# aluminum or ti bolts?



## PoorCyclist (Oct 14, 2010)

Is aluminum bolt lighter than Ti bolt?

I need to replace my top cap bolt because the head shape is wrong for the top cap. So for the application, it just need a tiny bit of torque to set the preload.. and AL bolt is alot cheaper


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## laffeaux (Dec 12, 2001)

Aluminum is lighter. For a top cap aluminum should work fine.

In general, don't use aluminum bolts any time where having the bolt snap would be detrimental to you and/or your bike. Aluminum bolts are not particularly strong and are brittle. They work for water bottle cages and chain ring bolts (although they're pretty easy to break if you over tighten them). A top cap bolt doesn't need to be on the bike once the stem is tightened, so an aluminum bolt would be fine.


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## PoorCyclist (Oct 14, 2010)

So.. my bike came with the Aluminum bolt for the water bottle cage, at first I thought well, this is a big bolt because it takes a 5mm hex instead 3-4mm. But I weighted it and it is about 1/3 of the weight. I have been using it to hold my cages.


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## aengbretson (Sep 17, 2009)

Go with aluminum. The weight savings will be literally next-to-nothing.


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## Kerry Irons (Feb 25, 2002)

*Weight savings?*



aengbretson said:


> Go with aluminum. The weight savings will be literally next-to-nothing.


Not sure what you mean here. Al is less dense than Ti (2.75 vs. 4.47 s.g.).


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## FBinNY (Jan 24, 2009)

Go with the aluminum bolt. If your're concerned about strength when setting the headset preload, borrow a page for the days when folks used aluminum bolts for square taper cranks.

Use a steel bolt, and even another top cap to adjust the headset, tighten the stem, and switch to aluminum.


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## FBinNY (Jan 24, 2009)

Go with the aluminum bolt. If you're concerned about strength when setting the headset preload, borrow a page for the days when folks used aluminum bolts for square taper cranks.

Use a steel bolt, and even another top cap to adjust the headset, tighten the stem, and switch to aluminum.


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## flatsix911 (Jun 28, 2009)

As a professional engineer I would recommend:


Use Al bolts only on non critical loads ... bottle cages, top cap etc.
Use Ti bolts on all critical load areas ... stem, saddle, crank, etc.


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## cxwrench (Nov 9, 2004)

alloy bolt is absolutely fine for the stem top cap/preload bolt. it does nothing but adjust the bearing preload on the headset and then sit there holding the top cap.


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## MR_GRUMPY (Aug 21, 2002)

Weight savings? How much do you weigh? Can you lose 1/4" pound before your next ride??
Do you ride with one or two bottles? One or two cages???


inquiring minds.......
.
.
.


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## Kontact (Apr 1, 2011)

MR_GRUMPY said:


> Weight savings? How much do you weigh? Can you lose 1/4" pound before your next ride??
> Do you ride with one or two bottles? One or two cages???
> 
> 
> ...


Which is stupider: Spending $1000 on a slightly lighter groupo, or 10 cents on an aluminum bolt?

I have a hard time seeing why this decision should cause any sort of emotional reaction at all.


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## Guest (Jan 17, 2012)

Kontact said:


> Which is stupider: Spending $1000 on a slightly lighter groupo, or 10 cents on an aluminum bolt?
> 
> I have a hard time seeing why this decision should cause any sort of emotional reaction at all.


Agreed... if you look at a lot of this stuff on a $/gram basis, things like carbon fiber cages, aluminum bolts, even things like cutting down unnecessarily long bolts (only need to be long enough to engage all the available threads) etc. are low-hanging fruit in the shaving weight game. They're still expensive for the difference in weight, but going from second-tier to top-tier groupset (ie Shimano Dura-Ace vs Ultegra, or SRAM Red vs Force, etc) is a more costly deal for most components, and for the most part those difference are primarily for weight -- thing like titanium machine screws or cassette cogs instead of steel....


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## GRAVELBIKE (Sep 16, 2011)

laffeaux said:


> Aluminum is lighter. For a top cap aluminum should work fine.
> 
> In general, don't use aluminum bolts any time where having the bolt snap would be detrimental to you and/or your bike. Aluminum bolts are not particularly strong and are brittle. They work for water bottle cages and chain ring bolts (although they're pretty easy to break if you over tighten them). A top cap bolt doesn't need to be on the bike once the stem is tightened, so an aluminum bolt would be fine.


What s/he said.


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## terbennett (Apr 1, 2006)

Kontact said:


> Which is stupider: Spending $1000 on a slightly lighter groupo, or 10 cents on an aluminum bolt?
> 
> I have a hard time seeing why this decision should cause any sort of emotional reaction at all.


+2.....:thumbsup:


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## outhere (Apr 11, 2011)

The rule of thumb I remember from years ago is that Ti (bolts, etc.) weigh 40% as much as the equivalent steel part and that aluminum weighs 33.33% (i.e. 1/3) as much as the equivalent steel part.


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## Kerry Irons (Feb 25, 2002)

*Broken thumb*



outhere said:


> The rule of thumb I remember from years ago is that Ti (bolts, etc.) weigh 40% as much as the equivalent steel part and that aluminum weighs 33.33% (i.e. 1/3) as much as the equivalent steel part.


You remember wrong. You could have just read my post or looked it up. Aluminum is 34% as dense as steel. Ti is 58% as dense as steel. Steel specific gravity = 7.8, Ti = 4.5, Al = 2.55-2.8.


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## outhere (Apr 11, 2011)

Actually, I remember correctly I just got titanium backwards. That is, 60%, not 40%. Otherwise, my figure for aluminum is correct. Mind you, a rule of thumb is not intended to be perfectly exact but is intended to give one a method of quickly calculating the weight reduction vis a vis steel acheived by using either titanium or aluminum.

So, a hypothtical 10g steel bolt would weigh about 6g if rendered in titanium and about 3.3g if rendered in aluminum.


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## bikes4fun (Mar 2, 2010)

If aluminum is used, recommend also using anti-seize compound to prevent dissimilar metal corrosion.


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## GirchyGirchy (Feb 12, 2004)

IMO the main purpose of a top cap is to set preload of the bearings prior to tightening the stem. After that it doesn't serve as anything else other than aesthetics. If you're really that worried about the weight, remove the cap and the bolt.


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## Kontact (Apr 1, 2011)

bikes4fun said:


> If aluminum is used, recommend also using anti-seize compound to prevent dissimilar metal corrosion.


Grease works perfectly fine for aluminum screws and bolts.


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## Ppopp (Jun 20, 2011)

GirchyGirchy said:


> IMO the main purpose of a top cap is to set preload of the bearings prior to tightening the stem. After that it doesn't serve as anything else other than aesthetics. If you're really that worried about the weight, remove the cap and the bolt.


I just had a Rob Schneider SNL flashback:

"Cool bike. Carbon fiber frame, aero wheels. It probably weighs less than 15 pounds."

"Yeah, and it has the cool hole in the top of the steerer where you can put your weed in it."


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