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Hi all

I am looking for the best 15" rim size for a NA that is only for track work.

Whilst i would love to go big and bad, I need to keep costs down. My research points to a 15 x7 rim as having the best range of semi slicks. What would the PCB be?

Just wondering if i am on the right track and what tyre size would be best as a standard fit

Thanks.

15x8, ET25, 4x100

Run 205/50R15

Yeah I'd say 15x8, and run between 205s and 225s depending on power, flares etc. I run 15x8 +32s, fit on my NB without any modification with 205/50/15 semislicks fitted. Could go 215 or 225 tyres but not a lot to gain on stock power.

Thanks, I thought 8 " might be more difficult a range, but i will chase some quotes, thanks.

I will definitely look at the 205 seeing as i wont need to roll guards.

Recommended rim width by every R-spec manufacturer is 15x6.5 for 205/50R15, with an approved rim width range of 5.5 to 7.5. But, hey, what would they know?

Agree on 15x8 with 205/50s as being the 'sweet spot' for BFYB. Offset from +40 to around +25 should fit without modification. You might need a roll at the lower offsets.

But if you can get 15x7s for cheap they'd be worth looking at as well. That will get you within manufacturer recommended rim widths as manga_blue points out, if that's important to you. They will however be slightly slower than 8s.

[quote="Could go 215 or 225 tyres but not a lot to gain on stock power.[/quote]

how did you conclude that? ignore power for a minute, if you can carry more speed through (and out from) a corner you'll be faster

Ned Loh wrote:

Trackphotos wrote:Could go 215 or 225 tyres but not a lot to gain on stock power.

how did you conclude that? ignore power for a minute, if you can carry more speed through (and out from) a corner you'll be faster

You cant ignore power as that also determines if you are faster or not. OP talking track work so lap times are the focus..

Yes, you could and would carry more speed through the corner from the wider tyres, but on a low power NA you'll probably lose all you gained and then some on the straights, (track dependent obviously)..

rascal wrote:

Ned Loh wrote:

Trackphotos wrote:Could go 215 or 225 tyres but not a lot to gain on stock power.

how did you conclude that? ignore power for a minute, if you can carry more speed through (and out from) a corner you'll be faster

You cant ignore power as that also determines if you are faster or not. OP talking track work so lap times are the focus..

Yes, you could and would carry more speed through the corner from the wider tyres, but on a low power NA you'll probably lose all you gained and then some on the straights, (track dependent obviously)..

I hear you. & yes track dependant for sure. You'd really only know after testing I guess. I'd still wager on the wider tyre!

What Rascal said. More mass to move, more resistance to changes in speed. The marginal increase in grip is probably not enough to outweigh the extra drag you're inducing by having more rubber. Hypothetically anyway, I've never run tyres that large. Just seems to be the consensus from most of the guys that track miatas over in the states, many of whom have done their own testing back to back to come to that conclusion.

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yes it is track only, standard 1.6 non turbo for Wakefield and other nsw courses. I just want to get off the daisies and into something better that gives a range and availability of tires to choose from. I think for pure practice and getting out there, the 205s sound better $$ wise and be a huge improvement on what i already have.

maybe Santa can grab some super lights once i improve and start worrying about 10ths of a second

The thread title said "best bang for your buck". It's a stockish NA6 fercrissake. Suggesting anything over 6.5 rims is opting for biggest bucks for your pop. 195/50s on lightweight 15x6 or 15x6.5 are going to be the fastest and by far the cheapest way to go for this stage of development.

All other things being equal, 195/50s on an 8 will be quicker than on a 6.5.

8s give you more flexibility with tyre choice, as you can run anything from 195/50 up, so you won't need to buy another set of wheels down the track when you want to go faster.

8s are also a lot easier to come by now than they used to be and cheaper too. If you buy second hand (which you should if you want BFYB!) the price difference between 6.5s or 7s and 8s is usually not much.

So yeah I still think 8s are the 'sweet spot' and best BFYB.

I would suggest getting in touch with some of the local MX5 track guys to see if they have a cheap used set of wheels and tyres to sell. I got 15x8s with used 225/45 NT01s from lightyear for significantly less than what a new set of tyres alone would cost, as he was moving up to 15x9s and 225/50 A050s. Prior to that I got some second hand 15x7s and R888s for cheap off another forum member.

NT01s are a good track tyre to buy used as they generally don't heat cycle out and give good grip right to the cords.

pepejesus wrote:All other things being equal, 195/50s on an 8 will be quicker than on a 6.5.

8s give you more flexibility with tyre choice, as you can run anything from 195/50 up, so you won't need to buy another set of wheels down the track when you want to go faster.

8s are also a lot easier to come by now than they used to be and cheaper too. If you buy second hand (which you should if you want BFYB!) the price difference between 6.5s or 7s and 8s is usually not much.

So yeah I still think 8s are the 'sweet spot' and best BFYB.

I would suggest getting in touch with some of the local MX5 track guys to see if they have a cheap used set of wheels and tyres to sell. I got 15x8s with used 225/45 NT01s from lightyear for significantly less than what a new set of tyres alone would cost, as he was moving up to 15x9s and 225/50 A050s. Prior to that I got some second hand 15x7s and R888s for cheap off another forum member.

NT01s are a good track tyre to buy used as they generally don't heat cycle out and give good grip right to the cords.

^This right here.
I bought 15x7 to start with and ended up buying another set of 15x9 for track work.
If I had bought 15x8 to start with I probably wouldn't have worried too much about another inch.
If you end up going turbo in the future, these will be sufficient.

Thanks everyone, definitely food for thought, i hope to be out at Wakefield to watch the mx5 cup challenge.

i am still a novice and need to get track time first. Probably a case of getting experience with the NA but wont ever turbo it.