Kia Qouris/K900 V6 2013-2018 rear seat, passenger and steering wheel Vibration Fix! - Kia K900 Forum
 
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post #1 of 9 Old 05-29-2019, 04:23 AM Thread Starter
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Default Kia Qouris/K900 V6 2013-2018 rear seat, passenger and steering wheel Vibration Fix!

Good afternoon ladies and gents, I m a proud first owner of a 2016 Kia Qouris 3.8l with 120k km on it and all the way from Dubai. Hope everyone is doing well and please forgive me on errors since this is my first post.

I would like to inform you V6 owners that through extensive research, I have found the optimal solution for those of you who complained about excessive vibrations and not knowing the proper fix.

Having my Qoursy for quite a while. I have been noticing uneven tread wear all around the tires in the long term, slightly heavy steering and audible steering whine. Along thinking the car is a big too heavy and underperforming on the highway.

These vibration and excessive tread wear issues never got resolved by the Kia maintenance center.

The good part:

It turns out that the OEM rims on the V6 model are 18x7.5, while the OEM tires are 245/50r/18

The maximum allowable tire width on a 7.5inch rim is 235 and ideal width from 215-225. So it was most probably the 245's caused the excessive vibration and also the rubber bulging out of the rims.

My recommendation based on standard measurement would be to install 235/50/R18's with a load index of 101
And believe me it has made a world of a difference after Installing them with balancing and alingment. Suddenly on the road I instantly felt Sharper handling, better grip due to stiffer sidewall, faster acceleration and braking along better gas mileage. The car lowered by 0.3inches which makes it feel very stable, and say goodbye to the floaty bouncy and annoying suspension feel.

It turns out the 235/50/r18's are the tire size used on many mid to large size luxury sedans just like the Lexus LS and older models of Mercedes S class.

Thank me later or by the time you install them 235's!
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post #2 of 9 Old 05-29-2019, 10:06 PM
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Very interesting! I will look and see what I have. It's a very weird error for the factory to make, though--wonder how it happened.

Also, welcome to the board, SultanZarooni!

2016 V8 VIP+, black with white interior
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post #3 of 9 Old 05-30-2019, 03:34 AM Thread Starter
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Thank you kind sir.
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post #4 of 9 Old 05-30-2019, 09:35 PM
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Quote:
Originally Posted by SultanZarooni View Post
Good afternoon ladies and gents, I m a proud first owner of a 2016 Kia Qouris 3.8l with 120k km on it and all the way from Dubai. Hope everyone is doing well and please forgive me on errors since this is my first post.

I would like to inform you V6 owners that through extensive research, I have found the optimal solution for those of you who complained about excessive vibrations and not knowing the proper fix.

Having my Qoursy for quite a while. I have been noticing uneven tread wear all around the tires in the long term, slightly heavy steering and audible steering whine. Along thinking the car is a big too heavy and underperforming on the highway.

These vibration and excessive tread wear issues never got resolved by the Kia maintenance center.

The good part:

It turns out that the OEM rims on the V6 model are 18x7.5, while the OEM tires are 245/50r/18

The maximum allowable tire width on a 7.5inch rim is 235 and ideal width from 215-225. So it was most probably the 245's caused the excessive vibration and also the rubber bulging out of the rims.

My recommendation based on standard measurement would be to install 235/50/R18's with a load index of 101
And believe me it has made a world of a difference after Installing them with balancing and alingment. Suddenly on the road I instantly felt Sharper handling, better grip due to stiffer sidewall, faster acceleration and braking along better gas mileage. The car lowered by 0.3inches which makes it feel very stable, and say goodbye to the floaty bouncy and annoying suspension feel.

It turns out the 235/50/r18's are the tire size used on many mid to large size luxury sedans just like the Lexus LS and older models of Mercedes S class.

Thank me later or by the time you install them 235's!
Great information!!! I believe on my 2015 K900 the tires are staggered:

245/45R19 = 27.7x9.6R19
275/40R19 = 27.7x10.8R19

So I wonder what would be a better choice for us 2015 owners.
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post #5 of 9 Old 05-31-2019, 04:54 AM Thread Starter
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Good question,

The 5 litre V8 comes with the staggered setup

With rim size:
Fronts 19x7.5
Rears 19x8.5

The fair solution would be

Fronts 235/50/R19
Rears 265/45/R19

Hope this helps!


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post #6 of 9 Old 05-31-2019, 10:26 AM
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Love it - thank you!
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post #7 of 9 Old 05-31-2019, 01:13 PM
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Welcome to the forum SultanZarooni! Glad to have you here!

While the charts you refer to are a good rule of thumb, there is more to the story. Because tires have flexible sidewalls, a single tire size will fit on a variety of rim widths. Each tire manufacturer specifies the particular tire model's rim width range, which identifies the narrowest to the widest rim widths upon which the tire is designed to be mounted. These rim width ranges vary depending on the manufacturer and the specific tire model. In addition, each tire model has a measured rim width (the width of the rim at which the tire is the specified width. The width of the rim will influence the width of the tire. A tire mounted on a narrow rim would be "narrower" than if the same size tire was mounted on a wide rim.

The US spec 5.0 K900 has 8x19 front, 9x19 rear wheels, which are within the rim width range for the OEM Hankook Optimo H426 tires, and are also the measured rim widths for that tire. I checked the rim width range for the 245/50R18 Hankook Optimos that came on the V6 models, and the rim width specified for that tire is 7" to 8.5", with a measured rim width of 7.5"

I checked the rim width ranges for a half a dozen tire models popular here in the USA, including tires from Michelin, Continental, and Pirelli. For the 245/50R18 tires, they all fell into a recommended rim width range of 7" to 8.5" and the 245/45R19 sizes all fell into a recommended width range of 7.5" to 9". The 275/40R19 tires used on the rear of the V8 models were a little more variable, but the 9" width rims were within the recommended rim width range specs for all of the tires I checked.

The Hankook Optimo 426H tires are frankly terrible, and many people have complained of vibration and poor ride from them. I suspect the reason you no longer have vibration issues and better handling is more due to the fact that you replaced worn out, poor quality tires with superior ones than it is to the change in size. Also be aware that going to a smaller width while keeping the aspect ratio (the "50" in 235/50R18) the same, the tire now has a smaller overall diameter, which will throw off the accuracy of your speedometer. It will now indicate you are going slightly faster than you really are.
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post #8 of 9 Old 05-31-2019, 06:13 PM Thread Starter
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I agree with you, mines came with the Hankook H426's and were very terrible. Within my first 5k km I have asked a couple of staff back at the service center and they claimed that the first batch of them on the 2016 models were defective due to bad storage. (Tires were stacked vertically in the warehouses for a long period of time).

I then replaced them emediatly with Firestone touring tires of the same size which eliminated vibration but kept coming back just before every tire rotation at 8km of it's last 2k km. Then went for Dunlop Max 50's and same story.

I was consistent with regular maintenance invervals of rotation, balancing and alingment

Three sets so far haven't lasted 40k km each, along severly uneven tread wear from premature alingment issues (based on pic). I feel this has all to do with the excessive sidewall buldge. And tires that exceed allowable width will cause overheating, vibrations, suspension damage in the long term along premature misalgment.
I have researched. other similar rim sizes on different cars and turned out to be around the allowable tire width chart.

The roads here are categorised as A class and have had tires living up to 120k mark on my lexus LS.

The slightly smaller diameter tires is acceptable at 1.1% or 0.3inches from the OEM as long as it's not more than 3% and will give me an advantage on radars if over speeding though a bonus, and the speedometer difference I have calculated is around 0.3mph slower at 60mph and 0.9mph slower at 80mph.

Thanks for the feedback!
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post #9 of 9 Old 05-31-2019, 06:18 PM Thread Starter
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It is a sort of a snowball effect where vibrations keep getting worse and causes more damage, the longer you put miles on it.

Exssesivly wider tires would sit fully flat along its edges which they are not designed to and causing these uneven tread wear patterns. And since the car weighs up to 4.5k pounds, it's best to opt for high load ratings since the 245's are at 97-100 which is barely sufficient to support and deform while parked for several days.
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Last edited by SultanZarooni; 05-31-2019 at 06:26 PM.
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