Question about lift heights

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funmtbiker

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I have a question about lift heights. I have a stock 2005 Rubi LJ, with the stock ~31 inch. I'm planning to install either a curry or metal cloak lift on and then larger tires. From what I'm reading it sounds like you need a 3.5 inch lift kit to do 33s, and about 4.5-5 inches to do 35s. I'm probably going to keep it simple with 33s, but here is my question:

If I go from a 31 inch tall tire to a 33 inch tire, that tire is going to be only 2 inches taller, or 1 inch taller measured from the center of the axle. To put it another way: When parked, the fenders, etc will be 1 inch closer to the the top of a 33 inch tire vs a 31 inch tire. So why do you need 3.5 inches of lift to add 1 inch of tire as measured from the axle?


I'm not denying that it is what needs to be done, I'm just trying to wrap my head around why. Can someone explain like I'm 5?
 
As the lift height increases, so should the shock length so as to maintain at least the factory 4" of up travel. As the shock length increases, so does it's compressed length along with it's overall travel. The increased compressed length necessarily limits up travel.

Also, the articulating axle with the tire attached at the ends travels in an arc. As the shock travel increases, do does the arc that the tire. More arc needs more room.

Basically, there are multiple variables that are being juggled to arrive at these recommended lift heights for a tire size.
 
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funmtbiker said:
Not denying that it is what needs to be done, I'm just trying to wrap my head around why. Can someone explain like I'm 5?
Click to expand...
33" tires aren't only bigger around, they are wide so they hit the fender flares when you hit a bump among other things. The stock tires tuck nicely in the fenders. That alone is why the simple one inch bigger radius doesn't equal one inch lift.
 
pagrey said:
33" tires aren't only bigger around, they are wide so they hit the fender flares when you hit a bump among other things. The stock tires tuck nicely in the fenders. That alone is why the simple one inch bigger radius doesn't equal one inch lift.
Click to expand...
A larger tire isn't necessarily going to be wider. It will however, require additional backspacing, resulting in wider track width as you mentioned.
 
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You're right. You don't need 3.5" of lift for 33" tires.
However, you do need that much lift to get the most usable travel and articulation so that size tire can do the most good.
Think of the extremes. Lots of lift with little tires or big tires with no lift. Neither one works very well.
 
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funmtbiker said:
I have a question about lift heights. I have a stock 2005 Rubi LJ, with the stock ~31 inch. I'm planning to install either a curry or metal cloak lift on and then larger tires. From what I'm reading it sounds like you need a 3.5 inch lift kit to do 33s, and about 4.5-5 inches to do 35s. I'm probably going to keep it simple with 33s, but here is my question:

If I go from a 31 inch tall tire to a 33 inch tire, that tire is going to be only 2 inches taller, or 1 inch taller measured from the center of the axle. To put it another way: When parked, the fenders, etc will be 1 inch closer to the the top of a 33 inch tire vs a 31 inch tire. So why do you need 3.5 inches of lift to add 1 inch of tire as measured from the axle?


I'm not denying that it is what needs to be done, I'm just trying to wrap my head around why. Can someone explain like I'm 5?
Click to expand...
I don’t totally agree with all the answers, only partially.

The main reason is to maintain factory shock travel of 4”. If you don’t lift 3.5” for 33’s you will have to add more bumpstop to keep the tire out of the fender. That extra bumpstop will cut down on your shock travel.

A related reason is so the tire doesn’t hit the rear of the fender (not flare) when tires are turned and articulated (stuffed). Again, to do that at a lower lift, you’ll have to add more bumpstop, sacrificing valuable shock travel, giving you less than stock travel.
 
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LONGJP2 said:
You're right. You don't need 3.5" of lift for 33" tires.
However, you do need that much lift to get the most usable travel and articulation so that size tire can do the most good.
Think of the extremes. Lots of lift with little tires or big tires with no lift. Neither one works very well.
Click to expand...
This is the only answer that makes sense to me. With a 1 inch more radius ( and assuming the same tire width), everything is going to be one inch closer. So it makes no sense to me that you need 3.5 inches of lift for it to fit even under full flex. But basically you need that much lift to make any use of the taller tire.
 
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JMT said:
I don’t totally agree with all the answers, only partially.

The main reason is to maintain factory shock travel of 4”. If you don’t lift 3.5” for 33’s you will have to add more bumpstop to keep the tire out of the fender. That extra bumpstop will cut down on your shock travel.

A related reason is so the tire doesn’t hit the rear of the fender (not flare) when tires are turned and articulated (stuffed). Again, to do that at a lower lift, you’ll have to add more bumpstop, sacrificing valuable shock travel, giving you less than stock travel.
Click to expand...

Bump stops should be set to prevent contact. Where the tire contacts the fender doesn't depend on lift height. Longer shocks (more lift) need more bumpstop.

More lift needing less bumpstop only applies to mall crawlers that don't use full travel.
 
funmtbiker said:
This is the only answer that makes sense to me. With a 1 inch more radius ( and assuming the same tire width), everything is going to be one inch closer. So it makes no sense to me that you need 3.5 inches of lift for it to fit even under full flex. But basically you need that much lift to make any use of the taller tire.
Click to expand...
You aren't understanding what longer shocks do to the travels.
 
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@funmtbiker
Not just 1" taller.
The tire is also wider (horizontal diameter (not tread width). When you turn (flexed or not) it can hit the control arms, frame, sway bar, etc. To counter this, most will push the tire out farther with spacers or offset wheels. Now your width from center of vehicle is longer, which makes the articulation arc bigger, which in turn requires more height for clearance.
Just empty every pocket.
 
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So if you can put 31,s on a 2inch lift or on no lift you should be able to get 33,s on a 2inch lift? Not saying just asking because not all tyres get wider as they get higher, so I was told the other day?
 
funmtbiker said:
This is the only answer that makes sense to me. With a 1 inch more radius ( and assuming the same tire width), everything is going to be one inch closer. So it makes no sense to me that you need 3.5 inches of lift for it to fit even under full flex. But basically you need that much lift to make any use of the taller tire.
Click to expand...
Focus on lift spring length being determined by the longer shock as opposed to the inverse. What spring do I need to fully utilize the travel of this longer shock?
 
Fishtaco said:
So if you can put 31,s on a 2inch lift or on no lift you should be able to get 33,s on a 2inch lift? Not saying just asking because not all tyres get wider as they get higher, so I was told the other day?
Click to expand...
shocks...
 
@Fishtaco

LONGJP2 said:
You're right. You don't need 3.5" of lift for 33" tires. Yes, you can put 33s on 2" of lift.
However, you do need that much lift to get the most usable travel and articulation so that size tire can do the most good.
Think of the extremes. Lots of lift with little tires or big tires with no lift. Neither one works very well.
Click to expand...
;)
 
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