I'm looking to change the frame of my Dawes Century SE (Audax bike) as it has never really fitted me; size issues are too steep seat angle (I have to push the saddle back further than the limits to be comfy) and it's also a bit shorter than I like. My Spa tourers are longer and I find much more comfy. At the same time the ability to have 28mm tyres is an aim too.
Looking at Thorn's frame sizing the 570 looks perfect for me being very like my tourer, BUT according to their sizing guide I should be in a 550. What have I missed?
On a separate note I can't find any info about the head angle, does anyone know what it is?
Thanks in advance
Chris
"Marriage is a wonderful invention; but then again so is the bicycle puncture repair kit." - Billy Connolly
Thorn won't give complete geometry information; they say they don't want their competitors to know! However such things can be measured and I have a CTC review of an Audax MK 3 from 2008. I had a quick search on the CTC site but couldn't find it. This review is for a 55 cm frame (the smaller of your two candidates) and the head angle is measured at 72.0 degrees.
I've spent time looking at this frame in the past, but was put off by:-
1. The claimed frame weight is more than you'd expect. We discussed this at length on this forum and assuming that it really is 8-5-8 gauge we were all rather puzzled. When I got my Spa tourer 54 cm frame and fork I weighed them and found them to be about the same as the Thorn Audax! The frame on my old Dawes weighs about the same and that is mostly 9-6-9 gauge with junky chainstays, lugged construction and Dawes 'Ardaznailz' paint which is extremely thick. What's more it's a traditional design with horizontal top tube. I was so puzzled I phoned SJS and asked if they had weighed the frame with the (included) seatpost fitted but they said they hadn't!
2. The steel fork seems to be more like a touring bike fork in weight. The 531c fork blades on my Dawes Audax are lighter after allowing for the difference in steerer (my Dawes is an old one with a quill stem). To get a fork more like mine I'd need to buy the mega expensive 853 fork at £200+
3. Compared with Spa's Audax it seems expensive.
Having said all that I'm sure that the steel forked version has bigger clearances than the carbon forked Spa bike. Don't know about the steel forked Spa - the Thorn and Spa steel forks both weigh about 1.1 kg I think.
I did come to the conclusion that the 570 (med/large) frame would suit me best. My Spa tourer is size 54. Is your Spa tourer a 54?
Networkman, interesting about your sizing conclusion being like mine and thanks for the 72 degree head angle. The fork is interesting as I have a compatible carbon fork on my current frame. I may discuss with thorn a fork swap so not needing 270 quid extra but we'll see. Mind you it only saves 200g!
I was initially put off by the weight but I'm not a light man so not really fussed!
Cheers
Chris
"Marriage is a wonderful invention; but then again so is the bicycle puncture repair kit." - Billy Connolly
fatboy wrote:Networkman, interesting about your sizing conclusion being like mine and thanks for the 72 degree head angle. The fork is interesting as I have a compatible carbon fork on my current frame. I may discuss with thorn a fork swap so not needing 270 quid extra but we'll see. Mind you it only saves 200g!
I was initially put off by the weight but I'm not a light man so not really fussed!
Cheers
Chris
It's not so much the weight of the fork but the possible lack of spring. While there are debates about the importance of frame flexibility most people seem to think that a light springy fork does make a difference with narrow tyres at high(ish) pressure. On the sizing, I'm about 5' 10" or 5' 11" but have long legs and short body. On the 54 cm tourer I have a 9 cm non-sloping stem. On my rebuilt Dawes Audax I have an 8 cm stem. From what you say you are likely the opposite (longer body, shorter legs).
I've got the 853 fork on a Thorn Club Tour Mk IV that I bought secondhand, no way would I have spent £270 if I'd been buying new. I presume the fork weighs less than an equivalent 531 fork but my impression is that it gives a harsher ride.
I built the bike up with two different wheelsets, as a lightweight tourer come gravel bike with Mavic A319 wheels or an audax style fast road bike with Open Pro's. The lightweight wheels, are shared with another bike with a 531 fork, albeit with a 1”threaded steerer. With similar rubber, 25 or 28mm slick tyres, the 531 fork gives a more comfortable ride.
If you go for the Thorn Audax frame I reckon you could get a decent 531 fork custom made and still have change from your £270.
Norman H wrote:I've got the 853 fork on a Thorn Club Tour Mk IV that I bought secondhand, no way would I have spent £270 if I'd been buying new. I presume the fork weighs less than an equivalent 531 fork but my impression is that it gives a harsher ride.
I built the bike up with two different wheelsets, as a lightweight tourer come gravel bike with Mavic A319 wheels or an audax style fast road bike with Open Pro's. The lightweight wheels, are shared with another bike with a 531 fork, albeit with a 1”threaded steerer. With similar rubber, 25 or 28mm slick tyres, the 531 fork gives a more comfortable ride.
If you go for the Thorn Audax frame I reckon you could get a decent 531 fork custom made and still have change from your £270.
I weighed and calculated that the blades were about the same weight as my 531c ones which have a minimum wall thickness of 0.5 mm. I don't think such light steel forks are at all common now and I don't think Reynolds are still making the 531c blades. My old Dawes Horizon has a 531ST fork which is heavier than the 531c one; not all 531 forks are the same. Pretty sure Thorn say that their 853 blades are specially made for them. I'm surprised they sell enough for that at £270 each, then again perhaps that's why they cost £270 - to pay for the tooling!
I think that Brucey on here reckoned that a 1" lightweight steerer makes for a smoother ride than a modern 1-1/18" one. Perhaps another reason to hold on to my old Dawes Audax with threaded 1" steerer?
If you want a compliant steel fork, talk to Lee Cooper about a 631 fork. The taper starts quite close to the crown....but I don't think Lee will put low-rider braze-ons on 631 blades. Its quite easy to unpick Thorn's logic on head angles for the Audax-type bikes. Anything they will supply with a carbon fork is most likely to have 72 deg head, because that suits the "standard" 45mm offset of carbon forks. The problem of getting good toe clearance without too long a reach (to the bars) comes in the small sizes. The smallest bikes they will supply with carbon forks could be 71.5 deg head, because most folk won't tell the difference of half a degree. But smaller than that you will find bikes that only come with steel forks, and if you search diligently you can find the offset for the different forks. 55m offset (or thereabouts) suits a head angle of 71 degrees....this gives about 20mm shorter top tube for the same front centre....10mm for the extra offset, and about the same for the extra slope. ....unless its all changed since I last looked at the Technicolour website!
I’m 5’ 11” and ride a 550 thorn audax. I’ve also got the 853 fork.
Regarding frame weight, I’d say the thorn is carrying about an extra kilo against a comparable audax frame and carbon fork. I think it’s more of a light specified tourer compared to a light audax. I’ve happily toured on mine with about 10kg of luggage...
With the forks I have it takes 28mm with guards and I find the ride comfortable and the forks are rather nice. I didn’t buy them though, it was a birthday present.
It’s stable. I’ve coasted downhill from Princetown at 40mph with panniers and a bar bag and been able to take hands off the bar.
It flexes if you put too much power through the bottom bracket. If I stand up and honk up a steep hill I can get the gears to make a noise.
Finally, in blue, it looks brilliant.
Basically it’s a good light tourer. If all you’re going to do is ride it unloaded I’d say there are better bikes.
honesty wrote: Basically it’s a good light tourer. If all you’re going to do is ride it unloaded I’d say there are better bikes.
Unless it's been mentioned above, Thorn's Audax has a rear drop-out of 132.5 making it possible to use heavier 135 wheels and thus pointing perhaps at more rugged use. Spa's touer OTOH also has a rear drop out of 132.5 making it possible to use lighter 130 wheels. Of course the beauty of it is that you could own both bikes and just swap the wheels over ...
But the moral of the story is that yes, the Thorn Audax and the Spa Tourer must surely be able to be classed as very similar bikes. I do like that - it implies lots of flexibility (of the right sort) in two very capable bikes.
When the pestilence strikes from the East, go far and breathe the cold air deeply. Ignore the sage, stay not indoors. Ho Ri Zon 12th Century Chinese philosopher
I went to see them recently. They spent a couple of hours fitting me up for a nomad. The angles and frame size were two of the things we discussed and they were willing to let me choose between two frame sizes and a slightly more relaxed angle than their standard. I went back a couple of weeks later for a trial run on one of their rohloff bikes. So if it's at all possible I'd recommend a visit.
I am still undecided. I'm going to tour my old bike in September and then make my mind up. It was really nice to ride a steel bike again but the weight and cash is putting me off slightly. I need to figure out whether I need a t Usher bike next summer or if I can tweak my old bike enough. Wheels are my real concern.
