Help me figure out my axle length

[lacofdfireman]

Getting ready to start a build on another trailer and to me the hardest part is figuring out my axle length to order. I’m a little gun shy this time because last time I was told to build the trailer frame first then order the axle. Well somehow I screwed it up and my axle was to short so I had to order another one. About a $200 mistake. This time I want to order my axle first and build the trailer frame around my axle. So here is what my needs are.

My trailer frame width will be 5ft to outsides of frame rails
I want a 3500lb spring axle with brakes
I will be using my stock Jeep Wheels so will also need to order 2” spacers so I can run stock wheel caps

I believe my spring perch centers should be 60” because I want a 60” wide trailer frame but not sure how much I’d need to add for Hubface with electric brakes. I wish there was a axle calculator out there where you could just put in the type of axle you want and the trailer frame width and it would figure it out for ya.


Also where is the best place to order a 2” spacer for my jeep Wheels? I know my jeeps wheel center hole is to small to fit over the axle

So with those parameters what size do you think I’d need?

 

[ottsville]

If your frame is 60" outside to outside then you don't want your perches 60" on center. That would put your spring mount outside of the frame by half the width of the spring mounts. You need to deduct 1/2 the width of your spring mounts on each side from outside width of your trailer to get center for your perches.

You shouldn't need to know the width of the electric brakes. Lay a straight edge across the back side of your tire wheel combo. Measure down to the face where the wheel mates to the hub. Note that depth. Add whatever distance you want between your tire and frame to that. Multiply by 2, add 60 for the trailer width and subtract 4 for your spacers.

Etrailer's website has lots of good information about trailer stuff, including how to measure axles.

 

[PhulesAU]

What year Jeep? The 5x4.5 bolt pattern is common for many trailers. I would do all I could to get correct hubs and NOT use a spacer.

 

[lacofdfireman]

If your frame is 60" outside to outside then you don't want your perches 60" on center. That would put your spring mount outside of the frame by half the width of the spring mounts. You need to deduct 1/2 the width of your spring mounts on each side from outside width of your trailer to get center for your perches.

You shouldn't need to know the width of the electric brakes. Lay a straight edge across the back side of your tire wheel combo. Measure down to the face where the wheel mates to the hub. Note that depth. Add whatever distance you want between your tire and frame to that. Multiply by 2, add 60 for the trailer width and subtract 4 for your spacers.

Etrailer's website has lots of good information about trailer stuff, including how to measure axles.

Ok so let’s use this wheel as an example. When I order my axle the company wants to know my hub face measurement. So my wheel hub face measurement is 8”.

Wheel Hub face measurement is 8”
Distance from tire to frame I’m thinking 2”

So 8” plus 2” by both sides is 4” so we are at 12” add in 60” for the trailer and we are at 72” then minus my 2 “ spacers on each side and I come up with a 68” hub face. Does that seem correct or did I do something wrong with my math?

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[lacofdfireman]

What year Jeep? The 5x4.5 bolt pattern is common for many trailers. I would do all I could to get correct hubs and NOT use a spacer.

My Jeep is a 2012 Rubicon. And spacers are not a choice as the center hub on a wheel isn’t wide enough to fit over a 3500lb trailer axle without enlarging the wheels center hub hole. Jeep Wheels are hubcentric. Not lugcentric.


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[dstock]

My Jeep is a 2012 Rubicon. And spacers are not a choice as the center hub on a wheel isn’t wide enough to fit over a 3500lb trailer axle without enlarging the wheels center hub hole. Jeep Wheels are hubcentric. Not lugcentric.


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Exactly correct! I got my spacers from Adaptit USA they were great to deal with and I haven't had any issues them.

 

[lacofdfireman]

If your frame is 60" outside to outside then you don't want your perches 60" on center. That would put your spring mount outside of the frame by half the width of the spring mounts. You need to deduct 1/2 the width of your spring mounts on each side from outside width of your trailer to get center for your perches.

You shouldn't need to know the width of the electric brakes. Lay a straight edge across the back side of your tire wheel combo. Measure down to the face where the wheel mates to the hub. Note that depth. Add whatever distance you want between your tire and frame to that. Multiply by 2, add 60 for the trailer width and subtract 4 for your spacers.

Etrailer's website has lots of good information about trailer stuff, including how to measure axles.

Ok so let’s use this wheel as an example. When I order my axle the company wants to know my hub face measurement. So my wheel hub face measurement is 8”.

Wheel Hub face measurement is 8”
Distance from tire to frame I’m thinking 2”

So 8” plus 2” by both sides is 4” so we are at 12” add in 60” for the trailer and we are at 72” then minus my 2 “ spacers on each side and I come up with a 68” hub face. Does that seem correct or did I do something wrong with my math?

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Anyone know if my math on this axle seem right? I’d like to get this ordered soon so I can get building.




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[dstock]

Anyone know if my math on this axle seem right? I’d like to get this ordered soon so I can get building.

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Personally I would build the frame first but since you prefer to order the axle first, I would tape the potential frame out on the garage floor and check your measurements. You can position the wheels and get a visual of how everything will line up.

Frankly, I don't think anyone here wants to be responsible for telling you your measurements are correct and then have something be wrong. When I did my build, I fully sweated the axle order so I totally understand where you are coming from. I put my wheels under my trailer even when I thought I had the measurements correct and triple checked everything.

Just my 2 cents! Hope it's helpful.

 

[villageidiot327]

let me take a stab at it.....

you have 8" from hub to the tire edge, plus 2" to trailer body =10" past the frame on each side.
frame width of 60"

hub to hub of 80" is my math. deduct what you want for hub spacers from that. 2" spacers deduct 4" off the hub to hub etc. most require a 1.5" spacer to clear the studs or else you have to cut studs.

if frame is 60" and you want to use 2" wide material, spring perches should be on a 58" center to center.

 

[lacofdfireman]

let me take a stab at it.....

you have 8" from hub to the tire edge, plus 2" to trailer body =10" past the frame on each side.
frame width of 60"

hub to hub of 80" is my math. deduct what you want for hub spacers from that. 2" spacers deduct 4" off the hub to hub etc. most require a 1.5" spacer to clear the studs or else you have to cut studs.

if frame is 60" and you want to use 2" wide material, spring perches should be on a 58" center to center.

So I don’t know why this is so confusing to me. I have a hard time wrapping my head around hub face when I’m thinking of my drum brakes. So is the actual axle hub face from the lug side of the axle drum to drum? Or is the axle hub face where you mount the drum to? Does that make sense? I think that’s what’s throwing me for a loop. Just wondering if I need to add anything for the drum brake face since that’s actually where I’ll mount the spacers to.

Does this even make any sense? And after looking at it my math is wrong. Also the axle company I’ve called said they don’t care about spring perch distance. They m want hub face only and said you weld on your own spring perches.


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[villageidiot327]

So I don’t know why this is so confusing to me. I have a hard time wrapping my head around hub face when I’m thinking of my drum brakes. So is the actual axle hub face from the lug side of the axle drum to drum? Or is the axle hub face where you mount the drum to? Does that make sense? I think that’s what’s throwing me for a loop. Just wondering if I need to add anything for the drum brake face since that’s actually where I’ll mount the spacers to.

Does this even make any sense? And after looking at it my math is wrong. Also the axle company I’ve called said they don’t care about spring perch distance. They m want hub face only and said you weld on your own spring perches.


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hub face is from the flat part of the hub that the WHEEL SITS AGAINST to the other sides flat part.

also known as wheel mounting surface.

doesn't matter if you have drum brakes, disc brakes, or no brakes, hub face is from wheel mount surface to wheel mount surface. IE: the face of the hub.

 

[lacofdfireman]

So I don’t know why this is so confusing to me. I have a hard time wrapping my head around hub face when I’m thinking of my drum brakes. So is the actual axle hub face from the lug side of the axle drum to drum? Or is the axle hub face where you mount the drum to? Does that make sense? I think that’s what’s throwing me for a loop. Just wondering if I need to add anything for the drum brake face since that’s actually where I’ll mount the spacers to.

Does this even make any sense? And after looking at it my math is wrong. Also the axle company I’ve called said they don’t care about spring perch distance. They m want hub face only and said you weld on your own spring perches.


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hub face is from the flat part of the hub that the WHEEL SITS AGAINST to the other sides flat part.

also known as wheel mounting surface.

doesn't matter if you have drum brakes, disc brakes, or no brakes, hub face is from wheel mount surface to wheel mount surface. IE: the face of the hub.

Ok perfect. This was what I couldn’t wrap my head around. I’ve seen so many photos of different photos showing hub face, brake mounting surface, spring centers etc that I was confused. Now I know if I order an axle with brakes they are talking about the hub face of the drum. So that should make my math easy.

Trailer width 60”
Spring centers 58”
Wheel mount surface to edge of tire is 8”
2” for wheel to frame clearance
2” for wheel spacers

Now the math

58” spring perch centers
Add 8” per side for wheel mount surface to brake drum hubface
Add 2” per side for wheel clearance.
Subtract 2” per side for wheel spacers

So 58” (spring center) + 16” (wheel mount surface to tire edge)+ 4” (tire to trailer clearance) =78” Brake drum hubface. Then 78”-4”(wheel spacers) = 74” adjusted hubface.

So I should be ordering an axle with a 58” spring center and 74” hub face.

This should be the correct measurement for my trailer width.

Also my Jeep wheel bolt pattern is a 5 on 5 bolt pattern and I think I’ll order the axle the same way. So my wheel spacers will be a 5 on 5 to 5 on 5 instead of the standard trailer axle bolt pattern of 5 on 4.5.


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[villageidiot327]

Ok perfect. This was what I couldn’t wrap my head around. I’ve seen so many photos of different photos showing hub face, brake mounting surface, spring centers etc that I was confused. Now I know if I order an axle with brakes they are talking about the hub face of the drum. So that should make my math easy.

Trailer width 60”
Spring centers 58”
Wheel mount surface to edge of tire is 8”
2” for wheel to frame clearance
2” for wheel spacers

Now the math

58” spring perch centers
Add 8” per side for wheel mount surface to brake drum hubface
Add 2” per side for wheel clearance.
Subtract 2” per side for wheel spacers

So 58” (spring center) + 16” (wheel mount surface to tire edge)+ 4” (tire to trailer clearance) =78” Brake drum hubface. Then 78”-4”(wheel spacers) = 74” adjusted hubface.

So I should be ordering an axle with a 58” spring center and 74” hub face.

This should be the correct measurement for my trailer width.

Also my Jeep wheel bolt pattern is a 5 on 5 bolt pattern and I think I’ll order the axle the same way. So my wheel spacers will be a 5 on 5 to 5 on 5 instead of the standard trailer axle bolt pattern of 5 on 4.5.


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you're close

you need axle width enough to go the whole width of the trailer, not just spring center.

60" (trailer width), + 16" (WMS to tire edge) +4" (clearance) = 80" axle. 80"-4" (spacers) + 76" adjusted hub face/axle length.

the spring perch distance is irrelevant to the axle unless theyre welding them on.

 

[lacofdfireman]

Ok perfect. This was what I couldn’t wrap my head around. I’ve seen so many photos of different photos showing hub face, brake mounting surface, spring centers etc that I was confused. Now I know if I order an axle with brakes they are talking about the hub face of the drum. So that should make my math easy.

Trailer width 60”
Spring centers 58”
Wheel mount surface to edge of tire is 8”
2” for wheel to frame clearance
2” for wheel spacers

Now the math

58” spring perch centers
Add 8” per side for wheel mount surface to brake drum hubface
Add 2” per side for wheel clearance.
Subtract 2” per side for wheel spacers

So 58” (spring center) + 16” (wheel mount surface to tire edge)+ 4” (tire to trailer clearance) =78” Brake drum hubface. Then 78”-4”(wheel spacers) = 74” adjusted hubface.

So I should be ordering an axle with a 58” spring center and 74” hub face.

This should be the correct measurement for my trailer width.

Also my Jeep wheel bolt pattern is a 5 on 5 bolt pattern and I think I’ll order the axle the same way. So my wheel spacers will be a 5 on 5 to 5 on 5 instead of the standard trailer axle bolt pattern of 5 on 4.5.


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you're close

you need axle width enough to go the whole width of the trailer, not just spring center.

60" (trailer width), + 16" (WMS to tire edge) +4" (clearance) = 80" axle. 80"-4" (spacers) + 76" adjusted hub face/axle length.

the spring perch distance is irrelevant to the axle unless theyre welding them on.

Thanks so much for the axle education. This is exactly what I was hoping for. But I do have one last question.

As far as the spring perches being welded on or you welding them yourself why is the calculation different? Example: If I was going to order an axle with the spring perches already welded on I’d want a 58” spring center for a 60” trailer. But according to your math if I ordered an axle without the spring perch’s welded on I’d want a 60” axle. So just wondering why my math is off 2” just because a perch was welded on vs. not welded already. I’m confused. I thought I had this figured out.

Sorry for the stupid questions. I owe ya big time for this.

Hopefully maybe this post will help someone in the future also.


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[villageidiot327]

Thanks so much for the axle education. This is exactly what I was hoping for. But I do have one last question.

As far as the spring perches being welded on or you welding them yourself why is the calculation different? Example: If I was going to order an axle with the spring perches already welded on I’d want a 58” spring center for a 60” trailer. But according to your math if I ordered an axle without the spring perch’s welded on I’d want a 60” axle. So just wondering why my math is off 2” just because a perch was welded on vs. not welded already. I’m confused. I thought I had this figured out.

Sorry for the stupid questions. I owe ya big time for this.

Hopefully maybe this post will help someone in the future also.


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Simple misunderstanding. No matter what axle you order (for a 60” wide frame) spring perches are going to be welded 58” on center. (Assuming 2” frame material)

BUT!

You need 60” of axle length to clear the frame, not just the length between spring centers. You just used the spring center length instead of frame width in your calculation.