Is my spare useless?

Dmopar74 · Mar 15, 2017

Factory spare is 275/70/18, new tires are 305/70/18. I'm thinking I can't use my spare without screwing something up?

VicViper · Mar 15, 2017

Overthinking it, 305 on flat? Use the spare...get the 305 replaced/plugged/repaired, then put the spare back under the truck. Of course the handling is going to be different with the smaller spare.

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Dmopar74 · Mar 15, 2017

Just wondering incase I ever get a blowout that I can't plug

07MegaCabRam · Mar 15, 2017

You are SMART for thinking this! Most people don't even think about it when doing larger tires etc. On a solid front/rear axle.. can be pretty bad if one tire is spinning at a way faster rate than the other!! Blow them gears!!!

You should be good!
Diameter inches (mm) 33.16 (842.2) 34.81 (884.2) 1.65 (42) 5% difference.

Mega-Hemi · Mar 16, 2017

Most manufacturers say if you get a flat on a rear to take a wheel off the front and put the smaller spare up there. Saves the rear diff. Of coarse that was back when the front diff would disengage, not sure if it would make a difference now.

NewBlackDak · Mar 16, 2017

Mega-Hemi said:
Most manufacturers say if you get a flat on a rear to take a wheel off the front and put the smaller spare up there. Saves the rear diff. Of coarse that was back when the front diff would disengage, not sure if it would make a difference now.

The hubs are disengaged on current gen HDs, unless you're running in 4WD.

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68PowerWagon · Mar 16, 2017

Aren't the donut spare's they put with a lot of cars a smaller diameter? Don't think it is really going to matter as temporary fix.

BBRAM2500 · Mar 16, 2017

It will be fine the only trouble arises when your using 4wd and even that only really is if you hit hard pack binding may happen if you can throw it on the front and drop everything in 2wd you will be fine

cattaco · Mar 17, 2017

Also if you have a limited slip you shouldn't use different size tires.

U&A · Mar 20, 2017

Max out the PSI in your spair. When you need it, Drop the psi in the other 3 to a safe psi but still lower. You will be supprised that you can loose a good .5" or more depending on how fast you plan on driving is whst should determine how much you can comfortably let out. Just drive it directly to the tire shop. And dont go fast.

It will be fine. Like airing down for iff road.

Is my spare useless?

Dmopar74

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VicViper

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Dmopar74

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07MegaCabRam

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Mega-Hemi

US AIR FORCE '08-'18

NewBlackDak

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68PowerWagon

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BBRAM2500

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cattaco

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U&A

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