Bicycle Mechanics - Mixing steel chainring bolts with alu chainrings...

I needed a new set of chainring bolts for my standard Sram Force crankset. Local shop only had chrome plated steel bolts, which was fine with me since standard alu chainring bolts tend to strip easily.

However, I'm concerned about contact corrosion (or galvanic reaction) between the two dissimilar metals. Does anyone have experience using steel bolts with aluminum chainrings?

I think steel bolts with alu rings is basically standard for most cranks so should not be a problem. As always, grease or anti-seize compound on the threads and contact areas is a good idea.

Agreed - it will be fine as long as you use an anti-seize compound (available at any auto parts store).

-Sam

Agreed - it will be fine as long as you use an anti-seize compound (available at any auto parts store).

-Sam

I did put anti-seize on the threads, but that's not what I'm worried about. I'm worried about the interface where the outside of the steel bolts contact the aluminum chainrings.

And btw, the bolts that came with my crank where aluminum.

the bolts usually get some form of protective coating, like chroming, that keep it from rusting.
actually, the part that will rust first in a chainring bolt, is the spot where the tool comes in contact with the bolt.

the bolts usually get some form of protective coating, like chroming, that keep it from rusting.
actually, the part that will rust first in a chainring bolt, is the spot where the tool comes in contact with the bolt.

+1

Galvanic corrosion also requires the two dissimilar metals to be immersed in an electrolyte, like saltwater. For typical cycling environments. I wouldn't worry about it.

Every crank I've ever worked on, including models from Shimano, SR, Sun Tour, Suguino and Campy, have steel bolts and aluminum chainrings. They have never caused any problems even though some of the cranks were in service for 30,000 miles and used in all types of weather.

Do use grease or anti-seize on the bolt threads but don't worry about corrosion between the chainrings and bolts. It's not a problem

Every crank I've ever worked on, including models from Shimano, SR, Sun Tour, Suguino and Campy, have steel bolts and aluminum chainrings. They have never caused any problems even though some of the cranks were in service for 30,000 miles and used in all types of weather.

Do use grease or anti-seize on the bolt threads but don't worry about corrosion between the chainrings and bolts. It's not a problem

Ditto. It worked for Eddy Merckx- are you better than Eddy? I think not. 8-)

I've had more issues with aluminum chainring bolts not holding torque or stripping out. Steel bolts work fine. I grease the threads on mine.

You should do some maintainence occasionally , take stuff apart to thoroughly clean it.. at least ..

+100 Steel bolts and alloy chain rings are pretty much the standard.

On steel bikes, you will have several places where aluminum and steel meet, like the stem and seat post. That's where the corrosion can be a real problem.

I'm still not convinced. I have seen plenty of rust on drive train components. Even with lubrication and maintenance, that area still collects more than its share of road grime, salty sweat, etc.

There is about 0.30 V of potential between aluminum alloy (anode) and chrome plate steel (cathode). It is not recommended to combine dissimilar metals with greater than 0.25 V difference in "uncontrolled" environments. However, in indoor climate controlled environments, you can get away with as much as 0.50 V. The chainring is probably somewhere between uncontrolled and indoor conditions so perhaps by that criteria 0.30 would be ok. But to me, it's inevitable that the galvanic reaction will occur over time. The questions is how much time.

I'm still not convinced........But to me, it's inevitable that the galvanic reaction will occur over time. The questions is how much time.
OK, do what you want. Several of us with years of experience have said that we have never had the slightest bit of problems with steel bolts in long term use with aluminum chainrings. Maybe the problem is inevitable but it will not happen in any time frame that will cause you problems.

As I said, I have cranksets with over 30,000 miles that have shown no corrosive reaction between the chainrings and bolts even with exposure to rain, snow and salted roads. If that isn't long enough......

I'm still not convinced. I have seen plenty of rust on drive train components. Even with lubrication and maintenance, that area still collects more than its share of road grime, salty sweat, etc.

So buy some steel chainrings. Or stop worrying, and just ride the bike. You'll wear the chainrings out before they corrode. I've seen lots of bikes with all sorts of galvanic corrosion. (Seat post to seat tube, and stem to steerer usually) Never one with chainrings corroded.

Maybe I put too much emphasis on the bolts. Since aluminum is the anode, it will do the corroding. So you shouldn't have experienced any problems with the bolts. Ever examine the aluminum around the bolt holes to check for corrosion, wear, pitting, loss, excessive play, etc.?

Maybe I put too much emphasis on the bolts. Since aluminum is the anode, it will do the corroding. So you shouldn't have experienced any problems with the bolts. Ever examine the aluminum around the bolt holes to check for corrosion, wear, pitting, loss, excessive play, etc.?You should probably just get some aluminum bolts and store it in a vat of dielectric fluid to prevent this possibility.

Or you could get the hint that it is NOT a problem and go enjoy your bike.

Actually, there has been no HINT given. Everyone has responsed to my question of time by citing how many miles they got out of their steel bolts. Mileage has nothing to do with it. I could build a bike and leave it sit i my garage and never ride it one time and it will be just as susceptible to galvanic reaction (minus the salty sweat drops).

Mileage is irrelevent. If you put 30,000 miles on your bike in 2 years, yeah I would expect the chainrings to wear out before galavanic corrosion set in.

If you put 1000 miles a year on your bike and want it to be in good condition 20 years from now, totally different situation.

Actually, there has been no HINT given. Everyone has responsed to my question of time by citing how many miles they got out of their steel bolts. Mileage has nothing to do with it. I could build a bike and leave it sit i my garage and never ride it one time and it will be just as susceptible to galvanic reaction (minus the salty sweat drops).

Mileage is irrelevent. If you put 30,000 miles on your bike in 2 years, yeah I would expect the chainrings to wear out before galavanic corrosion set in.

If you put 1000 miles a year on your bike and want to be in good condition 20 years from now, totally different situation.What, did you just finish an Intro To Chemistry class or something? In the real world, this is NOT a problem. Chalk it up to anodized parts, chalk it up to fewer salt drops than you think, but your supposed problem simply does not exist.

God knows what will happen when you find out about all the other places steel bolts are used on aluminum throughout your bicycle.

Galvanic corrosion also requires the two dissimilar metals to be immersed in an electrolyte, like saltwater. For typical cycling environments. I wouldn't worry about it.

+100

But if you are really that worried about it then hang a 10# magnisium anode from your cranks or use an impress current cathodic protection system, just insulate all points of contact with your bike (especially if you have a Brooks saddle with copper rivits)

But on a serious note, you really need an electrolytic solution to have the problem.

My understanding is that electrolysis in these situations is more of an issue if one uses stainless steel bolts with aluminum. The Nickel content in the stainless is more electically reactive. Any Metallurgical or Electrical engineers, on the forum, care to weigh in?

Galvanic corrosion is an issue more with seatposts and quill stems getting stuck,
if left in a long time..

Sweated upon profusely on the trainer, indoors.

In the shipyard we welded Zinc ingots inside the tanks that were a sacrificial metal
so salt ate away that rather than the hull.

My understanding is that electrolysis in these situations is more of an issue if one uses stainless steel bolts with aluminum. The Nickel content in the stainless is more electically reactive. Any Metallurgical or Electrical engineers, on the forum, care to weigh in?

Yeah, that's true. Wikipedia of all places actually does a pretty good job with galvanic reaction (so all the nay-sayers can see that I'm not making this up)

http://en.wikipedia.org/wiki/Galvanic_corrosion

My understanding is that electrolysis in these situations is more of an issue if one uses stainless steel bolts with aluminum. The Nickel content in the stainless is more electically reactive. Any Metallurgical or Electrical engineers, on the forum, care to weigh in?B.S., Materials Engineering. Theoretically, anything dissimilar will eventually corrode. In practice, the anodizing, lack of electrolytic solution, and grease used pretty much eliminate this as a problem within the usable lifespan of the product.

Yeah, that's true. Wikipedia of all places actually does a pretty good job with galvanic reaction (so all the nay-sayers can see that I'm not making this up)

http://en.wikipedia.org/wiki/Galvanic_corrosion
No one said you were making it up. What we said was it is NOT a problem in bicycle use. Yes, I have examined aluminum chainrings after YEARS of use with steel bolts. Repeat: It is NOT a problem.

No one said you were making it up. What we said was it is NOT a problem in bicycle use. Yes, I have examined aluminum chainrings after YEARS of use with steel bolts. Repeat: It is NOT a problem.

Then stay tuned for my next thread: "What happens when valve stem isotope atoms swap neutrons?"

Then stay tuned for my next thread: "What happens when valve stem isotope atoms swap neutrons?"
Hey, if you want to fixate on a potential (pun intended) problem, consider the fact that you have stainless steel spokes in contact with both your aluminum hub flanges and your aluminum rims. Your wheels are going to collapse catastrophically any day now. :D

I have encountered corroision problems with steel bolts on aluminum chainrings before when I dismatled bikes that were ridden a lot in the rain. It was a pain in the butt to get those bolts to come off as the corroded two pieces of the bolts did not want to turn to screw off from each other. If you do ride a lot in the wet, it might be good to consider going with all aluminum. Not that aluminum will not corrode too after some time in the wet, but it will not corrode as fast as a dissiimlar metal situation with steel bolts and sluminum chainrings put together. As for the stregnth of aluminum bolts, I have used aluminum bolts on all my chainrings since the 80's Never had any problems with them at all. All that steel gets you is the shiney chrome finsh, as far as I'm concerned.

Chombi

I have encountered corroision problems with steel bolts on aluminum chainrings before when I dismatled bikes that were ridden a lot in the rain. It was a pain in the butt to get those bolts to come off as the corroded two pieces of the bolts did not want to turn to screw off from each other. If you do ride a lot in the wet, it might be good to consider going with all aluminum. Not that aluminum will not corrode too after some time in the wet, but it will not corrode as fast as a dissiimlar metal situation with steel bolts and sluminum chainrings put together. As for the stregnth of aluminum bolts, I have used aluminum bolts on all my chainrings since the 80's Never had any problems with them at all. All that steel gets you is the shiney chrome finsh, as far as I'm concerned.

Chombi

yeah, I've gotten that too. The bolt and the nut stick together quite well after a winter with lots of brine on the road.
but those were bolts that had zero grease from the factory.


Hey, if you want to fixate on a potential (pun intended) problem, consider the fact that you have stainless steel spokes in contact with both your aluminum hub flanges and your aluminum rims. Your wheels are going to collapse catastrophically any day now. :D

some of the cheaper built wheels do get problems with the brass nipples sticking. but that's on wheels that have been sitting out in the rain for a long time... like over a decade.

Cars use special Dacro-coated bolts to join aluminum body/chassis parts together - but it's a common place thing to see ferrous fasteners with Al components in almost any industry. However, those are either coated bolts or stainless steel if they are an OEM application. I say if you use GOOD anti-seize like Loctite C5-A or even blue Loctite, you can cut down the risk of galvanic corrosion. However, Al bolts are the best way to go.

Cars use special Dacro-coated bolts to join aluminum body/chassis parts together - but it's a common place thing to see ferrous fasteners with Al components in almost any industry. However, those are either coated bolts or stainless steel if they are an OEM application. I say if you use GOOD anti-seize like Loctite C5-A or even blue Loctite, you can cut down the risk of galvanic corrosion. However, Al bolts are the best way to go.

except for crank bolts, they're not a good choice, since they need loctite to keep from loosening and easily crack.
I would say the problem is caused by the bolt being designed with steel in mind in the first place and trying to replace the bolts with aluminum, which is simply not strong enough.

I would recommend marine grade grease. Much easier to get the bolts off when it's time to change the rings out.

Lots of people are using Loctite and anti-sieze interchangeably, but the two are entirely different. One bonds the threads together and the other prevents bond. I used anti-sieze on the threads of the chainring bolts so that hopefully when the day comes to remove them, they will break free easily and not be rusted together, which by the way is not galvanic reaction since the male and female threaded parts are of the same material.

The galvanic reaction would take place on the outside of the bolts where it contacts the aluminum. I applied marine grease to the outsides of the bolts to hopefully help break the conductive path between the steel and Al, as well as reduce noise that I was getting which started the whole problem in the first place.

However, Al bolts are the best way to go.
I disagree. Aluminum crank bolts are far weaker than steel and if you think aluminum on aluminum will prevent corrosion, talk to anyone who has had an aluminum searpost stuck in an aluminum frame.

Grease them and be done with it.

I disagree. Aluminum crank bolts are far weaker than steel and if you think aluminum on aluminum will prevent corrosion, talk to anyone who has had an aluminum searpost stuck in an aluminum frame.

Grease them and be done with it.

Al v Steel strength is irrelevant here. Without running the numbers, I garauntee the cross sectional area of 5 aluminum bolts is plenty strong enough to transmit the forces required of them. Doesn't matter how much stronger steel is, in this case Al is plenty strong enough

Half way between Fe and Al is Ti .. get some Titanium Chainring Bolts then.

Al v Steel strength is irrelevant here. Without running the numbers, I garauntee the cross sectional area of 5 aluminum bolts is plenty strong enough to transmit the forces required of them. Doesn't matter how much stronger steel is, in this case Al is plenty strong enough
It's not the shear load that's the problem, it's the needed clamping force to keep the rings tight enough to avoid squeaking.

Frankly, if you are so convinced aluminum chainring bolts are better, buy them and report back after a few years.

It's not the shear load that's the problem, it's the needed clamping force to keep the rings tight enough to avoid squeaking.

Frankly, if you are so convinced aluminum chainring bolts are better, buy them and report back after a few years.

So by your previous poo-pooing of aluminum bolts, are you implying that the bolts are not strong enough to provide the required clamping force? I double my garauntee that the aluminum bolts are not going to fail in tension by being tightened to the proper torque required to achieve sufficient clamping force. And just for the record, tightening a bolt until it breaks is a form of shear failure, not so much tension.

So by your previous poo-pooing of aluminum bolts, are you implying that the bolts are not strong enough to provide the required clamping force? I double my garauntee that the aluminum bolts are not going to fail in tension by being tightened to the proper torque required to achieve sufficient clamping force. And just for the record, tightening a bolt until it breaks is a form of shear failure, not so much tension.

I guarantee you that a vast majority of the aluminum chainring bolts sold on the market are no good.

So by your previous poo-pooing of aluminum bolts, are you implying that the bolts are not strong enough to provide the required clamping force? I double my garauntee that the aluminum bolts are not going to fail in tension by being tightened to the proper torque required to achieve sufficient clamping force. And just for the record, tightening a bolt until it breaks is a form of shear failure, not so much tension.
I'm poo-pooing aluminum chainring bolts as an unnecessary refinement to cure the non-existent "problem" you began this entire unnecessarily long thread with. i.e. corrosive incompatibility between aluminum chainrings and steel bolts. It doesn't matter if they are as strong as Hercules, they aren't needed. If you are so enthralled with them buy them. No one is stopping you. We are just saying they aren't of value to your original question.

Every so often someone will start a thread by proposing a "problem" they think desperately needs to be solved. Even after many experienced riders and mechanics report the problem isn't a problem, they persist in insisting it must be and then coming up with a bunch of rationals to defend their original claim or go off on a tangent that changes the original claim entirely. This thread is one of those.

Sorry to make the thread one post longer but let me add testimony: Thirty plus years of riding a large variety of aluminum rings with various steel (mostly) and aluminum fixing bolts. Have never noted corrosion.

I guarantee you that a vast majority of the aluminum chainring bolts sold on the market are no good.

That is probably true, but it has nothing to do with the inherent strength of Al.

That is probably true, but it has nothing to do with the inherent strength of Al.

the piece was designed to use steel bolts to begin with, and aluminum parts should have more material than steel bolts and nuts, especially hollow ones, if it is to replace steel.

everything is designed with their original purpose, and when you start replacing parts with weaker materials, then they start to break. That's why aluminum bike frames are designed with oversized tubing.

aluminum is very soft compared to steel. Fasteners, unless designed from the ground up to use aluminum, should not be replaced with aluminum. When you start cutting corners, you start to eat into the built in safety zone, and that's what aluminum chainring bolts are.

That is probably true, but it has nothing to do with the inherent strength of Al.

As was pointed out above, replacing a steel fastener with an aluminum one of identical design is problematic. The bolt & nut in a chainring fastener has a lot of small sections and sharp angles that form stress risers- just the thing to avoid in aluminum. I have a couple sets in my collection- but I won't use them on a bike I need to depend on. I've had the heads break off or the threads strip under ordinary hand pressure. (I'll also point out that you noted that aluminum bolts tend to strip easily.)

If you wanted to redesign the crank/chainring interface to take advantage of the properties of aluminum, go right ahead. I'll stick with steel bolts, which have been perfectly reliable in my 30 years of wrenching on bikes.

Does anyone have experience using steel bolts with aluminum chainrings?

PMSL. Do we what!


aluminum is very soft compared to steel.

Not all aluminium is created equal... I'd be prepared to try some quality ally chainring bolts, but then I'm only 65kg.

dp

A couple decades ago, budding young engineer at Honda figured he found the secret to the 500cc Grand Prix championships. He went through the design specs of the engine and scratched out all instances of steel and replaced with titanium. Then he found all occurrences of aluminium and replaced it with magnesium. Wow, what brilliance, he instantly shaved of 25kg an already super-light 150kg motorcycle!

Now on the demo day of his new design, he was as proud of his creation as a new father. It wasn't mnore than 5-minutes into the test-session when the magnesium pistons expanded too much and seized themselves into the cylinders. Which cracked the titanium crank and sent shards out the side of the case, narrowly missed taking out the rider's ankle by mere centimeters. Needless to say the young engineer learned an important lesson.

Wow, no one knows what they're talking about. The aluminum chainring bolts were ORIGINAL equipment on the Sram crank. They only replacement is swapping them out for steel. The thing came from the factory with aluminum bolts, yet I am being lectured about replacing steel with aluminum. Ah, the age of the internet experts...

I needed a new set of chainring bolts for my standard Sram Force crankset.

Why did you need to replace your Al bolts with a new set of bolts?

Wow, no one knows what they're talking about. The aluminum chainring bolts were ORIGINAL equipment on the Sram crank. They only replacement is swapping them out for steel. The thing came from the factory with aluminum bolts, yet I am being lectured about replacing steel with aluminum. Ah, the age of the internet experts...
+1......... I thought of posting the same the other day on this thread but I didn't want to bother as it seems like some here are just making declarations about how bad Al bolts are without anything to back up their claims, not even personal experience of Al bolts breaking on them. All my bikes came with Al bolts on their cranksets since the 80's same with cranks I bought through the years to mod up my bikes and I also bought a couple of NOS cranks this year with Al bolts on them and I never had any problems with them stregnth-wise. No, you don't need to change out your bolts if they are Al! If installed correctly, they are just as safe as steel bolts. Otherwise we would have heard about this in a big way years ago.

Chombi

Why did you need to replace your Al bolts with a new set of bolts?

I had over tightened a couple of them and they were boogered up. My fault for not using a torque wrench.

The thing came from the factory with aluminum bolts, yet I am being lectured about replacing steel with aluminum. Ah, the age of the internet experts...
No, you were being lectured on your fixation on the possible corrosion problems that would arise from the use of steel bolts in aluminum chainrings. You were told it isn't a problem. Everything after that was way off topic.