How to make "1-piece" 4130 Chromoly Bars (Updated! 5/3/09)

T

Taylor_Davis

Member
or you can use a cutting wheel it works wonders it goes through like anything and you have alot of control because its like a grinder but straight
 
J

jzf88z

Member
Many riders seem to believe that all bars made of chromoly are lighter AND stronger than bars made of mild steel DOM tubing. This is not necessarily true:

According to www.onlinemetals.com, and www.aedmotorsports.com:

1. Chromoly is NOT lighter than mild steel. It is in fact heavier.
The weight per lineal foot of 1.25�outside diameter, 0.065�thick wall (Size you need for steering tube) of 4130 is 0.83 pounds, and for mild steel it is 0.81 pounds.
The weight per lineal foot of 0.875�outside diameter, 0.065�thick wall (Size you need for cross bar) of 4130 is 0.57 pounds, and for mild steel it is 0.52 pounds.

2. Chromoly is STRONGER than mild steel. Tensile strength of 4130 is 97,200 pounds and mild steel�s is 87,000 pounds. Chromoly about 12% stronger.

The tensile strength of 4130 can be further improved to up to 180,000 pounds by heat-treating it. Heat treating it would make chromoly more than twice as strong as mild steel.

Because chromoly is stronger, manufacturers can use thinner wall tubing so the bars will be lighter and still strong enough. For the crossbar, this is no problem. Worst case you have to shim your bar-ends. For the steering tube, a thinner wall means you will have to use a shim at the clamp or get a special clamp.

Before you order 4130 bars, ask your vendor how much their bars weigh, ask how thick the wall thickness of the chromoly is, and if they are heat-treated to make sure you get what you pay for. Inward Scooters has published the weight of their mild steel bars on their website for you to compare.
 
C

coryM

Member
OK first of all let me start off by stating that materials have less to do with strength than design.

now
Weight per foot doesnt mean anything as it is dependant on size. The strength to weight ratio of chromoly is unmatched by any other type of steel* in tubing aplications especially. (*excluding Ti and aluminums for now)

Bars of mild steel CAN be lighter, but then they will just be weaker...
They CAN also be stronger. But then they will be heavier...
This is only true if both sets of bars being compared are the exact same design.


btw
These are the weights of our unpainted OG bars in both the standard 1-1/4" steer tube and also the OS 1-3/8" bars.

1-1/4" steertube
24H x 24W = 2.70lbs or 44oz
18H x 16W = 1.80lbs or 29oz

OS 1-3/8" steertube
24H x 24W = 2.80lbs or 45oz
18H x 16W = 1.98lbs or 32oz
 
A

alexiorio

Member
Thanks for the information, Cory and Jp.
I never said there was anything wrong with steel.
I've felt Inward bars before, they're not much heavier than chromoly, AND they have that steel insert.
 
C

coryM

Member
^^ if your talking about the steertube on the bars, then there is no need for threads at all. Im pretty sure razor doesnt even thread their bars anymore. I think they used to. But its pointless...
 
A

alexiorio

Member
coryM said:
^^ if your talking about the steertube on the bars, then there is no need for threads at all. Im pretty sure razor doesnt even thread their bars anymore. I think they used to. But its pointless...
Click to expand...
Nope, the bars slide right over threaded forks.
And wait til tomorrow, I have 2 pairs of bars being welded right now, they're so clean :)
 
You must log in or register to reply here.
Top