Track guys - Tyre size query

[old'n'slow]

I have a set of 16” x 8” rims that I want to fit some track (DOT) tyres to for Club days. I have no clearance problems.

Do I fit:
• 205 x 45s or
• 225 x 50s

The 205s have a rolling distance that is 7% smaller, therefore would allow quicker acceleration than the 225s however the 225s obviously have a larger contact area with the road and would hang on (and look) better.

These are the only two sizes available to me from my source. Any constructive ideas appreciated.

[Mr_Q]

... the 225s obviously have a larger contact area with the road and would hang on (and look) better.

They'll give a wider contact patch, not necessarily a larger one.

Are they both the same type of tyre (i.e. same manufacturer, rubber, etc.)?

Which track do you mainly run at? Would the acceleration or better top speed be more worthwhile?

[old'n'slow]

... the 225s obviously have a larger contact area with the road and would hang on (and look) better.

They'll give a wider contact patch, not necessarily a larger one.

Are they both the same type of tyre (i.e. same manufacturer, rubber, etc.)?

Which track do you mainly run at? Would the acceleration or better top speed be more worthwhile?

Wakefield, so top speed not a priority.

205s are Kuhmo V700 and 225s are Bridgestone RE55, but it's more the trade off I'm concerned about. ie loosing acceleration of the 205s to (hopefully) gaining corner grip with the 225s.

In other words will carrying a higher exit speed offset the lower acceleration up the hill and onto the straights?

[bruce]

Oh god, who gives a crap! I think we are really splitting hairs here (tenths of a second).

Just fit the tyres, get out there and try to improve each time.

[Mr_Q]

My vote's for the 205s. Other than that - what Bruce said: just drive them hard and see how they go. Tyres are consumables anyway so try the 225s next time (if you think you need to).

[Boags]

Aren't 205s a tad on the small side for an 8\" wide rim?

It'll look dori dori, that's for sure.

Boags

[irwin83r]

Aren't 205s a tad on the small side for an 8" wide rim?

It'll look dori dori, that's for sure.

Boags

205's are a bit narrow for 8" but it has a fair amount of side wall to bend in.. not like the tempe specials

205 will have better turn in than the 225 maybe.. better acceleration due to total rolling Diameter but it wouldnt be bucket loads different

the 225s will look better and i'd say are more suited to a 8" wide rim.

id go the 225s but im in no position to be taken too seriously im a newb


if in doubt... which is cheaper

and which is made where?? see if one is a dodgy korean make..

the kumho's apparently warm up fairly fast and have some decent water grooves.. no idea on the bridgestones.. havent heard much about them

[kula]

i run 195s on an 8 inch wide rim and its fine,
that said, some tyres might not like it as much.

[Mr_Q]

205mm is 8 inches - so you'd think it'd be a good fit.

[Boags]

Fair enough! Thanks guys.

Boags

[Ted]

A 225/50 is a very tall tyre, esp for an MX5. That is about the size I would expect on a Saloon car, in fact I think that is their control tyre size. Its seriously got to be at least 30mm taller than a 205/45.

Unless its a fairly high power car, I don't know too many MX5s that can turn a 225/50 well. On the plus side, you could run a 4.4 diff and still have moonshot gearing.

[manga_blue]

I can't help thinking that 225/50x16 is a pretty large tyre. It's going to be pretty tall and it just looks it's big and heavy - OK for a full size sedan but not for a small car. I'd expect it to generate handling and ride that's big and heavy as well.

205/45x16 is the recommended size for that rim in a MX5.

[kula]

there are quite a few cars in japan runnin that size but 15.

including this:
http://www.hundred-one.com/demo1.htm

which is the fastest around tsukuba.

ＰＡＮＡＳＰＯＲＴＳ特注品Ｆ １５Ｘ８Ｊ　Ｒ １５Ｘ８.５Ｊ
Ａ０４８　Ｆ：２２５/５０-１５　Ｒ：２２５/５０-１５

[Benny]

A 225 will perform worse than a 205 on an MX-5.
The 225's are just over-tyring the car and have too much grip.
In R spec tyres, even 205's are a bit too much for a NA MX-5, but are OK with SP's and the like.

Go for the 205's.

[deez]

On a related note, thoughts on tire pressure on the track? For a 205/50/15