I'm sold! I've been contemplating these 16 inchers from Superformance for a couple of months now; your testimonial has me ready to take the plunge. I can't wait to see how they do on my 308 GTBi. BTW, what tires are you running? Have you had time yet to try out different brands or styles?
hey Art, how do you find the rolling radius of a tire...short of having a spec sheet ? is that indicated on the tire ? brett
Howdy Brett, Tirerack.com has extensive information on every tire they sell. The site is an excellent source of information.
How do you find the rolling radius? Why you use the attached tire conversion calculator of course! Image Unavailable, Please Login
Brett, Dave's calculator is pretty cool but I have no experience with it. The easiest way I use is to look at specs. The rolling radius is often represented as revolutions per mile. You can use it directly or convert to rolling radius which, if I recall, does not exactly equal the tire radius. Now, does anyone know how many revolutions per mile a new TRX makes? Regards, Art S.
Art, Coker shows 245/55VR415's to have a 27.2" Dia. 5280 X 12/27.2 X pi = 741.4748 revs per mi. or 39379.96/27.2 X pi = 460.8467 revs per km. Bruce
Guys, The diameter/radius is not necessarily the same as the rolling radius. The rolling radius is less - when on the ground a tire is not round - think about the contact patch. Regards, Art S.
Hi Marc- From the horse's mouth, here's Michelin's classic tire catalog, which gives the dimensions of the stock TRX tire (along with their logic for creating it): http://www.michelin-passion.com/passion/front/templates/affich.jsp?codeRubrique=20050713084556&lang=EN I don't think you'll find an exact match in a modern tire, but getting within a percent or so should be more than close enough. Looking quickly on Tire Rack, there are 2 tire sizes that fall around the same size: 235/60R16 and 255/55R16. The latter size is only available from General, while the former is used widely and has a large assortment, although not many with higher speed ratings. The next nearest available size is 255/50R16, but is about 4% smaller, and would bring your expensive exhaust system about 1/2" closer to the pavement (assuming they aren't too wide). And the hard part: as I recall the Ferrari 308 wheels have different widths front to rear (7" in front, 8" in rear), neither of which are the same as the 400/412. This may be why the spacers (and possibly center boring?) are needed to make the 16" set fit. When I checked over a year ago, I couldn't find anyone willing to sell me a set of 4 16" repro wheels of equal width, and I couldn't find any definitive data that suggested I'd be better off with a more modern tire, so I went down the original-equipment path and purchased new TRX tires from Longstone Tyres in Yorkshire, UK. Since winter has hit the DC area, I only had several weeks of driving time on the new TRX tires before garaging my 400i. In that time I can tell you that they greatly improved the ride and handling. In fairness, they replaced 11-year old TRX GT tires that looked practically new but were well past their freshness date. Having said that, my experience is that they offer a nice balance between comfort, control and dry/wet traction performance. Since I will spend minimal time on a track, I was more concerned about fun driving on twisty roads and a compliant ride around town and on the highway, than all-out performance. Good luck whichever path you take! Bret
The 308qv and 328 non-abs wheels bolt on a 400 no problema with just a small spacer (and a bearing cap mod if you go with the 328 version). A 412 is even easier - any of the ABS wheels (328 ABS, Mondial 3.2, 348, 355) should bolt right on. A
thanks to all for the generous input...with 6 inches of snow outside I am not in a rush but come spring I think I'll go with the trx's, again...Marc thanks
thanks to all for the generous input...with 6 inches of snow outside I am not in a rush but come spring I think I'll go with the trx's, again thanks , Marc
Hi all- I noticed this morning that someone has listed 3 of the TRX tires on eBay. They're described as used with 95% tread remaining, but there's no mention of the date code. If you're in need of a spare this may do the trick: http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=220536465047&viewitem=&sspagename=ADME%3AB%3ASS%3AUS%3A1123 Bret
Dave I am running used tires on my Ferrari they have 10,000 miles on them and are over two years old, in fact every part in my Ferrari is used except the gas.
BAWAHAHAHAHA Thanks I needed that. Tough day today, my elbows are killing me today (but I have been feeling much better).
Wimps, I'm in the process of buying tires for my car that had at least 3 prior owners and were mounted on at least 2 cars - and they are still fresh enough to use! Regards, Art S.
.........and don't forget, this is very important, make sure they are underinflated by at least 10 pounds so they will last just a bit longer
I received my Dunlop Direzzas from Tire Rack last week, the day after I received my 16" wheels from Superformance. (You do, by the way, have to pay about $28 for customs charges when you order these from England - still cheaper than any source in the US by about $400 - as long as the dollar stays relatively strong against the GB pound.) Got the tires on the rims and the wheels on the car today. What an improvement! Should have done this years ago! I kept one of the original 390 mm wheels, with near-new TRX tire, as a spare. I hope never to use it, but I do think that the extra weight up front improves handling. Now I've got the 390 mm wheels up on eBay. (Hope it's okay to mention this here.) I can't really imagine who would want them, but someone else might need a spare, I guess - or maybe some lunatic who values absolute "originality" on his 1980-1982 "i" car will snatch up all four! If not, I see a nifty coffee table in my future. . .
