Article Ten Speed Cassette Conversion for Mountain Bikes

This article on a 'retro' 10 speed MTB cassette conversion has been written by Omar R. Esteves from Caracas Venezuela.

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I am an old man who has been experimenting and tinkering with all kinds of bikes for a good part of my life, including mountain bikes in the last twenty five years or so. During all this time I have seen quite a lot of good ideas (not including terrible ones) on bikes and bike equipment fly away to obscurity only to come back some years later as the latest innovations.

For a few years, I had been reading that now when we have mountain bikes with 9-speed cassettes in all imaginable ratio combinations and from various manufacturers, some people insist that these are not suitable for mountain bikes, instead, they say that 8-speed cassettes and chains and even 7-speed cassettes (both use the same size chain) are much better for all-around mountain bikes. This proves once more that you can never satisfy everyone and everybody. Such is life and the free world some of us live in.

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During the early days of 2004 I had the sensation that sometime before 2005 I was going to end up with an obsolete 9-speed cog conversion originally created by Tom Ritchey back in 1996 for his 2X9 system based on an 8-speed 12-28T or 12-30T cassette and 8-speed chain plus a special Ritchey concave big 33 teeth cog. Since 1997, I started using this conversion but as a 3X9, that is, with three chain-rings. For many a reason, including the future shortage of replacement parts, I was convinced that for now, it was time to go to the new standard 9-speed cog cassette and the narrower chain and save my old Deore XT-II thumb-shifters until everything went back to either 7 or 8-speed cassettes and chains. As I favor thumb-shifters over trigger, dual-levers or twist-shifters, I wanted to take advantage of the Thumbies made by Paul Components Engineering and install a set of Shimano SL-BS77 9-speed indexed shifters.

After some months of wait and endless back-orders, by mid-December 2004, I got a call from Jose Gregorio Ramirez, a long time good friend, mountain bike racer and business partner at one of the local bike shops. He said he had finally received the shifters but, that there was a slight problem. The ones he received were not the SL-BS77 9-speed I had ordered but the SL-BS78 TEN SPEED! All I said was that if he had the additional parts I needed there would be nothing to worry about. A few months before, he had provided me with a set of Paul Engineering Thumbies adapters. The following day I got the rest of the components needed and went ahead with my project. Now I can say that, by a mere computer warehouse control mix-up, I put together my own ten-speed cassette conversion and I have a 30-speed indexed system working in my mountain bike. This was my 2004 Christmas gift to myself.

Many will frown and say he is not the first to do a ten speed cassette conversion for a mountain bike or he ought to be kidding, ten speed cassettes are for roadies or even those 10-speed Frankenstein jobs have never worked well in mountain bikes..

Well, it is correct, I was not and I do not pretend to be considered the first one, none-the-less, my ten speed cassette conversion for mountain bikes DOES WORK like a Swiss watch! I have been using it extensively since before Christmas of 2004 for some 11.000 kilometers or 6.875 Miles – road, dirt, weeds, high grass, mud and rain without complaint. This so far has only required top maintenance of the drive train and one chain replacement before getting to the critical stretch/wear limit.

Before going to the technical how-to, let us review some facts on the immediate past related to the creations of two experienced gentlemen who worked on this idea and made 10-speed cassettes functional for mountain bikes before me, that is, as far as my poor knowledge goes since there may be others I never heard of or read about.

Back in 1999, Tom Ritchey developed a ten speed system for his Ritchey Team mountain bike racers who were supposed to be using it during the 1999 season; probably the man himself still does. Unfortunately, Tom Ritchey never revealed how it was put together or how it worked and neither introduced this system to the mountain bike market.

I suspect Ritchey's approach was a 2x10? system controlled by a ten-speed indexed twist shifter specially made for him by Sachs as a prototype, that is, a similar piece to the one used on his "2x9" system. Maybe it was simple for Ritchey to go ahead and do it with the use of his rear Z-Hub and a prototype hub body as he did not use thedished 33T cog from his 2x9 system. He did use his OCR rear rim combined with a special ten speed cog - maybe a 12-34T 9 speed cassette plus a prototype 11Tcog/lock ring combination and a 9-speed chain.

Anything I could say would be only my own speculation. It would be anybody's guess but, if you are curious enough, you can check on a hint given in "Mountain Bike Action" magazine, July 1999 issue, in page 122 there is a picture and legend which reads "fully rigid: Tom's personal bike is a blast from the past save for the 2x9 drivetrain and SRAM composite shifters", also in page 124 of the same issue, another picture of the rear wheel and cassette of "Plexus" and the legend says "Count ‘em: Here is a look at the prototype 10 cog cluster that Ritchey is developing. The team is using it in competition this year". This was in 1999!

Several years before, there were rumors that Tom Ritchey had some of his team racers using 8-speed HÃœGI cassettes operated with 7-speed Shimano Deore XT-II thumb-shifters with the help of the extra "click" already included at the top of the right hand (rear) shifter. Well, the truth is I was also using a similar arrangement from about mid-year 1991 with an 8-speed Titanium cassette of unknown origin that my good friends at Cycle World, Miami, Fl, had ordered for me.

In 1996, after some extensive tests and racing experience and long before his 10-speed experiment plus more than a year before Shimano or anyone else produced a 9-speed system for mountain bikes, Tom Ritchey introduced to the market his 9-speed cassette conversion for his racing "2x9" system. This was achieved by using 8-speed chains and standard 8-speed cassettes mated to a 9th special 33T dished cog of his own design; the free-hub body needed for this was the standard unit that came with FH-M900, FH-M737, FH-M737-A and FH-M750 and FH-M755 hubs – this free-hub body is the one with the removable aluminum spacer that Tom Ritchey recommended you had to replace by a thinner steel spacer included with the kit. Shifting was provided by the special Ritchey designed and "Sachs" made indexed twist-shifters.

As an early convert, in 1997 I started using a "copy-cat" of this 9-speed cassette system but with three chainrings up front. I built it around eight HÃœGI aluminium cogs of 12-13-15-18-21-24-27-30T mated to a Ritchey titanium dished 33T cog "Made in Italy" for Ritchey Design and, of course, an 8-speed chain. In my version, indexed control was provided by my old set of 7-speed Deore XT-II thumb-shifters with the help of the extra click at the top end and the empty space at the bottom end of the right hand (rear) shifter. A similar set-up is now working perfectly well on Cesare Pellati's 1999 Ritchey Plexus using Shimano XT-II thumb-shifters, an "Action-Tec" 11-12-15-18-21-24-27-30T Titanium cassette mated to a concave Ritchey 33T and a Shimano Dura-Ace 8-speed chain.

Having said all this, anyone inerested can check on the "2x9" Ritchey conversion back into articles in (a) the November 1996 issue of "Mountain Bike Action" (b) the September issue of "Mountain Bike" magazine and (c) in the October issue of "Mountain Bike Action". This can also be confirmed in "IDEAS NEVER SLEEP", the early 1997 catalog from Ritchey Design Inc., and "Logic Follows Function" 1998 and 1999 Products Catalog also issued by Ritchey Design Inc. As general information, Shimano introduced its 8-speed "Dura-Ace" system for 1989 but, did not introduce to the market more than 8-speed cassettes for the XTR or XT mountain bike series until 1998.

A few years ago and long before I accidentally came about my ten speed cassette conversion, Paul Price of Paul Components Engineering, after introducing his "Thumbies" to the market, had been experimenting for some time with the idea of a 30 speed mountain bike. As there were no 10-speed cassettes for mountain bikes, he used a standard Shimano Dura-Ace 12-27T 10-speed cassette on his "Kelly" framed test-bed mountain bike; index shifting was provided by a set of Shimano Dura-Ace SL-BS78 shifters on his own "Thumbies".

I knew of the Ritchey 10-speed cassette as I had read about it during mid-1999 but, I was never aware of Paul's experience until the weekend of 26-27th June 2005, some seven months after I did my own, when I was glancing through Paul's Components Engineering web page and saw he was offering for sale his "Kelly" test-bed bike. Nevertheless, as any one would agree, a 27T cog as the maximum bail-out gear in a mountain bike is for hard core racers but not enough for non-racing mere mortals like the majority of us. I believe Paul Price would also agree.

I hope every one may be satisfied now on who were the first and if someone wants to add something or someone else, please, be my guest.


A few words and sincere advise. If you are a true believer or swear by either 8-speed or 9-speed drive systems and would like to install indexed "thumb-shifters" with the optional friction mode in the right hand/rear shifter for the "just-in-case" but you are unable to find the original Shimano Deote XT-II shifters, go ahead and order a set of the Paul "Thumbies" to install either the Shimano SL-BS50-8(Dura-Ace), SL-BS64-8(Ultegra) both are designed to work with 7 and 8-speed cassettes & chains or the Shimano SL-BS77(Dura-Ace/Ultegra) designed for 9-speed cassettes & chains. This way you will not have to bother with all the troubles and work the ten speed conversion represents. No harm done.
Required Parts & Components ¦ All What You need for your 10-speed cassette conversion

a) Rear Derailleur: any long-cage or mid-cage rear derailleur, compatible with Shimano indexing and capable of handling 8 or 9 speeds and a maximum of 34T big size cog. Any short cage rear derailleur works correctly only up to a maximum of 28T.

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b) Front Derailleur: The best derailleur designs for use with this conversion are the "band type". For old style cranks with 110/74 five-arm bolts circles use band type long cage mountain derailleur suitable for 3x8 (24 speeds) or 3x9 (27 speeds) speeds set-up, similar in size to a Shimano XTR FD-M900 or FD-M901 (band type). If using "compact" style cranks, either 94/58 & 94/56 five-arm or 149/102/64 & 104/64 four-arm designs, go with a band type derailleur designed to work with compact chain-rings such as Shimano FD-M961, FD-M806, FD-M761 or similar design from other makers. Older (and longer) designs made to work with the bigger 110/94 bolt circle chain-rings tend to rub or may find interference with the right hand chain-stay when used with the compact design cranks. IMPORTANT: Any derailleur of the Shimano FD-M960, FD-M760 or similar design from other manufacturers which attaches to the frame via the bottom-bracket right hand side spindle cup (BB Mount) may create chain-line problems.

c) One pair or set of Paul Component Engineering "Thumbies", either 7/8'' size for mountain bike bars or 26mm size for road size drop-bars. All necessary stainless steel hardware is included.

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d) One set of Shimano SL-BS78 bar-end shifters to be mounted on the "Thumbies"; you will need the cables & cable housing provided with the set. Remove the original barrel type bar-end mounts from the shifters as you will not be using these mounts.

e) A free hub body capable of accepting any 9 speed or 10-speed cassette is mandatory. The use of a XTR FH-M900 free-hub body with the removable aluminum spacer is recommended (I use an old model Shimano XTR FH-M900 complete hub). IMPORTANT NOTE: Please remember that this same free-hub body with the removable aluminum spacer was also used with the Shimano XT rear free-hubs models FH-M737, FH-M737A and FH-M750 from the year 1994 through the year 2000, inclusive.

f) A 10 speed Chain.

g) One 11-34T SRAM PG-970 9-speed cassette or any similar cassette made by other maker which can be taken apart in order to change the original 2,56mm spacers for thinner 2.25mm spacers, plus a separate 27T and a 30T of any compatible make and a Ritchey 33T concave cog from a 2x9 set. It all depends on what you want to do please check different options under item 4) below.

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h) It is always advisable to use a rear "OCR" (Off Center holes Rim), nevertheless, this is not absolutely necessary but helps a lot with alignment, makes a stronger wheel and gives some more separation between the big cog and the spokes.


First of all, in theory all the Shimano free-hub bodies that take a 9 or 10 speeds cassette as well as some 8 speeds free-hubs of the upper level have the same "depth" or body length. Therefore an XT or XTR free-hub body designed for 8 or 9 speeds and similar bodies will also take the 10 speed cassette. Why? Very simple:

1) A 9-speed Cassette has a total "width" of 36.5mm and a 10-speed cassette has a total of 37.5mm. The 1.0mm difference between the two does not really affect the new setup plus the fact that the long or "deep" thread lock-ring provided with 9-speed cassettes is perfectly capable of taking care of this additional 1.0mm.

2) In a 9-speed cassette, the spacers between the cogs are 2.56mm and the cogs are 1.76mm thick, while in the 10 speed cassette the spacers are 2.35mm and the cogs are 1.60mm, or so Shimano states. It is important to note that the spacers on the first two or smallest cog units (11T & 12T) in both 9 and 10 speeds cassettes were found to be almost the same or closely similar to each other and both are fully compatible with indexing of the SL-BS78 shifters, therefore no need to change anything here for these first two or smallest cogs.

3) After taking out the retaining bolt in the SRAM PG-970 cassette, or if you use other maker's which come as individual or separate cogs, you will have to use 2.25mm spacers to separate the eight bigger cogs. These 2.25mm spacers can be made from any standard 3.0mm aluminium spacer or better still from the plastic 2.56mm spacers that come with the SRAM PG-970. It is important to remember that too thin spacers place cogs extremely close to each other which may hinder the shifting from any smaller cog to the next bigger cog, therefore, NEVER GO too much below 2.25mm. Remember, differences in thickness here may be less than a hair thick.

4) The choices are few but, with a dose of patience, the set-ups given below can be achieved fairly easy, that is:

1. If you are going to use the original SRAM PG-970 with the nine 11-34T cogs (11-12-14-16-18-21-24-28-34T) plus any compatible 30T cog from other manufacturer (Action-Tec, HUGI etc..) and the proper spacers (seven spacers of 2.25mm), you will have a combination of 11-12-14-16-18-21-24-28-30-34T, but you must use either a Shimano XTR M900 free-hub body or any of the XT M737, M737-A or M750 free-hub body and REMOVE the aluminum spacer that comes with it in order to make some extra room on the body for the 30T cog and the 7th spacer of 2.25 mm. If you use a compatible 27T cog instead of the SRAM 28T, you will be able to improve the closer ratios and have a combination of 11-12-14-16-18-21-24-27-30-34T but, you still have to remove the aluminum spacer from the free-hub body. In this case the use of a rear OCR rim is recommended.

2. If you decide to work with the concave (dished) 33T from a Ritchey 2x9 Drive-train and you have been able to find one, you can use any 9 speed free-hub body. There is no need to insert a spacer between the concave (dished) Ritchey 33T cog and the next 30Tcog. This way you will also have similar combinations as the groups in item i) above, but your maximum (biggest) cog will be the 33T which many consider an advantage.

VERY IMPORTANT: It is also necessary to take into account that if you use cog sets which are "straight-cut" (no ramps) or any other cog sets without a specific design or ramps to help the chain go up from any cog to the next bigger cog, you may have to OVER-SHIFT a bit with the right hand thumb-shifter in order to help the chain engage the next bigger cog.

by: Omar R. Esteves M. Caracas - Venezuela (Reviewed September 22, 2007)


No mention of use of the Shimano SL-R770 10 speed Rapidfire shifters. I understnad that these work really well too on 10speed MTB applications.

Omar R. Esteves M.

Here are my considerations for not mentioning the Shimano SL-R770 10spd Rapid Fire:

1) Firstly, in the last part of third paragraph of the article I clearly stated that "I favor 'thumb-shifters' over trigger, dual levers or twist-shifters...". Rapid Fire shifters are one of many versions of trigger or dual lever shifters. On the other hand, when I came out with my 10speed cassette conversion on December 2004, the SL-R770 10spd Rapid Fire was non-existent. As a matter of fact they were not available until early 2007.

There are other considerations that must be mentioned:

1) The SL-R770 were developed by Shimano as a "flat bar" group to work with "road components", this is evidenced by the 'R' in front of the 770 in its model number. Rapid Fire shifters are not as dependable as the system in the SL-BS78 which has, basically, the same full-proof but reduced in size internal mechanism as in the old XTII Thumb Shifters; this mecanism incorporates the "friction" mode in case of accidental bending or misalignment of the derailleur hanger or because any other damage of the micro-adjustment of the indexing mode. These options of indexed and friction modes are non-existent in any other model of Shimano twist, dual, trigger or rapid-fire shifters.

2) SL-R770 Rapid Fire model as any of the new 'rapid fire' sets can not shift more than two cogs or gears at a time. With indexed thumb shifters including SL-BS78 you can go up or down two, three, four etc.. or from top to bottom or viceversa with one move, that is, the whole rear shifting spectrum in one go.

3) SL-R770 Rapid Fire (front) shifters will only work well and must be used with FD-R770 front derailleur for double chainrings or FD-R773 (2B, 2F, OB or OF) front derailleurs which are compatible to work with triple cahinrings from a maximum of 50T to down to a minimum of 30T chainring but can not handle the difference in triple chainrings from a 48T down to 20T in the same crank as do long cage front derailleurs like the FD-M900 or FD-M901 made for use with the old type 110/74 triple cranks or the FD-M961, FD-M806 or FD-M761 made for compact triple type cranks. Furthermore, SL-R770 (rear) shifters are designed to work well with RD-7800, RD-6600 or RD-5600 both GS and SS road type rear derailleur which are all "short cage" and limited to handle a maximum rear sproket size of 27T only.

4) SL-R770 Rapid Fire shifters will not allow room for the necessary "overshift" to go to the next bigger cog when one uses straight-cut cog teeth.

Andy P

this is a great idea, but you have made it over complicated. You don't need to do modify a new cassette. All you have to do is buy a IRD 11-34 10 speed cassette. it uses a shimano 8/9 speed spline. playing around w/ the spacers just seems like a headache.


For a simpler 10speed Shimano atb conversion check out the IRD cassette.

Omar R. Esteves

It would have been oversimplified IF, for 2004, 2005 and 2006 IRD had had their 10-sp. MTB cassettes in 11-34T, 11-32T or 12-32T BUT, these were not available until late 2007. If you go back and read what the article, I did this conversion back in December 2004. OVERCOMPLICATED? I doubt it, since there were no special separate 10-sp spacers in the market. On the other hand IRD does not make the close ratio cassette I have.


I've had some experience with the 10 speed IRD cassette mentioned in "Eric's" post and while it is a relatively wide ranging cassette vs. that of a garden variety Shimano,SRAM or Campy road cassette, it's pretty heavy (302g) and it only goes from 12-28 but the new SRAM XX has an 11-36 range that is only 208g! It seems a nice (albeit expensive) alternative to the IRD.

My general experience with the IRD cassette is that it suffers from a lot of drive train noise even with a good quality Dura Ace chain. Given the relative spacing and thicknesses of the cogs of the IRD cassette vs a Shimano the plates of the chain would constantly rub against the cogs (even with a properly adjusted and aligned derailleur).

I'm a bit more optimistic about the SRAM cassette even though they are generally a bit more noisy than a Shimano cassette but not nearly as clangorous as the IRD offering.

Paul is now making a mounting system for the SRAM TT 500 shifter and that could be a cool set up and offers a intriguing possibilities for a 1x10 or 2x10 mtb set up.

Personally, I may make the leap to a 1x9 set up if and when Shimano comes out with their 11-36 cassette in 2010.

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