Mountain Bike Reviews Forum banner

1 - 15 of 15 Posts

·
Registered
Joined
·
186 Posts
Discussion Starter · #1 · (Edited)
Hi,

First of all sorry my english (I'm portuguese). And then, sorry if it is a repost or in wrong place.

I'm interested in making a home-made "ghetto" Procore system, and I will share with you my idea to discuss a possible home-made version.

I have 26" rims (ERTRO: 21-559) on my DH bike.

1) The idea is to use a clincher road tire, for instance, the Schwalbe Insider (ETRTO: 23-559, price 15€ euros, 210grams, 145 psi max pressure).

Schwalbe-Insider-Performance-Trainings-Faltreifen-61069eb151450b3b1625c843f01d11d0.jpeg

$_3.jpg

Insider | Schwalbe North America



2) Do a small hole in the road Insider tire. Something like this:

p4pb11345291.jpg


3) Them, drill a 2nd hole in the rim (my rim is cheap and has already 37 holes, 36 from spokes +1 from valve, so no big problem). Put a 2nd air valve in the rim. Seal the valve holes and rim with tape to be tubeless-ready and avoid air leaks.


4) Put a road air chamber inside the Insider tire, like this:
1691793-c93stmh4aalg-schwalbe_2-large.jpg


5) Install the Insider and the skinny air tube, and then the main tire (in my case a 2-ply BigBetty tire) with liquid sealant. When finished should look like this:
dual-performance.jpg


6) The first valve is from the skinny air tube. The 2nd valve fills the air inside the Insider tire (but outside of the air tube). So, when inflating the 2nd valve, the air goes to the Insider tire and passes through the hole in the insider tire inflating the main tire [see point 2)]. A picture from moto tubliss system to help visualizing the ideia:

tubliss-chamber.jpg

7) After inflating the main tire (1.5 Bar), inflate the inner air tube (1st valve) to ~ 6 Bar.


8) I think this system is similar to the first Procore prototype with 2 air valves. The main "problem" comparing to final Procore, is that you have to drill a 2nd hole (not a big deal for me, at least). The second minor issue is that you may need to deflate the insider tube temporarily in order to adjust the main tire pressure (because if the insider pressure is too high, the air from the 2nd valve will not pass-by the tube and escape from the hole in the inner tire). A 3rd minor issue is that you have to seal well the valve's holes to avoid air leaks (probably an o-ring between the rim and the Presta valve nut will work, or something like that). After the Insider tire being inflated to 6bar, there is no big problem for air leaks from the main tire through the valve's holes.

tube7.jpg


This system will cost about 20 euros per wheel (almost 10-times less than the original). It's cheaper, and I don't think that the disadvantages are very relevant.


An alternative method of this, is to use a road tubular 26" tire. The problem of this method is that a tubular tire is not a clincher tire, so it will not fit so wheel in the rims. Also a tubular tire is a bit more expensive.


What do you think ?

Greetings,
Andre
 

·
Registered
Joined
·
1,705 Posts
Nice. That is what I was thinking too. I figured someone was going to figure out something. Someone else suggested a tubular tire to me also. It would seem like the tubular tire would be good because there isn't 2 components to install (tire + tube) and only the tire itself. The tubular tire looks like it would work in theory but I don't have experience with it.

My issue with the Procore is the weight and price because you are adding a pound of weight to your bike. However, if it saves your tires and rims from being destroyed by snakebites then the cost looks better.

What is the weight addition?
 

·
Registered
Joined
·
186 Posts
Discussion Starter · #3 ·
A tubular tire will work in most cases, especially in non super-wide rims. However it is not the best solution because a tubular tire do not have the beads to fit in the rim. Moreover, a tubular tire does not expand laterally so well. Tubular tires have a fixed width (like 22mm for instance). In a ultra-wide rim (eg: 30mm inner width) the tubular tire will not expand enough to promote the proper fixing of the main tire. With a normal clincher road tire you will be on the safe side, and have the same performance as the original Procore. Moreover, its easier to find a clincher road tire with your wheel dimensions. And it can be cheaper.

Regarding the weight, "my" ghetto procore will add about 300grams (0.66 lbs). You will always gain weight with this system, except if you do DH an run heavy-duty DH tubes like me (my maxxis DH tube weights 490gr ~ 1.1 lbs). In that cases you lose weight (200gr ~ 0.4 lbs). Also, if you run 2-ply tires with tubes only to avoid pinch flats, you can go single-ply with this.

Here it is a sketch of "my" ghetto system. It is in Portuguese, later I will put an english version. But I think it's easy to understand.


SemTiacutetulo_zpsdd904d4e.png

LEFT (1st Step): Cross-view of the system centered on 2nd valve
RIGTH (2nd Step): Cross-view of 1st valve (the inner tube valve).
 

·
Registered
Joined
·
1,705 Posts
I like the Schwalbe Procore system and think it is well design, but I also really like to build things and create new solutions for things. So, I may experiment some. Haha.
 

·
Registered
Joined
·
186 Posts
Discussion Starter · #5 ·
I also like to create things. The original system is way toooo expensive (almost 10 times more) and is only available in 2015.
 

·
Registered
Joined
·
186 Posts
Discussion Starter · #6 ·
The english version of the sketch.

Apresentação1.jpg

An improvement to the original ideia:

Use duct tape to wrap around the tube (only just above the 2nd valve and below the Insider tire hole) to limit its expansion when inflated. By reducing the diameter of the tube in that area (4cm length is enougth) you create a open space that allows the air to flow freely between 2nd valve / hole / external chamber. With this trick you can inflate both chambers independetly. Meaning that you can inflate inner chamber first and then external chamber
 

·
Registered
Joined
·
186 Posts
Discussion Starter · #7 ·

·
Registered
Joined
·
1,705 Posts
Looks like the DeanEasy guy invented it before Schwalbe. His videos are pretty convincing of how well it works and how it locks the bead on the rim. To me the tubular tire looks like a good way if you can find a lightweight tubular tire.
 

·
Registered
Joined
·
171 Posts
Tried to get a tubular inside a tubeless tires. Mounting was a b!tch and I gave up.
You have to make sure the tubeless bead goes under the tubular and inside the rim's center channel, pushing it with the help of a tire lever. It's even harder with UST rims, but I've done it. Anyway, in my opinion the profile of a UST rim also makes it more difficult for the tubular to lock the bead against the rim wall when inflated, better to use the tire and tube method.
 

·
Registered
Joined
·
397 Posts
ghetto procore

Vittoria makes a 650 road tubular for those now running 650b/275 wheels, I plan on making this happen over the winter....
To run ghetto with a 26in tyre (559), you need to use a 700c tubular.
26in tubular is designated as 650c (as mentioned above Vettoria do one).
But if you use a 650c, it will be tight in the middle of the rim when deflated, and make it extremely hard to mount the standard tubeless tyre over the top.

Using a 700c gives it enough slack to allow easy mounting of the outer tyre, but also allows the tubular to inflate and expand back to the rim and provide the essential support against the bead.

You are limited to using tubulars that are as near to the inner width of your rim as possible. (22mm will work fine on rims upto 24mm ID)

There are also a lot of available tyres to choose from, including indoor track only tyres which will minimise the weight penalty. (some as light as 150g!)


Scar
 

·
Registered
Joined
·
54 Posts
Good post scar4me!
700c tubulars might be solution for problems that occured to me with mounting tubeless tire with inner clincher tire/tube combo to 21mm ID rim. I simply couldn't make tubeless tire bead to seat because insider tire filled all the space in central channel.

Just two more questions:
1. What is inner diameter of the rim you've been using?
2. can you recommend tubeless tire that is optimal regarding weight/price ratio?

thanks!
 

·
Registered
Joined
·
397 Posts
26in Light-Bicycles Wide AM Rim (the original) 30mm OD, Rim ID 23.5mm.
I've done it ok with some 23mm road tubulars, but TBH I'm looking at trying a cheap 32mm CX tubular tyre n cutting off the tread.
Slightly heavier, but gives a much better internal chamber volume.


Scar
P.s. I use a fine needle mounted in a presta\schrader convertor on my track pump to inflate the main chamber, and just let the sealant seal it up after :)
 
1 - 15 of 15 Posts
Top