What is the maximum tooth sprocket you could fit on the back using a Deore DX rear derailleur?

[retrobiker273891]

The rear mech? No clue, it was just what I had in the parts box that looked to have a decent cage length. I didnt buy it deliberately for the job. I suppose it'll be the long cage version that the web describes as 85mm.

Good to know, just grab n go! No complex mathematics behind the decision.

Looks like some relevant discussion here, particularly a chap down the page, linking to a video, saying he ran 45 on a bike from 2012. Ok not that old but somewhat. https://www.mtbr.com/threads/deore-m4100-10-speed-11-46-compatability.1174701/

 

[hamster]

So never upgrade a bike. Stick with single speed and 'mash' up all hills. .

I tried out singlespeed 15 years ago. The first month was horrible, but I got fitter and stronger really rapidly. Interestingly my descending and cornering also improved as I sought to conserve speed.

It's still my go-to bike for riding off road. Throwing away all that gear lark saves a 2-3kgs or so, and you end up with a crazy light and nimble bike.

 

[retrobiker273891]

Back on topic, I did try a Microshift 9 speed cassette with a wide range which worked fine with a hanger extender and LX M570 rear mech, but found myself not using anything other than the first 3 cogs, so I've ditched it and gone back to a normal cassette.

Hi, revisiting this thread now I have my new bike.

I found out today the RD on it is XT RD-M771. Is that of similar spec to yours? I wasn't able to find the datasheet for your one but for mine it says 45t/33t for SGS/GS and max of 34t for both. I think mine is the GS version as it doesn't look as extended as the SGS from the images but I read somewhere recently than if it is a 3x mountain bike then it necessarily will be SGS. Is that right?

 

[retrobiker273891]

Reality is 34T, that's what we punched them too BiTD, and there where larger (just).

Drop the front to a 24T, and if you get it cheap then middle to a 36T and you have a good range.
8 or 9speed at the back at a later date with 11/32T 11/34T

The dinner plate cogs are for tooth counts around 30T at the front and one or two ring at the front (2 rings if you also want the higher speed and like to pedal at that speed.)

I have been riding on my new 20/28 front/back and could still do with some more. Not because I need it. 18" is great for most but a few lower will be better for serious hills. I am not talking about everyday stuff, which 18 covers but the long monsters.

Also though I feel bigger in the back would really be nice to give more options on the middle ring, or outer, since I think I will be going 2x.

 

[manac]

I have a 1995 Trek 950 that came with 22/32/42, 11-28 8 sp LX derailleur.
Put an 11-40 and it works well. Can’t cross chain down low even from the middle chainring. Lowest two gears only work on the 22 chainring but it’s not a problem.
I’ve ordered a derailleur hanger extension to see if it helps.
I have read you can take that 11-40 8 speed and make it a wide 7 speed if needed.
I have a Killer V with a seven speed XT setup I may try it on.

 

[retrobiker273891]

I have a 1995 Trek 950 that came with 22/32/42, 11-28 8 sp LX derailleur.
Put an 11-40 and it works well. Can’t cross chain down low even from the middle chainring. Lowest two gears only work on the 22 chainring but it’s not a problem.
I’ve ordered a derailleur hanger extension to see if it helps.
I have read you can take that 11-40 8 speed and make it a wide 7 speed if needed.
I have a Killer V with a seven speed XT setup I may try it on.

Thanks for the information.

Sounds like your original setup is the same as how mine is right now however I have 20 up front. The change from 38 (on my previous bike) to 32 on the middle is really nice for gentle climbing.

As I re-evaluated I have come to the thought that going too big on the rear would be wasting my 20t granny since it would mean I would spend more time in the middle ring. I do want a bit more on the middle but not so much to overshadow the granny. I am settling on 36t cassette now which will give me a couple more gears for both the granny and the middle ring but I feel will be an even balance between the two then.

Currently I feel I could do with a couple more for the middle for medium climbs and a couple more on the granny for serious climbs and 36 I think will cover both bases.

28 is my maximum right now and this will give me two more low gears on the back with 32 and 36 additions.

I think my derailleur should just about be able to handle that without modification as I looked up the tech sheet and it says 34 max while people say the shimano ratings are conservative so 2 more should be fine according to other reports.

 

[retrobiker273891]

I have a 1995 Trek 950 that came with 22/32/42, 11-28 8 sp LX derailleur.
Put an 11-40 and it works well. Can’t cross chain down low even from the middle chainring. Lowest two gears only work on the 22 chainring but it’s not a problem.
I’ve ordered a derailleur hanger extension to see if it helps.
I have read you can take that 11-40 8 speed and make it a wide 7 speed if needed.
I have a Killer V with a seven speed XT setup I may try it on.

Btw does that low gearing get used much? I calculate it at 14 gear inches. People say that lower than 18 is a waste and you won't be able to stay upright but I have seen threads online where people go way lower and say it gets good use. I read one person as low as 13 and said they were using it happily.

I was out again today and can say 18 deals with most things but at soon as it is a long climb or super steep beyond the norm then lower would be much appreciated!

It is not that I am unfit, I would say fairly, but I want to be comfortable with any hill. Not that I have to use the lowest all the time but I want it there for exceptional climbs whereas most people who talk down on super low gears seem to only be accounting for normal stuff, not the exceptional.

Today I was on a really tiny single track and it was in bad disrepair. Lots of the hedge overgrown into the rand moss up the middle. It was so overgrown I had to ride in the middle for a while and it was about a mile of climbing. Not super steep but the length and the moss did take it out of me.

Oh yea and I tackled this super super steep hill which I used to 'test' the gearing the other day. I was fresh that day and got up it but it was super hard. I thought I would try it again today after having ridden a couple of hours, with less in the tank, and it was way harder. I thought I would have to bail out and push at one point but I just managed to stay on to the top at a crawl.

Lower gears are also good in this case when you are running near empty to keep you going.

 

[manac]

Rode the bike yesterday. Can’t use the lowest two gears with the 32 and 42 chainrings. Don’t really need to though, see the chart.
Running 700x41’s

I normally don’t need the 14 and 18 gear inch but any ride from my house has a mile of 20% grade to get home.

 

[retrobiker273891]

Rode the bike yesterday. Can’t use the lowest two gears with the 32 and 42 chainrings. Don’t really need to though, see the chart.
Running 700x41’s
View attachment 884682
I normally don’t need the 14 and 18 gear inch but any ride from my house has a mile of 20% grade to get home.

You have cropped the left side so I can't see what the other axis is but I can I guess infer it is largest, 40, on the first left and going higher (gearwise) thereafter.

Indeed, I certainly wouldn't expect to use 14 all the time but it is there for when it is needed. Either extreme ascent or just 'bonked' and want to keep going. You don't have issues 'falling over sideways' in 14 as many detractors will tell you?

My gearing will be almost identical at the low end at 20/36. Ordered so should be here in the next few days.

As for me, I also want to use the middle ring to give some more mid range low gearing as I feel I could do with some more there currently at 28 max. The new cassette will offer 32 and 36 so thinking that will be a valuable addition for both middle and granny.

There was someone on other cycling forum shaming me for wanting even 18 showing off how he has 30 as his lowest and that he has more energy than people with lower gears he rides with.

I am going to take off the outer ring to make 2x since I didn't use it anyway and just coast when going downhill so never seen the point in it.

 

[retrobiker273891]

I got my 36t and put it on yesterday and a bit disappointed it doesn't clear the 36t cog cleanly! I thought it would be easy enough going by what people say about shimano being conservative in their maximum low cog specifications and 34t being listed as that and 36t being only 2 above.

It clears it but it is so close that the top jockey wheel and the sprocket seem to be intermeshed, although not touching. Rides fine for the little I did yesterday but if I spin the crank backwards I notice the derailleur would rattle a bit and shake slightly from side to side. I guess that is not good and likely would give more wear on the parts?

I screwed the b-screw, I presume that is what it is that people refer to, all the way I could and that stopped the rattling when on the 32t chainring but then when I change to 20t granny the rattle came back.

Maybe I will try the screwing the b-screw in the other side to get a little bit more out of it, that I have read. It is frustrating if I have to buy a hanger extender after all as I thought the 36 would be ok but if I have to then I will.

If I twist the derailleur by hand there is still plenty of spring and movement in it to give lots more clearance it is just the screw is set to maximum so not sure how I would make use of that. It seems like a longer screw, or other means to jam the gap, would do it. I doubt the existing reverse b-screw will extend it to its full potential.

Anyone know what kind of screw that would be that I could buy from a common DIY store so I can get longer? Or other way to plug that gap to give the derailleur more clearance?