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a tight tub inside sucks the bead in and prevents you getting any slack
Makes sense.
However:
a claw hammer wrapped in a rag
😯
O.k, so next question, how much does a 700c tub weigh?
You can get tubs that weigh less than the Procore system claims to (200g per wheel), but at a cost that makes it fairly pointless going ghetto. For cheaper options you seem to be looking at around 300g per wheel. Not too bad considering you can offset most of this by using lighter main tyres.
Given that I've spent over £50 on tubs now, maybe I should've waited until February 😀
However:
"a claw hammer wrapped in a rag"
😯
Yeah. Tyre levers and two people working together couldn't shift it, but that did. Two levers brought a bit of bead out over the lip, then the claw hammer slid under and let me pull on it. I managed without damaging the rim or the tyre, but I'm not letting those 650's anywhere near it again.
daver27 - Member
so what sized tubs do you need for 650b...?goodgrief - Member
650a
nach - Member
Right, I've given mounting a quick go with a 650b tubular tyre
AlexSimon - Member
There are a lot more sizes than 650b and 700c though.
590 mm, 650A
584 mm, 650B
nach - Member
but I'm not letting those 650's anywhere near it again
Given 700c is 622ish and is so slack you can take it off when inflated, do you not want to try using the right size first? LOL!
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I think you might be misunderstanding how toruses behave under expansion. If only we had an exemplary sphincter to hand, everyone could see a demo.
700 is right for doing this with 26. Others might be too. ETRTO is only of limited use for this because going really close to the bead seat diameter with something as unyielding as a tubular isn't desirable for this application.
Stepping through the process is also really interesting, because it's showing me why, for instance, the Deaneasy designed double valves look so inelegant but were probably the best approach without Schwalbe and Syntace's production abilities to hand. Interestingly, they appear to have ended up only selling pre-prepared rims rather than the valves, too.
I'm surprised this ^^^ went without mention, looks pretty easy to do!
That's quite a lot of extra weight to run lower pressure. I still would not want to offset the weight by using a lighter tyre for fear of rips to sidewalls.
I get it, but it seems weighty and a lot of faff.
I think I'll just go wider rim for lower pressure
100gs is "quite a lot of extra weight?".
What planet are you living on?
You can get more weight difference than that changing tyres/tubes!
alexh wider rims do not completely protect you from burping and denting rims 😉
its an extra weigth of course, but for some people it might be irrelevant. I use heavy duty DH tubes (470 grams each one), so in my case I saved 200g with this system 🙂
Having bought Chinese carbon rims for my fat bike that even when fully deflated you have to put the tyre on an edge (say a nice carpeted step) and jump up and down on the rim to unseat the tyre bead, Procore might be a solution to a problem that tighter manufacturing can solve more easily.
5psi front and 9psi rear for the record, and no burping yet.
Denting rims not an issue on the fat bike, perhaps it will help with this.
Agreed, wider rims don't negate the risk of giving the rims a good thump. I'm not saying I don't see the point in the system, but at least on the ghetto set up it looks a lot of faff to run a lower tyre pressure.
100 grams is 100 grams, it all adds up, it's a bad place to have extra weight. I understand though, some bikes and style of riding you won't give a rats ass about that extra few grams.
And where did 100 grams come from? I've not seen that mentioned up above.
@nach, @andrextr I've just given this a try with a 700c tub on a 26" rim and it stays baggy until about 80PSI then starts to twist itself around. The valve stem then gets pulled up into the rim. It's too baggy to lock the outer tyre at up to 50-80PSI and then uncontrollable after that. It fills the rim nicely at 100PSI but I could only do this inverted.
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Did you not have this problem? Cant seem to find any tubs with threaded valve stem that might solve it.
Hi. Yes you have to put 120 Psi to firmly fit the 26 wheel. Yes the tubular has a tendency to invert. When inflating the tubular firmly hold the tire with your hands to avoid twisting (grab the tire in the opposite part regarding the valve). You can put +170Psi and let the tubular stretch 24hours in the rim. When you mount the MTB tire the tubular has less room to twist. Bye 🙂
Rightho, thanks Andre, I'll give that a try.
Outdoors. Wearing goggles. And ear defenders, I reckon!
Andre, on the video there are two threaded valve stems, but tubular tires usually don't have thread. How did you make it?
I've tried this with a 700c tub on a 29er rim.
I'd say it works in principal and it's close to working in reality!
I found some cheap tubs from PX that had the threaded valve - That bit is essential but yes, they seem hard to come by - most seem to not have the thread on.
Getting them on the rim at the same time as the outer tyre is a struggle but possible. I used a Hans Damphf evo 2.35 which are pretty baggy themselves. I wouldn't want to try it with a tighter tyre. Rims are Mavic XM719s with an extra hole drilled for the tub valve and regular tubeless tape fitted. Getting air past the tub to the main tyre isn't a problem with a track pump and some heft - I think it's a DT valve but I can't see it making much difference.
So doing all that, I can get everything pumped up to the point of bouncing the wheel round the garage and feeling that warm sense of achievement. Close inspection though concludes that I can't get the tub valve sealed onto the rim so I'm slowly losing air from the outer tyre. I've tried bonding o-rings onto the valve at the base, building up a 'bung' at the base with silicon sealant, bodging a lockring and o-ring either side of the rim.....nothing seems to solve it.
Like I said, feels really close yet, so far!
Paul@RTW: did you use some sealant? Probably it could plug the leak around the valve?
It was a while ago now but it seems like a bit of an obvious oversight if I didn't try some sealant in there. To be honest though, I can't definitely say that I did! I'm using the outer tyre on another wheel and the tub is sat on the side and as far as I recall neither have any dried up residue on them so it seems like may be I didn't.
Thanks for the prompt, I'm inspired to try this again and get it working.....with sealant perhaps!
Having never seen a tub up close, I have a tap and die set, so you think I could run a thread up a tub threadless valve?
I'm guessing there's some 'meat' on it?
I've found tubs that are 150g, which is lighter than a reasonable tube and also allow lighter tyres to be fitted.
Hi! Sorry for the delay but I don't come here often... You can reach me through Youtube or something 🙂
You can try the tap and die method or using an external clamp mechanism.... something like this:
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Be creative 😀
Bye 🙂
100mphplus - tried that. Failed. There was less 'meat' on it that I thought and it just ended up cracking. The one I tried on was a pretty brittle material which didn't help. You could probably do it with a little more care and patience but I'm not sure I'd trust it not to crack eventually.
I ended up coming across a really cheap tub on PX that showed a threaded valve body so I took a punt and it worked out. I don't see them on the site now. I'll dig out the brand/name and let you know.
This is the tub I found that had a threaded valve but As I said doesn't seem to be available from any Google searched place at least:
Areo Extra Tubular Tyre 700c Black 22mm
Is Areo another PX acquired brand? A lot of their cheap bike accessories are marked as Areo but I've not come across the brand any where else.
I ended up buying a couple of cheap tubs, (@195g ea), they have a brass valve and I managed to cut an M6 x 0.75 thread on it. You have to chamfer the neck with a file first to allow the die to seat on the valve stem and then it cuts no problem.