PantsUK

iTrader: (1)

Having had the standard RE070 tires on I'd gotten used to driving it with all of the twichy oddness, most other people who drove my car though found it very unsettling especially when changing lanes (two hands at all times).

Now have
225 45 17 (Goodyear Eagle F1) - Front
235 45 17 (Prestivo- STS Holburn exclusive) - Rears

£40 four wheel allignment


COMPLETELY DIFFERENT CAR !!!!

I was considering suspension and all sorts of other changes but the biggest change have been getting rid of the re070s on the front !!!! (I know this because I changed them set at a time and the F1s were on the back then put on the front when I bought the prestivos)

Fat Boy

Prestivos Get F1 s all round and it'll be transformed again

PantsUK

iTrader: (1)

So far so good mate !!!!!

I'll wait till they wear out they've been bloody good so far, not such a prob anyway as they're on the back. Guy I was chatting to had them on the back of his bmw running 300 through the back wheels and reckoned they gripped well so we'll have to wait and see
They wont be going on the front though.

PantsUK

iTrader: (1)

Weren't the dogsh1t cheap ones by the way either .... thought I'd better add that as I know they do have them as well!!

lucky_strike

225 front and 235 rear? Is that a common setup?

chocolate_o_brian

iTrader: (22)

just curious, on a scoob awd car dont you have to have the exact same tyre sizes all round. if im correct in thinking the rears will have a larger diameter due to the percentage height of the tyre wall in cohesion with the width, thus winding the differential up

just curious as ive been told this by a couple tuners.

PantsUK

iTrader: (1)

I bloody hope not !!!


////// please eee e ee e e be wrong /////


but it does drive well anyway !!

chocolate_o_brian

iTrader: (22)

think about it. do you ever see a subaru getting towed by the front or rear wheels? noop, because the diff will go bang!

always see them all 4 wheels off the ground or on the ground because its an awd car.

WR Scooby

You should really have the same make of tyre all round as if you have a front set that grip well and the rears are slipping you can potentially get Diff wind up from that.

chocolate_o_brian is correct.

cster

I've heard RE070's tramline when tracking is out.
Hopw much of the improvement do you think is down to the 4 wheel allignment.

deangtiuk

iTrader: (3)

You should be running same overall Diameter all round ie 225 45 17 front and rear or 235 45 17 front and rear as you will cause damage to your Diff, as it will wind up.

PantsUK

iTrader: (1)

diameter is the same 235/225 is the width.

This has got me thinking ....

I can imagine having 205 x 245 could be a problem but we are talking about 1cm width difference which obviously will increase grip at the rear but the tires shouldn't grip as well as the fronts (in theory F1 Vs Prestivo) so surely this will balance out.

and again 1cm you'd find a bigger difference having the tyres incorrectly inflated (which probably includes half the people on this forum)

o well I don't know they've both only just been fitted so I'm reluctant to change them yet but clearly I'd like my diff to not explode !.

munna

was the whole different tyre thing a problem with cars like the calibra 4x4 and cavalier...

as far as i know, the diff should not blow...look at the BMW M3..??!!

as per the towing thing, is that not different?, naturally the car was created to have all four to the floor, and not designed to have its ***** dragged..(Sorry about that!)..there for the diff ws not engaged..and thus cause the wind up..

me thinks....

53

iTrader: (41)

Your rear tyre profile etc is larger than your front.
Not good as I understand it.

chocolate_o_brian

iTrader: (22)

ah good, someone spelt it out for the o.p.

the tyre wall height is a proportion of the percentage of the width. can you understand it now. the extra width and same profile still means its taller.

so 225/45 the 45 being the percentage of 225mm the tyre wall is in height 101.25mm

235/45 is 105.75mm.

basically your gonna wind the diff up regardless of having grip etc.

m3 is totally different too, its a rwd car ie only 2 wheels push the car from the back so tyre width makes no difference as long as both rears are the same.

PantsUK

iTrader: (1)

get it now ..... unfortunately.

Butty

iTrader: (2)

Were 235 sized tyres already on the car and the garage just swapped like for like?

Nick

PantsUK

iTrader: (1)

No I asked for them, I had 225 but I knew the rim could take it and I wanted the extra overhang to protect my alloys a bit. Didn't realise there would be a problem.

chocolate_o_brian

iTrader: (22)

without wanting to sound patronising, you would expect any tyre place or respectable garage to know that a permanent awd car needs the same tyres all round.

one thing though, never figured out how awd lambos do it as they have huge tyres on the back compared to the front. anyone answer?

BMWhere?

I would expect they handle it with the final reduction in the front vs rear diff, so the drive shaft speeds are equal at the centre diff, but the front and rear axle speeds will be different to account for the differing tyre sizes.


On a scooby though, tyre sizes should be the same all round and you should also really replace all four together as worn tyres on one end with new tyres on the other will also introduce a slight difference.

Tyre wear on the scooby is usually pretty even anyway, but it can be a good idea to swap the fronts to back every now and again to even up the wear!

deangtiuk

iTrader: (3)

I remember when calibra 4x4 needed tyres if the tyre that is replaced at 8mm the others must be at least 6mm or you would have to sign a disclamer stating you had been told of possible drivetrain issues, the Impreza is AWD and not like the BMW that is only rear therefore ALL tyres should have overall the same diameter. The only 4 wheel drive car you can get away with this is th VAG 4motions and latter Quattros that have a Haldex coupling to enable slip between fron and rear Diffs.

jasonius

iTrader: (1)

Should say in your owners manual (the warning about the diff overheating..! ) to have fitted, not only the same size, but also the same brand and model of tyre all round..!

It also mentions somewhere about rotating the wheels f-r every now and then..!

So there is, as already said, potential for excessive wear to occur running different size/brand/worn tyres on a scoob..!

Looks like you need two new tyres..

cster

Put some 235's on ther front.
Personally I would never mix different brands front and rear.
On the limit there are bound to be different characteristics in different conditions ie tyre slippage.
For me one of the big advantages of AWD is that it is easy to balance on acceleration after apex and different tyres front/back will negate this.

PantsUK

iTrader: (1)

what a bloody nightmare .....

anyhow both up for sale and I'll buy whichever ones I'm left with

see sale thread

https://www.scoobynet.com/private-sa...ml#post7843258

PantsUK

iTrader: (1)

will just add ......

Thanks for some of the advice on here it's been helpfull.

As far as different grip levels front to back you'll always have that due to tyre pressures coupled with you've got a smegging great engine over the front and naf all over the back so there will always be different grip levels.

Personally (which is a shame) and the reason for me starting this thread in the first place was I found it loads better having this new setup over the last which were 225x45x17 front and rear & same make.

Don't get me wrong you still need decent tyres all round regardless of what you do.

Cheers

cster

Yeah - it may well be that the best way to effect the balance is by varying the tyre pressures or by altering the allignment.
Can't say I know much about either though