Woke up this morning and thought....

[nickfrog]

Have you had a mess about with sheldons gear calculator?

I've had a serious mess about with it !!!!

 

[nickfrog]

There is also the issue of chain alignment. If you just have the centre chainring of a triple chainset at the front, the chain has to curve a lot to reach the inner and outer-most sprockets of the rear cassette, which places extra stress and wear on the chain when used like this.

In general a triple chainset set-up, whether it's 18,21,24 or 27 speed, is designed so that the inner chainring is used with the inner most sprockets of the cassette, the middle chainring with the centre cassette sprockets and the outer chainring with the outer cassette sprockets. This diagram and comparison with a 14speed hub gear sort of explains it: http://www.rohloff.de/en/products/speedhub/gear_range_comparison/index.html

Fair comment and I would have to place the single ring where the middle ring currently is (ie exactly in the "middle" of the cassette) to minomise stress/wear/friction.

 

[Dr S]

Forge Racing made some nice single's to fit Shimano cranks from that era. Look on eBay. I use a 32t up front and a 32/12 9 speed cassette on my modern and we have some really big hills up in Northumberland. Unless you are riding really bumpy stuff you shouldn't need a device to hold the chain on the ring, just get your chainline as straight as you can and keep the chain short. A short cage mech helps too.

 

[Rob853]

I went for the Middleburn spider on 952 SS. Works really well but pricey.

 

[nickfrog]

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

I am so excited, I feel like I am 12 again.

 

[FluffyChicken]

28tooth chainring may be your problem though.

Do you have 5 arm spider or the everything bolts to the top ring setup currently?

A 5 arm spider (110BCD) would limit you to 34T in the middle ring as your smallest, while you could fit a 28tooth to the inner ring position, it's not ideal as you cannot push you chainline out easily with your bottom bracket.

If you fit a middleburn 4 arm spider on (about £40 I think) I think 32 becomes the smallest middle ring you can fit.

If it's XTR outer ring, then well just getting hold of a ring may be a problem and you'll still have a top ring and probably still not small enough.

If you start moving buying spiders and ring possibly bottom bracket if using inner ring, it may just be cheaper, less of a compromise to get a new single speed specific setup..


Though that HBC link does have the probably cheapest answer. Not seen that before

 

[nickfrog]

Cheers Fluffy. The cranks are spider less so HBC are my only resort for the moment for a 28. I'd better buy several in case they stop making them!!
I still need to check compatibility with M950 as the site only list M952. They look very similar if not identical.

If anyone had a definite answer on that ? HBC don't have a contact link...

 

[nickfrog]

Guys,

I am now looking at an 10 speed cassette to minimise gear compromise as they do a 11-36. Does anyone know if my M950 rear mech will cope with that case both in terms of capacity and in terms of chain width?

Also, will the custom ring be likely to cope with the super super narrow 10-speed chain ?

Thanks.

Confused of Sussex

 

[nickfrog]

UPDATED. Finally done it. 29t x 11-34 9-speed. No chain retention device at all. No chain drop though despite aggressive XC use.

 

[kaiser]

Is that a homebrewed chainwheel?