[shark]

Hey guys I got a flat that can't be repaired today.
I'm currently running 215/75r15 but I have some spares at home that are 195R15.
Will I be able to go four wheel driving with the 215s on the front and the 195s on the rear??

[alien]

you probably shouldnt... you'll get transmission windup from the difference in size. You'd be best to run 195's all round if you have 4 of them as spares.

[shark]

Which I don't

[sideways]

What do the 195s measure?

I wouldn't on my own car but I've been in a fair few farm utes with a combo of 750/16s and 205r16s that didn't explode or anything.

Cant just tube it?

[sideways]

Actually, I lie.

I ran 30s on the back of the lj81 with 28s on the front. I went fine, couldn't notice.

I accidently drove it around in 4wd for ages because I thought it was in 2wd but it's super hard to get it into 2wd so yeah.

[fordem]

alien wrote:

you probably shouldnt... you'll get transmission windup from the difference in size. You'd be best to run 195's all round if you have 4 of them as spares.

Agreed you shouldn't - but then again you probably won't be using 4WD in any situation where there isn't already enough slip to prevent wind up - what's confusing is if this is a "can't get the flat fixed today type deal" - how are you getting the 195's mounted? Why not put the spare on and put the 195 on the back, just in case.

I've actually got 215/65R16s on the road wheels and 215/70R16 on the spare right now - not as much of a difference - but it's there if I need it, and so far I haven't had a flat.

[shark]

The 195's are on rims already..

[BlueSuzy]

should be fine for offroad only.

there was a time i had a 215 and a 205 not realising, on the same diff, with a welded diff.. Guess which one wore out faster

[Scrawny]

I think you'll find there's bugger all height difference between the 215/75 and 195

[alien]

Scrawn wrote:

I think you'll find there's bugger all height difference between the 215/75 and 195

a 195r15 measures 30" diameter... a 215/75r15 measures 27.5" - that's a total of 63mm difference in rolling diameter, or another way to look at it is that the 195r15 is 9% larger.

So if the back wheels are doing 10km/hr, the fronts will be spinning at 11km/hr.... its either going to spin the front wheels or drag the rears in a low traction scenario... and if its in 4wd with a lot of traction (rocks) the tcase won't be happy.

[Scrawny]

alien wrote:

Scrawn wrote:

I think you'll find there's bugger all height difference between the 215/75 and 195

a 195r15 measures 30" diameter... a 215/75r15 measures 27.5" - that's a total of 63mm difference in rolling diameter, or another way to look at it is that the 195r15 is 9% larger.

Where did you get those measurements from?

These tyres were on my MKI Vit, shows both 195R15 and 205/75R15 which says to me they're the same size. That would make the 215/75 slightly BIGGER, but only by a bees dick

[shark]

The tyres are old mate.
I got that off the side wall.
It need to last me two weeks both on road and hopefully off road tonorrow.

[shark]

195s

[shark]

Hard to take a comparison shot. There isn't a huge difference but im concerned.

I don't think there would be any issues in 2wd??

[Scrawny]

2wd will be fine! The front diff won't be turning so it doesn't matter.

If you're really concerned about 4wd just engage it when you really have to. I still don't think there'll be any issues tho.

[sideways]

alien wrote:

Scrawn wrote:

I think you'll find there's bugger all height difference between the 215/75 and 195

a 195r15 measures 30" diameter... a 215/75r15 measures 27.5" - that's a total of 63mm difference in rolling diameter, or another way to look at it is that the 195r15 is 9% larger.

No, you're assuming a 100% aspect ratio which is generally incorrect. When the aspect ratio isn't given, it's normally 80%. If 195r15s were 30", we could legally run 30s!

Run them shark, that's bugger all difference.

[alien]

Ah right... well there we go i learneded something...

in that case, and given the images then its fine. I ran 2 different brands of 215/75r15 on my sierra - coopers on the front and goodyears on the back... the goodyears were bigger than the coopers by about 15mm when you stood them side by side. Offroad you could hear the front end spinning on gravel etc, not unlike the way a locker drags or spins a wheel. Changing from low to high range or 4wd to 2wd the transfer would let out an allmightly CLUNK too. You could stop that by rocking the car side to side to allow the wheels to slip a bit though =)

[sideways]

alien wrote:

Ah right... well there we go i learneded something...

in that case, and given the images then its fine. I ran 2 different brands of 215/75r15 on my sierra - coopers on the front and goodyears on the back... the goodyears were bigger than the coopers by about 15mm when you stood them side by side. Offroad you could hear the front end spinning on gravel etc, not unlike the way a locker drags or spins a wheel. Changing from low to high range or 4wd to 2wd the transfer would let out an allmightly CLUNK too. You could stop that by rocking the car side to side to allow the wheels to slip a bit though =)

As above, you shouldn't be in 4WD where there's enough traction to make a difference anyway.

[303zuke]

sideways wrote:

alien wrote:

Scrawn wrote:

I think you'll find there's bugger all height difference between the 215/75 and 195

a 195r15 measures 30" diameter... a 215/75r15 measures 27.5" - that's a total of 63mm difference in rolling diameter, or another way to look at it is that the 195r15 is 9% larger.

No, you're assuming a 100% aspect ratio which is generally incorrect. When the aspect ratio isn't given, it's normally 80%. If 195r15s were 30", we could legally run 30s!

Near enough to correct. Where the aspect ratio is not specified on "R" tyres (which stands for Radial), the aspect ratio is 78%. On Crossply tyres (those without R) without a stated aspect ratio, such as 6.00-16, the aspect ratio is a [i]nominal[i] 100% (but rarely exactly that).

[303zuke]

alien wrote:

Ah right... well there we go i learneded something...

Changing from low to high range or 4wd to 2wd the transfer would let out an allmightly CLUNK too. You could stop that by rocking the car side to side to allow the wheels to slip a bit though =)

You can also release the tension by reversing a metre or two before changing to 2wd. Or if you have a bunch of mates with you, lift one corner of the car and that wheel will spin and take off the tension completely. Love the light weight of Suzukis!

[shark]

I'm gonna give it a go tonorrow.
Hope I don't break something cause of it. They do look really close.

[sideways]

They'l be fine mate, you'd squish your tyres more on rocks than the difference between them! It's only the radius that matters so it's basically nothing.

Thanks for clearing that up 303. I remember reading crossplies are 105%, I certainly reckon 16-6 bartreads are anyway!

[alien]

put the smaller ones on the front so it goes fast like a drag car =)

[sideways]

Yeah, it'l be faster because it's always going down hill.