OK, I'm in the middle of this thing right now. I have 205/55 & 245/45 on the 308 right now. They are old BS RE71's. I have also lowered the car via QA-1's. This set up was great when I initially lowered it (all the negative camber had great grip), but inside wear was tremendous. Once aligned, I had more understeer than I wanted. I've decided to go with 215/55 and 245/50. The rear tires in the previous set up were slightly smaller than the fronts. I wanted to even it out or even go slightly larger on the rears. This would provide the desired "rake". I went with Avon M500's from Tirerack. I have already received the rears and am awaiting the fronts today. Keep in mind that the calculated dimensions are only "theoretical". The calculated diameter of one tire could be 25.65 but the actual could be 25.25 (ie the rear Avon). Also, the same size tire from manufacturer to manufacturer can also vary. I've got actual dimensions of my stock 14" XWX's, RE71's, & Avon's if anyone is interested.
Umm, Guys, Just a reminder that I started this latest round (post #20 this thread) by asking if anyone had experience running the same sized front & rear. In particular: 225|50-16s both front & rear.
Verell, It's not the tires, it's more than likely the alignment that is causing problems, followed by the weight distribution of the car. In addition, you may be dumping too much load into the front under braking (too much droop) which futher escalates the problem of too much weight distribution on the front of the car on turn in. To sum up, it's NOT the tire sizes. All thing equal, you need to look at you corner weights, suspension settings (springs/shocks) and braking loads before you think about changing tires. Consider this, every mid engined car in the world comes with wider rear tires, including race cars and F1 cars. Putting on smaller rears (or keeping the same as the front) will fix the mistake, but will not solve the problem. Solve the problem first.
Sean, I recognise that I'm trying to compensate for the stock suspension. I'm running a completely stock suspension, so don't have spring height adjustment. Doesn't that mean that I don't have a way to adjust corner weights? Also, At this point I've pretty much blown my remaining maintenance budget on the 16" wheels & the tires I'm about to buy, so don't have $$ for suspension components. Also am trying to keep my suspension stock, at least for a while longer. As I see it, that leaves tire pressure & sizes as variables. Am I forgetting something.
Sorry Verell. As for every car coming with wider rears...mine didn't. It came stock with 205/70-14 on all four corners. I don't know about all the other models out there though. I think it is an alignment issue as well as a tire issue. It is a suspension "system" and everything has to work together. You might try a little more negative camber in the front (easy to do). If you buy/bought new 16" wheels, did you buy four 16x8's? I don't think the same size tires all around would be a bad thing, but not necessarily what I would do. From reading the posts here, the 225/50 will fit on the front. Be careful though, if you do end up putting different shocks/lowering it, you might run into rubbing issues. The right front (205/55) "grabbed" the fender lip making a right into a steep driveway. My car has been lowered though. Henry
Henry, I went to 245/50 16 on the rear and so for so good. I put 225/50 16 on the front with the same results as you. The right front grabbed the fender lip making a right into my steep driveway. I really like how I have the car lowered, and the corner weighting is perfect. So I may either go to a different width in front, or be forced to raise the car all the way around.
Dave, I'm glad you haven't had any problems with the 245/50's. I ended up with the 215's on the front because I was afraid the 225's would exacerbate the problem. I too am thinking about raising the whole car maybe about 3/8". It has bottomed out once or twice. I'll let you know how the 215's work. What brand/model tire did you go with? Dang, why can't all the cool 308's be out here on the west coast. Everyone here has either a 355 or 360.
I installed Pirelli P-Zero Nero's on my 86 328, and have no complaints about handling. I posted earlier about tire upsizing and decided to go with the stock tire size. I figured if Enzo and the people at Ferrari thought this was a good tire combination, who am I to argue with them.... My 2 cents. David Wikette
Charles is absolutely correct. Get the ACTUAL dimensions from your retailer (like Tire Rack) BEFORE you buy the tire you think you want.
I have a big spread sheet for tire diameters that i put together--i am traveling today but Verell --feel free to post if you like
I also thought about those. I think those are made by Bridgestone. Yeah, what do you think about them?
To be honest, I don't have enough seat time since putting them on to tell you what I think, as I have been real busy lately. I just recently got around to corner weighting the car, doing an alignment, and setting up the toe. The shop that did the setup had encouraging comments. They felt that the adjustable coil-overs I installed made for a much better handling car compared to the stock 308s they have experienced. As a side note, they also said that my sucky old two valve 77 308gtb was quicker than any of the injected QV cars they have had in the shop. Next week we are headed to the Crescent Classic Ferrari Tour with some of the nicest twisties in the U.S. so I will have a much better idea of how the tires perform after the event. If for some chance I don't make any more posts after the event, then the tires sucked!
As I posted earlier, my car came with/has 220|55VR390 on all 4 tires & significant understeer. Good suggestion, will try. Have to have a the wheels aligned anyway as Ferrari's alignment specs for the 16" wheels is quite a bit different from the specs for the 390mm wheels(see below). Note that the 16 front camber is quite a bit more negative than the 390 camber. What would you suggest as a starting camber? The Superformance 16" wheels are same as the original 16s: 7x16 front, 8x16 rear. I'm specificly asking about using symmetric f-r tires w/stock suspension, then fine-tuning w/camber & air pressure. Based on what I've heard so far, I think I'm going to go that way. At worst I'd end up deciding it was a bad idea, & buy a pair of wider rears. Would have a spare pair of fronts. Given the relativel;y short lifetime of high perf. tires, having a spare front pair wouldn't be a bad investment. Going to adj shocks it would totally change things. At that point I would have enough adjustment & spring options to tune for 245|50 rear tires. If necessary I would make new fibreglass wheel well liners to ensure clearance. However, I'm trying to keep my car stock so I can continue to enter it in concours with reasonable chances of being competetive. Image Unavailable, Please Login
I know you have the same all around, someone else posted that "all mid-engined cars come with wider rears". [/QUOTE] Good suggestion, will try. Have to have a the wheels aligned anyway as Ferrari's alignment specs for the 16" wheels is quite a bit different from the specs for the 390mm wheels(see below). Note that the 16 front camber is quite a bit more negative than the 390 camber. What would you suggest as a starting camber?[/QUOTE] I'm no expert, but I'd probably start around -2 degrees camber. This is all a trade off. The more neg camber you go with the more the insides of your tires will wear. This is fine if you drive aggressively and wear the outsides of your tires = thus even wear. If you do a lot of commuting or straight line then you will notice the inside wear. [/QUOTE]I'm specificly asking about using symmetric f-r tires w/stock suspension, then fine-tuning w/camber & air pressure. Based on what I've heard so far, I think I'm going to go that way. At worst I'd end up deciding it was a bad idea, & buy a pair of wider rears. Would have a spare pair of fronts. Given the relativel;y short lifetime of high perf. tires, having a spare front pair wouldn't be a bad investment.[/QUOTE] Right now it sounds like you are looking to buy four 16x7's (fronts). If I were you I'd buy four 16x8's. The 225/50's will fit better on the 8" rims. [/QUOTE]Going to adj shocks it would totally change things. At that point I would have enough adjustment & spring options to tune for 245|50 rear tires. If necessary I would make new fibreglass wheel well liners to ensure clearance. However, I'm trying to keep my car stock so I can continue to enter it in concours with reasonable chances of being competetive.[/QUOTE] That is so cool you can make that kind of stuff. Your right, if you do go with adjustable coilovers, everything is wide open. I believe that 245/50's would fit in the rear w/o any problems (no need for new liners, at least that's whet I'm hoping on). I will be installing 245/50's in a few weeks. Good luck Verell. Keep us posted.
Guess I wasn't clear. I've already received my new wheels. Bought the stock combination: 16x7 fronts/16x8 rears. Hadn't thought about getting offset adapters like Atlantaman made, or would have gone that route. Would have left me with a bit of maintenance budget to experiment with tire combinations. The wheels were en-route when I got to thinking about what wider rears & thinner fronts than the 390mm wheels would do to the already noticable understeer. Up until then I'd been planning on going with 225|50-16 front & 245|50-16 rears based on Atlantaman's advice. I think that combination works well with him because he's running about 75 more hp than I am, & has adjustable shocks & spring height. Thus can tune his suspension & has enough throttle to overcome any remaining understeer. That's how I got to the symmetric 225|50-16 f&r idea. BTW, Making something thin like fender liners out of fibreglass is pretty easy. You just need some kind of a smooth form to shape it on, coat the form with something the fibreglass resin won't stick to & lay 3 or 4 layers of glass cloth on, liberally brushing each layer with resin. Then trim the edges to the desired final shape. For a wheel liner, I'd probably use the original wheel liner & make a fibreglass mold of it's inside, then build up the mold where I wanted extra clearance.
V--I was running that size when my car was a 205hp stocker---it handles great having just a bit more rubber in back when you start throwing the car into a turn
yep--I bought the tires based on overall diameter--been running 245/50-16 since 86 did all my upgrades in last 5 yrs
Verell, What size rear bar are you running? I know you want to keep it stock, but if you could find a bit bigger rear "stock" bar, this might help to reduce the understeer. I have not tracked the 308 but have autox'd P cars for many cars and it seems to me that the majority of the understeer is the limited slip pushing the car straigt, lift off and the front tucks back in. 2 Degrees of front neg camber sounds like it would result in better front grip under power but significantly reduced streeet tire life. If the back is giving you decent tire life with occasional tracking, maybe the next step would be to have the front camber and toe set for track days, then back for everyday use. What do you guys with a lot of "bar" experience think?? chris
Chris, If I remember correctly, the QV GTSs had the largest sway bars of any of the 308s. Atlantaman, is your car a GTB or GTS? I'm wondering if the GTS's higher chassis flex is coming into play also?
V--GTSi --but I think you are analyzing this a bit too much-- I went on tire diameter to get 25.5" rears so my speedo would not be off
