What size tyres?

[Sailor]

Just picked up a set of 8X16 RX7 alloys for my NC.
Now I need to decide what size tyre to fit for track days.
Should I keep close to standard rolling diameter or would I do better to change?
Original tyres are 205/45/17 with a 1936mm RD
225/45/16 will give 1913mm RD which is pretty close
245/45/16 1969mm RD
225/50/16 1982mm RD
245/50/16 2046mm RD

Thinking that 245 might be overkill and extra drag might not be worth the extra grip.

Thoughts appreciated before I commit

Cheers all,
Rob

[tbro]

NC's came with 205/50/16 tyres with poverty pack, Japan spec.

Hope that helps


Terry

[rascal]

Just picked up a set of 8X16 RX7 alloys for my NC.
Now I need to decide what size tyre to fit for track days.
Should I keep close to standard rolling diameter or would I do better to change?
Original tyres are 205/45/17 with a 1936mm RD
225/45/16 will give 1913mm RD which is pretty close
245/45/16 1969mm RD
225/50/16 1982mm RD
245/50/16 2046mm RD

Thinking that 245 might be overkill and extra drag might not be worth the extra grip.

Thoughts appreciated before I commit

Cheers all,
Rob

I would go for the 225/45 out of the above list for track days.
Too many people get sucked into the 'big is better' theory when, with low powered cars like the MX5, having too much tyre can make you slower..

[SPy vs. SPy]

It's also partly dictated by what you can get

Kumho

Toyo

Dunlop

Per what rascal said, unless you're heading to Bathurst you won't use 6th or maybe 5th depending on the track, so a slightly smaller tyre will help acceleration without impacting top speed.

also the 225/45/16 would be the best choice for a 16*8

[bruce]

First question is size. Second question is price (as you may not get your ideal size at the right price).

[Hellmun]

8 inch = 202.3mm . So it's actaully the perfect size for a 205 wide tyre. I'm currently experimenting with 225 wide tyres and I noticed I got more life out of them. I had 12 trackdays out of a set of D01J's in 225/50/15 and they would've lasted over 14 days if I'd rotated them earlier. I've got a brand new set of Kumho V70A 225/45/15 to try next and we'll see if it's the same.

[Sailor]

Thanks for the replies.
I'm swayed toward the 225/45/16 in the Toyo R888 and this set will probably get used only at Wakefield so my guess is that the gearing should work out OK.
I'll talk to Charlie B and Heasmans about an alignment so I don't lose outside edges prematurely.
Guess a couple of heavier bars might be a good move as well eh.

[Charlie Brown]

Thanks for the replies.
I'm swayed toward the 225/45/16 in the Toyo R888 and this set will probably get used only at Wakefield so my guess is that the gearing should work out OK.
I'll talk to Charlie B and Heasmans about an alignment so I don't lose outside edges prematurely.
Guess a couple of heavier bars might be a good move as well eh.

Well look at this, I go away for a few days and she who is to be obeyed is letting the Black Beast onto the track. One down one to go. (Little in joke here ).

Rob, go with either the 205x45 or the 225x45. I'm running the 225x50 and to get a little more drive out of the corners I think the smaller diameter would be a great help. I'll probably go for the 225x45 next time, only 'cause I want to show Hellmun the rear of the NC.

[Sailor]

Yeah, I've had a win....but she always knew it was coming.

Will go for the 225/45 R888 and see how it goes.
I am after all just a learner again.

Better lubricants and fluids look like a must as are front/rear bars, then we'll see how those soft Bilstein rears behave.
Better join too eh.

I'll be giving Rob a stir up in August over dinner...see if I can light the fire

[16bit]

8 inch = 202.3mm . So it's actaully the perfect size for a 205 wide tyre. I'm currently experimenting with 225 wide tyres and I noticed I got more life out of them. I had 12 trackdays out of a set of D01J's in 225/50/15 and they would've lasted over 14 days if I'd rotated them earlier. I've got a brand new set of Kumho V70A 225/45/15 to try next and we'll see if it's the same.

hey mate how did the kumho's go compared to the dunlops?

[Hellmun]

Well with the Kumho's and a new alignment (I had positive camber before I took it in for a new alignment due to some suspension play ) I pulled 1.5s off my PB at Oran Park and 1.8s off my PB at Eastern creek. The small aspect ratio means I'm getting a lot more push out of the corners and the Kumhos work from nearly cold. Plus with actual negative camber I found I got slightly better turn-in . The Kumho's definitely have a little more grip than the D01J's as I can push in more throttle on sweeping corners. I'm pretty concerned with the wear so far though... 2 track days and the shoulder tread is almost gone but they're still a little way off the indicators. I think I might only get 6-7 trackdays out of these but time will tell, you get surprisingly little tread to begin with so they may yet surprise me. Next club day at wakefield will be the real test, I'm still learning EC/OPGP but wakefield has felt much more on the limit for a while. If I can beat 1:10:59 there by over a second like everywhere else I'll be surprised

[PAU61L]

Hello, I didn't know you had negotiated track day driving privileges. Have you got the tyres yet, has Phil told you about garys motorsports and if he has any tyres. Is swmbo driving as well or watching. All the best with your swaying of the other MX5er.
Regards Paul

[moo moo nel]

Hellmun, what size of rims are you using?

[Hellmun]

15*8 6UL's.