Drop out and fork spacing

[Uncle Monty]

Had a quick look around the web. I have a rear drop out spacing of 115mm or 4.5" and a fork spacing of 95mm or 3 and 3/4". For a 1954 bike would this have been the norm? I see much more in the way of 120/100mm hubs from the same era, so would it have been common practice at the time to just spring in wider hubs, cold set the frame and fork, alter cones and spacers, or would the correct width of hub be commonly obtainable and used at the time? 5mm is not much to gain but they certainly don't just drop in as they are.

Cheers - Chris.

 

[sisyphus]

I think its common to have that rear spacing for have an old bike. I've an old Holdsworth - 1951 - with that spacing 115.....but I've put in a wheel with a 120 hub without any problems - its just not going to slip in as it should.

 

[Takingabreak]

Re:

I think the 115mm spacing was for a sturmey archer hub

 

[keithglos]

Re:

British bikes were almost all made 4.5 inch rear end until we started using campagnolo QRs, towards the mid 50s. These bikes were made for a 1.5 inch chain line. For 10 speed systems we needed a 1.75 inch chainline, so some mods were in order.
By 1955 I was ordering frames with Campagnolo ends and 4.75 rear spacing.
If you look at a BH airlite or Harden rear gear sided hub you will see that the gear side spokes would be nearly vertical. We used tubular tyres with stronger rims, like Fiamme and Mavic, and spaced out the rear to improve this.
Keith

 

[Uncle Monty]

Re:

Thanks for the replies folks. That's interesting Keith, I guessed it was 4 1/2 inch spacing. This is the Hetchins I am playing with. Simplex drop out with the hanger hacked off. I have had a re- think and picked up an early Simplex lever and a suicide front shifter. Hopefully a matching rear mech will be with me soon. I intend to use it with a bolt on hanger. The double Simplex chainrings and Duprat cranks are I think original. The wheels are a mess and I don't think I will be able to use the steel Dunlop rims. They have big dents in the braking surface and are badly pitted and rusted. The hubs are OK and could be restored. The centres would need removing and re-chroming. Spokes have had it. I have picked up some Fiamme rims of the same drilling as the originals. They are already built up with Campagnolo hubs. I can either try to make these fit as is, or strip them down to rebuild with my original hubs. Can you explain a 1-1/2" chain line to me and hazard a guess as to if this was originally 4 or 5 speed at the back? The whole "what spec was the drivetrain and what am I going to do about wheels" thing has been a bit of a show stopper. I have decided to give tubulars a go as this opens up the options on rims a bit.

Cheers- Chris.

 

[jon w]

You spacings sound about right. These were often for 3 speed though. I've just got a 1951 3 speed with a cyclo going and just had the space to get it all in.

 

[Uncle Monty]

Re:

Re - reading above, 1.5" chain line would be exclusively 4 speed? The 1.5" is taken from BB centreline to the middle of the freewheel gears and the front chainring(s)?

My rear mech arrived. A Simplex Juy which I think is a Tour de France although I am not 100% on that. It has a pressed steel cage not alloy. Single cable design. The front one - a Simplex Competition I picked up at Ripley. Now that I have it in my hand I can see where the two cylinders fixed to the rod match up with chips in the paint. Before I had this, I could not see where a front changer had been fitted.

My wheels turned up - really pleased with those. 1950s Fiamme sprint rims 32/40 laced to Gran Sport LF hubs complete with QRs. They are light and true and just need a bit of glue removal. I feel inclined to perhaps play with the spacers and try and lose as much of that extra 5mm width as possible, then re-dish the wheel. I think I need a freewheel to play with and check it all fits before I do that. In period, were folks fitting a Gran Sport hub like this to a 4.5" wide frame and would they still be using 4 speed freewheels with them or would a five speed be more in keeping? As it came to me, the original hub, which I am not 100% what manufacturer they are, despite being only 4.5" wide had a 5 speed 12-28 freewheel fitted of Japanese manufacture, so there does seem to be room for five. Once I have a suitable freewheel and have proved the combination of parts all work with one another, I can start to put this thing together.

Cheers - Chris.

 

[sisyphus]

Sounds like a fascinating build.

 

[Uncle Monty]

Re:

For me its a steep learning curve. The Simplex deraileur could be 4 speed only. It does not have any marks saying 4 or 5 speed, so I won't know until I try a freewheel.

 

[sisyphus]

If you ever get time to post any pictures of that bike.....