Have I got this right re; tyre replacement ?

Plum · Post by **Plum** » Thu Sep 13, 2007 9:30 pm

After reading the tyre fact sheet, 5 pages or so of past posts on tyres I have come to the following conclusion :

Continental Vancos are the tyre of choice
Load rating 92 front, 96 rear
Front tyres - 195/70 x 15
Rear tyres - 215/65 x 15

Can someone confirm this is what I need for a 4wd aft before I go out and get them replaced please

Cheers
Plum

francophile1947 · Post by **francophile1947** » Thu Sep 13, 2007 9:33 pm

Confirmed sir!!!

Although many people (myself included) use the same size tyre all round on a 4WD.

Plum · Post by **Plum** » Thu Sep 13, 2007 9:39 pm

francophile1947 wrote:Confirmed sir!!!
Although many people (myself included) use the same size tyre all round on a 4WD.

Now lets not confuse me !!

thanks for confirming

Plum

daveblueozzie · Post by **daveblueozzie** » Thu Sep 13, 2007 10:16 pm

same tyres all round 215/65 x 15 . 96 rating and the same on the spare.

Colin Lambert · Post by **Colin Lambert** » Thu Sep 13, 2007 10:19 pm

So Why do Mazda bother to factory fit different sized tyres front and rear (both 2&4 WD).
Stick to the factory fitments. They don't do it for fun!

francophile1947 · Post by **francophile1947** » Thu Sep 13, 2007 10:26 pm

I admire your blind faith in car manufacturers Colin. If they're so good, why do we get safety recalls (including on Mazda Bongos)?

Plum · Post by **Plum** » Thu Sep 13, 2007 11:36 pm

which would decrease fuel consumption, same sizes all round or differing sizes ???
or does it make no difference ?

Plum

francophile1947 · Post by **francophile1947** » Fri Sep 14, 2007 12:40 am

No difference - rolling circumference is almost the same.

dandywarhol · Post by **dandywarhol** » Fri Sep 14, 2007 8:13 am

I know this is going over old ground again which is happening quite a bit these days.

I was originally of the opinion that the different tyre sizes was to overcome an understeering problem but Mazda are cleverer than that

The reason for the different sized tyres (from what I can fathom out) is to introduce different speeds on the front and rear propshafts so the viscous coupling can allow a "Full Time 4WD" function.
The downside to this type of 4WD is that the viscous coupling starts to wear from day one and has a limited lifetime as the gel breaks down inside.
Other manufacturers achieve this difference in propshaft speeds by using different ratios in the front and rear final drives i.e. Land Rover in their Freelander - and they really eat up viscous couplings

Plum · Post by **Plum** » Fri Sep 14, 2007 10:14 pm

francophile1947 wrote:No difference - rolling circumference is almost the same.

OK thanks.
The hassle I had trying to get new tyres today was unbelievable, most places out of stock and fitters arguing about the size differences, telling me I was wrong !
Hey ho we got there in the end.

Plum

trevd01 · Post by **trevd01** » Fri Sep 14, 2007 10:57 pm

dandywarhol wrote:I know this is going over old ground again which is happening quite a bit these days.

I was originally of the opinion that the different tyre sizes was to overcome an understeering problem but Mazda are cleverer than that

The reason for the different sized tyres (from what I can fathom out) is to introduce different speeds on the front and rear propshafts so the viscous coupling can allow a "Full Time 4WD" function.
The downside to this type of 4WD is that the viscous coupling starts to wear from day one and has a limited lifetime as the gel breaks down inside.
Other manufacturers achieve this difference in propshaft speeds by using different ratios in the front and rear final drives i.e. Land Rover in their Freelander - and they really eat up viscous couplings

Dandy

I didn't use to accept this argument. But I am now with you on this one.

I am an ex-Landy owner and have had several Defenders and once had a Freelander. When I was learning for my off road driving certificates the bible was 'Off Road Driving' by Tom Sheppard, which I haven't read since we got rid of the Landy and got the Bongo. Until now...

I've just re-read the chapter in that book on types of 4wd. There is a whole section on 'Pre-load in pseudo 4x4', including this:

"...'pre-loaded' VC that feeds some torque to the rear axle all the time and boosts it when conditions get really bad"

Cites Freelander & Fiat Ducato 4x4 as examples.

So I would say, in difficult conditions, 4wd Bongo owners will get more grip, more of the time, with the correct c1% different tyre sizes.

One question though, why fit different sizes to 2wd Bongos? Unless it also contributes to 'safer' understeering.

(Our 4wd has 215s all round, BTW)

Quicksilver · Post by **Quicksilver** » Sat Sep 15, 2007 3:58 am

Hiya all,

Been having sleepless nights after reading all the threads on tyre sizes and winding up diffs and rolling circumferences after discovering I have a good set of 195s all around.
I`m planning to change the rears to 215s as this can only improve handling and it makes senses.
However I have had the van 6 weeks and it is fantastic. I`ve done 4000km around Wales driven it hard on beaches and to the harbour at Porth Clais near St Davids, straight down the slipway in no more than a couple of inches of water, got me straight to the top of a wet field in little haven and also the highest point on the headland just above newgale, to the west, to take some great photos and managed to get it on to a beach where I shouldnt really have been, in the intrest of science and discovery of course,the point is Its a very capable vehicle and gets me places most cars cant go, I dont really understand how viscous couplings or transfer boxes work but I know it seems to and it seems to manage ok . I wiould like to think that things are built to tolerences.....and maybe instead of worrying we shold just put it in L , hit the hold button next time you see a slipway or a pitch a little higher than everyone else and go for it and enjoyit after all thats what its been designed for!...........Just a thought!
I would like to acknowledge all the the suberb and detailed information and expreriences that members have shared here, it has been invaluable to me and after a 2 year wait am finally enjoying a lifestyle change which is what I think its all about!
Cheers .

neilfraser · Post by **neilfraser** » Sat Oct 06, 2007 9:40 pm

dandywarhol wrote: The reason for the different sized tyres (from what I can fathom out) is to introduce different speeds on the front and rear propshafts so the viscous coupling can allow a "Full Time 4WD" function.

Sorry to be replying to this so long after it's finished, but if the rolling distance of the front and rear tyres is the same how can there be different propshaft speed? Have I missed something obvious?

Thanks

Neil

Colin Lambert · Post by **Colin Lambert** » Sat Oct 06, 2007 10:26 pm

Francophile,
Nothing to do with blind faith. All manaufacturers spend £millions designing vehicles. Why should they go to all the trouble of deciding that different tyre sizes are required if there isn't a very good reason for it. I am not aware of any safety recalls on the Bongo purely because my V reg has not been subject to any (only a valve in the gear box, not safety related) I wouldn't mind betting that NONE of the safety recalls had anything to do with tyre sizes.
Mind you any manufacturer that puts a space saver where a full size wheel will fit without incursion into lugggage space is either bonkers or penny pinching in the extreme. Very good reason for a space saver in my MX-5 but in a Bongo or a Mazda 2??????

francophile1947 · Post by **francophile1947** » Sat Oct 06, 2007 10:36 pm

Blimey Colin - that took a long time to reply

One Bongo recall for the front driveshafts on 4WD - could result in a fire.
Auto gearbox problems that could cause Bongo to move forward in Neutral.
Both of those sound pretty unsafe to me.
No safety recalls for tyres though

Have I got this right re; tyre replacement ?

Have I got this right re; tyre replacement ?

Tyres, diffs and beaches