What effect Would a donut spare have on a differential?

[bronsin]

Assuming you put your doughnut spare tire on one of the front wheels with that tend to mess up the differential? I mean it’s not as big in diameter as a regular wheel and my understanding is the differential needs to wheels of the same diameter to work properlly.

Or is it in fact perfectly OK to put that spare opposite a regular wheel on the front end?

[justanotherdrunk]

the manual does not prohibit

■When the compact spare tire is attached
The vehicle speed may not be correctly detected, and the following systems
may not operate correctly:
●ABS
●Brake assist
●VSC
●TRAC
●Cruise control (if equipped)
■Speed limit when using the compact spare tire
Do not drive at speeds in excess of 50 mph (80 km/h) when a compact
spare tire is installed on the vehicle.
The compact spare tire is not designed for driving at high speeds. Failure
to observe this precaution may lead to an accident causing death or
serious injury.


since its not a limited slip diff there should be no problem


i remember on some of the performance cars i had with limited slip diffs the spare had to be in front so a rear flat meant demounting 2 wheels on those rwd cars

imagine a posi rear end forced to slip continuously by mismatched tire heights

ouch!

[kevinj93]

The compact spare will have less grip than a standard size tyre. On the front, it wil affect youe steering, acceleration and braking. If you are only going to use it to get to the nearest tyre repairer, fine. If you have to go any sort of distance, it's probably better to put the space saver on the rear of the Yaris.

[Bluevitz-rs]

With a regular open diff it will no effect. You should not if you have a limited slip diff.

However as others have said, you really shouldn't ever use a space saver on the front as 75%ish of your stopping power comes from the two front wheel. As well as steering.

[mrpj]

With a regular open diff it will no effect. You should not if you have a limited slip diff.

However as others have said, you really shouldn't ever use a space saver on the front as 75%ish of your stopping power comes from the two front wheel. As well as steering.

I agree -
But if you are some distance from the nearest place where the flat tyre can be repaired or replaced, or home for access to another jack (if owned)or some means of supporting the car and only have the vehicle jack, there really is no other option. How many of us carry around a trolley jack, axle stands etc.?
Hence, I would suspect the 50mph limit to allow for the smaller width tyre.
I have been in that situation and, if driven sensibly, it does not pose a problem.
e.g. take corners much slower, think ahead, remain a longer distance from vehicles in front etc.

[Bluevitz-rs]

I agree -
But if you are some distance from the nearest place where the flat tyre can be repaired or replaced, or home for access to another jack (if owned)or some means of supporting the car and only have the vehicle jack, there really is no other option. How many of us carry around a trolley jack, axle stands etc.?
Hence, I would suspect the 50mph limit to allow for the smaller width tyre.
I have been in that situation and, if driven sensibly, it does not pose a problem.
e.g. take corners much slower, think ahead, remain a longer distance from vehicles in front etc.

You need to think outside the box a bit.

Jack up the rear and replace the rear tire with the spare. Then jack up the front and put that good tire on the front. Not too difficult

[bronsin]

Well i got to try the donut.

Picked up a nail the night befor a 6 inch snow. Went out in the am early to go food shopping and the TPMS ! was on. Flat rear tire. As I have Parkinsons and have trouble moving my hands sometimes I took the wifes car and called AAA to change the tire upon returning from shopping. Then went out driving n the snow.

Not bad!

[SirDigby]

You need to think outside the box a bit.

Jack up the rear and replace the rear tire with the spare. Then jack up the front and put that good tire on the front. Not too difficult

that's not really outside the box.

you should have learned this in driving class...

[mrpj]

You need to think outside the box a bit.

Jack up the rear and replace the rear tire with the spare. Then jack up the front and put that good tire on the front. Not too difficult

You are, of course correct. I obviously forgot to put on my thinking cap.:rolleyes:
I still don't think there is a more substantial risk by fitting it to the front IF care is taken when driving. Toyota don't offer any preferences or warnings in the manual either. If it was that impotant, they would surely advise rear fitting only?
In the U.K. it is usually avised, when replacing tyres, to fit the new ones on the rear i.e. if changing front tyres, swap the wheels, front to back. So fitting the spacesaver to the rear sort of negates that.
We don't rotate tyres/wheels which seems to be common in the U.S. nor is it part of the sevicing schedule.
I have an old classic car and all the tyres are no wider than the Yaris's "doughnut" with no limit on speed - however the max speed of the car is not much more than 60mph!

[Bluevitz-rs]

You are, of course correct. I obviously forgot to put on my thinking cap.:rolleyes:
I still don't think there is a more substantial risk by fitting it to the front IF care is taken when driving. Toyota don't offer any preferences or warnings in the manual either. If it was that impotant, they would surely advise rear fitting only?
In the U.K. it is usually avised, when replacing tyres, to fit the new ones on the rear i.e. if changing front tyres, swap the wheels, front to back. So fitting the spacesaver to the rear sort of negates that.
We don't rotate tyres/wheels which seems to be common in the U.S. nor is it part of the sevicing schedule.
I have an old classic car and all the tyres are no wider than the Yaris's "doughnut" with no limit on speed - however the max speed of the car is not much more than 60mph!

It's more about the fact that the space saver is has the same section width as a front tire on a motorcycle. You can't predict an emergency braking or steering situation, so as to be proactive, you should simply always put the temporary spare tire on the rear.

[bronsin]

Good observation about the cross-section of the donut resembling a motorcycle tire. Food for thought!