For the '97/'98 winter, I installed Gislaved (pronounced GIS-la-ved) NordFrost II in the 175/65R14 size. Though the Bridgestone Blizzak has superior winter traction over a non-studded NordFrost II (mine are studded however) I recommend them anyway over Blizzaks. Tire construction is a cornucopia of compromises and the NordFrost II properly balances attributes I feel are important.
Wheel & Tire Size Issues:
My '97 "R" package Miata came with 185/60HR14 Bridgestones. The nominal diameter specification for this size tire is 22.74 inches. The wide, 185 mm body width of the stock summer tire is THE reason the Miata is such a slug during winter. With its wide footprint and light (exactly one metric ton) weight, the Miata can’t get a good bite into the snow. The universal rule for better winter traction is to get the narrowest possible winter tire with the same (or nearly same) diameter as the stock tire. The ideal tire for the Miata would be a 155R13. Such an 80-series 13-inch tire would give the highest ground loading available while maintaining a nearly dead-on nominal diameter spec of 22.76 inches. Of additional benefit, the 155R13 size is one of the least expensive sizes available. Unfortunately, all '94+ Miatas have rotor/calipers that are too large to accommodate 13-inch wheels (I’ve tried; no way). According to Richard Dekker -- Founder & President, Wild Rose Chapter - Miata Club of America -- 13-inch wheels from the 1990-95 Mazda 323 hatchback or Mazda Protege (lower models, not the LX) can fit pre-'94 Miatas.
For '94+ Miatas, the 175/65R14 size is the narrowest commercially available 14" tire in this diameter range (with a theoretical nominal diameter of 22.96 inches v.s. the stock 22.74 inches). This theoretical difference in diameter would make a car go 0.57 MPH faster at 60 MPH than the stock tire. However, differences due to the extra available tread depth wear capability as well as differences in inflation pressure and load deflection are more significant factors than this small theoretical difference.
Tire Construction
Gislaved is a Swedish company located near the town of Gislaved (surprise!!) in south-central Sweden. It was one of the first three companies to have produced steel-belted radial-ply tires and is now owned entirely by Continental. Notwithstanding the strong Swedish tie-in, my Gislaveds were manufactured in Austria. This, in its own right, helps make these tires way-cool.
The tire’s basic construction consists of a single ply of rayon cord with one nylon and two steel belts. This makes for a tire possessing robust puncture resistance but with extreme sidewall flexibility. More on this in a moment.
As for tread construction, don’t get confused by the discontinued Gislaved NordFrost (minus the "II"). Many dealers (as of winter '97/'98) still have remaining inventory of this earlier model tire. The NordFrost II has a tread with many of the same features as the U.S. military’s Hummer (only with more blocks, edges, and sipes): It has a central, relatively groove-free rib that reduces wandering and contributes to a smoother ride. Large shoulder blocks provide traction in deep snow and allow for sure-footed cornering on dry pavement. The main part of the tread is a sort of "morph" transition between the shoulder blocks and the central rib. Since this tire calls Scandinavia its home, it has holes for studs. I live in Eastern Washington state so I had mine studded. The tread compound has a fairly high percentage of natural rubber for added winter traction. This is, of course, at the expense of faster wear.
Winter Traction
First off: it’s WAY, WAY better than with the stock Bridgestones. I might as well have parked the car for the winter like it was a Lamborghini. I can now get around fine with the Gislaveds. The best way to evaluate winter traction is to compare yourself to how others are doing at the time. In the "go forward" department, my Miata has an ace up its sleeve. "R" package Miatas as well as other Miata packages over the years, are equipped with Torsen limited-slip differentials. This means that we essentially have two-wheel drive as opposed to conventional-differential rear-wheel drive cars (which are really only "one-wheel" drive). All-in-all, under acceleration, I figure I can go forward about as well as can any front-wheel drive car equipped with a conventional differential and typical winter tires. That’s pretty good. I was able to accelerate forward from a complete stop on an approximately 8% uphill grade on top of three inches of virgin snow. A tough test. Plus, the bottom half-inch of the snow was re-frozen, packed corn ice. As for stopping, the narrow (135 mm) well designed tread and studs on all fours makes for kick-butt stopping power. I suspect few cars can do much better.
Trade Off’s
Tire construction engineering is an exercise in the art of compromise. Remember the single-ply sidewall? The Gislaved absorbs sonic vibrations and shocks very, very well. I can hear the studs howling, but surprisingly little of their vibration gets through to the R-package’s stiff sport suspension. This is good, otherwise every single little component in the dash that COULD possibly work the littlest bit loose, would. These parts would then sympathetically vibrate to the fundamental frequency (or some harmonic) of the studs at freeway speeds. Washboarding -- normally encountered only on dirt roads during summer -- is a common hazard in winter driving. Washboarded roads that I wouldn’t have DREAMED of going over with my summer Bridgestones were completely absorbed by the Gislaveds. The trade off? When I first put these tires on and went down a dry road, I thought one of my tires was inflated to only 12 psi. I actually got out of the car and checked the tire pressure. I might as well have had 300 pounds of concrete slung under both bumpers. I haven’t experimented with increased tire pressure yet. This might help but could be at the expense of even tread wear and would definitely be at the expense of shock isolation. Remember though, the Miata R-package has even more of a sport suspension that the standard Miata. It doesn’t even have power steering; you’ve got a lot of road feel. In performance driving, you don’t just feel what the tires are "doing"; with the R-package you can feel what they’re THINKING. I’ve never before driven a car with such a finely-tuned suspension that it made a huge apparent difference in the feel between summer and winter tires.
This brings us to our second trade off issue: tread compound. The Bridgestone Blizzak has a patented tread compound that makes it essentially a closed-cell foam rubber. At the microscopic level, the stuff looks like swiss cheese. Bridgestone says this rubber compound gives the Blizzak superior traction on ice (I’m sure it does) so they elected to omit holes for studs! The trade off is tread life. The multicell rubber compound wears down so fast, Bridgestone made only the top half of the tread from this special material. I’ve been told by two authorized Bridgestone dealers that after the first season, one is left with only a conventional, unstudded mud & snow tire. Who said being able to stop on ice during the second year is not as important as during the first??
The second Blizzak v.s. NordFrost II trade off: tread design. The NordFrost II uses a super-winterized version of the Hummer military tire design with a central rib morphing to blocky (but stout) shoulder blocks. The Blizzak on the other hand has a fine-pitch checker board, across the entire tread width, of independent squarish blocks. More like towers really. Try pushing across the tops of one of the Blizzak’s tread blocks with only the traction of a finger tip. You can make them sway back and forth like pencils jammed into a tire carcass. I’ve read that the Blizzaks act "squirrelly" while driving down the road; I can see why.
My suggestions:
1) If you’ve got money to burn, don’t like the noise of studded tires, and want unexcelled winter traction year after year, buy $350-worth of Blizzaks each winter. To extend their life, try installing them late in the season and take them off early. They’ll behave "squirrely" on bare roads since Bridgestone went all-out in the compromises department to obtain maximum unstudded winter traction. Still, I think Blizzaks are over-compromised and over-hyped. Their price reflects it too.
2) Get Gislaveds and have them studded. You’ll have to put up with the noise of the studs but I bet studded Gislaveds will kick Blizzaks' butt on ice any day. They have stable tracking and driveability on dry pavement. Their "go" ability is fine on a Miata and their stopping power on compressed snow/ice is outstanding. They’ll give you several seasons in a row of consistently high winter traction before wearing out too.
| Back to Product Reviews | 14 June, 1998 |