Shimano Biopace Replacement

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groberts
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Shimano Biopace Replacement

Post by groberts »

I would like to replace my Shimano Biopace 48=38=28 front chainring with something similar - if I can get the cranks off (see earlier posting) - any recommendations on what might be compatible? It runs with a x7 rear cassette.
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mattsccm
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Re: Shimano Biopace Replacement

Post by mattsccm »

Do you want the funny shaped rings? If so I think you may be in for an expensive shock as they are now very much the kit of the fast and well off rider. Look at the big shops catering to the racer or does Highpath still make them?
If you just want rings that are round you just need to get a set that match the bolt holes. Its called BCD and there are clever ways of measuring or you wait until some from this forum tells you.
Best way though is to spend 35 quid at Spa cycles and but a complete chainset for less than the price of 3 rings.
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cycleruk
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Re: Shimano Biopace Replacement

Post by cycleruk »

I swapped all my Biopace rings for round ones years ago.
IIRC the BCD is 110 & 74. My rings are 46-36-24T.
You'll never know if you don't try it.
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meic
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Re: Shimano Biopace Replacement

Post by meic »

Like they say 110BCD for the two larger rings and 74BCD for the inner ring.

Assuming that you are upgrading to normal rings:
because Biospace rings are not perfectly round, if you want to leave the front deraileur where it is you will be better off using a 50 tooth outer ring as the biospace is the same max diameter as a ring two teeth larger.
The middle ring will probably be OK with either 40, 39 or 38 and the inner ring will be fine from 30 to 24 probably.

Or you can use 48-38-28* again and lower and readjust the deraileur, it isnt hard to do.

* If buying rings separately now is a good time to down gear if you want to and the 28 can be replaced by 26 or 24 if you can see enough space below the chain inside the deraileur cage when on the smallest inner ring and rear sprocket.
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breakwellmz
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Re: Shimano Biopace Replacement

Post by breakwellmz »

I`ve got a Biopace chainring on my lightweight Raleigh singlespeed.Ifind i works well for me,here in Bath,despite initial scepticism.
If anyone out there has unwanted Biopace rings between say,between 38 and 42t,i would give them a good home.
groberts
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Re: Shimano Biopace Replacement

Post by groberts »

Thanks for that everyone. The current Biopace rings are fitted on my Trek 830 MTB, can't see why they did this? I had often looked down at the moving rings which looked warped, through this forum I now know they are eliptical - strange idea if you ask me. Anyhow, I have no desire to keep this feature and will revert to round rings and will probably get a full chainset rather than just the rings - I was wondering if the 'narrow' feature had any implications. This is an old bike (15 to 20yrs) and I suspect at the time x7 cassette and x3 chainrings was state-of-the-art, of course we've moved on since then.
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cycleruk
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Re: Shimano Biopace Replacement

Post by cycleruk »

The "narrow" feature is more to do with the cassette spacing. As the sprocket numbers went up the gaps between them logically got narrower. With "normal" chains the rivets poked out more and so would catch on adjacent sprockets and cause mis-shifts.
If you look at "narrow" chains the rivets are virtually flush with side plates and that is why you need special joining pins or use the newer joining links.
You'll never know if you don't try it.
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meic
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Re: Shimano Biopace Replacement

Post by meic »

Why did we have Biospace? Fashion, gimmick, something novel but it soon went out of fashion again.
Possibly you could argue that clipless pedals made them unnecessary.

I reckon the disadvantages of worsened gear changing and uneven wear make them worse than ordinary rings.

I take it that you are planning to replace the crankset for reasons other than the biospace rings as the crankset will be the same as for ordinary rings.
If you do choose to replace the crankset, you may need to buy a new bottom bracket unit of a different length.
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Brucey
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Re: Shimano Biopace Replacement

Post by Brucey »

if you must have identical biopace chainrings I may be able to furnish you with a set, at much less cost than the current custom offerings.

PM me if biopace is all that will make you happy.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
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meic
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Re: Shimano Biopace Replacement

Post by meic »

With regard to the "narrow" chain, it is as you thought a bit out of date.

Pretty much all of the chains you are now offered for deraileur gear bikes will be this "narrow" type.

If they are rated as 6, 7 and/or 8 speed they will be suitable and I for one happily use a chain tool on them though I do prefer to use a power link for convenience.
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groberts
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Re: Shimano Biopace Replacement

Post by groberts »

Still trying to remove the old bottom bracket!!!!!!

In the meantime:

Meic - why does the bottom bracket unit have to be a different length if I go to round chainrings?

Brucey - at the moment I am planning on going to an ordinary, round chainring but will get back to you if things change + thanks for the offer.
groberts
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Re: Shimano Biopace Replacement

Post by groberts »

Still trying to remove the old bottom bracket!!!!!!

In the meantime:

Meic - why does the bottom bracket unit have to be a different length if I go to round chainrings?

Brucey - at the moment I am planning on going to an ordinary, round chainring but will get back to you if things change + thanks for the offer.
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meic
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Re: Shimano Biopace Replacement

Post by meic »

The bottom bracket doesnt have to go a different length if you go to round rings.

It may have to go to a different length if you replace the whole crankset, rather than just the rings.
The bottom bracket length is meant to match the crankset rather than the frame.
You may well be lucky and they are the same or near enough.
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groberts
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Re: Shimano Biopace Replacement

Post by groberts »

I have now replaced my drivetrain (bottom bracket + Stronglite 48/38/28 tripple chainset + chain + cassette). Whilst the rear mech works fine, I am having a problem getting the front mech to work properly. I have adjusted the H & L and barrel settings by the book but find whilst I can change up OK through all the chainrings, going down the chain either moves straight across from the large to the small chainring or down to the middle chainring but then will not move again down to the smallest chainring.

My previous bottom bracket square taper spindle was 120mm, I pointed this out when purchasing the new equipment but was told that a 110mm spindle would be OK. I am now thinking it isn't! I presume the 120mm spindle would set the chainset a little further out from the frame (at the moment it is now very close) and thus provide more scope for adjustment of the front mech. Any thoughts / advice please?
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cycleruk
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Re: Shimano Biopace Replacement

Post by cycleruk »

Have you re-adjusted the hight of the derailleur to suit the new chainset?
It should clear the big ring by 1 to 2mm.

Check the recommended chainline of the derailleur. This should approximately line up with the middle chainring.
You'll never know if you don't try it.
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