Tire size help

Happienumber

Happienumber

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Quebec
Threep the Jeep came to me with 285/70/R17 tires installed. I’m trying to work out my lift kit needs and I’m running into conflicting information regarding what that size tire is in inches.
“Conversion” websites tell me it’s 32.7, I’ve seen people referring to them as 31’s, and as 33’s in posts. I measured them with a tape measure and the ones on the ground measure 31.5 and the spare measures 32 (I’m assuming due to tire pressure and weight on them)

This is how they fill out the wheel well on my otherwise stock 2006 TJ:

IMG_7673.jpeg


My speedometer is also OFF and I want to get a new speedometer gear but I can’t figure out what to classify my tires as.

Thank you for helping me out with such a silly noob question!

(Side question somewhat related: hours of research has not led me to answers about what the backspacing is on my wheels. A reverse image search FINALLY led me to them being Tuff T10 A.T. Which are no longer in production, but all the specs sites I can seem to find don’t list backspacing. Is there a better site to look at or a way to just measure it my own gotdang self? Thank you!!)
 
Actual size is best for the speedometer charts. I have 35" BFGs and they're close but 34.5"... wife's JK has 35" Mickey's and they're 33" actual.

Looking at your Jeep I'd say it's pretty close to the ideal 3.75" backspacing...but best pull one off and measure.

You might be able to get away with some coil spring spacers and longer shocks...but it's best to make a longer term build plan.

-Mac
 
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Happienumber said:
Threep the Jeep came to me with 285/70/R17 tires installed.


My speedometer is also OFF and I want to get a new speedometer gear but I can’t figure out what to classify my tires as.


(Side question somewhat related: hours of research has not led me to answers about what the backspacing is on my wheels. A reverse image search FINALLY led me to them being Tuff T10 A.T. Which are no longer in production, but all the specs sites I can seem to find don’t list backspacing. Is there a better site to look at or a way to just measure it my own gotdang self? Thank you!!)
Click to expand...

For the tire size, consider them a 33. While their nominal measurement is 32.7" unmounted, a typical 33x12.50 isn't any larger, and that's what the charts refer to when they say a 33.

For the wheels, from the old application chart I found, it appears that the only 17" wheel with a 5x4.5" bolt pattern (5x114.3mm) was 17x9 with a -13 offset. That works out to be about 4.5" backspacing.
 
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deadbeat son said:
For the tire size, consider them a 33. While their nominal measurement is 32.7" unmounted, a typical 33x12.50 isn't any larger, and that's what the charts refer to when they say a 33.

For the wheels, from the old application chart I found, it appears that the only 17" wheel with a 5x4.5" bolt pattern (5x114.3mm) was 17x9 with a -13 offset. That works out to be about 4.5" backspacing.
Click to expand...

Thanks for this! I’ll consider them 33s for lift purposes.
And wow your Google-fu is better than mine, you found that wheel info lightyears faster than me! Good to know.
I know for a fact that she’s not rubbing at all at full steering lockout, so I knew she wasn’t stock backspacing, but I could NOT figure out what I was actually running here.

macleanflood said:
Actual size is best for the speedometer charts. I have 35" BFGs and they're close but 34.5"... wife's JK has 35" Mickey's and they're 33" actual.

Looking at your Jeep I'd say it's pretty close to the ideal 3.75" backspacing...but best pull one off and measure.

You might be able to get away with some coil spring spacers and longer shocks...but it's best to make a longer term build plan.

-Mac
Click to expand...

So should I be looking to set up my suspension for 33s but get a speedometer gear for 32s?


Longer term build plan is the idea.

My goals are, sure, to be able to do some rock crawling in the summers for fun, nothing too extreme. But Threep is definitely a daily driver and needs to be able to handle going on the autoroute sometimes. KEY point being that 80% of my “daily driving” where I live would be considered by many to be snow wheeling. Mud and snow are my number one priorities (as Mud Season delivers some 2 foot deep mud holes on regular roads, worse on the unmaintained rd I live on)

When I lived here as a teenager I had a ZJ that came to me already lifted 4.5 inches on 34’s for 900 bucks because that’s what you could get back then. That rig took me pretty much anywhere.

Moving back, I got Threep but have to more or less build her out myself to be as capable.

Honestly tho I’ve been INCREDIBLY impressed by the fact that stock suspension on, I think we determined 33’s, is VERY nearly as capable as the ZJ with 4.5 lift. I’m guessing it’s the lighter weight of the TJ letting me float better (drove home today through several kilometers of snow that reached 2/3 of the way up the tire because it dared snow while I was at work lol)

I’m mostly running into snowpack in the wheel wells and me having to stop and clear them out to keep from locking up. Therefore the lift/looking into highline fenders/other misc upgrades.
 
Happienumber said:
Threep the Jeep came to me with 285/70/R17 tires installed. I’m trying to work out my lift kit needs and I’m running into conflicting information regarding what that size tire is in inches.
“Conversion” websites tell me it’s 32.7, I’ve seen people referring to them as 31’s, and as 33’s in posts. I measured them with a tape measure and the ones on the ground measure 31.5 and the spare measures 32 (I’m assuming due to tire pressure and weight on them)

This is how they fill out the wheel well on my otherwise stock 2006 TJ:

View attachment 592013

My speedometer is also OFF and I want to get a new speedometer gear but I can’t figure out what to classify my tires as.

Thank you for helping me out with such a silly noob question!

(Side question somewhat related: hours of research has not led me to answers about what the backspacing is on my wheels. A reverse image search FINALLY led me to them being Tuff T10 A.T. Which are no longer in production, but all the specs sites I can seem to find don’t list backspacing. Is there a better site to look at or a way to just measure it my own gotdang self? Thank you!!)
Click to expand...

Screw charts. Use an equation and round the number to the closest tooth count. No need to make guesses about tire size

Post in thread 'TJ Speed Gear Issues' https://wranglertjforum.com/threads/tj-speed-gear-issues.67779/post-1261642
 
Happienumber said:
Thanks for this! I’ll consider them 33s for lift purposes.
And wow your Google-fu is better than mine, you found that wheel info lightyears faster than me! Good to know.
I know for a fact that she’s not rubbing at all at full steering lockout, so I knew she wasn’t stock backspacing, but I could NOT figure out what I was actually running here.



So should I be looking to set up my suspension for 33s but get a speedometer gear for 32s?


Longer term build plan is the idea.

My goals are, sure, to be able to do some rock crawling in the summers for fun, nothing too extreme. But Threep is definitely a daily driver and needs to be able to handle going on the autoroute sometimes. KEY point being that 80% of my “daily driving” where I live would be considered by many to be snow wheeling. Mud and snow are my number one priorities (as Mud Season delivers some 2 foot deep mud holes on regular roads, worse on the unmaintained rd I live on)

When I lived here as a teenager I had a ZJ that came to me already lifted 4.5 inches on 34’s for 900 bucks because that’s what you could get back then. That rig took me pretty much anywhere.

Moving back, I got Threep but have to more or less build her out myself to be as capable.

Honestly tho I’ve been INCREDIBLY impressed by the fact that stock suspension on, I think we determined 33’s, is VERY nearly as capable as the ZJ with 4.5 lift. I’m guessing it’s the lighter weight of the TJ letting me float better (drove home today through several kilometers of snow that reached 2/3 of the way up the tire because it dared snow while I was at work lol)

I’m mostly running into snowpack in the wheel wells and me having to stop and clear them out to keep from locking up. Therefore the lift/looking into highline fenders/other misc upgrades.
Click to expand...

Measure the hub height x’s 2 to get the tire size. Get a Speedo gear for that size if you’re staying with that size. Then report back to discuss proper lift height..
 
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The first concept to understand is that there are nominal and actual tire sizes. A tire known as a 33" (nominal) is really only ever around 31.5" actual. Refer to it by it's nominal for least amount of confusing. A 285/70R17 is a nominal 32.7" tire which is close enough that it is known as a 33". It will only measure out to around 31.5", which is normal and expected. You are perfectly good to call what you have, "33s"

A good way to get a feel for it is to compare rev/mile numbers. A 285/70R17 will have almost the exact same rev per mile measurement that any 33x will have. They are for all intents and purposes the same height. Just like 265/70R17 is a 32, 265/65R17 is a 31, etc., even though the latter two are known as 31.5 and 30.5, the rounded-up number is close to the flotation or inch size equivalents.
 

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