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I have Fulcrum 5 DB wheels, which are not tubeless ready. My previous wheelset were tubeless compatible and I've been impressed with running tubeless.

So my question is: Assuming I can mount my tubeless tyres on the new wheels and can get them to seal and not leak air, is there any reason I shouldn't run these wheels tubeless? Is the rim going to 'hold' the tyres less tightly and cause roll offs? Is there something else going on with tubeless compatible rims that I've missed?

My tyres are Schwalbe Pro Ones

  • Is it possible to swap the previous wheels to the current bike? – Criggie Sep 22 '16 at 9:16
  • I've purchased the fulcrums as an upgrade. I can put tubes in if necessary, just wondering whether I have an option to go tubeless – Mac Sep 22 '16 at 11:33
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    How necessary are tubeless for you? There doesn't appear a rolling resistance advantage yet for tubeless road (I expect that to change soon however) - latex tubes plus clinched tire still seems to have the lowest RR. – Rider_X Nov 27 '16 at 21:27
  • You do, of course, need to seal the rim, and a rim that is not designed for tubeless may be harder to seal. – Daniel R Hicks Nov 27 '16 at 22:43
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    @DanielRHicks - Not only that, but severe tire deflection can cause the seal to break momentarily (burping) and you may lose more air before resealing than with a rim that was explicitly designed for tubeless tires. – Rider_X Nov 28 '16 at 21:35
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One of the considerations (assuming you are able to get a good seal) is that air loss under a tire burping may be worse than a tubeless specific rim. In CX this is definitely a consideration, especially if you are pushing the lower limits of tire pressure (e.g., < 30 psi on 700x33c is amazing on slick off camber turns, but it is easy to fold the tire in a hard high traction turn). A large burp could drop the pressure dangerous low, resulting a loss of control and injury.

For running on the road, it is unlikely you will want the pressure at such low levels, so burping events are much less likely. [DISREGARD - see Update]

Update - Nov 28, 2016

Found this quote from Lennard Zinn:

When using road tubeless tires, I recommend using tubeless-specific rims. For the lower pressure of mountain bike tires, I think, other than a bigger burping issue on corners due to the lack of the bead-locking “hump” on the medial edge of each bead shelf, that tubeless conversion with most rims is fine.

Read more

For road bike applications, Lennard recommends only using tubeless-specific rims, but for mountain bikes (read larger volume tires) this is not always necessary depending how low of a pressure you are running and how aggressively you are riding. Similar to my initial answer, Lennard also points out you stand to lose more air in a burping event.

Thinking about Lennards answer some more, I suspect his recommendation for road tubeless has to do with a lower margin-for-error with a road tubeless tires. You are dealing with smaller air volumes, and are much more susceptible to negative consequences associated with air loss events.

For example, you could have a poor rim/tire seal. It seems to hold air at initial inspection but it is in fact slowly leaking air. Air loss during a ride could result in the bike becoming uncontrollable. With a larger volume tire, slow air loss is less of an issue because your margin of error is larger. Small volume tires could reach critical pressure levels much quicker than a larger volume tires under the same poor seal scenario.

Because road tubeless tire a smaller pressure buffer, mistakes in your setup become critical to safety as critically low pressures can result in a bike becoming uncontrollable.

Conclusion

I would follow Lennard Zinn's advice and only uses road tubeless tire with a tubeless-specific rim.

  • Wow, I didn't know CX ran tubeless. I thought it was only larger volume tyres. I guess you really do learn something new every day. Might get the no-tubes sealant out on my red metal 5's and see what tubeless feels like. – Chris Nov 27 '16 at 22:13
  • @Chris - Be careful with a tubeless setup, I would recommend tubeless-specific rims as you are generally running very low pressures in CX and any burping event could drop the pressure critically low. CX has always been obsessed with being able to run low pressure, this is why tubular tires dominate at the elite levels. – Rider_X Nov 28 '16 at 21:31
  • I only ride MTB but being pretty light I often run pressures in the region of 25psi anyway. Plenty of grip and so far not got a pinch puncture. – Chris Nov 28 '16 at 22:15
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I am currently running tubeless tyres (Maxxis High Roller LUST) on non-tubeless rims- it is working just fine and has been for a number of months now!

The main thing that needs to work is the initial seal. For some reason, when I installed the tyres, I didn't get the typical pop you associate with the bead seating itself on a tubeless setup, and I can only assume this is due to the fact the rims do not feature the slight lip of tubeless ready profile rims. However, the advantage of my setup is that the tires are quite chunky and sitting on fairly narrow rims so I think the bead has essentially squished itself into the rim seating. As I've said though it is holding very well- I've even burped them once or twice and the seal has held just fine.

So from my personal experience, it's completely doable, however I think it would be dependent on the tyre/rim combo.

Note: Prior to buying my current tyres I tried to set up my non-tubeless rims with non-tubeless tyres. Surprisingly, the only thing that prevented this working was existing holes in the tyres. It is entirely possible the whole tubeless-ready idea is another bike-industry gimmick.

  • Thanks for the info. Your tyres are MTB right? My setup is road, 28mm tyres on 23mm rims. I wonder if that makes a difference. – Mac Sep 22 '16 at 16:49
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    Ah ok; they are- I wasn't aware people ran tubeless with road bikes! It may make a difference as the rims are significantly narrower, however assuming the rim profile is the same I don't see why it wouldn't work. I forgot to mention it's also prudent to do the initial inflation with an air compressor, the floor pump didn't quite cut it. – RobinHorner Sep 23 '16 at 0:11
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I've been doing exactly what you're doing:
'regular' road clinchers with Schwalbe Pro One Tubeless tires ... and running them as tubeless. Yes, it's possible. Yes, it's safe. The key point is the Tubeless tire! The rims are [mostly] all very similar but the key is to have that first seal (i.e., the seal which occurs when you first set up the 'regular' rim and the tubeless tire). You'll know if it's holding air, ... within 10 minutes it'll either still be full or will have lost air within 45 seconds. Yes, run it with sealant! The sealant is used to stop air loss: at the rim strip, out of the tire pores, and out of the rim/tire bead contact area. The 'SNAP' people are used to is due to the tubeless tire running in the inner channel of a tubeless rim and then hitting X pressure and snapping up out of the channel and against the side of the rim (where the tire bead sits against). With a 'regular' rim, the inner channel is missing so the tire simply slides out gently and slides into position. This though will only work if the tire is sitting somewhat taught against the 'tubeless tape' sealed rim. Yes, the rim bed needs to be 'sealed' (e.g., Stan's No-Tubes tape is some of the best, and two layers of tape helps make the tire beads tight even in a regular rim).

The comments about pressure differences are indeed [mostly] correct. Mtn bike speeds are not as high which means the air pressure won't exert as much force against the tire to stretch and jump over the top of the rim. The risk between the two disciplines is the same, but the likelihood of catastrophic failure while using non-tubeless rims and non-tubeless tires is much lower if trying to cobble together mtn tubeless versus the higher likelihood of failing with road tubeless ! Key Learning: ONLY use tubeless tires for road tubeless!!!! (and pump them up to a reasonable running pressure) The risk we all face is having the tire bead roll off (same problem we faced in 1985). The tubeless tires though avoid this problem due to carbon beads whereas 'regular' tires use steel or aramid / kevlar beads. Carbon beads don't stretch, aramid / kevlar beads do stretch. Manufacturers and industry participants are protecting their liability and their products. Therefore always consider the source of any comments (they aren't necessarily wrong but the speakers have a vested interest in having us chose their direction). For me, I care about the facts, the numbers. Incredible these 'experts' can't agree on a standard, ... oh, something like say Road UST. Just do it already. The many different Tubeless Compatible, Tubeless Ready, No-Tubes systems... the reality is they all adhere to a different 'standard' (if you care to call it that). Unfortunately, it comes down to who is holding which tape measure while they build and label their parts. Hmmm, again it sounds like 1985.

The final decision is always our own. I typically start slow and gain some experience on any new gear after I've read everything possible about the real numbers!!!!

I am of course always willing to ingest additional information so if anyone has any 'real' information / numbers, please do advise.

  • The other issue with using non-tubeless specific rim in a road tubeless setup is a lower tolerance on the rim bead seat diameter, depending on the tire/rim combination, this can allow more wiggle room which could result in the tire bead climbing over the rim at the higher pressure. With a tubed setup the extra friction against the inner tube keeps the bead in place even if there is a loose fit with the rim. Manufactures often undersized non-tubeless specific rims to make fitting tires easier. – Rider_X Sep 21 at 1:47

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