Ranger Mods

I am completely ignorant about wheels/tyres.

My son fitted 20 inch rims to his Commodore, up from 18inch.

I thought it was for a better ride, he said it was to look better.

He said the ride is rougher because total wheel diameter is the same as 18inch.

The rims are bigger but the tyres are low profile.

I was considering getting a set of bigger rims but unless I can still fit normal tyres, I don't want a rough ride.

Someone steer me in the right direction.

I can get a set of Wildtrak wheels, removed from new but is an extra one inch really a benefit?

Is 19 or 20 better?

Taller tyre side wall would generally lead to a softer ride at the right pressure as it allows for flex. Bigger the rim then lower the profile, so the side wall is not as tall, stiffer, less flex, harder ride.

So smaller the rim eg 16 inch, larger side wall to equal say 31 inch vs. larger rim 18 inch, smaller side wall to equal 31 inch.

Someone else may be able to explain it better but that is the short of it.

Dead right Stew, and when in the bush not many stock 18 & 20 inch tyres, stick to the 17 inch rims as they are very common these days, if you have a lift 285/70/17 are nice.

So upgrading wheel size for me is pointless as I am not going to lift the car, right

Pretty much Ross

Thanks

I'm more than happy with the 17" ROH rims and fitted with 285-65s. It gives me a 1" larger diameter and with the +20mm offset it fills the flares nicely. Still tows the van nicely, so it hasn't upset the gearing too much.

With the 17's I know I can get decent off road tyres and have plenty of flex in the sidewalls when I let them down for sand or rocky terrain. Just my opinion, but I reckon 20" wheels on a 4x4 is useless and strictly wank factor... this is where I duck for cover...

What flares do you have Gerry?

I have been offered a set of Wildtrak wheels, done 10klms.

They are 18inch and he wants $400.

If you get the standard Wildtrak wheels don't put flares on.

Hi RossPat,

Ford put them on when I bought the car, so no idea what brand they are mate. But the only way you'll fill them is to get aftermarket wheels with a different offset.

Mine looked pretty weird with the standard offset rims and flares. If you go with the WT wheels, then don't bother with the flares.

naddis01 wrote: ↑Wed Jul 18, 2018 2:57 pm If you get the standard Wildtrak wheels don't put flares on.

Why not?

As Gerry said, it will look funny. The wheels already sit inside the guards so with flares you are adding probably about 40mm extra to the width. It will look like dumbo ears or something.

I thought so, the only difference between the Wildtrak and XLT wheels is one one inch in height, the tyres are the same I think.

Tyres cannot be the same as they suit an 18inch rim. If you mean the overall circumference then the 18 is a tiny bit larger.

For offroad trips, I replace my wildtrak factory supplied 18's with 275/70 R17's on 8" wheels ... with the right offset sit nicely under an unlifted truck with no flares and perfectly adjusts the 5% "over-read" the speedo had from factory to a spot-on figure. Counting the days until I wear out the original rubber so I can replace with taller tyres for an accurate speedo between dirt trips.

That's fine, but you do realise that if your speedo reads spot on, your odometer, fuel consumption and DTE readings will all be out.

Marked wrote: ↑Thu Aug 23, 2018 10:23 pmperfectly adjusts the 5% "over-read" the speedo had from factory

I am no expert but I am not sure that is correct.

I have taken a GPS speed reading off my phone.

I have also taken a GPS speed reading off a Garmin GPS system and they are all very close to the same @ 60, 80, 110 & 1xx.

RossPat wrote: ↑Fri Aug 24, 2018 10:52 am

Marked wrote: ↑Thu Aug 23, 2018 10:23 pmperfectly adjusts the 5% "over-read" the speedo had from factory

I am no expert but I am not sure that is correct.

I have taken a GPS speed reading off my phone.

I have also taken a GPS speed reading off a Garmin GPS system and they are all very close to the same @ 60, 80, 110 & 1xx.

Which part wouldn't be correct? GPS speed reading with standard wheels reads 80km/h when speedo says 84, 100 when speedo says 105.

With the off-roads, reads spot on on gps compared to speedo.

GPS speed reading would be correct. If your speedo reads the same as the GPS then your odometer, DTE and economy figures will all be out.

[quote=GerryP post_id=5665 time=1535061804 user_id=52]
... If your speedo reads the same as the GPS then your odometer, DTE and economy figures will all be out.

I am not sure I am understanding clearly ... are you suggesting that the odo, etc. are only accurate when the speedo reads incorrectly?

I do understand that changing wheel diameter via forscan doesn't change odo, etc. but surely physically adjusting wheel diameter would mean that all values actually read correctly? I would have expected that if the speedo was out from factory, the odo would be out by the same amount?

Essentially yes. The car's computer reads the actual speed (based on standard tyre circumference) correctly and uses that to do the various calculations and to update the odometer. But, for the speedo, it adds a percentage prior to displaying on the dash - it's written in the firmware, so can't be changed using Forscan.

Hence, a standard car will always read higher on the speedo in order to comply with the ADR which states that a speedo cannot read less than actual but can read more (within set limits).

With bigger diameter tyres, whilst your speedo may read spot-on, if you read your speed using a Scangauge, Ultragauge, Forscan etc., you'll see what the computer thinks your real speed is and it will show less than what your speedo is telling you.

Confusing I know... hope that makes sense.

It does make sense, thank you - I also went and read the tyre size thread under forscan programming where it was all explained very clearly.

For day to day driving I am more interested in having the speedo reading correctly, so will be happy leaving programmable settings at standard and using physical tyre diametre change to sort the speedo reading. Once I decide what I want displayed using Scanguage I might reassess ...