Falken Tyre Pressure

[Fearless]

Hi guys

Question: Falken ZE 912 - 225/50/15 on rear of 2010 RT. Carrying 2 up and trailer.

What tyre pressure would you run, currently 22psi.

Cheers and beers

Frank

[SPYD3R]

considering it's most likely a 4 ply tire... and carrying another person, i would think that 25 - 28 psi would be fine....
however, wait to see what others suggest before you go out and change your PSI...
Dan P
SPYD3R
USA

[BLUEKNIGHT911]

Hi guys

Question: Falken ZE 912 - 225/50/15 on rear of 2010 RT. Carrying 2 up and trailer.

What tyre pressure would you run, currently 22psi.

Cheers and beers

Frank

Because I know the Science ..... You could actually take it down to 18 psi and be even happier. That tire ( Falken ) is able to safely support a 4000 lb. car ....... So the 500 +/- lbs the Spyder has on the rear tire isn't even close to the tires capabilities..... consider this also , the tire is actually part of the suspension system, so the harder ( higher psi ) the tire, the less compliant it is..... and give a harsher ride ...... some folks have said the lower psi's that myself and Peter Aawen recommend leave them feeling that the Spyder feels too loose ..... This is the problem with BUTT science as opposed to REAL science .....Butt's fib ....... good luck - ride safe ........Enjoy ...... Mike

[OlJim]

Go for a nice long ride and then feel the sidewall of the tire. If the pressure is too low the side wall will flex and build heat. This is what causes most blow outs. If not building heat the pressure is high enough or too high. Increase or decrease until no heat build. If load increases you should increase the tire pressure accordingly.

[canamjhb]

I run 20 in the rear. I believe what Mike says but he hasn't converted me entirely. Close, but not quite there. But, hey, I'm old and stubborn..... I have a little over 5,000 miles on the rear and haven't detected any wear yet.

[Peter Aawen]

...... some folks have said the lower psi's that myself and Peter Aawen recommend leave them feeling that the Spyder feels too loose ..... This is the problem with BUTT science as apposed to REAL science .....

Mike's absolutely right - if you get used to riding on a rock hard tire, ANYTHING ELSE is likely to feel 'a bit loose' for a while, at least until you hit a little bit of damp road or until you get used to the 'feel' of the different pressure.... But at those lower & 'more appropriate to the load the tire is carrying' pressures, once you get used to the difference, the suspension & the tire get to work together to your advantage, and your butt AND your wallet will benefit, as will your traction & tire life!! All wins as far as I can see!

Btw, you need SOME heat build-up to get the tire tread compound up to its operating temp, but you don't want so much that the tire carcass or plies start being compromised! Generally, you'll want to aim for a 4psi increase in pressure after ryding for a while, since the pressure increase will be directly related to the temp increase. For Passenger car construction tires (like those we all run on our Spyders, even that lighweight Kenda rubbish!) anything much less than about 2psi will leave the tread compound too cold & therefore too hard & compromising traction; while anything much over about 6 psi means the construction of the tire itself is likely to be compromised as well as significantly increasing the tread wear rates!! You could probably fine tune your pressure even better by measuring the temp increase using a proper tire compound thermometer, but few have access to those, and while measuring the tread or sidewall surface temps with a laser thermo or similar can be a handy indicator, it's not as reliable as the 4psi increase thing, because it is only measuring the top millimetre so of the tread thickness & not the internal tire compound temps, besides which the surface temps vary extremely quickly!! Even just getting off your byke & walking around the back is enough to show a noticeable variation in those surface temps; which can show an increase if the internals are hotter than ideal, or drop rapidly if the ambient air temp is low enough...... or they can pretty much do anything in between!! Which is why the known & direct relationship between psi increase & internal tire temperatures is so handy!

[BLUEKNIGHT911]

I run 20 in the rear. I believe what Mike says but he hasn't converted me entirely. Close, but not quite there. But, hey, I'm old and stubborn..... I have a little over 5,000 miles on the rear and haven't detected any wear yet.

....I'm so glad to hear you are " almost " there ..." Seriously " ...... on the WEAR thing .... Because of the construction of almost every CAR tire, what psi you are using isn't going to effect the WEAR to any noticeable extent..... I advise reading what Peter said above .....( He is a tire EXPERT ) ............ Mike

[canamjhb]

....I'm so glad to hear you are " almost " there ..." Seriously " ...... on the WEAR thing .... Because of the construction of almost every CAR tire, what psi you are using isn't going to effect the WEAR to any noticeable extent..... I advise reading what Peter said above .....( He is a tire EXPERT ) ............ Mike

OK, OK, I give up. I'm going on a ride tomorrow and will drop rear to 18. And I promise to ride a fair amount to give it (my butt) a chance to get use to the lower pressure. We don't get much rain here in Arid-Zone-A and I don't ride in it on purpose. Traction has never been an issue and I honestly don't think I will notice much difference in the 2Lb reduction. But, I will give it a shot....... You provide a compelling argument. (Science)

[Peteoz]

Generally, you'll want to aim for a 4psi increase in pressure after ryding for a while, since the pressure increase will be directly related to the temp increase.

Hey PeterA,
Like Canamjhb, I am running 20psi rear and 18 fronts (Mike hasn’t converted ME entirely either). I notice FOBO is telling me that my tyre psi increases by around 1.5 psi after an hour or so riding for both front and rear. Would dropping the rear by just 2psi to Mike’s recommended 18psi, really result in an increase of 4psi after an hour or so of riding, when 20psi only gives an increase of 1.5psi? It just doesn’t seem possible.
Hopefully the above makes SOME sense to you

Pete

[Peter Aawen]

The actual change you see can be quite different to the actual change I might see from exactly the same change in pressure Pete, it all comes down to the collective impact of ALL the variables involved, including things like the ambient temp, the road surface temp, how hard you ride, how hard you brake, the load you are carrying, the pressure variation, and a whole bunch more.... Buuuut, the only proof is in the pudding, and seriously, you might be surprised how much difference just a little change can bring - so why not try it and see?! And if you think it still feels a 'little loose' on your first try, give it a bit of a chance - for some, it can take 500 miles or more of ryding to get used to the differences in steering a Spyder, and even just a 2psi change CAN bring about just as much of a significant difference in tire behaviour & traction, ride, or handling, so you might need to give it much the same sort of distance/time to get used to the changes there too!!

Still, you don't HAVE to do it all at once!! You noticed the differences dropping your rear tire pressure down to 20 psi made in ride & handling didn't you?? You should've been quite aware of the difference it made in traction if you ever got to ride on a wet road! So even if you don't want to go the whole hog and aim for that 4psi increase first up, maybe take a few little nibbles at it & get comfortable with a few small differences staged over time rather than one big difference all at once?!? Try it, you might be surprised!

Nb: I usually run 16psi in my rear tire when I'm ryding solo, sometimes even going down to 14 psi if it's cold and wet & I don't want to hang the tail on every corner!! I usually only go as high as 18psi when the Missus is on the back or I'm looking at ryding solo at speeds up over 140kph when it's hot & I hafta do the Alice to Darwin run by tomorrow morning OR ELSE!! But that's what works for ME, and it might not be what works for you.... after all Pete, there's a pretty good chance that you might put just a little more load on your Spyder tires than I do (I'm just a lightweight @ 180cm's tall these days!) so you running a little higher pressure may still see the sidewalls flexing enough to heat things up enough to make for the necessary pressure increase, even if it's a larger increase than I'd see.... make sense?

Still, if you like how it feels at 20psi and the traction, ride, & handling at that pressure works OK for you, then ride at that pressure - just bear in mind that you could probably get better traction & tire life going a little lower. But once you are aware that the 1.5 psi increase you get at 20 psi is a touch less than optimum, and by not making that change you will be compromising your tires best traction, ride, handling, and life etc, & maybe increasing your risk of punctures from road hazards & debris a tad too, then you can make an informed choice. No-one is twisting your arm, altho we might flap our gums or throw a few posts at you for being a wimp & not giving it a try, especially if you post about traction concerns or short tire life but ultimately, it IS YOUR choice - we are just trying to make sure that you know about the potential safety aspects, risks, & limitations you might be creating for yourself by running pressures a little too high!

It's those people running tire pressures that are a LOT too high that generally score the long and narrow pieces of mind from Mike'n Me!

[Peteoz]

Thanks Peter. Makes sense, as usual. I do like how 20psi feels compared to 24psi so I’ll give 18psi a go and see how I feel.....but don’t tell Mike......he’ll claim the credit, the grumpy old bugger

Pete

[Peteoz]

.....and sorry for highjacking your thread, Fearless, but it is all pretty relevant info to your question

Pete

[Peter Aawen]

......but don’t tell Mike......he’ll claim the credit, the grumpy old bugger

Pete

That's OK Pete, he can have the credit, he's been saying it here a lot longer'n me & it does tend to make you grumpy after a while.... telling people the same thing over & over & still being ignored, especially when it's as well documented & known by the experts in the field, but pretty much ignored by most everyone else, even those who SHOULD know better & SHOULD be telling the end users!! He just needs a little extra help & occasional back-up.

[Bob Denman]

I ran a 912 on my first RT: just be VERY careful of it's wet road tendencies...

[mrfixit]

considering it's most likely a 4 ply tire... and carrying another person, i would think that 25 - 28 psi would be fine....
however, wait to see what others suggest before you go out and change your PSI...
Dan P
SPYD3R
USA

4 Ply? Look at your tire. That's 4 ply rating.

[BLUEKNIGHT911]

4 Ply? Look at your tire. That's 4 ply rating.

An example ...what's stronger an 8 ply sheet of plywood - or a 6 ply sheet of plywood rated the same as an 8 ply sheet .....answer .....They are both the SAME ............ The " RATING " tells you the functional strength of that tire..............Hope this helps .... Mike

[Easy Rider]

..... This is the problem with BUTT science as apposed to REAL science .....Butt's fib ....... good luck - ride safe ........Enjoy ...... Mike

Not claiming that there is any science in my butt........BUT I will believe the reports IT gives me over what comes out of your head any day.

[BLUEKNIGHT911]

Not claiming that there is any science in my butt........BUT I will believe the reports IT gives me over what comes out of your head any day.

.... Sir your WIT and Repartee is only exceeded by overall intelligence....... ...up here in VT. we enjoy sliding ( where appropriate ) .....down in Fla., I wouldn't recommend it ...... Mike

[Peteoz]

Not claiming that there is any science in my butt........BUT I will believe the reports IT gives me over what comes out of your head any day.

The trouble with expressing our butt feelings is that we are effectively saying that we are talking out of our arse, Easy Rider

Pete

[Fearless]

Thanks guys.

Will try 20psi for the next tankfull and see how that feels.

Heading off to Tasmania next Saturday so will play with pressures on the way down.

Was supposed to heading out today for smoko at our favourate cafe but it is raining well here on the Gold Coast.

Cheers
Frank

[Bike-O-Din]

Well, the racing people use this technique and so I have used this method successfully on all of my bikes, cars, trucks, trailers etc over the years and it has always worked well.

A tire should increase about 10 percent in pressure from cold to full operating temperature. Example: Starting at 25psi cold, the tire should be at 27.5psi when completely warmed up. Starting at 30psi, tire at full temp should be 33psi.

Inflate the tire to the pressure recommended by the tire manufacture, or one you like (or the best guess). Then run the bike until it gets to full operating temp riding it like you normally would (ie, highway, twisty, around town, 2 up, or whatever is "normal" for you). Then check the pressure. If it has gone up 10 percent + or - just a little, you are right on.

If it goes up more than 10 percent then increase the cold starting pressure by a pound or two and try again.

If it does not get to cold plus 10 percent, lower the cold starting pressure by a pound or two and try again.

It takes a few times to get it right, but after that, you never need to check again, just set it and forget it.

It is hard to believe, but this actually works without much regard to the ambient outdoor temperature. Even when it is hot, the 10 percent thing just seems to work. You only have to adjust the cold starting pressure to the magic number as the weather goes from cold to hot and back again over the course of the year.

As an aside, having the fobo TPMS system makes this a breeze to do!!

Have fun, and ride safe.

Mr Bill

[Bob Denman]

You can also try "chalking" your tire tread...

[BLUEKNIGHT911]

Well, the racing people use this technique and so I have used this method successfully on all of my bikes, cars, trucks, trailers etc over the years and it has always worked well.

A tire should increase about 10 percent in pressure from cold to full operating temperature. Example: Starting at 25psi cold, the tire should be at 27.5psi when completely warmed up. Starting at 30psi, tire at full temp should be 33psi.

Inflate the tire to the pressure recommended by the tire manufacture, or one you like (or the best guess). Then run the bike until it gets to full operating temp riding it like you normally would (ie, highway, twisty, around town, 2 up, or whatever is "normal" for you). Then check the pressure. If it has gone up 10 percent + or - just a little, you are right on.

If it goes up more than 10 percent then increase the cold starting pressure by a pound or two and try again.

If it does not get to cold plus 10 percent, lower the cold starting pressure by a pound or two and try again.

It takes a few times to get it right, but after that, you never need to check again, just set it and forget it.

It is hard to believe, but this actually works without much regard to the ambient outdoor temperature. Even when it is hot, the 10 percent thing just seems to work. You only have to adjust the cold starting pressure to the magic number as the weather goes from cold to hot and back again over the course of the year.

As an aside, having the fobo TPMS system makes this a breeze to do!!

Have fun, and ride safe.

Mr Bill

Nice theory - However could you please tell me what manufacturer of ....Auto tires ... gives recommended tire pressures for Spyders ............. Answer - NONE , because the Auto Tire manufacturers don't test their tires with the Spyder's specifications in mind ... Mike

[canamjhb]

Today I dropped my rear pressure from 20 to 18 psi. I didn't think it would make much difference. I was wrong. Did some mountain twisties, city driving, and 60-70 mph sweepers. A little over 180 miles total. I didn't feel much in the city except the bumps were a little softer. Mountain twisties and sweepers were noticeably more smooth and in better control. Much better.....I thought I might have a little mushy feeling but had none. Great improvement. I might be a slow learner. But I have now become a believer. Those of you running CTs are missing better performance by running higher pressure. Thank you gentlemen....

[BLUEKNIGHT911]

Today I dropped my rear pressure from 20 to 18 psi. I didn't think it would make much difference. I was wrong. Did some mountain twisties, city driving, and 60-70 mph sweepers. A little over 180 miles total. I didn't feel much in the city except the bumps were a little softer. Mountain twisties and sweepers were noticeably more smooth and in better control. Much better.....I thought I might have a little mushy feeling but had none. Great improvement. I might be a slow learner. But I have now become a believer. Those of you running CTs are missing better performance by running higher pressure. Thank you gentlemen....

Thanks for sharing .... maybe your post will give others a bit of a nudge to at least try a lower PSI .... I am surprised you noticed it that quickly, but you didn't drop your psi 10lbs, it was only 2 lbs...... but it will actually show performance gains and assist the feel of the suspension .... I hope Peter reads this post ...... Sir I hope you have an Auto tire on the rear ( I think you do ) ....... How about the fronts , auto tires can be as low as 14psi and also benefit from less pressure ............... Mike