Isis vs MegaExo
- Thread starter Walrus
- Start date
Walrus said:
Theoretically, the outboard bearings, which are larger, should last longer than the smaller bearings in the ISIS bb. Are there any other advantages? Don't know, except the manufacturers can sell more stuff, now that there is something "new and improved" = greater profits for them!
Seriously, though, a friend of mine who has been riding FSA megaexo's for the past 5 months or so said he hasn't noticed any significant differences from his previous bb (Dura Ace Octalink).
Before I install the ceramic BB I spun it and noticed no difference between my regular Token Strontium BB. And I didn't notice anything less frictionless during my ride. Maybe ceramic is just hype or maybe these BB are less friction under pressure. Yeah, I paid $150 big bucks on ebay for mine. At least it's light weight.
I'm really hoping to get an ergomo pro for my bikes but I gotta make more money. It's really expensive at $1600 a setup.
I'm really hoping to get an ergomo pro for my bikes but I gotta make more money. It's really expensive at $1600 a setup.
ISIS or 'International Splined Interface Standard' actually refers to the interface or area where crank/arms meet spindle. Other spindel interface standards are Octalink (shimano proprietary), square taper.Walrus said:
MegaExo is FSA's copy of Shimano's integrated BB on their Hollowtech cranks - whereby the BB spindle is pressed into the crank spider (therefore already integrated with the crank and its not a separate unit). In both systems (FSA & SHimano) the sealed bearings are larger in diameter and are mounted outside the BB shell. Normally in other standards (ISIS, Octalink, square and alike) the bearings sit inwards and within the BB shell. So between the 2 systems (1st system being FSAs megaexo and shimanos integrated BB; 2nd system being Octalink, Isis and square - I am classifying them according to their appllication of bearings) in theory the 1st system is stiffer, and friendlier to the bearings because the bearings sit farther apart (and nearer to the area where crank meets spindle) thereby reducing the force exerted on the bearings when one stomps on the cranks/pedals.
FSA's Megaexo is a copy of Shimano's but is said to be an improved version with the use of ceramic bearings and has in fact received the 'Fiets Rai 2006 Innovation Award' in a cycle show in the Netherlands. You can read more about the innovation at http://www.cyclingnews.com/tech/2005/shows/interbike05/?id=results/interbike0513
Outboard bearings have a few advantages, and a few disadvantages. One such plus is the longer wear life of the bearings. One - is the higher Q-Factor. ISIS can be great, but if you search around there are a few isis problems. A well designed isis can be much better than a badly designed outboard. This is just like a good aluminium bike can be better than a carbon one. It is all about marketing. Oh, and outboard systems limit your crank choice to only a couple, whereas there are a huge selection of isis.
I think there is still a bit of confusion here so let me just clarify....bobbyOCR said:
Megaexo system is similar to shimanos integrated BB and the 1 feature that distinguishes such system is the OUTBOARD BEARINGS. Outboard bearings are not interfaces. It so happens that ISIS, square and Octalinks have bearings inboard but that is not their design feature. The design features that distinguishes these are their interfaces.
The point of comparison and therefore to put the question into perspective is - Is an outboard bearing system (FSAs Megaexo or Shimano's Inegrated BB) better than other systems than use inboard bearings.
To sum up, the interface does not have anything to do with the durability of the bearings.
Splines and/or interfaces are an entirely different issue. Which one is better is entirely a matter of one's preference and experience. As is the case, manufacturers always claim theirs is the best. Then again 'best' can refer to a lot of things - is it best in terms of durability, stiffness, reliability etc.bobbyOCR said:
In the past the most universally available spline was the square taper. Then shimano came out with the Octalink which it claimed to be more durable than the square, etc, etc. However it was licensed and proprietary and that is why the ISIS came to be. Again those who advocate ISIS claim it to be better than the Octalink which is better than the square blah blah blah. Better in terms of what is still questionable to me. I suspect that it was better in terms of compatibility because a lot of manufacturers embraced this standard.
Now in terms of durability - that I think depends on the manufacturer and not dependent on the design. For example, one can make an ISIS spline using inferior mettalurgy versus chromoly steel square taper spindle that's been obsessively over-engineered and vice versa.
IMO, the bad rap one system has gotten in the past (I wont mention which but I think you know) is not because of the interface design that's been adapted but rather with the material used and manufacturing process coupled with the misuse, re: incompatible components. That is why it is always wise to use the spindle/BB that comes with a particular crankset or the one recommended by the brand.
SKF Germany are supposed to make the best ISIS bottom bracket but are hell expensive , as a bearing company first , they seem to have sorted out the bearing durability issues of the Taiwanese units.
As long as it works, fits, doesn't self destruct easily, I don't care where the bearings sit or how my crankarms attach to my bike. I have outboard on mine and have noticed an increase in the Q factor, and in fact it is about the same (due to the redesign of the crank arms). So it really depends on if you want the ability to choose from different crank designs or not. Just my two cents, not meaning to step on anyone's toes.
1. I've seen in various posts stating that outboard bearing crank sets have more friction than other bottom bracket configurations due to the loading of the bearings. It's my understanding that Campy has addressed this issue with their new release.
2. WRT ceramic bearings, it's my understanding that a (relatively) inexpensive set of ceramic bearings are no better than a good set of steel bearings. IIRC, Zipp mentions that the ceramic bearings they use add nearly $1k to the cost of their top of the line wheel sets.
2. WRT ceramic bearings, it's my understanding that a (relatively) inexpensive set of ceramic bearings are no better than a good set of steel bearings. IIRC, Zipp mentions that the ceramic bearings they use add nearly $1k to the cost of their top of the line wheel sets.
What value.
I presume you currently have an ISIS crank ... and, that you want to dabble in the world of "external bearing" Bottom Brackets ...Walrus said:
If that's what's on your mind, FSA has an ISIS BB with outboard bearings (see attachment) ... the price varies depending on where you buy it from (LBS, mail order, eBay, wherever).
The wider bearing separation of a MegaExo (or, equivalent) BB theoretically creates a pseudo-wider BB shell which supposedly means there is less "flexing" & greater power transfer ...
I've read that the BB shell needs to have been faced to ensure the bearings & BB spindle don't bind -- that makes sense to me. Cartridge bottom brackets which have been prevalent over the past decade-or-so obviously are self-contained and have not required the frame being prepped to the same extent for plug-and-play use so your frame's BB shell may not have been faced in the past.
An "in between" variation is the FSA Megatech OS BB, which was designed as an open-standard to go along with the larger-diameter ISIS spindles. It uses 43mm OD cartridge bearings which are press fitted directly into an oversized (68mm OD) BB shell. In addition to the bigger bearings, the other bonus is the the OS shell allows larger weld zones for the frame tubes.
My frame was build with the "Megatech OS" BB in late '03. The framebuilder here thought it superior to the ISIS cartridge BBs, and I agreed. Appears never to have caught on, and now that the outboard bearing designs are here, doubt it ever will.
I've had the bearings changed out once at about 10K miles last year by my LBS. Seems they got contaminated with sand/grit, the typical thing that kills bearings in my experience. Like most cartridge-bearing designs, there are no contact seals on the spindles, just the standard rubber shields to "seal" the bearings.
Drawbacks to the non-standard system is that the bearings have to be ordered, and that a proper-fitting press kit are required to remove and replace the bearings. If I was buying another frame or bike, would just go with one of the outboard BB designs.
My frame was build with the "Megatech OS" BB in late '03. The framebuilder here thought it superior to the ISIS cartridge BBs, and I agreed. Appears never to have caught on, and now that the outboard bearing designs are here, doubt it ever will.
I've had the bearings changed out once at about 10K miles last year by my LBS. Seems they got contaminated with sand/grit, the typical thing that kills bearings in my experience. Like most cartridge-bearing designs, there are no contact seals on the spindles, just the standard rubber shields to "seal" the bearings.
Drawbacks to the non-standard system is that the bearings have to be ordered, and that a proper-fitting press kit are required to remove and replace the bearings. If I was buying another frame or bike, would just go with one of the outboard BB designs.
