Frame Size and Crank Length.

[nigelsbicyclejourneys.com]

Hi,

I'm in the process in the next few months of purchasing a Thorn Sherpa frame. Then commencing a bike build. My previous bike build can be found here.

http://nigelsbicyclejourneys.com/the-bike/rebuild-part-ii/

I'm 5' 11" (180 cm) so this will give me a frame 565L. The Thorn documents says a 175 mm crank would be a good size. Now I've researched many a site and have found very different crank lengths recommended with plenty of formulas for an inside leg of 83 cm.

I had been running a 175 crank before with no problems. Loaded touring bike up BIG hills round New Zealand. But after probably too much research to spin up hills, perhaps a 170 crank may be better    

Any ideas or as they say if it's not broken don't fix it!

Nigel

[Danneaux]

Hi Nigel!

Congratulations on moving toward a decision to purchase a Thorn frame. You've surely setup your Orange P7 nicely, and I can see how a Sherpa might well address your needs.

As another set of data points, I am the same height as you, and with average proportions. I've owned a 560S Sherpa Mk2 and now a 590M Nomad Mk2 -- both with the shortest available top tube to better accommodate my preference for drop handlebars.

The Nomad's sizing is likely closer to that of the current Sherpa Mk3, so you may wish to see my rationale for choosing the 590M here: http://www.thorncycles.co.uk/forums/index.php?topic=4523.msg22073#msg22073 I could have fit the 565M or the 590M (again, the shorter top tube for drop 'bars; your needs may well differ wrt TT length), but chose the larger size to avoid excess amounts of seat post and steerer showing above the frame. I'm pleased with my choice of the larger size and have plenty of standover clearance for use on logging roads and fire trails (the shorter TT frames have steeper slopes to the TT). The larger frame had slightly lower load capacity at the limits, but I am really pleased with my choice, especially where I prefer the tops of my drop handlebars to ride level with the top of my saddle. Andy Blance very kindly advised me as to size and confirmed I *could* have fit either size, but would likely be happier with the larger. His conclusions matched my own and I have been very pleased with the sizing.

For reference, my Sherpa is detailed here: http://www.thorncycles.co.uk/forums/index.php?topic=3896.0

Through proper frame sizing and adjustments in stem length and seatpost layback, both the Sherpa and Nomad's hard points are identical to those of my other bicycles, so I was able to duplicate my fit exactly across all my bikes.

Coming to both the Sherpa and Nomad from tourers based on 700C-wheeled road bikes, I stayed with the 170mm cranks that have always suited my light, fast pedaling cadence of 110-120RPM. I find longer arms result in too much knee articulation to spin as easily, and shorter cranks result in less torque being applied to the drivetrain. The 170mm arms have been the "just right" solution for me. "Mashers" (those who ride at lower pedaling cadences) are typically happier with proportionally longer crankarms for their size, while smaller riders do better with shorter arms.

There's a lot to recommend staying with what is already proven to work for your needs, *especially* on a new bike where everything else is otherwise a bit unfamiliar. On the other hand, sometimes it helps to plunge into the deep end of the pool and go "all new" on a fresh bike so you have a clean slate and can try new things at once.

I hope something in the above will be helpful to you in making a choice best suited to your own needs.

Best,

Dan.

[sdg_77]

Nigel - I am the same height and inside leg proportions as you and after probably far too much research .... settled on a 560S Sherpa mk2 with 170mm cranks.  Like Dan, I prefer dropped bars.  My road bike (Cannondale Synapse) has 175mm cranks and although I don't notice a huge difference in pedalling, I do find the Sherpa is my most comfortable bike and have no regrets from buying it.

hope that helps
Steve

[il padrone]

Don't sweat over it mate. I use 170mm cranks on my road bike, but 175mm cranks on the Thorn Nomad, my dual-suspension MTB and tandem. I think the single-speed has 170mm cranks. I don't really notice any particular performance difference.

[mickeg]

My general opinion on crank length is to go for the longest crank that will not cause any knee problems.  That said, if you like to spin at an unusually high cadence, then you may prefer a shorter crank. 

I am a bit taller at 6 foot, half inch, so my data is not comparable.  I am running 175mm cranks on my bikes.  I usually use a cadence of 72 to 81 on my Rohloff bike, on my derailleur bikes with closer gear spacing my cadence is usually 72 to 78.

[nigelsbicyclejourneys.com]

OMG guys that's all fantastic info

As Dan says 'steerer showing above the frame'. The one thing I've noticed on some bikes is a lot of steerer above the frame. This I'd like to reduce, but will also include a T-Bar for a bar bag.

I'll be running a flat bar system as my previous build with myself coming from a MTB back ground. Never got on with drop bars even as a kid. I used to then turn them up!

I tend to be more of a spinner than a masher. So a 170 crank might bode well?

I did have to replace my worn cassette/chainrings/chain in Nelson NZ. Weight and lots of hills does that! I replaced my cassette from a 34T to a 36T (22T front small). What a difference. Felt like I gained another leg when needed. Not cheap, but soon worth it.

I hope to contact Andy in due course to get his final ideas on frame size 565L or a 600L.

Looking at the XT M770 Hollow II Tech as a new chainset. Now, I'm coming from the tried and tested spindle, so how is this new system holding up for loaded touring?

Thank you.

ps. Enjoyed the various photos. Gives one ideas  

[Danneaux]

Hi Nigel!

I made some comments regarding service life of the Shimano external BB here:
http://thorncyclesforum.co.uk/index.php?topic=4523.msg22073#msg22073
...here: http://thorncyclesforum.co.uk/index.php?topic=4523.msg43173#msg43173
...and the result here: http://thorncyclesforum.co.uk/index.php?topic=4523.msg43281#msg43281
...and here: http://thorncyclesforum.co.uk/index.php?topic=4523.msg43285#msg43285

I still think the external bearing bottom bracket (and Shimano's implementation of it) is a terrific idea. Unfortunately, it often seems to be let down by the sealing and quality of the external bearings, which ride in relatively soft alu cups and are few in number and not altogether well sealed from weather in my experience. From what I can see of others' experience, getting the preload a bit too tight *really* chews them up quickly. Get that right (really, only tight enough to *just* remove any wobble) and I've found the bearings last a good while in most benign conditions, but not as long as most square-taper, 3-piece, internal BB cartridges with shielded bearings.

For ultimately greater service life with original bearings, I'd suggest staying with the internal, square-taper BB. However, the OBB (external) crankset has some advantages and can be relied upon for much greater service life if it is adjusted properly on installation and especially if one purchases aftermarket bearing/cup sets -- at least in my experience and that of others on various fora about the 'Net.

So long as the integrated right arm/spindle is not damaged by bearing failure, then replacement OEM bearing/cup assemblies are available inexpensively at replacement time (or one could pack a spare pair on a very long tour), and it is even possible to press aftermarket bearings into the original cups. Another alternative that is remarkably long-lasting is the RaceFace external bearing/cup assemblies, which are lubed with Phil Wood waterproof grease and have better seals.

As for me, I found what appears to be the ultimate solution in a Phil Wood Outboard Bearing bottom bracket, as described in the last couple links above.

I do like the stiff feel of the Deore OBB crankset, and the arms are listed as cold-forged (lightweight, they have hollow, c-section arms) and the lot can be serviced or even removed with a 5mm allen wrench. I liked mine on the Sherpa well enough to spec it again on the Nomad.

Hope this helps.

Best,

Dan.

[nigelsbicyclejourneys.com]

Dan,

Many thanks for the great links.

I'll expect to go with the XT OBB Hollow techs. Nice to try something new. Will then replace the OBB when worn out with the other Guzzi kit ie. Phil Wood, Race Face etc.

Who'd you recommend for selling Phil Woods here?

Nigel

[Danneaux]

Hi Nigel!

I'm not sure if it will help or not given the cost of overseas shipping, but I got my Phil Wood OBB at a good price here in the US from:
http://www.aspirevelotech.com/Merchant2/merchant.mvc?Screen=PROD&Store_Code=AVT&Product_Code=BOSBI&Category_Code=PW-OUTBOARD-BB

Aspire Velotech has specials from time to time and I paid USD$105.50 + $6.33 (actual postage charged; they do international shipping pretty reasonably too). Thinking...USD$105.50 is NZD$128.99 or GBP£66.15 or €79.10, so more reasonable than some I've seen advertised overseas and perhaps enough savings to make up for shipping? I'd suggest checking Aspire Velotech's shipping first, as US retailers are notorious for waaay overcharging for shipping to Australia and New Zealand.

Please note: If you go with Phil, you'll need to either save your old spacers or get some new ones. I picked up some black-anodized alu spacers inexpensively off eBay and found them to be very high quality -- better than the plastic Shimano originals.

Hopefully, the Phil OBB unit will be long-lived in my use. I own several of their internal BBs, hubs, and even a pair of their old platform pedals dating from 1980-1985 and most have well in excess of 30,000 mi/48,280km and are running without excess play and even more smoothly than new. I looked seriously at Chris King since they're made in Portland, just up the Willamette Valley from Eugene. They look good but don't seem to do nearly as well as the Phil units in long-term reviews at the MTBR site: http://www.mtbr.com/reviewscrx.aspx A review here: http://road.cc/content/news/12159-phil-woods-obb-bottom-bracket-designed-british-conditions-mind%E2%80%A6-thats-wet

I really believe excess preload in initial adjustment is what kills the Shimano units fastest. Get that detail down and you'll likely get some reasonable mileage on the originals unless exposed to water or their number comes up. Do check radial and axial play from time to time and listen for "crunching" noises or clicks from the BB bearings so you don't end up like my Dutch pal with the bearings eating into the spindle, requiring an entire crankset replacement.

Hope offer an alternative as well.

Best,

Dan.

[honesty]

Im 179cm (5' 10.5") and Im using 175mm cranks on both my bikes. I'm using them because the first bike I got had that length on it, and when I built my audax I just matched the length. I'm not sure how much difference 5mm is going to make given that I can just have thicker soled shoes and my feet would be transcribing a smaller circle anyway...

My cycling style by the way is to sit in the saddle rather than stand up on hills and keep a steady cadence of around 85 ish.

Edit: also to say on Hollowtech BB's, they are great but I've got a Hope BB with ceramic bearing to extend the life of the BB. Its been fit and forget since I put it on.

[nigelsbicyclejourneys.com]

Hope; I'll also check out for the future.

Dan, I think I noticed you said somewhere you used the standard Deore V brakes over perhaps the XT version? Something about arms/levers/pivots???

Also any experience between to XT trekking V brake levers over the Deore??

Cheers,

Nigel

[Danneaux]

Dan, I think I noticed you said somewhere you used the standard Deore V brakes over perhaps the XT version? Something about arms/levers/pivots???

Yep. Nigel, I prefer and deliberately chose plain Deore v-brakes over the older-style XT versions with the parallelogram linkage Shimano called "Parallel-Push". In my own experience over time, the parallelogram links became a source of wobble and squeal, while the plain versions proved longer-lived in my use and that of friends who tried them. Shimano seem to have agreed, since they have redesigned the XTs so they no longer have the "parallel-push" mechanism and now just have plain arms like my Deores.

Andy Blance and I respectfully disagree on this one, and I think it comes down to what (has) worked best for each of us in use. Certainly, others seem to have been happy with the older-style parallel-push linkage, but it did not work as well for me in my use. The idea behind the parallelogram was to keep the brake pads hitting the rim sides squarely as the pads wore. This they did, but (in my experience) at the cost of wear in the pivots over time. In contrast, the standard arms do allow the pads to wear less evenly (vertically) unless the rider intervenes, but if you are careful in your initial setup and use Kool-Stop Salmon pads (as I do, to maximize wet braking and minimize rim wear on non-CSS rims), the adjustment intervals can be very long indeed.

Please note, if you have your heart set on the older style XT v-brakes with parallelogram linkage, they are still available for reasonable prices on eBay, often in NOS condition. They are also very pretty, at least to my eyes.

As an aside, having installed many Shimano v-brakes, I have yet to find any with balanced native spring tension. What I do first is to back the tension adjustment screws out evenly on each side then manually adjust (gently bend) the linear springs outward so the tension on both arms is equal and the pads are equidistant from the rim sides. Then, I set the tension adjustment screws on each arm, which makes for a finer adjustment on spring tension than setting the spring pins in different holes on the brake bosses. I mentioned this to a Shimano rep at a MTB race and he agreed this was the method he used as well.

As a trivia note, the cable tension on v-brakes is approximately half that of conventional cantilevers, thanks to the geometry. This reduces cable housing liner wear as a happy byproduct.

Hope this helps.

Best,

Dan. (...who in general likes v-brakes very much)

[mickeg]

Dan,

Thanks for your comment on bending the springs to equalize the spring tension on each side.  I may have to do that after-the-fact on some of my brakes.  I had not thought bending the springs to be practical so had not tried it.  On one set of brakes I had to buy longer screws to be able to adjust them correctly.

[nigelsbicyclejourneys.com]

Top response  

'Shimano seem to have agreed, since they have redesigned the XTs so they no longer have the "parallel-push" mechanism and now just have plain arms like my Deores'

Yes, the new XT's are also nice, but I'll probably go with the standard Deore unless I find a black pair of XT's! Has to be Black!

Looking at them both can't see what the difference is though?

Thanks for the heads up on Kool-Stop Salmon pads.

Also much of a difference between Shimano Deore T610 brake levers and the XT T780. Both seemed to be classed as 'Trekking'?

Nigel

[Danneaux]

Also much of a difference between Shimano Deore T610 brake levers and the XT T780. Both seemed to be classed as 'Trekking'?

Nigel, I can't speak to the merits of these from firsthand experience, as I went with a drop-bar spec on my Nomad and Sherpa (Tektro RL520 Aero V brake levers and Tektro 740 "interrupter" brake levers [black w/red QR]).

Best,

Dan. (...who also likes monochromatic, all-black bikes)