BB of Isaac Proton FW - 42mm shell?

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dino0204
Posts: 52
Joined: Tue Feb 24, 2015 5:31 pm

by dino0204

Hi,

I have a problem with BB (currently I have Shimano SM-BB91-42) in my frameset Isaac Proton FW. I want to install Dura Ace 7900 crankset, but the axle is too short (or mounted BB is too wide). I press cups to the end. Maybe I must apply another bottom bracket?

Here are dimensions of shell in the frame:

Image

Another pictures:

Image
Image
Image
Image

If someone can help me, I will be very grateful.

Krull

by Krull

sorry, i am not well informed with this bb-stuff, but could those possibly fit?

http://www.bike24.de/1.php?content=8;na ... 413;lang=2

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bikerjulio
Posts: 1900
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Location: Welland, Ontario

by bikerjulio

I'm not a Shimano person but i have studied BB's.

Is that a MTB BB by any chance? It appears to be. Therefore for 5 mm wider cranksets.

I see that Isaac describe the BB as "BB Shell Hybrid: Integrated Shimano Press Fit". Completely meaningless and misleading. Shimano BB86 uses a 41mm ID shell standard.

Perhaps ask Isaac?
Last edited by bikerjulio on Sun Mar 15, 2015 10:22 pm, edited 2 times in total.
There's sometimes a buggy.
How many drivers does a buggy have?

One.

So let's just say I'm drivin' this buggy...
and if you fix your attitude you can ride along with me.

http://www.youtube.com/watch?v=GekiIMh4ZkM

Krull

by Krull

bikerjulio wrote:
Is that a MTB BB by any chance?


this is my suspicion as well (bit i did not have the guts to state it :mrgreen: )

when i "google" "sm bb9142" i get this:


http://www.bike24.de/1.php?content=8;na ... 164;lang=2

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bikerjulio
Posts: 1900
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Location: Welland, Ontario

by bikerjulio

I'm pretty sure that's a MTB BB.

That is a very unusual (Unique?) BB shell you have there. Does not fit any of the common types. See here

http://www.lightningbikes.com/cranks/bottom-bracket-shells.html

It's closest to a direct bearing fit BB386 EVO system, where instead of using PF30 cups, the bearings are pressed in directly to the frame.

This needs to be done very carefully, using the correct loctite and procedures.

To fit a Shimano style crank would then just need bushing adapters to get the bearing ID from 30 mm down to 24 mm. Wheels make the adapters - just a plastic bushing. http://wheelsmfg.com/386evo-adapter-for-shimano-cranks.html

I guess as an alternative you could try machining back the shoulder on those BB's you have already to allow them to sit more deeply. 2.5 mm off each side will do it. If I was in your shoes I would try that first.

There is yet a third possibility. The only difference between your shell and a standard BB 86 is that yours is 42 mm ID and the standard is 41 mm. If Isaac or anyone else can provide a sleeve that will get the ID down to 41 mm, then a completely standard Shimano BB86/91 road bottom bracket can be used.
There's sometimes a buggy.
How many drivers does a buggy have?

One.

So let's just say I'm drivin' this buggy...
and if you fix your attitude you can ride along with me.

http://www.youtube.com/watch?v=GekiIMh4ZkM

androidavies
Posts: 74
Joined: Sun Sep 29, 2013 4:34 pm

by androidavies

You may well find that if you tap one of the cups out, then pull out the plastic centre sleeve, then press both cups fully home, that they'll fit flush against the BB shell, and you can fit the crankset successfully. As far as I recall, it's the width of that centre sleeve that is the difference between the road and mtb bottom brackets, the cups themselves are the same fit. The sleeve may stop some water getting on the axle, but a smear of grease on it will stop any corrosion setting in.

Hope this helps!

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bikerjulio
Posts: 1900
Joined: Fri Dec 11, 2009 10:38 pm
Location: Welland, Ontario

by bikerjulio

That is a shoulder on the cup. They won't go in any further without removing it.
There's sometimes a buggy.
How many drivers does a buggy have?

One.

So let's just say I'm drivin' this buggy...
and if you fix your attitude you can ride along with me.

http://www.youtube.com/watch?v=GekiIMh4ZkM

5 8 5
Posts: 1315
Joined: Sat Jul 29, 2006 2:36 am
Location: UK

by 5 8 5

dino0204, are you using the 2.5mm spacer that is included with the BB? If you are, removing it would get you close to the 86.5mm spec of the crank.

"9" is the 2.5mm spacer

Image

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bikerjulio
Posts: 1900
Joined: Fri Dec 11, 2009 10:38 pm
Location: Welland, Ontario

by bikerjulio

It's a MTB BB. The spacer is used on MTB cranksets, but the lack of it will not fix the situation. The BB is 5 mm too wide for a road crank even without the spacer.
There's sometimes a buggy.
How many drivers does a buggy have?

One.

So let's just say I'm drivin' this buggy...
and if you fix your attitude you can ride along with me.

http://www.youtube.com/watch?v=GekiIMh4ZkM

5 8 5
Posts: 1315
Joined: Sat Jul 29, 2006 2:36 am
Location: UK

by 5 8 5

bikerjulio, I see what you mean.

Is the shell not just a BB86 (86.5x41) with the Shimano SM-BB91-42 BB pressed in because I'm wondering if the cups are actually 41mm inside the shell.

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jekyll man
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Location: Pack filler

by jekyll man

I can't see that the problem is the frame/BB.
With a total width of approx 80mm there should still be enough spindle sticking through, otherwise how would it fit bb86/90?

Maybe check to see if you have a strug chainset?
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bikerjulio
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Joined: Fri Dec 11, 2009 10:38 pm
Location: Welland, Ontario

by bikerjulio

The description for that BB is

High-quality Pressfit bottom bracket cups. Easy to install, increased durability because of the larger bearing size. Pressfit 91 bottom bracket cups can be used with BB30 MTB frames (bottom bracket size 84,5x42mm) only. All Shimano Hollowtech-II cranksets with integrated 24mm spindle are compatible with this bottom bracket.


Means Shimano MTB cranksets, not road cranksets though.

So this, plus the OP leads me to believe that the BB shell is 42 mm ID.

Since Isaac refer to it as "Shimano pressfit" it should be 41 mm ID but apparently isn't.

Unless OP has managed to press a 42mm cup into a 41mm hole :shock:

Perhaps Isaac normally supply a sleeve? Nothing useful on their site.
There's sometimes a buggy.
How many drivers does a buggy have?

One.

So let's just say I'm drivin' this buggy...
and if you fix your attitude you can ride along with me.

http://www.youtube.com/watch?v=GekiIMh4ZkM

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Frankie - B
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Location: Drenthe, Holland

by Frankie - B

Hold your horses with speculating... ;)

I've had the Proton version of this frame. you have the Proton Flyweight at hand. There is a shoulder inside the BB like on your drawing. It could be that there must be pressed two special rings against those shoulders. Then you press in a BB30 bearing and then follow up with the correct spacer for shimano. Let me run into the garage as I remember I have kept the box of the BB adapter.
'Tape was made to wrap your GF's gifts, NOT hold a freakin tire on.'
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Frankie - B
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Location: Drenthe, Holland

by Frankie - B

The adapter that was delivered with the frame was called System 42. I'd suggest that you contact Isaac directly.
'Tape was made to wrap your GF's gifts, NOT hold a freakin tire on.'
If you want to see 'meh' content of me and my bike you can follow my life in pictures here!

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dino0204
Posts: 52
Joined: Tue Feb 24, 2015 5:31 pm

by dino0204

Thank you for your interest.
Yes, now I have exactly this BB:
http://www.bike24.de/1.php?content=8;na ... 164;lang=2

It's for mtb, but probably Shimano doesn't produce 42mm BB for road.
I'm sure that shell in frame have 42mm, becouse I've tried with 41 and were too small.
I wrote twice to the company Isaac, but they haven't responded.

Bikerjulio have great idea with machining back of those BB. I need to try do this.
Another option is buying 42mm bearings and adapters, but I'm worried that I will give money and it will not fit again.

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