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Old 05-07-2010, 05:32 PM   #1
RiceyHot
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Question Ride Comfort: 245/40-17 vs. 245/45-17

Okay, firstly, I did a search. My question is kinda specific.

First, some info about my setup:


  • 2005 Subaru WRX sedan
  • OEM Struts/shocks
  • Eibach Pro-Kit springs (~1.2 inch drop)
  • OEM front sway bar
  • Cusco rear sway bar w/Kart Boy endlinks
  • Camber: OEM settings all around
  • All fenders are rolled
  • Wheels: Work Emotion CR Kai (17x9)
  • Current tire size: 235/40-17

Okay, so I'm in the market for a new set of tires, and my primary concern is ride comfort. I know, I know, you don't get 17x9 size wheels for ride comfort, but my secondary concern (only a tad less important than my primary) is appearance. I like the 9-inch wide look.

I live in an area with super crappy roads, and I have a pretty harsh ride right now when I hit bumps and pot holes. For my next set of tires I want a wider tire (previous owner of the wheels slapped the 235's on them, which are stretched pretty good on the 9-inch wide wheel right now), so I am definitely going with a 245. I don't want to consider 255's because I don't want any fender rubbing issues.


Question is, would getting a taller tire (245/45-17) result in better ride comfort and taking bumps better due to more sidewall???


I know 245/45-17 tires are hideous/huge and about one full inch taller in diameter over stock, but I'm tired of cringing every time I take a bump too hard. I have decent
wheel clearance right now since my drop is not that low and my fenders are rolled, so I'm pretty sure the 45's will fit just fine.


I've done a comparison in tire size and this is what I found:


Specification___Sidewall_Diameter_Circumference__R evs/Mile_Difference
205/55-16(OEM)_4.4in___24.9in_____78.2in________811____0. 0%
245/40-17______3.9in___24.7in_____77.6in________816____-0.6%
245/45-17______4.3in___25.7in_____80.7in________785____3. 2%


So basically the 40's will ride very close to stock (good thing), and the 45's will ride slightly sluggish (longer gearing). But if the ride quality is improved, I'd still consider them.

Any input would be greatly appreciated.

Some pics of my setup and pics of the plenty of wheel gap that I have:


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Last edited by RiceyHot; 05-07-2010 at 06:06 PM.
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Old 05-07-2010, 05:41 PM   #2
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I would run 255/40s. 245/45s are pretty tall on a WRX gearing wise. If comfort is your only concern then go for it!
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Old 05-07-2010, 06:52 PM   #3
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Quote:
Originally Posted by Badler View Post
I would run 255/40s. 245/45s are pretty tall on a WRX gearing wise. If comfort is your only concern then go for it!
Out of curiosity I tried plugging in the 255/40-17 into a tire size calculator to see the dimensions and I discovered that as you go with a wider tire, you increase sidewall size more than I thought.

I knew that as the width of the tire got larger the sidewall can increase in size slightly as well, but I didn't know it made a considerable difference....

If I go with 255/40-17's (vs. the 235/40's that I already have) I will gain 0.3 inch more side wall without even having to increase the tire height.

I think I may go with your 255/40 suggestion!
Thanks for the input.
Let's just hope I don't rub any fenders with the 255's.

And if anyone is interested in a great tire size calculator:

http://www.miata.net/garage/tirecalc.html
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Old 05-07-2010, 06:57 PM   #4
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Not sure about your current fender mods but you may require a little more to fit the 255s. The eibachs are pretty soft. Good luck!!!
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Old 05-07-2010, 07:53 PM   #5
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I have them rolled all around. My wheel gap is pretty big...kinda annoying actually. You think I'll have issues with 255/40's even with them rolled? I don't want to get them pulled at any cost. Thing that sucks about this is that I won't know for sure until I throw the 255's on them. Crap.
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Old 05-07-2010, 08:11 PM   #6
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Unfortunately alot of this stuff is trial and error. I would search around and find someone running similar specs and pick their brain. Wish I could help more.
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Old 05-07-2010, 08:19 PM   #7
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Ask in the motorsports forum and note the wheel offset as well. Likely your stock camber is going to be a problem. Also, not saying you won't notice it(depends on your butt dyno), but the gearing issue shouldn't be much of a concern if you're not competing in a motorsport.
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Old 05-08-2010, 02:13 PM   #8
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Thanks for the info/input guys. For now, I'm just gonna suck it up and get the 245/40-17's. I'll just have to be more careful going over bumps/holes. I can't afford to get a camber kit/coilovers/fenders pulled right now so I'll hold off on the 255's. However, I will ask the Motorsport forum just for shlts and giggles to see if anyone is running a very similar setup to me and see if 255's fit under their fenders.
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Old 05-08-2010, 03:12 PM   #9
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Ride comfort can be more the tire you choose and not the size. Some tires have stiffer side walls than others. One example is the RE070 / stock tire on the 04-07 STi (225-45-17). They have very stiff sidewalls and are also a heavy tire at 27lbs each. On the other hand, I have some 235-40-18 tires that are only 21lbs each soft side wall and nice ride (on my wifes LGT). Check the reviews on TireRack for more info, they do include ride comfort in the reviews. FYI the 2nd number on the tire (45,40) etc is the percentage of the tire width so a 255-40-17 is taller than a 245-40-17.
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Old 05-08-2010, 03:36 PM   #10
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Quote:
Originally Posted by MD04WRX View Post
Ride comfort can be more the tire you choose and not the size. Some tires have stiffer side walls than others. One example is the RE070 / stock tire on the 04-07 STi (225-45-17). They have very stiff sidewalls and are also a heavy tire at 27lbs each. On the other hand, I have some 235-40-18 tires that are only 21lbs each soft side wall and nice ride (on my wifes LGT). Check the reviews on TireRack for more info, they do include ride comfort in the reviews. FYI the 2nd number on the tire (45,40) etc is the percentage of the tire width so a 255-40-17 is taller than a 245-40-17.
Hmm, good point. Thanks for the info. Yeah, I'll do some research on the tire sidewall stiffness as well....I'm trying to save money right now, so I won't be able to get the "best" tires out there. I'm looking at a set of Hankook Ventus V4 ES H105 or a set of Falken Ziex ZE-912. Both sets get mixed reviews...mostly good, but some bad. I'll have to see if I can figure out which ones have a softer sidewall.

Yeah, I did discover that the 255/40's are about 0.25 inches taller in sidewall than the 245/40's. Interesting...I didn't know the 2nd number was a percentage. It all makes sense now...no wonder that number is listed as "ratio". Learn something new everyday on this crazy 'ole internet.
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Old 05-08-2010, 05:50 PM   #11
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Quote:
Originally Posted by RiceyHot View Post
I'm looking at a set of Hankook Ventus V4 ES H105 or a set of Falken Ziex ZE-912.
Do you really want ALL-SEASON tires in SoCal? They both suck on snow if you were thinking to use them to the mountains in winter.

I'd get Hankook Ventus V12 evo K110 or Sumitomo HTR Z III if I were you... they both have $50 rebate offer now.
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Old 05-08-2010, 09:20 PM   #12
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Quote:
Originally Posted by Fendyman View Post
Do you really want ALL-SEASON tires in SoCal? They both suck on snow if you were thinking to use them to the mountains in winter.

I'd get Hankook Ventus V12 evo K110 or Sumitomo HTR Z III if I were you... they both have $50 rebate offer now.
Honestly, no I do not want all-season tires...but I wanted to get tires that are around $100 bucks a piece and have good tread life. So yes, by doing this I do sacrifice some performance. I have a set of winter wheels that have snow tires on them already, so snow traction is not a concern with my next tire purchase.

I currently have Yokohama S Drives on my car....and I like them a lot, but I want something with slightly softer sidewalls (for the crappy roads where I live) and more tread life (S Drives have a treadwear rating of 300, as opposed to the Zeix-912 that have 360).

I've ruled out the Hankook Ventus V4 ES H105 because they have some pretty negative reviews. The 912's aren't great at anything and are poor in the snow (not a factor), but they are $95.00 a piece and last a little longer than S Drives.

I was actually considering the Falken FK-452's...more of a performance tire and I can get them for $100.00 a peice, but they do have the 300 treadwear rating that the S Drives have.

Hmm...I'm always debating between daily-driveability/ride comfort and performance. I'm trying to find a happy medium since this is my daily driver and I drive over crappy roads everyday.

The Venus V12 evo K110 seems like a badass tire, but they have a treadwear rating of 280. Too low for my daily driving. The Sumitomo HTR Z III have a rating of 300 and are under $100...surprisingly!

If I go with a performance tire, I will be debating between the Falken FK-452, the Sumitomo HTR Z III, and the Yokohama S Drives. I have about another month or two before absolutely having to replace my current tires.
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Old 05-08-2010, 09:30 PM   #13
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Quote:
Originally Posted by Fendyman View Post
I'd get Hankook Ventus V12 evo K110 or Sumitomo HTR Z III if I were you... they both have $50 rebate offer now.
I did some reading up on the Sumitomo HTR Z III...I like 'em. However, I didn't see that $50 rebate at Tirerack's website. How do I get the rebate???
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Old 05-08-2010, 09:35 PM   #14
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Nevermind, I found it.
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Old 05-09-2010, 12:52 PM   #15
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oh jesus....this thread is FAILBOAT through and through
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Old 05-10-2010, 12:48 PM   #16
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RiceyHot - Don't put too much stock in comparing treadwear ratings from different tire manufacturers. Read Tire Rack's tech page about the UTQG markings and you'll understand that the treadwear ratings are really only a guideline.

Even without knowing what tires you're running now, I think you'll likely see a ride comfort benefit just by going to tires that are more appropriately sized to the wheels. That will put the sidewalls in a position they're actually designed for, rather than being stretched like the 235s you have now. And MD04WRX's comments about the type/brand/model of tire having a big impact on ride quality is also very true. Some performance tires have a reputation for having a softer sidewall (like the FK452s you mentioned, for instance). Others (mostly in the max/extreme performance range, which is well above the price range you're looking at) have very firm sidewalls.

Quote:
Originally Posted by Uncle Scotty View Post
oh jesus....this thread is FAILBOAT through and through
More valuable input from the guru. It must be exhausting to just give and give and give like you do.
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Old 05-10-2010, 04:10 PM   #17
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Specification___Sidewall_Diameter_Circumference__R evs/Mile_Difference
205/55-16(OEM)_4.4in___24.9in_____78.2in________811____0. 0%
245/40-17______3.9in___24.7in_____77.6in________816____-0.6%
245/45-17______4.3in___25.7in_____80.7in________785____3. 2%

Pick Diameters 24.3" to 25.0"
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Old 05-10-2010, 04:13 PM   #18
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Quote:
Originally Posted by mosc View Post
Specification___Sidewall_Diameter_Circumference__R evs/Mile_Difference
205/55-16(OEM)_4.4in___24.9in_____78.2in________811____0. 0%
245/40-17______3.9in___24.7in_____77.6in________816____-0.6%
245/45-17______4.3in___25.7in_____80.7in________785____3. 2%

Pick Diameters 24.3" to 25.0"
This. 45 sidewalls are too tall IMO.
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Old 05-10-2010, 04:27 PM   #19
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Diameter. Ignore sidewall entirely except to compute diameter. Look at Diameter.
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Old 05-10-2010, 04:33 PM   #20
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No, you want to look at circumference and revolutions per mile.
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Old 05-10-2010, 04:38 PM   #21
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Circumference and diameter are directly proportional. There is no difference in looking at one or the other. The issue is using "sidewall ratio" on it's own, which is totally meaningless without context (specifically a tire width and wheel height which will lead you to diameter and circumference).

Seriously, is another poster going to say "No, diameter AND circumference are useless, look at radius"? Didn't somebody pass middle school geometry around here?
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Old 05-10-2010, 07:22 PM   #22
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d00000000000000000000d...

it is ****ing totally all about ****ing radius!!!
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Old 05-10-2010, 07:25 PM   #23
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With larger numbers it's easier to see differences. And when it comes to correct odometer/speedometer readings, revs are what matter. Hence:

Quote:
Originally Posted by Byzantium View Post
No, you want to look at circumference and revolutions per mile.
It was merely a recommendation to help someone easier understand the issues at hand.

Last edited by Byzantium; 05-10-2010 at 07:34 PM.
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Old 05-10-2010, 08:13 PM   #24
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Hey guys, thanks for all of your great input and patience. Newbs like myself gotta learn somewhere, and NASOIC is probably the hardest place to do that since a lot of senior members are so bitter and impatient with us.

The original question was whether or not a 45 ratio tire would provide a less harsh ride than a 40 ratio tire. All of you helped answer the question for me very clearly: I should not be concerned with the tire ratio, I should just put the correct size tire on the wheels that I have. I will do so. After reading what you guys posted and re-analyzing the tire size chart and looking more at diameter, I have conclude that I will stay away from the 45's.

Another thing that Patrick pointed out that was very helpful is the treadwear/tread life rating of the tire. Patrick, I did read the "UTQG markings" link that you posted and learned a lot. I will be getting a summer "performance" tire rather than an all-season, as a 300 treadware rated performance tire will not wear that much faster than a 360 all-season. I'll try to find a performance tire with a softer sidewall to handle my crappy roads a little better.

Uncle Scotty - I understand the time that you have put in on this board and I realize that you have much knowledge and experience...what I don't understand is why you choose not to share it? Rather than posting something constructive you bash the thread. Isn't this what the "NASOIC Technical" forum is for? Technical questions about our cars? I didn't think I posted a repetitive question without trying to do some type of research on it first.

What's more surprising is that you are a "Scooby Guru". It was my understanding that a "guru" in any field of expertise is one who is regarded as having great knowledge, wisdom and authority in a certain area, and who uses it to guide others. Would your title here be a fallacy? I think with experience and knowledge should come the maturity and responsibility to use it with wise discretion. I am an open minded person, but I see no necessity in your post. Either way, I'm not here to argue with you on a public forum. You can post whatever you want...after all, you are a "Scooby Guru".

Hmm...I do wonder though, what would the threads on this forum consist of if ALL of the members were "guru's"? Would you guys just stroke each others egos all day or what? I mean, would any questions even be posted since all of the members already know EVERYTHING?

(No offense to helpful Scooby Guru's like "Byzantium" and NASIOC Supporter's like "Patrick Olsen".)
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Old 05-10-2010, 11:46 PM   #25
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Quote:
Originally Posted by Patrick Olsen View Post
d00000000000000000000d...

it is ****ing totally all about ****ing radius!!!
This is so well done, I tip my hat!

If you care about ride comfort, you can control sidewall by controlling wheel width. 19" wheels may look cool but do not provide much value at smaller widths, especially if you personally value decent ride comfort. You can actually get 15" wheels that will clear your brakes remember. Anything more is going to directly sacrifice comfort. Not that I wouldn't recommend a little stiffer sidewall for a performance car than you're going to find in a 15" tire mind you, just something to think about. 17" choices between stock and 3% below stock diameters generally provide a good balance of gearing, cushion, sidewall, and good value for WRX applications.
Quote:
Originally Posted by Byzantium View Post
With larger numbers it's easier to see differences.
If you put that on a test I gave, I'd give you an F. Sorry, but that makes no sense. Significant figures do not increase with magnitude.
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