14" VS 15"

[Nool]

Hi guys
I'm thinking seriously of upgrading from the horrible standard 14" vti steelies to 15". Doing it for looks - extra performance will be a bonus, but I don't want to stuff up the ride or the geometry. I'm considering something like 15 X 6.5 with +35 offset.

1) The Honda dealer says I MUST stay on original 14" Honda spec wheels or I'll do all sorts of damage to the steering and front end. Anyone heard of this happening?
2) Any experience on how 15" (or 16") affect the ride compared to 14"?
3) Any experience on how the wider rims affect the feel of the steering and especially the tracking?

Any advice greatly appreciated. I don't want to stuff up what is a great little car.

[vividjazz]

The VTiS comes standard from Honda with 15" wheels so for a dealer to say there is some adverse effect from changing from one factory standard size to another factory standard size on the same vehicle pretty much sums up what the dealer knows.

The factory standard sizes on the Australian models are 185 / 55 R15 82V for the VTiS &
175 / 65 R14 82T for Gli & VTi.

With any wheel change you want to maintain rolling diameter so as not to throw out the speedo and odometer. This means if you go wider you go lower profile. If you go up in wheel size you go down in profile. This site www.carbibles.com/tyre_bible.html explains it very well and has a calculator to compensate for changes.

Lower profile tyres mean less flex in the tyre wall which translate to an improvement in cornering but also a harder ride.

Wheel weight drasticly effects fuel economy on a light vehicle. Jazzes with 17" wheels get poor fuel economy compared to 14" and the weight also means that they accelerate slower particularly from a standing start.

Similarly wider stickier tyres improve handling but increase rolling resistance reducing fuel economy and can result in slower acceleration if the increase in resistance outweighs the increase in traction.

From experience with different cars the choice in tyres is more limited for 16" and a bit more expensive than for either 15" or 17" tyres.

As for doing damage to the steering and front end I sure hope you don't take your car to this dealer for servicing as they might put water in the engine thinking its the radiator as they sound like they don't know much about cars and even less about Hondas.

I'll leave it to someone else to talk about offsets, rim sizes to match tyre width and the impact on a vehicle though the link above also talks a bit about it.

Some people only care about looks and don't think about any of these things. There are Jazzes with even 18" & 19" rims shoehorned onto them. Wouldn't want to be paying for those licorice strap tyres or driving on the goat tracks they call roads in Sydney with them.

Personally I'm happy with my 14" Honda Enki mags even with the cheescutter tyres. When the tyres wear out I'll go a bit wider with the corresponding slight drop in profile to compensate to maintain the correct diameter.

[wai164]

I think you can go with 195/50 R15. Cause the actually size of the wheel is smaller than the normal standard 14" wheel.

[vividjazz]

You do not want more than a 2% difference in diameter between changes.

To maintain this then the following sizes are all equivalent to each other:
175/65R14
185/60R14
185/55R15
195/50R15
195/45R16
195/40R17
195/35R18

I don't know whether 205 width will fit in the caverty ie. the next width up from 195s. Has anyone tried?

[dreams]

depends on the offset.

[SmellyTofu]

Having been driving in today's wet weather, the cheese cutter tyres are perfect for going through the wet weather. No aquaplanning at all which is surprising for a car that's so light. I'll go 15" if and when these cheese cutters go but I'd be happy with a more agressive tyre pattern in the standard 14" size.

[Nool]

Thanx everyone for the feedback - esp vividjazz. Apparently Honda put out a service bulletin saying that vti's must stick with 14" as bigger wheels will cause damage - I find this incredible as we all know the vtis has 15's - but this is apparently a release from Honda. Is there any difference to the vtis front end or steering box? If not, then they must be talking total crap.

Tyre diameter is pretty easy to get right. Here's a site with a great calculator to compare tyre sizes: www.miata.net/garage/tirecalc.html

Talking about wheel geometry, not clearance: I'm curious about optimum wheel offset with wider rims. For example, when you put on wider rims, do you aim for an offset which keeps the CENTRE of the rim in the same place as the standard rim? In doing so you are making the rim wider in equal directions relative to the hub. Or do you aim to keep the OUTSIDE of the rim in the same place as standard. I ask this cause I'd imagine that wide rims can stuff up the steering and introduce problems like bump steer.

Also has anyone had experience going from the 14" chessecutter to 15" and fatter tyres? And how did it affect things like ride, noise and steering. This is all important stuff if you you want to go outside factory specs and not undo the work of the Honda engineers. My experience with my old BMW was that even fitting a different brand of tyre could affect the way the car tracked and steered. So how much more damage can you do by fitting up rims that simply fit and look good.

[spoom]

that dealer is and idiot, i bet he wont hesitate selling you a set of 15" alloys from honda

[Nool]

More about wheel geometry: I've been doing some research of my own on the subject. Spoke to a friend who's had some experience setting up race cars. He reckons that offset on a road car is not very important. You shouldn't stuff up your steering or handling if you deviate from the original offset. Tyre width (contact patch size) and tyre profile will cause more of a change than offset. Of course you still need to consider offset for clearance. This all seems to fit in with what I've read on this & other forums.

[swat]

18 is as good as 14 or 15 unless if u hit crub then u will damage the car touch wood........

[vividjazz]

swat said:

18 is as good as 14 or 15 unless if u hit crub then u will damage the car touch wood........

Yeah only difference is you'd want a kidney belt with every set of 18" wheels on the Jazz and not want to eat anything prior getting into the car because the ride would be so bone jarringly hard on Sydney roads (most roads elsewhere in Australia aren't alot better).

That kind of jarring has to do serious suspension damage in a very short time and with such little rubber to protect the rim the 1st pot hole (available in a variety of sizes from moon crater to welcome to mainland China) will cause serious wheel damage.

The enormous loss in performance and fuel economy sort of defeat the purpose of the car but if looks are all that count and you don't mind driving 2km/hr over every speed hump placed every 100 meters down most suburban streets then why not go 19s and get a 2nd morgage to pay for the special order tyres.

[Nool]

vividjazz, how can you be so conservative? My favourite website for tyre size calculations www.miata.net/garage/tirecalc.html tells me that I can fit 20" whilst maintaining my speedo accuracy. Yes for those who say too much is never engough, dreams can come true - who would be seen dead with a set of 18's when you fit a set of 145/12R20's to your Honda Jazz.

I've made my choice. Actually my bank balance made the choice for me, but I'm more than happy with it's decision. I'm sticking with 14's. When I need to go for new tyres, it'll be 185/65R14 which give 10mm increase in diameter, 7mm increase in radius (I'll be very surprised if there's any clearance issues) and a 2.2% decrease in speedo reading which will actually make the speedo more accurate as it currently reads 100km/hr at an actual 96.