Tyres and gearing...

[CMF_Bishop]

In the strange but true basket, by chance I found some rather rough Pulsar wheels, tyres were in theory all wrong, but I decided to drive it yesterday anyway, reality is the car rides smoother and turns just as well, with the bonus being the gearing feels better.

The first time I drove a Micra, I thought 155/70-13 feels geared all wrong, the car pulls like it should have a larger diameter wheel, with 175/65-14 the car pulls more like most other hatch backs I have driven, I'll probably go a 175/60 though, but really if I was not bothered about the speedo at all, I'd keep running a 175/65 or a 185/60.

 

[CMF_sikK11]

I run 185/60R14 and they are fine with my speedo still accurate.

 

[CMF_1300cc]

i started on 13", then went to 14"....i noticed slight increased in fuel consumption, then went to 16" for approx 2 years, then back to 13"....i can feel its much responsive and fuel economy improved when on 13"....btw my car is NA....

 

[CMF_1300cc]

i started on 13", then went to 14"....i noticed slight increased in fuel consumption, then went to 16" for approx 2 years, then back to 13"....i can feel its much responsive and fuel economy improved when on 13"....btw my car is NA....

 

[CMF_chargeR]

13s for life! The car is slow as hell anyway without additional rotating mass, and taller gearing isn't likely to improve matters. Personal preference I guess .

sikK11 WROTE:

"I run 185/60R14 and they are fine with my speedo still accurate.

Your speedometer might be accurate but it is probably because the larger diameter tyres you are using have compensated for the OEM speedo reading high on OEM sized tyres .

 

[CMF_sikK11]

Its kinda funny when people think that tyre size is all that important. Really its like 20mm or something in difference. Be the same as having a full tank of fuel to a 1/4 tank. Really its not that big of a deal.

 

[CMF_Bishop]

Rotating mass etc and so on, also should read as bigger wheels make the car less twitchy, the other bonus I have found.

Drove it again today, I recon the clutch is working a shade harder with bigger wheels, but I am just tempted to slap on 185/60 now, the are a dirt cheap size.

 

[CMF_sikK11]

But your alloys would almost be lighter then smaller steelies. Plus lower profile tyre as well equals less weight then higher profile tyre.

 

[CMF_Jon (2)]

http://www.miata.net/garage/tirecalc.html

Play with that guys,

Legally in most states of Australia you cant go more than +/- 15mm in rolling diameter on your tyres from standard.

To the OP, 175/65/14 (106.6 km/h @ 100km/h) is too large and so is 175/60/14 (103.4 km/h @ 100km/h)

Sikk11: 185/60/14 are 30.4mm larger in diameter than standard. Your speedo at 100km/h would actually be 105.6km/h

 

[CMF_sikK11]

No my speedo at 100 is dead on 100.9 i have had it checked as i was fighting a speeding fine. Guess what i had to pay the fine cos my speedo was spot on with the tyres on.

 

[CMF_frank2]

sikK11 WROTE:

"I run 185/60R14 and they are fine with my speedo still accurate.

those would be ok for cruising/motorway runs but they must kill your acceleration and urban fuel milage :O
165/60/14,s ftw (stock fittings to the facelift k11)

frank

 

[CMF_Bishop]

sikK11 WROTE:

"But your alloys would almost be lighter then smaller steelies. Plus lower profile tyre as well equals less weight then higher profile tyre.

No, people often think an aloy is going to weigh less, often they don't, and just because something is low profile, it's often not as low profile as what came off the car, a 155/70 is actually quite low profile, cause it's 70% of only 155, where as say 60% of a 185 is more sidewall, tyre math don't lie, hence why I said my car rides better with what is on it now, 155/70 suck on the bumpy roads I live on.
Edit: Oh and much of a tyres weight is in it's width, sucks but it's true, wider tyres weigh more in general.

Jon WROTE:

"<A href="http://www.miata.net/garage/tirecalc.html" title="http://www.miata.net/garage/tirecalc.html" target="_blank">http://www.miata.net/garage/tirecalc.html</A><BR>
<BR>
Play with that guys,<BR>
<BR>
Legally in most states of Australia you cant go more than +/- 15mm in rolling diameter on your tyres from standard.<BR>
<BR>
To the OP, 175/65/14 (106.6 km/h @ 100km/h) is too large and so is 175/60/14 (103.4 km/h @ 100km/h)<BR>
<BR>
Sikk11: 185/60/14 are 30.4mm larger in diameter than standard. Your speedo at 100km/h would actually be 105.6km/h

You can legally build a car with more speedo error than what is legal to upsize in australia I think (although they may have updated that reg in the late 90's), been that way a long time, go figure.

Believe it or not tyres from different makers also vary a 'huge' amount in rolling diameter, in fact some rated high fuel economy tyres cheat by undersizing their product, over sized tyres are wrong, right up until you realize it matters very little.

And Frank, surprisingly my Micra is not much slower at all, in fact it's gets off the line faster, so a little of one more of another, and the milage bump has been quite small so far.