Brompton wheel building

[Charlotte]

I know that some people aren't awfully enamoured of Brompton's wheel building skills.  As an amateur wheel builder myself, such things worry me.  I currently have a new Brommie on order and it should be arriving some time next month.

What should I do to ensure a longer-lived wheel?  Slacken off all the spokes and re-tension and true?  Or actually tear it apart and start again from scratch using some arcane majik?

[border-rider]

I'd just leave well alone until attention needed

On all mine (I'm on my 2nd Brommie and 6th wheel) the hub/rim have failed before the wheel has gone far enough out of true to worry about.  With tiny wheels like those, you can get away with *really* poor wheelbuilding

[Biggsy]

Or actually tear it apart and start again from scratch using some arcane majik?

I don't believe there's ever any need for that with any wheel unless changing the spokes (like Roger has done with Brommies).

To make good as possible with existing spokes: detension; tension and press spokes hard with thumbs to make conform to the hub flange; true; stress-relieve by squeezing hard together pairs of spokes.

I have a question myself (perhaps a rather dumb one): is the rear wheel supposed to have the rim centred between the locknuts in the normal way?  The dishing of mine is well out if so.  I haven't bothered to correct it yet.

[border-rider]

is the rear wheel supposed to have the rim centred between the locknuts in the normal way? 

yes

[Biggsy]

Thanks.  Both my Brompton wheels were poorly built, and rim tape was missing from one.  I intended to retension them, but procrastination got the better of me, and I've already ridden them a fair bit as they came (except for the addition of rim tape!).

[rogerzilla]

They won't collapse but the factory wheels have a terrible reputation for breaking spokes.   Some people claim to remove the rear wheel to replace a spoke more often than to repair a puncture.  The quality of the materials is OK (Sapim spokes) but they don't stand a chance if they're too slack and they can move.  The guy in C H White said they get good ones and bad ones on new Bromptons.

The main annoyance with building 16" wheels is that (if you don't have a self-centring jig) your dishing tool doesn't fit.

[Arellcat]

I had the first spoke break in my B's rear wheel somewhere around the 800 mile mark, but by then the rim itself was well on the way to being cut to pieces by the grippy-but-scouring Fibrax brake blocks plus a Scottish winter.  So I took the opportunity to do a rebuild, lubing the spoke threads and eyelets in the new rim and stress relieving the thing as I went along.  I tensioned the spokes to the point where I was worried the nipples would round off (which also made me question the quality of my Park spoke key).  Another 500 miles since then and the wheel has been very happy.

Of course, I was dismayed to find that the Brompton butted spokes (137mm, 154mm, 158mm) didn't match with the 150mm bars-of-steel I needed for the hub gear rear wheel.  I already had the spare Brompton rear rim, but a Velocity Aeroheat might offer more possibilities.  I did read that Sapim Race were available in 150mm, but can't find the reference now.

[andygates]

Never had a problem.

Mind you, a poor abused Brompton on the second half of the Dumb Run had five go at once in a kaboom.  Horrid maintenance, heavy rider, it was overdue.  Oh gods that screeching, will it never stop?

Building little wheels is surprisingly easy.  The rim is massively stronger relative to the rest of the parts so there's little truing to be done.  Just tighten up and go.  I've had to do it for a Bob Yak wheel that was hopeless out of the box, but never for a Brommie...

[orienteer]

I usually check for even tension by plucking and adjusting the spokes to get roughly equal pitch from each. On a dished wheel the drive side has higher tension than the other side of course.

Amazing how many slack/overtightened spokes I've found on new wheels that way.

[Arellcat]

Mind you, a poor abused Brompton on the second half of the Dumb Run had five go at once in a kaboom.  Horrid maintenance, heavy rider, it was overdue.

And famously doesn't wash the bike either.  He just won't be told. 

[Kim]

Mine's now at just under 200 miles, so I took the opportunity to bung the wheels on the truing stand and see what's what...

Front wheel: Brompton Shimano dynamo hub wheel - Vertical true was distinctly dodgy, with a couple of pairs of spokes having much less tension than the others.  Not too bad horizontally, but still room for improvement.  I re-trued, abused the spokes a bit and repeated a few times until it stayed in shape.  Will see how it goes.

Rear wheel:  This is from a Kinetics SA 8-speed kit, and therefore hand built by someone who knows what he's doing.  Unsurprisingly, it was in much better shape, with just a couple of spokes benefiting from a tweak to bring it back in horizontally.  Except, the dish is out by a few mm (that is, compared to the centre point between the dropouts).  WTF?  I put it back on the bike, and noticed that it was off-centre WRT the mudguard (which doesn't look like it has much scope for moving sideways, being bolted to the rack), but the brakes were happy enough (I wouldn't read much into that, as I've tweaked the brakes since getting the bike).

Is this a weird Brompton thing (pretty much everything on the bike is asymmetrical in some way to facilitate the fold), or a Kinetics cockup?  Should I be re-dishing the wheel, or bodging the mudguard?

[Biggsy]

My 6-speed Brompton was supplied with the rear wheel dished like that, too.  I mentioned it on this forum and was told that it's incorrect and the rim should be central in relation to the dropouts locknuts.  I don't know the official spec.

I never got round to dealing with mine.  I was thinking of completely rebuilding it and procrastinated.  It rides ok.

[Kim]

I've dug the original single-speed wheel out (which I'm keeping as a convenient source of a spare rim) and checked that, and it appears to be symmetrical.

And yes, it rides fine.  Mudguard clearance is the only obvious issue, and that hasn't been a probelm so far (and I've tested it on some of Sustrans' finest).

[rogerzilla]

The wheel should be correctly dished (i.e. centralised as normal) but remember that the rear triangle is offset so it looks a Bit Weird. 

[Kim]

Righty.  I'll have a go at sorting it next time I can be arsed, or have to remove the wheel, whichever comes first.

[Arellcat]

The rear wheel on my 6-speed was also offset with respect to the centreline of the bike.  I was never sure if it was the wheel or the rear triangle and I thought I was losing my mind at one stage.  When the wheel broke its first spoke, I took the opportunity to disassemble it completely and rebuild it, and I just centralised it to the locknuts.  My truing stand is the Ultimate single-sided one, so I didn't really have a choice.

[Kim]

Sounds like Brompton's wheel building process is somewhat lacking in quality control.  They're probably making that "the tensions are even so no need to check the dish" assumption that you read about in guides to building front wheels, or something.  Surprised that a Kinetics wheel would be similarly afflicted, though, and was wondering if there was a subtle reason for it.

Having heard stories about the rim-eating habits of the stock brake pads, I replaced them with Kool Stops from the outset (which combined with cable length jibble is why I can't vouch for the original alignment of the brakes).

[Kim]

Okay, on the basis that the wheel wasn't going to get any cleaner, I've had another go at it and centred the rim.  It now lines up pleasingly with the mudguard and the seatpost, the rear triangle doesn't look any wronger, the brakes just needed a nudge in the right direction and in as much as I can tell from a 500m lap of the block, everything still appears to work.   

[SA_SA_SA_SA]

I have read of a heavy person claiming that building a one cross rear wheel solved their spoke breakage problems.

[Kim]

My wheel is 1-cross.  The XRF8(w) is quite chunky, and this seems entirely appropriate.

[LittleWheelsandBig]

I built my SA8 349 wheel 1 cross and it has lasted well. Otherwise the spoke angle at the rim is just stupid with such a large hub flange.

[rogerzilla]

The standard wheels have to be built x2 though, just because the standard spokes only come in one length    However, this works for any SA hub in an A-series sized shell, which is all the 3-speeds from the 1930s without brakes, dynamos or other add-ons.  Doesn't have to be an SRF3 or BWR.

Other length spokes are available for fiddlers; I bought a Merc rear wheel for less than the cost of a new SRF3 hub , just to get the hub.  A while later the rear rim on the ex-Mrs Z's bike got concave so I rebuilt it using the Merc rim and a different length of spoke.  Can't remember where they came from, though.  As far as I know her father still has the bike, but I might enquire as to whether he still wants it since he is 73 and he was only using it when he had to pop into Bedford regularly to see his ill wife (now back at home).  I feel a custom project coming on, with an atrociously loud paint job...