Notice: We request that you don't just set up a new account at this time if you are a previous user.
If you used to be one of our moderators, please feel free to reach out to Chris via the facebook Outerlimits4x4 group and he will get you set back up with access should he need you.
Recovery:If you cannot access your old email address and don't remember your password, please click here to log a change of email address so you can do a password reset.

Spare tyre diameter difference to main tyres.

General Tech Talk

Moderators: toaddog, TWISTY, V8Patrol, Moderators

Post Reply
Posts: 148
Joined: Fri Dec 29, 2006 9:22 pm
Location: Melbourne

Spare tyre diameter difference to main tyres.

Post by juls »

New tyres arrived today, MT 117s.

Image

Since the golden rule is to not spend more on any mod than you did on the actual car, I couldnt buy a 5th tyre for the spare.

My plan is to purchase a 2nd hand spare.

So the MT117's measure 900mm (35.5") in diameter (exactly as silverstone say). Incidently each rim and tyre weighs 43kgs.

So how much variation in diameter is acceptable for the spare tyre vs the main tyres.

Since this tyre has 17mm of tread its conceivable you could have a variation of up to 30mm over the life of the tyres.

So I reckon im after a worn 36" tyre that will be around 35" in diameter. Will a worn 35" tyre (around 34" diam) be acceptable?
Posts: 166
Joined: Tue Mar 04, 2008 4:04 pm
Location: SW Victoria

Post by djroberts »

it doesnt matter so long as you arent planning to drive far on the spare. in a full time 4wd (which i dont believe yours is) it can be a problem as increased movement in the drive train can lead to more wear. (side gears and such). i suggest if you do get a flat, just arrange the tyres as such that the spare is on the front. -problem solved.

-Dave
loose as a goose
Posts: 2169
Joined: Fri Jun 16, 2006 4:41 pm
Location: melbourne

Post by joeblow »

or you could let the other tyre down to suit the height of the spare.
lwb 1.6efi,4sp auto,f&r airlockers,dual t/cases.custom coils.builder of ROAD LEGAL custom suzukis...and other stuff.
CAD modelling-TECH drawings-DXF preparation.
http://www.auszookers.com/index.php
Posts: 2585
Joined: Fri Mar 28, 2008 4:45 pm
Location: SYDNEY

Post by thehanko »

joeblow wrote:or you could let the other tyre down to suit the height of the spare.
Whilst letting the tire down will reduce the height of the tire, it will not change the circumference of the tire - which effects how many turns it does at any given speed.

I agree with the first answer, For a short trip you could get away with it as your diff should slip enough to not cause problems. If your driving home in good roads then 2wd and chuck the smaller one on the front.

However if driving off road it should be ok as the reduction of traction should allow a certain amount of slipage anyway.

As long as you dont have welded diffs of anything it should be sweet.

I would go for the 35 as that gives you a half way point between 35.5 and 34.5 which is going to be the rough usage range.
*there's a rock, drive over it :) there's a bigger rock, drive over it :twisted: there's an even bigger rock, oops broke it :oops: Upgrade broken bit :bad-words:
Goto *
Posts: 8556
Joined: Mon Jun 13, 2005 9:34 pm
Location: Sydney

Post by RockyF75 »

I've had a tire guy tell me, rather emphatically, that you shouldn't do it. But I don't see how running a slightly larger tire, on an open diff, is any different to just taking a corner? The diff is doing whats its designed to do, split the drive between the left and right wheels.

So, it MAY cause increased wear on one side. But thats like saying don't turn left or right all the time cause it will wear one part of the diff more :?

EDIT: and an :rofl: for the tire dropping suggestion :D
60 + Turbo, 33"s :armsup:
Posts: 14209
Joined: Sun Jan 11, 2004 11:36 am
Location: Adelaide

Post by -Scott- »

djroberts wrote: it can be a problem as increased movement in the drive train can lead to more wear. (side gears and such).
More wear? Vehicles with a front axle disconnect system (such as Pajero and some Hilux models?) have their front diff side gears spinning for thousands upon thousands of kilometres. I've never heard of one of these diffs needing to be replaced due to wear - will a 3% difference in tyre diameter make much difference?
Posts: 4583
Joined: Fri Jun 11, 2004 5:57 pm
Location: Wheeling in my backyard

Post by sierrajim »

joeblow wrote:or you could let the other tyre down to suit the height of the spare.
Now there's some GREAT advice. Didn't someone at Ford say "just let some air out of the tyres, that will get them riding better" not nlong after there was a spate of tyres exploding attached to Explorers.

DO NOT RUN LOW PRESSURES ON THE ROAD, tyres get hot and let go.

But a cheapo spare that's roughly the same size if you have to.
[quote="Harb"]Well I'm guessing that they didn't think everyone would carry on like a big bunch of sooky girls over it like they have........[/quote]
Posts: 2944
Joined: Tue Feb 11, 2003 5:47 pm
Location: Manjimup, Western Australia

Post by ausyota »

It is fine with an open diff.
With an LSD, auto locker or welded centre it can cause problems.
Paul.
R.I.P Brock Fontanini 28-3-06 - 16-2-08
www.teamcarnage.net
Posts: 2158
Joined: Sat Jan 20, 2007 8:16 am
Location: New Zealand

Post by KiwiBacon »

sierrajim wrote: DO NOT RUN LOW PRESSURES ON THE ROAD, tyres get hot and let go.
Should that be "don't run low pressure at speed"?
Offroad they can heat up and come apart too.
Posts: 3132
Joined: Wed Sep 28, 2005 3:22 pm
Location: Newy

Post by HotFourOk »

joeblow wrote:or you could let the other tyre down to suit the height of the spare.
:rofl: This is the funniest thing I've heard for AGES! :D
[quote="RockyF70 - Coming out of the closet"]i'd be rushing out and buying an IFS rocky[/quote]
Post Reply

Who is online

Users browsing this forum: No registered users and 120 guests