Bridgestone/Praxis Suspension System
07-10-2003, 09:45 AM
#16
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When will this be available, and what will be the approximate cost. This sounds like a good system. What is the reliability like on the air junctions. If it is just a hose clamp it seems as though you could run into some serious problems. I have a 1967 GTO with air shocks, and when there was a leak in them and all the air got out it was bad news. I am just wondering how high the probability of this happening on this system is.
Stephen
Stephen
07-10-2003, 10:07 AM
#17
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The system should be available early August - we plan on offering it for $3450, which includes everything you need to get up and running minus a set of tools. No hose clamps - the air fittings are industrial grade "press fit" type - same as used on semi-truck airbrakes. The hoses do not leak and can only be removed by "unlocking" the fitting. I was skeptical as well, so I did some of my own tests - I couldn't twist or pull out the tube from the connector. I'd consider it a trustworthy setup.
Last edited by Dexter@tirerack; 07-11-2003 at 12:27 PM.
07-10-2003, 11:34 AM
#18
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Here are some thoughts and impressions on the system overall:
*Compressor - the compressor only seems to run at startup - to recharge the tank to 100PSI. I never heard it run on the road, even after a few ups and downs but the engineer said it might. This worried me because the compressor on my car was a bit loud. He then showed me the production compressor mounting and it's rubber fittings. After hearing this newer version on another car we have here, it is absolutely different than the one on my test car. I don't think you would even be able to hear the new version of the compressor, especially with the engine running.
*Leveling - this feature is another nice side effect of and air suspension system. Ever pulled a trailer and seen the tail of the car drop? Got any "jolly" friends that may be embarassed by the tilt of the car once they get in? As you can guess - the system compensates for these imbalances and keeps the car level.
*Air tank - stores between 80 and 100PSI - and can be used to fill tires with dry air. A nice side effect of the system. You can set up the hose yourself or they'll be selling an optional connector/hose.
*Air dryer - this is a considered a lifetime unit. I had trouble with this because dryers tend to get wet over time. It turns out that it stays dry by venting the dry air through the same unit as the struts deflate. This dry air leaving the unit absorbs the wetness in the dryer and carries it away. Good thinking.
*Spring angle - a strut, unlike a shock, acts as the upper control arm of the suspension. This means that it is not only seeing vertical forces (or forces parallel to the shaft), but lateral (sideways) as well. The area where these stresses are noticed is the interface or seal between the shaft and the body of the strut. Ever noticed how the springs on the WRX aren't in line with the strut shaft? This is to help cut down on the lateral load felt by the seal. This is duplicated (even to a bit larger extent) on the Praxis struts. This decrease in the load on the seal adds to longevity as well as decreases the force needed to overcome the friction between the seal and the shaft - allowing for more responsive damping.
More to come as questions arise and I get more time to experiment with the car...
*Compressor - the compressor only seems to run at startup - to recharge the tank to 100PSI. I never heard it run on the road, even after a few ups and downs but the engineer said it might. This worried me because the compressor on my car was a bit loud. He then showed me the production compressor mounting and it's rubber fittings. After hearing this newer version on another car we have here, it is absolutely different than the one on my test car. I don't think you would even be able to hear the new version of the compressor, especially with the engine running.
*Leveling - this feature is another nice side effect of and air suspension system. Ever pulled a trailer and seen the tail of the car drop? Got any "jolly" friends that may be embarassed by the tilt of the car once they get in? As you can guess - the system compensates for these imbalances and keeps the car level.
*Air tank - stores between 80 and 100PSI - and can be used to fill tires with dry air. A nice side effect of the system. You can set up the hose yourself or they'll be selling an optional connector/hose.
*Air dryer - this is a considered a lifetime unit. I had trouble with this because dryers tend to get wet over time. It turns out that it stays dry by venting the dry air through the same unit as the struts deflate. This dry air leaving the unit absorbs the wetness in the dryer and carries it away. Good thinking.
*Spring angle - a strut, unlike a shock, acts as the upper control arm of the suspension. This means that it is not only seeing vertical forces (or forces parallel to the shaft), but lateral (sideways) as well. The area where these stresses are noticed is the interface or seal between the shaft and the body of the strut. Ever noticed how the springs on the WRX aren't in line with the strut shaft? This is to help cut down on the lateral load felt by the seal. This is duplicated (even to a bit larger extent) on the Praxis struts. This decrease in the load on the seal adds to longevity as well as decreases the force needed to overcome the friction between the seal and the shaft - allowing for more responsive damping.
More to come as questions arise and I get more time to experiment with the car...
Last edited by Dexter@tirerack; 07-11-2003 at 12:26 PM.
07-10-2003, 12:41 PM
#19
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what sort of damping ranges are going to be available? you mentioned that you drove the car set to one damping setting at all three ride heights. is the system pre-set with damping rates, allowing you to change the rate to match the ride height, or is it adjustable in finer increments to suit individual drivers? are there going to be reccomended rebuild intervals?
07-10-2003, 01:23 PM
#20
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The struts have 6 clicks per revolution - and there are about two revolutions between full tight and full loose. Any level can be used in any damping mode, but they're listed "touring, track, and sport."
Last edited by Dexter@tirerack; 07-11-2003 at 08:00 AM.
07-10-2003, 05:54 PM
#21
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Yeah the rebuild issue seems like a good one to tackle. What are the recommended rebuild times? It seems like a pretty involved system as well. What extent will a car have to be drilled/holed/permanently disfigured 
to get the install. And is it something that can be done in a weekend. As being without a car for days during the week is pretty tough.
THanks
Stephen
to get the install. And is it something that can be done in a weekend. As being without a car for days during the week is pretty tough.THanks
Stephen
07-10-2003, 06:31 PM
#22
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my guess is that the modifications to the chassis and interior will be pretty minimal. Dexter mentioned that the compressor mounts inside/under the fender well (it's got to be relatively small, what 3-5 gallons max?) and that the valving and 'brain' would mount in the trunk. I'm guessing that lines will need to be run from the compressor to the trunk, and to all the air bags underneath the car. that could probably be accomplished with hose clamps, which means you're left mounting the compressor and control unit, and punching some holes to get the lines in, and wiring he controls to the driver's area.
given the target market, Bridgestone/Praxis aren't going to be able to sell it if the permanent modifications to the care are too great. people willing to pay for this sort of adjustability aren't going to be too excited about drilling holes, cutting chunks of their car, and generally making heavy modifications to their vehicle. racers and track junkies do that, but they're probably not as interested in this system as well off auto-x'ers who drive to work five days a week.
it sounds to me like it's going to be a ten hour job for a professional to two, and that anyone doing it in their own garage ought to plan on two full days for the install.
i think that the rebuild issue is going to be a big deal. if the rebuild interval is too frequent, people are going to get sick and tired of pulling things apart and putting them back together. given, it won't take as long the second or third time arround, but i'm guessing it'll take longer than doing it for coilovers.
it's really too bad that Bridgestone/Praxis weren't able to come up with a way to control the damping from the cockpit. with the adjustable ride height, it would be a huge benefit. maybe they'll offer it at a later date as some sort of premium add-on, like Tein's EDFC.
given the target market, Bridgestone/Praxis aren't going to be able to sell it if the permanent modifications to the care are too great. people willing to pay for this sort of adjustability aren't going to be too excited about drilling holes, cutting chunks of their car, and generally making heavy modifications to their vehicle. racers and track junkies do that, but they're probably not as interested in this system as well off auto-x'ers who drive to work five days a week.
it sounds to me like it's going to be a ten hour job for a professional to two, and that anyone doing it in their own garage ought to plan on two full days for the install.
i think that the rebuild issue is going to be a big deal. if the rebuild interval is too frequent, people are going to get sick and tired of pulling things apart and putting them back together. given, it won't take as long the second or third time arround, but i'm guessing it'll take longer than doing it for coilovers.
it's really too bad that Bridgestone/Praxis weren't able to come up with a way to control the damping from the cockpit. with the adjustable ride height, it would be a huge benefit. maybe they'll offer it at a later date as some sort of premium add-on, like Tein's EDFC.
07-11-2003, 03:11 AM
#23
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I'm also more than a little disapointed that the damping is only one way adjustable and that there are only three settings. No matter how ell they did their research, a little fine tunning will be necessary. At $3,500 to $3,800 they must be charging an awful lot for the R&D, because at this point I'm not seeing it in the Hardware.
07-11-2003, 08:45 AM
#24
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Great questions - I fixed the "damping adjustments" post to reflect the truth. I originally misunderstood the engineer in his explanation of the way it was set. There are six clicks per revolution, and about two revs available. So, you have many more options in damping levels.
Rebuild: The shocks can be rebuilt if necessary, but they will need to be sent to H&R for service. The engineer doesn't estimate a rebuild necessary for a number of years outside of failure of the damper itself. This is more believable now that I know there are numerous levels of adjustment to the damper. The damper actually disassembles from the air unit quite easily - there are a few o-rings at the base and three bolts, then removal from the mount on the top.
Modifications: Next to none - the car can be brought back to stock without question. Everything is custom made for the WRX - Strut mounts, brackets, wiring, etc. The wiring uses existing access points for passage. The only drilling required is 4 holes in the two bars behind the back seats of the sedan to mount the tank in the trunk.
Installation: Yes, it will take time. If you can change brake rotors and install a subwoofer, you can do it. I would estimate a total of 10-12 hours novice, 7-10 professional. The most time consuming part is running the air hoses and wiring, as the struts are a drop-in fit.
Rebuild: The shocks can be rebuilt if necessary, but they will need to be sent to H&R for service. The engineer doesn't estimate a rebuild necessary for a number of years outside of failure of the damper itself. This is more believable now that I know there are numerous levels of adjustment to the damper. The damper actually disassembles from the air unit quite easily - there are a few o-rings at the base and three bolts, then removal from the mount on the top.
Modifications: Next to none - the car can be brought back to stock without question. Everything is custom made for the WRX - Strut mounts, brackets, wiring, etc. The wiring uses existing access points for passage. The only drilling required is 4 holes in the two bars behind the back seats of the sedan to mount the tank in the trunk.
Installation: Yes, it will take time. If you can change brake rotors and install a subwoofer, you can do it. I would estimate a total of 10-12 hours novice, 7-10 professional. The most time consuming part is running the air hoses and wiring, as the struts are a drop-in fit.
Last edited by Dexter@tirerack; 07-11-2003 at 09:28 AM.
07-11-2003, 09:13 AM
#25
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Is there an estimate on mileage for a rebuild. I know it will be totally subjective as to what kind of driving they see. But if I were to run track 1-3 times a month and then used it as daily driver, what kind of mileage could I expect out of them before a rebuild. Because not being able to rebuild them yourself will be a huge hassle. The system sounds nice, but I would prefer to be able to sit and rebuild them myself for the sake of not being without a car for a few days/week.
Stephen
Stephen
07-11-2003, 04:20 PM
#28
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In order:
No official mileage estimate on rebuild. I should be able to get a better answer on Tuesday. I'm expecting at least 100k miles of aggressive driving, as that's what H&R products traditionally expect.
Mules? They're very responsive to Subaru events. Do you know of any events that they should know about? They might not be able to drop by your house, but a nearby event might get the thumbs-up.
Update to my driving experience:
Last night I had some more time to play with the system. I wanted to get the best it had to offer on an otherwise stock car. So, I rolled under the car and tightened the damping. The struts on my test car aren't the production models, so I had to use a little key to do the adjustments. The production models have attached handles that can be adjusted quickly - which will be a nice upgrade...
The front adjustments were easy - even with hot brakes. The rears were a bit trying, with the lower front arm in the way. After dropping the key a few times I rolled around back and got it done quickly. Again, the attached keys will make this a 2 minute job.
After my initial drive, as well as 60 miles on the way to work today, I decided that the suggested "track" settings on the struts are for me. I've been stuck in my own "ultra touring" mode for 50k miles on my wagon. I'm tired of it. The ride at "touring" height in "track" damping is nice on the highway.
"Sport" height is perfect for spirited around the town driving. I put it in this mode when I came up on the usual corners that embarass me in the wagon with the front tires whining. Understeer is significantly reduced in this and "track" modes.
The "track" height is even acceptable on smooth roads, but not rough roads. The car is glued to the ground like I've never felt on a WRX. Sway is significantly reduced, and the car feels and looks like an autocrosser.
Thoughts:
Yes - servo controlled damper adjustments would be easier - but would add about $1k to the system, as well as some more unspring weight (the air struts weigh 2.5lbs. less front and .5lbs. less rear btw). I would likely keep the dampers between "sport" and "track" recommendations for everything but race day. This setting feels great in my opinion.
These struts are quiet. I've noticed some high performance struts and coilovers are sometimes a bit noisy. I've found the air struts to be quieter than stock; especially over big bumps and RR crossings.
I would like to try the system with an upgraded set of sway bars. Even with the huge difference in handling, I think a swaybar would be the icing on the cake to punish the car's desire to roll. The roll was significantly reduced; especially when I tightened the dampers. Even the best dampers, though, can't focus on stopping sway as well as a less-compliant sway bar.
No official mileage estimate on rebuild. I should be able to get a better answer on Tuesday. I'm expecting at least 100k miles of aggressive driving, as that's what H&R products traditionally expect.
Mules? They're very responsive to Subaru events. Do you know of any events that they should know about? They might not be able to drop by your house, but a nearby event might get the thumbs-up.
Update to my driving experience:
Last night I had some more time to play with the system. I wanted to get the best it had to offer on an otherwise stock car. So, I rolled under the car and tightened the damping. The struts on my test car aren't the production models, so I had to use a little key to do the adjustments. The production models have attached handles that can be adjusted quickly - which will be a nice upgrade...
The front adjustments were easy - even with hot brakes. The rears were a bit trying, with the lower front arm in the way. After dropping the key a few times I rolled around back and got it done quickly. Again, the attached keys will make this a 2 minute job.
After my initial drive, as well as 60 miles on the way to work today, I decided that the suggested "track" settings on the struts are for me. I've been stuck in my own "ultra touring" mode for 50k miles on my wagon. I'm tired of it. The ride at "touring" height in "track" damping is nice on the highway.
"Sport" height is perfect for spirited around the town driving. I put it in this mode when I came up on the usual corners that embarass me in the wagon with the front tires whining. Understeer is significantly reduced in this and "track" modes.
The "track" height is even acceptable on smooth roads, but not rough roads. The car is glued to the ground like I've never felt on a WRX. Sway is significantly reduced, and the car feels and looks like an autocrosser.
Thoughts:
Yes - servo controlled damper adjustments would be easier - but would add about $1k to the system, as well as some more unspring weight (the air struts weigh 2.5lbs. less front and .5lbs. less rear btw). I would likely keep the dampers between "sport" and "track" recommendations for everything but race day. This setting feels great in my opinion.
These struts are quiet. I've noticed some high performance struts and coilovers are sometimes a bit noisy. I've found the air struts to be quieter than stock; especially over big bumps and RR crossings.
I would like to try the system with an upgraded set of sway bars. Even with the huge difference in handling, I think a swaybar would be the icing on the cake to punish the car's desire to roll. The roll was significantly reduced; especially when I tightened the dampers. Even the best dampers, though, can't focus on stopping sway as well as a less-compliant sway bar.
Last edited by Dexter@tirerack; 07-11-2003 at 04:43 PM.
07-11-2003, 07:09 PM
#29
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Man, Dexter, you are a hell of a sales man. Everytime I read your posts this set up sounds more and more gnarly. When they come out I am going to have a hard time not breaking my wallet for them. I have been looking for a good setup for a while now. It was between DMS 40mm, JIC's, or Ledas. But if these really handle, and have the ease of adjustment that you say, I can really see that this will be a really nice setup. But hearing what happens after you add sways would be nice. Also, what tires do you have on the car? Are they super sticky or just some decent speed rated?
Stephen
Stephen
07-12-2003, 08:00 AM
#30
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Ha, don't know about that. The car has SSR Comps in 17x7.5 with 225 S-03s on them - which offer great traction. I use the same wheels on my wagon with same sized Sumitomo HTR+ - so some thoughts on the possible skewing of MY impressions of the system due to wheels/tires:
The S-03s are at 34psi - I run my sumitomos at 40psi. Tire to tire, initial responsiveness is similar (helped by psi difference), but the traction limit on the S-03 is superior no doubt. Smoothness between the two is similar, again because I run at 40psi on my car. Overall - I don't think the impression of the system is affected by the difference in tire.
The S-03s are at 34psi - I run my sumitomos at 40psi. Tire to tire, initial responsiveness is similar (helped by psi difference), but the traction limit on the S-03 is superior no doubt. Smoothness between the two is similar, again because I run at 40psi on my car. Overall - I don't think the impression of the system is affected by the difference in tire.