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Discussion Starter · #1 ·
At a base price of $2250, the specs for the entry level Alu Fatback seem pretty good to me with, possibly, one exception. The reliability of the Truvativ Isis bottom bracket is questionable according to the reviews posted on MTBR and other forums. Folks claim to be blowing through bottom brackets every couple of months. Unacceptable, IMO, if true, especially when the proprietary design mandates the purchase of a new crank to be rid of the problem.

Living in Nome and 500 miles from the nearest bike shop, reliability is my main concern. And money IS an issue. A couple of other minor upgrades already has the price up to $2400 plus shipping. The wife, a non-rider, already views the whole purchase as an unnecessary extravagance. So is the Isis system total crap? Is it worth an extra $200 or more for a Fatback 15g (Reliability? Too soon to say?) or a Phil BB matched with a cheap, but solid square taper crank. Any other suggestions for a value-oriented, reliable crank/bb? I don’t need something to hand down to the kids, just a year or two of trouble free service.
 

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No, that's not phonetic
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I've run an FSA DH Isis BB in my Pugs for many years now. I'm still on my first one, and it has seen a lot of beach riding. It is not smooth anymore, but it still turns fine. Maybe ask Speedway to swap the Truvativ for the FSA. They cost the same.

The benefit of external bearing cranks is pretty compelling in that you can repack the bearings at will, whereas Isis BBs are not serviceable. You run the Isis until it dies, then shell out another $50 for a new one. After a few laps around that pool you have paid for the external bearing crank you were too cheap to spring for originally. FWIW, I have never worn out an external bearing BB because I am pretty good about repacking them before enough dirt gets in to cause them to die. I have many years on some of my original Shimano external bearing BBs now. My Isis stuff usually lasts about 1 year or two. The Pugs's BB has been hanging on longer. Ymmv, especially if you only ride the bike on snow. With the total lack of dirt, bearings should last a heck of a long time.

The Fifteen G cranks are things of beauty. There are other external bearing 100mm BB cranks out there like the Raceface Atlas and Surly Mr Whirly.
 

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bored ex-shop rat
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If you want stick to your ISIS cranks, go for the FSA.
I use one in my pugs and I don't want throw away my beloved R.F. NorthShore DH, 5-arm,
ISIS cranks
 

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No, that's not phonetic
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Another consideration is that the Truvativ BB uses the world's most retarded tool for installation- one of those giant toothed old-skool bb wrenches, while the FSA uses a newer nice positive-grip splined tool. I can't think of a single reason to use the Truvativ.
 

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is buachail foighneach me
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tscheezy said:
Another consideration is that the Truvativ BB uses the world's most retarded tool for installation- one of those giant toothed old-skool bb wrenches, while the FSA uses a newer nice positive-grip splined tool. I can't think of a single reason to use the Truvativ.
So, it's a negative that the Truvativ uses an existing tool as opposed to a brand new tool that the purchaser almost definitely doesn't have?

:thumbsup:
 

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if you have existing isis cranks, then get the fsa bb for them. if speed way is building you a bike, and you are purchasing new cranks, them i would definatly not buy the isis system. i had a race face isis bb go bad in a couple of months on my regular mtb.
 

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sean salach said:
So, it's a negative that the Truvativ uses an existing tool as opposed to a brand new tool that the purchaser almost definitely doesn't have?
Quite the opposite. I have a lot of legacy BB tools but none seem to fit the tooth arrangement of the Truvativ well. If you ever had Octolink BBs or Isis in the past you already have the spline tool for those. In fact I have a few. They are cheap too if you don't have one (which at this point seems doubtful).
 

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A different spin on tscheezy's comment....
External bearing BBs are great if you are good with your preventive maintenance; however, if you are like me... than you might be better off with the sealed bearings.
Both the TV and FSA BBs are a lot cheaper than anything else on the market and may actually last longer than the external bearings depending on how you care for them.
 

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bored ex-shop rat
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Don't forget the Truvativ Howitzer Team BB and crank option, it's also a good solution
and cheaper than the external BB/cranksets.
The BB cost less than 40$ and cranksets start at 60$, it's maybe a consideration.
The bearings are big and external
 

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I find myself...

...in a similar situation, VB, though I am in Bethel and my mechanic lives in Anchorage. I have the FSA ISIS BB in my Ti Fatback and have not had a single problem with it in two years, though admittedly don't ride as much as many others on this forum...not as much salt in the air here as in Nome either...
 

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No, that's not phonetic
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I should ammend my earlier comment about the needed Truvativ tool. This Park tool works, so if you have one sitting around (they were used for various BBs including the old Octalink XTRs back in the day), you could use it.

BBT-18:

 

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Billy--Arctic Cycles
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Truvativ ,FSA BB's

I have been renting Fat Bikes for over five years and Winter bikes since 1997. Yes,Tscheezy is correct the internal BB's are maintenance free . But with the Truvativ Isis, I have had problems from the start. I only use the FSA Isis now . I have not had any problems with BB's since.

Hope this helps,Billy
www.arcticcycles.com
 

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bored ex-shop rat
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Or the Shimano TL-UN96-A, precise machined, no cheap cast, fits perfect with the
Truvative ISIS BB cups.

 

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Discussion Starter · #16 ·
Good information here... thanks everyone.

There's a lot to digest here for a BB newb. First a couple of comments specific to my situation: Speedway will build the bike from the ground up (no existing parts to use). Starting from scratch, sounds like I should try to avoid the ISIS if possible. If not possible due to budget reasons, there's some consensus that the FSA DH is the better option. Summer use is definitely in the picture -- lots of beach riding potential here -- so salt and grit penetration is a concern.

Tscheezy, the external BBs are sealed, too, right? Does easier to service also mean easier to contaminate? Do you repack every coupla months or so? Is there a tool for getting grease into the bearing cartridge? Velopax, the TV Howitzer sounds like a cheaper take on the higher end externals like 15g and Surly Whirly. Do I have that right? Is it considered a fairly solid BB?

Interestingly, no one said they would go with the Phil BB and a cheap square taper crank like, say, the Sugino XD triple.
 

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bored ex-shop rat
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veloborealis said:
the TV Howitzer sounds like a cheaper take on the higher end externals like 15g and Surly Whirly. Do I have that right? Is it considered a fairly solid BB?
The Howitzer BB Is a very solid solution, TV use this type of BB on all FR & DH sets,
you have the choice between the Blaze, Husselfelt, Holzfeller or Holzfeller OCT cranks all
available stock as 1, 2/w bash or 3 ringed version, only the Howitzer Team BB is as 100mm
version available.
 

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All non-Wal-Mart bike BBs are "sealed", just some more effectively than others. As far as non-serviceably BBs go, I would say the FSA Isis DH 100mm is "well sealed."

Quality external bearing BBs are just as well sealed, or better, than Isis models because they generally employ an extra dust shield over the actual bearing (such as Shimano's). These work quite well, and if you clean and repack the bearing twice a year (spring and fall) you should get a couple of years out of the things. Chris King makes an external bearing BB now which is very nice, and you can get a grease injection tool for it (sold separately, natch) so that you don't even have to pop their seal retaining ring out. I overhaul my King BBs only once a year, and while the grease is gone they are otherwise clean inside and I just add new grease (I don't own the grease injection tool). Their BB costs 3x what a cheapie Shimano costs, but if it lasts 3x as long, then they cost the same.

If cost is an overriding factor, get the cheap Isis cranks and the Isis FSA BB. That will last you years. If you want the ultimate, either get the 15G setup, or if you want the best durability, the Chris King external bearing BB with any compatible crank (Surly Mr Whirly or RaceFace Atlas) would be a great option. Or you could find some square taper cranks and get the Phil Wood BB. I have no experience with this last item.

Since Speedway is building it, and you are on a budget, and it would be easiest for everyone involved to be able to use easy to find off-the-shelf parts, just get the FSA Isis DH BB and the cheap Isis cranks and revisit the whole thing in a few seasons when the upgrade bug bites.
 

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i am upgrading to Phil Ti bb and Middleburn cranks when my bb goes. i do like the speedway/15g combo and will have to see if it comes in lighter than the Phil Middleburn combo i plan to use. both systems lock me into a crank and bb combo.

long term durability in the harshest conditions is not of concern for me. i dont ride in the tundra so i can get away with lighter xc stuff.

to sum it up i think we can agree on the following,

Truvative-questionable durability, lots of crank arm options, cheap.
FSA-works, but will eventually develop issues, lots of crank arm options, cheap.
External BB set up- can be rebuilt when contaminated, locked into arms, expensive.
Phil square taper- has been around way longer than the rest. unknown on the long term durability because they are not as popular. cheap cranks are available, but you can get light expensive ones also.
 
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