Confused: Should I get wider tyres before any engine mods?

[mazmad]

For track use, to clarify.

Whilst I do plan to do engine mods, is it premature to fit wider tyres without boosting power? Will the increased grip be offset by having to push greater weight around and increased drag?

And yes....I have read the thread on 'How to ruin the handling of an MX5.by Norman H Gar'. Horses for courses comes to mind. So my horses are for track courses, not street.

Thanks!

[CheyneX5]

A good shock and spring set up, paired with some good tyres will go nicely. What tyres you use will depend on your wheel size and budget.

[Suspense]

How wide are we talking? Are you still running the stock NB8B rims (6.5" wide)?

I went wider when I got my 6ULs but nothing drastic. Technically anything greater than 7.5" (i.e. 1" greater than stock) isn't road legal. Keep in mind what tyres you'll be running too. I'm still running 205s, and I really questioned whether any performance gain from going to a wider rim would really be perceptible with a relatively stock engine. If the tyres are the same width, is a half inch in the rim really worth the extra cost or is it better spent elsewhere?

[Magpie]

As has been said on here before be aware of the unsprung weight of the rims/tyres that you are putting on.

For example for my NA the:
Standard 14" (rims/tyres) are 15.7 kgs each
15" x 7.0" rim with 195/55/15 tyres are 17.4 kgs each
15" x 6.5" Storm II (Advanti Racing) with 595RS-R 205/50/15 are 14.6 kgs each
15" x 7.0" 6UL's with R888's 205/50/15 are 14.7 kgs each (from memory)

[hks_kansei]

15" x 7.0" rim with 195/55/15 tyres are 17.4 kgs each

55 profile on a 195 is a bit high, the general profile for a 195 is only 50.

A 195/55 will be 10% greater rolling diameter than a 195/50, the 10% higher gearing would be more detrimental than the weight.

[Magpie]

55 profile on a 195 is a bit high, the general profile for a 195 is only 50.

Thanks I will check when I get back home, they could be 50 profile (my other half was telling me the numbers and I may not have heard correctly).

[mazmad]

Thanks all for your comments.

S'pense, I am going from the standard wheels - best I can work out these weigh 15.5lb - and am going to 6ul 15 x 8, at 12.7lb. So tyres will add weight for sure, wheels some saving to offset that.

Maybe weight gain overall will be minimal. So does the standard engine have enough power to push the biggers tyres around, for the increased gain in grip?

[Apu]

My logic is to go on the basis on the width of the tyre you want to run. No point getting a rim wider than necessary as it's just extra weight.

For example, I run a 205/50/15 and I use a 6.5" wide rim, for which a 205 is the widest recommended. On my Integra, I will be running 215/45/16 on a 7" wide rim. Again, same principle.

I'll stick with 205 for my MX5 until I substantially bump the power, but I reckon the 205 will still do the job. If not, I'll go to a wider wheel and a 225 profile tyre.

Think about what you want to spend on your wheels and work it out that way. My 15x6.5s weigh about 5.5 kg and cost about $700-800, and that was a substantial drop in weight from stock.

[Muzdaman]

From emilio at 949

If you are grip limited, more tire is faster. On a 90whp stock Miata at Willow Springs, 205's are about as much tire as you need but that's about the only instance where 205's are all that's needed for max speed. Up it to about 140whp and 225/45's are proven faster even on the fastest tracks. Up it to 200whp and 275's are faster. Talking about autocross, giant tires are faster almost no matter what the power is. ES Miatas with maybe 120whp run 225/50/14's on daisies. They would run bigger tires if they could fit them onto the rim. STS2 Miata autocrossers with 110whp will soon be running 9" wide 225/45 R1R's on class limited 7.5" wheels. CSP NA & NB Miatas run 275's, I think there is at least one very fast NC with 285/30/18's now, they ran 265's last year.

If your goal is max grip/speed, figure out how to shoehorn the biggest, stickiest rubber under the car. If you goal is a certain "feel" that comes with the very lightest wheels/tires, then get the very lightest wheels/tires. Don't mistake the two.

My daily driver is getting 15x8's with 205/50's, plenty grip for occasional 6/10ths street driving and 110whp. The two track cars get 15x9's with either 225's or 275's depending on how serious I am about going fast that day.

[sailaholic]

949 have also shown a wider rim (within limits) is faster then a narrower rim for the same tire.

For memory 8 inch on 205, 9 inch on 225. I have also seen additional published details saying the the widest rim recommended for a tyre will be the fastest combination (based on equivalent rim type)

Sent from my GT-I9100 using Tapatalk 2

[mazmad]

wow that's interesting. 8" seems big for 205's, stiffer is better everywhere right...?

[NitroDann]

205mm=8"

Or close enough.

Dann

[mazmad]

Where the stock nb8b is 6.5" and 205's. 8" is much straighter sidewalls.

[Suspense]

949 have also shown a wider rim (within limits) is faster then a narrower rim for the same tire.

What sort of difference are we talking though?

[NitroDann]

Significant, basically, if any width up to 10" cost the same amount, and you were running 225s (NT01s etc basically stock standard road course tyres for mx5s) you would always always get a 10.

Dann