Hey All,

Serious newbie to all this. Bought a '99 RS200Z (215/45/17 tyres) last friday (21st August) so reading as much as I can to learn fast and get up to speed.

I'm a picky bugger and like to know whats happening in and around my car so I went for a cruise with a mate with a hand held Navman GPS unit.

Found out that my car is doing 94kph when its readin 100kph on the speedo. Or 103kph when reading 110kph on the speedo.

Got another friend who is an auto sparky and he said thats standard Toyota (a factory setting to read faster than actual ground speed).

Now that bugs me so over the last couple of days I've been sorting out what tyres would bring my speedo back inline.

Found out 215/55/17s brings it in REALLY well.

Does anyone know of pretty decent tyres that give good mileage?

AJoker_0

I'm a Toyo T1 fan, like a few of us here, but others swear by all sorts...

Toyo are a good bang-for-buck at around the $220 mark. Falkens are just as good but another $50 or so, and then all the usual suspects like Dunlop, Yokohama, Bridgestone etc make a good tyre.

Can't say I've tried a good Chinese tyre yet, but I have out-cornered a few on other cars... :P

Are you serious? Most cars never read dead accurate from the factory let a lone after 10 years. You obviously aren't worried about the aesthetics of your car. 55 series tyres will look ugly & change the handling characteristics. Why not spend the money you're about to waste on new tyres on getting the speedo recalibrate at somewhere like Robinson Instruments. Other options would be to get a GPS or Apexi rev/speed meter if you want accuracy.

According to http://www.rims-n-tires.com/rt_specs.jsp 215/55 is 42mm larger in overall diameter than 215/45. I hope your car isn't lowered.

As i said ... looking for ideas and feedback.

I'm just wanting a good mix of comfort /noise level / life out of the tyres.

Last time I looked into recalibrating a speedo was years ago and it wasn't guaranteed to set the speedo properly anyway. Guess technology has advanced lol.

Are Altezza speedo's electronic or mechanical?

Welcome to the club :D

option 3

buy top quality tyres what ever your choice
toyo, dz101's, yoko's
or whatever, no one regrets buying quality.

If you are seriously worried about the minor spped differential between your speedo and the satnav....... buy a satnav and use that as your speedo :)

Get quality 215/45/17 tyres, and a GPS unit. That way your car will handle like it was intended, and you'll always have accurate speed reading.

or just drive at 105kph , knowing you're still under the limit ;)

i'm pretty sure that legally manufacturers speedos need to read the correct speed or slower, otherwise they could be in big Sh##. they are just playing it safe by making them read 5% slower than required.

altezza speedo is electronic.

I would not go the 215/55/17s route you may regret it

It will change the acceleration and handing characteristics due to the tyre radius not to mention look odd sitting on standard rims

actually, GPS speed is not accurate...its an estimate.

GPS information depends on how often your equipment ask your location.
From there, it calculates how fast your are going but the error goes bigger the faster you go.

I have a pivot speed meter x to sell if that is of interest to you?

Does that remove the 180k speed cut as well?

My mate got the wrong size tyres on his SR20 Primera - one size too big (40 instead of 35 profile or something). Reckoned it made a huge difference - couldn't spin the wheels on dry road, really sluggish, etc. Got the tyre shop to swap them back to the right size and all was well again.

Hey at least you won't get a ticket for creeping over by 5km/h :P If you're using 17x7 and you really must go up a tyre size try 225/45R17 It will only give you a only slightly more profile, a greater contact patch (i.e. grip) and be about 1.5% larger diameter (i.e. slow your speedo 1.5km/h at 100km/h) That would be just about as close as you'd get without going over ;)

This is a useful tool to compare tyres sizes with varied diameter, width, profile. And calculates the % over/under at 100km/h for you too! Click it Tyre Size Calculator

Just punched in the numbers and the ugly 215/55R17 is actually 7% out! Anything more that 3% is not recommended :rolleyes: If you had slightly wider rims like 17x8 then maybe you could use a 235/45R17 which is a very common tyre on Skylines and Bombadores.

If you go 7% larger you'll need to get them certified too, so add another $500 onto the price. Seems pretty expensive for a whole bundle less performance.

Hey,
My speedo is 6.5% out (reads 100kph when doing 93/94kph ground speed) so the 7% larger wheels will bring the ground speed up to match the speedo.

I used the same a website (1010), on Sunday night, to calculate the tyres I'd "need" lol.

So to make sure my theory was right I went and saw 4 different tyre specialists and gave them the basics (speedo vs groundspeed only) and asked if it could be sorted via tyres. They all came up with the same numbers (215/55/17) but had varying ideas on the "right" brand of tyre.

None mentioned anything about certifying, so any info concerning that aspect would be great. Not seeing why it would need to be certified as its bringing the calibrations into alignment, not screwing them up but if it needs certifying ....

IF .... big IF ... i do get the tyres, i'll be mounting the fronts first and checking steering locks / guard clearances etc, before I drive away. If they rub, I ain't getting!

I'm aware that I'm offending the guys who want pure aesthetics and also the guys who want pure performance .... but .... I'm just looking for CONSTRUCTIVE feedback ... Pros vs Cons ... so I can make an informed choice.

I'm coming from $250 Wonder Cars ('88 Corollas, '86 Subaru Leones etc) and wanting to do this right ... not doing it to please other people.

thanks to all who are giving me good info :D

Oh and I am definitely weighing up the pros vs cons of tyres vs GPS units vs recalibrating speedo vs anything else you guys can throw at me lol

Thanks again

I don't think a speedo that reports faster than actual speed is a con.

i agree. If you look at any car magazine road test, you'll find that the speedo idicated speed vs actual speed has nearly all cars reading between 93-98 kph. i think they are just covering their arses from any legal stuff.

Please read:
http://en.wikipedia.org/wiki/Speedometer



And keep in mind the Lexus IS200 was built for the European Market, and because most components are shared with the Altezza, that's probably why your speedo is slightly off.

I say leave it as it, don't fix if it ain't broke

Nah, screw you. We've given you good advice, go ahead and ignore it.

Don't come posting up here when your car looks like rubbish and performs even worse, and some particularly zealous WOF inspector fails you for them being illegal. And you'll probably get scrubbing coz the tires are too big, and a bigger diameter means the tire acts a bigger lever so will bugger your suspension etc up quicker.

HAHAHAHAHAHAHAHA twitchy ain't ya Spoon.

Thanks Nick, Robo and all the others for the advice and info (yes even you Spoon).

I'm gonna leave this subject alone and look into other ways of sorting this out

Later

yellow box

its what all the guys with bikes use when they change the final drive ratio(front or rear sprockets) you can get them for cars as well.

your speedo is always going to be out buy some small percentage and the faster you go the further out it will be just my 2c

Not that twitchy - look at the advice that had been given to you:

You come in here asking for advice, have a bunch of people point out to you that the idea is stupid for a whole host of reasons (not to mention it's illegal without certification) and you post back saying you're still thinking about it.

If you want advice, take it. If you've got your mind made up about something already, don't bother posting and wasting our time finding links, doing calculations, typing posts, etc.

I just noticed something today when I was putting air in my tyres. Had the wheels turned & there's not much clearance between the tyres & guard lining (I couldn't get my fingers in there). 55 series tyres would rub like a bastard.



I think Nick put it best when he said If it ain't broke, don't fix it.

Spoon, as they say: you can lead a horse to water but you can make it drink ;)

Is the guard lining suppose to stick out like that? Think mine's a bit flatter

If you don't want to trust your speedo reading under, then just look at your beloved GPS instead :P
Why bother with changing tyres at all? As they wear out the speedo will be affected again by a few %! lol

OK done some calculating and here is what I got.

215/45/17s:
Rolling Radius - 196.3442cm
Total Diameter - 62.53cm
Sidewall Height - 9.675cm

With the 215/55/17s:
Rolling Radius - 209.8462cm
Total Diameter - 66.83cm
Sidewall Height - 11.825cm

So for every 1KM, the stock size gets 510.2 rotations where the 215/55/17s get only 476.5 rotations.

So the stock tires @ 100KPH Rotate at 510200 rotations and the 55s get 476500 rotations respectively.

That means with the larger tires, you will get approx 6.44% more distance by using the larger tires, which would then put your speedo out again, to be too slow to the actual speed and net you tickets/speed camera fines etc.

Is it really worth it?

Someone feel free to correct me if I'm wrong, my form 6 math (Level 2 NCEA) is quite limited haha