custermustache

I have a mountain bike with Shimano Deore DX group, and I have it set up as an around town bike. I am normally a skinny tire road bike guy, and would rather have a more teeth up front than mountain cranks allow - is it possible for my derailleurs to handle the larger gearing without any trouble? The bike feels slow, and I understand it will be a little slower due to wheel size, etc, but I think with more road type gearing it would make me happier.

Also, where does Deore DX land in the Deore line? I know they don't make it anymore, but I'd like to know a little mroe about it, if at all possible.

scozim 

If the derailleur in the rear is a long cage I wouldn't see why not. What's the crankset? Can you go with larger rings up front? My Trek is set up with a 42-36-26 right now but I've got a 48 tooth chainring if I wanted larger gears for commuting.

mkeller234

Yes you can. I had a 1990 Trek 1420 "sport touring" bike that came with Deore DX on it. The bike had a typical road type triple on it and it worked very, very well.

I believe the lineup up to 1992 was:
- Deore XT
- Deore DX
- Deore LX

XTR was introduced in 1992 I think (can anyone confirm that?) DX was dropped the same year. It's great stuff, I never once had a problem with it.

Here is the Trek:

dashuaigeh

Heya custer - I think you should be fine. Most rear derailleurs have a "max capacity", which is the (biggest chainring - smallest chainring) + (biggest sprocket - smallest sprocket). Check chain length to make sure it's long enough for new front chainrings? As for front, just make sure the jump from one chainring to the next is within it's capacity.

As for DX - Sheldon Brown to the rescue. Appears to have become LX. https://www.sheldonbrown.com/shimano.html

degan

I have a set of DX 7/8 speed hubs I'm getting ready to build up into touring wheels. They seem like a short run, but higher end, line within Deore. The hubs, anyway.

custermustache

I currently have a 42 up front, but I would like to go a little higher - do I need to change all 3 rings, or can I just switch out the big ring?

Currently it has a Shimano Hyperdrive - c crankset. I'm not opposed to just switching out rings if I don't have to buy a new crankset.

mkeller234

The Deore DX equipment on my Trek was mixed with Shimano 105, so I assumed the two groups were roughly equal. Maybe the Deore DX was slightly nicer than 105 and the hubs on my Trek were a cheap-out component, the crank was nothing fancy.

nikkorod

There was no real difference between the XT, DX and LX. Many high end mountain bikes were speced with any of the three or a mix. I had a DX group on a 1990 Diamondback Apex. Worked flawlessly. I have LX and DX on my Trek 950 and they all work perfectly. The late 80's early 90's XT, DX,and LX components are some of the best stuff Shimano ever made. IMO

dashuaigeh

I think you should be able to just switch out the rings (plus a diff crankset may change up your chainline). What's your next largest front chainring? If it's not too big of a jump from the middle ring to your new ring, it should be fine. Front derailleurs have a max tooth difference rating - for example, on a lot of modern derailleurs it's around 16 teeth to handle something like a 50/34 compact gearing.

custermustache

How would I figure out what my front derailluer range is?

I actually have a Biopace ring that I may put on it.

surreal

ok, the RD is not a consideration in this case, as the change will be in the cranks, and the FD will limit the choices for front rings before a difference big enough to impact the overall chainwrap could even begin to challenge the RD.

In the olden days, many mtb front derailers were designed around the 48/36/26 or 48/38/28 cranks, so the max ring for that ol' DX front derailer may well be >48, and most likely a 50 will work nicely. My suggestion would be to jump all the rings up. Depending on the BCD of your hyperdrive-c (with a 42t big ring, i'm thinking it is either an early 4-arm/104mm, or a compact 94mm 5 arm), finding bigger rings will be easy, but i've not seen larger than a 48t for 4 arm systems, and finding anything at all beyond standard compact mtb rings in 94mm 5-bolt will be a chore. If you got a 104mm 4 arm, getting the modern shimano "Trekking" rings in a 48/36/26 should be no problem. If it's a 94mm 5-bolt, i'd just buy a sugino xd or similar and make life easier.

In any case, changing just the outer ring will likely not be a viable option, b/c while a 48 to 32 tooth drop might be finagled enough to work, it'll make for some sloppy shifts and a massive gap in the front gearing in the best case.
-rob

surreal

mkeller, is that a DX front derailer on that there trek? Or, a 105?

-rob

dashuaigeh

Would you happen to have a parts number for the FD? You may be able to look it up, but I'm willing to be the capacity is 22 (most triples seem to be - there's usually a 22 tooth difference b/w the granny and large gear). Surreal is right - the only difference for a road and mtb triple is the amount that cable pull moves the FD, and the cage size, which determines capacity. I was slightly wrong (sorry, didn't think clearly about triples), you do have to make sure the tooth count difference from your big ring to your smallest/granny ring is within the capacity.

I happen to really enjoy Biopace - I took it off of my tourer b/c I thought it looked funny, and now I might end up putting it back on another ride .

mkeller234

Its a DX front derailleur. It managed the jump up from that tiny granny ring with no problems. I think the small ring had only 30 teeth or so.

surreal

mkeller: If you have a 52 big ring and a 30t small ring, that is pretty standard for road triples, and not much of a jump at all. Well, it's a 22t jump, and pretty big, but it's kind of the "standard" triple-FD jump. A bigger consideration for the OP and folks in his situation is the step-between to the middle ring, especially if his front shifter is indexed. Most of these things go in a big ring minus 12 minus 10, but there's some wiggle room there. But, a big ring minus 18 minus four would shift terribly, if at all (in most cases). At any rate, it's great news for mkeller (and the rest of us with a curiosity about such things) that the DX FD can handle a full-size road triple.

Dash- You're right about the 22t capacity, and also the generalization about the road and mountain FDs having slightly different pull ratios. (This is more of a difference among the modern stuff, where the chainline of the mtb crank is further outboard, and the indexing is markedly different between many road and mtb front shifting.) Another consideration, however, is the max ring; due to the angles of the cages, many modern FDs are actually rated for a maximum size chainring. For instance, modern XT FDs come in several flavors (high-clamp, low-clamp, e-type), but also in different versions: a "trekking" version with a 48t max-ring rating, and the typical mtb version, with a 44t max-cog. It is difficult to use the latter with a 48t big ring without some rubbing. My suspicion is that the DX and its contemporary FDs are going to be able to handle 48t+ because the 48t top ring was common on mtbs for many years just prior to that.

The numbers are fd-m650 or fd-m651; the 651 is the low-clamp/top-swing version. If yours is a fd-m650 like mkeller's, we already know it'll handle a 52/42/30; velobase lists the capacity as a 26t, so you might be able to go with only changing the outer ring. (I can't recommend it, though)

-rob

custermustache

1. My crankset has 5 arms
2. I run the whole thing in friction mode
3. Could I just move all of my rings down, so to speak - move my two outer rings in and put my larger ring on the outside? Does that make sense?

Thanks for all of the help.

Suburban Grind

custermustache:

To question 3, you can't because the smaller chain ring mounts on a smaller bolt circle diameter (BCD) on the cranks spider than the two big ones. The mounting holes on the bigger chain rings and the bosses on the back of the crank spider are a mis-match. It has nothing to do with how the derailleurs are operated and little to do with how many arms your crankset has.

dashuaigeh

Yeah, SuburbanGrind is right, the outer one won't go into the granny. I actually have access to a few extra Biopace chainrings from the co-op that I can send over for shipping if you want, just lemme know the desired tooth counts (I'll let you know if they don't have them) and BCD on your crankset (it should be 110 if it is an old Deore triple)

surreal

it's a hyperdrive c, with a 42t big ring, which means the spider of a 110 would be too small to support a 32t ring, so i'm guessing it is a 94mm bcd

-rob

custermustache

Forgive my ignorance, but what is BCD?

After I learn that, I will take you up on the chainring offer.

dashuaigeh

BCD is bolt circle diameter - a measurement of the spacing of the crank bolt holes on a crankset. Here's a definition - https://www.sheldonbrown.com/gloss_bo-z.html.

Sorry, I didn't read before that you were using Hyperdrive C cranks - if they're 94 BCD, they won't fit the set of chainrings I've got :\.

custermustache

I could just throw a road triple crankset on there, couldn't I? I forgot that I have one.

surreal

yes, you can totally do that, with the appropriate BB

-rb