New Bb With Cranks?

[Ed91]

Hey, I used to be of the philosophy of buy cheap parts then replace them when they break, but now that I'm fixing up my old bike with decent gear, I've been caught out.

I want a new set of Middleburn cranks, but should I buy a new bottom bracket with them? I know I don't have to, but seeing as they cost so much I don't want to stick them on something that's going to ultimately destroy them, and if I should get a new BB, can anyone recommend one to me, as it used to be a simple case of sticking a cheap one in there and going with it!

Thanks, Ed

[ZHI-sam]

hey,

if you get a set of isis burns and kill them i will personaly take my socks off and eat them infront of you lol

yea i would replace the bb if youve been using old componants. you dont know how long it will last after all. i hear good things about the FSA ones

[Danny Kearns]

Hey mate, i know just the bottombracket for you but it all depends on your price range.

The bottombracket you should take a look at is the SKF BFR - 600 That link there takes you straight to tartybikes with the bottombracket i am talking about, if you are unsure give Dave and Adam a phone call (landline phone number is at the top of the page) and they will be more than happy to answer any of your questions and to point you in the right direction.

But i have heard good things about that bottom bracket and i would highly recommend it, but it depends if you have the money for it.

Dan.

[Ed91]

Thanks for the replies, I think my budget is fairly flexible if I use my trusty overdraft to tide me over to the next paycheck! So second question, when I stopped riding 4 or 5 years ago after completely messing my shoulder, I don't think (or at least can't remember that) ISIS cranks/BBs existed.

I know there seems to be quite a debate about them just by looking through other threads in forums, but if anyone could shed some light on the subject of which is better for trials that would be a great help!

I read one thread praising their strength, then another saying they mess up cranks after removing them a few times.. all pretty confusing for me!

Thanks again, Ed

[Danny Kearns]

Isis cranks/bb's are the new way forward in trials, almost everybody is using isis now days, i don't know where you have herd it wrecks the splines after taking them off a few times because it doesnt, You can not round isis cranks off like taperd one's and you do not have to tighten your cranks up as often.

As for strength wise, i think isis is alot stronger now days, i have had alot of trouble with taperd cranks and bb's, but i have never had a problem with isis cranks/bb's.

Isis will be your way forward for trials riding.

Dan.

[Mike W]

get an isis skf iv had one in my t-comp and there indistructable

mike

[bionicman]

i use a burn crank with a koxx try-all bb i dont recomend buying fsa i snaped two of them in 6 months and they were the fsa platinum pro

[nmt_oli]

I read one thread praising their strength, then another saying they mess up cranks after removing them a few times.. all pretty confusing for me!

Thanks again, Ed

i don't know where you have herd it wrecks the splines after taking them off a few times because it doesnt, You can not round isis cranks off like taperd one's and you do not have to tighten your cranks up as often.

As for strength wise, i think isis is alot stronger now days, i have had alot of trouble with taperd cranks and bb's, but i have never had a problem with isis cranks/bb's.

Dan.

The ISIS interface is inherently stiffer, and allows for the use of a larger diameter axle to increase strength. Unfortunately however, the larger axle means there is less room for bearings, so in most situations the load capacity of the BBs are reduced, or they don't last as long, or both. Various methods have been devised to prevent this, such as the external bearing BBs, although the mentioned SKFs seem the best on the market at the moment.

You are right about the actual taper causing problems over time. Square taper cranks work on a fully tapered interface, you can just keep going if the crank becomes slightly loose, wheres the ISIS taper has a much shallower angle, and actually has a stop, so unlike square tapers which you can keep forcing when the taper wears a little, the isis cranks push on and stop at a set point. If any play develops, which it can after a lot of use (accelerated by multiple removal of cranks) then there is no way of getting rid of it, the taper is permanently damaged. I've seen this happen to a few cranks, including middleburns. you undo the crank bolt and you can just slide the crank off, no need for an extractor.

Square has been around almost forever, and i think it will have its place for a long time to come yet, its simple, cheap, universally known and easy to maintain.

ISIS is a great solution for the more extreme ends of biking nowadays, which inherently have shorter lifespans on high stress parts such as cranks any way, so you may be able to justify the reduced longevity for the extra strength.