Workshop tales, trials and disasters.
Maintenance tips, techniques and myths.
Technical discussion, description and outright lies
19 posts • Page 1 of 1
When I designed my Chitanium custom disc road bike, I left lots of room for tyre/guard clearance... just because.
Although I usually run 700x25c road tyres (which was the nominal size I had in my geometry calculations), I can easily fit 35c knobby CX tyres (with miles of space) for back-country adventures.
Just for giggles, I once swapped in my MTB wheels with 26*2.1" knobbies, and there was just enough clearance to ride it up and down the driveway. I've never considered that to be a viable configuration for riding, because the clearance is too tight for any terrain that would justify knobbies, and because the rolling diameter is smaller than design which drops the BB even further (it's somewhat low by design) and messes the steering geometry. But without the need for rim brakes, the location of the rim is not a limiting factor.
And then I come to think... my standard 700x25c tyres have the same rolling diameter as a 650x44b...
I got such a good price on the hubs I built my 700c wheels up on that I bought a spare set, and haven't really known what to do with them. A second wheelset of some kind, I always figured...
I designed the bike with a slack head angle (71°) and used a fork with quite a bit of rake (48mm), so I'm running relatively low trail (about 65mm with my standard diameter wheels - that is, 700x25 or 650x44).
I'm beginning to realise that I may have accidentally built myself a low-trail 650B randonneur bike!
With a slightly smaller tyre, the trail decreases further, which would give me even more of the legendary low-trail rando goodness. Not massively, of course... probably noticeable only by placebo... but suffice to say that I'm in the ballpark, and any likely change will be in the right direction.
Having a set of 650B wheels would also open up the possibility of running modest 27.5" knobbies to turn it into a real monstercross go-anywhere bike.
Of course, it's never going to be a "classic" 650B rando... with sloping top tube, threadless headset, carbon fork without mounting points for a porteur rack ... but it should come somewhere close to the right ride qualities.
So... where to find a set of good 650B rims? On the cheap, because... well, because I'm cheap , and that's the cycling game as I like to play it. And light, too, because I'll be building them with 32 spokes to make up for any strength shortcomings (remembering Bontrager's axiom - light, cheap, strong; pick any two).
Using my 700c rims as a benchmark - Velocity Aeroheat OC, coming in at 415g each - I would think that smaller diameter hoops should be easy enough to find at somewhere close to the same weight. A quick look around the usual sources finds mostly "all mountain" MTB rims at 500g or more.
And tyres? Again, there's plenty of 27.5" knobbies around, but 650B road tyres are a bit harder to stumble upon. What recommendations do people have? I see Maxxis do a 27.5x1.5" Detonator... I used to run 26x1.5" Detonators on my Long Haul Trucker, and quite liked them, but later found out why the 700c variants are notorious for getting flats. Still, it looks like they're a cheap option if nothing else.
Has anybody else considered the 650B rando options on a disc-braked 700C road/CX bike?
If you were genuinely cheap, you'd be waiting for 2nd hand! 650bs are still way too "hot" at the moment to be found a decent prices. Take it from an old cheapskate from way back
I am still anticipating owning my first Fatbike (2nd or 3rd hand) in about 2018.
Since I keep misplacing my common sense down the shed, I guess I'll have to borrow someone elses off the internet.
But even then, it seems the "hot" 650b sales are all in beefy overweight MTB wheels. When they're second hand, they'll still be beefy and overweight. I'm kind of aiming for a similar weight to my 1700g 700c disc wheels (which I built with change from $200, if we're comparing cheapskate credentials).
Would it be wrong to do this with no-name Chinese carbon 27.5" rims? They are abit spendy, but the irony of building classic old-school 650B randonneur wheels with disc brakes and carbon rims is somewhat delicious...
Light Bicycle rims are more than fine (for disc use, not rim brake). American Classic 101 are 32H and quite light, hard to get here though and won't meet your price requirements. The lightest Stans rims are far too noodly.
Hetre / Babyshoe Pass for slicks. Don't skimp on this aspect.
Well, in spite of Blakey's excellent advice, I skimped on tyres and went with the Maxxis Detonator 27.5x1.5" slicks. A pair of them for well less than the pre-shipping price of a Babyshoe Pass. I'll think about upgrading later maybe, but fat Detonators were actually a really nice tyre to ride on my 26" Long Haul Trucker, so I'm optimistic.
I've also grabbed a pair of Schwalbe Smart Sams - I have had these as a 700c CX tyre before, and they're quite good on hardpack due to the continuous centreline tread blocks. Will be interesting to see how they go in the smaller diameter with a significantly bigger bag. These will be my mostly-offroad-but-don't-suck-completely-on-road tyres (as opposed to the Detonators for kinda-on-road-and-gravel-unless-I-feel-like-going-offroad-a-bit conditions... I know from experience they don't climb well on wet clay )
Needless to say, I've got my 650B wheels done. Well, almost. Laced and tensioned, just needing a bit of final trueing before we roll.
The one sticking point now... where does one obtain wide-road sized 650B tubes?
Standard 27.5er tubes are at the wider end of normal MTB width... 2.2-2.5" and such. That's going to be too big to stuff into a modest 1.5" road tyre.
If I don't find 650x35B-ish tubes soon, I'm thinking I'll probably try and get away with running narrow 26" tubes with a bit of stretch. I've got stocks of them, and an extra inch or so of diameter is well within their stretchability.
Actually keen to hear about the performance of these. I have one 650B setup that runs sub 42mm tyres. Might be a decent narrow budget option.
I use these:
http://www.jensonusa.com/!4wf12MwK6JmF6 ... resta-Tube
But 26" tubes will work, done it before, will do again as required.
26" tubes will go in no worries. have used 26" tubes on my 29er.
i've also used 26x1.5" and 700x28 detonators with no real punctures. (fingers crossed, i'm doing pretty well in the puncture game.. even with paperthin ultremo zx's)
Continental and Schwalbe both cover the 650B space with 26" tubes for a slightly wider tyre by 5-8mm. I suppose you use up some of the resilience of the tube stretching it an extra 5 or 6% around the rim, so they work out narrower. Check out the Schwalbe SV12 in this link
and at this Conti link
http://www.conti-online.com/www/downloa ... bes_en.pdf
you can see that their city/trekking bike tubes each cover a range expressed as an ETRTO tyre size from for example 559x37mm through to 597x47mm, certainly covering 584x42mm (the 650x42B that i am interested in).
But I'd use this approach rather than try to use 700C tubes or anything from a larger diameter. Folds in tubes are not good for their longevity!
The moulding on the sidewall calls them at 40-584 (ie a 40mm tyre). So they're sub-42, but they're still a decent sized bag.
And at $25 each, on a free shipping week at Velogear, they definitely meet the "budget" criterion.
Don't hold your breath for a review... it will come eventually, but this project is taking a while
Finally got around to finishing one wheel.
Went from this:
Wheels are nearly exactly the same rolling diameter... just that one has 25mm bags, the other has 40mm bags
I thought I had a spare 12-30T cassette in the box, which I planned to use on this, but it failed to be there when I looked. I didn't have time nor inclination to pull the cassette off my 700c wheel for a test ride. New cassette required.
Unfortunately, I overestimated the clearance my frame has for big knobbies. The 27.5x2.1" Smart Sams I got for it will fit and turn, but we're down to a couple of mm clearance either side... which won't take much dirt and mud and rubbish to fill up. Not sure whether to shave the shoulder knobs or sell them unused and try something different.
Hopefully I'll get the front wheel trued up properly sometime soon, and I can give her a test run as a 650b-er.
It's an ebay special
One like this:
http://www.ebay.com.au/itm/Picasia-fork ... 35ce6c24ee
They can be had under a number of names (Trigon, Picasia, Token, Ritchie, Corratec), for a variety of prices. I went with the cheap one with the least garish logos.
They're a non-suspension-corrected 26" MTB fork, which means they're neither fish nor fowl in terms of axle-to-crown length. Longer than a road or CX fork, but too short for most MTBs. I designed my frame around the oddball A-C length, so it's not a concern. Upsides are the buckets of tyre clearance, the weight (460g) and the price.
i'd just been scouring ebay and thought i saw a similar one, albeit covered in logos. i'm looking something with 390-395 however.
Well, I finally got around to finishing my wheels.
On Sunday, I had the opportunity for a one-way solo ride from home to Maryborough, which is about 80km. So I fitted my 650b wheels and set off into a head/cross wind. I usually do a 60-90km bunch ride before Saturday breakfast, so it's a fairly routine kind of distance for me.
The most obvious effect of the fat tyres (27.5x1.5" Maxxis Detonators, aka 650x40b) is in ironing out crappy road surfaces. We get lots of coarse chip-seal tarmac around here, especially on quiet back roads that are otherwise nice for riding. I found straight away that there was basically no difference in feel and resistance when crossing from hotmix to chip-seal to gravel. They just roll smoothly on. Very comfortable.
Aside from the rims and tyres, the other difference to my usual setup is the cassette. I've fitted a 12-30 to these wheels in place of my usual 11-25. I wouldn't have expected this to have any effect at all, but I kept finding myself tripped up by the unfamiliar gearing (combined with the ~4mm smaller rolling radius? Would that even make a perceptible difference?)... often finding myself cross-chained and at one end or the other of the cassette. Weird.
I only really stopped once on the way (for a sausage roll, as per the photo above). Running later than planned, I tried to push it along a bit, keeping the speed up so as not to miss what I was heading to Maryborough for. I was working pretty hard. Strava says my moving average was 26km/h... not too bad for me on a solo run, considering we usually average 28-32 on Saturday bunch rides. It felt mostly uphill... although reviewing the elevation profile when I got home said it was mostly downhill. Maybe the headwind? The realities of riding without a bunch to work with?
Anyway, I had a nice ride, certainly comfortable, but pretty knackered by the end.
Tuesday mornings my bunch does our hills route. A bit over 500 vertical metres climb in 27km. I usually get to the top of the climbs near the front of the group (not blowing my own trumpet too hard... most of these guys are 10-20 years older than me ). This morning, I figured I'd give the 650b wheels a run, given that they were still on the bike and I'm too lazy to change them.
A very telling ride. I was really working hard just to stay with the bunch. On the second last climb on the way back, I cracked. Burned the last match. Had to let them go. I made use of that low gear, trundled over the last few climbs at my own pace and didn't see the others again.
So, that's how things look with my new 650b wheels. They're comfortable, but they're bloody hard work to ride. Sure, they were never meant to be climbing or race wheels, but even as all-day cruising wheels... working as hard as I did on Sunday, all day, doesn't sound like a really appealing proposition.
To be honest, I'm a bit disillusioned. I'm really surprised that they seem to have made so much difference, but this morning sealed it. I don't think I've suddenly lost a heap of form, and I haven't changed anything except the wheels. Maybe the Detonators are just a rubbish tyre. As I said above, I used to ride them a bit on my 26" Long Haul Trucker and quite liked them, but I didn't do any bunch riding or "fast road rides then, and didn't have a normal 700c road bike to compare them to. But again, I'm finding it hard to believe that a better tyre would make such a difference that would be required to bring my 650b performance back up to where it should be.
Suffice to say, I'll be back on 700x25c tyres for my next road ride. Hard to imagine when/where I'll use the 650b wheels in future. I guess they'll be in their element on dirt roads... I took a ~7km dirt detour on Sunday, and the bike handled it beautifully. But I often ride dirt roads on my 25s, so the big tyres are just an added luxury there in my books.
I'll hang the little wheels on a hook in the shed for a while and think about it.
You were warned.
As a comparison, after moving from 700x28 (Paselas) to 650x42 (Hetres) I smashed all my Strava routes without trying.
The real benefit of 650B on a road bike is access to amazing - fast - tyres. Hetres are one, Babyshoe Pass the other.
The 80:20 rule hasn't worked.
I guess it's now a choice of whether to double down and buy some really expensive magic tyres to get the 650B magic flowing. Whether I really believe in the concept enough.
Do you believe in magic, Peter Pan?
I was pretty bummed last night... left out on the road by a bunch of 60 year olds, then a crappy day at work. But yeah, that's first impressions... of the Detonators, if nothing else.
Probably also worth mentioning is tyre pressure. I went radical for the long Sunday ride, and rode them at 40 psi. Upped them to 60 psi for the hilly ride. Haven't done any serious looking into % sag or whatever... just taking a punt on low pressures (noting that I have run my MTB tyres in the low 20s of PSI for nearly 2 decades). I did run those Detonators at ~80 psi (their max rated) on the LHT. Maybe I should try that before I write them off.
80psi will be awful on them.
I run my hetres ~40 and don't reinflate until they go under 20.
I did end up buying a set of the $20 650B detonators for the townie, they were ~500g compared to ~300g 32x650b GB they replaced, roll slower and have a noticeably stiffer carcass. For a shops bike, no worries, but for a rando/road setup, hell no. I think they're better than the truly awful Col de la Vie's (that I forced on someone for free to get rid of them), but worse than the fatty rumpkins. Not even in the same galaxy as hetres/pari moto/babyshoe pass
I have a suggestion, if you pay postage, I'll mail you some hetres to play with for a couple of weeks. Cheaper than buying babyshoe pass'.
Barefoot, use the Frank Berto-derived chart on the Bicycle Quarterly site to work out the right initial tyre pressure based on your total weight. Then work out what's correct for you with small changes of 2-3psi at a time from there till you feel its right and your speed is back where it should be, with added comfort. If you change by 20psi increments you won't learn much at all.
i use Barlow Pass tyres (700x38C) at about 70 rear and 50 front (100kg plus bike) but i'm decreasing the pressure a bit at the moment. The Hetres and Babyshoe Pass tyres have about 15-17% more air in them so I'll be using them at that much less proportionately to start when I get my Rawland Stag on the road (soon).
Blakey is being very nice to you.
19 posts • Page 1 of 1
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