# Field repairs



## ki5ka (Dec 17, 2006)

Doesn't seem possible, but I think we rode like this for at least a minute before the chain departed from the rings. Did a little off-piste through some gnarl shortly before the event and I DO remember a particularly loud clunk from a good-sized rock bouncing up. 

Thank goodness there were a wide assortment of anvils and hammers to choose from  The field repair was successful and we were able to ride out!


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## PMK (Oct 12, 2004)

Been there, done that. 

FWIW, prior to our ride this morning, I had the front ring off and straightened it.

PK


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## Blaster1200 (Feb 20, 2004)

Did fully destroy the bash guards where they completely came off? 

I can't imagine an offroad tandem without bashguards protecting the timing chain rings.


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## patineto (Oct 28, 2005)

Blaster1200 said:


> Did fully destroy the bash guards where they completely came off?
> 
> I can't imagine an offroad tandem without bashguards protecting the timing chain rings.


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## patski (Dec 12, 2005)

*Taco'd ChainRing*

Annadel last weekend, don't remember any loud clunks in the gnarl, but...

On the last dip before the top I tacoed my CR when I jumped out of the saddle, I could feel it "fold".... extremely good luck, only maybe 30-50 feet of pushing over the summit and I coasted to the carpark, YEE HAW!


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## ki5ka (Dec 17, 2006)

I am inclined to agree with you. Guess I know what my next upgrade is going to be.


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## PMK (Oct 12, 2004)

I'm guessing the 4 bolt XT might be on a single with the linkage and carbon frame but maybe it is not a US machine.

I too have bent 4 bolt chainrings on a single. On a tandem, they might not hold up either.

We run 5 bolt 110mm cranks. No timing ring guards. We have bent several front timing rings over the years. Maybe it is time to research what is available in 110mm.

PK


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## patski (Dec 12, 2005)

1x10 on an Ibis Mojo SL, raceface 34T Chainring.



PMK said:


> I'm guessing the 4 bolt XT might be on a single with the linkage and carbon frame but maybe it is not a US machine.
> 
> I too have bent 4 bolt chainrings on a single. On a tandem, they might not hold up either.
> 
> ...


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## ki5ka (Dec 17, 2006)

So, ... took the chain ring off and straightened it, remounted it and went for a ride tonight. Hit a pointy rock on a speedy bit of downhill and pinch-flatted both tires. Didn't crash!  One hour 10 minutes and 5 repairs later, using a mini pump (the co2 inflater that I finally broke down and bought last week didn't even fill ONE tire!) and we still have a flat tire. Walk out was only a bit more than a mile, so not too bad. Good exercise, that's why we do this, right


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## SlowJoeCrow (Mar 16, 2009)

PMK said:


> I
> We run 5 bolt 110mm cranks. No timing ring guards. We have bent several front timing rings over the years. Maybe it is time to research what is available in 110mm.
> 
> PK


110mm 5 bolt is pretty common for cyclocross so there are lots of aluminum guards for 36-44 tooth rings.


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## mhopton (Nov 27, 2005)

ki5ka said:


> So, ... took the chain ring off and straightened it, remounted it and went for a ride tonight. Hit a pointy rock on a speedy bit of downhill and pinch-flatted both tires. Didn't crash!  One hour 10 minutes and 5 repairs later, using a mini pump (the co2 inflater that I finally broke down and bought last week didn't even fill ONE tire!) and we still have a flat tire. Walk out was only a bit more than a mile, so not too bad. Good exercise, that's why we do this, right


I'm chuckling this morning looking at these posts because we've all been there. The worse part is having an audience with your stoker standing over your shoulder giving direction.

Last fall we went thru a string of rides where every ride we had some sort of breakdown. It got to be pretty frustrating but, eventually our luck turned.

Have fun!

Sent from my SCH-I535 using Tapatalk


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## PMK (Oct 12, 2004)

SlowJoeCrow said:


> 110mm 5 bolt is pretty common for cyclocross so there are lots of aluminum guards for 36-44 tooth rings.


Just not willing to give up the clearance since we run 34t. I can make them but am just to lazy and usually just try to hit everything at an angle that won't sideload the chainring. More of a pain than a problem.

PK


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## rbs (Sep 30, 2008)

*5x v.s. 4x*



PMK said:


> I too have bent 4 bolt chainrings on a single.
> <snip>
> We run 5 bolt 110mm cranks. No timing ring guards. We have bent several front timing rings over the years. Maybe it is time to research what is available in 110mm.PK


Warning - non-tandem content....

I'll second that thinking. I have a fully rigid single single-speed (single[SUP]2[/SUP]-speed?) with 5x110x36T. I have hit my share of rocks and never bent the ring. I figure the chain makes a good enough guard to protect the teeth.

This winter I started riding a fully rigid fat bike SS using 4x104x34T. After the first two or three rides I was forced to add a bash guard when I kept bending the chain ring.

The only other difference is that the 5x110 is alloy and the 4x104 is stainless, so that could be a factor.

But I think that it is primarily that the extra distance and reduced support on the 4x crank makes it a lot easier to bend the ring.


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## PMK (Oct 12, 2004)

It's both, 4 bolt is not supported well at the impact point. We run Salsa SS timing rings, and they are softer than aluminum. Good or bad, they are easy to repair and hopefully will save the more rare Race Face tandem cranks from cracking.

Bashguard wise, we need something for less than 36t since we run 34t. Just for clearance, I suppose I could go with 28t and use the inner ring location and build some serious protection on the 110 holes.

All I know is that when you hit the front timing ring hard enough to stop a moving tandem, it is sometimes not pretty for the riders. The most recent time was riding on a wooden ramp structure upramp /entry, we fell to the side, dropping about 5 feet. Jeanne fell in thorns and was upside down unable to get the bike off her or put her hands to the ground on account of the thorns. Myself I took a good wack fro the frame as I hoped off, but tumbled like a 12 year old child gymnast doing back flips as I too went into the thorn bush.

Mostly caused because the suspension compressed just enough to have the front timing chainring hit the wooden crest and stop us pretty quick. Not enough momentum to ride it through.

PK


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## ki5ka (Dec 17, 2006)

YIKES. We have cactus and can relate to not being able to get up without help from your partner. SOunds like a nasty tumble.


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## mhopton (Nov 27, 2005)

Paul, I bet I know just the ramp structure you're taking about - the entrance into the vortex area at santos! I couldn't believe you rode over that on your tandem last year! 

Sent from my SM-G900V using Tapatalk


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## PMK (Oct 12, 2004)

No Mike, this wooden feature was on the Bunker Hill section at Johnathon Dickinson. On a single it is easily a jump. This was taller, but a softer landing, except for the thorns.

Actually the entire situation should have been straight forward and easy, but as the front wheel cleared the crest, clearance reduced and WHAM.

The ramp at Vortex is not bad, both people must focus and ride it smooth. Momentum helps too.

To practice stuff like that, sometimes we ride the edge of a sidewalk curb, The one thing with practice that she hates is riding the concrete drainage thing we have here on the edge of the roads. Nothing drastic or crazy, basically riding in a very shallow concave thing that is not deep. the bike is super unstable and wiggles as it tries to find a line. This freaks her out, but as yo have witnessed, she doesn't usually care about the back siding around in the dirt.

Practice hard stuff, and rides on new trails you have never seen sometimes become easier.

PK


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## ki5ka (Dec 17, 2006)

Just dropped the timing chain again last night... Thought I had straighten that ring out pretty precisely, but guess I'm going to have to replace that ring after all.


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## PMK (Oct 12, 2004)

Bent tooth...seen that before, just takes one to keep derailing inconstantly.

PK


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## ki5ka (Dec 17, 2006)

Trying to work out how the eccentric works... hopefully I get it worked out before anyone has a chance to reply, but just it case....


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## ki5ka (Dec 17, 2006)

OK, worked it out, but I'm sure I didn't do it the RIGHT way. Can't find any sort of manual on Ventana USA | Custom-American Made Mountain Bikes Am I missing it?


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## Okayfine (Sep 7, 2010)

http://www.bushnelltandems.com/eccinstructions.pdf


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## ki5ka (Dec 17, 2006)

Awesome, thanks!


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## ki5ka (Dec 17, 2006)

". Find the perfect medium point where the chain is not too loose or too tight," 

LOL, This was the question I had,... how much tension, ... that perfect medium spot, that is just so damn precise  Well, the timing chain didn't fall off today, so I guess it's not too loose! 

Not that I don't appreciate you pointing me to the link Okayfine!


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