BLOG "El Burro" Granite Tandem Design spec

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1	BLOG Bike packing tandem "El Burro"
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4	category	Item/ Brand	Specification	Basis of decision/selection	grams	Link
5	frame	Granite Tandem Design	Granite Tandem Design Gravelleur, titanium uncoupled frame	target 35#, $10,000 project specifically addressing bike-packing needs. 29x2.3 and 27.5x3 tires for terrain we've found most prevalent.	3468
6			427 axle to crown, 65mm offset fork. for 100x15 thru axle 73-degrees head angle and 65mm rake for 45mm trail	Our riding does OK with flex ti fork and no front suspension, allowing us to have a reduced axle-to-crown (AC) height, maintain standover height without a bent top tube. We opt not to have suspension for weight and to avoid the high center of gravity geomery of a mtn tandem. The tire size and pressure services us well enough for rough forest service roads.
7			148 rear spacing	Initially thinking was to match our racing gravel tandem wheel set to have interchangable sets, but the racing tandem is 135mm QR. So we decided a new set of wheels and 148 x 12mm thru bolt was best
8			captain top tube 58.3cm (5mm longer than our racing frame)	to provide toe clearance on bigger tires
9			50mm BB drop	not a monster truck geometry of a mountain tandem with zero BB drop. Instead opted for a lower center of gravity serves us for gravel conditions
10			Stoker seat tube approx 400mm to accommodate 210mm stack height for Ergon CF3 flex seat post and seat.	Ergon does not publish stack height, I had to get one to measure it. Considered the Body Float which is a little heavy for our needs but might be nice. I notice riders with them bob up and down with every pedal stroke: maybe they don't have the right weight spring or preload.
11			rear BB shell 86.5mm wide for BB386 EVO standard, offers largest area for welding chainstays	David Lafferty at Granite Tandem's idea that allows better chain stay welding for wide tires, while still working with desired road cranks.
12			10 bottle mounts (2 bolts each bottle) 4 of which are for use when bags are not mounted. 12 singular bolts at frame bag mounts in addition to using bottle bolts for some bags. 4 fender/rack mount bolts on stays Bevy of thought thru cable guides and a pass thru top tube for RD housing	Included "side-by-side" mounts on top tube 45 degrees off top of tube since the frame would be filled with frame bags. We found since the bottles face a llittle "downhill" a short loop of elastic cord from the cage around the nozzel of the bottle was needed to hold them in place over bad waashboard. We knew from the bags on our first gravel tandem that we could take a differnt approach with a large bag set just to the top of the timing chain, and then use tool bottles for the lowest position adjacent the chain, would result in enough bag for packing without the need for a large "stoker stem" bag, so the option for more bottles in this position was possible. Worked with JPak on frame bolted bags
13		Headset	Headset with 1.125/1.5 races, external cane creek 110: ZS44/28.6/EC44/40 12mm stack height	opted for Cane Creek 110 series upgrade over their 40 series affordable option	92
14		fork	blacksheep Purpose built Titanium tandem duty, 427AC, 65mm take, (2) bottle mounts, and (2) anything mounts, paragon tapered steerer, ISO mount disc brake, 100x15 thru axle, includes thru axle from DT Swiss, Steerer 250mm. http://www.blacksheepbikes.com/	Prior gravel tandem we tried a 70mm offset ti fork and found it very stable, and the ti flex performed well on washboard	1000
15	Controls
16		Captan stem	100MM redshift SHOCKSTOP STEM	heard good things, 100g premium over thompson. I left it set rather soft, I am sure it's doing work but still feesl bumpy. On 2 week trip my arms did hold up better than last year without it	260
17		cap nut and ti bolt	carbon/Ti		15
18		steerer tube spacer	Carbon. About 60mm of stack depending on the stem width and angle. At a minimum (3) x 5mm, (3) x 10mm. Measure frame to see how much we need		10
19		stoker stem	Custom ti stoker stem from Dean bikes a little over +27.2, 30 degrees, 240mm long. Alum face plate		240
20		captain Bars	Salsa Cowbell 2, 280g 46cm, 12 degree drop flare, no bottom flare. 68mm reach, 115mm drop, aero reinforced. 120mm-wide center with long slow taper about another 50mm, assume 31.8mm clamp for Eagle shifter	Wider flared bars like the woodshipper are not as well reviewed for riders who like position in the hoods. So I went with modest flared bars. I could found no better short reach shallow drop options. The 31.8mm section was not wide enough for the Paul's mounted mtn shifter so I had to make an adaptor	281
29		stoker bars	cobra wing		210
30		Bar wrap	Sew up leather bar wraps! 2mm bright blue upholstery leather with pink waxed thread done in baseball stitching	I've done leathers on a few bikes now and find they hold up really well. Difficult to apply over cables and padding	110
31		Bar Phat	cinelli time 2 for front and back		142
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33	Drive	1x12 with right side timing chain		For packing we don't need speed gears like I have on our 3x11 700% range gravel race tandem. Instead I wanted the reliability of one rear derailleur and not electronic so would persist in the backcountry. And wanted efficiency in drive train gained with right side timing chain.
34		crank rear right	SRAM Force BB30 165mm right. Discard SRAM spider. Resort with camo spider per spec below	Credit GDavid at Granite tandems for working out this drive. I just provided crank arm lengths. David spec'd cranks, found he could remove the stock spindle in the rear that's too short without having to buy a whole second set to make a left crank from a right and helicoil the pedal. He could have done so, but since the spindle removed he was able to use one set	162
35		crank rear left	SRAM Force BB30 165mm left from same set. SPindle removed and replaced with longer spindle. No helicoil required.		155
36		spindle	Cannondale 125mm spindle, which will result in a 156mm Q-factor		95
37		FIRST REAR DRIVE TRAIN GEARING 28T		Started with this but found it not low enough
38		spider rear right	Wolftooth CAMO M2 for SRAM. Spacers - custom	provides best spacing for 3.0 tires, drive train clears tire by 3.5mm. David at Granite worked out the right offset version to spec	36
39		rear chainring bolts and nut	(5) M5 x 16mm SHCS, M5 Nylok nuts, custom M5 spacers. All stainless. Because the outside mounted 38t chainring does not "plug in" to the camo spider, the chain ring bolts should be stainless steel, not alum	Camo spider not made for this application to have rings both inside and outtside of spider, but thru bolts worked	23
40		rear Drive chainring	28t, Wolf Tooth CAMO narrow-wide stainless @ 49mm chain line	This is the smallest steel narrow-wide chainring I could find. Blogs told me that alum rings 30 or smaller were lasting under 1000 miles on single mtn bikes.	62
41		Rear Timing chain ring	Wolf Tooth CAMO 38t @ 56mm chainline in rear, on outside of spider with extended bolt length thru camo spider and nuts. Chain clears 2.875 x 27.5 tire by 3.5mm	To reduce bottom tube bending and thus improve efficient power transfer from the captain, a larger timing chainring makes a big difference and we don't need more clearance for rocks since we're not jumping logs. Also worked hard to keep the timing chainlnie close to the frame center. The front timing chainring is even closer than the back that does help with no need for the line to be dead straight	65
42		SECOND REAR DRIVE TRAIN GEARING 26T		We needed this low gear. On every day of our 2-week bike-packing trip we had a use for this gear loaded on steep climbs
43		spider rear right	North Shore Billet 64/104, inner ring spaced with an additional .75mm washer to allow drive chain when it's in the largest cog in back to clear timing chain		66
44		rear chainring bolts and nut	(4) chainring bolts		20
45		rear Drive chainring	26t stamped steel 64bcd @ 47.5mm chainline (smaller ring needs more spacers to clear timing chain than does the 28t chainring in option 1. Chain clears 2.875 x 27.5 tire by 2mm	I wish I would find a narrow-wide 26t, 64bcd in steel or stainless steel	65
46		Rear Timing chain ring	38t SRAM Road C-Ring 38T 2X11-Speed Black 104BCD Chainring @ 56mm timing chainline in rear	See above about 38T selection	85
47		Front crank	SRAM Force, single road crankset right and left 170mm length, replace spider BB30 standard, road spindle		438
48		Front crank spider	Camo for SRAM, M8 44mm chainline Alternate: SRAM 110bcd spider for non-Camo chainring	Tighter chainline in front than in back does help reduce bottom tube bending and thus efficiency of captain power transfer. See below for clocking issues with the captain and stroker cranks using narrow-wide chainrings	36
49		front chainring bolts	alum for camo		5
50		Front Timing chain ring	Wolf Tooth narrow/wide 0 offset for SRAM 38t. Alternate: non-camo 110bcd 38t chainring to align the cranks.	Turns out the 724mm belt-length bottom tube length and Camo spider having only one position for the chainring (it can not be rotated around to any other of the 5 bolt positions) that the captain's crank leads the stoker by 1 chain link (10 degrees). The narrow wide chainring only allows chain to jump 2 links so either 10 degrees ahead or 10 degrees behind. This the alternate non-camo spider and non-narrow-wide chainring to alow clocking the capt and stoker cranks to align. If you didn't want an option for a belt, the bottom tube could be shanged a few mm eaither way and make cranks work.	63
52		Eagle 12
53		cassette	X01 - XG-1295 Eagle 10-50 XD Driver low gear 0.52 vs 0.52 on coyote with 2.1 tires Confirm effective gearing diam of 2.3 vs 2.1 tire 586g for sunrace cassette	The XX1 and X01 are both 355g, the GX is 450g, so I opted for the expense of the X01 to save weight	357
54		RD	GX Eagle	GX same weight as X01 and XX1	290
55		Trigger shifter	GX Eagle, replace "Matchmaker" clamp with Paul clamp	GX same weight as X01 and XX1	124
56		trigger mount	31.8 trigger shifter mount adaptor by Paul Corp	31.8mm center section of bars were not wide enough so I used pieces of Problem Solvers seat post shims to mount Paul onto narrower section of bars	20
57		12 speed chain	GX Eagle	GX same weight as X01 and XX1	260
58		backup cassette	for 27.5 wheels, SunRace MZ90 12‑speed Cassette 11‑50 with standard not XD Driver Cassette, 526g, $115	Most touring is on 29 wheels, 27.5 are for local sandy rides. I opted for budget hubs and casette
59		shift cable and housing	4mm Jagwire Pro compressionless LEX-SL, only sold as kit... 2300mm cable appears just long enough for tandem Discontinuous housing, see routing diagrams		74
60	Timing	rear BB	386EVO Angular Contact BB for 30mm Cranks		91
61		eccentric	Proprietary Granite Tandem Design similar to State Bikes eccentric, includes press fit BB bearings	lighter than bushnell feather weight	170
62		timing chain	two thus: 11 speed, KMC X11-SL	Needed narrow 11spd to help right timing and right drive chain clearance.	314
63		see "drive" above for chain rings
64	Braking	brake levers	Use Campy Record 10 short pull	Get to use cool vintage levers. And I've always liked the grip fit of Campy levers	215
65		rear	TRP HY/RD post mount	Found the hydraulic reservoir reasonably adjusts for pad centering and wear. The latest set seems to adjust a little less than ideal and take cable adjustment as pads wear.	195
66		front	TRP HY/RD post mount		195
67		rear rotor	Magura storm 203	started with Disco floating rotor thinking the float would help with heat and warping, but they seems to shed particles into resin pads and wear poorly	175
68		front rotor	Magura storm SL 203		177
69		rear caliper mounts	frame is 203 post mount, no adaptor	Needs 1 to 2mm washers to center pads in rotor
70		front caliper bolt/shims	shimano 185-203 post to ISO mount	Needs 1 to 2mm washers to center pads in rotor	26
71		ti caliper bolts	M6x20mm (6) ti bolts for caliper and adaptor mounting.		30
72		ti rotor bolts	(12) titanium		15
73		cables and housing	5mm Jagwire Pro compressionless KEB-SL, road brake ends 2800mm rear cable is long enough. Front is continuous housing, rear is discontinuous but housed everywhere lower than the top tube		150
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75	Wheels	29 wheels	29er wheels, see separate work sheet		1950
76		front	Onyx 36h, nextie 29AS33, asymmetric with optional reinforcing, 27mm internal rim, 100x15 included with fork	Studied largest dia spoke flange specs for front and back which helps build strength	65
77		rear	White Industries 36h, 148x12, XD Driver, ISO 6 bolt, 36h. Nextie NXT29AS32 25mm internal width, asymmetric by 2.6mm. Thru axle DT Swiss RWS 173.7mm for 148x12x1.0P, flat washer	ordered rims when I thought the whiles might interchange with gravel racing tandem which limited the rim width	73
78		tire: front 29x2.3	For 15% tire drop 360# weight on 2.3 = 42psi, on loaded 400lb 2.3 = 47psi	In spite of calculated pressure for 15% tire drop, we found running at 35-37psi was appropriate for rough trails and washboard
79			cross mark II 2.25 exo (59mm or 2.3" actual width, 364.mm actual radius with 15% deflection)	good solid center bead for mixed terrain	780
80		tire rear 29x2.3	minion SS 29x2.3	semi slick with good grip on edges. Have had one tire ruber delaminate from the housing	780
81		27.5 x 3 wheels	27.5 wheels, see separate worksheet, deore XT 32h hubs, Nextie NXT27AM40, 33mm internal width, 1808g. Backup cassette is above in drive section	rim no longer available changed to different product.
82		tire front and rear 27.5 x 3	For 15% tire drop at 360# 27.5x2.875 = 31.4 psi. For loaded 400lb, 2.875 = 33psi	we've used them a little and have started at 32psi
83			WTB ranger is nice and tight tread compared to buldozer, actual on spec'd rims = 73mm at casing 76.5mm (3" exactly) at knobs (on 33mm ID rim) and 357.5mm Radius with 15% deflection, withint 7mm of 29x2.3 tires. 835g light, 1080g tough	measure 2.875" when mounted
84	seating	front seat post	Thompson masterpiece 27.5		200
85		rear set post	Ergon CF3 pro carbon (not the chinese knock off) Only available in 27.2 dia vs 31.8 frame in rear	220mm stack height from seat top to max insertion not stated, I had to measure after ordering	230
86		front shims	27.2 to 28.6 shim		10
87		rear shims	27.2 to 31.6 shim		10
88		stoker seat	respero, unisex soft. contour 411g, sportif 326g	out of production but the only seat stoker will use for 10 hours a day	400
89		captain seat	SQL, 611 size 15, considering the new "active" version Consider carbon to save 140g = SQL 611 carbon $230 150g 611 cromo $110 250g 611 active carbon $280 190g		305
90		Front seat collar	31.8 Thompson	Really should find a super hold double bolt collar	10.5
91		Rear seat collar	Built into frame		11.5
92	Pedals
93			speedplay syzr	like the easy release	624
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95	bottle cages	(9) eight	Gorilla 38g for bottom tube stoker and some of the fork carbon Salsa and king SS elsewhere		220
96		unused bolt fillers	(8) black alum		8
97		bottle bolts and bag bolts	(10) ti bolts		8
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99					34.8
100	Frame bags	bags	JPAK LLC, rear saddle bag, two frame bags, two gas tank		3.5
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