Ideal wheel size?

[George]

Hello,

I am looking at

335/35/ZR17 Michelin Pilot Summer Tires and
275/40/ZR17 Michelin Pilot Summer Tires

2 questions I have is...

1: Would a 265 tire be better than the 275 for handling purposes on the GT40s or the 275 is just right with the 335 front (is there an ideal?)

2: If 335 and 275 is great, what is the ideal wheel size I should be looking at for the 335s and the 275s?

Thank you
G-

 

[flatchat(Chris)]

GT 40s had 15" dia. wheels with fairly tall wall tyres and probably of cross ply type --- if you wanted to be authentic.
If you're going the big dia. wheel low poofy profile, trendy bling factor tyre then you need to talk to the manufactures of these type tyres and see their recommendations for optimum wheel dimensions and then work around their offsets etc -- some examples from a race tyre manufacturere :- - MD Motorsport | Hoosier Tire Australia - good luck with that.

 

[David]

It all depends on the rest of the car. In theory a narrower tyre gives a slightly better turn in at the expense of a small amount of grip. It all depends on the setup though and if you plan on running power steering , it could get very hard work at slow speeds without it.

The tyres really depend on what you want from the car, how fast it'll be and how much power it'll have. Plus to a certain extent availability and cost, for me this is the biggest reason for going to 17's rather than 15, very little available for 15's in comparison. It might even be worth looking at the sizes you're considering and see if the ones one size up and down are cheaper (which would also suggest better availability). As an example people stick 225's on our car instead of the 215's it should have as they are £50 (25%) cheaper each!

As for rim widths there are recommendations for widths, personally I'd aim for the width in the middle, allows you to go a size or two smaller *or* larger if you want.

 

[George]

So it is not as simple as 1+1=2 :wacko:

It will be for a GT40. 500hp, and 850kg max weight, probbably 750-800kg.

Just trying to achieve best handling which will give it a faster circuit time than the other set-up.

Is the general rule of thumb to match the wheel width to the tread width?

335s run a 12.5" tread, so a 12.5" wheel would suit that best? If I ever run slicks on it, the hoosier 335/35/ZR17s have a 12.9" tread.

Cant figure out the tread width on the 275 Michelins though and the manufacturer in Australia said 'we dont carry them in stock' (the 335s) and cant tell me anything on wheel sizes. Why a manufacturer couldnt tell you a principle that applies to all tires/wheels without having it is beyond me. Plain stupid.

Thanks though.

 

[Ian Anderson]

George

You will also have to work within the confines of whichever GT40 chassis you use.

You will find with wider Tyres on the front you get rubbing on the chassis, bodywork and in some instances even suspension parts.

Likewise on the rear depending on offsets, etc you could have problems clearing radius arms.

But yes the 17 inch rubber has a better selection than the15 inch stuff.

But 15 inch is period correct. So it's your call

Ian

 

[Bob Putnam]

Go to tirerack.com, select by tire size, and look at the specification tab... Tread width and recommended wheel widths are listed.

 

[Mick Ridley]

George,

A couple of things to consider are....

A 17" rim will allow you to fit a larger diameter disc than you can fit with a 15" rim

There are many variable factors, but just by fitting a wider tyre,doesnt
necessarily mean you will get more grip, and have faster lap times

Amontons' Laws of Friction Guillaume Amontons - Wikipedia, the free encyclopedia

1. The force of friction is directly proportional to the applied load. (Amontons 1st Law)
2. The force of friction is independent of the apparent area of contact. (Amontons 2nd Law)

Why are wider tyres used..... again there are many variable factors, but a tyre has a optimum working temperature, if the tyre is too narrow, it will soon get above the optimum working temperature, over heat and loose grip, so you need to choose a tyre width, that doesnt allow the tyre to over heat.

It never is a simple as 1+1=2

When you have decided on 15" or 17". The best way to choose your tyre width is to see what other people are useing on thier cars. If you do a search on tyre widths etc, there is lots of information available on this site

It is a very complex subject...and Im just trying to explain it in simple terms

 

[George]

Thanks for the effort. Tire Rack recomended rim width on the 335s is 11-13", measuring rim was 12" with a 13.4" overall width and 12.5" tread. Thing is though, as I continued reading stuff on there, the Michelins have the tread around the side of the wheel like a shoulder, thus tread width depends where they measured from and could be anything.

If I went with a 13" like the Viper or a 12", what would mainly change? Would there be more contact patch of the tyre if the wheel was wider? Tire rack did not seem to mention anything about that except overall width is larger. If contact patch remains the same, I would assume the narrower option would be better as it would save some weight and lose no grip as the contact patch wont change.

I will research a bit on here to. If you know any link that is really good in the meantime on here, hook me up.

Thanks again
G-

 

[EGLITOM]

George
THe 275 will not fit on a standard GT40 bodywork. THey will rub at turn in at the rocker panels. Also the front fender will have a hard time to cover it properly. It may make sense to go this wide. But you have to check and change a lot of things to make it fit.

BTW how realistic is your GT40 project? Have you already purchased a chassis( and or kit) ? If not decide on this first and than check what wheeloptions your project allows later.

Thanks
TOM

 

[Dimi Terleckyj]

George
BTW how realistic is your GT40 project? Have you already purchased a chassis( and or kit) ? If not decide on this first and than check what wheeloptions your project allows later.

Thanks
TOM

Hi Tom

If you check on George's previous threads and posts the above question will answer itself.

 

[George]

Thanks Tom.

I am in contact with a GT40 builder and they can modify the car from standard to fit the idea. This is why I wanted to work out the little parts first, so that the builder can look at it and know whether he can make it work or not, if not, I will go smaller, if Yes, at least he will know howmuch change would need to be made given I know what I want to run. This is why im working in reverse order at the moment.

As far as having a chasis... nothing at the moment. I am trying to get a blueprint of what I am trying to build first, then produce the information to the car builder and see what of that can or can not be done with modifcations. This way we see if the car can be built around the idea rather than have the car and then realise this and that wont work without changing what was already built. Hope that makes sense.

Tom, are you having any issues with your 335's and 275's?

Tire Rack got back to me and said the ideal wheel widths for those 2 sizes would be 17x12 rear and 17x10 front.