Woke up this morning and thought....

nickfrog

... I only need 1 ring. I never use the big ring and only occasionnaly the small one. I run a full M950 8-speed group with 24/36/46 and 12-32.
So I am thinking of going 9-speed with a 28 ring and a 11-34 cassette.

Benefits are simplicity and saving maybe 350g.

Questions:

1 - How do I convert my M950 crank into a single ring. Is it easy to source and fit a compatible spider and ring ? Any recommendations ?

2 - Will the gaps between gears be too great ? I have done some calculations and it does not look as shockingly spaced out as I thought on paper but in the real world ?

3 - Will the chain be prone to falling off the ring ?

4 - Any issues that I have naively ignored ?

Cheers!!

stu8975

How do I convert my M950 crank into a single ring. Is it easy to source and fit a compatible spider and ring ? Any recommendations ?

Think your only option would be to remove the inner/outer ring, use shorter bolts on the middle (but you will prob have to keep the 36t ring on) as i very much doubt you will find anywhere with 112bcd rings or compatible spider for the m950 cranks. You could try retrobike.co.uk. you will also need to run a chianguide on the front, but pretty much all these fit via driveside bb cup (fit behind it), which may bring up spacing issues. The weight saving on this would be minimal.

silveringsurfer

Hmm - You 'hardly' use your smallest chainring? So are you prepared to get off and push on those occasions when it's missing? I know you are thinking of a 28 tooth front to compensate but this is going to leave you missing bigger gears. I'd be tempted to go to a 2 ring setup as a compromise and see how you get on before going the whole hog.

nickfrog

I live on the South Downs where the climbs are short, rare BUT steep and at 41, I still want an easy option equivalent to my easiest gear even at the detriment of bigger gears.

28t ring with 34t gives me 1.7m which compares well with my current set up of 1.6m (24t ring with 32t) while at the other end, 28t ring with 11 gives me 5.3m, which is not too far off my current 12t with 34t ring (5.9m).

If you guys reckon I can't find a spider then the project is a non-starter as using the 34t or going to 2-ring would not help much.

I estimate the potential weight saving as 350g (2 rings, 1shifter, 1 front mech), which is significant for me.

stu8975

Like i said you could try retrobike for compatible rings seeing as your m950 gear is circa '97..As far as saving weight goes your will only really save the weight of 2 rings..front mech/shifter is about the same weight as a chainguide (if you can find one to fit - most are for rings 32t upwards - MRP/E-Thirteen)

Northwind

2 ring might be a more practical middle ground, 28T might seem like a natural compromise but it'll cut well into your higher gears. I do 22/36 which works well but even then I sometimes run out of top end, ran 22/32 for a little while and it happened often enough to be a pain so there's no way I'd go with 28/11 as a top gear personally.

stu8975

Personally, i'd ditch the M950chainset/bb and go for an slx/xt with custom 2 ring set-up (not shimano rings though and no bashguard - eg. 22t/32t), prob looking at 200-250g saving on your current chainset/bb.

supersonic

28 I would imagine to be a bit too low a compromise.

This is where 10 speed may be of advantage to you - will close the ratios up, and allow a 36 tooth rear cog. Though you can get that with some 9 speeds too.

RealMan

Think about going double first. I'm running 26-38 on the front, and its perfect for everywhere. If I went single ring, I'd be spinning out or pushing a lot, one or the other.

Then you can probably use your mech you're using now, you won't need to buy anything except two new chainrings and some new chainring bolts.

Northwind

here Realman, what 38T chainring do you use?

RealMan

Middleburn. Did use a middleburn 26 as well, but it chainsucks like hell. Middleburn small rings are rubbish. Went and got myself a deore steel ring, and it fixed it instantly. Never had chainsuck since, on the middleburn, I had it all the time. When the middleburn 38 wears, I'll probably replace it with deore steel.


On an unrelated note, would anyone like to buy a slightly used 26T middleburn chainring..?

stu8975

Northwind wrote:

here Realman, what 38T chainring do you use?

If you are going for aftermarket..Specialite TA Chinook rings.

nickfrog

Hi guys,

Just to say thanks for all the answers and the input.

I never realised that a chain guide (the ones that go where the front mech is) would be the same weight as a front mech + shifter + cable + 2 rings. Is that really the case ? Are they 350G?

Also, the idea of 2 rings appeals a little. Are we sure that a current SLX chainset and BB ares lighter than my 97 M950 chainset + BB or is that an assumption ?

Over at retrobike they seem to think that I don't need a chain guide with a tight chain and a short cage (which I happen to have).

Cheers guys. Appreciated.

supersonic

The old M950 chainset was about 670g, and with the 210g BB puts it at roughly the same weight as a SLX triple.

I don't think you will need a chain guide.

Doombrain

i removed my 46 and never looked back. however i don't think i can do without the 24 for those tricky long grinds.

nickfrog

Doombrain wrote:

i removed my 46 and never looked back. however i don't think i can do without the 24 for those tricky long grinds.

Fair enough but what do you run at the rear ?
Even 30(F)X34(R) is not that far off my currrent 24X32 bottom gear.

bike-a-swan

I have to say, I don't really understand the appeal of a double for general use. If you're going to run a bash, fine, or if it's a good weight saving on an already light bike. But for general use I don't really see the advantage- it's a little lighter and simpler but you sacrifice some gears. You don't lose the mech, the shifters or any of the issues with front shifting. Single ringing it I get, just not double.

I'm not saying it's bad, and I thought about it myself, but that's what led me to this decision. If you were speccing from new, again, fine, it's just people saying they've changed deliberately. Seems a lot of effort to me for minimal gain.

Any thoughts?

VWsurfbum

On my hardtail i swapped out the tripple to a 34T single ring truative up front with a 11-34 XT on the rear, the only problem with that is there is a quite a big jump between some gears and forget any real steep climbs!
but i did save (a bit ) of weight and the chain doesnt fall off unless standing still or pedeling backwards :oops:

nickfrog

Guys,

I just came accross this, which seems perfect but they say it fits M952. Does anyone know if it will also fit the M950 ?

http://www.homebrewedcomponents.com/sto ... chainrings

supersonic

I can't remember what the m950 looks like tbh - have you any pics? It all depends whether the crank arm is spiderless.

Doombrain

nickfrog

SRAM PG 980. 11-32 Tooth range / alloy spider

I can get to 25mph on it, more than enough speed!

nickfrog

supersonic wrote:

I can't remember what the m950 looks like tbh - have you any pics? It all depends whether the crank arm is spiderless.

Cheers for that. I can't see any differences between M950 m951 and M952, although the later ones maybe optimised for 9-gear.

Here is a photo of the M950: http://www.mombat.org/96XTR1.jpg

Does it look spiderless to you ?

nickfrog

Doombrain wrote:

nickfrog

SRAM PG 980. 11-32 Tooth range / alloy spider

I can get to 25mph on it, more than enough speed!

Cheers. I am gonna stick all the developements on excel, current and potential and will try to make a choice. I am pretty sure it'll be 28 or 30 upfront with a 34T cassette.

I am going to give it a go I think and I'll report back.

biff55

defo give it a go nick frog as i did the same a few months back , ie , ditched the front gears and use only the middle chain ring.
one of the best mods i've done on my bike , although i appriciate everyone has different riding needs.
saves weight , saves maintenance , simple progression up and down the rear cogs without having to think about ratio's with front mech.
find life so much easier.
and if i run out of gears on a steep climb ? no big deal , pushing the thing isn't that much slower than pedalling in granny gear.
never considered 2 ring set-up , not enough gain IMO.

nickfrog

Cheers biff55. This is how it would look from a gearing point of view on paper:

biff55

forget the maths pal , its all about the smug satifaction of never having to listen to chain rub again.

nickfrog

biff55 wrote:

defo give it a go nick frog as i did the same a few months back , ie , ditched the front gears and use only the middle chain ring.
one of the best mods i've done on my bike , although i appriciate everyone has different riding needs.
saves weight , saves maintenance , simple progression up and down the rear cogs without having to think about ratio's with front mech.
find life so much easier.
and if i run out of gears on a steep climb ? no big deal , pushing the thing isn't that much slower than pedalling in granny gear.
never considered 2 ring set-up , not enough gain IMO.

Do you use a chain guide in lieu of front mech ?

biff55

not as yet , but considering it for when cranks get replaced.
but next job is replacing my existing long cage rear mech for a mid-length or short cage rear mech to reduce unwanted chain rattle and occasional jumping.

Northwind

bike-a-swan wrote:

I have to say, I don't really understand the appeal of a double for general use. If you're going to run a bash, fine, or if it's a good weight saving on an already light bike. But for general use I don't really see the advantage- it's a little lighter and simpler but you sacrifice some gears.

You lose very little, 36/11 covers all but the very highest gears- with 11/36 you lose the top 2 gears only, but the highest gear is very close to the second highest gear on 11/44. With 11/38 you lose only the very top gear. Mostly what you get rid of is overlap, it's counterintuitive but when you actually check ratios you realise how small the difference is.

You lose a bit of weight. Can't remember how much, something between 100 and 150g for me with the lighter bolts, shorter chain and no big ring. Not a huge amount. But, you also get more even chain tension because you're not having to cover such a big range, which helps shifting and chain stability. Not a huge difference this one either though, just a side benefit. Lastly you get ground clearance, and that's a nice thing to have, on more techy or steep stuff, catching a ring badly can be pretty nasty. None of this stuff makes a huge difference but then neither does losing the ring so it's a nice balance.

bike-a-swan

that was more or less my point, it has some small benefits, some small downsides. not really that much better or worse overall, yet you do get some people raving about it. I guess I can see it being something that would be worth doing on a new build or if re-drivetraining anyway, but not worth going out of the way for.

supersonic

To get an idea of 28/11, on a standard MTB, 26er, with 2 inch tyres, pedalling at 120rpm on the flat will give you 20mph. Is that fast enough for you?