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Discussion Starter · #1 ·
Anybody try this combo? I bought a Specialized Ground Control Grid 2BR (UST) tire about 6 months ago and finally got around to mounting it on my Stans ZTR flow rims.

At first, I couldn't get it to seat the whole way around. So I let it down and soaped up the sidewalls lightly and then hit it with the air. Bang! Bang! Usually that means it's seated up. I took it up to about 36psi (max is 38psi stated on rim) while wincing at every plunge of the pump handle. I inspected the tire and it looks fully seated the whole way around on both sides. No air leaks listening by ear.

If I start letting the air out slowly it is still seated down to about 10psi. Once I get into the mid single digits, the tire bead will come unseated while I'm holding it by the rim only. That has me a bit worried. I never used soap to mount tires before so maybe that always does that when the soap is still wet? Stan's site says the GRID UST is a tight fit but still OK.

Never had an Ardent come unseated after letting the air out all the way - I always had to break the bead seal by pushing the sidewall in with my hands.
 

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Vassago Bandersnatch, Motobecane HAL Comp 27.5+
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Anybody try this combo? I bought a Specialized Ground Control Grid 2BR (UST) tire about 6 months ago and finally got around to mounting it on my Stans ZTR flow rims.

At first, I couldn't get it to seat the whole way around. So I let it down and soaped up the sidewalls lightly and then hit it with the air. Bang! Bang! Usually that means it's seated up. I took it up to about 36psi (max is 38psi stated on rim) while wincing at every plunge of the pump handle. I inspected the tire and it looks fully seated the whole way around on both sides. No air leaks listening by ear.

If I start letting the air out slowly it is still seated down to about 10psi. Once I get into the mid single digits, the tire bead will come unseated while I'm holding it by the rim only. That has me a bit worried. I never used soap to mount tires before so maybe that always does that when the soap is still wet? Stan's site says the GRID UST is a tight fit but still OK.

Never had an Ardent come unseated after letting the air out all the way - I always had to break the bead seal by pushing the sidewall in with my hands.
The Stans rims are designed for a standard shaped bead. I was always able to get the 2Bliss models to mount fine on Sun-Ringle Chargers and Stans Flow (1st gen) rims and stay put even when deflating. Maybe the GRID tires have a more beefy square bead that simply will not fit into the "bead socket" of the Stans rims. I can especially see this as being a problem on the newer Flow EX with the very short sidewall. There also isn't an inner barb like UST spec rims to keep the tire from coming unseated. Though my current Velocity rims don't have this barb either and my Geax TNT tires (with a very square bead shape) stays put when I deflate it and takes some effort to unseat.
 

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Discussion Starter · #3 ·
The Stans rims are designed for a standard shaped bead. I was always able to get the 2Bliss models to mount fine on Sun-Ringle Chargers and Stans Flow (1st gen) rims and stay put even when deflating. Maybe the GRID tires have a more beefy square bead that simply will not fit into the "bead socket" of the Stans rims. I can especially see this as being a problem on the newer Flow EX with the very short sidewall. There also isn't an inner barb like UST spec rims to keep the tire from coming unseated. Though my current Velocity rims don't have this barb either and my Geax TNT tires (with a very square bead shape) stays put when I deflate it and takes some effort to unseat.
I have the older ZTR Flow, not the Flow EX.

I ran some Specialized Captains 2Bliss about 2 years ago and they mounted up no problems on the same rim (different wheelset). They weren't GRID - that wasn't an available option back then. The GRID is definitely beefier in the sidewall (why I bought it) and I'm wondering if the bead has more meat too and isn't quite sitting into the bead area on the inside (drop channel side) of the bead seat.

I'm going to let the tire sit over night and see what it does. I'll let the air out again and see if it stays mounted or if it falls back into the drop channel. If it does fall back in, I think I'm going to take the loss and get a different tire. There's no way I'm going to trust that it won't burp/blow off at low pressure on heavy cornering.
 

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mtbpete
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2Bliss is a better choice. The Grid UST is a UST bead and designed for smaller bead seats than the Stan's rim. The UST tires will usually fit on Stan's 26in rims, but not the 29in rims. Because UST is tighter than a 2bliss tire they will compress the rim more and drop the spoke tension more. Even so, if you can get it seated it should work well enough.

If the tire came unseated and the bead fell back into the center channel of the rim, it probably wasn't fully seated to begin with. UST has a strong bead and you can inflate it more than 36. I would avoid going above 45, but I've seen them up to 60 psi for seating purposes. Use some soap and when you get to 35 or 40 psi take a look all around the rim on both sides to see if the line next to the tire bead is sticking above the rim sidewall the same amount everywhere. If it dips down into the rim - that will be an area that's not seated fully.
 

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Discussion Starter · #5 ·
2Bliss is a better choice. The Grid UST is a UST bead and designed for smaller bead seats than the Stan's rim. The UST tires will usually fit on Stan's 26in rims, but not the 29in rims. Because UST is tighter than a 2bliss tire they will compress the rim more and drop the spoke tension more. Even so, if you can get it seated it should work well enough.

If the tire came unseated and the bead fell back into the center channel of the rim, it probably wasn't fully seated to begin with. UST has a strong bead and you can inflate it more than 36. I would avoid going above 45, but I've seen them up to 60 psi for seating purposes. Use some soap and when you get to 35 or 40 psi take a look all around the rim on both sides to see if the line next to the tire bead is sticking above the rim sidewall the same amount everywhere. If it dips down into the rim - that will be an area that's not seated fully.
My bad. The tire is a 2bliss model, not UST. I checked the sidewall and the packaging and they both just say 2bliss or 2BR. They do offer a 29r with GRID and UST - but my tire is not that one.

I was thinking about what Bike Whisperer said above and checked the profile picture of the ZTR flow rim and see that there is no inside lip like on a Mavic UST rim. It's been so long since I taped up a Stan's rim I couldn't remember what it looked like. With such a tight fitting bead plus the soap and the clean, slippery tape, I'm no longer surprised that the tire is slipping into the center channel.

I tried to seat the tire dry (what I've done successfully for more than a decade including UST DH tires with steel beads) and I just couldn't get it to seat (checking the line around the edge as you mentioned). I went all the way to 36 psi and it still was not seated. Once I soaped it up, it was popping on and fully seated the whole way around at 20-22 psi already. I then pumped it up to 36 psi to be extra sure it was on there. Letting the air out slowly revealed that it would jump back into the middle just before it was fully deflated.

My rim says the max pressure for a 2.3 tires is 38 psi max. I remember reading on here about someone who took a tire (not sure what size) up to about 40 and they cracked/split the sidewall or something catastrophic. That story coupled with the fact that Stans rims are not in the same league as Mavic (ran EX823 for years - killer reliable and true UST) has me a bit gun shy to get much closer to that 38 psi.

And good call on the spoke detention with tighter beads. It's amazing the number people who don't understand that or even deny it happens. The Stans ZTR Flow seems especially prone to that (when you really air it up). I normally run psi in the teens so the minimal spoke detention is not a problem on the trail. But at 36psi, the spoke bed is like a handful of cooked pasta noodles.
 

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mtbpete
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I've never seen the bead fall into the center of a Flow rim when deflated. I just aired up a friends over the weekend, then let air out to add sealant through the valve hole. The Schwalbe EVO tire stayed seated. Did you apply only one layer of Stan's yellow tape and no rim strip? If so, I guess that your tire has a fat and tight bead that keeps slipping into the center.

UST rims use a bead-lock, which is the lip on the bead seat that you describe. It's designed specifically for UST tires. It doesn't work as well with some of the older tubeless ready tires because they are not as tight. Stan's rims and most other tubeless ready rims do not use a bead lock. Instead they generally have a wide enough bead seat combined with a larger bead diameter that it keeps the tire from falling into the center of the rim.

The strength of the bead actually compresses the rim a little more than the air pressure. If your tire would stay seated you could see that the spoke tension is lower with no air in the tire.

The Flow rims can handle way more than 36 psi. They are triple walled - they have an extra inner wall. 38 is just a reasonable riding pressure. The reason for the low max is that many customers use tube-type tires with very weak beads that have been known to blow off the rim at 40 psi. The larger the volume of the tire equals greater pressure pushing out, and greater chance the tire will blow off the rim.

I've seen hundreds of used Stan's rims and two types of rim failures due to high pressure.
1. On the Crest, 355, and Race/podium rims some riders set them up for road use and will run hundreds/thousands of miles at 40 psi or more and eventually the center of the rim can crack inside due to the outward force of the tires. Note: none of these rims have the extra wall like the Arch and Flow do.
2. On 355 rim brake rims that were used WITH rim brakes the aluminum will wear down over time due to the friction of grit on the pads. Eventually the sidewall would wear thin and not be strong enough to hold air pressure anymore, and the rim will split on the sidewall. Most modern rim brake rims have wear indicators to let the rider know when it's time to replace the rim, but the 355's did not have a wear indicator.
 

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And good call on the spoke detention with tighter beads. It's amazing the number people who don't understand that or even deny it happens. The Stans ZTR Flow seems especially prone to that (when you really air it up). I normally run psi in the teens so the minimal spoke detention is not a problem on the trail. But at 36psi, the spoke bed is like a handful of cooked pasta noodles.
When I built up a set of Flows to the recommended spoke tension and then put my 2Bliss tires on them I was horrified how much my spoke tension dropped. I have never seen that type of drop in any wheelset I've owned. I ended up building them to about 130 kgf max so that there was decent tension when the tires were mounted. And actually PSI has nothing to do with this, it's simply from the tight bead being seated, tension loss was the same at 20 psi as it was at 40 psi.
 

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Discussion Starter · #8 ·
I've never seen the bead fall into the center of a Flow rim when deflated.
Me either. And I've used a lot of different tires on several Stans flow wheelsets over the years and never had this happen. That's why I started the post.

Did you apply only one layer of Stan's yellow tape and no rim strip?
Correct. I didn't change the tape when I switched to the GC ... I simply cleaned it up and inspected it and then mounted the tire.

The Flow rims can handle way more than 36 psi. They are triple walled - they have an extra inner wall. 38 is just a reasonable riding pressure. The reason for the low max is that many customers use tube-type tires with very weak beads that have been known to blow off the rim at 40 psi. The larger the volume of the tire equals greater pressure pushing out, and greater chance the tire will blow off the rim.
Yeah, that makes sense since the "intended use" is regular clinchers. With the tighter fit of a 2bliss tire, you probably can get a bit more pressure in there. I'm just too chicken to do it I guess. Besides, the tire is seated the whole way around so there's really no point in going higher.

Well, the tires were rock solid about 24 hours later and showed no signs of losing any air. They looked fully seated as any other tire. Once again, I slowly let the air out and once all of the air was out, the bead on the disc side fell gradually into the center channel. The drive side stayed on. However, I just had to barely ... and I mean barely ... give it a tiny push, and then it fell right into the center also. All of my other tires - dozens of them - always required both thumbs and pressure to break the bead off of the seat and get them into the channel. Usually they kind of give a dull "pop" once they slide in.

Like you said you did with your friend's tire, I usually deflate a tire completely and inject stans fluid through the removable valve core and I've never had a tire unseat - even with some clumsy handling. I'm talking both regular clinchers and 2bliss ready type tires.

I guess this combo just isn't going to work for me. There's no way I can use this GC tire on this rim and not risk a burp or rolling it off the rim. It still has zero miles on it so I'll just try to sell it as "mounted only" and get something different. What's another $60 down the drain in this sport, right?
 

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Discussion Starter · #9 ·
When I built up a set of Flows to the recommended spoke tension and then put my 2Bliss tires on them I was horrified how much my spoke tension dropped. I have never seen that type of drop in any wheelset I've owned. I ended up building them to about 130 kgf max so that there was decent tension when the tires were mounted. And actually PSI has nothing to do with this, it's simply from the tight bead being seated, tension loss was the same at 20 psi as it was at 40 psi.
I've read that the newer, burlier Flow EX has made the tension drop less dramatic. But I've never seen any numbers to back up the claim.

To be honest, I'm not sure I've even checked spoke tension when the tire was fully mounted but with no air in it. The only time that would happen is when I'm putting more sealant in and I'm too lazy to break the bead seal and look for boogers.
 
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