gitaneusa.com :: View topic - What is the frame material on a 70s Grand Sport De Luxe?

r1st

Hello,

I am looking to by a Grand Sport De Luxe Mixte for my wife and i wanted to know what the frame is made of.

I am looking to build the bike into a single speed for her to commute with. I have fund a bike that is in good condition but is in poor working order due to lack of use. I will be replacing the brakes, BB, and Crank.

Any advice of info on the frame would be greatly appreciated.

Thanks

sandranian · Site Admin

The frame on that bicycle is made out of steel.

I am curious as to why you want to or need to replace the bottom bracket and crankset? Even the brakes most likely only need to be repaired and cleaned up (perhaps the brakepads replaced). The bike will also be French threaded, so keep that in mind when making your decision regarding the bottom bracket.

r1st

I guess I should have been more clear. I know it is steel. I am looking for more info as to the type of steel used. Is it High Tension or Chromoly etc.

As far as the replacement parts, I am actually just going through a mental worst case senario.

sandranian · Site Admin

It is likely not chromoly. Catalogue lists it as "seamless lightweight steel".

http://www.gitaneusa.com/images/catalog/1970_pg11.jpg

verktyg

r1st,

Greetings,

The terminology used for describing various materials used in bikes, especially steel, is laced with misnomers and marketoid poetic license.

The term "High Tension Steel" has come into popular use probably through "Jiglish" - the Japanese translation of High Tensile Steel. Rolling Eyes

"High Tension" would indicate that something was in a stress loaded condition such as the steel reinforcing rods in prestressed concrete construction components or high voltage electrical transmission lines etc.

High Tensile Steel, like Hot Rolled Steel, Cold Rolled Steel, Heat Treated Steel are not accurate technical descriptions. They don't indicate the chemistry or mechanical properties of a given steel. For example 4130, 1018, 304SS and so on are standardized AISI/SAE designations used in the US and some other countries. Those numbers provide much of that technical information. Other countries have equivalent designations.

"Chromoly" is another one of those magic terms: Chro-Mo, Chromo, CrMo etc. have come to mean a Chrome Molybdenum Alloy Steel most frequently 4130 steel.

Much of the Columbus tubing was made with an Italian equivalent alloy steel. So was Reynolds 501 and some of the Vitus tubes. Same thing with the Japanese brands Tange and Ishiwata. Reynolds 531 (and 753) tubes were made of a similar alloy steel except the Chrome content was replaced with Manganese (not Magnesium).

The mechanical properties of these CrMo and MnMo alloy steels are all about the same! Shocked

So, back to your question about the Gitane Gran Sport frame...

The Gran Sport was Gitane's entry level model. Those bikes were made with seamed carbon steel tubing also known as "Gas Pipe Tubing". The wall thickness of the tubing was about 1.5mm. Many similar bikes used tubing as thick as 2mm!

Alloy steel tubing is 30% to 50% stronger than carbon steel tubing so the wall thickness can be less. The advantage of thinner tubing is that it makes for a 1 to 2 Lb. lighter bike but more importantly a better ride.

That said, a lighter weight person on a smaller frame size bike may not notice a difference in ride until they move to a frame made of very thin wall specialty tubing.

It's only in the mid range frame sizes 56cm - 60cm where a casual rider over 150 lbs. is going to really notice a difference in the ride between a standard production Reynolds 531 frame and a Gran Sport. In many cases heavier riders on larger frames like the feel of the heavier tubing!

(In my experience, riders under 150 Lbs. don't weigh enough to flex the frame sufficiently to feel the real advantage of light weight tubing, especially on smaller frame sizes. The "Princess and the Pea" applies here. Also, don't confuse RIDE with HANDLING)

When I was selling bikes in the 70s we preached two things: buy a bike with a nice riding frame and get light weight wheels! Wink

Gitane Gran Sports were nicer riding than many competitive makes of that era. I had several of them myself.

Your Gran Sport probably has chrome plated steel rims. The biggest improvement that you can make to the bike is to get a set of alloy rim wheels! They will take from 1 1/2 to 3 Lbs. off the bike and improve both ride and handling.

The steel cranks are probably the least important component on the bike. As long as the rings are straight and the chain doesn't come off while pedaling (not when shifting gears), I'd leave that until last.

Brakes, tune them up and replace the pads or get some of the new Shimano or Tektro dual pivot brakes (on special now).

http://tinyurl.com/ylcz7x6

Seat, get one of the seats designed for women.

Alloy rims. The GS bikes came with 27" wheels. The current standard is 700c which is about 4mm smaller in diameter. 700c tires are more readily available. The old wheels had a rear axle width of 120mm. In the 80s the standard changed to 126mm with 6 speed freewheels then in the 90s to 130mm wide with 7+ speed gears and freehubs. Check eBay or local bike shops for some older 120mm wide alloy wheels.

Dérailleurs, the older Simplex derailleurs were not the easiest to use or adjust. It the bike has Suntour or any later model derailleurs clean, lube and adjust.

Cranks, alloy aluminum cranks are cotterless and require a bottom bracket axle with square ends. The bottom bracket on GS bikes had French metric threads. You'll have to find a Stronglight, TA or Japanese cotterless BB or else buy one of the new sealed bearing metric thread BBs from Velo-Orange. The axle widths vary so you will have to match it with whatever crank you choose.

Pedals, the old steel cranks take metric threaded pedals. Many cotterless cranks take the standard British threaded pedals.

This project can start costing quite a bit so unless the frame is in pristine condition or there's some emotional attachment, I'd think twice about "putting silk stockings on a rooster".

Back in the 70s I built up a Gitane Gran Sport mixte for my Brother-in-law and niece using moderate quality alloy components. It weighed about 25 Lbs. and was a nice riding bike.

While I collect mid to high range bikes, I'm not really a bike snob. I've done a lot of riding so I'm more fussy about my steeds than a casual rider might be. It's the joy of riding that counts. I recently overhauled a 1972 Peugeot mixte for a friend. I was really surprised by how nice it rode!

Good luck and have fun with your project...