PDA

View Full Version : Air Ride: What to Buy (complete list)



veedubbin
07-19-2014, 06:58 AM
Hey folks. A while ago, when I first started becoming interested in air suspension, I spent lots of time scouring around for a complete list of pieces and parts needed for a full air suspension system. I found many threads saying I needed bags, a compressor, a manifold, and a tank. To me, that was worthless. I already knew the basics, I just wanted to make sure I didn't look over anything small.

I've spent the past couple of weeks putting together another kit, and I thought it would be beneficial to make a complete list of everything a person should need. The first time around, I used manual paddle valves because I was trying to go as cheap as possible. This time, I'm still trying to spend as little as possible, but I couldn't do the paddle valves again. They sucked. Running that much airline and being so slow was really stupid. So this time I went for the VU4.

Bagriders is a great place, with a lot of helpful people. I looked around and found out that they are also usually the cheapest and most reliable place to find the parts I needed. However, I did buy a few things off of Amazon and Ebay just because I couldn't justify spending more than I needed to for the same product. But make sure you remember that Bagriders does offer price matching.

I'm going to leave out the actual bags because it's really the only part of the puzzle that's specific to each car. But if you want to know, I'm going to use airlift's lifestyle universal struts.

Okay, enough of that. On to the list:

Manifold: I went with the VU4 from Bagriders (http://bagriders.com/modlab/products/VU4-4-CORNER-VALVE-KIT.html) because it's easy to install, reliable, small, and compact.

Compressors: I decided on dual 444c Viar compressors. I chose dual 444c because they are big enough to have a pretty short fill time, but also compact enough to hide away in my trunk. Amazon and Bagriders both have the same kits with the same parts included at about the same price. But I found a better option. I found a killer deal on eBay. Here's a dual 444c kit with the mounting hardware and filters like in the kits on Amazon and Bagriders, but they also throw in the relays, the pressure switch, AND A 5 GALLON TANK. That's right. And this kit only costs $329 with free shipping, $10 more than Amazon and Bagriders. And that brings me to the tank.

Tank: Included in the compressor kit above, is a free five gallon tank. A three gallon tank doesn't hold enough air, and a seven gallon tank is just too big to have in your trunk(in my personal opinion). This tank has nine fitting altogether. Some people may find that this is too many. I find that it is a nice number. I just wish that they had different sized ports but it really doesn't matter. The sizes of the nine ports are: (4x) 1/2 NPT along the face, (2x) 3/8 NPT one on both ends, and (3x) 1/4 NPT two on the left side and one on the underside for a drain.

Gauges: The best way to go without a doubt is the Triple Gauge Combo Kit from Bagriders (http://bagriders.com/modlab/products/TRIPLE-GAUGE-COMBO-KIT.html). Their kit includes almost everything necessary to install your gauges. The only things they don't provide is obviously a place to mount them considering every car's dashboard is different, and for my setup because of the port sizes on the tank, a fitting for the tank to send the pressure to the tank gauge(which I will go over in the fittings section). They even offer different colors of backlights for the gauges to match your instrument lighting in your car. I thought that was pretty cool.

Switchbox/Controller: I debated on buying a switchbox, or even making my own, but in the end I decided to go with four simple toggle switches. I bought a VU4 Wiring Harness from Amazon and four SPDT (on) off (on) toggle switches that you can get anywhere. For those of you who don't know, SPDT means Single Post Double Throw and (on) off (on) means momentary on - off - momentary on which means that the switch normally stays in the middle in the off position but you can toggle it two different directions to control two different things. In this case each switch controls the up and down functions for each corner. The wiring for this harness is pretty much straight forward. You attach each wire to it's correct post on it's correct toggle switch. There are also auxiliary wires to power the compressors. I will add a nice detailed diagram with exactly how to wire up the switches with the harness and how to add in the auxiliary wires for the compressors. Or maybe I won't. Maybe I'll forget.

Water Traps: Bagriders (http://bagriders.com/modlab/categories/MANAGEMENT/WATER-TRAPS/) offers a couple of really nice water traps. They are aesthetically pleasing and from what I've heard they work well. But once again, I went the cheaper way. I went on Amazon and ordered these. They are regulators/water traps but it really doesn't matter. The max pressure is 150psi, exactly like the traps from Bagriders. They aren't the best looking, but for my setup they will be hidden. Looks were the last thing I was worried about.

Leader Lines: Leader lines were included with the front struts I'm using, but I also wanted leader lines for the rears. Bagriders (http://bagriders.com/modlab/categories/OTHER-PARTS/LEADER-LINES/) has their leader lines, but I found mine on Amazon for a bit cheaper.

Air Line: I went for 3/8 line from Bagriders (http://bagriders.com/modlab/products/DOT-AIR-LINE.html). It's big enough to maintain high inflate/deflate speeds, but small enough to easily run through your car. I bought 50 feet just to have a little extra just in case. It's pretty cheap so it really doesn't hurt to buy extra.


Okay people, it's time for the fun part-

Like I said earlier, the tank has nine ports. Here is how they will be used:
1/2- Compressor input
1/2- Compressor input
1/2- Output to water trap/ manifold
1/2- Output to water trap/ manifold
3/8- Pressure switch
3/8- Cap/ inflation valve
1/4- Tank gauge
1/4- Cap
1/4- Drain cock

Fittings: I got all of my fittings from Bagriders (http://bagriders.com/modlab/categories/FITTINGS/). They had everything I needed so it was easier to get everything from them.

(4x) 3/8 PTC to 1/4 NPT(female) bulkhead (http://bagriders.com/modlab/products/SMC-DOT-BULKHEAD-FEMALE-STRAIGHT.html)- Between the leader lines and the 3/8 air line. I'll drill holes in the wheel wells and throw these there so it's a nice transition out of the wheel well and into the cabin of the car.

(8x) 3/8 PTC to 1/4 NPT(male) straight (http://bagriders.com/modlab/products/SMC-DOT-MALE-STRAIGHT.html)- Threaded into the manifold for the intake, exhaust, and out to the bags. I bought the VU4 with these fittings already installed, so I don't need to buy these. But if you buy the VU4 without them, then these are what you need.

(4x) 1/8 PTC to 1/4 NPT(male) straight (http://bagriders.com/modlab/products/SMC-MALE-STRAIGHT.html)- Threaded into the manifold for the readings on the gauges. These are included with the Triple Gauge Combo Kit. You will not have to buy these if you buy the kit.

(5x) 1/8 PTC to 1/8 NPT(female) straight (http://bagriders.com/modlab/products/SMC-FEMALE-STRAIGHT.html)- Threaded onto the back of the gauges. These are included with the Triple Gauge Combo Kit. You will not have to buy these if you buy the kit.

(1x) 1/8 PTC to 1/4 NPT(male) straight (http://bagriders.com/modlab/products/SMC-MALE-STRAIGHT.html)- Threaded into the tank. This is for the tank gauge. There is a 1/8 NPT(male) included with the Triple Gauge Combo Kit but for the tank I bought, I needed the 1/4 NPT.

(2x) 1/2 NPT(male) to 3/8 NPT(male) hex nipple (http://bagriders.com/modlab/products/HEX-NIPPLE.html)- Threaded into the tank and water trap. This goes to the watertrap. The watertrap is connected right to the tank in my setup.

(2x) 3/8 PTC to 3/8 NPT(male) straight (http://bagriders.com/modlab/products/SMC-DOT-MALE-STRAIGHT.html)- Threaded into the water trap. The line that goes into these go to the manifold.

(2x) 3/8 PTC to 1/4 NPT(female) straight (http://bagriders.com/modlab/products/SMC-DOT-FEMALE-STRAIGHT.html)- Threaded onto the leader lines coming off the compressors. The line that goes into these goes the the tank.

(2x) 3/8 PTC to 1/2 NPT(male) straight (http://bagriders.com/modlab/products/SMC-DOT-MALE-STRAIGHT.html)- Threaded into the tank. The line from the compressors goes into these.

(1x) 3/8 NPT(male) to 1/4 NPT(female) reducer bushing (http://bagriders.com/modlab/products/REDUCER-BUSHING.html)- Threads into the tank. The pressure switch supplied with my compressor/tank kit threads into this. The pressure switch included with mine is 1/4 NPT while most are 1/8 NPT so keep that in mind.

(1x) 1/4 NPT(male) hex plug (http://bagriders.com/modlab/products/HEX-PLUG.html)- Threaded into the tank. This is just a cap because you don't need this port.

(1x) 3/8 NPT(male) hex plug (http://bagriders.com/modlab/products/HEX-PLUG.html)- Threaded into the tank. This is just a cap because you don't need this port.
-OR-
(1x) 3/8 NPT(male) to 1/8 NPT(female) reducer bushing (http://bagriders.com/modlab/products/REDUCER-BUSHING.html)- Threads into the tank. This inflation valve (http://bagriders.com/modlab/products/NPT-INFLATION-VALVE.html) threads into the reducer. The inflation valve is used if your compressors give you problems and you need to charge your tank at a gas station or with another compressor.

(1x) 1/4 NPT(male) drain cock (http://bagriders.com/modlab/products/DRAIN-COCK.html)- Threaded into the tank. This is to drain the air from your tank if you need to do that for some reason.
-OR-
(1x) 1/4 NPT(male) safety valve (http://bagriders.com/modlab/products/SAFETY-VALVE.html)- Threaded into the tank. This is a valve that opens up at a certain pressure incase your compressors act up and decide they don't want to turn off. (Damn, thank you Sam)


Alright, so that's everything I'm using for my air setup. I hope this helps some of you to better understand the systems. Don't be afraid to go for air ride. It's super easy once you have it all figured out. If anyone has anything to add, please let me know.

In the future I plan to add more information for other management options.

Oh Damn, it's Sam
07-19-2014, 10:14 AM
Great info! I did notice you're missing one part I think is essential: a safety valve (http://bagriders.com/modlab/products/SAFETY-VALVE.html). If your pressure switch fails to shut down your compressors for any reason, the safety valve will open, preventing your tank from being filled beyond its rated pressure.

Are you looking at all for those of us with different equipment to post the details of our setups?

Alex@BagRiders
07-25-2014, 08:19 AM
Nice write up, I'm sure others will find this very helpful when piecing together their own air ride setups.

No need to buy from Amazon or Ebay in the future though! We'll price match them all day! :alright

TONY0305
07-26-2014, 07:02 PM
nice write up, i'm sure others will find this very helpful when piecing together their own air ride setups.

No need to buy from amazon or ebay in the future though! We'll price match them all day! :alright

oh nice i have seen some smc water traps from a different website would you guys price match them??

Alex@BagRiders
07-28-2014, 08:19 AM
oh nice i have seen some smc water traps from a different website would you guys price match them??

Of course! Just shoot me a PM or send us an email and we'll take care of you!

TONY0305
07-31-2014, 02:07 AM
Of course! Just shoot me a PM or send us an email and we'll take care of you!

Ok cool because I plan to use copper for my hardlines what ptc fitting work best??? I also might want to have flare fittings...what do you guys have that work good with copper??

Alex@BagRiders
07-31-2014, 08:48 AM
Ok cool because I plan to use copper for my hardlines what ptc fitting work best??? I also might want to have flare fittings...what do you guys have that work good with copper??

We have found that the SMC DOT ptc fittings (the ones with the inner sleeve to hold the line in place) work best for hardline setups. When it comes to the lines themselves, copper has more impurities than other metals so sometimes you won't get accurate bends. If you're set on the copper lines, they can definitely work fine but aluminum lines will be easier to work with overall.

We are working on adding some more compression fittings to our site. The ones we will be adding are stainless and do not require you to flare the ends. We have brass compression fittings on the site right now that work great and don't require flairing either.

TONY0305
08-15-2014, 08:16 PM
we have found that the smc dot ptc fittings (the ones with the inner sleeve to hold the line in place) work best for hardline setups. When it comes to the lines themselves, copper has more impurities than other metals so sometimes you won't get accurate bends. If you're set on the copper lines, they can definitely work fine but aluminum lines will be easier to work with overall.

We are working on adding some more compression fittings to our site. The ones we will be adding are stainless and do not require you to flare the ends. We have brass compression fittings on the site right now that work great and don't require flairing either.

ok so i was wondering if i could use a -6an male fitting and screw it onto my tank that has a 3/8 npt port? Is this possible?

Oh Damn, it's Sam
08-15-2014, 08:22 PM
-6AN won't thread to 3/8 NPT. -8 is closer, but you'll still need to adapt.

TONY0305
08-15-2014, 08:53 PM
-6AN won't thread to 3/8 NPT. -8 is closer, but you'll still need to adapt.

Thanks I think I figured out how I'm going to do my hardline setup thanks though

siopaolover
08-20-2014, 01:11 AM
Great info for those of us just starting to get into air suspension!

veedubbin
08-31-2014, 08:22 AM
Great info for those of us just starting to get into air suspension!

Thanks man. I'm hoping this helps at least a few people before it gets buried forever.

AnchorsAweigh
11-25-2014, 07:55 AM
Great info! I did notice you're missing one part I think is essential: a safety valve (http://bagriders.com/modlab/products/SAFETY-VALVE.html). If your pressure switch fails to shut down your compressors for any reason, the safety valve will open, preventing your tank from being filled beyond its rated pressure.

Are you looking at all for those of us with different equipment to post the details of our setups?

Yes. I've had my relay fail causing my compressors to remain on. This is crucial

meme405
01-02-2015, 12:30 PM
Just gonna bump this. To keep it present. I had found this when I was first looking into my air ride, and then between here and Air Society, I couldn't find it again.

There is really good information in here for anyone trying to plan their system, or anyone new to air.

Thanks OP.

Creation
01-28-2015, 08:31 AM
Thank you, as someone whose overwhelmed by air ride and trying to figure out his setup this really helped.

siopaolover
02-25-2015, 08:36 PM
Just bought my compressors, tank, bags, lines, and basically everything I need but fittings. Is that list of fittings above all the bagriders kit includes? And is that all I need?

Oh Damn, it's Sam
02-25-2015, 11:30 PM
Most Bag Riders kits come with the minimum of what you need for a basic install, minus the fittings for the bags themselves. Post up exactly what you've got and what you're wanting to do for an install, and we can work through what you need for fittings.

Alex@BagRiders
02-26-2015, 08:33 AM
Just bought my compressors, tank, bags, lines, and basically everything I need but fittings. Is that list of fittings above all the bagriders kit includes? And is that all I need?

If you are piecing everything together separately, the list of fittings the OP listed will not help you unless you are doing the exact same setup they have put together.

Choosing the right fittings for your setup depends on what tank you decided to go with, how many compressors, water traps, how you want your trunk setup to look, etc, etc.

siopaolover
02-27-2015, 03:01 PM
If you are piecing everything together separately, the list of fittings the OP listed will not help you unless you are doing the exact same setup they have put together.

Choosing the right fittings for your setup depends on what tank you decided to go with, how many compressors, water traps, how you want your trunk setup to look, etc, etc.

Thanks! I actually bought a Viair 444c, 5 gallon 9 port tank, Airlift Dominator D2500, 3/8" line, and I'm about to buy a 3/8" SMC water trap and 2 3/8" valve manifolds, and I'm trying to piece together what I need. I'm just going for a basic air setup with nothing fancy in the trunk

Oh Damn, it's Sam
02-27-2015, 03:13 PM
IIRC D2500s have 1/2" FNPT ports, so if you're going to run nylon air line right to the bags (i.e. not use a braided leader hose), 4x 3/8" PTC to 1/2" MNPT fittings will do you fine. If you need elbows to fit the lines in (might be helpful in the rear), the SMC swivel elbows that Bag Riders sells are excellent.

Which valve manifolds did you purchase, and which tank?

siopaolover
02-27-2015, 03:47 PM
IIRC D2500s have 1/2" FNPT ports, so if you're going to run nylon air line right to the bags (i.e. not use a braided leader hose), 4x 3/8" PTC to 1/2" MNPT fittings will do you fine. If you need elbows to fit the lines in (might be helpful in the rear), the SMC swivel elbows that Bag Riders sells are excellent.

Which valve manifolds did you purchase, and which tank?

Yessir! They are 1/2" ports. So I'll put in an order for 4 of these, right?
http://bagriders.com/modlab/products/SMC-DOT-UNEQUAL-UNION.html

And 2 of these 3/8" to 3/8" for the rears:
http://bagriders.com/modlab/products/SMC-DOT-SWIVEL-ELBOW.html

For reference, here's the compressor, tank, and bag kit I bought:
http://www.ebay.com/itm/Viair-444C-Chrome-Dual-Compressor-D2500-Airlift-5-gallon-Air-Tank-Ride-Bag-kit-/381172003136?vxp=mtr

And these are the valves I'll be using:
http://www.ebay.com/itm/201244205848?_trksid=p2060778.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Oh Damn, it's Sam
02-27-2015, 04:10 PM
Yessir! They are 1/2" ports. So I'll put in an order for 4 of these, right?
http://bagriders.com/modlab/products/SMC-DOT-UNEQUAL-UNION.html

And 2 of these 3/8" to 3/8" for the rears:
http://bagriders.com/modlab/products/SMC-DOT-SWIVEL-ELBOW.html

You'll want two of these (http://bagriders.com/modlab/products/SMC-DOT-MALE-STRAIGHT.html) in 1/2" MNPT and 3/8" PTC for the front and two of the swivel elbows you've got listed there for the rear, but the swivel elbows will want 1/2" MNPT threads, not 3/8".


For reference, here's the compressor, tank, and bag kit I bought:
http://www.ebay.com/itm/Viair-444C-Chrome-Dual-Compressor-D2500-Airlift-5-gallon-Air-Tank-Ride-Bag-kit-/381172003136?vxp=mtr

Aha, twin compressors. You'll also want twin water traps. Sounds like you got the 3/8" SMC trap, which is my favorite of what Bag Riders carries, so get one more of those. You'll also need 2x 1/4" FNPT to 3/8" MNPT bushings to adapt the 1/4" threads on the leader hose to the 3/8" threads on the water traps.

I don't see anywhere in that listing what the port sizes are on the tank. If you know, post it up, otherwise once it arrives we can figure it out, and go from there.


And these are the valves I'll be using:
http://www.ebay.com/itm/201244205848?_trksid=p2060778.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

You'll need two more of those valve blocks to handle four corners. One valve on each block is fill and one is dump, so you need eight valves total in four blocks. Personally, were it me, I'd think long and hard about upgrading to a VU4 manifold. They're more expensive, but they're beautifully made and switching to a VU4 will save you a LOT of screwing around.

If you're intent on making those valve blocks work, it can absolutely be done, I just wanted to throw another option out there for you.

EDIT: While we're at it, you need to be sketching out how you want the trunk laid out and where you want to run lines.

siopaolover
02-28-2015, 02:07 PM
You'll want two of these (http://bagriders.com/modlab/products/SMC-DOT-MALE-STRAIGHT.html) in 1/2" MNPT and 3/8" PTC for the front and two of the swivel elbows you've got listed there for the rear, but the swivel elbows will want 1/2" MNPT threads, not 3/8".



Aha, twin compressors. You'll also want twin water traps. Sounds like you got the 3/8" SMC trap, which is my favorite of what Bag Riders carries, so get one more of those. You'll also need 2x 1/4" FNPT to 3/8" MNPT bushings to adapt the 1/4" threads on the leader hose to the 3/8" threads on the water traps.

I don't see anywhere in that listing what the port sizes are on the tank. If you know, post it up, otherwise once it arrives we can figure it out, and go from there.



You'll need two more of those valve blocks to handle four corners. One valve on each block is fill and one is dump, so you need eight valves total in four blocks. Personally, were it me, I'd think long and hard about upgrading to a VU4 manifold. They're more expensive, but they're beautifully made and switching to a VU4 will save you a LOT of screwing around.

If you're intent on making those valve blocks work, it can absolutely be done, I just wanted to throw another option out there for you.

EDIT: While we're at it, you need to be sketching out how you want the trunk laid out and where you want to run lines.

Thanks!

So just to clarify, I'll need both PTC and NPT to be 1/2" for the swivel elbows, right?

And I'll actually just be running one compressor. I'm giving the other compressor to a friend as sort of a way to repay him for helping me with install :o

Everything is coming in today, so I'll update you guys on the tank when it gets here!

Also, I'm just looking at running front/back instead of FBSS. Would the VU2 be a pretty good option for me at this point? And save me the headache of running those valve blocks?

Oh Damn, it's Sam
02-28-2015, 10:47 PM
The PTC size is the size of your air lines. Since you have 3/8" lines, you need fittings with 3/8" PTC ends. The swivel elbows you will want are threaded 1/2" MNPT (since the bags have 1/2" FNPT ports) with 3/8" PTC ends to allow your lines to connect.

Tying your left and right corners together is an unsafe hack. You need to keep your corners isolated from each other in order to prevent side-to-side airflow during cornering. This will require a manifold like the VU4 or similar, eight electric valves, or four paddle valves.

siopaolover
03-01-2015, 04:35 AM
The PTC size is the size of your air lines. Since you have 3/8" lines, you need fittings with 3/8" PTC ends. The swivel elbows you will want are threaded 1/2" MNPT (since the bags have 1/2" FNPT ports) with 3/8" PTC ends to allow your lines to connect.

Tying your left and right corners together is an unsafe hack. You need to keep your corners isolated from each other in order to prevent side-to-side airflow during cornering. This will require a manifold like the VU4 or similar, eight electric valves, or four paddle valves.

Got it! Thanks again, Sam. Looks like UPS isn't delivering until Monday, so I'll update when everything comes in

EDIT: Can I run these valves instead?
http://www.ebay.com/itm/AIRLIFT-25009-AUTO-PILOT-MANIFOLD-VALVE-/221389168380?pt=Motors_Car_Truck_Parts_Accessories&hash=item338bd29efc&vxp=mtr

Oh Damn, it's Sam
03-01-2015, 03:39 PM
EDIT: Can I run these valves instead?
http://www.ebay.com/itm/AIRLIFT-25009-AUTO-PILOT-MANIFOLD-VALVE-/221389168380?pt=Motors_Car_Truck_Parts_Accessories&hash=item338bd29efc&vxp=mtr

Yes, but you'll need two blocks. At that price, get a RidePro manifold, save up another $100 for a VU4, or save yourself $150 and just use individual SMC valves.

siopaolover
03-01-2015, 11:07 PM
Yes, but you'll need two blocks. At that price, get a RidePro manifold, save up another $100 for a VU4, or save yourself $150 and just use individual SMC valves.

I think I'll just save up a few more weeks and buy the VU4 :D Is it more of a straightforward install with the VU4?

Oh Damn, it's Sam
03-01-2015, 11:11 PM
It's a bit more straightforward. The PTC VU4 saves you half a dozen to a dozen NPT-PTC fittings versus a traditional valve block. If you're going to have leaks, it's going to be on NPT fittings, so the more you can cut out of your setup, the better.

siopaolover
03-03-2015, 12:47 AM
It's a bit more straightforward. The PTC VU4 saves you half a dozen to a dozen NPT-PTC fittings versus a traditional valve block. If you're going to have leaks, it's going to be on NPT fittings, so the more you can cut out of your setup, the better.

Thanks again for the info. I hope other people interested in air suspension find all this useful too!

UPDATE: compressors, bags, and tank came in today :eyebrows
https://farm9.staticflickr.com/8588/16079039364_dbf316480f_c.jpg (https://flic.kr/p/quRhdC)image (https://flic.kr/p/quRhdC) by fbaladad (https://www.flickr.com/people/93420847@N05/), on Flickr

https://farm9.staticflickr.com/8606/16081937663_0a5e41261d_c.jpg (https://flic.kr/p/qv78Mi)image (https://flic.kr/p/qv78Mi) by fbaladad (https://www.flickr.com/people/93420847@N05/), on Flickr

siopaolover
03-13-2015, 04:22 PM
Just bought my VU4 yesterday from a member on vwvortex :D

Quick question though... How do you guys power everything??

Oh Damn, it's Sam
03-13-2015, 04:34 PM
Your switch setup will want 12+ ignition or 12+ constant depending on whether you want the ability to air down with the car off.

You'll need to run 12+ ignition power to the trunk, pass it through your pressure switch, and run it to the trigger pin on your compressor relay.

You'll also run a fused cable from the battery that's capable of handling 30A. This'll run to the power pin on your relay. The output pin will then feed the compressor power.

The VU4 just receives input from the switchbox, and then is grounded. It doesn't need power of its own.

Motoman325
05-18-2015, 11:06 PM
I got a question. i'm still planning out everything, I wanna run fbss, do i need 4 pressure sensors for gauges or can i do one for front and one for back?

Oh Damn, it's Sam
05-19-2015, 08:13 AM
You'll need a separate sender for each line. There are ways to use a single sender to average the pressures for two or more lines, but it involves using diaphragm isolators and so forth.