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slight change in tire diameter

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Old Jun 17, 2008 | 08:00 AM
  #1  
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slight change in tire diameter

If one desired to change the fits final drive ratio just a little bit by installing SLIGHTLY taller tires what would be my options? This is on stock sport rims. I know the speedometer would be off but I'd like to go for slightly lower revs at highway speeds without major expense. I don't want any rubbing.
 
Old Jun 17, 2008 | 10:32 AM
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195/60/15's? they are going to look very ugly with those balloon tires...
 
Old Jun 17, 2008 | 01:39 PM
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subtle

Originally Posted by kenchan
195/60/15's? they are going to look very ugly with those balloon tires...
That size is what I guessed. I'd hardly call 60 series balloon tires. I doubt that the difference would be that easy to see to the casual observer. Tire replacement is a ways off (5700 miles) so I'm just bouncing the idea around for now. I'm just looking for cheap ways to tweak mileage upward.
 
Old Jun 17, 2008 | 02:07 PM
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50's are borderline.

60's are definitely balloons.
 
Old Jun 17, 2008 | 03:45 PM
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Originally Posted by feddup
If one desired to change the fits final drive ratio just a little bit by installing SLIGHTLY taller tires what would be my options? This is on stock sport rims. I know the speedometer would be off but I'd like to go for slightly lower revs at highway speeds without major expense. I don't want any rubbing.
I would suggest 205-50-15 on stock rim there be no rubbing and the look would be awesome.
 
Old Jun 17, 2008 | 04:22 PM
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diameter?

Originally Posted by fitoromocto
I would suggest 205-50-15 on stock rim there be no rubbing and the look would be awesome.
Wouldn't that decrease the outer diameter? Looks are not my primary concern. I'm 46 and couldn't care less what the kids say. 60s aren't balloons. The "series" of the tire is the percentage that the sidewall height is of the width of the tire. The sidewall height of the stock sport tires should be 55% of 195mm = 107.25. The sidewall height of the 205/50/15 should be 50% of 205 = 102.5mm. I believe the height of the ladder tire would be less which is the opposite of what i desire. Looks definitely matter but so does mileage and, in my case lower revs at highway speeds. I'm well aware that this will lose me some acceleration as well. I'm just bouncing around ideas since my car only has 5700 miles on it. I'm old and don't "FIT" the typical fitfreak demographic. I'm aware of that. I bought a brand new Honda because all the used ones had been "Modded" to the point that mileage and dependability had been compromised. All my "Mods" will be in an effort to save money in the long term which, to me, is what the Fit is about. Anyway any further ideas or criticism is welcome.
 

Last edited by feddup; Jun 17, 2008 at 04:23 PM. Reason: spelling
Old Jun 17, 2008 | 05:28 PM
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Originally Posted by feddup
Wouldn't that decrease the outer diameter? Looks are not my primary concern. I'm 46 and couldn't care less what the kids say. 60s aren't balloons. The "series" of the tire is the percentage that the sidewall height is of the width of the tire. The sidewall height of the stock sport tires should be 55% of 195mm = 107.25. The sidewall height of the 205/50/15 should be 50% of 205 = 102.5mm. I believe the height of the ladder tire would be less which is the opposite of what i desire. Looks definitely matter but so does mileage and, in my case lower revs at highway speeds. I'm well aware that this will lose me some acceleration as well. I'm just bouncing around ideas since my car only has 5700 miles on it. I'm old and don't "FIT" the typical fitfreak demographic. I'm aware of that. I bought a brand new Honda because all the used ones had been "Modded" to the point that mileage and dependability had been compromised. All my "Mods" will be in an effort to save money in the long term which, to me, is what the Fit is about. Anyway any further ideas or criticism is welcome.
Go to tire rack .com (our sponsor) check out the 205 55/15s and pick one and check the tires specs. most are .3 to .5 inches taller than the 195 55/15s (23.4"). Our speedos off 2 to 4% fast so I think with these you'll still be going slower than you really are(on the speedometer).
 

Last edited by 08FitSport; Jun 17, 2008 at 05:32 PM.
Old Jun 17, 2008 | 05:36 PM
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Originally Posted by feddup
Looks are not my primary concern. I'm 46 and couldn't care less what the kids say. 60s aren't balloons.

All my "Mods" will be in an effort to save money in the long term which, to me, is what the Fit is about. Anyway any further ideas or criticism is welcome.
you can careless about wat a 'kid' says yet you are aggrivated
by getting called a ballooner for running 60 profile...lol.


you want to change gear ratio for wat? better mpg? if so, i
suggest a scangauge if you want to save money on gas. cheaper
than getting a new set of tires. some have netted over 40mpg using
the monitor and watching their driving habits. much more efficient
than trying to change your final ratio while adding more unsprung
weight on the wheels. you might improve mpg during cruising
speeds but could potentially waste more fuel when you run into
traffic due to the taller ratio.

you have knowledge in tire calculation so i am assuming you are
already using higher psi than factory. if not, i suggest pumping it
higher to 35psi range cold. i dont suggest going too much higher
especially on a hot summer day.
 
Old Jun 17, 2008 | 05:40 PM
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Originally Posted by 08FitSport
Go to tire rack .com (our sponsor) check out the 205 55/15s and pick one and check the tires specs. most are .3 to .5 inches taller than the 195 55/15s (23.4"). Our speedos off 2 to 4% fast so I think with these you'll still be going slower than you really are(on the speedometer).

i think it's the other way around.... my car shows 45mph when the
police radar thingie shows 42mph. im shorter running 195/50/15's.
 
Old Jun 17, 2008 | 05:52 PM
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Originally Posted by kenchan
i think it's the other way around.... my car shows 45mph when the
police radar thingie shows 42mph. im shorter running 195/50/15's.
Yes, so with shorter tires you're going slower than the speedometer. 195 55/15 will be about 43.5 and 205 55/15 is about 44.5 maybe on the money.
 
Old Jun 17, 2008 | 05:56 PM
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Originally Posted by 08FitSport
Yes, so with shorter tires you're going slower than the speedometer. 195 55/15 will be about 43.5 and 205 55/15 is about 44.5 maybe on the money.
ok ok...

so shorter tires = actually going slower than the odo.

taller tires = actually going faster than the odo.
 
Old Jun 17, 2008 | 06:23 PM
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tires

Originally Posted by kenchan
you want to change gear ratio for what? better mpg? if so, i
suggest a scangauge if you want to save money on gas. cheaper
than getting a new set of tires. some have netted over 40mpg using
the monitor and watching their driving habits. much more efficient
than trying to change your final ratio while adding more unsprung
weight on the wheels. you might improve mpg during cruising
speeds but could potentially waste more fuel when you run into
traffic due to the taller ratio.

you have knowledge in tire calculation so i am assuming you are
already using higher psi than factory. if not, i suggest pumping it
higher to 35psi range cold. i dont suggest going too much higher
especially on a hot summer day.
I'm running 38psi cold. I wanted a scanguage but can't afford it. The machine shop I work at went down two weeks ago. I won't replace the tires on a whim. I researched the fit for months before I bought it and I'll put that much thought into it before I change tire sizes. I'll replace the tires when the ones I'm running wear out. Not a moment before!
 
Old Jun 18, 2008 | 07:56 AM
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Originally Posted by feddup
If one desired to change the fits final drive ratio just a little bit by installing SLIGHTLY taller tires what would be my options? This is on stock sport rims. I know the speedometer would be off but I'd like to go for slightly lower revs at highway speeds without major expense. I don't want any rubbing.
Very interesting. The 19/55x15 tires are 23.44" diameter. Hre are some choices:
195/60x15 24.21" (3.2% change)
185/50x15 23.74" (1.2% change)
165/70x15 24.09" (2.7% change) couldn't find 'em on discount tire or tire rack
175/65x15 23.95" (2.2% change)
185/60x15 23.74" (1.2% change)

The 165/70x15 used to be very popular so may be lower cost and is my recommendation.
However its not available. The next choice is 175/65x15 tires and they are a good choice available from several manufacturers. And 185/60x15 as well.
If you want better mileage when you go larger on diameter you don't need much; if you increase more than an inch the extra power requirement eats up the gain. So you go narrower as well so the rolling resistance is reduced.
And 2% isn't worth considering as an odo and speedo error. 2% at 60 is 1.2 mph; 2% on odo results in 'saving' 20 miles in a thousand.
And it might be worth your time to find some used steel wheels to mount them on. A 5" rim will handle 175 nicely and will indeed need a a little extra air pressure to keep the tread flat and that too will increase mpg. Longer wear ratings will help also but be aware your sport performance is reduced. There is no free lunch.
You should be able to get as much as 5 mpg that way but more likely 3 mpg more.
good luck.
 

Last edited by mahout; Jun 18, 2008 at 03:23 PM.
Old Jun 18, 2008 | 08:26 AM
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195/60s

I think that 195/6015s will probably be the way I'll go. It might be year from now though. I'd prefer not to go narrower as 195 is pretty narrow to start with. 3% sounds perfect as far as lowering the highway revs (for an MT) and not messing up the speedometer readings too much. Also I checked tirerack and there are many excellent relatively inexpensive choices. I'm willing to compromise some handling and acceleration in the name of mileage but don't want to get freaky about it. I think Honda made excellent choices as far as mileage/performance/handling/ride compromises and I don't want to deviate far from them.
 
Old Jun 18, 2008 | 11:56 AM
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Originally Posted by feddup
I think that 195/6015s will probably be the way I'll go. It might be year from now though. I'd prefer not to go narrower as 195 is pretty narrow to start with. 3% sounds perfect as far as lowering the highway revs (for an MT) and not messing up the speedometer readings too much. Also I checked tirerack and there are many excellent relatively inexpensive choices. I'm willing to compromise some handling and acceleration in the name of mileage but don't want to get freaky about it. I think Honda made excellent choices as far as mileage/performance/handling/ride compromises and I don't want to deviate far from them.
Don't be surpised if you find you're using more gas, about 2 mpg less on a corrected mileage basis. The 195/60x15 weighs 19 lb compared to 18 lb and is 24.3" vs 23.4" . It takes more energy to turn those tires even after you correct for 4% more miles traveled than indicated. If your terrain isn't too hilly you may break even.
Good luck.
PS many cars of Fit size run on tires as narrow as 145/82x13
 

Last edited by mahout; Jun 18, 2008 at 11:58 AM.
Old Jun 18, 2008 | 12:21 PM
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All brands?

Originally Posted by mahout
The 195/60x15 weighs 19 lb compared to 18 lb and is 24.3" vs 23.4" .
For all brands?

When I was researching tires before I owned the fit there was some mention of tires specifically designed for low rolling resistance. I can't seem to find any mention of this now. Has anyone heard of tires specifically designed for low rolling resistance tires in "fit" sizes? Yes I'm aware that smaller and narrower tires in general have a lower rolling resistance. I'm willing to deviate in size from stock just not very far.
 
Old Jun 18, 2008 | 02:45 PM
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Originally Posted by feddup
For all brands?

When I was researching tires before I owned the fit there was some mention of tires specifically designed for low rolling resistance. I can't seem to find any mention of this now. Has anyone heard of tires specifically designed for low rolling resistance tires in "fit" sizes? Yes I'm aware that smaller and narrower tires in general have a lower rolling resistance. I'm willing to deviate in size from stock just not very far.
Those are tires for the Prius (non-touring) and recently for Cavaliers, sorry, whatever they're called now. The size is 185/65x15. They may not work very well on a Fit. The diameter is 24.46", a 4.3% increase which is OK but not so good. It weighs but 17 lb which is very good and the recommended rim is 5 to 6.5". You can verify at TireRack.com specs. But the torque it takes to turn it is high. And high torque means gas consumption.
The original tire was the Goodyear Integrity 185/65x15 but that oem may not be the replacement tire offered by tire rack for $65 plus shipping. Wear 460. Discount tire has a $55 tire (wear 400) with free shiopping but you need to contact either to see you're getting the Prius low rolling resistance tire. The LR tires have recently been chosen by GM to raise their mpg numbers by 2 mpg. And you will pay with slower acceleration.
Be sure you avoid the touring Prius tire if you want high mpg. The touring tire is a result of so many Prius owners complained about be outcornered by bicycles. There is no free lunch; the lower the wear rating the better cornering and of course shorter tire life.
Again. good luck.
 

Last edited by mahout; Jun 18, 2008 at 03:30 PM. Reason: my slide rule slipped a cog; makes prior post in error
Old Mar 24, 2015 | 11:14 PM
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I'm rolling on 195/65/15.

I'm the one you see bouncing over cars down the freeway. rpms fixed, but don't be like me. fix 5th gear with a crz 6th gear
 

Last edited by space egg; Mar 24, 2015 at 11:49 PM.
Old Mar 24, 2015 | 11:22 PM
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Originally Posted by space egg
I'm rolling on 195/65/15.

I'm the one you see bouncing over cars down the freeway. rams fixed, but don't be like me. fix 5th gear with a crz 6th gear
surely you don't think a 6th gear will eliiminate your car bouncing down the freeway ?
 
Old Mar 24, 2015 | 11:51 PM
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Originally Posted by mahout
surely you don't think a 6th gear will eliiminate your car bouncing down the freeway ?


meant that big diameter tire fixed my rpm problem, but at a silly price. I think the crz gear is a better choice to reduce the rpms at high speeds.
 
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