Thorn Forum Member Frame-size Registry: Who fits what

[jags]

funny i often thought if the house god forbit went up in flames what would i grab first and  my bikes and guitar were top of the list 
my 300 plus albums vinal are in the attic so hopefull the houst would be saved before it got that far.
man bad thoughts must not think of these things bad karma.

[alfie1952]

  Just noticed this, so I have done the necessary measuring.

I am 5' 9 1/2 (177cm).
Inside leg measurement is 31 1/2 (80 cm in stocking soles)

Bike is a Thorn Sherpa 560s.(Black)
Flat bars with Ergon grips and bar ends.(I also have Humpert trekking bars which I may change to)
Brooks Flyer (black).
Thomson stem 100mm with 15 degree rise on uncut steerer.

Hoping to add photographs shortly.

Regards, Alfie

[Danneaux]

Aww, sounds like a beauty, Alfie. In my favorite size as well! Looking forward to seeing those pics in the gallery.

Best,

Dan.

[joesoap]

Hi, I am 5ft. 7"  ( 170cm ) tall and ride an XTC 525 S. I have a Velo orange Grand Cru seatpost with 3omm layback and Nitto Noodle drop bars on a short 60mm stem (c to c )
  My Brooks B17 Ti. is shoved back as far as it will go and this position is just fine for me. However, I have always wondered if perhaps the 525 'L' version of the frame would be better for me.
   I believe that it has a top tube 1" longer than mine. I am thinking that perhaps my seat would not have to be so far back, or would I have exactly the same seatpost / crank arrangement and just a longer reach to the bars?
  I seem to fit my arrangement very comfortably and I can drop a plumb line from my knee to bisect the pedal spindle exactly. I can't help thinking that my saddle looks kind of odd so far back.
  Any ideas? regards, Joe
P.S. I can illustrate with photo if necessary....

[horizon]

  My Brooks B17 Ti. is shoved back as far as it will go and this position is just fine for me. However, I have always wondered if perhaps the 525 'L' version of the frame would be better for me.
   I believe that it has a top tube 1" longer than mine. I am thinking that perhaps my seat would not have to be so far back, or would I have exactly the same seatpost / crank arrangement and just a longer reach to the bars?
  I seem to fit my arrangement very comfortably and I can drop a plumb line from my knee to bisect the pedal spindle exactly. I can't help thinking that my saddle looks kind of odd so far back.
  

Try to get a definitive answer to this. As bikes get bigger or smaller the top tube increases or shortens in length behind the BB - it's cycling's best kept secret. Thorns are different in that the top tube lengthens or shortens on the same basic frame size (say 565 S or 565 L). AFAIK there is some difference in "reach" (however you measure it) i.e. the change in top tube length also occurs forward of the BB. But even Thorn are subject to the laws of geometry and any major change to shorten the TT length forward of the BB will create toe overlap. For this reason the reach is shortened by changing the stem length, not the TT length. Your saddle looks "kind of odd" so far back because the seat tube is steep - stay with your comfortable position, it's priceless. Make changes based on stem length but not on your saddle position.  

[joesoap]

Thanks for replying. Do you mean that a 525l has the same angle of seat tube, that the longer top tube is achieved wholly forward of the B.B?

[JWestland]

I have a 525L but I am 5"5'...it's too long for me. I adjusted with a shorter stem, namely 6 cm. I would much prefer a 490S/525S as it's still slightly too long.

Pushing saddle back gives you about 2 cm more TT, making is 54.5 cm ish but..it does change the angles as you noted.
The 525L has a virtual top tube of 55.5 cm. So if you push the saddle forwards you can put 2 cm on the stem (giving you the 2 more reach you need), a 525L *may* suit if you feel your current reach is still short.

http://web.archive.org/web/20081122163416/http://www.thorncycles.co.uk/thornpdf/ThornxTc853BroLoRes.pdf

has all the geometry in it, that may answer your questions

[horizon]

Thanks for replying. Do you mean that a 525l has the same angle of seat tube, that the longer top tube is achieved wholly forward of the B.B?

Without more dimensions I cannot say. Looking at the 565 Sherpa, there is a difference of 4 cm in the top tube between S and L. Some of this is accounted for by the seat tube angle but it cannot be all. Furthermore, Thorn recommend a different fork offset for each size: this can only be needed if the head tube has moved back towards the saddle and there is now danger of toe overlap. I would have to check with Thorn what the relevant figures are for TT length forward of the BB for S and L.   

[Blue lotus]

I own a Thorn Sherpa mk2 560XL, I measure 6'1'' (1m85), my trousers are 36waist*34leg (never measured it otherwise).

I've a very short Thorn stem (Thorn Front Loading Alloy 1 1/8" Ahead Stem +40 Deg Satin Black - 90mm). Accessory bar at the front, front and rear rack, Modolo Yuma Mohican handlebars (very good two position bar, upper relaxed one, and more racey one with brakes).

Picture to follow by the end of the week.

Cheers,

[RobertL]

RST 586L Flat bar 1.78 m 170mm crank

San Marco Rolls and Saints pedals

Initially thought this might be a bit of a stretch, but am now very happy with the fit. The bar was turned to make way for a zip roll, ideally I would like the bar back in its lower position, but too lazy to see if the zip roll would fit.