Do you carry a matching spare tire?

[mountainpete]

So... I'm thinking tires lately... can you tell??? :D

Is your spare tire a matching tire (brand, type)? Is your spare tire a matching size?

I know a lot of guys who carry a spare that is a different size than what they regularily use and say that if it is within an inch or two and you are not locked it doesn't matter. Personally, I have always have a matched spare in the past - exactly the same size and type.

Let's discuss :jump:

[OutbacKamper]

I personally believe in carring a spare of the same size, although I am not too concerned if it is the same type.
You certainly could manage with a spare of "similar" size provided you use it accordingly (ie: drive to the closest tire shop and repair/replace the defective tire immediately). However for "expedition" travel a matching tire (size and type) is mandatory IMO. On my Aussie trip I had one spare of identical size and type (that got used several times for thousands of kilometers) and a second emergency spare of almost the same size (identical diameter ), never used but reasuring to have when heading into the Outback when the primary spare is in use.
Provided it will fit, my suggestion is to always buy 5 tires when changing tire size. The spare, 5th tire, can be a used tire and will usually cost less than what you can get for your old spare, if it is in good shape.
Cheers
Mark

[Boston Mangler]

Some vehicles are VERY sensitive to different size (diameter) tires, especially in 4wd! TLCA and many other clubs of that nature require a Full Size Spare.

All vehicles are different but its best to try to use the same brand AND SIZE!

Reason being: Some brands varying in actually sizing, ie. a goodyear mtr 305/50-16 maybe 1/4" taller then a BFG mud of the same size, or vice versa.

I think an 80 with the front and rear lockers engaged with one tire a different diameter then the others would be a recipe of a tcase explosion!

If your not locked you "could" get away with it, but who is not locked nowadays? :cool:

My Two Cents!

p.s. Yes, all 5 of mine are identical and i rotate the spare in as well :D

[Colorado Ron]

I run same size spare as well. Never know how far in the back country youll have to drive out from when you need a spare. THe way I see it, it always happens at the worst, most PIA spot. And the one situation you didnt want to be in--thats when youll need the spare.

[OutbacKamper]

Some brands varying in actually sizing, ie. a goodyear mtr 305/50-16 maybe 1/4" taller then a BFG mud of the same size, or vice versa.

I was about to say that you get this much variation in the same brand and size due to different wear, however you have covered this too:



all 5 of mine are identical and i rotate the spare in as well :D

This is a great idea, but it does require identical wheels (mine came with 4 forged alum rims and one steel rim) so I never even considered rotating the spare. I will have to keep an eye out for a used matching factory rim.

I must say that I find it hard to understand why a small difference in diameter (say 1/4" - on a spare used briefly) would make much difference even on a locked axle. If you lock the rear and turn a corner (even with identical tires) one rear tire is trying to turn at a different speed than the other and a small amount of scrubbing occurs. This is ok since you only lock the axle on low traction surfaces that allow this to happen. The same would occur with small differences in diameter, wouldn't it? When I used my spare in Australia there was at least a 1/4" difference in diameter because the spare was more worn, I did not notice any ill effects.


Cheers
Mark

[jim65wagon]

If your not locked you "could" get away with it, but who is not locked nowadays? :cool:

Me, :( , although it wouldn't matter much since I do run the same size spare (this ones the same brand/type also).

The spare doesn't make it into the tire rotation, but since it was a used half-tread to begin with the difference in diameter through a tire sets life isn't much.

[Boston Mangler]

I must say that I find it hard to understand why a small difference in diameter (say 1/4" - on a spare used briefly) would make much difference even on a locked axle. If you lock the rear and turn a corner (even with identical tires) one rear tire is trying to turn at a different speed than the other and a small amount of scrubbing occurs. This is ok since you only lock the axle on low traction surfaces that allow this to happen. The same would occur with small differences in diameter, wouldn't it? When I used my spare in Australia there was at least a 1/4" difference in diameter because the spare was more worn, I did not notice any ill effects.


I am no engineer so this is pure speculation, but on a rig like a 80 that is full time 4wd or maybe a subaru that is all wheel drive, I would imagine at highway speeds having different diameter tires would possibly harm or at least alter the charatcheristics of the transfercase of a all time 4wd or all wheel drive vehicle, no?

[datrupr]

My spare does not mach the tires that are on the truck as far as brand etc. But it is the same size (265/75/r16). Actually just a bit smaller than the Firestones I have on there, but it will work to get me off the trail and back home again with out compromising comfort or the trucks drivetrain. You really do not want to drive on a smaler or bigger tire for very long or you could damage some critical drivetrain components.

[Boston Mangler]

I will have to keep an eye out for a used matching factory rim.


I used www.car-part.com to replace mine when i destroyed it. found a nice alloy rim in almost new condition (better then the 4 that were on there) for $75 shipped to my door! :gunt:

[Scott Brady]

I have 6 tires and wheels of the same kind. So I rotate through the entire set. 2nd spare to spare to rear to front and back to 2nd spare. Sides are alternated from the spare position.

And I do not worry about rotation in one direction only.

[HenryJ]

I like having all five the same and using the spare in the rotation. When the spare is in the rotation it is a guaranteed way to have a 20% increase in the lifespan of a set of tires ;)

Here is a good search engine for salvage yard wheels - Inventory search (http://www.gaineyautoparts.com/inventory.htm)

That is how I found a matching alloy wheel for my truck.

[OutbacKamper]

I am no engineer so this is pure speculation, but on a rig like a 80 that is full time 4wd or maybe a subaru that is all wheel drive, I would imagine at highway speeds having different diameter tires would possibly harm or at least alter the charatcheristics of the transfercase of a all time 4wd or all wheel drive vehicle, no?

This makes sense, but...do all wheel drive cars such as Subarus use full size spares or do they use space saver spares? I should know the answer since my wife drives a WRX but I must admit I have never looked at the spare.


Thanks for the suggestions on scources of oem rims. I will be buying new tires before winter, and will see if I can get an extra rim then.

Cheers
Mark

on edit: I just got back from checking the WRX spare: spare 135/70-16 (diameter approx 23.4 inches) other tires are 205/55-16 (diameter approx 24.9 inches)
:exclaim:

[Boston Mangler]

on edit: I just got back from checking the WRX spare: spare 135/70-16 (diameter approx 23.4 inches) other tires are 205/55-16 (diameter approx 24.9 inches)
:exclaim:

Interesting. I am going to look into this more and will report back.

[HenryJ]

Some AWD transfercases use a fluid/clutch coupling and are not affected by differing wheel speeds like a gear/chain directly connected transfercase in a 4x4.

[erin]

:coffee:
I think that traction devices are more dependent on all tires being the same size. Detriot specifically states that all tires must be the same size when using trutracs or the detriot locker. Obviously, manual lockers would not be affected nearly in the same way.

[asteffes]

This makes sense, but...do all wheel drive cars such as Subarus use full size spares or do they use space saver spares? I should know the answer since my wife drives a WRX but I must admit I have never looked at the spare.


Thanks for the suggestions on scources of oem rims. I will be buying new tires before winter, and will see if I can get an extra rim then.

Cheers
Mark

on edit: I just got back from checking the WRX spare: spare 135/70-16 (diameter approx 23.4 inches) other tires are 205/55-16 (diameter approx 24.9 inches)
:exclaim:

They probably also state in the manual or on the spare tire that you shouldn't drive more than forty or fifty miles with the spare. That's to protect the spare and the differentials.

[michaelgroves]

IMO, running with tyres of slightly different diameter won't generally do your vehicle much harm, though you wouldn't want to do it for thousands of miles. It's worse if the tyres differ left to right, than front to back though, so a single spare of an odd size isn't ideal. This is more an issue of unevenness in braking and handling, than differential problems.

If the tyres differ in diameter by, say 5% (i.e. a 31.5 inch and a 33 inch tyre), then the diff pinions will need to rotate at 2.5% of the road-wheel speed (one forwards, one backwards). At 120km/h, the road-wheels are rotating at around 800 rpm, so the diff pinions "spin" at around 20 rpm - or one revolution every three seconds. Nothing's going to get hot or wear out very fast.

Even with permanent 4WD, the centre diff isn't working very hard - a little faster than one rev per second (or half that if there's only one odd-size wheel).

Having said all that, there doesn't seem to be all that much to gain by carrying an odd-size spare wheel on an expedition vehicle. The original context for my thinking about this issue was whther it is essential to use a tyre size that is readily available in the countries you are visiting. I decided I could always get away with using a locally available 7.50-16 as an emergency replacement for the rare 255/85-16s.

Naturally, locking the CDL or engaging 4x4 on a part-time system should only be done when on a slippery surface (and axle locks even more so) - the 5% difference equates to making 40m sweeping turns, so it's not a good idea to lock anything unless the ground will yield easily.

Btw, I have no idea how a viscous coupling would enjoy a constant speed difference of 5%. Any ideas?

[YJ Dave]

I also run a full sized spare, it sucks having to limp home on a mismatced tire. Plus if I need the spair on the trail, it is comforting to know that the spair is still a good stout tire that will help move me up the trail.

[Ric]

yes i do also, have all 5 wheels and tires matching and rotate all 5 like others here...

[Willman]

http://i51.photobucket.com/albums/f374/nicwillman/Rear%20Bumper%20Buildup/DSC01463.jpg

Its a full-size 255 spare! I need to get new rims so i can rotate the 5 around....My rig would look pretty funny with one black steel rim and the rest stock toyota rims.....

:ylsmoke: