Changing wheel size, effects?

pobber1

Hi,

I have a 2003 Fiesta (Zetec). The car currently has 15" alloy wheels that are badly buckled. I have had them repaired once before and I am now considering replacing them completely as they buckle far to easily.

I can get a set of standard 14" Fiesta wheels. Can anyone tell me if this would have any undesirable effects on the car? I guess this would have the effect of gearing the car down which may give me worse fuel consumption on the motorway; but the difference may be negligible.

Thanks

Pete67

The 15in wheel will probably have a lower profile tyre than the 14in, so the overall diameter and gearing may be the same.

pobber1

Thanks Pete.

I just remembered I didn't post the tire information, which is clearly important!

Current tire: 195/50 R15
New tire: 175/65 R14

pobber1

Nice calculator here -> http://www.tacomaworld.com/forum/tirecalc.php?tires=195-50r15-175-65r14

Looks like the difference is very small, so it shouldn't be a problem.

jimgoose

According to my calculations your new overall wheel diameter will increase by 7.1 mm, thus giving you very very slightly taller gearing. You'll be grand.

CiniO

With tyres you mentioned there won't be really any difference in gearing, or fuel consumption.

However on 14" car will become much softer. It will be way better to drive on bumpy roads with potholes, but will be bit worse to drive on good flat roads, especially at higher speeds - you will notice car is not turning so nicely.

joujoujou

pobber1 wrote: »

[...]
Current tire: 195/50 R15
New tire: 175/65 R14

Wheel circumference difference = 1.2% so near to nothing.

//source: http://www.voxwheels.com/

Narrow tyres will give less grip, but more mpg.

CiniO

jimgoose wrote: »

Narrow tyres will give less grip, but more mpg.

MPG might increase very slightly, but I don't think it will be noticable.

In mosts cases grip will be the same.

Main difference between higher profile, narrower tyres comparing to wider with lower profile can be felt during fast cornering.
Higher profile tyre will bend more, and might case less grip.

But in straight line - f.e during braking, grip should be very similar.

Esel

joujoujou wrote: »

Narrow tyres will give less grip, but more mpg.

More grip on snow/ice though.

jimgoose

CiniO wrote: »

MPG might increase very slightly, but I don't think it will be noticable.

In mosts cases grip will be the same.

Main difference between higher profile, narrower tyres comparing to wider with lower profile can be felt during fast cornering.
Higher profile tyre will bend more, and might case less grip.

But in straight line - f.e during braking, grip should be very similar.

Hey! I didn't say that!

pobber1

There's only one problem, my sexy Fiesta wont look as cool without the alloys

Thanks for all the comments and info.

joujoujou

Esel wrote: »

More grip on snow/ice though.

Grip on ice? :eek: Only if you have studded tyres. :P

Esel

joujoujou wrote: »

Grip on ice? :eek:

Eh -yeah. Tyres do grip on ice; narrower tyres grip better than wider ones. It's not rocket science.

pobber1

Got the new rims and tires on last night. I drove 70 miles today and there was very little difference in the handling.

The main thing is the whole car doesn't vibrate any more, which is nice.

CiniO

joujoujou wrote: »

Grip on ice? :eek: Only if you have studded tyres. :P

Don't take it personally, but you sound like good representative of typical Irish drivers, as most of them think that driving on ice or snow is nearly impossible.
Funnily there is plenty of places in the world where people do drive on snow and ice without any problems really.

Just my conclusion. once again it has nothing to do with yourself - I just referred to what you said.

joujoujou

CiniO wrote: »

Don't take it personally, but you sound like good representative of typical Irish drivers, as most of them think that driving on ice or snow is nearly impossible.
[...]

LOL!

Trafiłeś jak kulą w płot chłopie. :P

To be clear - I've no problem whatsoever to drive on snow or ice (or both), my only failure in previous post was a kind of unfortunate simplification.

Esel wrote: »

Eh -yeah. Tyres do grip on ice; narrower tyres grip better than wider ones. It's not rocket science.

Nah. Narrower tyres plough better through snow/mud to (more or less) solid surface to get a grip on. No, it's not a rocket science alright, but it's not so simple as it looks either.

http://www.physicsforums.com/showthread.php?t=330790

daRobot

You might as well. Cheaper tyres, better ride. There's no real negatives.

Obviously bigger wheels look better, but on a small runabout it's not really of consequence.