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Does increase in Rim size really reduce FC DRASTICALLY?


Woes
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1st Gear

Just want to pose the above question to all the drivers out there, feedback is appreciated.

 

Before I start, let me give some info on my current car. Driving a SUV now. Stock wheels were 235/65 R17.

 

A few months back, the tyres were getting bald and needs a change. I have long been a fan of huge chrome deepdish rims. Since it needed a tyre change, I reckon I will go for the full package.

 

 

After asking around, most of my friends or shop owners will say that 'your FC is going to be super jialat, furthermore with such big rims'.

 

I thought, what the heck, it is not everytime I get to have a car to be able to be fitted with big rims. I went ahead and got a R22 rims with 265/35. The overall diameter is still withn 1% of my stock wheels. I must say, I did not regret my decision. Full chrome with a 3" lips.

 

Before changing wheels, FC was approx 7.8 - 8 km / L.

 

 

After changing rims, I monitored for 2 months and most of the time, it is quite constant.

 

Many who have seen my rims were WOW, your FC must be crazy. I just told them it is ok, still acceptable to me.

 

 

Question to the bros and sis here, be it either you have experience with rims upsizing or you hearsay from others, what do you think my FC is currently.

 

I did not purposely change my driving style before or after, style and attitude still remained the same.

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If your overall diameter barely changed within 1%, your FC should not have much change... you should not even notice a change.

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(edited)

If your overall diameter barely changed within 1%, your FC should not have much change... you should not even notice a change.

you must be a car noobie

 

so when you hear people say FC change a lot after changing to larger rims, you also think their overall diameter also change a lot?????

Edited by comegetme
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1st Gear

One thing to highlight, although the overall diameter is the same, the total weight definitely is much heavier. I know because I changed it myself although I don't know the exact weight.

 

 

My point here is not to say the FC won't increase but the opinions by all before I decide to change is, it is going to DRASTICALLY increase FC especially the rims I'm getting is 5 size bigger.

 

When I ask why, most of them say they hear it from somebody or somewhere. They themselves have no experience...

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forget about the look, change to the best tyres will do, that give u immediate performance n driving satisfaction

rim, i ever saw many bling bling rims cars, always so careful running over hump, lobang, curbs. really feel sorry for them.

some more heard from my friend, buy many types of rim polishing stuff, always cleaning it after the ride.

one day i saw him kpkb, he said need to change disc break plates bcos everyday, go home straight wash tyres n rims, the discbrakes still hot n the water cooling effect cause immediate contraction to the plate damaging it in the long run.

 

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1st Gear

If your overall diameter barely changed within 1%, your FC should not have much change... you should not even notice a change.

 

I tried to keep within my stock diameter because I'm afraid of the rubbing issues etc. But width had to increase because my rims are 10", in the end I had to decrease my offset else I might be rubbing the inner walls.

 

 

Initially I wanted a 24" rim but after calculation, the profile will be too thin for my liking. There may be some who might say 'I had even lower profile' but this is a SUV, not a sporty car so to me, this profile is acceptable to me.

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TBH my FC did suffer a bit, when I upsized from 17" to 18". on 17" is around 9km/l, on 18" is around 8+km/l.

 

But the car certainly feel more planted to the ground, and that is more important for me.

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Turbocharged
(edited)

2 months is not the factor. How many KM you drove on the new set of wheels?

 

the first 1000 to 2000km you will not feel much difference, but once your tyres are seasoned at mileage of around 7000km onwards you will feel the full effects of whether the new set of wheels will actually increase the FC or not.

Edited by Pocus
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probably the road contact surface has been reduced instead of increased after change.

 

from 65 to 35 profile is very drastic change.

 

make sure your insurance covered.

 

 

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1st Gear

forget about the look, change to the best tyres will do, that give u immediate performance n driving satisfaction

rim, i ever saw many bling bling rims cars, always so careful running over hump, lobang, curbs. really feel sorry for them.

some more heard from my friend, buy many types of rim polishing stuff, always cleaning it after the ride.

one day i saw him kpkb, he said need to change disc break plates bcos everyday, go home straight wash tyres n rims, the discbrakes still hot n the water cooling effect cause immediate contraction to the plate damaging it in the long run.

 

 

yo bro, I'm not driving a cayenne, x6 nor q7. There's no performance worth mentioning about mine.

 

Bling bling rims are just one of my pet peeves. In the past, I did mess around with the performance like upgrading turbos, brakes, intercoolers and even engines but after a while, I get sick and tired of these.

 

With a performance car, big rims are a no no so I can only do it with my SUV now.

 

As for potholes, humps, I do not deliberately slow down, just continue to whack as usual. That's what SUVs are for, right.

 

As for the cleaning, I only wash it down with clean water once a week. Sometimes I don't even wipe it dry and it still blings.

:D haha, my car definitely feels super planted which is a good thing because this is also a family car.

 

 

TBH my FC did suffer a bit, when I upsized from 17" to 18". on 17" is around 9km/l, on 18" is around 8+km/l.

 

But the car certainly feel more planted to the ground, and that is more important for me.

 

2 months is not the factor. How many KM you drove on the new set of wheels?

 

the first 1000 to 2000km you will not feel much difference, but once your tyres are seasoned at mileage of around 7000km onwards you will feel the full effects of whether the new set of wheels will actually increase the FC or not.

 

 

This is good info to me. Not sure what is the mileage but I will take note when I reach the 7k mark, thanks.

probably the road contact surface has been reduced instead of increased after change.

 

from 65 to 35 profile is very drastic change.

 

make sure your insurance covered.

 

 

 

 

I'm sorry, why will the road contact decrease? I went from 235 to 265, shouldn't it increase?

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Turbocharged
(edited)

 

This is good info to me. Not sure what is the mileage but I will take note when I reach the 7k mark, thanks.

 

Not only that. The weight matters, how heavy is your stock rims and how heavy is your current one? Maybe you gotten yourself some light-weight forged rims that compensate the wider tyre width.

 

It's all physics man, God won't give you unique exceptions. Wider tyre conditions will definately increase FC. There must be some mitigating factors that skew the FC's reading to the unexpected. The question is will this FC last?

Edited by Pocus
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I'm sorry, why will the road contact decrease? I went from 235 to 265, shouldn't it increase?

 

 

A normal tyre contact patch is normally around the size of square shape. However, as you increased the width, the tyre shape becomes more rectangular. Hence, total contact surface may decrease (if overdone).

 

This could mean when you are driving off on a straight road, there's increased resistance, but during cornering, your tyres are in "twisted" position = less grip (if overdone).

 

Most car maker's recommendation for rim upgrade is not 2 inch higher (i.e. from 14" to 16", but not 17" and higher) than the stock recommendation with corresponding correct change in profile to keep rolling circumstance more or less same as stock size.

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I upgraded from 195/65/15 to 215/45/17" on my ride last 5 months / about 8k km. Friends told me i will surely suffer 50 km per full tank but in fact FC maintains about 10-11 km/l. Often, people just exaggerate too much on the impact.

 

Just enjoy your bling2 wheels and no need to care much on FC ar..

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I don't think at 235mm width to 265mm width with a big SUV and powerful engine it would make any significant difference but on small engine cars and going from 15" 165mm to maybe 17" 195mm would.

 

The biggest contributing factor to FC is always weight. When rims are upsized and wheels are widened the weight of the wheel increases. Unsprung weight is detrimental to FC. But if your vehicle is already 1,800kg in weight, it's a small percentage of change -- you're not gonna feel anything.

 

Don't believe me? Just do a weight vs FC comparison. Here's my observations (in general), even with varying engine sizes

 

1 to 1.2 tonnes = 11-14 km/1

1.2 to 1.4 tonnes = 9-12 km/l

1.4 to 1.8 tonnes = 8-10 km/l

 

The lighter your car, the more you will be affected by a wheel upsize.

 

But wheel upsize apart from asthetics, a lot of people don't understand how a wrong offset would completely mess up their suspension geometry. I always stick to original wheels (even if I upsize).

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You all get bad FC because you all change to those heavy cheapo rims.. Every extra inch in diameter should be accomodated by 10mm width increase in tire width. But do note that the extra width will add to the FC. But better cornering that's for sure

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Neutral Newbie
(edited)

i changed the stock 18"rims with run flat tyres to 20"rims with michelin tyres. the FC has improved in my case. I'm driving a SUV.

Edited by Volvolite
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Supersonic

Ask the cyclists why they want thin thin wheel and not fat fat wheel ?

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