29.76 lbs Trek Session 88
- Thread starter Cyklist
- Start date
It works for you, but I'd guess you'd loose your rotor if even one of the three bolts loosened up...Forgive me for posting my real world experience.
Also, if the bolts DID see shear, you'd notice the bolt threads would get damaged where the rotor hits them. I have not noticed that on my steel rotor bolts.
Interesting that Ti torque values are the same as steel, not sure that makes sense, as you usually torque bolts to around 75% of the force required to permanently deform them.
Anyway, thanks for posting, maybe I'll have to go find some Ti rotor bolts
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They are held in via 262 (high strength) loctite. The only thing I'll lose is those bolts when I realise I need a vice to remove them.
I guess it's everyone's decision to decide what works for them though... the OP's bike wouldn't work for me but I'm sure it works for him and the riding he does. Just think it's a little silly to brag about it in the "DH" forum.
I actually have noticed bolt damage on steel rotor bolts where the rotor contacts the threads (not enough to cause concern though)... the titanium bolts (avid) don't do that though from what I can see, because there are no threads contacting the rotor. The bolt has a short flat section before the threads start for the rotor to sit on.
As for the torque thing, I think torque recommendations are given in regards to what is required to fasten the part rather than a percentage of what it takes to deform the fastener. You're probably thinking of max torque for a fastener rather than a part (eg. if you torque crown bolts to 75% of their capacity instead of what is recommended, you'd probably stretch the clamp).
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Some interesting info. from a Ti bolt mfg... apparently they can make bolts that are as strong as steel:
Technical Information & Torque Specifications
All of our bolts are made with aircraft grade Titanium Alloy. One of the outstanding benefits of Mettec bolts is that we forge the heads for superior strength. The threads are then rolled to produce greater fatigue strength and reduce galling.
Our bolts exceed minimum Ultimate Tensile Strength (UTS) of 120,000 psi. Mettec can also make titanium bolts that exceed 160,000 psi in Ultimate Tensile Strength (UTS). Both styles of bolts conform to DIN and ASTM specifications. Titanium bolts can replace both grade 5 and grade 8 steel bolts which have minimum UTS requirements of 120,000 psi and 150,000 psi respectively. Metric bolts with an 8.8 rating can be replaced with titanium while bolts with a 10.9 rating can sometimes be replaced with titanium depending on intended use. Any bolts with a rating over 10.9 rating should not be replaced with titanium.
Technical Information & Torque Specifications
All of our bolts are made with aircraft grade Titanium Alloy. One of the outstanding benefits of Mettec bolts is that we forge the heads for superior strength. The threads are then rolled to produce greater fatigue strength and reduce galling.
Our bolts exceed minimum Ultimate Tensile Strength (UTS) of 120,000 psi. Mettec can also make titanium bolts that exceed 160,000 psi in Ultimate Tensile Strength (UTS). Both styles of bolts conform to DIN and ASTM specifications. Titanium bolts can replace both grade 5 and grade 8 steel bolts which have minimum UTS requirements of 120,000 psi and 150,000 psi respectively. Metric bolts with an 8.8 rating can be replaced with titanium while bolts with a 10.9 rating can sometimes be replaced with titanium depending on intended use. Any bolts with a rating over 10.9 rating should not be replaced with titanium.
why would it be different? something should be torqued at a lower rate because it is a different material?
clamping forces are the same no matter what material. am i right on that?
problem resolved
Scary part here about that statement....... Automotive has been using torque to yeild tech for some time now. Simply put, that means your going to tighten your fastner as tight as possible without breaking... Yes you are deforming it, and cannot reuse it. Mostly you see this on the head bolts, main bolts, and rod cap bolts.....Now here is the reasoning and method.... Reason for this is you end up with a more evenly torqued part in which holding pressures will remain more constant longer. Method is a little spooky, first you torque to a low value specified by what is being tightened, then you use an angle meter and turn so many degrees further. You can sometimes feel as the bolt starts to strecth just a bit as you reach that final stopping point....... Either that method, or you find breakaway bolts, and these are what I am worried about in the biking world.....
Interesting that Ti torque values are the same as steel, not sure that makes sense, as you usually torque bolts to around 75% of the force required to permanently deform them.
Break away bolts are a one time use bolt, that you CANNOT over tighten, and you know for a fact when its tight..... the end breaks off when your tight. Simpl to use, install, tighten till it breaks, all bolts are evenly torqued........ I just have it stuck in my head that we will start seeing these in the biking world over the next few years......
Torque values would be different if the tensile strength of the material is different. For example, aluminum has 1/4 the strength of steel, so your torque values would need to be lower than with a steel bolt so the aluminum bolt doesn't fail. The Ti alloys used my Mettec have similar strength to steel, so the torque values should be similar.
Mike, TTY bolts are more accurate than conventional fastening, when the bolt is yielding, the clamping force is closer to constant than in the elastic region before the bolt permanently deforms. Torque wrenches are typically only +/- 25% accurate in achieving the clamping force desired. I'm not sure how accurate TTY is, but looking at stress/strain graphs I'd guess its far better than 25%. I've never used breakaway bolts, sounds interesting...
Can you please provide the weights for the parts on your list?
I still have trouble seeing how it can be so light with these parts unless the tires are 800 g each. Not hating, just curious (and maybe missing something).
I still have trouble seeing how it can be so light with these parts unless the tires are 800 g each. Not hating, just curious (and maybe missing something).
What does customized XTR cranks mean? Does it mean you're shaving more strength off the cranks by doing the Ti swap?
I'm not hating just making a joke! Hey man if that rig works for you rock that $hit.
I bet that thing rides gangsta in a bike park say on a jump trail!
I'm not hating just making a joke! Hey man if that rig works for you rock that $hit.
I bet that thing rides gangsta in a bike park say on a jump trail!
Tubeless? Thats the 400g you are missing maybe?
Ive had breakaway bolts fail in two of the last three engines Ive built... I hope to god we dont start seeing them in the bike world
Mr. Average Joe is buying these uber expensive race bikes. Go to any race and you will see half the sport class on bikes that make my dh comp want to go lock itself in the closet. And its average joe who doesnt know how to crash and ends up destroying stuff. Its also average joe who doesnt replace the frames every year. So in time Im sure we will see the frames really start to fail. Im a middle of the road expert rider and I know that I couldnt get a couple of these freak light bikes to last me long enough to pay them off my credit card.
"average joe who doesnt know how to crash "
There's a good way to crash?
There's a good way to crash?
wouldnt a large part of how light of a bike you could get away with downhilling on have to do with the rider's weight? but that is a very nice spec'd bike sir!
Yeah I get TTY, I have to deal with them ALOT at my regular job, Hell there are TTY Nutts as well. Break away are actually pretty cool, they will be stepped a bit and the head will litteraly snap off when they are at the proepr torque, leaving a nice fitting flange. There are a few methods of removing them, couple of them use a special tool, personally I just grab a small cold chisel gove a little tap then roll them out by hand.... Def not something you want to see that is serviced regularly.... See these alot in steering columns. Very easy to use, Ill see If I can dig up a photo
EDIT...
Breakawat Nutt
Breakaway bolt
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Just wow.
Why would anyone want or even need a license to practice professional engineering when the technical joy found in Ridemonkey Forums are just an internet connection away?
Rhetorical question. I digress.
Please, practice away.
Why would anyone want or even need a license to practice professional engineering when the technical joy found in Ridemonkey Forums are just an internet connection away?
Rhetorical question. I digress.
Please, practice away.
Yes, the "RM" stamped into that bolt does stand for Ridemonkey.
I would run other Cranks and spokes just so its not SO light but the choice is you other than that just seems like a nice build.
Zark, you rock that is funny stuff
i think the trek is cool, but i weigh very little. however, mine is still quite a bit heavier than that.
to me weight is a factor but it is how it rides that matters, i have never been on one so, i won't judge either way.
be proud and happy with your ride.....
I bet he's out riding it instead of trolling up 8 month old thread.So the question is Cykist, how did the bike hold up? Are those XTR cranks still straight? Has your Stans Flow rim taken the same beating that mine does if I go near a rocky track on it? Smashed the lower guide off yet?
Angry much?
Since you're going all out with that there XC rig, why don't you run an air rear shock? considering some of the compromises you've made in strength and handling i don't know why you'd bother running a coil rear
then that might make it the "worlds lightest dh bike"
I don't think the Vivid air was available when he built the bike, at least not here, and the other air shocks seems a bit crap.
When I when I saw the bike end of last season it seemed like it had held up just fine.
When I when I saw the bike end of last season it seemed like it had held up just fine.
Wouldn't say I'm trolling - I re-stumbled on this old thread while searching for something else, and thought it'd be interesting to see how well this 30lb bike had coped with Cykist's season! I'm not hating on him at all, I'm as big a weight weenie as anyone here, I've just not taken it to quite such extremes. If I had more money I probably would have... barring the caveats I raised earlier in this thread, which come from my own personal experience (bending XTR cranks very easily, etc).
Nice build! I've built a lot of wheels off of Tune King/Kong MK hubs and they're bar-none my favorite on the market right now. The only thing I'd change would be to offer them with aluminum freehub bodies - Tune insist on shipping them only with Ti ones and it drives the price up 
The bikes been great.So the question is Cykist, how did the bike hold up? Are those XTR cranks still straight? Has your Stans Flow rim taken the same beating that mine does if I go near a rocky track on it? Smashed the lower guide off yet?
Rides like a dream, it's really so much fun.
Haven't broken anything at all, not even in a few pretty heavy crashes or when I've clipped the pedal.
As expected I've had to true the wheels a few times, got dents in the rims and also got a little dent in the frame but that doesn't bother me at all.
Except for that I've just been riding different tires at times and as planned I put on lock-on grips when the rain was too bad.
Actually it's been so good that I'll be riding pretty much the exact same setup this season too. Might be a few very small changes but not much. Only things at the moment are that I want slightly wider bars and also I'll try a Vivid Air.
Will you be riding the same frame for 2011, or will you get a fresh one, like in the 2010 season?
Sorry for potentially opening an old can of worms but this Cyklist guy has been building a DH bike again: https://m.pinkbike.com/news/the-british-racing-green-project-scott-gambler-spark-custom.html13.50kg/29.76lbs with 2.5" UST Swampthings and coil rear shock.
Frame: Trek Session 88 size M
Rear shock: Fox RC4 with Diverse ti-spring
Fork: RS Boxxer WC
Headset: CaneCreek
Spacers: PointOneRacing
Topcap: Carbon with alu bolt
Stem: PointOneRacing LTD
Handlebar: Truvativ Holzfeller WC polished
Grips: Bontrager XXX Lite with plastic plugs
Brakes: Avid Elixir CR Mag with ti hardware etc
Discs: Formula R1 SL 180mm with ti bolts
Shifter: Customized Shimano XTR with alu bolts
Derailleur: Customized Shimano XTR
Housing/Cable: Yumeya/Powercordz
Chain: KMC X10SL
Cassette: 7speed DuraAce 11-21 with alu lock-ring
Chainring: E13 Guidering
Crankset: Customized Shimano XTR
Pedals: Superstar Ultra MAG
Chainguide: Customized LG1+
Seatclamp: Hope
Seat/Post: Stripped I-Fly/Carbon micro post with ti hardware
Hubs: Tune King/Kong MK
Spokes: DT Swiss Aero Lite with alu nipples
Rims: NoTubes Flow
Tires: Maxxis Swampthing UST 2,5"
Plus more ti and some other small things.
Think I’ve seen enough
don't look there, there is a Gambler too without chainguide and with a lot of shiny bits, quite a lot indeed...
I had already scrolled past the Cylon fork and hideous wheels when I reached the high point of that seatpost. That VW product placement was so subtle and fitting too, just like everybody else, when I hear British racing green, I immediately think of the holy trinity: MGB, E Type, Tiguan.
Was the point of these builds lightness again? He must have loved finding out about the new featherweight Gambler while he was halfway done sanding down a frame consisting of 50% pivots and links.
Was the point of these builds lightness again? He must have loved finding out about the new featherweight Gambler while he was halfway done sanding down a frame consisting of 50% pivots and links.
Maybe the guy needs some attention?
if not for the super ugly stem I kinda dig the look of the gambler. It seems to be lacking a few accents to make it look complete but i like the retro race car idea.
Also the builds make me realize me I need more money so I can spend it better than strange builds
Also the builds make me realize me I need more money so I can spend it better than strange builds
The point was, he works at a bike shop and likes to make sick bikes. These weren’t about a crazy light weight goal but more about the thick clear coat paint jobs.
He knew about the new frame because when he started this project the DH team was already on the new one. He has the carbon swing arm making it a 3.4 kg frame set. The new V10, Commençal, Devinci and Intense are all heavier than that and have the same amount of pivots.
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