Safe Cruising Speed for 5.38 gear Roxors

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Parabellum2013

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Hello, all. I'm looking into getting a roxor and making it street legal here in michigan as a somewhat daily driver. I hear the newer production Roxors switched to a 5.38 gear ratio from the older 3.73s and since the RPMs will higher from my understanding I was curious what a reliable cruising speed over a long trip would be without causing to much stress on the motor and such. I'd love to be able to drive the roxor to the UP to ride trails and camp which would be a several hundred mile ride and I'd like to be able to cruise at least 55 mph to get there without blowing up the roxor. Thanks for the help!
 
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WillysJeep

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Based on your use I would highly recommend the 3.73. I have 5.38 and at 55 she is turning very close to 3000 rpm. I have been told that redline is 3200.
 
CJ2Rox

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Hello, all. I'm looking into getting a roxor and making it street legal here in michigan as a somewhat daily driver. I hear the newer production Roxors switched to a 5.38 gear ratio from the older 3.73s and since the RPMs will higher from my understanding I was curious what a reliable cruising speed over a long trip would be without causing to much stress on the motor and such. I'd love to be able to drive the roxor to the UP to ride trails and camp which would be a several hundred mile ride and I'd like to be able to cruise at least 55 mph to get there without blowing up the roxor. Thanks for the help!
I just had my 2020 tuned and I would say over 60 and I'm not comfortable. The Rox engine can handle it but around bigger vehicle etc is interesting
 
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Parabellum2013

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Based on your use I would highly recommend the 3.73. I have 5.38 and at 55 she is turning very close to 3000 rpm. I have been told that redline is 3200.
I had a feeling that would be the case, I'm not opposed to buying a used one with the 3.73s, but the used market for these is pretty slim pickings. Sound like my best bet would be a gear swap, ontherox only has 4.10s for their tallest gears, but I'd think even that would be an improvement
 
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Parabellum2013

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I just had my 2020 tuned and I would say over 60 and I'm not comfortable. The Rox engine can handle it but around bigger vehicle etc is interesting
Does it not feel stable?
 
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I use my Roxors as daily drivers around Phoenix and on highways on weekends. With the 3.73 and 255/85/16 (33") tires rpms are around 2200 to 2400 between 60 and 65 mph. With stock tires, it would be anoit 10% higher rpms if I remember correctly.
Even with the big tires, the Roxor is stable at 60, even 65 is ok on straight roads (With a shock upgrade). Personally, I think the Roxor is right at home up to 60 mph (with a shock upgrade).
With the 5.38, you will need big tires to keep the engine in a reasonable range.
 
CJ2Rox

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Does it not feel stable?
Aside with my air pressure is at 20 and have stock shocks it did alright. I have shocks coming and will be putting in more air. The shocks that come with these are horrible. It rides great
 
txroadkill

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I have a set of take out 3.73s including the carriers. Also have front and rear axle shafts. pay the cost of shipping and I’ll send you the gears and carriers.
 
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I have a set of take out 3.73s including the carriers. Also have front and rear axle shafts. pay the cost of shipping and I’ll send you the gears and carriers.
Sounds like you changed out your axle shafts? Did you convert to 30 spline? What axle shafts did you go with? Thanks


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I went 30 spline with the kits from on the Rox. The front is u joints.
 
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I've had mine to 75 to mph before with no windshield. Felt fine, would go faster if it weren't cold.
 
CJ2Rox

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I've had mine to 75 to mph before with no windshield. Felt fine, would go faster if it weren't cold.
Just remember where the red line is at. I heard just over 3000
 
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Just remember where the red line is at. I heard just over 3000
Seems like nobody really knows. Unfortunately a bunch of info on these machines is just speculation
 
CJ2Rox

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Haven't figured out how to pull up old chats here

Screenshot_20210225-144808_DuckDuckGo.jpg
 
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We need a stickied thread with information like this.

I wonder what speed I'll hit at 2500 with 35s. I'm about to install the long travel kit from max. Hopefully it will be done before April with the longer driveshafts and tires and everything
 
txroadkill

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We need a stickied thread with information like this.

I wonder what speed I'll hit at 2500 with 35s. I'm about to install the long travel kit from max. Hopefully it will be done before April with the longer driveshafts and tires and everything
Gear Ratio Calculator

1-3.77
2-2.08
3-1.37
4-1.00
5-.78
rev-3.52

t case low 2.46

plug them numbers in that calc and use whatever tire size you want. Just remember actual mounted height is likely to be less than advertised sidewall height. for instance a 35-12.5–15 might only be 34.5” tall. Shouldn‘t make much of a difference maybe a couple hundred rpm But you’ll be close to ballpark. If using a metric tire then size calcs should get you pretty close.
 
Cloud

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Gear Ratio Calculator

1-3.77
2-2.08
3-1.37
4-1.00
5-.78
rev-3.52

t case low 2.46

plug them numbers in that calc and use whatever tire size you want. Just remember actual mounted height is likely to be less than advertised sidewall height. for instance a 35-12.5–15 might only be 34.5” tall. Shouldn‘t make much of a difference maybe a couple hundred rpm But you’ll be close to ballpark. If using a metric tire then size calcs should get you pretty close.
That is one reason I run nittos in the Toyota. They give actual tire size. Makes calibrating the speedo easier.

Interco seems to give you the actual size in the product description.

Thanks for the numbers!
 
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I have an update for you, I was mistaken and did not realize it until recently.

My max speed with a stock roxor with 5.38:1 diffs and stock 29" tires, engine screaming, was 68mph. And I mean the thing was SCREAMING. I would never cruise with such high engine speeds. Apparently my speedo was already adjusted for 35s and I didn't know it, neither did the guy that tuned it so maybe mine was originally setup for 3.73 ratio and nobody changed that ratio in the computer, don't know, don't care. 68 max gps verified. The engine is working uncomfortably hard at 45mph with little tires on it.

Now with tires measuring 34.25" diameter I've not topped it out, but it's about 2550 rpm at 55mph. I've had it to 65mph and I was comfortable with the engine sounds and rpm. I'll let it loose later and see what she'll do
 
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Parabellum2013

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I have an update for you, I was mistaken and did not realize it until recently.

My max speed with a stock roxor with 5.38:1 diffs and stock 29" tires, engine screaming, was 68mph. And I mean the thing was SCREAMING. I would never cruise with such high engine speeds. Apparently my speedo was already adjusted for 35s and I didn't know it, neither did the guy that tuned it so maybe mine was originally setup for 3.73 ratio and nobody changed that ratio in the computer, don't know, don't care. 68 max gps verified. The engine is working uncomfortably hard at 45mph with little tires on it.

Now with tires measuring 34.25" diameter I've not topped it out, but it's about 2550 rpm at 55mph. I've had it to 65mph and I was comfortable with the engine sounds and rpm. I'll let it loose later and see what she'll do
Nice, thanks for the update. Do the 35s fit with the stock suspension or do you need a lift to for them?
 
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