Hey there, I was thinking that while I always like the factory look of stock rims, they are almost always improved upon by aftermarket 3 piece with custom offsets, etc. Why doesn't Ferrari, Porsche, and other manufacturers design as much wheel and tire under their bodies as possible? It seems they are getting better at this now on new models. I'm not referring to race bred F40's and Enzo's. But take the cars of the 80's and 90's, Don't they want as much grip and stability as possible? You can always cram a bigger custom set underneath. What do you think is the reasoning of this? Why wouldn't they do this from the start? What are they gaining? Thanks for any thoughts. Robb Williamson Centennial, Colorado
well think about profit!! the bigger the tire the more expensive... they'd probably deliver the enzos on those factory bicycle wheels, if they could ..lol it's also about handling balance i think....only drag racers need those real wide rears....
A wider tyre is not a guarantee of greater grip. Do you wonder why a F1 car runs 13" wheels, or why a 360 Modena has a 215 section tyre on the front? All you are doing is spreading the same weight over a larger area. The optimum grip level depends on the elasticity of the tyre as it deforms into the irregularity of the road surface. That's reason why you get more grip on a bitumin road compared to a smooth concrete one. Ferrari and Porsche have a very active tyre testing program with 4 of the major manuafcturers which is why they have bespoke tyres for all the models. (Excluding competition compounds of course.) After market wide rims are usually fitted by drug dealers, rap artists and generally people with dubious taste. TRX fitments excluded. Regards, Carl.
I like that! "drug dealers, rap artists, ... dubious taste" that's classic. I agree though, there is little performance advantage to it, in most cases I've seen....vanity only....
Manufacturers have to make a lot of compromises to produce a car. That's why. In Japan, no part of a tire can be visible in plan (top) view. So the fenders have to be big enough to keep the tire covered. Manufacturers worry about what happens when you're at full jounce with the control arm bushings gone still screaming around a corner with the steering at full lock loaded to GVW. When you put those bigger wheels on, maybe you even have to roll the fender lip. No problem to you, but an additional manufacturing process for the manufacturer. Some do it, some don't--either for cost, production speed or other reasons. When you put those big wheels on and load up your big brother in law and have his collection of books in the boot, you might suddenly discover that those tires rub. It's not a big deal to you, but you can't design cars like that! So much of it is all about tolerances and wear...
Also, remember the technology advances.....tyres are one of the most rapidly evolving sciences.... I'd rather do a long distance drive in a std tyred Ferrari over a drug dealer homey dropped and chopped car anyday. If only for the reduced road noise of the std tyre, never mind the ride quality.... Go to the track, and it's a different story.....
Carl, Thanks for the technical information. I found it very informative. You always see the "perfect (wider) offsets" mentioned by the manufacturers of new rims, and in other threads by people trying to help others with finding the perfect sizes to get the most out of the car on the track and street performance. (Big run-on) Just to clarify, I'm referring to the "non-drug dealing" brands, speedline, hamann, HRE, RUF, etc. I am not referring to the dodge neon's with rubber sticking outside the fenders by 6 to 8". I can understand the dubious tastes part as well. Very few styles look good and not tacky on classic F-cars and 911's. What are TRX? Thanks All who replied! - Makes more sense now. Robb Williamson Centennial, Colorado
Hi Rob, There is no reason to change the size, unless you a chasing a particular compound not available in the stock size. If you compare lap times on something like a 308 GTB with the stock 205/55-16 and 225/50-16 and then on the popular upsize fitment, the 225/50-15 front and 245/45-16 rear using an indentical compound, the car will be no faster. In fact, the car will understeer less on the smaller 205 section front tyre. Of course, a decent 4 wheel alignment is also what you need to get the most from the tyres. The TRX refers to a type of tyre developed 25 years ago by Michelin. It stands for "Tension Repartie X" and it basically was a tyre developed to fit a rim with a short flange to allow the sidewall to absorb more of the load over a convetional tyre (That is prevented from evenly absorbing the load because of the high rim flange). Of course you need to have a special rim for this tyre, so Michelin made all the fitments metric, so you had rim sizes of 390 and 415mm to prevent the tyres being fitted to conventional imperial size rims. Ferrari's were fitted as standard with the TRX fitment tyres from the 1981 model year to 1986. (Along with Jaguar, BMW and Peugeot to name a few). TRX tyres are expensive and difficult to source now. BTW, I see you have a 911, you must have a 911 set up with a downward rake of 3/4 to 1 degree. Your car appears flat. I gues you had it lowered by one of those chop shops that really had no idea what they were doing Regards, Carl.
