Bicycle Mechanics - Changing gearing on new bike
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I'm trying to put an 11-32 MTB cassette on my Kona Jake. The Jake has a Tiagra rear derailler, which is spec'd for a max cog size of 27T. So I was planning to borrow the Deore derailler from my mountain bike for a while, but when I put the new cassette on, it seems like it works OK with the Tiagra derailler.
I haven't taken it down from the bike stand yet. Would I regret trying this for a while? Am I going to break something?
It looks like this:
08-03-08, 08:50 PM
meh, looks alright
if anything youll probably just fatigue the spring in the derailleur faster. but it doesnt look 'that' bad.
if your really that worried about it just swap it for a mtb der.
Well, I was hoping to hear that it would be OK. I hope not to spend a lot of time in that gear anyway. :)
08-03-08, 09:28 PM
I've been using an 11-32 on my Cross Check with Tiagra. 1000 miles or so with no problems. I just recently got a second wheelset and found that with the deraileur adjusted for the 11-32, I can swap out the wheel for one with a 12-25 without adjusting a thing.
I just recently got a second wheelset and found that with the deraileur adjusted for the 11-32, I can swap out the wheel for one with a 12-25 without adjusting a thing.
Fantastic. That's exactly what I hope to do, long term. The cassette I just took off was 12-25. I'm getting geared up (pun intended) for a century in a couple of weeks that has about a 450 foot climb at around mile 80, and I'm just not that strong a climber. On the other hand, I love the 12-25 for my daily commute. Now throw in the fact that I want to switch between road tires and the stock CX tires quickly, and there's another pair of wheels in my future.
The big question was whether I'd be able to do that with the Tiagra derailleur or if I'd have to move to a Deore.
08-03-08, 10:37 PM
What ring are you on in the pic?
I looked at 2007 Jake spec's and it said it had a 30-39-53T triple.
That's a toot differential of 23T+ the 21T differential of the cassette makes a total of 44T wrap capacity needed. The Tiagra GS is listed as a 37T cpacity.
IF your chain is PROPERLY sized for the Big:Big combo, it'll probably be close to dragging on the pavement in Small:Small.
I'm on the middle ring in the pic. I've got the 2008 Jake, which has 30-39-50
I haven't really put much thought into the chain length yet -- it's very likely not properly sized.
Since I won't be using the big:big or little:little combos I don't expect that to be much of an issue. Everything looked OK shifted through all the cogs on the middle chainring. I typically only use the big chainring with the three or four smallest cogs and the small chainring with the two or three biggest cogs, and even those only rarely. I'm mostly a middle chainring kind of rider.
08-04-08, 03:33 AM
I'm a middle ring kind of guy too, but accidents happen.
" I haven't taken it down from the bike stand yet. Would I regret trying this for a while? Am I going to break something?"
I appreciate that, and I see your point.
So it looks like this on the big-big combination:
and like this on little-little:
It still has tension in the little-little combination, so that looks OK to me. But as I was playing with it a little more, I noticed that it's got a little bit of a "hop" in the little chainring-big cog combination. That is, whenever it hits one of the wide teeth, the derailleur gets pushed back for a moment.
Now, I understand that those teeth are there to get me out of this gear and the hop will do that, but will this go away if I swap in a Deore derailleur made for this size cog?
08-04-08, 09:38 AM
It looks like you're just squeaking by on the big-big combo. If it shifts into and out of that combo without a lot of crunchy sounds then you just made it on the safe side and can use the Tiagra without any issue. Even if it makes light crunchy sounds but shifts into and out without the chain getting really tight (check it for up and down play while the chain is crossing teeth at either end) it'll be OK since it's not actually going hard tight to the point of jamming. If it DOES go guitar string tight and you can feel definite harder resistance as it crosses into and out of the engagement then you're straining the chain and components and should consider a switch or just be extra careful to avoid the big-big combo.
As for the lack of tension on the small-small combo who cares? You'll never (shouldn't) ride in that combo anyway. And technically you should never be in the big-big combo either but as Bill says accidents happen and it's nice to know it won't bust a button if you select that combo in a moment of non thinking.
Outside of that just stay attentive so you don't cross chain and it'll work marvelously
08-04-08, 09:47 AM
.IF your chain is PROPERLY sized for the Big:Big combo, it'll probably be close to dragging on the pavement in Small:Small.
That's not important. Allowing big-big is a mechanical necessity. Not that you should use it but an inadvertent shift can do a lot of damage if the chain is too short. Small-small is a useless combination but having the chain too slack in it is not a hazard.
So what about the hop in the big-little situation? Does anybody have an opinion on that?
08-04-08, 11:34 AM
Big - big doesn't look so good, but you shouldn't use that anyway. Adjusting your B screw might take care of your hop.
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