View Full Version : Material for Motorcycle Axle?

05-02-2009, 04:11 PM
One of my customers bought an ebay front end for his bike,unfortunately it didnt come with a front axle.This is a hidden type axle setup,and its proving to be an oddball size. Would be alot easier just to make what he needs rather than scrounging....what material is best for this?

05-02-2009, 04:14 PM

05-02-2009, 04:18 PM
Who made the front end?

05-02-2009, 04:27 PM
I'm no expert, but I would guess 4130. I don't know too much about motorcycles, but we used to use 4130 for all of the FSAE axles and the Baja car king pins/stub axles. The FSAE vehicle went to some exotic stainless alloys and nickel super alloys for the axles. PITA to machine, but they can be made smaller and lighter that way.

I guess stress proof makes sense - the front axle on the motorcycle doesn't have to transmit any torque...

05-02-2009, 04:41 PM
Hidden axle: Off ebay.??

Probably a inverted tube front end from Midwest. (Ultima brand??)
Good news is they are $30 or so.. bad news is they made several different designs of them.

The axle on the front end here, seems it has a bearing preload adjustment on it, then it all bolts up into the "bullets" shaped covers on the lower legs.

The newest sales flier, the triple trees are like $125 (117x237), and the tubes' and sliders (117x236) are $299

THE crane cams hi-fire single fire ignition kit is a good deal this month too at dlr cost of $164.. all tuning parameters are adjustable.

If you can provide Fork part numbers I will get a part # for the axle Monday for you through my rep.

(I gave $750 for one of these just a year or two back)

05-02-2009, 05:19 PM
THE crane cams hi-fire single fire ignition kit is a good deal this month too at dlr cost of $164.. all tuning parameters are adjustable.

Quick sidebar - Crane Cams has been bought by S&S so at least the bike parts will continue. Dunno about the auto stuff.

Anyway - a front axle is nothing to experiment with. I'd rather have swine flu than build one, but then I've stood over the open graves of a couple friends who broke front axles. There's a lot of science that goes into making them strong.

I have a rear axle from my Harley in the garage - I removed and replaced it when I spun a bearing back there. It looks fine but I'm not going to risk it. If at all possible get a factory-built axle. If not, crack the books and see what kinds of treatment and metal is appropriate.

05-02-2009, 05:35 PM
I built an axle for my former Harley Shovelhead motorcycle. I used a 3/4" 4130 rod. I threaded one end to 3/4-16 and welded a 1-1/4" stainless steel nut on the other end. It worked perfectly for the 15 years I owned the bike. I made it because I added some heavy 1/4" thick stainless steel washers on the outside of the swing arm to protect it. That caused the need for a 1/2" longer axle. I don't think you would need anything stronger or harder than 4130.

05-02-2009, 07:49 PM
Probably a inverted tube front end from Midwest. (Ultima brand??)

Hmmm...I swear he told me Mid Usa. I have no idea if its inverted or not,havent seen anything other than the caps for the lowers. He DID tell me he's already ordered 2 axles from they're part #'s and neither did the job.I'll agree an axle is nothing to play with,and I've mixed emotions about the whole setup. This is mainly due to the fact that he (and alot of others) buy this stuff from ebay,many missing pieces,and then come to me to sort out the mess. As much as I'd like to tell him to stick it where the sun wont shine,he's been a good customer,and I'd like to follow thru. I've done alot of bike stuff lately,got a BDL drive in the shop now re-doing races,but am not very comfortable with this axle thing.....is this a liability issue? If so I dont think I need to be involved,we're a reputable shop with a good customer base,and I def dont want to endanger any of that.

05-02-2009, 08:25 PM
Proprietary axle fits that front end. It has a flat flange on one end and a nut on the other.

They come with the front ends normally, Have "customer" go through the supplier off ebay. Probably one came with the front end, laying in the corner and didnt' get shipped with it.

05-02-2009, 10:06 PM
4130 will do the job. It has the right combination of high yield strength and resistance to fatigue cracking. That is why it is used in the most critical parts of aircraft where failure is not an option such as wing spars, landing gear struts, control columns and engine mounts.

05-02-2009, 11:07 PM
As said before 4130 is a good choice, no doubt. I myself prefer the 4150 heat treated, or the 4150 heat treated,stress relieved. It has super strength, super wear resistance, plenty hard enough, and dosen't "brittle up" badly when welded on. I promise you that the original was probably 1118 since it machines easyer than the old common1018 carbon steel. Any chrome-molly is superior to any carbon steel. I make a lot of stuff out of 4150, sometimes a little tuff to machine. But in the end, makes a better part. I have seen chrome molly hold up long after the others failed.

Also, new member here, my first comment in the forums. New to computers too. :D

Your friend, Doggie

05-02-2009, 11:35 PM

I used 3/4" O-1 drill rod. Fit my bearings nice and threaded nice as well.


05-03-2009, 12:52 AM
Did a little research looking through catalogs I have, and on the net, and have found that most are made out of 4140.

Here's a link to a $6,300 Baker wide tire kit which also comes with a 4140 axle, just as an example that it's not a mickey mouse choice and probably has a bit of engineering behind it as far as choice of materials goes.

The Linky (http://www.dumbassbiker.com/store/BAKER%20300%20KIT?__utma=1.46887984002422590.12413 25387.1241325387.1241325387.1&__utmb= ganic)%7cutmcmd=organic%7cutmctr=motorcycle%2520ax les%25204140&__utmv=-&__utmk=220554520)

05-03-2009, 06:12 AM
Jap OEM hollow spindles are ususally made from some kind of mature cheddar, judging by how easy it is to round-off the corners of the hex part.

John Stevenson
05-03-2009, 06:58 AM
I'm waiting for the post that says no don't make one, it will break and every slimeball will sue you.
14 posts and it hasn't appeared yet ?

05-03-2009, 07:15 AM
it will break and every slimeball will sue you.

Thats where the "mixed emotion" part comes in. I've wondered that too John,and my thinking right now is that the risk isnt worth what little the job would pay...I think the best plan would be for me to pass along what I've learned about the alloy and refer him to another shop. Maybe one with a $hitload of liability insurance that wont care if it breaks 5 years from now.

05-03-2009, 08:26 AM
For one of my racebiked from A2 toolsteel and my buddy heat treated it and annealed it back. I used to have a lot of bearing failures in my rear wheel hubs and traced it to axles bending (perhaps from flying over jumps at over 240 kph? Not really sure but it had some motor in it also and the jap steels seemed crappy. But this new axle worked perfect never bent and suddenly never had a bearing problem again. Oh if you make it from A2 and it snaps dont bother suing me i got no money left

05-04-2009, 04:35 PM
Once saw a 300 lb. guy with a 10 pound sledge break a 3" steel axle like it was a noodle. My point: the axle was pre nicked on its diameter by lmachinig with a sharp v tool, so when you machine your axle it will be very important to have it very smooth, no nicks, maybe grind it or sunthin. Be safe my friend.


05-04-2009, 06:09 PM
If the bearings are really close to the fork leg, you could get away with aluminum, (I dont recomend it though) the further towards the center of the axel the more force you will have trying to bend it. Then you need a good strong axel. I would use a 41 series with a hole drilled in it.

05-04-2009, 09:52 PM
I love when those OCC guys (is that show still on, I really don't know/care) cut some 4" long axle spacers for a narrow wheel on a wide front end, and best of all, use an air grinder. You would think natural selection would kick in sooner or later?!?

05-06-2009, 07:46 PM
I prefer 4340 as it is more fatigue resistant than 4140 . Peter

05-07-2009, 12:55 AM
use a 4140 annealed, you dont want a hard shaft, it will bust and kill you.

nothing wrong with an 1140 stressproof, its tough too and not brittle.

What you need is a tough shaft not a hard shaft. (yer old lady may say otherwise) :D