That Pometamine conversion - formerly 700c/29" issue

[Ham]

Some while ago, with the assistance of a helpful vendor in these Hallowed Halls, I got my old Pompetamine into shape for sale by the inclusion of a 135OLN Single Speed Wheel, that wheel is 29"

Now, with both 29" & 700c being 622 bead, I expected no issues. Only, the 700 tyre was close to an impossible fit. I got it on, puncturing two tubes beyond redemption as part of fighting the good fight, before succeeding (albeit with a 26" tube).

Unfortunately instead of selling it, I gave it to SiL-to-be, who loves it. FF a few months and this tyre was losing too much pressure, so the time had come to sort.

The Pomeptamine had loads of clearance with a 28, so I thought I might get away with a 2.1" 29" tyre. I didn't.

Any suggestions? Ideally I'd get a 29" 35 equivalent, but it doesn't seem to be available.

[PaulF]

What’s the tyre/rim combination? I regularly put 700c tyres on 29er rims but I’ve had one tyre that was a pain to fit which I suspect was too small.

[Brucey]

if the rim is 'tubeless compatible' then IME it stands a fair to average chance of being a tighter fit than 'normal' 700C rims.

cheers

[Ham]

Rim: WTB i23, indeed, tubeless compatible
Tyre: Conti Cyclocross 700 x 35 (v v hard to fit)
Schwalbe 29 x 2.1 v easy fit (thumb)

I'm thinking rebuilding onto a known good 700c rim may be the way to go.

[zigzag]

the key in mounting tyres (especially on tubeless rims) is to make sure the bead is in the "well" all around the rim before mounting the last section. i've mounted several different 700c tyres on the 29er tubeless rim quite easily without any tyre levers - it's the same size rim if manufactured with correct tolerances.

[Somnolent]

As a very general rule of thumb (for any given 700c rim) Continental tyres are significantly harder to fit than Schwalbe.
More detail about specifics in the sticky.

I'm not at all sure that your difficulties are entirely rim related.
 

[Ham]

if the rim is 'tubeless compatible' then IME it stands a fair to average chance of being a tighter fit than 'normal' 700C rims.

cheers

Yup.

Basically, with the knowledge that the diameter is the bloody same, it had to be the well, which is shallow and narrow on the WTB.

Time and patience, as ever, centreing the bead all round, it can be fitted. The Conti is slightly tighter than the Schwalbe, but I managed to fit with finger force only. I'd hate to be trying to change/patch a tube in cold/dark/wet thobut.

Still considering rebuilding as a standard clincher, be nice to see if I can find one with at least the allegedly same ERD (603) - Mavic A119 is allegedly 607 to let me re-use the spokes

Oh, anyone got a use for a 29" tyre?

[Torslanda]

Schwalbe Spicer in 700x35 is a known easy fit on that WTB rim, as would a 40mm Hurricane. Impac Dutchpac in 32 should fit too, without any significant effort.

Contis can be absolute bastards to fit. I had to inflate a couple of 2.2 Rubber Queens to over 70 psi and leave them in front of the heater for half an hour before they popped into shape, once upon a time.

[sojournermike]

Schwalbe Spicer in 700x35 is a known easy fit on that WTB rim, as would a 40mm Hurricane. Impac Dutchpac in 32 should fit too, without any significant effort.

Contis can be absolute bastards to fit. I had to inflate a couple of 2.2 Rubber Queens to over 70 psi and leave them in front of the heater for half an hour before they popped into shape, once upon a time.

That doesn’t sound entirely appropriate Tors!

[Ham]

Tube went bang.

This doesn't look good





Not seen much like that before, at least with a new (although a few years old) tyre. Storage issues or the earlier levering to get on the rim?

[LittleWheelsandBig]

Probably the second.

[Ham]

This Pometamine conversion is turning into a bit of a saga.

Got the tyres sorted,as above, but next issue was that it dropped the chain in fairly normal use. There was some wear (actually unusual wear given the mileage) so I started looking for the cause. Which seemed to be the chain line was about 1/8" out, as compared to the original Alfine sprocket. In my mind that would account for the drop and the excessive wear.

Can't think of how to fix, though

(note that the wear wasn't more than 0.75%, and that brought the chain to the end of the horizontal dropouts, indicating yet another possible issue that the dropouts may not be long enough for SS use)

[LittleWheelsandBig]

If you run a chainring one tooth smaller or bigger, that will shift the rear wheel backwards or forwards. Perhaps the Pompet's chainstay length was designed around a different chainring size.

[Brucey]

it sounds as if you have a wheel out of a genesis day-one singlespeed model. IIRC this uses a chainline that is a bit wider than if you have an alfine hub with the dished sprocket turned inwards but about the same as if the sprocket were turned outwards.  IIRC Genesis use a ST BB/chainset in that bike so the chainline might not be as per an Alfine crankset.

 Maybe you can adjust the chainline by moving the chainring and/or using BB spacers and MTB style cups (which are narrower) if you have an alfine crankset.

FWIW there are such things as half-links for 1/8" chains (which move the wheel 1/4"), and 1/8" chains run OK on 3/32" sprockets , so that is one route ahead. KMC B1 is my favourite 1/8" chain but

a) you must keep it well oiled, the chain is fully bushed and the oil won't get to where it needs to go via the rollers alone and
b) the chainline needs to be cock-on

  If the chain is 0.75% worn it is due for a change anyway and the wheel will be ~1/4" further back than with a new chain. If you remove a whole link from the chain the wheel will move 1/2" forwards.

FWIW the failed tyre looks like it has failed because it was a tight fit on the rim and the wire bead chafed through during fitment.

Vittoria Voyager hyper in 35mm should fit OK on that bike and is usually not a super-tight fit  on most rims.

cheers

[Brucey]

further to the above I have just measured the chainline on a day-one singlespeed model and the chainset has a 52mm chainline in the inner position. With a typical (eg Dicta) freewheel the rear hub has chainline  ~54-55mm, i.e. that wheel gives a rubbish chainline even when fitted in the frame it was intended to go in.... And the bike has an absurd Q value for a singlespeed....

Of course the hub can be respaced to move the chainline inwards a couple of mm but

a) this will push the disc mount out of position, potentially making any brake fitment impossible and
b) even this probably isn't enough for a good chainline onto an alfine crankset, not without changes as described above, certainly.

I quite fancy machining the rear face of a freewheel so that it gives a better  chainline, but I dunno how easy this would be...

Wot a palaver!

cheers

[LittleWheelsandBig]

With a lathe, it is pretty easy to machine a hub to position a SS freewheel a couple of millimetres closer to the centreline. Useless for a fixed cog, of course.

[Brucey]

yeah there is a little wriggle room of that kind. Shame the wheel has to come to bits to get the hub in most lathes.

FWIW the back of the freewheel is ~4mm clear of the spoke elbows as things stand.

On the day-one I have (which is a bit of a project) it looks as if there is enough room (with the brakes that are presently fitted to it) to move the disc leftwards by 1-2mm before the caliper runs out of lateral adjustment and/or the disc hits the ISO  adapter. Dunno how the pomp compares.

cheers

[Ham]

A few ideas there, not sure where the wheel comes from, although the JoyTech hubs on the DayOne look to be a likely candidate. Not sure of the lateral adjustment, possibly just the mm or so from the BB7 adjustment