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Different wheels on the front and back

Chris

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So far I am sensing that we're mainly leaning toward this not being a good idea.
 

TonyP

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Oh I don't know, I think there may be some value in trying this, not on my 120 mind, but I'd say why not.... :whistle:
 

Grimbo

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Why not just fit the same tyre all round ?
Not even sure the 120 has an unequal torque split ?
Bigger rears would push it more bias to the rear ? not sure I would want a tail happy 120 on the road ....
Each to his own though ....50 profile tyres on 20's will last a few hrs on the potholes round here .... not to mention giving a hard ride .
 

chadr

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Each to his own though ....50 profile tyres on 20's will last a few hrs on the potholes round here .... not to mention giving a hard ride .

In fairness, a 50 profile (aspect ratio) on a 305 wide/section tyre is still quite thick and not quite as rubber-band-like as you might imagine.

Still, it doesn't make the OP's idea a good one!
 

Sid

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thinking maybe 275/55/20 renegade tyres could be a good compromise or 285/50/20. i ve seen some 305/50/20 on the 120 series but not sure what modifications they had done. ours has a 2inch lift and diff drop kit. currently have 265/70/17 on 32mm hubcentric spacers which gives about 31 inches. look nice just a little small with the lift kit so thinking something larger to fill out the arches. the 20inch alloys have et25 so with spacers would be ET-7. looking at toyota specs, they did give an option for 285/50/20 from factory with ET25. any recommendations - don't fancy cutting up jeep to fit bigger wheels.
 
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goodoldboy

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thinking there shouldn't be windup if open diffs on the front and centre.
I have 5mm overall height difference caused by new tyres on front, worn on rear, and it winds up when reversing really badly, yours will do the same.

I run rears at 40psi and fronts at 35psi to compensate, but even then its knocks if I reverse around a corner.
let us know how you get on Sid
 

chadr

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Assuming all 4 wheels are going to have the same size tyres, 305/50R20 would probably be a good fit (diameter and rolling radius wise) as not much difference between that and and OEM size. However the clearance for that width of the tyre will be issue - especially at front on full (or any) lock, as I just can't see how they would not foul the rear wing/bulkhead/chassis etc.

Unless of course you go all "Artic Trucks" and widen the track etc. :cool:

Also interested to see where you found;

....looking at toyota specs, they did give an option for 285/50/20 from factory with ET25.....

Is this for the 120? If so, can you please share a link, thanks. :thumbup:
 

Sid

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275/55/20 arch loss of 17.1mm
305/50/20 arch loss of 18.35mm
265/70/17 arch loss 13.25mm
285 arch loss of 8.35mm

so I'm thinking 275 might be the best choice, not as wide as the 305 but similar increase in circumference and shouldn't require any mods or trimming
 

Chris

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At the very least, all other implications aside, the output shafts of the centre differential will be spinning at different speeds if different radius tyres are fitted. The diff is designed to take up, well as it's called, differential rotation when cornering and so on. What it's not designed to do is operate under those conditions all of the time. There will be increased heat generation and accelerated oil shear which is not a good thing. Additionally it would mean carrying two different sized spares.

If this was a good idea, then I'm pretty sure manufacturers would have been onto it by now. Deviating from the OEM diameter on the IFS Landcruisers has been covered in depth. In standard form there is little latitude for increased tyre diameter. It is not impossible and one Colorado owner managed to fit 35" tyres but not before significant suspension and body work modifications. Mild suspension lifts and body mount lifts give only very small additional clearances where full lock is concerned.
 

Sid

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so just means more frequent oil changes, not concerned about the spares.
 

chadr

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As in your original post, this "funny car" setup would be purely for road use and that you would revert to standard for offroad use, have you considered insurance implications?

I'm thinking if you were to have a serious accident and it got to a point where a vehicle inspection was carried out - I would imagine this anomaly would get highlighted pretty quickly. This might be worth considering, even if you intend to revert to standard setup to get it passed at MoT time.

Also, you never really answered the question as to what you hope to gain from trying for a 50:50 torque split front and rear, vs the 40:60 standard setup? Genuinely interested to hear your views.
 

Shayne

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For my 90 series IFS a body lift helped more than a suspension lift when it come to fitting bigger wheels and I also found a greater negative offset helped though i still had to trim and bend some inner arch .

I often wondered if i could do the same to a 120 but it seems to me the bodywork doesnt lend itself to the idea .
 

Chris

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Sid, you may be interested but you're clearly not listening. This is one of the most experienced and friendly forums covering the Landcruiser marque and so far everyone is telling you that this is not only a bad idea but a particularly daft one too that has no conceivable upside to it aside from aesthetic vanity. And yet you persist to pursue the idea much to our combined bemusement. I think that now being two pages in, you're unlikely to get any alternative responses to the already overwhelming tide of advice that this is an idea best left alone. We welcome freedom of ideas, thoughts and speech, but you need to listen to what is being said and not simply come back each time trying to justify what is at the heart of it a bad notion.

I must remind all members that comments containing personal attacks, character profiling and such, should they been deemed so, will not be tolerated on this forum. As frustrating as we might find this baffling modification, please keep responses within the rules of the forum.
 

Jacob100

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The use of 'jeep' as a generic term to mean any 4x4 led me to think the OP might be from NI.
 

Sid

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I understand the concerns but the design of the transfer box and open centre diff - why cant it accommodate. I'm not saying that this is what I will do, I'm just thinking if its an open diff theoretically it shouldn't be a problem. opinions about oil shear have been mentioned and to me this just means more frequent oil changes. the diffs dissipate heat well under normal driving conditions and load. think what I'm asking does the centre open diff operate the same way as an axel open diff. the transfer box splits the torque - is this the reason for complications? I'll probably go with 275/55/20 front and back but im still trying to picture the workings of the transfer and centre diff. regarding safety and legality it would pass the mot and as long as declared to the insurance would be ok. advancing our understanding of the world requires questioning what has gone before. the world was flat - it was questioned. the laws of physics become theories when disproven. never to be complacent and drive to improve it what I believe in. to me this means widening our understanding. I've had some good points mentioned. thanks for those.
 

Chris

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Well they do say there is no such thing as a stupid question.....
 

Andy

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Sid, i still can’t quite get my head around your reasoning for wanting to do this.

even if you came back and said something like “ my dear old aunt Doris left me some different size tyres in her will I want to use them in her memory” I might just possibly start to understand your logic, but................well I just don’t know!!

please enlighten me!

Andy
 
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