Much difference between 30's and 31's?

Jeff - are you anywhere near NJ? Where are you?

Bill, his Jeep came with 3.07 gearing so it can't be a 4 cylinder. He regeared it to 4.1 according to his post. I think the 31s will be a better match for his gearing, although 32s would probably be even better.

---------------------------------------------------- Del Rawlins- del@_kills_spammers_rawlinsbrothers.org Remove _kills_spammers_ to reply via email. Unofficial Bearhawk FAQ website:

It isn't quite that simple because of the differences between nominal and actual sizes of tires. A lot of 30s are really only 29 or 29.5 inches tall, whereas most 31s are just about right on 31 inches. And while that might not make a very big difference in clearance, it will have a bigger impact on his RPM at cruising speeds. With his 4.10 gearing a 31" tire would probably be a better choice, although I would personally want to go for 32s, since that gives the same overall ratio with 4.10 that I have with 30 inch tires and 3.73 gearing, which is a good all around combination.

Whether or not it is worth switching is something that nobody here can answer for him.

---------------------------------------------------- Del Rawlins- del@_kills_spammers_rawlinsbrothers.org Remove _kills_spammers_ to reply via email. Unofficial Bearhawk FAQ website:

Moving from 30" to 31" is only a 3% change, or about 100 RPM at 65 MPH....not worth doing in my opinion.

Walt Johnson

99 TJ

True Del, but as I recall, he was talking about switching from BFG AT

30's to BFG MT 31's. That's going to make the manufacturer variances in sizes pretty much a wash IMO.

Dave

I just misundertood that part of your post, thinking that you believed his Jeep to be a 2.5L. Actually I don't really care what he does with his 30 inchers, I was just saying that 31" would be a step in the right direction for his engine and gearing. My real opinion is that if he had bought a Jeep with 3.73s to begin with he would have been a lot happier waiting until it is convenient for him to lift the Jeep and install the tires he really wants. He got to where he is now by half measures ( first with the 30s, then the regear) and another half measure will still be sub optimal, but he'd at least be happier with the 31s than he is with the 30s. Whether that is enough to justify the expense is a question for the man in the mirror.

It is questions like this that make me glad I custom ordered my Jeep the way I wanted it, or at least as close as Daimler would build for me. With 3.73 gears, 30" tires, a truetrac in front and a trashlock/d35c(rap) in the rear, it is a reasonably well balanced rig that I am happy driving on and off road.

At some point I'd like to upgrade to 32" tires, regear to 4.10, install an electrac equipped D44 and a 2-3" lift but doing any one of those mods without the others would turn the Jeep into something I wouldn't be happy with. So I will wait until I can do them all at once. All that because I want ABS, which Daimler won't give you with the D44, although the aftermarket will at 4 times the price (plus shipping to Alaska).

---------------------------------------------------- Del Rawlins- del@_kills_spammers_rawlinsbrothers.org Remove _kills_spammers_ to reply via email. Unofficial Bearhawk FAQ website:

You can see that kind of thing even with the same manufacturer. Goodyear's 30s are only 29.5" tall, while their 31s are really 31s.

---------------------------------------------------- Del Rawlins- del@_kills_spammers_rawlinsbrothers.org Remove _kills_spammers_ to reply via email. Unofficial Bearhawk FAQ website:

Just checked Goodyears site for specs on their MT tires:

31X10.50R15LT is 30.7 30X9.50R15LT is 29.7

But I do understand what you're driving at, and it's true sometimes.

Dave

Hi Jeff,

regeared it to 4.1 according to his post. I think the 31s will be a better match for his gearing, although 32s would probably be even better.