TIRE questions,sizes, mounting,pressures ANY tire questions

#1 (**permalink**) 05-04-2005, 04:44 PM

Tires have specs for section width, rim width, and rim width range.
(Plus lots of other stuff).

Looking at a Pirelli PZero Nero 225/45-WR17, it lists a rim width of
7.5" and a rim width range of 7-9".

If this wide tire were mounted on a 17x7" wheel, it would seem that
the sidewalls would protrude a bit on either side, offering the rim
some small level of protection against curb scrubbing.

That would seem to be a good thing, but what I need to figure out is
if there are any handling / ride considerations for using a 7" rim
versus a 9" rim.

Any implications for sidewall flexing / rolling resistance / contact
patch / "spring" effect on a tire as a car enters a corner?

Thanks in advance.

-- CL.

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| Charles Lasitter | Mailing / Shipping |
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gsiy2 · #2 (**permalink**) 10-30-2005, 10:00 AM

I recently changed the tires of my 1.5 Jazz/Fit Vti CVT to 195/60/15, will this compromise anything in the car? Can the Jazz/Fit accomodate 205/60/15 tires?

vividjazz · #3 (**permalink**) 10-30-2005, 05:25 PM

Your speedo and odometer will be thrown out as the rolling diameter of your wheels with tyres is greater. As you go wider you need to reduce the tyres profile to maintain the same rolling diameter.

Lower profile tyres give a harder/harsher ride. Heavier wheels with stickier rubber will reduce the vehicles fuel economy. The vehicle will also be slower.

http://www.carbibles.com/tyre_bible.html - This site will help you calculate the correct sized tyres needed to maintain an accurate speedo.

Comes down to better looks traded off against everything else.

gsiy2 · #4 (**permalink**) 10-30-2005, 11:29 PM

Thank you vividjazz, the carbibles site was very helpful. According to the site and the bridgestone website, the maximum size of tires that i can put on the stock 15 inchers is 205/50/15. Will the ride of the 205/50/15 be less harsher than the ride of the stock 185/55/15? The ride of the 195/60/15 is wonderful but as you said it sacrifices speed and fuel economy then that defeats the usefulness of the jazz. I am thinking of switching to 205/50/15 as recommended by carbibles and bridgestone, however, before I do so, I would like to hear your opinion on the ride of the 205/50/15 compared to the stock 185/55/15.

vividjazz · #5 (**permalink**) 10-31-2005, 12:21 AM

The wider tyre is going to improve cornering and braking quite noticably but will result in more resistance as you have a larger contact patch on the road. ie. economy, acceleration and speed will suffer a bit.

The lower the profile the harsher the ride as you have less rubber on the sidewall of the tyre to absorb bumps but the trade off is less flex in the sidewall and hence better grip particularly when cornering. I also used to find with bad roads it was very easy to damage the rims with ultra low profile tyres (Sparco Racing wheels weren't made for Sydney roads).

The wheels rim size and offset is also going to impact how wide you can go as the rim has to safely support the tyre width and the tyre shouldn't protrude beyond the wheel arches.

Alot of people are happy with the tradeoffs of going even to 16" (or even larger) with really wide tyres but personally I intentionally chose only 14" Honda (Enki) alloy wheels to maximise performance. I'm considering going the next size wider in tyres when these wear out but not up in wheels or any wider than just an extra 10 wider in tyres.

Guys with 17"s report very noticably worse fuel economy and sluggish takeoff. The car isn't really designed for them but some people are only concerned about looks at all costs.

Tyre compounds will also effect performance. As wonderful as Silica is for grip particularly in the wet it means more resistance. Its interesting to look at the tyres chosen for the hybrid cars as these really maximise a cars economy due to absolute minimum resistance.

vtec · #6 (**permalink**) 10-31-2005, 03:51 AM

gsiy2,
I have just changed my tyres also, from 175x65x14 to 195x60x14. I have noticed a massive increase in cornering ability, but the economy seems to have dropped slightly. I had got up to 18km/l, but now get 16.5-17.7 km/l. Still really good, and I think it is worth it for the added cornering safety.

vividjazz · #7 (**permalink**) 10-31-2005, 04:32 AM

Quote:

Originally Posted by vtec

gsiy2,
I have just changed my tyres also, from 175x65x14 to 195x60x14. I have noticed a massive increase in cornering ability, but the economy seems to have dropped slightly. I had got up to 18km/l, but now get 16.5-17.7 km/l. Still really good, and I think it is worth it for the added cornering safety.

I could certainly make peace with that trade off in economy for cornering. Thanks for the figures.

How many kms did you get out of the factory tyres?

vtec · #8 (**permalink**) 10-31-2005, 03:02 PM

Hi,
I got 100km, as I have just imported it!
It didnt have the factory tyres on it, it had horrible yokohama aspecs, which were really hard. It was sliding at 50km around corners. Now I do 90 around the same corners.
What economy do you get?

vividjazz · #9 (**permalink**) 10-31-2005, 05:26 PM

Quote:

Originally Posted by vtec

Hi,
I got 100km, as I have just imported it!
It didnt have the factory tyres on it, it had horrible yokohama aspecs, which were really hard. It was sliding at 50km around corners. Now I do 90 around the same corners.
What economy do you get?

Yeah mine has those Yoki ASpecs on it now. They work alright with the correct amount of air in them (came very underinflated from the Australian Honda dealer).

Front and rear XForce strut bars ($A100 later) and the vehicle handles like a go kart. I imagine it would be even better with better tyres.

Get around 7L/100KM around city and alot better on the open road 5.4L or less/100KM. Have to take off fairly hard in Sydney traffic and I certainly don't feather the accelerator. Economy didn't pick up until got over 10-11,000km.

If you've got a Jap spec Fit make sure your running premium fuel in it as 95RON is what they are tuned for min in Japan. They detune the car for other markets. You can really feel the difference with the CVT with the better grade fuel.

vtec · #10 (**permalink**) 10-31-2005, 05:40 PM

Hi,
Thanks for info on the fuel, I was wondering about that. The brochure for the 1.5 jazz here says to use 91ron.
Yep, I've driven in Sydney, I know why you have to take off fast!
I guess I can't complain about my economy. Got 6.09 l/100km this morning. Thats driving up a hill to 550m and back down the other side to sea level.
Do you think it will run ok on 91? I'm not worried about performance. I use my other car for that!
(2002 RX7 Type RS)

Cheers

vividjazz · #11 (**permalink**) 10-31-2005, 06:55 PM

They don't even sell 91 RON fuel in Japan anymore. Shell in Australia is also fazing it out with regular unleaded going to 95 and Optimax at 98.

I don't think its going to be catostrophic if you run 91 in yours but if it splutters, pings or does anything else unusual just fill up with 95+ the next time.

I like the increased power the different density, higher octane fuel provides. People gain less power with pod air filters and exhaust systems which cost alot more than a few cents a litre. I haven't got an RS RX7 in the garage though but do have a VFR800 bike.

Gazzz · #12 (**permalink**) 11-15-2005, 08:22 AM

my lancer has 195/50/15 atm. really impressed with the cornering so they'll be getting transferred to the jazz. Provided they'll fit! they should tho...

vividjazz · #13 (**permalink**) 11-15-2005, 07:35 PM

Quote:

Originally Posted by Gazzz

my lancer has 195/50/15 atm. really impressed with the cornering so they'll be getting transferred to the jazz. Provided they'll fit! they should tho...

Very close match. They'll only throw your speedo, mileage and fuel economy figures out by 1.5%. Stock tyres are 185/55/15 or 175/65/14.

Only other issues are offset and stud pattern. Honda's are only 4 stud.

Gazzz · #14 (**permalink**) 11-15-2005, 07:51 PM

4 stud??!

OH NO!

kokonchi · #15 (**permalink**) 12-08-2005, 08:36 AM

Quote:

Originally Posted by Gazzz

my lancer has 195/50/15 atm. really impressed with the cornering so they'll be getting transferred to the jazz. Provided they'll fit! they should tho...

My jazz have a 205/45/16...love its cornering and grip..FC still around 16+/100km..

epin · #16 (**permalink**) 01-20-2006, 09:56 AM

Quote:

Originally Posted by vividjazz

Very close match. They'll only throw your speedo, mileage and fuel economy figures out by 1.5%. Stock tyres are 185/55/15 or 175/65/14.

Only other issues are offset and stud pattern. Honda's are only 4 stud.

My Fit now is 195/50 R16. before that, it was 205/45 R16.
I Hv tested my car from 0-100km/h. with 205/45 needs 11.9 sec. with 195/50 needs 10,2 sec. pretty good with the small-one.

Can u Explain 2 my why is this happend?

vividjazz · #17 (**permalink**) 01-20-2006, 06:18 PM

Speedo is inaccurate unless you maintain the same total diameter (wheel + tyre).

_karu_ · #18 (**permalink**) 01-21-2006, 07:08 PM

if only i can move my 2004 Civic EX's alloy wheel with 195/60/15 to the new Fit..