Thorn single speed frame.

[4leksander]

This is my first post so HI EVERYONE 

I have been a long time fan of Thorn bikes but because of my preference to single speed I used other manufacturers until I found this:
(ups, where is my picture?Hopefully visible when posted)
Anyways, I have just found and without asking too many questions, purchased a lovely looking red frame that seems to have similar geometry to Thorn Audax.

I have been advised that this is an early Thorn model.
Could anyone help identify the frame model and details please?

I forgot to mention that I intend to build it for Audax type of spins. Perhaps someone has one built and would like to share their observations?

[Danneaux]

Hi and welcome, Alexander!

What a lovely frame; I can't wait to see it built up. It looks really versatile with two sets of bottle bosses, mudguard/rack mounts and routing for a rear brake.

While I don't have this SJS frame, I do have a 1970 road-racing bike I converted to single-speed/fixed use that appears to have similar geometry except for long, ramped road dropouts (with a derailleur hanger) instead of track ends so I can speak a little about this kind of bike in terms of setup for longer road rides.

My dropouts are spaced at a track-standard 120mm OLN so I am running a flip-flop rear hub -- fixed-gear on one side, single-speed freewheel on the other. I almost always ride the bike Fixed and use it in my early season training to get in shape quickly. I don't use the single-speed freewheel unless I will be going downhill a lot. I find the bike works well for up to 200km day rides depending on wind and terrain, but I have no problem getting it up 10% slopes if they are short and I stand (I use 38 x 16 gearing = 64 gear-inches) and spin. I cruise at 18-20mph/29-32kmh and top out at about 31mph/50kmh which seems fast enough in traffic. While I haven't ridden it in formal Audax rides, my use is similar and it works well -- again, provided there are not a lot of headwinds or steep hills. I usually fit a large Ortlieb underseat bag so I have some room for a wind jacket, 3/4 tights, and a longsleeve jersey in the early season as well as my patch kit, spare tube, a mini-tool, my 15mm "peanut butter" wrench for the wheels, and an energy bar or two. I have one bottle cage on the downtube and another two cages on the handlebars. I prefer 1 liter bottles, as it gets hot in the summer where I live and water sources can be few and far apart.

I ride in all weather, so I machined some axle adapters to mount mudguards and I prefer to ride with front and rear caliper brakes in traffic in case I need to stop faster than hop-skipping with a locked rear wheel would allow. Everyone has their preferences, but it seems the safety provided by good braking is pretty important. One last thing...I prefer to use 1/8in chains, chainrings and sprockets in this application as I find them more durable in my use when riding Fixed.

I hope something in the above is helpful. Dave Whittle (Thorn's Workshop Supervisor) will likely have a better idea as to the provenance of your frame and may be able to tell more about it.

Best,

Dan.

[Danneaux]

I saw yours on eBay a short while ago, so it is nice to see the story complete with you as the new owner. A quick search shows similar bikes on LFGSS. The photos might help give some ideas for your build:
https://www.lfgss.com/conversations/233475/
https://www.lfgss.com/conversations/177987/
https://www.lfgss.com/conversations/316423/
http://fatguycycling.blogspot.com/2004/06/ (on down the page a bit at that link)

Best,

Dan.

[PH]

They were quite popular at one time and a bit of a bargain, I expect they were bought in and were never part of the Thorn brand, quite basic but nothing wrong with that.  I have a recollection of SJS selling several non Thorn brands, Dawes at some point?  Though that may be a false memory...

[rafiki]

They were quite popular at one time and a bit of a bargain, I expect they were bought in and were never part of the Thorn brand, quite basic but nothing wrong with that.  I have a recollection of SJS selling several non Thorn brands, Dawes at some point?  Though that may be a false memory...

Yes, they sold Dawes bikes. I bought, and still ride today, a Dawes hybrid - the Mean Street XT, in 1994.

[4leksander]

Thank you for your replies,

This is some amount of valuable information. Massive thanks for that.

My current SS bike is Fuji Track and it is by far the most comfortable road bike I have ever been on. It is quite funny considering the only reason I bought it was bike shop voucher I got which would expire.
It is now fitted with drop bars, SKS mudguards and I prefer it over any other bike I have.
It is configured with 46T cranks and 16T freewheel giving 77 gear inches and it is suitable to relatively flat roads around where I live.
I fell in love with the simplicity and silence of a single speed.

While not the most important bit, I am still trying to find some information in regards to materials used and what was it actually designed to do (Audax, city commuter etc) but I am sure I will find all the answers some day 

I will keep your advice in mind when purchasing the drive train for it.

On the fixed wheel side, the freewheel gave up recently so I flipped the wheel and have to say it was an experience I will never forget. While cycling to work on back road, I saw a pothole and without thinking tried to bunny hop over it. This resulted in some peculiar acrobatics while I was trying to stay on the bike with one leg unclipped. I hope the driver behind me had dashcam and I will see myself on youtube some day.

That Fat Guy Cycling blog is very funny indeed.

I was in contact with Dave as I have been a fan of Thorn for a while and knew I will get an Audax some day. It just so happens that I need a road bike now so hopefully there will be another bike in the stable soon enough. I know about Audax mk4 but rim brakes, in my humble opinion, better compliment the frame. I understand there are advantages but stopping power with rim brakes never an issue. They are also significantly cheaper, easier to service and fix on the side of the road. This leaves me with mk3 I think.

Back to the subject...
I appreciate the fact that the frame is quite basic, but as you pointed out, there is nothing wrong with that. Probably no fancy tubing either but I want something that will be build strong and reliable. The fact that it was designed by people who know a thing or two about cycling comfort makes it even better.

I will be building wheels for it next week, so if you have any recommendations I will gladly take it on board. At the moment I don't know the wheel spacing, bb size etc so just waiting on frame to arrive early next week.

Once again big thanks for all the information.

[PH]

While not the most important bit, I am still trying to find some information in regards to materials used and what was it actually designed to do (Audax, city commuter etc) but I am sure I will find all the answers some day 

I'm pretty sure the tubing was advertised as Tange Double Butted, no tubeset range, that probably makes it 4130 cro-mo, equivalent to Reynolds 525, not as desirable as heat treated tubes, like Thorn's own, but not gas pipe rubbish either. 
What were they designed for?  I don't know, general purpose I think, brakes both ends so road rather than track, quite a few people used them as courier bikes, both for the price and the robustness.  I only know one person who had one and he used it for everything including Audax up to 600km.

[4leksander]

Thank you PH for your reply.

It looks like I made a very good frame choice.

 

[macspud]

700c Singlespeed Steel Frame - Raw Finish are still available from SJSC:

https://www.sjscycles.co.uk/frames/small-52cm-700c-singlespeed-steel-frame-raw-finish/

And Raw Finish Forks:

https://www.sjscycles.co.uk/forks/steel-fork-1-18-inch-steerer-for-700c-wheel-raw-finish/

[4leksander]

700c Singlespeed Steel Frame - Raw Finish are still available from SJSC:

Different frames though.
If geometry is the same then those might have been working prototypes perhaps.