Is this right? (reach on Surly versus Thorn)

[horizon]

I've copied this over from another thread as I would really appreciate some input on it:

A bit late to this party perhaps as I think you've decided on the CT but thought I'd just say that I have previously owned a LHT which I sold as it was too long in the top tube (even after buying a smaller frame) and I currently own a thorn CT and a thorn Audax.   

I wonder if the LHT frame is really designed with flat bars in mind, or half in mind.   Most riders I've met find them a little long, if using drop bars.   

According to my current understanding that's mathematically impossible. The length of the top tube is adjusted at the rear by moving the saddle fore and aft - it's at the front where you will feel stretched out. A shorter/higher stem will deal with this unless the reach is too long. The reach on a LHT (26" and 700c) is identical to a Club Tour and Sherpa - around 39.5 cm.

The reach is the distance from a point vertically above the BB to the head tube. According to the information on the Surly website it is around 39 cm (and cannot be lower without toe overlap). We've calculated the reach for the Thorn bikes on this forum.

If anyone would care to verify this I would be very grateful.

[Erudin]

I can get exactly the same contact points setup on my Thorn Audax Mk3 525 as on my 26" LHT 52cm, they both have identical drop bars, stems and saddle. There is 1cm difference in their effective top-tube lengths.

[Slammin Sammy]

Surly lists "Effective Top Tube" lengths which are equivalent to Thorn's "Virtual Top Tube". Surly's seat tube length is centre of the BB to top of the top tube. Thorn's is C-C.

For the smallest 700c LHT (size 56), the ETT is listed as 570mm. The equivalent size Thorn CT is 580S or 580L.

LHTs are generally sold with drop bars. The shorter tube 580S would be Thorn's recommended drops model. The VTT for this frame is 560mm.

Seat tube angle is 73 deg for both bikes, so I would think that portion of the ETT or VTT to the rear of the vertical from the BB is the same (or very close) for both bikes. This would confirm that the LHT's reach is therefore 10mm longer than the CT, all other things being equal.

Contact points however, would be easily adjustable within this range (stem length and angle, seat post setback, etc).

[Far-Oeuf]

it's possible that people (me included) just don't go into enough detail.   I have a 58cm LHT, and I tried a 580S Club Tour, and they are quite different even though the stem length is very similar.   Being a lay-person, I'd treat them both as 58cm ETT (ignoring the S/L variations).   Possibly the 58cm LHT is comparable to the 580L (which is designed for flat bars)?

[Andre Jute]

it's possible that people (me included) just don't go into enough detail.

In defense of laymen, we may not always know which detail is important. It may be enough for many that Andy Blance knows.

It took me a few years to realize that as little as a few millimeters on on handlebar height and reach makes an important difference to whether I'm keen to ride the bike or whether I take my exercise as a matter of duty, a veritable gulf of motivation and consequent outcome.

(signed) The Perpetual Dilettante, and proud of it!

[horizon]

For the smallest 700c LHT (size 56), the ETT is listed as 570mm. The equivalent size Thorn CT is 580S or 580L.

I would have thought that the nearest equivalent LHT to the Thorn 580S is the 58 cm LHT. This however gives a strange reading with a difference of .5 cm in reach but 2 cm difference in ETT (after removing .5 degree angle difference which I've called .5 cm in top tube).

That's either mathematically impossible or the two bikes aren't equivalent but I don't see why not. Why did you choose the 56 cm LHT for the Club Tour 580S?

 

[Slammin Sammy]

I would have thought that the nearest equivalent LHT to the Thorn 580S is the 58 cm LHT. This however gives a strange reading with a difference of .5 cm in reach but 2 cm difference in ETT (after removing .5 degree angle difference which I've called .5 cm in top tube).

That's either mathematically impossible or the two bikes aren't equivalent but I don't see why not. Why did you choose the 56 cm LHT for the Club Tour 580S?

 

I've used seat tube length. The 56cm LHT is sized by its seat tube (centre to top). Thorn's 580 CT has a seat tube length of 55.5 (centre to centre), which is closest. The 58cm LHT would be considerably taller. I was just trying to compare two equivalent-sized models to address the reach question. The 58cm LHT would be even longer again in reach - another 16mm, or almost 3cm longer than the 580S.

I'm not using a mathematical derivation, but rather the definition of reach given by the original poster (your good self). And whilst I agree with Andre that the definition is rather abstract, it's as good as any to compare bikes when the seat tube length and angle are equal.

The effects of taking numerous alternatives to adjust one's required contact points around different frame configurations is a source of endless fascination for me. I often think I should have gone for a larger frame Nomad, as the height of the stack puts the stem uncomfortably close to my gut. (Thorn actually recommended an even smaller frame, based on the carefully measured sizing data I supplied.)

A larger frame would have made a slight difference to stand over height, which is never really a problem for me, but in hindsight I would have preferred a longer top tube and shorter stem. Same contact point distribution, but just a little more breathing room up front.

As it turned out, I use an n'lock stem which is 130mm (one length only), and this assures my riding comfort. I'm also trying to reduce the "overhang" up front, with some serious time on the bike. Another good way to add a little breathing room  !

[mickeg]

I have several bikes:
 - LHT (700c), 58cm, 80mm 10 degree stem.
 - Thorn Sherpa, 610S, 90mm 17 degree stem.
 - Thorn Nomad MkII, 590M, 90mm 35 degree stem.
 - And a few others.

All three bikes are setup about the same, all use drop bars.  When I get on one it feels the same as the next one for fit.  The only noticeable difference is that the Nomad feels taller, I think the bottom bracket is higher off of the ground.

My Brooks Conquest saddles are pushed all the way back on the seat rails on the LHT and Sherpa, but on the Nomad the saddle is maybe 20mm forward of the farthest back position.  I am unsure, but I think that the seat tube on the Nomad is a shallower angle.

I have noticeable toe overlap on the LHT, not on either Thorn.  I could probably use a 60cm LHT to reduce toe overlap (60cn has a longer wheelbase) but it is very hard to find stems shorter than 80mm that look good.

It was not until I compared all three bikes by writing this that I realized that the LHT is the smallest size based on seattube length and it also has the shortest stem.  I bought my LHT frame and fork in 2004 before they started selling complete bikes, I built it up from the frame.  (I also built up the Thorns from the frame.)  In all three cases I did a bit of experimenting with stems until I got to the ones I currently use.  I found that an adjustable stem (for angle) is very useful to have for a new bike when trying to figure out what stem you really need.

I think it is common for LHT owners to buy shorter stems than were stock if they retain drop bars.  I however do not think I have ever heard of a LHT owner swapping out a stem for a longer one.  

Also it is common for LHT owners to request an uncut steerer when they order one from a bike shop, otherwise many bike shops have cut the steerer too short.

I wanted to compare trail on the three bikes to see if that could be the source of the handling problems I had on the LHT on my last tour.  I asked Thorn for fork rake and headtube angle information on the Thorns, but they did not provide that information.  I do not have equipment with sufficient precision to make the measurements myself, so I was not able to calculate trail with sufficient accuracy.

[Far-Oeuf]

@mickeg, when I ordered-up a custom frame bag for my mountain bike I had to lay the frame on a sheet of A3 and draw around it.   Maybe that's a good way for you to measure the angles?

cheers,

[energyman]

I just put my faith, dimensions and requirements into Lisa's hands and I ended up with an RST that is a joy to ride all day (and night now I have some decent lights !)

I have been trying various styles of handlebars but am back to Thorn Comfort bars as of this morning.

[horizon]

I just put my faith, dimensions and requirements into Lisa's hands and I ended up with an RST that is a joy to ride all day (and night now I have some decent lights !)

I have been trying various styles of handlebars but am back to Thorn Comfort bars as of this morning.

I think your faith, dimensions and requirements went into the comfort bars. These obviate any problems with reach as they don't have the forward throw of drop bars. It is probably where I may end up but I am still persevering with drops until I can get no further (or nearer!) with them.