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one ring up front--need a derailleur?(16 posts)

one ring up front--need a derailleur?Ross
May 28, 2001 11:41 AM
hi. just built up a new cross toy with one ring in the front and nine in back. do i need a front derailleur? i know that in theory it would help the chain from hopping off, but how likely is this? the bike sure looks good without the extra metal, but i obviously don't want to kick off the chain every time i go over a bump. thanks
May 29, 2001 5:10 PM
In short time your chain will be off. You can either use a derauiller, or there have been products available periodically in the past to substitute for it. I've been planning on just making a unit out of carbon as a guard on my TT bike, but for the activity involved in cross racing you need the security of a full derauiller.
re: one ring up front--need a derailleur?ctxcrossx
May 30, 2001 9:21 AM
This is a typical setup for a downhill bike. They do make chainring guides for downhill bikes. The only problem you are likely to face is that of compatibility. Also, you won't save any weight since these products are meant to take downhill abuse. Good luck!

there was an old retrogrouch setup like this...lonefrontranger
May 30, 2001 10:18 PM
My old coach used to have an Alan with one chainring, and he said this was a common setup in the 70s & early 80s. It didn't have a front mech. It had some type of elaborate drilled-out (naturally) alloy chainguard setup. It looked very much like the present day DH ring guard, only very much lighter and tricker. The Alan set up with wheezy old Campy Victory 5-speed bits weighed somewhere between 16 and 17 lbs (no lie, it had some trick tubie wheels and he is a flyweight, but still!). I imagine you could still find these things out there somewhere, but my memory of the bike is shaky (he ripped the rear dropout off it ohh, about six years ago now).

If single-ring catches on again, you can bet your Northwaves some hip little machine house like Real or Paul's will come up with a takeoff of this part, similar to the "Mr Grumpy" right angled cantilevers, which are a takeoff on the old 70s Mafacs, a viciously effective evil bike bit designed strictly in order to gash your right ankle on the way over the saddle.
Not retrogrouch at allgeetee
May 31, 2001 10:23 AM
Have a look:
May 31, 2001 10:22 PM
Your knowledge is bigger than mine. I must get more knowledge...

Great catch! I'm glad SOMEbody actually knew what I was talking about. Most of the time I wonder if I'm just off on some arrant raving tangent that stems from too much lactic acid poisoning over the years.
there was an old retrogrouch setup like this...stoke
May 31, 2001 8:14 PM
ground down CR for the outside and third eye for the inside... works like a charm
May 31, 2001 7:20 PM
I'm using a singlespeed stup right now for road 40-15...spin great at 18mph..I'm going to 40-{12-32} XT cassete & Derailer .i believe the single front chainring is great !
as far as won't fall off unless your gettin it !
I'm going to set up a derailleur systemclimbo
Jun 1, 2001 7:07 AM
With a single ring, using a full cassette there might be some chain rub on the derailleur but I will be running a Campy set-up so I can trim it as I shift up and down. Hopefully this will work fine, then if I need to put on another ring to do some singletrack riding I won't have to do much work on the bike to set it up. Just a thought, I'll let you know if it works.
hey climbolonefrontranger
Jun 2, 2001 6:52 AM
my .02 if you're interested in saving a small, but significant amount of weight (this from someone who owns a 26.4 lb. 50cm bike, but anyway):

I'd remove the screw from the front mech plate to widen it slightly - all it needs to do is keep the chain from falling off, it doesn't actually need to guide it. Mebbe just bend it a bit if you're not going to use it for anything else.

Then I'd replace the left hand brifter with an aero brake lever from the bad old days of down tube shifting. I know I have some lying around in the garage, plus the two on my fixed-gear. There's quite a bit of weight hanging out in those newfangled Ergo / STI levers, although they've significantly reduced it from what it was back in '94 when I got my first set. I remember sitting in the garage, holding an aero brake lever in one hand, and a Chorus Ergo in the other, wondering what all the fuss was about and if I'd wasted my money.

Of course this defeats the purpose if you plan on adding rings back occasionally, but it shaves much more weight than just removing rings alone.
hey climboclimbo
Jun 4, 2001 6:43 AM
might try that, I have some old Shimano levers lying around somewhere. I too am going from a 26 lb single speed 70's 'cross bike to a new bike this year so to me it will seem light as a feather!
plastic anti-chain drop device (more)swede16
Jun 2, 2001 11:47 PM
I read, I think in VeloNews, that many of the racers in Paris - Roubaix were using a plastic device mounted onto the seat tube which would prevent the chain from dropping. I don't recall the name of the manufacturer. But it piqued my curiousity for potential cross use with a single chain ring, thus eliminating the need for either the derailleur (and shifter and cables) or chain ring guards.
This is it...pauly
Jun 4, 2001 10:34 AM

Looks totally 'DIY'-able, though.
plastic anti-chain drop device (more)psychodan
Jun 5, 2001 6:29 PM
There's a couple of these devices extant, one being the "third eye chain watcher". They are great for preventing the chain from dropping to the inside ( when shifting down to the small ring) but useless in preventing the chain from going off to the outside.
Jun 1, 2001 8:58 AM
hey. thanks for all of the help. just as a follow up, i went out for a ride yesterday, mostly on smooth dirt. no problems with the chain at all. about 1 mile out from home, i bunny hop a curb, and hit my rear wheel hard (not a very good hopper, sadly) and wouldn't you know it... off comes the chain. now i'm definitely going to hit bumps harder than this when cross season rolls around, so i've already put my derailleur back on (with the rear part of it bent a bit with pliers to avoid chain rub). as soon as i'm sure i'm happy with the front ring size, i'll invest in the nifty chain guide thing, but since i have a 44 tooth and might upgrade to the 46, i'm gonna hang onto my money for now. thanks again for the help.
drop to a 42the mekanik
Jun 19, 2001 8:23 PM
shite man only Groenendal runs a 45 and you want to run a 46? 46 is a good size for a big ring drop to a 42 is my suggestion a 42 witha 12-27 would keep you in a competive set of gears. so find 2 old 48's and grind em down and your done