To Anyone with 80's Moto Frame Knowledge
 

I've got an early to mid eighties Motobecane Mirage, on which I've upgraded everything but the frame. I'm unapologetic, unabashed (I know where I'm posting this) and thrilled with the results and love the ride above my newly manufactured road bike. With the new Wheelset, I've surpassed my goal weight: a svelte 23.5 lbs! :p

I've got a question about the frame itself - more than any bike, particularly newer bikes, I've realized a rather dramatic weight differential between the front and rear in the frame itself. lbs guy, more a wheel guy, was pretty sure that all of the tubing was chromolly (Motolite?) except the seat tube which may be a cheaper heavier grade.

This is for curiosities sake. Any info mid-eighties Moto frames would be appreciated.

Your Mirage has a high-tensile steel frame, 2040 I believe. I wouldn't hang my head over it though -- pay no attention to these CrMo snobs. :D

No issue of pride here as the frame itself is liable to be replaced in time, but I don't think it's 2040, though still, might not be Chromolly.

Any clues how to find out and if Motobecane ever used mixed grade tubing?

Based on the Motolite reference, the frame sounds circa 1983/1984. Is it inexternal brazed? While I have no objective evidence to support this, I believe that Motolite was a manganese alloy tubing. I have a couple reasons for this. First, the lower Nomade used still used 2040 during this period while the higher Super Mirage used CrMo, implying that Motolite fell between 2040 hi-tensile and CrMo tubing. With the exception of Reynolds 531, most tubing manufacturers postioned their manganese alloy tubesets between their hi-tensile and CrMo offerings. Secondly, this was era where the lower priced manganese alloy tubesets (ie Mangalloy, MangaLight, etc) first started to appear.

Motobecane definitely offered mixed tubing frames. However, the common practice was to use better tubing for the main traingle and economize on the rear stays and/or forks. For instance, the 1984 Super Mirage has a tubing label that specifically says "3 tubes CrMo'. and boom era models, such as the grand Jubile, used Reynolds 531 only for the main triangle.

A seat tube is in the middle of the frame and would have relatively little affect on the weight distribtion, as opposed to a rear triangle made out of thicker material. However, the tubing type of the seat tube can be assessed, to a certain degree, based on the seat post diameter. The premise is that stronger alloys permit a thinner tubing wall thickness and consequently larger seat post diameters. Most hi-tensile steel seat tubes use 25-26mm posts.

Through the late 1970s a Mirage would be, as MSwantak stated, 2040 Hi-Ten, I'm pretty positive of that as I bought the one step lower Nomade in 77 or 78 and it and the Mirage shared the same frame the difference being the Mirage had SunTour shifters and a 2 tone paint.

Though I obsessed on Motos during that time range I stopped during the 80s, eventually ending up on a Cannondale. However, from what I've seen since on eBay Moto expanded the Mirage label and some of the bikes could well be chro-moly or as T-Mar posted a Manganese alloy. Unless you dropped serious coin on ultra light wheels and maybe carbon bars I don't think you'd get a 2040 frame down to 23.5.

I swapped out a lot of parts on my Nomade which started at a claimed 29# and I doubt I got it much under 26# though it became a pretty nice ride.



:beer:

:rolleyes: Hey there,
I just picked up a Mirage from a local Police auction. There is a sticker on my frame on the seat tube, right underneath the main tube, that states, " 1020 Steel, Tubes, Forks & Stays". I wonder if the quality of the frame in the Mirages changed during the model's life span?
I have no idea what vintage this frame is, (my first Motobebane), so any help in dating it would be appreciated. The numbers underneath the bottom bracket are: 3692828-701. There is also a "609" marked above the other numbers.
I have plans to build a beater fixie out of it. I have a Maillard track hub that will match the Normandy up front, a Stronglight T/S crank, and some 700c Sun rim's around here somewhere......

Hey there...

I have a beautiful 1985 Motobecane Mirage that is indeed Crmo...;o)

Look on the wheel hub for a date. That is how I ID'ed mine as 1985.

Cheers
Alice