terrymorse 

Expensive Component:

WCS CARBON 1-BOLT ZERO OFFSET SEATPOST - $259.95

Steel mounting bolt after a few years, rusted:




Single bolt replacement cost (boltdepot.com):

• zinc-plated steel: $0.42
• stainless steel: $0.62

Same issue with Ritchey stem mounting bolts. They become rusty after 1 or 2 seasons.

Why, Ritchey? Why?

Rolla

Do the zinc and/or stainless replacement bolts last longer?

wolfchild

My Thompson seat post and stem are 15 years old and still don't have any rust on the bolts despite being used during winter time and wet conditions. All the other bolts on all my other bikes and components have some rust on them. The disc brake adapter and caliper bolts have most rust on them even after after I've been greasing them during winter riding season. Axle nuts have no rust because they are zinc plated and i grease them regularly...It's just cosmetic rust and doesn't bother me.

terrymorse 

The zinc-plated bits rust rather quickly. The stainless ones don’t rust, unless they are in a very corrosive environment (like salt water spray) for a long time.

That Ritchey bolt was probably zinc-plated.

Mojo31

https://provenproductivity.com/galva...r-materials-2/

KerryIrons

My Thompson seat post with nearly 80K miles on it shows zero rust on the bolts. My Thompson stem with the same mileage (and arguable more salt exposure from my hands occasionally clamping the bars right next to the stem) has rust on all the bolts. I've sought out stainless bolts but haven't tried very hard. The ones I can get from my local hardware store have heads that are just a bit to big. I agree that ALL bike components should be specified with stainless bolts where possible. There are various grades of stainless steel that are more or less corrosion resistant.

Bald Paul

If you're using a carbon seatpost to save some weight, why not go with titanium bolts? No rust, and lighter than stainless steel. Yes, they cost more, but if you're going with a $260 seatpost, well.....

Titanium Fasteners - Firmakes Titanium

elcruxio

I don't think any of my seat post bolts have ever rusted... but even if they did, I probably wouldn't swap to stanless or titanium. A seatpost bolt has to hold a lot of weight so that's one place I'd prefer 10.9 or higher grade steel.

njkayaker

fify.

rydabent

It would seem to me that the really expensive components would have stainless steel bolts in the first place.

Polaris OBark

The problem is that titanium, or even stainless steel bolts, of the same size, are weaker.

The carbon/steel interface allows for an oxidation-reduction reaction to take place, due to their electrochemical potential difference.

greatbasin

That's a zinc-plated bolt. Is it adjacent or contacting the carbon? Or does it bolt to an aluminum casting? With the presence of an electrolyte, a carbon/zinc assembly will produce an electrochemical reaction resulting in the erosion of the zinc anode (the bolt).

I would look for a Titanium bolt for this application. Titanium bolts are not weak, but they have two problems: galling, and flex. The lack of lateral stiffness isn't an issue in this application. To address galling, be generous with anti-seize when installing it.

Another good one is aluminum alloys with scandium. I've used a lot of aluminum bolts for less critical applicaitons like bolting side covers on engines. The quality of the aluminum bolts was abysmal, but it didn't have to be. There are some great aluminum alloys and while they aren't direct replacements for steel where the tensile strength is critical, they are strong and light. Specifying a larger aluminum bolt can be an effective substitute for steel but has design/build implications. Another trick I've seen are hollow steel bolts. Those have incredible strength/weight ratios, but they still require a compatible finish process.

I don't know where a person can get a small quantity of high-quality bolts and fasteners nowadays. Back in the day, I ordered from Aircraft Spruce. They're still around. The Titanium bolt makers I used 25 years ago are all gone, but no doubt there are others now.

LarrySellerz

From looking at their website I think it’s a stainless m5 bolt, can’t find the length called out anywhere https://ritcheylogic.com/bike/seatpo...plete-clampset


https://www.mcmaster.com/product/91292A194 something like this of the correct length and “collar” (the distance between the bottom of the head and the start of the threads.) is what’s on there now, it’s almost certainly standard 304 series.

if you want more corrosion resistance with 316 McMaster offers that too https://www.mcmaster.com/product/92290A258
i naively think that is sensible.. replacing with titanium or aluminum alloy sounds really weird, don’t try to reinvent the wheel.

LarrySellerz

From looking at their website I think it’s a stainless m5 bolt, can’t find the length called out anywhere https://ritcheylogic.com/bike/seatpo...plete-clampset


https://www.mcmaster.com/product/91292A194 something like this of the correct length and “collar” (the distance between the bottom of the head and the start of the threads.) is what’s on there now, it’s almost certainly standard 304 series. That’s assuming it’s actually ss.

if you want more corrosion resistance with 316 McMaster offers that too https://www.mcmaster.com/product/92290A258
i naively think that is sensible.. replacing with titanium or aluminum alloy sounds really weird, don’t try to reinvent the wheel.

terrymorse 

Well, that's an M6 bolt. Pretty hefty. Even in stainless, it should have a tensile strength above 10,000 lbs. If that's not enough to keep it from breaking, then I'd question the seatpost design.

This is what I'm saying.

This seatpost design is all steel touching aluminum. The aluminum castings clamp to the carbon post.

It's a (presumably) zinc-plated steel, bolted to aluminum castings. It doesn't touch any carbon bits.

It's an M6 bolt (non-stainless), actually. 1.0 mm threads, 55 mm long.

I replaced it with this stainless bolt.

zandoval 

What a sham. Components on a $259.95 Seat Post should not rust!

Just another example of not getting what you paid for... Come On Ritchey. It's little things like this that make me sober when pointing out defects in in some cheap ChiCom knockoff that doesn't rust...

Yep... This post deserves a Titanium bolt.

MoAlpha

Agree. I have replaced a lot of hex head bolts on bike parts with equivalent items from my local marine chandler (where I spend far too much time and money for other reasons). They don’t corrode.

HTupolev

I'm skeptical of your math.

The unthreaded portion of an M6 bolt has a cross-sectional area of about .044 square inches. High-strength 316 stainless hardware is usually rated for a minimum ultimate strength of around 110,000PSI, which over .044in^2 gives about 4,800 pounds.
But the threading also eats up a ton of the effective diameter. Realistically I'm not sure anyone should be counting on a coarse-thread M6 bolt to have an effective loaded cross-sectional area of much over .03 square inches, which gives 3,300 pounds.

Furthermore, stainless hardware often yields at far below its ultimate strength, so even "3300 pounds" is probably an optimistic perspective for most applications.

Polaris OBark

Doesn't matter. The aluminum is a wire that connects a cathode and anode. Current flows.

Polaris OBark

I just noticed the bolts in my carbon stem aren't looking too hot.

Pratt

Seems like someone would make an anti-corrosion chamois lube.

Shadco 

Stainless = not strong

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terrymorse 

You’re right, A typical stainless M6 bolt tensile strength is roughly 10,000 Newtons (not pounds), or about 2300 pounds.

(I misread the table)

Still, pretty beefy.

wolfchild

Plenty strong for use on bicycles.

Shadco 

We won’t use stainless in the drive train of an RC helicopter, very dangerous when they let go and they do.



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