Went to Bob Jane's yesterday to get new tyres fitted. Didn't want 225/50R17 again as they
are on the tad smaller side and need to get XL series which costs more, $245 for a
Hankook 422.

Ended up getting 225/55R17 Maxxis MA-Z4S at $210 each. 225/55R17's are now the
standard fitment to GMs so they are cheaper.

Anyhow, when talking to the owner through my options, he suggested 235/45R17 however
these are too small. I also said that they are not legal on 7" wide wheels, however, he said
they are. One of his crew as a TR SE with TL VRX wheels fitted with 235/45R17 tyres.
They actually looked alright, no major sagging etc.

I thought about fitting 235/50R17 which has the closest OD to the OEM ones, but I think
I'll need to change wheels to a 35+ offset otherwise the tyres will be rubbing the rear
suspension arms. Also, 235/50R17s cost approx $350 a tyre.

yeah being to wide for the rim will show up when you push the limits of adhesion, and really flex the sidewalls. Id still do it and go the cheaper option of the 235/45R17 based solely on the fact that you will be travelling slower then your speedo indicates and only by about 5km/h... always eer on the side of caution with speeds, really protects the wallet

yeah being to wide for the rim will show up when you push the limits of adhesion, and really flex the sidewalls. Id still do it and go the cheaper option of the 235/45R17 based solely on the fact that you will be travelling slower then your speedo indicates and only by about 5km/h... always eer on the side of caution with speeds, really protects the wallet

225/50r17 OD = 656.59 (OEM)
225/55r17 OD = 679.19 (+22.6mm or +3.4%, speedo reads 3.4% slower than OEM)
235/45r17 OD = 643.12 (-13.47mm or -2.1%, speedo reads 2.1% faster than OEM)

nowhere that I've seen will recommend putting 235mm tyres on any rim less than 7.5" wide. assuming that the OEM speedo is correct (which it probably isn't, most read slightly faster than actual speed), the 235/45 will read an extra 2.1% faster. so if the speedo is out by 5% on OEM tyres, it will be out about 7% with the smaller tyres. this can lead to issues when travelling longish distances, not the least of which is you think you're driving just on or under the speed limit when in fact you're doing almost 10km/h less than it.

the larger tyres will help if the speedo by being a good deal bigger, but they will also require certification because the OD is more than 15mm larger than OEM.

of course, the speedo could be spot on with the OEM size. I know mine isn't!!

cheers,
.wook

225/50r17 OD = 656.59 (OEM)
225/55r17 OD = 679.19 (+22.6mm or +3.4%, speedo reads 3.4% slower than OEM)
235/45r17 OD = 643.12 (-13.47mm or -2.1%, speedo reads 2.1% faster than OEM)

nowhere that I've seen will recommend putting 235mm tyres on any rim less than 7.5" wide. assuming that the OEM speedo is correct (which it probably isn't, most read slightly faster that actual speed), the 235/45 will read an extra 2.1% faster. so if the speedo is out by 5% on OEM tyres, it will be out about 7% with the smaller tyres. this can lead to issues when travelling longish details, not the least of which is you think you're driving just on or under the speed limit when in fact you're doing almost 10km/h less than it.

the larger tyres will help if the speedo by being a good deal bigger, but they will also require certification because the OD is more than 15mm larger than OEM.

of course, the speedo could be spot on with the OEM size. I know mine isn't!!
cheers,
.wook

mine is out 3'ks with the 17" on and its the same with my 19's

so does this mean the fuel trip meter and odometer could be reading inaccuratly if the wrong rolling diameter is used? or am i way off

225/50r17 OD = 656.59 (OEM)
225/55r17 OD = 679.19 (+22.6mm or +3.4%, speedo reads 3.4% slower than OEM)
235/45r17 OD = 643.12 (-13.47mm or -2.1%, speedo reads 2.1% faster than OEM)

nowhere that I've seen will recommend putting 235mm tyres on any rim less than 7.5" wide. assuming that the OEM speedo is correct (which it probably isn't, most read slightly faster than actual speed), the 235/45 will read an extra 2.1% faster. so if the speedo is out by 5% on OEM tyres, it will be out about 7% with the smaller tyres. this can lead to issues when travelling longish distances, not the least of which is you think you're driving just on or under the speed limit when in fact you're doing almost 10km/h less than it.

the larger tyres will help if the speedo by being a good deal bigger, but they will also require certification because the OD is more than 15mm larger than OEM.

of course, the speedo could be spot on with the OEM size. I know mine isn't!!

cheers,
.wook

My OEM were 215/60R16 with OD of 664.4mm so 225/55R17 is 14.79mm bigger. You had
me worried there for a while.

My OEM were 215/60R16 with OD of 664.4mm so 225/55R17 is 14.79mm bigger. You had
me worried there for a while.

sorry, I thought you had 17s with the 225/50 as OEM.

cheers,
.wook

so does this mean the fuel trip meter and odometer could be reading inaccuratly if the wrong rolling diameter is used? or am i way off

usually, yes. the VW I have has a built in "error" in the speedo, but the odometer and everything else uses the real speed and distance, which happens to be accessible through the climate control.

I do not believe Mitsu has done this, so yes, the odometer and trip computer will be reporting inaccurately if you change the OEM OD.

it may even be reporting inaccurately with the OEM wheel/tyre combination. the only way to tell is to travel a known distance and see what the odometer says.

cheers,
.wook

so would the odometer be ticking over quicker with a smaller than factory rolling diametre or would it be the other way around?

Smaller tyres will cause the ODO to tick over quicker.

Ended up getting 225/55R17 Maxxis MA-Z4S at $210 each. 225/55R17's are now the standard fitment to GMs so they are cheaper..


Also standard to the new VE wagon are 245/45/18, which have a similar OD to these, so if these fit your AWD, then the 18s should fit mine IF the offset is correct, right?



I thought about fitting 235/50R17 which has the closest OD to the OEM ones, but I think I'll need to change wheels to a 35+ offset otherwise the tyres will be rubbing the rear suspension arms. Also, 235/50R17s cost approx $350 a tyre.

What offset are you running now? Also with the 225/55s you've just bought, how close are they to the 'knuckle' just over the rear wheels?

My TL VR has 235/45 on the stock Ralliart rims.

Also standard to the new VE wagon are 245/45/18, which have a similar OD to these, so if these fit your AWD, then the 18s should fit mine IF the offset is correct, right?




What offset are you running now? Also with the 225/55s you've just bought, how close are they to the 'knuckle' just over the rear wheels?

I can't remember how much room there was with the OEM fitment but with the 225/50R17 I
could just fit my pinky, now with 225/55R17, it can't get it in al all. Look like I lost 3mm of
room.

I,m running 18/7.5,s on my AWD with 235/40zr1895wmaz1 Maxxis;no scrubbing etc.,currently at standard height.

I,m running 18/7.5,s on my AWD with 235/40zr1895wmaz1 Maxxis;no scrubbing etc.,currently at standard height.

What is the offset?

What is the offset?
Sorry Vlad,can't find that info in my paperwork.Bought them from B.JANE at Gawler if thats any help.Wheels are Advanti Tenso's.

Sorry Vlad,can't find that info in my paperwork.Bought them from B.JANE at Gawler if thats any help.Wheels are Advanti Tenso's.

That's ok. I pressume its 35+ offset. Anyhow, its stamped on the inside face of the wheel,
typically on the forks.

That's ok. I pressume its 35+ offset. Anyhow, its stamped on the inside face of the wheel,
typically on the forks.
Yeah,just had a look under my car with a mirror and it says et 45.I've got about 5mm clearance between tyre and susp.arm.

Thanks for the info. However, you do realise the tyres on your car are illegal. Its diameter
is more than 15mm smaller and I think the load rating will be a lot less than 95. That is why
you still have 5mm space. For a moment I thought the suspension arm actually moves to
accomodate bigger wheel/tyre combos. You should be fitting 234/45R18 tyres and having
40+ offset wheels. I now realise that I made the same mistake of not having smaller offset
wheels so I can fit larger tyres. Oh well. Live and learn.

Thanks for the info. However, you do realise the tyres on your car are illegal. Its diameter
is more than 15mm smaller and I think the load rating will be a lot less than 95. That is why
you still have 5mm space. For a moment I thought the suspension arm actually moves to
accomodate bigger wheel/tyre combos. You should be fitting 234/45R18 tyres and having
40+ offset wheels. I now realise that I made the same mistake of not having smaller offset
wheels so I can fit larger tyres. Oh well. Live and learn.

I,m running 18/7.5,s on my AWD with 235/40zr1895wmaz1 Maxxis;no scrubbing etc.,currently at standard height.
pretty sure that's the load and speed rating.

but yes, assuming the OEM was 215/60r16, the OD is out by too much. should have gone with a bigger tyre. 245/40r18 or 235/45r18.

cheers,
.wook

Yeah my load and speed ratings are fine. Do rim widths affect O.D.?:confused:

Yeah my load and speed ratings are fine. Do rim widths affect O.D.?:confused:

It can, but not by much. It all depends on how the tyre sits on the rim.

Yeah my load and speed ratings are fine. Do rim widths affect O.D.?:confused:
no, OD is based on tyre width, profile height, and rim diameter.

235/40r18 = 235mm tread width, 40% of tread width as the profile height (so 235mm * 40% = 94mm), r stands for radial tyre, 18 is the diameter of the rim in inches (so 18 * 25.4mm = 457.2).

so the OD of 235/40r18 tyres is 457.2 + 94 + 94 = 645.2mm

215/60r16 OD is 406.4 + 129 + 129 = 664.4mm

you can't legally change your OD by more than +/- 15mm.

cheers,
.wook

no, OD is based on tyre width, profile height, and rim diameter.

235/40r18 = 235mm tread width, 40% of tread width as the profile height (so 235mm * 40% = 94mm), r stands for radial tyre, 18 is the diameter of the rim in inches (so 18 * 25.4mm = 457.2).

so the OD of 235/40r18 tyres is 457.2 + 94 + 94 = 645.2mm

215/60r16 OD is 406.4 + 129 + 129 = 664.4mm

you can't legally change your OD by more than +/- 15mm.

cheers,
.wook

As I said, the OD can be changed by the wheels width. That is why tyre websites list the
OD on the actual rim width used as well as giving a range of the allowable rim widths. See
the following table from Yokohama.

As I said, the OD can be changed by the wheels width. That is why tyre websites list the
OD on the actual rim width used as well as giving a range of the allowable rim widths. See
the following table from Yokohama.

sure, it can also be changed by the tyre pressure, but that would be splitting hairs... most places will just use the tyre designation to ascertain the OD.

Damn tyre dealers.I've been horneswoggled:rant: :cry:

Also for others interested, My rims are 19x8.5 +35 offset. No guards have been rolled and no scrubbing when going over speed humps(we have some big ones in Townsville) or steep inclined driveways, so quite happy.
Probably why it looks like its got such a wide track and nicely fills the guards.