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Old 31st December 2007, 16:27   #1
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Default Downsizing tyres

Hi,

What would be the advantages / disadvantages, if any of downsizing the OEM 175/65R14 tyres to 165/80R14 ones?
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Old 31st December 2007, 16:41   #2
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one of a kind

more mileage, speedo err.
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Old 31st December 2007, 17:04   #3
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i guess ride will be softer from the higher profile tyres
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Old 31st December 2007, 17:57   #4
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Hi jkdas,

> one of a kind

Yes, you do get all sorts of people!

> more mileage, speedo err.

I tired those tyres in the front of the City. The speedo error is about 6% (for a 13km distance with OEM, this shows 12.3kms. The trial was to improve the ride. The tyres were better for ride quality, but needs further trials to form a good conclusion.

Unfortunately I could not test it longer as my Marina needed 2 front tyres and these went over to it. Even here it makes a difference to the ride, but yet to drive a longer distance to judge it well.

Even with the speedo difference, has not given better mileage as the up and down trip to Erode was done by my driver, who likes to travel fast.

The last tankful gave 16.93 kpl. My signature is not yet updated.

Wish you a very happy Married life and a very happy, prosperous New Year to both of you.
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Old 31st December 2007, 17:58   #5
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Hi bottle,

> i guess ride will be softer from the higher profile tyres

The intention indeed was that. It did make a difference.
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Old 1st January 2008, 12:25   #6
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The speedo error can be calculated easily. The wheel diameter with the tyre is:

For 175/65R14 = 2x175x.65 + 14x25.4 = 583.1mm

For 165/80R14 = 619.6mm

ie 6.25%

Your road holding will get worse, and the mileage will increase (correct for the longer distance travelled as compared to the indicated distance).
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Old 1st January 2008, 14:13   #7
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Quote:
Originally Posted by trrk View Post
What would be the advantages / disadvantages, if any of downsizing the OEM 175/65R14 tyres to 165/80R14 ones?
Braking will become poorer. Handling will get adversely affected, especially at high speeds, with 80 profile smaller tyres. Grip will come down and could be inadequate under wet conditions. Steering response could get adversely affected at higher speeds. The smaller tyres will have to have an adequate load rating (maybe higher than that of the stock ones?). Ride should improve, but I think the wider tyres will take potholes better than narrow ones.

Not advisable at all to downsize. If you insist on it, I suggest you pick a quality tyre with adequate speed/load rating and preferrably go for wider alloy wheels, if the tyre size permits this. That will compensate to some extent for the lower contact patch of the downsized tyres.
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Old 1st January 2008, 14:31   #8
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you shouldnt go over 2-3% than the original diameter. higher profile will make the ride more comfy. always downsize/upsize keeping the overall diameter correct.
what you have downsized to is very wrong
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Old 1st January 2008, 16:26   #9
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@trrk

Don't reduce the width of the tyre than 175mm, as most OEMs fitted tyres barely manage to keep the car on the road, a narrower replacement could be seriously dangerous.
If you want a higher profile tyre for the sake of ride, then you may go in for 13 inch rims and 175/75 tyres.
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Old 1st January 2008, 21:59   #10
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Reducing rim size has the disadvantage of poorer steering feedback, and of course the cost of new rims. It has the advantage of less rim damage in harsh conditions. Remember that the Zen used to come with 13" rims and this was later changed to 12".
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Old 2nd January 2008, 21:26   #11
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What tyre pressure are you running ?
If the ride is too jumpy, try going down 1-2 PSI and see if its any better.
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Old 2nd January 2008, 23:57   #12
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The right downsize will be 175/70/14 and not 165/80/14

Also if your getting better FE, that can be attributed to the speedo error.
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Old 3rd January 2008, 00:21   #13
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trrk
U can get 185/65-14 if your main objective is to improve the ride quality.

Quote:
Originally Posted by Alfa_Kilo View Post
@trrk

Don't reduce the width of the tyre than 175mm, as most OEMs fitted tyres barely manage to keep the car on the road, a narrower replacement could be seriously dangerous.
If you want a higher profile tyre for the sake of ride, then you may go in for 13 inch rims and 175/75 tyres.
I dont think there's any tyre available in that size.
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Old 3rd January 2008, 17:31   #14
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Hi rks,

> Braking will become poorer. Handling will get adversely affected, especially
> at high speeds, with 80 profile smaller tyres. Grip will come down and could > be inadequate under wet conditions.

Right now they are doing duty in my Marina. It had a long distance run with my driver and he did not find anything amiss. Yesterday I did use it for 60 kms on a route that I take regularly take. Even in the Marina, it does make a difference the way the front tyres react to the road surface. I did try an emergency braking at 60kph and the car tracked true and the braking was as efficient as with the original spec tyres. Wet conditions are yet to be faced. These are going to be the Marina's front tyres as it needed new tyres anyway.

> Steering response could get adversely affected at higher speeds.

The roads that I use are fairly straight. So can't comment. But I really don't feel much difference.

> The smaller tyres will have to have an adequate load rating (maybe higher
> than that of the stock ones?). Ride should improve, but I think the wider
> tyres will take potholes better than narrow ones.

The load rating should be fine as these are the OEM tyres for the Swift. Ride does improve.

> preferrably go for wider alloy wheels, if the tyre size permits this.

What would be the maximum width of alloy wheels that I can go for with the 168/80R14 tyres.
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Old 3rd January 2008, 17:33   #15
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Hi,

> you shouldnt go over 2-3% than the original diameter.

What are the reasons?
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