31" speedo

T0ADMAN · 05-13-2009, 05:21 PM

So, I think I've decided to get the 31x10.5 BFG AT KOs for my Jeep.
It's mostly a daily driver, but I hope to get into wheelin' in the future.

I figure I can put these tires on my stock Jeep (since it needs tires very soon) and then look into getting a small lift sometime in the future.

My Jeep currently as 30" BFGs on it. Is a 1" difference going to make any noticeable difference in my speedo/odom? Is this something worth trying to correct, or should I just let it go and be careful not to push the speed limit?

PS, I've been toying with the idea of getting the RC 2.5" lift right away and perhaps bigger/different tires, so if anyone felt the urge to give some opinons on that, I wouldn't mind either.

**GOLENJEEPTJ** · 05-13-2009, 05:31 PM

You can get a gear now or get one later after larger tires.Problem is they just keep going up in price.I would decide how it's going to sit with lift and tires and get a gear then.

Jeeeps · 05-14-2009, 06:58 AM

Quote:

Originally Posted by T0ADMAN

So, I think I've decided to get the 31x10.5 BFG AT KOs for my Jeep.
It's mostly a daily driver, but I hope to get into wheelin' in the future.

I figure I can put these tires on my stock Jeep (since it needs tires very soon) and then look into getting a small lift sometime in the future.

My Jeep currently as 30" BFGs on it. Is a 1" difference going to make any noticeable difference in my speedo/odom? Is this something worth trying to correct, or should I just let it go and be careful not to push the speed limit?

PS, I've been toying with the idea of getting the RC 2.5" lift right away and perhaps bigger/different tires, so if anyone felt the urge to give some opinons on that, I wouldn't mind either.

You'll get maybe a 5% difference in the speedo

cheers

Kraxen · 05-14-2009, 07:03 AM

im running 33s and my speedo is slow by 5 mph. and that throws off the mileage some too

jersey1972fj40 · 05-14-2009, 07:31 AM

get the rc lift and the 32 or 33's for an additional 300 bucks it is well worth it

**TheBoogieman** · 05-14-2009, 07:35 AM

Tires aren't cheap.Do it once.Get the lift,33's and if you have 3.73 gears you'll be fine.Then change the speedo gear.

Florida_Model · 05-14-2009, 07:40 AM

what tooth gear do you need? im jumping from 31s to 32s and right now my speedo is faster than my actual speed? previous owner must have downgraded before selling to dealership?

**Wheelin98TJ** · 05-14-2009, 07:49 AM

Many stock TJs actually have a more accurate speedo with 31" tires.

Green99Sport · 05-14-2009, 07:51 AM

Quote:

Originally Posted by Wheelin98TJ

Many stock TJs actually have a more accurate speedo with 31" tires.

x2, my speedo reads the same as a GPS with 31s.

bigred33 · 05-14-2009, 08:27 AM

I've got 32s on mine and am about 4-5mph off according to one of those road signs that flash how fast you're going.

emev0l · 05-14-2009, 08:28 AM

When I was running 31's it was very close maybe 1 or 2 miles off, now will 33's it's 5 or 6 miles off.

I wouldn't change the speedo gear for 31's, change it for 33's while your doing the SYE, and anything bigger is a must if it's a DD.

**Unlimited04** · 05-14-2009, 08:29 AM

Quote:

Originally Posted by Wheelin98TJ

Many stock TJs actually have a more accurate speedo with 31" tires.

x2. mine's dead nuts on with 31s. verified with radar speed sign & GPS at many different speeds.

**adoni77** · 05-14-2009, 08:34 AM

Quote:

Originally Posted by emev0l

When I was running 31's it was very close maybe 1 or 2 miles off, now will 33's it's 5 or 6 miles off.

I wouldn't change the gear for 31's, change it for 33's while your doing the SYE, and anything bigger is a must if it's a DD.

Sorry I'm still new to all this.. Mine is running 33's and is off. When you say change the gear, thats just to fix the Speedo or you talking actual gear ratio? Mine is a DD. Thankx for the newbie info.. lol

**JohnyPro** · 05-14-2009, 08:48 AM

31s make the speedo truly accurate for my LJ! Get the RC lift, I'm purchasing one at the end of the school year

**TheBoogieman** · 05-14-2009, 10:02 AM

Quote:

Originally Posted by adoni77

Sorry I'm still new to all this.. Mine is running 33's and is off. When you say change the gear, thats just to fix the Speedo or you talking actual gear ratio? Mine is a DD. Thankx for the newbie info.. lol

That's just to make the speedometer acurate with larger tires.
http://www.stu-offroad.com/engine/speedo/speed1.htm