Budget Hardtail XC Build USD$1000 - 100% COMPLETED

Discuss light weight issues concerning mountain bikes & parts.

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stockae92
Posts: 270
Joined: Fri Sep 25, 2015 5:13 pm

by stockae92

best of luck with the bike.

the idea of taking away material to the extreme to save weight without R&D + being reliable doesn't really go along too well.

Erwandy
Posts: 44
Joined: Mon Jul 27, 2015 2:14 pm

by Erwandy

stockae92 wrote:
Thu Jan 04, 2018 12:59 am
best of luck with the bike.

the idea of taking away material to the extreme to save weight without R&D + being reliable doesn't really go along too well.
Thanks. The things done on this bike is R&D itself yes? gotta start somewhere LOL

by Weenie


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Klaster1
Posts: 213
Joined: Mon Aug 15, 2016 10:25 am
Location: Krasnoyarsk, Russia

by Klaster1

Erwandy wrote:
Thu Dec 21, 2017 1:24 am
Once I have the funds I will go for DuraAce version
I'd like to see how light the DA RD can go. Is it going to be a 9000 or 9100? Did you plan where to remove material from yet?

Erwandy
Posts: 44
Joined: Mon Jul 27, 2015 2:14 pm

by Erwandy

Klaster1 wrote:
Fri Jan 05, 2018 1:55 pm
Erwandy wrote:
Thu Dec 21, 2017 1:24 am
Once I have the funds I will go for DuraAce version
I'd like to see how light the DA RD can go. Is it going to be a 9000 or 9100? Did you plan where to remove material from yet?
I'd prefer 9100 - because the newer version uses Shimano Shadow+ design. With Dura-Ace, I reckon there's no need to hack/grind the RD itself - it is already super light in stock form. Probably just mod the cage and pulleys. But this have to wait until I have the funds. For now I am keeping the budget within the $1000 mark

ooo
Posts: 509
Joined: Sat May 21, 2016 12:59 pm

by ooo

for lighter cable housing you can try Jagwire Link/ Nokon/ Alligator i-Link/ Aican Bungarus/ etc
'

Erwandy
Posts: 44
Joined: Mon Jul 27, 2015 2:14 pm

by Erwandy

ooo wrote:
Fri Jan 05, 2018 3:47 pm
for lighter cable housing you can try Jagwire Link/ Nokon/ Alligator i-Link/ Aican Bungarus/ etc
Thanks. I'll look into those.

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Willier
Posts: 1537
Joined: Wed Dec 21, 2005 4:37 pm

by Willier

I sent you a pm about pedals... Can you give review about them?
"Smart may have the answers, but stupid have all the interesting questions."

Erwandy
Posts: 44
Joined: Mon Jul 27, 2015 2:14 pm

by Erwandy

Willier wrote:
Fri Jan 05, 2018 7:21 pm
I sent you a pm about pedals... Can you give review about them?
PM replied :D

joshpeck
Posts: 25
Joined: Thu Jan 11, 2018 11:02 pm

by joshpeck

has the drivetrain held up?

Erwandy
Posts: 44
Joined: Mon Jul 27, 2015 2:14 pm

by Erwandy

joshpeck wrote:
Thu Jan 11, 2018 11:13 pm
has the drivetrain held up?
So far so good. I must admit there's some issue shifting between 36-42 due to cog gap issue - my own fault for indexing them not quite neat as how it was before (spacer removed in favor of gaping with rivets instead). 50t will flex under heavy load but nothing dramatic - I guess with the flexing some efficiency is wasted too (too micro to tell the difference).

Give it another month or two of heavy climbing and I would be able to tell more

Erwandy
Posts: 44
Joined: Mon Jul 27, 2015 2:14 pm

by Erwandy

Final Stage: Race Wheels

This has been delayed due to commitments at the turn of new year. But it is all done now. Cost me USD$95 and thus kept the overall budget well within $1K allowance. The rims are Stan's ZTR Podium MMX with a cheap Taiwanese Fastace hubs and DT Swiss Revolution spokes. Kept the price low for the whole thing by buying used at super bargain price.

The hubs were bought new: ....and modded extensively to reduce weight.
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No surprise there. 508g is a very common weight for commoner bikes

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Yes I know you will wince and cringe. I have been running 4 bolts setup since 2015. This time pushing it to 3 bolts :D

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And so the finished product weight is nothing to shout about at 422g. But for a $50 hubs I can live with it for now

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Laced and assembled. 1310g is not too shabby for a $95 wheelset yes?

I just love the fatty and rounder look of those tires on the Podium 21.4mm wide rims. Looked a lot fuller.
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..the kittens admiring the bike as well hahaha

So what's the final weight?
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* went to the local bike shop and asked them to weigh my bike using Parktool bike scale.
8.58KG feels very satisfying, considering this bike only cost $1K (slightly more at $1080ish).

That's all for now. The next stage is to grind this baby on XC courses. Hope all goes well. Thanks!

Erwandy
Posts: 44
Joined: Mon Jul 27, 2015 2:14 pm

by Erwandy

Update:

DISASTER! took her out today to my favorite forest park for the first real shakedowns. Up until now I have been running leisure pace. But today I decided to shift it up to racing speed and intensity. Unfortunately things started to break.

- First the 50t cog was literally sheared out of the spider while grinding a very steep climb. The failed points were the aluminum rivets that was unable to hold up under heavy load

- Second, rear derailleur hanger took extreme damage due to chain drag. Apparently the highly modified middle cogs flexed a lot under heavy pedaling - of which the flexing motion caused the chain to rub with the neighboring cog and in turn seized the chain at extreme angle - the end product being the RD and RD cage dragged backwards

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Makeshift repair done to limp my way out of the trail...
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But eventually the RD hanger snapped off clean after that due to strain.

Lesson learnt the hard way. Excessive modification of cassette is NOT a good idea. And don't ever use aluminum rivets for high strain area. Licking my wounds now. Need to find a replacement cassette & RD hanger. The Ultegra RD turned out to be still okay, just the cage bent and require replacement of jockey wheels, this further boosted my confidence in Shimano's durability.

I'd probably stick with 42t as it seems that with 8.5kg, the bike felt really good even on very steep climbs. Weight really does have influence on climbing prowess.

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F45
Posts: 869
Joined: Wed Jun 08, 2011 6:08 am

by F45

When a part is designed, the engineers will do stress analyses and then put something in called a safety factor. Usually the safety factor is 2 unless it's an airplane, then it's like 1.5.

What you're doing is reducing the safety factor to 1 or below with your grinder, but you don't know what exactly because you haven't done a single calculation, test, or simulation.

And now your bike broke on the first ride.

What did we learn?

Or is it going to take a face plant to knock some sense into you?

Erwandy
Posts: 44
Joined: Mon Jul 27, 2015 2:14 pm

by Erwandy

F45 wrote:
Mon Jan 15, 2018 12:00 am
When a part is designed, the engineers will do stress analyses and then put something in called a safety factor. Usually the safety factor is 2 unless it's an airplane, then it's like 1.5.

What you're doing is reducing the safety factor to 1 or below with your grinder, but you don't know what exactly because you haven't done a single calculation, test, or simulation.

And now your bike broke on the first ride.

What did we learn?

Or is it going to take a face plant to knock some sense into you?
When I first started this project and sharing it online, I knew that I have opened up a Pandora box. What I have done was basically realizing the "what ifs".

There's nothing in what I have done so far would constitute as being sensible - because if I were to stick to that line this project would have faltered even at conception stage.

My wife actually spend a good 30 minutes lecturing me on the folly of my actions when she picked me up from the bike park with a broken bike. She has always been the most sensible person that I have ever known. But we had a good laugh after that, because she knew me the best. Even at age 43 and with my eldest daughter turned 19 this year, I am still a kid with a loaded toolbox.

When the parts broke, I told myself that I need to report this back on the forum - despite knowing for a fact that people will laugh at me. But not sharing failure story is morally incorrect. At the very least I gave reasons for people to laugh, that's a good thing. And I laugh too at the folly of my action.

It has been said many times that we learn better when we fail. I have learned my lessons, being stubborn as a mule that I am, this will not be my last project, this is my own way of doing "R&D". And I take this experience to ensure that I am fully aware of what NOT to do when I start that other project (probably a $4000 29er build).

PS:
I would never do this to anybody else bikes. I took my chances and so I should shoulder the risks, not anyone else

by Weenie


ooo
Posts: 509
Joined: Sat May 21, 2016 12:59 pm

by ooo

Safer approach is to build heavy bike and work with parts 1 by 1 with test riding between changes - but this is very slow
Your approach is reverse, much faster, probably make sense to wear extra protection for testing period.
If we forget about safety, other downside is that some problems can have a consequences (other problems) and it may be hard to figure out what happened first

I have some concerns was about shifting quality - ultegra shifts slow on mtb cassette, i would not go more than 11-32
and while your bike have testing period, may be you don't need high top speed? you can use 32x11-32 or lower combo

about modification - I am worried about stem. it may be ok for road use with suspension for, but not for offroad use,
in some places suspension fork and air in wheel will be not enough to save it from failing...
'

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