thorn xtc

[LithiumDeb]

I have just purchased an old Thorn XTC - advertised as 2008 and a 490S. I've no real idea what type it is as it doesn't seem to match any of the frame geometry I can find on the forum and old documents.  Unfortunately nearly all the xtc info seems to be about the 853 version.

Its frame number starts 90 and ends -JS. It is from 725 tubes with lugs and has Ritchey drop outs on straight stays. Some dimensions (approx) are:
WB 1010mm,
seat stay 425mm,
virtual tt 535mm ish
head tube 128mm
Seat T c to c 460mm
Frame size 500mm
stand over ht at top tube 760
BB ht 277mm
TT dia 29.2mm
ST dia 29.4mm
DT dia 32.5mm

It would be great if anyone could thread any light on it. I have been out for a couple of spins and it is a really lovely ride and with 1.5 wide tyres it rides the potholes remarkably well too. Very pleased with it and I hope to take it to Spain for my hostelling tour in the summer. Mostly roads but a couple of days on old mining tracks. I reckon if I'm careful and with not much luggage it'll be fine. I've been over the Corrieyarick pass in the Highlands on my Joey with no ill effects.

The only other question is - do I put a motor on it... see my other thread soon to be posted. Sorry, I've no idea how to reference it.

In hope.

Deb

[LithiumDeb]

OOps. What I called the seat stay should have read - chain stay

[PhilD28]

It’s possibly an xtc short wheelbase (swb), I believe they were only  built in reynolds 725 conical tubing, mine certainly was. If it is of lugged construction rather than fillet brazed and with just enough fork and chainstay clearance for 1.5” tyres that would probably confirm it.
If it is it’s a superb bike.
I did 1000’s of miles on mine and when I sold it the frame was like new, they were very well built.

[brummie]

Hi Debs, This one?https://www.ebay.co.uk/itm/333515938774
Looks like an XTC classic ( the original Thorn XTC ) Handbuilt onsite @sjscycles - probably by Kevin Sayles ( KS stamped on BB? ) The XTC  SWB model didn't have the low loader bosses on the fork leg.

[macspud]

Its frame number starts 90 and ends -JS.

Puzzling, frame numbers from 90 to 99 were Reynolds 853 as far as I know.
http://web.archive.org/web/20060321060909/http://www.sjscycles.com/thornwebsite/thornpdf/ThornxTc853BroHiRes.pdf

It’s possibly an xtc short wheelbase (swb), I believe they were only  built in reynolds 725 conical tubing, mine certainly was. If it is of lugged construction rather than fillet brazed and with just enough fork and chainstay clearance for 1.5” tyres that would probably confirm it.
If it is it’s a superb bike.
I did 1000’s of miles on mine and when I sold it the frame was like new, they were very well built.

SWB had frame numbers from 80 to 89.
http://web.archive.org/web/20010712021014/http://www.sjscycles.com/26solobrochure/solobrochurewebp16.htm

Hi Debs, This one?https://www.ebay.co.uk/itm/333515938774
Looks like an XTC classic ( the original Thorn XTC ) Handbuilt onsite @sjscycles - probably by Kevin Sayles ( KS stamped on BB? ) The XTC  SWB model didn't have the low loader bosses on the fork leg.

Did they not have frame numbers from 70 to 77?
http://web.archive.org/web/20010712021014/http://www.sjscycles.com/26solobrochure/solobrochurewebp16.htm
Also, should it not have a Reynolds 753 Conical sticker?

It does get confusing as the old brochures get lost to time.

Photos would help.
 

[PhilD28]

The swb classic was definitely built with 725 conical tubing, I owned one for 15 years. A great bike although slightly twitchy on the front end compared to the XTC.

[LithiumDeb]

Hi,

Thanks all. The Brummie link to the add is the actual bike. I think PhilD28 has the best answer.

The Reynolds decal doesn't say Conical but it has been added post painting as I can scrape up the edge! I have remeasured the top tube and it is much bigger diameter at the head tube than at the seat tube so it is definitely conical tubing. So it's most likely a SWB Classic then.  The frame number matches with a short top tube bike page I found via the forum.

It's still mighty confusing though as the dimensions include those from an XS to a medium. Even smaller than an XS wheelbase with a M tope tube and a seat tube between XS and S. Maybe it was a one off, just based on a 490S using the 90 frame number series?

Whatever, after changing the saddle and adjusting bits and pieces I'm looking forward to getting out and about on it.

[PhilD28]

I really wouldn't worry too much about the precise model, although if it's conical 725 and lugged its  almost certainly an xtc SWB classic. If you find the front end slightly twitchy, I suggest Schwalbe marathon supreme  tyres in 1.6" size and run them at about 40 psi front, that calms things down nicely.

[macspud]

Hi,

Thanks all. The Brummie link to the add is the actual bike. I think PhilD28 has the best answer.

The Reynolds decal doesn't say Conical but it has been added post painting as I can scrape up the edge! I have remeasured the top tube and it is much bigger diameter at the head tube than at the seat tube so it is definitely conical tubing. So it's most likely a SWB Classic then.  The frame number matches with a short top tube bike page I found via the forum.

It's still mighty confusing though as the dimensions include those from an XS to a medium. Even smaller than an XS wheelbase with a M tope tube and a seat tube between XS and S. Maybe it was a one off, just based on a 490S using the 90 frame number series?

Whatever, after changing the saddle and adjusting bits and pieces I'm looking forward to getting out and about on it.

The 853 also has conical tubing. If the frame number stamped into the underneath of the bottom bracket is 90 then surely it is an 853? I thought that until very recently the stickers were placed under the clear coat, not on top? Has the sticker been replaced with the wrong one?

Whichever model it turns out to be it looks to be a beautiful bike. 

[LithiumDeb]

Thanks for all your assistance. I don't really mind what it is and as the front forks have low loader bosses I assume they must be strong enough. As this bike could be purchased custom sized that is my thought. It fits me well enough and that's what counts.

I went out on it twice today - including getting caught in a nasty hailstorm. No front end twitching whatsover on 1.5in nimbus tyres running at about 40-45psi. It's a joy compared to my other bikes.

Roll on Summer.

[PhilD28]

Ah, if it has braze ons for a front rack its unlikely to be an xtc swb classic as they had lighter forks that couldn’t take front rack, are you sure they aren’t mid mounted mudguard eyes?
It’s possible the forks have been swapped out or it’s a custom build, in which case Thorn will be able to provide details from the serial number.
Glad it rides nicely and you are pleased with it. I think all the xtc variants from that period were excellent bikes. I have an 853 xtc that I use as a winter bike, a very nice machine but not as nimble as the xtc swb I sold.
I also have a custom built Woodrup 650b frame I had built to my design by Kevin Sayles a couple of years ago to replace my xtc swb and it’s just about perfect, a bit lighter than the xtc swb and it fits me better. So Kevin is still building great frames in Leeds.

[PH]

Looks a lovely bike and really good value as well.  Wishing you many happy miles on it.

[macspud]

It’s possible the forks have been swapped out or it’s a custom build, in which case Thorn will be able to provide details from the serial number.

Yes, best to get in touch with Thorn. You can disregard all my waffling about it maybe being an 853 frame, they were fillet brazed and filed,