Determining Best Tire Pressure

[KosherKid]

Not the same old subject.

Most advice is to start with posted pressure for your Spyder and go from there.

What criteria do you experts use to determine the change in pressure needed. I'm using the Quatrac 5 on the fronts and Kumho AST on the rear.

I have tried several pressure settings from 15 to 20 for the front and 18 to 26 for the rear and can not really feel that much of a difference. What should I be looking for or feeling for? I now there is no hard and fast rule but I could use some advice.

Thanks for any help.
Dave

 

[BLUEKNIGHT911]

As you may know I ( & Peter Aawen ) have had actual training that included pressures in tires, and what effect they have on traction in both wet & dry , hot & cold conditions …. for practical, real use purposes, the Perfect PSI doesn't exist. …. Why ? - conditions are constantly changing … What myself and ( I believe ) Peter have always used in our estimations is an average number based on the current properties of 95% of tires made for veh's. ( cars mostly ). " Perfect " is what people who regularly drive at 200 + mph, in veh's designed to use that speed, on surfaces designed to permit that speed. However Perfect is not practical ( or necessary ) in real life driving… We have taken into account the design and specs of those tires, and applied proven principles to give a fairly accurate estimation of what works best for tires we use on our Spyders. A lot of folks don't realize that a tire is also an integral part of the over-all suspension system. A PSI that will achieve maximum handling, is going to effect the ride feel in a negative way, for most folks. Just like racing shocks/springs may improve handling, they won't give 95% of the riders a comfortable ride … If I'm just cruising on my RT, I would use ( Note: nothing I have , or will say, applies to Kenda's or Arachnids ) a front psi of 15-16, if I want maximum performance I like 17 to 19. The lower psi gives a more comfortable ride, the higher psi gives a firmer ride. … BRP used to have pre-load adjusters on the OEM shocks/springs, they stopped because a of people were not happy with the harsh ride that would occur the more pre-load that was being used. The handling improved ( for most ) but the over-all ride was not as comfortable ….. IMHO, the best compromise is a stiffer Sway Bar..... and we all know who makes those …. I hope this has helped you understand the over-all dynamics, and effects of tire PSI on your Spyder ..... Mike hyea:

 

[Baron14y]

As you may know I ( & Peter Aawen ) have had actual training that included pressures in tires, and what effect they have on traction in both wet & dry , hot & cold conditions …. for practical, real use purposes, the Perfect PSI doesn't exist. …. Why ? - conditions are constantly changing … What myself and ( I believe ) Peter have always used in our estimations is an average number based on the current properties of 95% of tires made for veh's. ( cars mostly ). " Perfect " is what people who regularly drive at 200 + mph, in veh's designed to use that speed, on surfaces designed to permit that speed. However Perfect is not practical ( or necessary ) in real life driving… We have taken into account the design and specs of those tires, and applied proven principles to give a fairly accurate estimation of what works best for tires we use on our Spyders. A lot of folks don't realize that a tire is also an integral part of the over-all suspension system. A PSI that will achieve maximum handling, is going to effect the ride feel in a negative way, for most folks. Just like racing shocks/springs may improve handling, they won't give 95% of the riders a comfortable ride … If I'm just cruising on my RT, I would use ( Note: nothing I have , or will say, applies to Kenda's or Arachnids ) a front psi of 15-16, if I want maximum performance I like 17 to 19. The lower psi gives a more comfortable ride, the higher psi gives a firmer ride. … BRP used to have pre-load adjusters on the OEM shocks/springs, they stopped because a of people were not happy with the harsh ride that would occur the more pre-load that was being used. The handling improved ( for most ) but the over-all ride was not as comfortable ….. IMHO, the best compromise is a stiffer Sway Bar..... and we all know who makes those …. I hope this has helped you understand the over-all , and effects of tire PSI on your Spyder ..... Mike hyea:

Thank you for the intelligent reply. I am running 20 psi on my front Formoza AZ01's, and 30 psi on the rear Arachnid (that will be replaced shortly) What do you recommend for the Kumho AST on the rear?:bowdown:

 

[Baron14y]

Thank you for the intelligent reply. I am running 20 psi on my front Formoza AZ01's, and 30 psi on the rear Arachnid (that will be replaced shortly) What do you recommend for the Kumho AST on the rear?:bowdown:

Another question. Disregarding the quality and characteristics of the tire, is there any pro or con to using either a 225/50R15 vs 205/55R15 on the rear since they both have the same rolling circumference?opcorn:

 

[BLUEKNIGHT911]

Thank you for the intelligent reply. I am running 20 psi on my front Formoza AZ01's, and 30 psi on the rear Arachnid (that will be replaced shortly) What do you recommend for the Kumho AST on the rear?:bowdown:

17-18 for cruising or a bit higher if you drive faster in the " twistie's ".... something that has been reported here concerning the Kumho, is a loss of traction on wet roads, as the tire ages ( wears down )…. My last use of a Kumho was in 09-10 on my GS … It's not a bad tire, it's just ( imho ) not the best available today ….. Thanks for asking …. Mike hyea:

 

[h0gr1der]

Not the same old subject.

Most advice is to start with posted pressure for your Spyder and go from there.

What criteria do you experts use to determine the change in pressure needed. I'm using the Quatrac 5 on the fronts and Kumho AST on the rear.

I have tried several pressure settings from 15 to 20 for the front and 18 to 26 for the rear and can not really feel that much of a difference. What should I be looking for or feeling for? I now there is no hard and fast rule but I could use some advice.

Thanks for any help.
Dave

Mr KosherKid,
I went through exactly what you're going through to arrive at exactly what BLUEKNIGHT911 and Peter Aawen suggest. I tried the 4 PSI rule, which didn't work for me. I could only get 1 to 1.5 PSI increase on the fronts, and I was going towards 14 PSI on the fronts. What I finally did was the tread temperature measurement (measure at 3 places across the tread quickly, using the appropriate equipment) after a hard run for 1 hour, and finalized that with the wet footprint test (on slick finished concrete or other surface, spray bottle your tire tread with water and roll it until it makes a footprint, measure width and compare to the tire tread width. Too narrow-pressure too high, too wide, pressure too low.) Long story short, as Mr. BLUEKNIGHT911 suggested, I'm running 16 PSI front and 18 PSI rear. Smooth and surefooted ride. I'm strictly a cruiser though, if I were going to push it extremely hard I may add a PSI or 3 to the tires. It doesn't ride as comfortably that way though.

 

[Chupaca]

Great info above...

Noticing the difference is very hard if you are a casual ryder. I have always pointed out that if your steering is feeling heavy your front tire pressure is low but the ryde is comfy...if the steering feels really light and the front end bounces in the corners there is too much pressure and the ryde is rougher. Now depending on roads, heat from both atmosphere and road will vary the pressure and then there is the altitude thingy....not being able to adjust for all these you should find what feels good for you. If recommended is where you started and you went up and down 4 pounds and feel no difference stick with the recommended. If you ryde extended times at different altitudes and temps check a bit more often...:thumbup:

 

[BajaRon]

BLUEKNIGHT911 is right. There are a lot of variables. Though you can get yourself into the ball-park. 'Perfect' is something reserved for the next life. One of the variables is temperature. You fill your tire to 18 psi at 60 degrees. Then you run down the road. If it's cool outside you will probably stay around the original 18 psi. If it is cold outside you can even lose some pressure. But if it's a hot day with pavement that will burn your hand. Then the air in your tires can easily get hot enough (and expand) to go over 20 psi.

BLUEKNIGHT911 is also correct that everything is a trade-off. You want a more comfortable ride? Then you're going to have to lower pressure a few pounds and sacrifice handling and responsiveness. You want handling and responsiveness? Then you're going to give up some on ride comfort. Me, I like performance and am most happy to sacrifice a bit of ride comfort. When you're running the twisties at or near your riding skills. You don't notice the ride all that much!:yikes:

If you are not sure, experiment a bit. I recommend using a good, accurate digital gauge and changing in 2-3 lb. increments so you get an exaggerated effect. If you go just a little bit of change you may not notice enough difference to make a judgement. Like boiling the frog, so to speak.

I highly recommend a good digital tire gauge. Without it, you're just guessing at your actual tire pressures. Getting both front tires to the same pressure (which is very important) is virtually impossible using a standard gauge. With a standard stick gauge you're lucky to get within 2 lbs. And they tend to be somewhat inaccurate on top of that.

I recently purchased this Michelin Digital Tire Pressure Gauge. I've owned a lot of tire pressure gauges in my days. Some more expensive than this one. But this gauge has become my all time favorite. It's really a great gauge. Very well built. Easy to use and easy to read. Fits nicely in your hand. It beeps when the reading has stabilized and holds the number so you can remove the gauge from the valve stem and read it if you are using it in an awkward position.

 

[ThreeWheels]

As an engineer I'm very empirical. I prefer measurements over theory.
Here's what works for me.

Get some chalk and lay it down on the ground. Drive your Spyder over the chalk.
If the center of the tire face is covered in chalk and the edges aren't, the tires are overinflated.
If the edges of the tire face are covered in chalk, and the center isn't, the tires are underinflated.
If the chalk evenly coats the entire face of the tire, you have the proper inflation.
Try deliberately overinflating the tires, and then slowly drop the pressure until the full face is covered in chalk.

As always, my free advice comes with a double your money back guarantee.

 

[BajaRon]

As an engineer I'm very empirical. I prefer measurements over theory.
Here's what works for me.

Get some chalk and lay it down on the ground. Drive your Spyder over the chalk.
If the center of the tire face is covered in chalk and the edges aren't, the tires are overinflated.
If the edges of the tire face are covered in chalk, and the center isn't, the tires are underinflated.
If the chalk evenly coats the entire face of the tire, you have the proper inflation.
Try deliberately overinflating the tires, and then slowly drop the pressure until the full face is covered in chalk.

As always, my free advice comes with a double your money back guarantee.

I can see the logic in your approach. What you suggest may be a very good starting point. But it does not take into consideration the dynamic forces of real world riding. The 'Butt Gauge' may be subjective. But it isn't always that far off.

Vertical centrifugal force tends to balloon the center of the tire at freeway speeds. Lateral centrifugal force in a turn tends to roll the tire off of its tread. Neither of these can be cured completely with tire pressure. But they can be reduced.

 

[Revalden]

I just increased my fronts to 20psi from 16psi and it felt too hard/bouncy. Going back to 16 psi. I look at the edge tread after some hard corners, I usually do corners faster than I should. Yesterday Nanny shut me down a little. :spyder:

 

[JO2L]

BajaRon, How is this unit for getting to the valve on the rear tire?

 

[h0gr1der]

I can see the logic in your approach. What you suggest may be a very good starting point. But it does not take into consideration the dynamic forces of real world riding. The 'Butt Gauge' may be subjective. But it isn't always that far off.

Vertical centrifugal force tends to balloon the center of the tire at freeway speeds. Lateral centrifugal force in a turn tends to roll the tire off of its tread. Neither of these can be cured completely with tire pressure. But they can be reduced.

That, and the heating of the tire plumps it up a bit. Say you're in one of those days that sees a 40-50°F temperature swing. You've found your bike to get maximum tread contact at 18 PSI. So you go out and in the 45°F start of the ride, put 18 PSI in the tires. By the hot part of the day not only has the temperature reached 85°F, but the tires have picked up additional heat from running. At 1 PSI increase in pressure per 10°F increase in temperature, you could expect to see a minimum of 4 PSI of increase from the 40°F swing, then factor in the heat in the tire from running. That's where the experience factor comes in. Experiment for what works for you.

 

[bobbarb4546]

Currently up in the Smokies with our new Vredstein Quatrac 5 tires 16 psi front 18 psi back riding double up with our combined weight around 450 and riding the mountain roads at moderate speeds. The Quatrac 5 tires are performing as expected with great handling and comfort. Being pretty new to trikes we have found that leaning as a team into each curve has helped in maintaining a sense of stability and helping in counter acting the centrifugal force one experiences on these curvy roads. As long time 2 wheel riders we are learning gradually how to get the best performance and comfort out of our 2016 Spyder RT. BajaRon's Sway Bar and our Quatrac 5 tires have made a great improvement in the performance, comfort, and, safety of our rides. We have another week up here before returning to the straightaway's of Florida and we will miss the majestic beauty and challenging rides the Smokies afford. Hope this info helps any of our Spyder Lover's gracing this forum. Rain today from the tropical storm in the Gulf so we will get rested up for a ride up to Deal's Gap and the Dragon tomorrow.

 

[BLUEKNIGHT911]

Currently up in the Smokies with our new Vredstein Quatrac 5 tires 16 psi front 18 psi back riding double up with our combined weight around 450 and riding the mountain roads at moderate speeds. The Quatrac 5 tires are performing as expected with great handling and comfort. Being pretty new to trikes we have found that leaning as a team into each curve has helped in maintaining a sense of stability and helping in counter acting the centrifugal force one experiences on these curvy roads. As long time 2 wheel riders we are learning gradually how to get the best performance and comfort out of our 2016 Spyder RT. BajaRon's Sway Bar and our Quatrac 5 tires have made a great improvement in the performance, comfort, and, safety of our rides. We have another week up here before returning to the straightaway's of Florida and we will miss the majestic beauty and challenging rides the Smokies afford. Hope this info helps any of our Spyder Lover's gracing this forum. Rain today from the tropical storm in the Gulf so we will get rested up for a ride up to Deal's Gap and the Dragon tomorrow.

Yes the Quatrac 5's are really catching on ……. I've been down to the Smokie's where you are a few times …. imho the " Rattler " is / was a much more fun experience …. NO CROWDS …. no LEO's …… have fun ….. Mike hyea:

 

[Curlytops]

IM still on Kendras as they were replaced by the dealer before I bought my spyder… ive tried several different pressures, and I hate the tyre wall wallow of low pressure... was at 21 front and 28 rear for my style of riding, but have since upped the pressure to 25 in the fronts and it now suits my style of riding fine. Everyone will give you different opinions on a forum of why their particular pressures are best.. just ride like you want to and raise and lower the pressures until you find one that suits you.

 

[Peter Aawen]

Curlytops, don't drop the pressure on any Kendas!! They are pretty lightweight tires to start with, many have been shown to have construction issues, and they really NEED the recommended pressure just to hold the metal Spyder bits off the ground! :shocked:

Sure, you can (& should) use lower pressures for any better & stronger constructed car tires, they are more than up to the task and they simply don't require the higher pressures to carry the much lighter load of a Spyder vs that of most cars and yet still function as intended as an integral part of the vehicles suspension, but that's NOT AT ALL appropriate for OE Spyder Spec Kendas!! :lecturef_smilie:

 

[KosherKid]

I did all this also: wet footprint, +4psi, temp, etc. I guess I was looking for defined benchmarks to look for. I know the ride will be harsher with increased pressure but I didn't really feel it. I'm going to take the most common advice and go with 15-16 front and 18-20 rear pressures. Thanks to all for the advice.

Dave