HELP WITH BOTTOM BRACKET FOR 1990 ALPINE STARS AL-MEGA DX

[drexal77]

Hi Guys,

Been a while, hope your all well.

I'm still trying to restore my 1990 al-mega (pre e-stay) but only getting to spend a day on it every so often due to family etc.

Really hoping someone might be able to help me with the below question, not getting a definitive answer from goggle.

I would love to find a NOS bottom bracket that this bike would have come from out of the factory. Does anyone know what the AL-MEGA DX would have come with in 1990? i know they used cheaper headset & pedals etc on the Al Mega DX model so the BB might have been a cheaper model also.

It currently has a plastic SKF BB which is super rough & sandy feeling, which i've been wrestling to get off ( i don't want to measure this current BB and replace like for like from the measurements as i'm not even sure it was the correct fit, because the amount of gouges in the chain stay (but i know this can happen even with the right BB in place).
I thought i should probably order a replacement while i struggle removing the SKF. The bike will be running a triple crank set Shimano FC-MT60 (170) with (C-46, C-36 & C-24 rings) The al-mega has over size tubes which has thrown me slightly as the sheldon brown website says you need to get a BB that compensates for this because of the front derailleur! I would like a shimano BB from 1990 really so its period correct, but if you think a the UN72 or UN91 would fit and would be a better bottom bracket (or happy to take on board any suggestions / different brands) that would help widen my search other wise i'm stuck with NOS etc.

Any help is massively appreciated.

 

[gtturbo]

Generally for a MT60 chainset you want a 122.5mm bb. Of course you then have the option of a 68 or 73mm shell so will need to measure your frame. If I manage to get at mine, it's buried, I will see what size it is. In 1990 we were still pre sealed cartridge bb from what I remember so that's the UN72 or UN91 out if you want it to be 100% correct.. That said there is not a huge choice anymore so get the best you can. If you can get a UN72 or 91 in the right size go for it. I would avoid the UN300, modern replacement, as it's crap really. I have a Token sealed BB on one of my bikes and that seems OK. Have you checked out the catalogue here for the specs - https://www.retrobike.co.uk/archive/1990-alpinestars-catalogue.280/

 

[drexal77]

Thanks so much @gtturbo for reply and help, ahh ok that makes this sound way more simple, don't worry about trying to get yours out to measure just checked mine and its a 73mm. Ok i'm going to start the search for a UN72 or 91 in 73mm 1.22mm if i can find one. Thanks so much again.

 

[gtturbo]

Good luck. I was looking for a 73x122.5 and that particular size seems to have really limited options, which is why I ended up with a UN300. Whilst you have the calipers out what's the length on the current axle just for comaprision to the 122.5 although I am 99% sure its 122.5 you want.

 

[drexal77]

Good luck. I was looking for a 73x122.5 and that particular size seems to have really limited options, which is why I ended up with a UN300. Whilst you have the calipers out what's the length on the current axle just for comaprision to the 122.5 although I am 99% sure its 122.5 you want.

Sorry for delay, family came home spindle length total is 126.5 & drive side protrudes roughly 2.5cm & none drive side roughly is 2cm, not sure how well this worked as the bike was un-rideable so i stripped it straight away. Ps thanks for catalogue i did check it, but it just says sealed mechanism for BB.