Changing wheel diameter raises the roll center of the particular axle.
The roll center of an SLA suspension can be found by drawing a line from the center of the contact patch of the left tire to the instantaneous center for the left wheel (A) and a line from the center of the contact patch of the right tire to the instantaneous center for the right wheel (B). The roll center is located where these two lines cross. If the suspension is symmetrical the roll center will be located along the center line of the vehicle. If the suspension is not symmetrical the roll center location can be located to the left or right of center (depending on the geometry).
The location of the instantaneous center can tell what the wheel does as it moves through it suspension travel. It can tell whether it will gain negative camber (lean in) and if so how quickly. If the instantaneous center is to the inside of the wheel (suspension side) then the wheel will gain negative camber as the suspension compresses (e.g. outside wheel when the body rolls during a corner, both wheels under braking). If the instantaneous center is outside the car (away from the suspension) the tire will have a tendency to tip out as the suspension is compressed (this is not good). The camber changes more slowly with a longer “virtual swing arm” and can change drastically with a shorter one. If the instantaneous center is far above or below ground (e.g. a lifted 4WD truck with independent front suspension) the track width of the vehicle can increase substantially when the suspension encounters a bump.
Having a suspension that gains negative camber as the body of the car rolls is beneficial. It helps keep the tire perpendicular to the ground during cornering which maximizes tire contact with the track.
The illustrations below show how the location of the instantaneous center can vary significantly with suspension geometry. The top illustration shows the upper control arm slopping in, toward the center of the car. This places the instantaneous center on the suspension side of the wheel. The bottom illustration shows the upper control arm slopping out toward the tire. This places the instantaneous center on the outside of the wheel. Many older muscle cars have this geometry (pre-1970 Camaros, pre-1973 Chevelles, pre-1975 Novas) and it is not preferred.
275/40/18's on the rear of my '88 Frankenlotus. The wheel well is maxed out for sure at this dimension. 35 series tire would probably be better but could not find a front/rear matching combination with a 35 series rear tire.
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And here are some of the usual suspect videos from flutube:
Well worth watching, but maybe not try at home.
If they don't show correctly, just click on flutube headline, and watch.
Anyway, here are my Futura's rebuilt with 1/4" wider outer rear lips, to 10,75" and with 315/30-18. They fit eeeeexactly under the 1990 wheel arch on the milimeter. All outer lips are now Radinox. They are still much lighter than the AWI Monobloc 8,5"*18" with 285/35-18, despite being 10,75"*18" with 315/30-18"
It's original Sport300 seats and subframes off a Sport300, and then reclad in magnolia leather to suit my interror.
These seats are nla but copies can be ordered from say SJ Sportscars in the UK. Either trimmed or bare glassfiber. The subframes from SJ is a bit different and may need a bit of modification from what I heard. No personal experience. But, it's possible. I should ad that SJ also offers to cover the back with a layer of carbon fiber if one so cares.
Sport300 Wheel Arches are meant to be installed later on. Now I am busy modifying my Laverda SFC1000.
But I am working heavily to finish the carbon tailgate for the Esprit, so later on I'll look into the Sport300 wheel arches.
29-31 kilo. Probably nearer 29 as I need to strenghen a few areas. But stil a substantial saving. Then on to the bonnet, then doors etc. But that's far away right now.
I think I've probably said it before, but those Sport300 seats are the boggest single change to the car by a mile! They grab you, you sit lower, and still comfortable and you stay firmly planted in hard cornering. It transforms the driving experience. Really!
I have AWI V8 wheels on my 93SE but as everyone knows replacing 235 40 17 rubber is not easy. I didn't really consider these tires until a friend suggested I check them out. "Firestone Firehawk Indi 500", price wise they are considerably cheaper than other performance tire options. I can't provide an update on the drive yet as it's early spring here and the temperatures are still cool but from an esthetics point of view they look very good and the 225 45 17 visually look good on the rim even with them being a slightly narrower tire. I can report for sure I experience LESS tire rub when parking my car so that's a plus. FYI I have 285 35 18 on the rear and they fit perfectly and I much prefer the wider look than the stock 93 wheel/tire....Yes my car needs a wash and I really want to get at my rims, trying to decide what product to use
I was fortunate enough to obtain the Euro Spec OZ rims for the S4s back like 15 years ago.... thanks to Ralph at RS Motorsports. They barely clear my front calipers....and I get no rubbing in the wheel well.
The extra width is great and it sits inside the wheel arch with minimal overhang. Here is the tire specs taken from the LEW website.
Wheels:OZ Racing light alloy, 8.5J x 17 front, 10Jx18 rear
Tyres: Michelin Pilot MXX3, 235/40 ZR17 front, 285/35 ZR18 rear
I currently run the Pilot Sports and have been very happy with them. I will probably replace the tires next season, so I may go with the PS2’s. I’ll try to upload a pic or two when I get a chance.