Buying new tires: do I need to stick with the same size?
January 14, 2012 8:50 AM Subscribe
Need new tires for my wife's 2003 3 series. Do I stick to the same tires: 225 / 45Z / R17 (expensive)? Or can I go with stores' web sites suggested 205 / 55 / 16?
Background:
Our 2003 3 series BMW has only 25,000 miles on it. We live in Colorado and we find the rear wheel drive BMW tough in the snow. (Our main car, front wheel drive Toyota, for which I have both summer and winter tires is a dream.)
Because we do such low mileage in this car I don't want to bother having two sets of tires. We barely drive it so I just want to get a set of tires to use all year round that are great in the snow (so not all seasons) and pretty good on the road. I've settled at these Michelins.
They cost $160 each if I go with the site's suggested 205 / 55 / 16. However, her existing tires are 225 / 45Z / R17 which are $210. I understand that narrower wheels perform better on snow--so 205 is perhaps a better option anyway?
Background:
Our 2003 3 series BMW has only 25,000 miles on it. We live in Colorado and we find the rear wheel drive BMW tough in the snow. (Our main car, front wheel drive Toyota, for which I have both summer and winter tires is a dream.)
Because we do such low mileage in this car I don't want to bother having two sets of tires. We barely drive it so I just want to get a set of tires to use all year round that are great in the snow (so not all seasons) and pretty good on the road. I've settled at these Michelins.
They cost $160 each if I go with the site's suggested 205 / 55 / 16. However, her existing tires are 225 / 45Z / R17 which are $210. I understand that narrower wheels perform better on snow--so 205 is perhaps a better option anyway?
Yeah, just in case you missed that, the final number (16/17) is the diameter of the actual metal wheel on the car in inches. If you switch from 17s to 16s, you have to buy new wheels.
posted by hwyengr at 9:22 AM on January 14, 2012
posted by hwyengr at 9:22 AM on January 14, 2012
Best answer: Yeah, you're talking about two completely different tire sizes here.
Your original tires are 225/45Z/R17. This reads as:
225 - nominal width of tire is 225mm
45 - ratio of sidewall height to width; sidewall is 45% of nominal width (~101mm in this case)
Z - likely the speed rating of the tire (149+mph)
R - radial
17 - 17" rim diameter (the metal wheel that the rubber tire gets mounted onto)
As Old Geezer says, if you switch to the suggested 205/55/16, you'll be attempting to fit a 16" diameter tire onto your 17" diameter wheels. Not gonna happen. Especially with the nice rims your BMW likely has on it, the cost of a new set of 16" rims to fit the cheaper tires is going to far exceed the difference in tire prices.
posted by xedrik at 9:24 AM on January 14, 2012
Your original tires are 225/45Z/R17. This reads as:
225 - nominal width of tire is 225mm
45 - ratio of sidewall height to width; sidewall is 45% of nominal width (~101mm in this case)
Z - likely the speed rating of the tire (149+mph)
R - radial
17 - 17" rim diameter (the metal wheel that the rubber tire gets mounted onto)
As Old Geezer says, if you switch to the suggested 205/55/16, you'll be attempting to fit a 16" diameter tire onto your 17" diameter wheels. Not gonna happen. Especially with the nice rims your BMW likely has on it, the cost of a new set of 16" rims to fit the cheaper tires is going to far exceed the difference in tire prices.
posted by xedrik at 9:24 AM on January 14, 2012
Response by poster: I wasn't factoring that in. Thanks! Darn it. Definitely don't want to buy New wheels. OK so I guess I need to buy those pricier ones then.
posted by NailsTheCat at 9:36 AM on January 14, 2012
posted by NailsTheCat at 9:36 AM on January 14, 2012
Besides the wheel thing, changing tire sizes beyond a certain narrow range of diameters and widths can drastically affect handling. The engineers have designed all the suspension components to work at a certain angle at certain loadings (like how the car leans around corners and hits a bump mid corner). In addition to this changing tire size will change the thrust angle on the wheel bearings wearing them out faster. A heavier tire/wheel combo will wear out everything in the suspension faster. And lastly the different tire size will cause the wheel to rotate at a different speed for a given road speed which will through off the sensors that things like your abs depend on. YOu can change a little in width and sidewall size and still be ok and you can change wheel sizes as long as your are pretty close to the original tire diameter and be ok but nothing is going to work as well as the stock size the factory set up the car for. The last specification you need to be aware of is the speed rating of Z. You may never go that fast (who goes 149 on public roads?)but a tire that can go that fast is also capable of handling at a much higher level than the standard S (112mph) speed rating.
Also this matters a lot more on something like a modern BMW than an old Chevy pickup.
posted by bartonlong at 11:56 AM on January 14, 2012
Also this matters a lot more on something like a modern BMW than an old Chevy pickup.
posted by bartonlong at 11:56 AM on January 14, 2012
Response by poster: Thanks for all the great comments. I've taken it all on board and will still with the same size tires and a high speed rating. I'm now deliberating over whether to get:
Michelin Pilot Alpin PA3 (winter tires that seem good on pavement too) or
Continental ExtremeContact DWS (the best all season on snow)
Blizzaks are also a fairly reasonably priced option, which I have as winter tires on my car. But I don't think they would be so great in summer.
posted by NailsTheCat at 12:25 PM on January 14, 2012
Michelin Pilot Alpin PA3 (winter tires that seem good on pavement too) or
Continental ExtremeContact DWS (the best all season on snow)
Blizzaks are also a fairly reasonably priced option, which I have as winter tires on my car. But I don't think they would be so great in summer.
posted by NailsTheCat at 12:25 PM on January 14, 2012
If you have enough space for car-related items, you might want to consider a spare set of rims from Craigslist or a salvage yard; that way, you could use the Continentals when necessary, and extend their life by storing them for the rest of the year.
posted by Smart Dalek at 2:56 AM on January 15, 2012
posted by Smart Dalek at 2:56 AM on January 15, 2012
Response by poster: you might want to consider a spare set of rims
I do this with the other car and it's definitely a great idea. However since we average 3k a year on this car, I don't think we'll have worn much off the Continentals by the time we get round to selling it (in a year or two probably) and so it's probably not worth the trouble/expense of new rims. Thanks for the suggestion though.
posted by NailsTheCat at 9:57 AM on January 16, 2012
I do this with the other car and it's definitely a great idea. However since we average 3k a year on this car, I don't think we'll have worn much off the Continentals by the time we get round to selling it (in a year or two probably) and so it's probably not worth the trouble/expense of new rims. Thanks for the suggestion though.
posted by NailsTheCat at 9:57 AM on January 16, 2012
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posted by Old Geezer at 8:58 AM on January 14, 2012 [1 favorite]