Why the difference in front & back tire profiles
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Joined: Feb 2006
Posts: 58
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From: Fort Collins Colorado
Why the difference in front & back tire profiles
-This maybe a stupid question, but here goes - Why are the profiles of front tires higher than the rears I.E 245/45/17 vs. 275/40/18. 45 vs. 40Is the a performance reason or something?
- Second question is when I get my new run flats I would like to get the same profile all the way around - is that O.K. ?
thanks as always for the responses.
- Second question is when I get my new run flats I would like to get the same profile all the way around - is that O.K. ?
thanks as always for the responses.
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Joined: Oct 2002
Posts: 16,477
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From: Gone
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St. Jude Donor '03
Simple answer: Because they're narrower.
The profile number is basicaly the sidewall thickness expressed as a percentage of the tire's width.
The wider a tire becomes, using the same profile, the taller it becomes. If you go to a wider tire, then going down in profile will keep the sidewall and tire height about the same.
As a good example, compare these two size tires.
245/45/17
275/40/17
45% of 245 makes for about the same size sidewall as 40% of 275, so although the 275 is much wider, both tires end up being about the same overall height. .
I wouldn't worry about the profile number. Worry about keeping the overall tire height about stock, and use the profile that gets you closest to that in your desired width. If you simply went with a 245/40/17 tire to "match" the 275/40/18 rears because you're concerned about the profile number matching...you would end up with a very short front tire with much less sidewall thickness than the rears.
As far as runflats, you will be very limited in what non-stock sizes you can get. Most runflats are made in OE sizes and that's it.
The profile number is basicaly the sidewall thickness expressed as a percentage of the tire's width.
The wider a tire becomes, using the same profile, the taller it becomes. If you go to a wider tire, then going down in profile will keep the sidewall and tire height about the same.
As a good example, compare these two size tires.
245/45/17
275/40/17
45% of 245 makes for about the same size sidewall as 40% of 275, so although the 275 is much wider, both tires end up being about the same overall height. .
I wouldn't worry about the profile number. Worry about keeping the overall tire height about stock, and use the profile that gets you closest to that in your desired width. If you simply went with a 245/40/17 tire to "match" the 275/40/18 rears because you're concerned about the profile number matching...you would end up with a very short front tire with much less sidewall thickness than the rears.
As far as runflats, you will be very limited in what non-stock sizes you can get. Most runflats are made in OE sizes and that's it.
