Bronze vs Billet Steel Shift Forks

[turboprop]

Would rather keep this focused specifically on the different materials and not get hung up on model years, etc.

What are the pros and cons to bronze or billet steel shift forks?

[kd]

I have no experience testing between the two but from a metallurgy point of view I would expect the steel ones to be less prone to bending and holding that shape than brass if abused.  More resilience or spring back so to speak.  I would also think the collets that fasten them are less likely to wear under the fastener and become loose.

[rbabos]

Find it hard to believe it's a full bronze fork. Too soft and would bend easy.  V rod for example is steel but bronze plated to act as a bearing face.
Ron

[kd]

That make more sense.

[turboprop]

Find it hard to believe it's a full bronze fork. Too soft and would bend easy.  V rod for example is steel but bronze plated to act as a bearing face.
Ron

Baker used to offer solid bronze forks for the BT five speed. They have since shifted their offering to only billet steel forks, but the bronze stuff is still around. I think there are a couple of sets on eBay right now. I have a set in one of my FXRs and they appear to be either solid bronze or the plating is really thick.  Time to replace them and I am at a decision point, either another set of bronze forks (I have a couple sets) or a set of their newer billet steel forks. Not a lot of information online that discusses the pros and cons of steel vs billet.

[JW113]

Steel is stronger than bronze, but how strong does a shift fork have to be?

Bronze has much better friction properties than steel against a spinning steel shift dog, so it will wear less. but how long does as shift fork have to last?

Bronze is more expensive than steel.

Bronze and steel have similar specific gravity (~8), so weight is not a factor.

"Billet" is a marketing term these days. More or less 'everything' metallic that is not as-cast starts out life as formed billet until processed into something else. I guess it is meant to imply that it's stronger or better than non-billet? In fact, strength or wear or toughness properties come from what happens after a metal is billet, for example forging or heat treating.

I can't imagine anything wrong or right with bronze shift forks. The material is plenty strong and will outlast steel in this application.

Flip a coin, I don't see there is a huge benefit of one over the other as a shift fork.

-JW

[PoorUB]

I'm  certain  Harley is concerned  about the weight of shift forks, then builds rims that weigh twice as much as anything else  out there.

[turboprop]

I'm  certain  Harley is concerned  about the weight of shift forks, then builds rims that weigh twice as much as anything else  out there.

You are right. Those pesky overweight shift forks. If only.....

Seriously, and I hate straying too far off subject, lets think about the weight of these forks. I will swag their lateral movement on the shaft at maybe half an inch and their weight as maybe .20 Lbs? Not really enough mass to create any significant inertia, or maybe there is?

From my perspective as an executive at a company that manufactures, I would think that total cost (manufacturing and warranty) would drive the decision, but that is not what I am asking about. I really dont care about the costs, just the technical and performance differences.

So, to take cost out of the discussion and look simply at the material that would make the best performing shift fork, bronze vs steel, I dont know.

FWIW, all of my FXRs are currently equipped with bronze forks but in the interest of science I am going to put in a set Baker steels just to see if there are any noticeable differences. Will see.

Thank you to everyone that provided technical information. I wish there were more of you on this page. 

[kd]

You got me interested so I asked my buddy Google.  I entered your thread title as a query and after a quick scan, by the second page, this popped up.

HGT Shift forks are CNC'd from Billet steel for zero flex which provided a more positive shift than cast or bronze shift forks.

I am short on time to search through their info or look for more right now but the info seems to be out there.  I know .... It's off the internet, but this is another performance gear box manufacturer (like Baker) that claims to have gone to steel (from brass).  In this case they say why.  Maybe Baker will be forthcoming or maybe Mark will see this and be able to shed some light on it for us, or maybe Bert just likes to be safe when he sells his transmissions to hooligans.   

Here's a link to HGT Precision

https://www.hgtprecision.com/

[Deye76]

The hot rod (car guys) use steel forks with bronze pads in T-56 tranny's. Don't think anything like that is available for our tranny's.

[turboprop]

The hot rod (car guys) use steel forks with bronze pads in T-56 tranny's. Don't if anything like that is available for our tranny's.

Baker used to make some solid bronze bushings. I have not seen harley shift forks made with any type of pads. The groves in the harley gears are only about .200" wide (guestimation). Making them with a pad would require either redesigned gears with wider grooves or forks with really thin base metal. Both of which dont seem likely or practical.

[Ohio HD]

2nd hand information here, I used to rebuild a lot of iron head Sportster transmissions. Since the shift forks aren't shimmed, rather are machined in different +/- offsets to setup gear spacing, I used to keep several on hand. John Boone a life long HD mechanic at HD of Hamilton (era 1965ish to 1999ish) told me the bronze forks were supposed to heat up and gall less due to their inherent lubricity. He said to use the steel ones, they were stronger. I personally couldn't tell any difference in how a Sportster shifted or how they held up.   

[rageglide]

Dissimilar materials work better together as well.  Most automotive manuals (at least in the days of iron castings) had steel forks with bronze bushings and in many cases bronze pads.   Not sure what billet steel means, so i guess that makes this response worth nothin'.   I would think forged would be stronger, especially in this day and age of non-virgin materials.

[turboprop]

Dissimilar materials work better together as well.  Most automotive manuals (at least in the days of iron castings) had steel forks with bronze bushings and in many cases bronze pads.   Not sure what billet steel means, so i guess that makes this response worth nothin'.   I would think forged would be stronger, especially in this day and age of non-virgin materials.

Not sure myself. But Bert 'Effing' Baker is a pretty smart guy and thats how he markets his shifter forks. Billet steel. Ask Bert.

[turboprop]

2nd hand information here, I used to rebuild a lot of iron head Sportster transmissions. Since the shift forks aren't shimmed, rather are machined in different +/- offsets to setup gear spacing, I used to keep several on hand. John Boone a life long HD mechanic at HD of Hamilton (era 1965ish to 1999ish) told me the bronze forks were supposed to heat up and gall less due to their inherent lubricity. He said to use the steel ones, they were stronger. I personally couldn't tell any difference in how a Sportster shifted or how they held up.

I remember those days. Rebuilt a few myself. Back in the day the joke was iron heads were the gifts that kept on giving. A lot of shops made money working on those bikes over and over.

[Ohio HD]

2nd hand information here, I used to rebuild a lot of iron head Sportster transmissions. Since the shift forks aren't shimmed, rather are machined in different +/- offsets to setup gear spacing, I used to keep several on hand. John Boone a life long HD mechanic at HD of Hamilton (era 1965ish to 1999ish) told me the bronze forks were supposed to heat up and gall less due to their inherent lubricity. He said to use the steel ones, they were stronger. I personally couldn't tell any difference in how a Sportster shifted or how they held up.

I remember those days. Rebuilt a few myself. Back in the day the joke was iron heads were the gifts that kept on giving. A lot of shops made money working on those bikes over and over.

I got good and fast at them. I'd have a bike dropped off in the AM. Call them about 4:00pm to come and get it. I kept all the common wear gears, usually 2nd gear and the forks took care of most of them. Also kept the gaskets and output shaft seals and bearings on hand.

[rageglide]

Not sure myself. But Bert 'Effing' Baker is a pretty smart guy and thats how he markets his shifter forks. Billet steel. Ask Bert.

No 'Effing' doubt.  But we've all been around long enough to know the word billet elicits all sorts of magic.  Most expensive way to make a product, so must be best.  Materials guys (and bean counters) will say, cast and machine.  Maybe billet cranks in a top fuel bike/car is stronger than a forged part, but damn you gotta get GOOD steel.   On a shift fork, does it matter?   Hell if I know, more weight in the gears we have to move around than the forks.  The shift dogs (or clutch drag) probably cause us more grief imo.

[kd]

Here's a decent description for billet steel and when / why it's used.

https://www.google.ca/amp/s/blog.mrt-castings.co.uk/blog/the-difference-between-cast-forged-and-billet%3fhs_amp=true

[rbabos]

V rod uses a combo. Looks like a hot spray bronze coating to the steel fork.
Ron

[jmorton10]

I remember those days. Rebuilt a few myself. Back in the day the joke was iron heads were the gifts that kept on giving. A lot of shops made money working on those bikes over and over.

I did quite a few also, that is the ones that didn't make a hole through the cases when they blew up LOL....

~John