what size tyre?

[Sailor]

Bear in mind that different aspect tyres suit different width rims for the same tyre width.
A 235/40 tyre will be happier on a wider rim than a 235/45.
Manufacturers don't spend millions on research and development without good reason!

http://toyotires.com/tire/pattern/proxe ... tion-tires

[Sailor]

If you read that link it refers to slicks and R Spec tyres, not road tyres.
Emilio talks about a 275 section slick on a 10" rim and tyre design, saying a 11" & 10.5" rim was no advantage. So it comes down to tyre design for certain rim widths.

I'm not sure if its referenced in that thread but he also reccomend a 225 rs3 on a 9" rim, which is a road tyre.

This again depends on the tyre aspect and in some cases wheel diameter.
The RS3 in a 225/40/18 is recommended for a 7.5 to 9.0 rim, the 225/45/17 is recommended for a 7.0 to 8.5..we are talking 17x9 so the tyre choice would be a 235/45/17 or the 245/40/17 both will require at a minimum some guard rolling to fit, but at least will give some semblance of a road quality ride compared to an overstretched tyre with no sidewall flex.

[plohl]

i think something that should be noted, is that the tyre companies are companies. Why would they invest resources into a tyre that only "worked" on one rim width? They have to produce a product that works, and works well, on a number of rim sizes and at different aspect ratio's, not to mention different cars which stress the tyres in different ways dependent on allignment, pressure and suspension geometry. I would be warey to assume that the middle of the fitment range is the "optimal" choice for a tyre.

[JBT]

Some info here about 3/4 of the way down the page: http://www.carbibles.com/tyre_bible_pg4.html

[Charlie Brown]

i think something that should be noted, is that the tyre companies are companies. Why would they invest resources into a tyre that only "worked" on one rim width? They have to produce a product that works, and works well, on a number of rim sizes and at different aspect ratio's, not to mention different cars which stress the tyres in different ways dependent on allignment, pressure and suspension geometry. I would be warey to assume that the middle of the fitment range is the "optimal" choice for a tyre.

You can't say fitting a tyre at either end of the rim width range is the "optimal" width.
It can't be "optimal" when a rim width half an inch outside the band is no good but one and a half inches the other way is fine.

Thinking logically. Imagine you're looking at a tyre in cross section. If you pull both beads out, the centre of the tyre will roll down. Push the beads together and the centre of the tyre rolls up.

Now mount it on a wider rim than recommended and the centre of the tread is lower than the outside. To make it work on the full tread width you must increase the pressure, but then you also start pushing the preferred design pressure envelope.

Stay with in the designed ranges and all will work well. Go outside and it's like a dog chasing it's tail. You'll never catch the "optimal" performance point.

[Sailor]

i think something that should be noted, is that the tyre companies are companies. Why would they invest resources into a tyre that only "worked" on one rim width? They have to produce a product that works, and works well, on a number of rim sizes and at different aspect ratio's, not to mention different cars which stress the tyres in different ways dependent on allignment, pressure and suspension geometry. I would be warey to assume that the middle of the fitment range is the "optimal" choice for a tyre.

I would be extremely wary of fitting a tyre outside of the manufacturers rim width recommendations because as you say the manufacturer has already considered the variations in vehicle type.

And besides the safety and ride issues, hugely stretched tyres just look f***ing ridiculous!

[Old Dude]

i think something that should be noted, is that the tyre companies are companies. Why would they invest resources into a tyre that only "worked" on one rim width? They have to produce a product that works, and works well, on a number of rim sizes and at different aspect ratio's, not to mention different cars which stress the tyres in different ways dependent on allignment, pressure and suspension geometry. I would be warey to assume that the middle of the fitment range is the "optimal" choice for a tyre.

I'll try and be diplomatic here, but before I start its not always easy for me. Tyre companies don't need to make a tyre to work on multiple rims as they make multiple tyre widths, to suit different width rims, and if someone is silly enough to buy a rim that is too wide for the car simple for looks how does it become the tyre companies problem to get a tyre to fit on an oversized rim?
Easy solution, sell the oversized rims, buy the correct size rim, and tyre to suit. Then you won't be compromiseing the tyre or the safety of the vehicle.

Hope I wasn't to brutal
cheers
Dale

[JBT]

...And besides the safety and ride issues, hugely stretched tyres just look f***ing ridiculous!

[Sailor]

Its funny the ammount of cheese and wine this thread has turned into. Its kind of like religion, disregard anything contrary to their beliefs.

The thread i posted has the guy who designed the 6ul, emilio stating that tyres are fastest with a little stretch and why they are faster when slightly stretched. Yet most people in here are arguing against it, i'm sure thev'e put in more tyre testing time than 949.

Fastest?
In what application?
AutoX guys are using 275 tyres on MX5...try that on a road circuit!

The thread started with a request for a tyre size for a 17x9 wheel for road use.
Fastest would require a slick...but only in the dry when a wet would be required.
Yes a little stretch is good where you are prepared to sacrifice a little ride comfort and compliance for a quicker response...that's why the manufacturer has a wide wheel width range
and there IS a maximum.
Overstretch is NOT "a little stretch", a little stretch is putting the tyre on the max recommended rim width.

On the road you require a tyre that is safe and compliant.
As I said before the manufacturers put a lot of effort into testing and designing tyres.

[NitroDann]

Im going to go ahead and be a prick.

Who cares.

Just get whatevers cheapest, OP obviously doesnt care.

And of course situation affects performance, so why are we arguing semantics.

/thread

Dann

[Steampunk]

Just get whatevers cheapest, OP obviously doesnt care.

He does care Dann, but like most of us, can't afford bigger tyres, so he's looking at the best compromise in size and price.

For my 2c l'll give a slightly askew example: (taking aside offset and fitment inside wheel arch)
I used to have 15x6" wheels with 205/50 Kumho KU36. Lots of people said it would not sit right, have too much bulge blah blah, but they looked fine stationary, and here's what they look like under load:



Notice the difference in tyre deflection F&R, especially the top and bottom of the rear.
The car is headed left, but because it was drifting (it's on a medium-grip skidpan), steering is to the right.
Now, I know the OP wants good road tyres, but under "enthusiastic" cornering, or emergency manoeuvre I equated lateral load on a high grip surface, ie. normal suburban roads, to be very similar to the load I put on the medium grip surface.

So just to reiterate, I had 6" wide wheels with 205 section tyres, and if I had wheels that are, for simplicity's sake, 3-steps wider, I would want tyres that are also 3-steps wider.
Buying a size tyre for the sake of fitment inside the wheel arch, instead of proper fitment to the wheel itself, is backward thinking.

[deanb90]

first off, I do care, otherwise I wouldn't be on this forum asking questions.

it's not about money either, it's about finding a good medium. I am not going to buy a cheap tyre, never have never will. 225 seems to be fine to fit on a 9" wheel according to bob Jane and about 4 other places so I think the debate wether a 225 is to small is over. the reason why I am going with the minimum required size tyre is because of the specs of the wheels. the car will still handle exceptionally well.

thank you
dean

[Sailor]

Dean, What tyre and what aspect ratio?

[JBT]

FWIW, these are 225/45 on 7.5" wheels front and 245/40 on 8.5" wheels rear as recommended by BMW.