MX5 Winter Tyre Sizes

[ChapppeRS]

Hi guys,

Just a quick question. Would it be OK to run 165/65 R14 on the front and 175/65 R14 on the rear for winter?

I know the standard is 185... are those two sizes a bit too narrow? I realise narrower is better in the snow but once it dries up a bit it could get a tad lairy?

[WarrenG]

The rolling radius challenge is quite awkward at those sizes,

Tire Size Comparison
Specification Sidewall Radius Diameter Circumference Revs/Mile Difference
185/60-14 4.4in 11.4in 22.7in 71.4in 887 0.0%
165/65-14 4.2in 11.2in 22.4in 70.5in 899 -1.3%
165/70-14 4.5in 11.5in 23.1in 72.6in 873 1.6%
175/65-14 4.5in 11.5in 23.0in 72.1in 879 1.0%

info from http://www.miata.net/garage/tirecalc.html

[ChapppeRS]

Perhaps I'm not knowledgeable enough in this area but 1.3% doesn't sound like a lot?

[WarrenG]

If you use the java visual version of the calculator, it gives you and idea of what 1% means,

stock 185/60-14, 165/65-14 is 1.3% too fast, so speedo says 60, you are really doing 59.2mph
165/70-14 is 1.6% too slow, so speedo 60, actually 60.9mph
175/65-14 is 1.0% too fast, speedo 60, actual 60.6.

all not really much bother and certainly inside 10% for errors, but the sidewall heights will be interesting if the car was already lowered (like mine) and you didn't want to get any closer to difficulty. I'm already sledging along on the centre pile of snow and would like to go for really tall and narrow winters to offset that problem myself!

[itiejim]

Why would you want to run those sizes?

I really can't see any tangible benefit, it's not like MX5's are over tyred in the first place. You could also end up in trouble with insurance etc if you come unstuck.

[ChapppeRS]

itiejim said:

Why would you want to run those sizes?

I really can't see any tangible benefit, it's not like MX5's are over tyred in the first place. You could also end up in trouble with insurance etc if you come unstuck.

They're all that's available and I don't want to spend loads on winter tyres only to take them off in 2 months.

I think since I'm a big grown up boy with an engineering degree, and this is pistonheads i'm just going to do it and report back if it's wicked and/or I crash.

My idea was that in low grip or snow, you want narrower tyres to increase the pressure over the area of the tyre print.

Although, i've not bought them yet... Part of me is saying "man up, you did fine on slicks in go karts on the 23rd, and this winter weather will be gone in 2 weeks"

Edited by ChapppeRS on Friday 8th January 21:18

[itiejim]

Go for it. My point was simply that, whilst dedicated winter tyres and greater pressure on the road / square inch is of benefit, given the length of time that we are likely to be subjected to this weather I can't see that there is much to gain. Winter tyres are designed to be of benefit under 7 degrees C, that's the average daytime temperature for London in February. Above that temperature you're better off with summer tyres.

If you chose to go ahead I'd be inclined to keep the same size front and rear.

[Merlot]

OP; What winter tyres are you going for? I'd be very interested in how the '5 handles on winter tyres. My '5 is off the road during this winter, but I am considering 'winterising' it for next year, which would include buying a second set of wheels shod with decent winter tyres.

[Shelsleyf2]

Merlot said:

OP; What winter tyres are you going for? I'd be very interested in how the '5 handles on winter tyres. My '5 is off the road during this winter, but I am considering 'winterising' it for next year, which would include buying a second set of wheels shod with decent winter tyres.

[ChapppeRS]

I've kinda decided not to I think, I'm not sure it's worth it and I'm not sure I want to go for such skinny sizes just because they're all that's available.

Also I'm pretty good in low grip, so unless it's horrible to drive tomorrow night when I collect it, I probably won't bother. If I've still got the car in September I'll consider it again.

[Merlot]

ChapppeRS said:

I've kinda decided not to I think, I'm not sure it's worth it and I'm not sure I want to go for such skinny sizes just because they're all that's available.

Also I'm pretty good in low grip, so unless it's horrible to drive tomorrow night when I collect it, I probably won't bother. If I've still got the car in September I'll consider it again.

Fair play. If I do go ahead and winterise my MX5 for next winter instead of selling her in the summer, I'll probably go for Vredestein Snowtrac 3, I've heard nothing but praise for them.

[ChapppeRS]

Ah cool, yeah I'm sure they're good but I was just going to buy some
part worns off eBay! Firestone FW930

[MX-5 Lazza]

If part-worn means half-worn they will be no better than a set of new all-weather tyres.
They rely on deep wide grooves in the tread so if half of that is gone they won't be anywhere near as effective on ice & snow.

[ChapppeRS]

Well that's not really true, the compound and shape is still of the winter variety, and most I've looked at still have 5mm left. The use of them on snow is only a small part of the point of having them, although summer tyres usually do fine on dryish tarmac.

I've bought some now, I'll be driving the MX5 from this evening til Saturday without, and then I'll report back on how good they are and if I actually notice a difference!

£110 for 4 x Pneumant 185/60s including steelies!

Edited by ChapppeRS on Monday 11th January 10:29

[MX-5 Lazza]

I was comparing them to all-weather tyres, not summer tyres. The all weather tyres on my Focus (GY Hydragrip on the back & GY Efficient Grip on the front) have been fine on the ice & snow, even up the hill to our road which is a 4" sheet of compacted snow. Most good all weather tyres are designed to have some ability on snow & ice and don't need to be swapped when the weather warms up & dries out.
I haven't bothered even trying the MX5 since I have a choice of 3/4 worn F1s or 1/4 worn RS2s so I wouldn't stand a chance.

[ChapppeRS]

Ah fair enough, sorry skimmed over that. Yeah mine has some rather cheap looking summer tyres on it, so I should see a difference! Won't be able to fit them til the weekend though, because they're in Essex!

[Bonefish Blues]

Can I resurrect this thread please.

I have a Mk 2.5 Sport, so standard is 205/45 R16s.

I have picked up a set of old MX3 alloys which are 15x6.5. My plan was simply to put 195/50 R15 winter tyres on, which I see from the calculator would mean speedo reading ever so slightly too fast (1.1%).

Any issues here at all - doesn't seem to be any cost saving going for, e.g. 185/55s.

[Merlot]

Bonefish Blues said:

Can I resurrect this thread please.

I have a Mk 2.5 Sport, so standard is 205/45 R16s.

I have picked up a set of old MX3 alloys which are 15x6.5. My plan was simply to put 195/50 R15 winter tyres on, which I see from the calculator would mean speedo reading ever so slightly too fast (1.1%).

Any issues here at all - doesn't seem to be any cost saving going for, e.g. 185/55s.

No problem. 195/50 is standard MX5 size anyway for 15".

[MX-5 Lazza]

With 195/50/15 on Mk2.5 Sport you'll find the speedo will read 65mph when you are actually doing 60mph. Not really a problem.

[Bonefish Blues]

MX-5 Lazza said:

With 195/50/15 on Mk2.5 Sport you'll find the speedo will read 65mph when you are actually doing 60mph. Not really a problem.

Calculator o the Miata site puts the difference a little lower, but yes that agrees with my thoughts.

Thanks both - 4x Nokian WR G2s here we come.