Bombadil Tire Clearance

[Chad]

I'm not sure if I have a odd duck here or not, but tire clearance on my early double top tube 650b Bombadil is really tight. With a 650b x 2.0 Quasi-Moto (actual width Is about 53mm on a Velocity Synergy rim), there is maybe 3-4mm clearance at the seat stay bridge. Enough for the tire to roll through but not much room for mud or rocks. I was thinking the Bombadil was designed to fit the quasi-Motos as there are pictures of early prototypes running around with this tire. I've also run the Schwalbe HS 315 "Fatties" (true width 47mm) and Bruce Gordon Rock n Roads (44mm), but it would be nice to fit at least a modern 27.5 x 2.1 MTB tire in there. Just wondering if anyone else here has experienced this challenge?
https://flic.kr/p/Bsyew9

[iamkeith]

I can't speak from direct experience related to the Bombadil, but maybe this helps.  

From what I understand, the bike actually preceded the tires - though not by a long timeframe.   Kirk Pacenti designed the neo moto, and then the quasi moto, directly in response to the Bombadil and some persuasive conversations he'd had with Grant.  So if you have a REALLY early model, I could understand how the clearance be minimal.  Since it was originally conceived as a bike "in the spirit of a 1985 mountain bike," and since mountain bike tires were only 1.75" wide back then, it probably made sense.   I know that later frames have increased in terms of their available clearance.  There are other images circulating of what is described as a test model, fitted with neo motos (which you've probably seen), and it does seem to have more clearance than yours - though its  hard to tell for sure.   Perhaps this was a first revision - before they did the batch of clearcoat frames?

https://www.flickr.com/photos/gzahnd/2417452065/in/photostream/

The other theory I had doesn't seem to apply to your frame:  Just like your bike, the seat-stay bridge is also the point of least clearance on my All-Rounder.  But on mine, the builder used one that was drilled for caliper brake mounting, even though the bike uses canti brakes.  In my case, I've assumed that it was (consciously or unconsciously) located where needed to provide the option of switching the brake-types, based on longest-reach brakes available at the time. But, unless I'm seeing it wrong, yours doesn't look like it is meant for that.

Even though it's tight, I personally would have no issues using it with the clearance you're showing.   I'd just avoid gumbo mud, which I try to do anyway.   If you're interested, I can post a picture of the modification I recently made to my fender, to allow it to clear the stay and still let me run an oversize tire. 

[Garth]

   I would never say that any Riv frames are designed around X tires , that's simply limiting. The clearances are like a balance between chainring sizes and the bend of the stays, chainstay length and the intention of designer. Meaning, it's all art !

   Even with a frame design , each one is unique to that particular builder so there will always be slight variances of some kind.  So your frames clearances simply are what they are.  Rivendell may design the frames and even furnish some lugs, but to have them built they are like a contractor of sorts in relationship with builders around the world, not unlike other companies.


  In regards to what iamkeith said about the early mtb's , they did come with 1.95" tires even in 1982 . My 1983 Stumpjumper Sport came with the original "Stumpumper" tires that I believe were 1.95" and when I wore them out I replaced them with Crossroads 1.95" . I used a max tire of 2.05 on it, a Vittoria Free Climb. The rims were the by todays standards "quite wide" Araya 7x which I believe were 32+mm's so the tires mounted fairly true to size. No problems with clearance . I suspect the 26x1.75 written on the Araya may have been a source of confusion as this referred to the smallest recommended tire , though I ran Tricross 1.5's on and off no problemo.

Those Stumpjumper frames were brilliant in the design of the chainstays and clearance and could have easily been reconfigured today to use wider tires and still have clearance for even "low q" triple cranks like the Sugino AT and TA Cyclotourist whihch came on the Sport($495 model) and Stumpjumper($750).  Our early Bombadils could have used a design like that ! I always considered the Bomba the fit and ride I always wished the Stumpjumpers had because they were quite bad in that way.

[Steven Sweedler]

were any of the larger Bombadil  frames  built for 700 C wheels, Thanks, Steve

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[Garth]

  Yes,Steve , the 60 and on up .  Mine has a max with fenders of about 50mm or so.

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[Jim M.]

I have a 56cm proto-Bomba. I'm running WTB Beelines tubeless, and they measure 55mm wide. These have low profile knobs and I get about 5 mm clearance at the bridge. There is only a little more clearance at the fork crown. It has been a problem in sticky mud. 

jim m

wc ca

[Leslie]

That pic was what led to me wanting a Bombadil, but, it was later on that I got one, ended up w/ the diagastay one instead (but that's another story).

For the clearance aspect:  at the time, there really weren't a lot of 650b tires... the Quasi came out while the bike was being prototyped...  http://cyclofiend.com/rbw/bombadil/

The clearance you're showing on yours, is a bit more than I'm running on my Rom...: https://www.flickr.com/photos/leslie_bright/15567948324/in/album-72157623199721925/


The later Bombas ended up w/ a lot more clearance:
https://www.flickr.com/photos/leslie_bright/6836831408/in/album-72157623199721925/
https://www.flickr.com/photos/leslie_bright/6835730758/in/album-72157623199721925/
(I can run 2.3 NeoMotos under fenders even.... not that I'd suggest such.... https://www.flickr.com/photos/leslie_bright/7150235995/in/album-72157623199721925/)

[Bill Lindsay]

I remember my rear chainstay bridge having some headroom over the Quasi Moto.  I don't have any great photos of it, and I don't own the frame anymore.  This is the best I have, but you have to use your imagination.  Mine was bought from Riv-stock in Spring of 2010.  

https://www.flickr.com/photos/45758191@N04/4521861157/

On Sunday, December 6, 2015 at 8:00:54 PM UTC-8, Chad wrote:

[ted]

Chad,

I have a first generation 52 Bombadil, and currently have Quasi-Motos mounted on Synergy rims on it.

I think they fit fine at the pressures I usually run in them (20-25psi). If I recall correctly, when I first mounted them I seriously over inflated and the resulting clearance was minimal to inadequate. I don't think I would buy 2.1 MTB tires for it, though before I bought mine I rode a demo at RBW WHQ that had (I think) a Quasi on the back and a Fire Cross (bigger knobs so fatter) on the front.

As others have noted the later Bombadils (diaga tube/stays and different crown) have more clearance. I don't know if some of the later parallel top tube versions had more clearance than the earliest ones or not. I fear if you want to use most current 27.5 MTB tires the early Bombadil may not work to work.

On Sunday, December 6, 2015 at 8:00:54 PM UTC-8, Chad wrote:

[Chad]

Garth- I too have an '83 Stumpjumper Sport frame and a box full of the most of the original parts.  I'm not sure what the tire clearance is like, but I have this neat old article from '83 as a reference http://www.vintagecrank.com/vintage-bicycle-articles/Fat-Tire-Bikes-Bicycle-Mag-May-83.pdf   Looks like every bike test is running 2.125 tires.  I also have a '87 MB-2 (one of Grant's first designs, the first was the '86 MB-1) that can only fit a fit a 1.9 tire.  I was able to squeeze in some reproduction Panaracer Timbuk II 2.0 tires, but they are super tight fit between the chainstays.

 

Jim and Ted- sounds like you guys have similiar issues on your early Bombadils (mine is a 52 BTW), so the problem is not just unique to my Bomba.  I think you folks our right about the Bomba being designed at a time when the Schwalbe HS 315 "Fatty" (true size 45-47) was the biggest 650b tire readily available. I CAN get about 5mm of clearance between tire and bridge if I run the Quasi's at 25-28 psi, but the one time I ran them that low I got a pinch flat.  I usually run 35 on pavement and then drop to 30 on rough trails.  I would like to eventually upgrade to a tubeless setup.

 

Mud clearance was a big issue this past season for both my Hillborne and Bomba.  I used my Hillborne for the Dirty Kanza gravel grinder and ending up carrying it for 3 miles because the wheels kept getting stuck between the frame and sidepulls.  I ended up wearing through the paint in a couple of spots when I finally was able to get the wheels unclogged enough to spin the clay-like mud was full of sand and pebbles.  I was running 40.5 wide Fatty Rumpkins and had at least 10mm of clearance above the tires on the Hillborne.  I may switch to Paul Racers and 38 mm tires this year on the Hillborne.  Similiarly, our local single track trails in KC were closed most of June and July here in KC due to rain and when they were open, they were still sticky in dirt and slick on the rocks.  I tried running the Schwalbe Fatties but could not get enough traction for climbing.

 

I have been talking to Rick at D&D cycles about getting the Bomba repainted, but I don't want to wreck the new paint with tire rub.  I am also considering trying to get the bridge raised 5mm.  I just installed Bruce Gordon Rock n Roads and they have tons of room in the frame and the tanwalls look great on the Bomba.  I am hoping the work well enough on our local trails.  I use my Bomba as here in KC as my primary trail bike, as my full-suspension MTB currently lives at our vacation place in Colorado.

 

Chad

 

 

[Chad]

http://www.schwalbetires.com/bike_tires/road_tires/marathon_mondial

 

I may try the new 650b x 2.0 Marathon Mondials on the Bomba when they become available.  I have considered Big Bens, but I don't think they will work well on the trails in my neck of the woods.

[Surlyprof]

I would think twice about the Mondials if you are thinking about them for dirt.  I use them in a 40 for commuting and they roll well on the road are are sturdy (no flats in over a year).  I bought them hoping they would be a good crossover tire for road and trail but they tend to slip a lot on dirt.  Too much smooth surface area in the center.  The knobs open up a little on the sides which provide pretty confident turning on hardpack trails.  In my opinion, Mondials were designed for road and hardpack but not dirt and rock.  Perfect for my commute.

John

[ted]

Chad,

I wouldn't say I have issues with my Bombadil. It works great for me, and I am very happy with it. But it does sound like you probably have the same clearance that I do, and that there isn't anything off nominal about your frame. If you want/need to run Quasi-Motos at 30 to 35 psi and would rather run larger tires that that, I suspect you would be happier with a different frame. Perhaps a Hunqapillar.

regards

Ted

[Chad]

I would agree Ted..  I too am happy with my Bombadil.  I am trying out the Bruce Gordon Rock n Roads and I think they might be a good happy medium.  I have spoken to Riv and for $2400 they can have Waterford build me a 48cm Bombadil in any stock Riv color.  However, Brian and Vince suggested that the newest Hunqapillars have even more tire clearance than the the second gen Bombadil.  They did suggest that with my 80 PBH I would get a better fit on a 48 Bombadil or 48 Hunqapillar especially with the tires maxed out.  My Hillborne is a 51 and fits me great, but I run 42mm tires.

[ted]

Glad you like your Bombadil, though you might like a 48 Hunqapillar even better. Get a frame and wheels, move all components over from the Bombadil and your all set. Then if you like the new rig sell the Bombadil frame and recoup half your outlay. Of course if the Rock n Roads do it for you no reason to change, but if you really want big tires you probably want a Hunqapillar.

[Leslie]

My Bomba is a 56, 650b, and I've run 2.3 NeoMotos under fenders;  if I pulled the fenders off, I have no idea what tire is out there that would be too big...  I think there isn't a 650b tire that it couldn't fit....

[ted]

Does your bike have the crown with the partial moon cutout (like a Hunqapillar), or the three dots (like a Hillborne or Hilsen)? Diagonal tube and mid stays or parallel second top tube?

[Leslie]

Mine?  It's a diagastay Bomba w/ the half-moon crown...  (see the pics from my earlier post in this thread if you'd like).

-L