre reduces +ve scrub radius (if that makes any sense )

just a bit of a tangent for you, if you were to head off road (rally etc) is it better to lower your car to eliminate body roll or leave it std height and upgrade the springs and swaybars to eliminate body roll?

and with strut front ends, i have also heard that they don't like a lot of positive scrub - not that i know what that is...!

i often wonder about whether macpherson struts are any good at all, it seems to be that the older "double wishbone" 'a' arm style front ends were a better design (not traverse leaf mind you - i'm talking about the coil spring versions) if a little heavier. they seem a lot easier to modify to increase/decrease camber and track. i've onyly ever heard good things about them and how many racers wish they'd have carried the design over to newer cars.

Two very different applications here though....
I suspect the tyre contruction and contact patch has a lot to do with it. If you look at a shellsport car on 13x10's, the diameter of the tyre is about 20 inches (or less than the original 12 inch!!)
The contact patch is therefore about 2 inches long, and 10 wide, and remember these are crossply slicks... You only ever run very conservative suspension angles to make these things work, so you dont end up working them very hard, the tyre doesnt tip over much with steering input......
Now looking at a car running on modern radials, the contact patch is probably something like 4 inches long, and 6 inches wide... You run huge camber and castor to make them work, which tips the tyre all over the show! Prap's adding scrub to this equation just stuffs things up too much....

I suspect that for any given setup, less scrub will always work better, if it's technically possible, which it isn't if you're stuck with Macpherson struts....

Harry,
Thanks for that, I must admit I've been chewing it over all weekend. The bit that I can't quite grasp is that in my experience the single biggest thing that you can do to enhance the 1200's handling is to put the widest offset wheels possible on them. Now obviously the distance from the inner edge of the rim to the strut is a limited ( even my 13x 6's with 175/60 R's are getting very close to the strut) so for a wheel of any width one has to go wider to the outside - for instance a shellsport race coupe that have monsterous offest 8'' wide (or bigger) wheels that you would think would be a big negative in terms of too much + srub? Yet they handle like they are on rails.
Maybe there's a tradeoff here between the extra stability provided by the wider footprint verses the negative's of too much +'ve srub?
Cheers
Dave

craig allen to me is abit like ray hall
to look at them and their surroundings you wouldn't think much of them
but if you look at what they have achieved
they are masters of their craft with very few piers if any!!
ray in a small town not a shoe in sight
craig in a big town with sh!t all around

you could try some 14x6 1/2's,for a while they seemed to be a popular choice on corona's.i've just put some 195/60x 14's on this size wheel,using falken azenzis,& they look good.they're the 5 spoked bathurst style,but they were called another name.i also know someone who has some 14x7's to suit a 1200,if you want to go that way.

Thanks Harry...I'll give 14x7's a gowith the 195/60 series