carthusian

Howdy. Currently running an 11-34 nine speed cassette with my SRAM X.9 long cage RD. I want to replace the 11-34 with an 11-36, but everything I'm reading says the RD is capped at a 34 tooth max. Is that an absolute limit, or is there sufficient wiggle room in the spec to permit use of the 11-36? The RD is probably 15 years old. If the current one can't handle the 11-36 spread, might newer generations of 9-speed RD's? Or am I forced to upgrade to 10 speeds? Thanks!

fietsbob

Have you tried it , first? crank on that B screw ..
Math Q: what is the radial difference between 34 & 36t
hint: a chain link is 0.5" between pin centers..

There is a 'wolf tooth' thing ,you guys talk about, to move the RD mount down a bit lower

carthusian

I thought I would ask, first. Since I'm a novice mechanic and have never swapped a cassette before, the first time will of course be a challenge. On the one hand, there would be inherent value to the experience regardless of the outcome. On the other, I want to avoid an exercise in futility.

jwh20

If it works with an 11-34, then it's likely that it will work with 11-36 as well. There is a bit of "slop" in the specs and no bike manufacturer makes their bikes at the limit of the component's range. It's worth a try and my guess is that it will work, worst case you'll need a new chain with another link.

fietsbob

Bike mechanics books are a good thing to own. ,

but the public library can loan you some..

dsbrantjr

You will need to carefully check that your chain is long enough to engage the big chain ring/big cassette cog combination, even if you never intend to use it. You may forget, try it, and it will be too late to avoid damage from a too-short chain.

djb

as someone new to bike mechanics, I highly recommend the Park Tools video series. Parks are one of the highest regarded tool companies, and they make a whole slew of very well done and reliable info vids on how to do stuff. Easy to find on the net, and you can find one showing how to check chain length.

and yes, a 2 tooth diff is pretty small so really shouldnt be a problem for the derailleur, but is it worth the change , the cassette cost just for 2 teeth? Or are you replacing a worn cassette and or changing chainrings also to get lower gearing?

If only changing the cassette where the 34 one is in good shape, the lowering of gearing is pretty darn small and a cassette will cost you X dollars, depending on the cassette, here in canada, probably min. $40 and upwards.

If you do this, along with verifying chain length, look into reading about the B screw on a rear derailleur, as you may have to slightly adjust yours to move the rd away a bit down from the slightly larger 36 cog diameter cmpared to the 34. Again, look up b screw stuff to understand the concept.

carthusian

All great tips. Thank you. I've recently subscribed to Park's YouTube videos. Also have their Blue Book, Plus Zinn's book on bike mechanics. The one on RD adjustment was really solid, I thought. I'm really close to getting the bottom I need, so am hoping that the two teeth will just about get me there. I couldn't go lower on the front end without a more major investment than the cassette, since the 24 tooth granny is the smallest I can get with a 74 BCD, so I thought I'd give this a shot. Also seemed like a feasible project for a noob.

djb

what crankset are you using? Im a real touring guy so can offer good advice on touring gearing.
Look at either the sheldon brown gear calculator, or the "html gear calculator" search result, its the first one, ritzel something....
and play iwth both of them, putting in the proper info, wheel size etc, and you can see the actual gear inches number for each gear, specifically your low gear, to see the diff between the 34 tooth and 36.
without knowing your bike, wheel size, tire size, i cant look at it for you, but if you want, give us that info and then we can go from there.

also, how much load you carry touring, and the terrain, all is a factor of your low gear and what is workable for you.

in any case, getting your hands dirty and doing some bike mechanics is just a plain good idea , to be more aware of your bikes condition, how to do stuff, and how to keep it in good working order, especially if touring is in the cards for you--if you are going to be touring, let us know, as I can make gearing recommendations and give examples of my experience with gearing and touring over the years.

carthusian

Thanks, djb. The gearing isn't for a touring application, but for a long wheelbase recumbent. It's low-slung, with a fairing, but a heavy bast*ard. So I need low gears because it climbs poorly, and high gears for the flats because I can run out of gears pretty quickly on anything more than a 2% downhill. I'm running a 50-38-24 130/74BCD 165mm 105 crankset and FD up front and an 11-34 in the back, giving me 18-118 GI. In a perfect world, 15-120 would probably serve. I didn't want to start with the crankset because, as hard as it is in general to find 165mm triple cranks, it's really hard to find a pair compatible with the 104 or 96-58 BCD setup I'd need in order to use anything less than a 24 tooth granny. I've considered the Mountain Tamer, though, which would allow me to get down to 18 teeth on a 74 BCD setup. On the upside, the recumbent chain is so long that it permits you to run your FD wildly beyond its spec'd capacity. I've read reports on bentrideronline of folks running a 52-42-20 with no problem using the same 105 FD I have. Unmodified.

Since I still can't post links, I'll just say that if you search "mike sherman gear calculator," you'll find a really impressive tool for playing around with the numbers. And if you search for "gearmaster.xls," the third entry down brings you to John Denman's marvelous Triketech site and access to a spreadsheet which, though geared to folks contemplating IGH's, permits GI calculations for derailleured setups. Those have been my go-to's of late, although I'm sure there are a million others.

djb

ah, a recumbent, interesting.
Perhaps at some point in the future, you could look at going to 10 speed or more, as 11-42 and even larger cassettes are becoming the norm, though of course a diff setup rd wise would be needed, but might be worth it at some point if thats what makes the recumbant more useable enjoyable.
have fun mucking around with options

Retro Grouch 

There's wiggle room but, contrary to the belief of many, the length of the arm isn't the determining factor.

If it was my bike, I'd slap on the new cassette and see if I could get the top pulley to clear the biggest cog. You'll probably have to dial in the "B" screw a little. If you run out of threads you can take the screw completely out and screw it in from the other direction to give you a little more scope.

Assuming you can make that work, be aware of your chain length. It's important that your chain be long enough to safely cover the big/big combination. If you ever inadvertently shift into the big/big, even once, with a too short chain, you can do hundreds of dollars damage to your bike in less time than it took me to type this sentence. A new longer chain (which you really should install to go with new cogs anyway) is cheap insurance.