Do I have to roll arches for 225s nb8b?

[mazmad]

With 'sport' suspension, track only car (apart from drive to workshop and sometimes track).

And yes....before you eager beavers hits the 'geez buddy have you heard of google search' button.... I have. and all discussions are either for 45s or larger wheels.

I am running 50/15s on 8in rims (6uls so think +36 offset)

[Lokiel]

No, unless you're really low.

MINX and I run 225s on our SEs for track days with no issues (both also have BC Racing coilovers and 6ULS).

[project.r.racing]

true, but the difference between 584 and 606 rolling diameter might just bring the tyre shoulder close enough to the chassis and arches. Nothing some height adjustable suspension cannot fix. Doubtful to have issues with stock height. But that doesn't take into account body roll or driving styles.

225/50R15s is much too big for a MX5.

[Lokiel]

^
Good point, forgot to mention in my post that I was referring to 225/45/15s (Toyo R1Rs or Hankook RS3s).

225/50/15s rub - MINX found that out on his BFGs.

[mazmad]

Sorry. Post edit..... Looking at 225/45/15s don't want to give up any gearing.

Thanks for the input peeps.

[hks_kansei]

225/45/15 compared to a 195/50/15 gives ~1.3% taller gearing (the 225 being taller)

225/50/15 compared to a 195/50/15 gives ~5.2% taller gearing

[mazmad]

Nah I have them slightly smaller diameter.

[hks_kansei]

Nah I have them slightly smaller diameter.

????

a 225/45/15 will always be roughly the same diameter when brand new, it's maths. (depends on how accurate the tyre manufacturer is when labeling)

A= 225 = width in mm
B = 45 = Aspect as a % of width (sidewall)
C = 15 = Wheel diameter in inches


Rolling diameter is:
(c*25.4)+(((A*(B/100))*2)

[mazmad]

I am looking at going from 205/50/15 to 225/45/15 results in marginally smaller diameter, which gives me marginally lower gearing (which is preferred).

[project.r.racing]

marginally a pooftenth difference. 2mm diameter change. which doesns't mean much when tyre lose 10-14mm if diameter in their life.

if you have the tyre and wheel combo you say you do currently, then just use one of the 100s of online wheel and tyre calculators and compare the differences. then just get a tape measure out and see how much difference to the chassis and arches they make.

[mazmad]

Done that with the 100s of online calcers, which as you say shows a poofteenth reduction in diameter.

But it's hard to estimate the difference due to increased tyre width. Not that I would often have the car near full lock (not a daily driver) but that is where the clearance becomes critical.

I am operating on the basis I will need to so getting the arches rolled next week probably.

[rascal]

But it's hard to estimate the difference due to increased tyre width. Not that I would often have the car near full lock (not a daily driver) but that is where the clearance becomes critical.

Also depends on what tyres you put on them. Not all 225s are created equal. (
One forum member posted some pics and measurements a while ago comparing Toyo 205/50/15 to Kumho 225/45/15 and the difference in width was only 4 mm. (not the 20 you would expect from the nominal measurements)

[Lokiel]

Federals seem to be wider too - kind of makes the WIDTH_IN_MM/SIDEWALL_PERCENTAGE/DIAMETER_IN_INCHES "standard" pretty meaningless.

[rascal]

Yeah, seems manufacturers can do what they want with regards to stated and actual sizings.

I changed from 235/55 to 255/45 on my tow car and the new tyres are 9mm narrower!!!!

[mazmad]

But it's hard to estimate the difference due to increased tyre width. Not that I would often have the car near full lock (not a daily driver) but that is where the clearance becomes critical.

Also depends on what tyres you put on them. Not all 225s are created equal. (
One forum member posted some pics and measurements a while ago comparing Toyo 205/50/15 to Kumho 225/45/15 and the difference in width was only 4 mm. (not the 20 you would expect from the nominal measurements)

Ouch!