4 Superformance Wheels & Tyres versus 4 new TRX's

17" Compomotives are going to be lower profile and 'fill' the wheel arches even less than 16", and if you'd have them in perfect world, what are you fussing about?

 

The look is determined by the (profile) thickness of the tyre relative to the diameter of the rim. You choose the overall diameter to be more-or-less the same so they will actually fill the arches the same anyway. Otherwise the speedo calibration and gearing will be changed.

Longstone are selling TRXs so you would expect them to promote them, but even if they are marginally less harsh (which I doubt) do you really care on a 308?

I changed my 14" XWX rims to 16" Compomotives my years ago and I wouldn't go back, although I've kept the original wheels.

 

I had the suspension rebuilt and made slightly stiffer at the same time as I changed the wheels so I can't give an accurate difference for the wheels/tyres alone. But it is certainly firmer and more precise than it was, and when I took it for a service at Keys recently, Tom (who has a GT4 on XWXs of his own) was happy with how it drove, even though the bushes are all in need of replacement again. It's still way too soft for a track though.

Modern rubber is designed to work with modern suspension systems which are generally much more sophisticated than a 70s Ferrari. So I don't think Longstone's claim sounds unreasonable, it's just I am not sure it's that relevant in the context of these cars. YMMV.

IMV it depends on how long you will keep the car and how much you drive it. If not long/not much then I'd go for the TRXs, otherwise maybe the 16"es are a better bet. There is probably much more difference between the 14" XWX -> 16" and 390mm TRX -> 16" though.

 

If its the same as the mondial, you can fit the bigger brakes with the non oem wheels and tyres.

 

I'd love to know how a modern suspension system on an average car is more sophisticated than the double wishbone, coilover design of the 308.

While modern supercars now have active rear steer and such sophistications I suspect the average modern suspension system, for modern tires, is less sophisticated than the 308.

 

Andy, go the 16's. If you want a nicer stance, put 245/45 on the rear, and 225/50 on the front. That's what I was about to do, until I found a set of mint TS-17's (tee-hee-hee!)

 

My GT4 has had 16" Superformance wheels since long before I bought it - probably 15 years given the age of the tyres when I got it 3 years ago. So I can't comment on the differences. But it handles rally nicely and no adverse comments fdrom FOC instructors when I have had it on track.

Biggest improvement was ditching the 11 year old Goodyear Eagles and replacing with more modern Bridgestones. Even I could feel the difference.

I actually prefer the look of the 16" wheels. Looks much better balanced.

 

I own 15" diameter wheels for my E30 BMWs in addition to the factory 14" wheels. I own the 15" diameter wheels for the same reason that 308s go from TRX to 16": there is very small selection of 14" tires compared to 15" diameter. My 15" wheels are currently shod with RE-11s.

I DO feel a substantial difference between the 14" and 15" rims but I attribute this entirely to the differences in unsprung weight (weight of tire plus rim) NOT the profile of the tire sidewall. Generally speaking, rims weigh more than tires so smaller diameter rims with higher profile tires often weigh less and therefore feel better than bigger rims with low profile tires. I am surprised at how little the weight difference has to be to be noticeable.

I would expect the Superformance 16" rims to be heavier than TRX wheels because of the diameter difference and also because Superformance wheels are aluminum while the TRX wheels are lighter magnesium (as are 16" factory Cromadora rims). Wheel style and construction methods count for a lot though; well designed larger rims can be light.

 

I made the switch to the 16 SF rims and didn't notice any difference at all. Pirelli P 7 tyres and perfect handling.

Remember you MUST to fit the plastic hub spacer to the front rims otherwise you WILL get wheel wobble at 50 to 80 mph

 

I have a car with new TRX, one with SF 16" and one with OEM Cromodora 16". The TRX aren't bad at all, but the 16" with modern tyres are better, even the SF. The SF 16" weight is almost twice the OEM Cromodora 16", but they are better the same than the TRX.

Ciao

 

From Brian...
I DO feel a substantial difference between the 14" and 15" rims but I attribute this entirely to the differences in unsprung weight (weight of tire plus rim) NOT the profile of the tire sidewall. Generally speaking, rims weigh more than tires so smaller diameter rims with higher profile tires often weigh less and therefore feel better than bigger rims with low profile tires. I am surprised at how little the weight difference has to be to be noticeable.

It's not only the unsprung weight which matters but also where it is... A larger rim have more mass further out from wheel center. When the wheel rotate this added mass will increase the gyro-effect which makes it harder to get the wheel to change direction - e.g. harder to get the car to turn.
Then, movement of the sidewall during driving is a major contributor to tyre heat, which you need to get good grip.
With a lower profile you need more movement to get to the right temp., so a stiffer tyre may make the car feel more precise, but it doesn't necessarily mean you have a better grip...
This may though apply more to a track situation than to a every day around the block driving, but worth keeping in mind

Sent fra min HUAWEI CRR-L09 via Tapatalk

 

switching to the SF 16" there is an emprovement (and a big save of money the next tire change), while switching to the OEM 16" there is a BIG emprovement due to the lighter (than the SF rim, not than the TRX rim) rim combined with the modern tyres.

ciao

 

They'll fit fine, Andy, and look a lot better. A couple of the track guys here run SF 8" and 245/45 all round, for better turn in - looks the business and fills the front guards, but probably make it a bit heavy on the street.
Plenty of good tyres in 245 and 225: Toyo, Yokohama, Bridgestone, etc - cheaper and better grip, too.

 

One thing that may need some work moving to modern rubber are the alignment specs. The factory specs for the 308 are 40 years old and reflect the tire technology of the time. I've never been happy with them on modern rubber... too much understeer. One of my projects this driving season is to find a setup I like with modern rubber.

 

I put the superformance 16 inch rims on my '83 308QV 15 years ago, the second year I owned it. I first looked for the original 16 inch rims and got frustrated with hearing "they are sold" everytime I called an ad. Back then I went with 225 /50 on front and 245/45 on rear. When I replaced the tires a couple years ago and I went back to original sizes of 205/55 front and 225/50 rears. Car handles great, as new rubber is lightyears better than in 83 and tire tread footprints seam to have gotten wider. Car looks right and handles great. Ride is comfortable, but I also refurbed the entire suspension 15 years ago and it still is perfect.

 

Did you play with tire pressures. It will help. But, can't argue with a more modern set up.

 

I put the superformance 16 inch rims on my '83 308QV 15 years ago, the second year I owned it. I first looked for the original 16 inch rims and got frustrated with hearing "they are sold" everytime I called an ad. Back then I went with 225 /50 on front and 245/45 on rear. When I replaced the tires a couple years ago and I went back to original sizes of 205/55 front and 225/50 rears. Car handles great, as new rubber is lightyears better than in 83 and tire tread footprints seam to have gotten wider. Car looks right and handles great. Ride is comfortable, but I also refurbed the entire suspension 15 years ago and it still is perfect.

 

Yes. In my experience my 308 is super sensitive to tire pressures at the front. Surprisingly so.