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PostPosted: Wed Jan 15, 2014 12:02 am 
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Location: Northern Ireland
Hello all,

After my Trek Madone being in storage for a while (4 years) the Bontrager XXX stem bolts and washers are rusting.
I have purchased some Titanium bolts and washers from ebay (http://www.ebay.co.uk/itm/261322665455?var=560240873265&ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649)

Problem is I have read a lot on forums about titanium not being as strong as the factory steel bolts, and advice given to use stainless steel.
Like wise I have read that stainless steel is not as strong as the factory bolts.

Can anyone shed any light on this? Are titanium bolts on a stem safe?
PS: I have emailed Bontrager for there answer.

Also the factory steel bolts were fitted using threadlock, is this required or will anti-seize be fine.

Im also an Engineer and have, and know how to use a torque wrench.

Thanks
Alan

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PostPosted: Wed Jan 15, 2014 12:36 am 
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Not a PEng like you but there have been threads on this issue. I'm remembering that Ti screws have about 1/2 the tensile strength of steel for the same diameter.

So, not a great choice for a stem faceplate where it's kind of critical.

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Posted: Wed Jan 15, 2014 12:36 am 


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PostPosted: Wed Jan 15, 2014 1:04 am 
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A lot of companies (Ritchey, Deda, 3T, FSA, Zipp, Extralite, New Ultimate, Tune, Enve) sell stems with titanium bolts. Would they do this if they felt that the bolts wouldn't hold up?

Also, correct me if I'm wrong, but it depends on the grade of the steel. In some cases titanium has a higher ultimate tensile strength than steel.

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PostPosted: Wed Jan 15, 2014 2:03 am 
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Wait.......you are an engineer and you can't look this up in standard mechanical engineering handbooks available just about everywhere? Really?


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PostPosted: Wed Jan 15, 2014 2:28 am 
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I've been using titanium bolts on stems for over twenty years. I've only had one failure and it took a crash hard enough to knock me out and split a helmet in two to do it. It was also a 4 bolt front plate and one bolt broke and the other three held. It was still rideable.

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PostPosted: Wed Jan 15, 2014 4:10 am 
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6AL4V Ti is stronger than MOST steel. There are SOME stainless (and others) that are stronger.

But that isn't the whole picture either. How the threads arer formed (cut or rolled) also influences the "strength" because tbolts often snap at a thread root, which is a stress concentration.

So, the devil is always in the details.
Buy Pro-Bolt 6AL4V certified bolts with rolled threads and you will never have a problem .

Once you start asking the question, then you realize you can never really be sure about bolts unless they are certified. Most bolts work prtty good most of the time. It is the few that break that cause us to ask the question.

(Never say "never", but they are super high quality.)


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PostPosted: Wed Jan 15, 2014 7:15 am 
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I used almost ti bolts in my bike and nothing failed or snapped for more than a year now. Just right amount of torque without indications and used some friction paste not on the bolts but on the parts clamping on each other. (6) M5x12mm ti bolts in my stem,M6x35mm on the headset lock, 13mm & 23.5mm brake recessed bolts, M5x12mm on the seatpost lock and replacement ti bolts for Thomson seatpost, all are 6AL4V ti bolts purchased in Ebay from Taiwan sellers.


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PostPosted: Wed Jan 15, 2014 7:30 am 
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Thanks guys for your inputs.

I found these:
1. http://www.tikore.com/titanium_facts.htm
2. http://faqload.com/faqs/bicycle-components/bolt-tuning-replacing-heavy-steel-bolts-with-titanium-aluminum-and-carbon-fiber

Which indicated that Titanium is slightly weaker than high tensile steel but still very strong.
I'm not sure what type of steel the factory bolts are as there no markings.
There website says "Corrosion-resistant steel bolts" which is a lie.

So I think when I get home from work, I think ill replace them with the titanium bolts and washers.

I apologize, when I say engineer, im more an electronic engineer than mechanical. Just making the point I can use a torque wrench.

Alan

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PostPosted: Wed Jan 15, 2014 8:12 am 
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I've been using titanium bolts on my Thomson stem for almost a year now. I'm no heavy rider though, only 70kg... Just make sure you use somekind of anti size paste on the bolts.


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PostPosted: Wed Jan 15, 2014 9:35 am 
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Please don't use cheap Ti bolts sourced from eBay with unknown quality and origin. There are loads of inferior and low quality Ti bolts floating around out there. These are suitable for clamping cables, holding bottle cages, and such. Get something of a known quality for all six stem bolts, all seatpost bolts and the seat clamp.

Grade 5, rolled threads.

The risk of snapping a high quality Ti bolt is slim, but the record shows that cheap Ti bolts in stem application are fairly prone to snapping, with severe injury to yourself at risk. In short, don't do it.

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PostPosted: Wed Jan 15, 2014 9:49 am 
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I went to Google and searched all over for something to back up the "tensile strength" issue. Looks like I was wrong to pass on such a general statement, as I found a variety of numbers, depending on the grades of steel and Ti.

I think @rick and @dmf have the best answers to the question.

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PostPosted: Wed Jan 15, 2014 11:40 am 
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Needless to say but I'll say it anyway. Make sure you use either anti-seize or grease on the bolts to get proper torque values.

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PostPosted: Wed Jan 15, 2014 2:19 pm 
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Not a wise place to look for gram savings.

My concerns would be creaking and pinging.

Titanium bends and is too soft.

Save grams in inner tubes where it matters (rotational weight).

Just an opinion.

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PostPosted: Wed Jan 15, 2014 2:22 pm 
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Just an FYI: the Bontrager RXXXL stem comes with Ti bolts all around (faceplate and clamp). You may want to contact Bontrager (or your local Trek dealer) to see if they sell the bolts seperately.

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Posted: Wed Jan 15, 2014 2:22 pm 


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PostPosted: Wed Jan 15, 2014 3:23 pm 
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Hi all.

@carbonlord
im not worried about the gram savings, more worried about corrosion.

@FIJIGabe
Looked this stem up online and it is factory supplied with steel bolts.


I also discovered my winter bike has an FSA stem with titanium bolts that came from tibolts.co.uk which aparentally are rubbish, but never had any issues.

Alan


Sent from my iPhone using Tapatalk

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