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Tire pressure recommendations

Paul - first I'd like to Thank you for your civility in your two ( above ) posts , others here can't seem to control themselves :yikes:, one of whom is now in a " time-out "...…. The short non-hyper technical answer is A. because they don't have to provide that info …. and B.- the answer is almost meaningless in terms of normal riding. ….. Under Racing circumstances this info would be gathered by each individual Team for their use in determining what works best for their vehicle and specific driver ( yes it's that technical )….But for everyday use the variables are so large , the manufacturers are only concerned about getting within certain parameters' of the safe range …… most of this info is considered " Proprietary " and therefore not divulged..... Are Heat signatures important - Yes , but they aren't critical. Not in the sense that is really meaningful..... The Basic Build criteria for Auto tires is met by ALL manufacturers who are more concerned with OVER-Loading the tires than with Under-stressing them. What I and I'm sure Peter Aawen do is use what we know about the Entire PSI thing and how it relates to tires ( in general ) and come up with a Well educated estimate of what Should work best for our Spyders..... To the best of my knowledge No-one has done any technical testing of Auto tires on Spyders and probably never will.....People are looking for answers/info that doesn't exist, and some of them get their Panties in a Wad because their Questions aren't being answered.....Hope this helped answer your questions ....................................................On another note: A few years back I sought your advice on the Shock Angle thing I was working on, because I knew you had worked for OHLINS ..... If I remember correctly, I NEVER asked you to prove your level of Expertise about your knowledge base. I was intelligent enough to assume that if OHLINS was smart enough to hire you THEY did their homework about it !!!!...... So what Gaul's me, is the fact the I'm Badgered about Proving my credentials. Except for one time, I've never asked them to prove theirs......... To supply the info THEY have required, I would have to go to the Landfill where this stuff has been buried for over three decades.... My X - deposited it there long before the divorce became Legal ........ Mike :thumbup:

To clarify, I have never worked for Ohlins.

In regards to your shock bracket project, your data, essentially the suspension geometry was mapped by myself, and I gave you suspension leverage ratio changes compared to stock, changes in wheel travel based off lofted hard point data.

I offered my opinion of what the data represented, and how it would alter chassis handling. You were the designer, fabricator and test rider. I merely presented what the data represented.
 
OHLINS - ERROR

Paul I'm sorry if I CLAIMED you worked for OHLINS , I will delete that immediately...… What I find interesting is: it appears that error was only thing you felt the need to comment on. Was all the rest meaningless to you ???...……………. Mike :thumbup::shemademe_smilie::shemademe_smilie:
 
Paul I'm sorry if I CLAIMED you worked for OHLINS , I will delete that immediately...… What I find interesting is: it appears that error was only thing you felt the need to comment on. Was all the rest meaningless to you ???...……………. Mike :thumbup::shemademe_smilie::shemademe_smilie:

Actually no, had somewhere to be and no time for a technical reply, patience, in time I will reply. Not now either as I am in Carters shopping for #2 granddaughters birthday.
 
Paul - first I'd like to Thank you for your civility in your two ( above ) posts , others here can't seem to control themselves :yikes:, one of whom is now in a " time-out "...…. The short non-hyper technical answer is A. because they don't have to provide that info …. and B.- the answer is almost meaningless in terms of normal riding. ….. Under Racing circumstances this info would be gathered by each individual Team for their use in determining what works best for their vehicle and specific driver ( yes it's that technical )….But for everyday use the variables are so large , the manufacturers are only concerned about getting within certain parameters' of the safe range …… most of this info is considered " Proprietary " and therefore not divulged..... Are Heat signatures important - Yes , but they aren't critical. Not in the sense that is really meaningful..... The Basic Build criteria for Auto tires is met by ALL manufacturers who are more concerned with OVER-Loading the tires than with Under-stressing them. What I and I'm sure Peter Aawen do is use what we know about the Entire PSI thing and how it relates to tires ( in general ) and come up with a Well educated estimate of what Should work best for our Spyders..... To the best of my knowledge No-one has done any technical testing of Auto tires on Spyders and probably never will.....People are looking for answers/info that doesn't exist, and some of them get their Panties in a Wad because their Questions aren't being answered.....Hope this helped answer your questions ....................................................On another note: A few years back I sought your advice on the Shock Angle thing I was working on, because I …..THOUGHT …. you had worked for OHLINS ..... If I remember correctly, I NEVER asked you to prove your level of Expertise about your knowledge base. I was intelligent enough to assume that if some company was smart enough to hire you THEY did their homework about it !!!!...... So what Gaul's me, is the fact the I'm Badgered about Proving my credentials. Except for one time, I've never asked them to prove theirs......... To supply the info THEY have required, I would have to go to the Landfill where this stuff has been buried for over three decades.... My X - deposited it there long before the divorce became Legal ........ Mike :thumbup:

I have read, and reread your reply several times.

I am going to avoid focus on any of the issues or remarks concerning proving credentials, others attitude or treatment towards others etc.

Tire pressures. To enter a worthy reply, first off, I disagree with portions of you recent reply. Unlike you, I do believe vehicle oems derive correct tire pressure based on tread temperatures across the tread. Myself I can not see any other means to validate the tire is not overheated or improperly inflated. With a base pressure gained from temp testing, that pressure can carry over into load testing. Understand, we all realize the vehicle manufacturers and tire companies have a lot of baseline data. So, essentially, if the know a tire size, a vehicle weight, and intended use, they can “suggest” a very educated cold tire pressure to begin with.

From that cold tire pressure, they can validate as needed, if the cold tire pressure is accurate.

At the oem level, if they are validating a cold tire pressure to be accurate, and this is the key question, how exactly do they determine if they got the cold tire pressure value correct. Comedians will say with a gauge, but seriously what do we believe they use. A tire temp signature acroos the tread or something else.

Vehicle weight, this one variable differs so widely between cars, trucks, motorcycles, and Spyders. Weight generates heat. Heat increases tire pressure. A car, heavier than a Spyder, will generate more heat into the tire. If we are in a quest to see a 4 psi increase in pressure as a result of heat, the lighter vehicle begins with a handicap. From what is published, it is accepted data that tires with lower pressure generate more heat, and underinflated tires should be avoid to prevent failures, probably from heat related concerns. Therefore, accepting the light vehicle is at a disadvantage to generate heat into the tire, it seems using the lower tire pressure is to overcome the disadvantage and generate heat, and with that, increased pressure.

But wait, there’s more, if the tire tread and casing are generating heat as it rolls, and we are expecting a certain pressure increase, should we not worry if portion of the tires edge tread is running notably hotter than the tires center?

Everything I found regarding a 4 psi increase was in reference to cars. Also, each reference was regarding pressure checks with hot tires, saying 4 psi hot should give proper cold tire pressure. This was on a heavy car. Simply not sure how relevent the difference between weights is.
 
SPYDER TIRES & PSI

I have read, and reread your reply several times.

I am going to avoid focus on any of the issues or remarks concerning proving credentials, others attitude or treatment towards others etc.

Tire pressures. To enter a worthy reply, first off, I disagree with portions of you recent reply. Unlike you, I do believe vehicle oems derive correct tire pressure based on tread temperatures across the tread. Myself I can not see any other means to validate the tire is not overheated or improperly inflated. With a base pressure gained from temp testing, that pressure can carry over into load testing. Understand, we all realize the vehicle manufacturers and tire companies have a lot of baseline data. So, essentially, if the know a tire size, a vehicle weight, and intended use, they can “suggest” a very educated cold tire pressure to begin with.

From that cold tire pressure, they can validate as needed, if the cold tire pressure is accurate.

At the oem level, if they are validating a cold tire pressure to be accurate, and this is the key question, how exactly do they determine if they got the cold tire pressure value correct. Comedians will say with a gauge, but seriously what do we believe they use. A tire temp signature acroos the tread or something else.

Vehicle weight, this one variable differs so widely between cars, trucks, motorcycles, and Spyders. Weight generates heat. Heat increases tire pressure. A car, heavier than a Spyder, will generate more heat into the tire. If we are in a quest to see a 4 psi increase in pressure as a result of heat, the lighter vehicle begins with a handicap. From what is published, it is accepted data that tires with lower pressure generate more heat, and underinflated tires should be avoid to prevent failures, probably from heat related concerns. Therefore, accepting the light vehicle is at a disadvantage to generate heat into the tire, it seems using the lower tire pressure is to overcome the disadvantage and generate heat, and with that, increased pressure.

But wait, there’s more, if the tire tread and casing are generating heat as it rolls, and we are expecting a certain pressure increase, should we not worry if portion of the tires edge tread is running notably hotter than the tires center?

Everything I found regarding a 4 psi increase was in reference to cars. Also, each reference was regarding pressure checks with hot tires, saying 4 psi hot should give proper cold tire pressure. This was on a heavy car. Simply not sure how relevent the difference between weights is.
I'll be the barer of bad news ….. the info and or validation of the info you seek ….. Doesn't exist …… Our Spyders are so light compared to any veh's used for testing purposes ….their findings won't be valid for our Spyders. It would be great if this wasn't the case, but sadly your search for answers will be futile imho …… Technical proof of what Peter and I have said about Spyder PSI's isn't likely to happen - I have neither the time nor the money to fund this type of project and why should I , I'm very happy with the tire with the tire PSI's I use.....and I'm perfectly OK if you choose differently...………… Thanks for the discussion ….. Mike :thumbup:......… PS, You didn't indicate whether you read Peter's post # 21 on this thread ….it's very informative
 
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I'll be the barer of bad news ….. the info and or validation of the info you seek ….. Doesn't exist …… Our Spyders are so light compared to any veh's used for testing purposes ….their findings won't be valid for our Spyders. It would be great if this wasn't the case, but sadly your search for answers will be futile imho …… Technical proof of what Peter and I have said about Spyder PSI's isn't likely to happen - I have neither the time nor the money to fund this type of project and why should I , I'm very happy with the tire with the tire PSI's I use.....and I'm perfectly OK if you choose differently...………… Thanks for the discussion ….. Mike :thumbup:......… PS, You didn't indicate whether you read Peter's post # 21 on this thread ….it's very informative

Mike, this one quote from your recent post is exactly how I am viewing the accuracy of using the 4 psi method.

From your post above:
"Our Spyders are so light compared to any veh's used for testing purposes ….their findings won't be valid for our Spyders."

Understand your not wanting to test and so forth, again understandable.
At some point, I may accomplish a heat test / Pressure check, and see how things plot out. If I ran FOBO setup, pressure checks would be simple, but I do not so any pressure checks require the gauge.

I had read Peters post a few times. Seems to be a good explanation for a person wanting to go with the 4 psi rule. He does make mention though that 4 psi is kind of a "rule of thumb", and for some wanting different characteristics they may opt for only 2 psi increase, or as high as 6 psi.

Peter does hold fast to the notion that the 4 psi method accounts for all variables that effect pressure and temperature of the tire. Again, I stay true to my idea that vehicle weight generates heat. With that I must still speculate that 4 psi is derived for cars and their typical weights. Lighter vehicles simply have a more difficult time generating heat into the tire, and under inflating is a known generator of heat.

Is it possible that the low pressure needed to generate enough heat to increase the pressure 4 psi is actually under inflated?
 
Tire heat signature

Mike, this one quote from your recent post is exactly how I am viewing the accuracy of using the 4 psi method.

From your post above:
"Our Spyders are so light compared to any veh's used for testing purposes ….their findings won't be valid for our Spyders."

Understand your not wanting to test and so forth, again understandable.
At some point, I may accomplish a heat test / Pressure check, and see how things plot out. If I ran FOBO setup, pressure checks would be simple, but I do not so any pressure checks require the gauge.

I had read Peters post a few times. Seems to be a good explanation for a person wanting to go with the 4 psi rule. He does make mention though that 4 psi is kind of a "rule of thumb", and for some wanting different characteristics they may opt for only 2 psi increase, or as high as 6 psi.

Peter does hold fast to the notion that the 4 psi method accounts for all variables that effect pressure and temperature of the tire. Again, I stay true to my idea that vehicle weight generates heat. With that I must still speculate that 4 psi is derived for cars and their typical weights. Lighter vehicles simply have a more difficult time generating heat into the tire, and under inflating is a known generator of heat.

Is it possible that the low pressure needed to generate enough heat to increase the pressure 4 psi is actually under inflated?
… I will defer to Peter for this answer -
Paul, on the heat vs. psi thing.... I'm more flexible than Peter is ….. To my way of thinking, using lower pressures in an Auto tire on Spyders has more to do with TREAD FLEXIBILITY ….. the tiny " SIPES " that most tires have won't work as effectively if there is LESS flexibility. A tire designed to hold up a 4000lb ( @32 to 36 psi ) vehicle is also designed to function at it's best at THAT WEIGHT ….. so an 1100lb Spyder needs much less pressure to function is if it weighed 4000 lbs..... I have never even suggested that anyone use any PSI that is LESS then what KENDA recommends, the Kenda absolutely needs the Higher PSI to function safely.... it doesn't have even half the construction that even the worst Auto tire has...…. Do some heat signature tests, keep accurate records and see where it leads...… I can understand Why people want proof, but un-fortunately I can't provide it, do to circumstances beyond my control..... all my records got trashed decades ago...……. Mike :thumbup:
 
'the 4psi Rule' is a 'Rule of Thumb' - it's a handy, easy, relatively simple, & repeatable method of giving you/most riders/drivers a 'tool' that will let them work out or even confirm that the pressures they are using are in the right ball park for what they are doing/the load their tires are being subjected to right now. It isn't specifically exact, and there are some circumstances (not too many tho!) where it might not be any better than a SWAG...

This 'Rule of Thumb' DOES take into account ALL the variables that will effect tire pressures in the riding/driving that you've just done, so any variable likely to impact the pressure/temperature change in that time HAS ALREADY DONE SO!!(Do remember, this rule of thumb calls for you to set your pressures to those you think are right to start with, then you ride/drive for an hour AND YOU CHECK THEM AGAIN, looking for that 4psi increase! Too much increase means the start pressure was too low; too little increase means the start pressure was too high!) It's up to YOU to make a judgement call & an educated guess on the riding/driving that you are about to do if you want to, and to use the info gained from the riding/driving you've just done & your 2nd pressure check plus what you know about/expect to face in the riding/driving ahead in order to confirm that your chosen pressures this morning were correct or if they need changing to suit what's coming even better - and the 4psi Rule is just one of quite a few tools that can help guide you in getting fairly close to what is 'right' without doing all the hard stuff!!

Peter, I've been trying to find out where this 4 psi rule of thumb comes from. It appears to originate with the auto tire industry in that most drivers, when using a gas station tire inflation machine, are adding air to an already hot tire, so to use the cold-inflated pressure would result in under-inflated tires. They suggest as a rule of thumb to pump up to 4 psi over the recommended cold inflation PSI.

Now, that's on car tires, where the typical inflation for a radial tire is 30-32 psi. 4 psi would represent about a 12-15% increase over cold tire recommended pressure. If we apply the 12-15% rule to Spyders using car tires, where most folks are recommending a cold inflation pressure of 20 psi, give or take, then we'd be looking for a 2.5 to 3 psi differential between hot and cold for an optimally inflated tire. What do you think?

I know there was a post on this forum where someone using that guideline was saying that a 12-15% range (I think) indicated a properly inflated tire. A higher difference indicated an under-inflated tire and a lower differential indicated an over-inflated tire.

I'd like to use this method for determining the best pressure for my new rear tire (a Michelin Premier A/S), since the recommendations on this forum are all over the place, from 18psi to 28psi.

Thoughts?
 
OK, at the risk of writing another epic tome, I've used the 4psi rule as outlined above on a whole range of vehicles and a whole range of tires over the last 50 or so years, and I've found that using the 4psi rule basically works across the board to get the best balance across the range of a tire's behaviour & performance... doesn't matter if it's heavy haulage truck tire, a thumping great off road tire, your mum's passenger car tire, or a tiny little motor scooter tire - aim for a 4 psi increase after an hours use & you'll get better performance across the board in every factor & feature & be very close to the optimal pressure for that tire in those particular conditions... and that's been confirmed by comparison to the calculations & testing done by a number of tire design & test engineers from a variety of tire manufacturers over the years too, some that I've worked for/with and some that I haven't. When you look for where all the lines reflecting changes in each factor of behaviour/performance as pressure changes on their charts, the place all the lines cross at is on or within a smidge of the pressure that gives that 4psi increase!! :clap:

Where it came from originally, I don't really know, but I first learnt it about 40 years ago from a 'tire guru' who'd looked after the tires for an international GP Race team back in the 50's & 60's, and since then I've seen it referenced & used in & by all sorts of companies & people... I even found a document written in the early 1890's referencing aiming for a 4psi increase after riding (a bicycle!) for an hour; and if you search you can find it referenced somewhere in pretty much every decade since! In most of the tire manufacturing company's that I've worked with/for, all the calculations & testing that goes into creating the charts & graphs they use to produce the tables of 'pressure for given load' that they publish often either hang off or are at some stage compared directly to the 4psi rule; lots of TPMsystems have settings that at a very basic level somewhere use the 4psi increase as a benchmark or trigger; many tire manufacturers & top level car racing teams either use it directly to help them 'fine-tune' their pressures or use it in their testing and development; it's been used widely either as a referenced factor or directly across pretty much all industries & activities that use pneumatic tires; and when I was a youngster, all the best tire companies & fitters used & recommended applying the 4psi rule to get the best from their tires.... And quite a few existing & reputable tire manufacturing companies still use &/or refer to it, some even still publish it for purchasers of their tires to use! For whatever reasons, it seems to me that it's probably only the last 20-30 years or so that the 4psi rule has receeded from the forefront of 'general knowledge' about tires in the passenger car using population; when I was a kid just about every tire fitter would either use it themselves when setting customer's tire pressures or they'd tell & help their customers in using it to get the best from their tires.... :shocked:

It works because it's based upon the changes that occur in the air that the tire contains while it's being used, so it doesn't really matter if it's the tire carcass flexing or the tread working, if the tire itself gets hotter, the air inside the tire gets hotter, either as a cause or as an effect, and looking for a 4psi increase allows a tested & proven standard change to be measured & aimed for. But if a particular user wants to target saaay fuel economy over tread grip/traction, they can (& some do) make an informed decision on aiming for saaay 2psi instead of 4. Want to enhance traction over tire life? Then they can aim for 6 psi. And since it's the air inside the bag (tire) that is actually carrying the load, it doesn't matter if it's a lightweight bicycle tire under your Spyder or a heavy duty M&S tire under your Spyder, aim for the 4psi increase & you'll be much closer if not exactly on the optimum pressure for that tire under that load to hit the optimum spot where all the lines on the chart cross!! The lightweight tire NEEDS MORE air in it to keep the tread on the road, the tire on the rim, & the rim off the road; while the heavy duty tire NEEDS a whole lot LESS air in it to allow it to flex & conform to the surface & absorb any road shocks & flex enough to reach it's ideal operating temp, cos the strength of the tread & sidewall is so much that any more air than results in that 4psi increase would have the tread not flexing at all & it'd be like riding on a steel railway bogie wheel.... and leave you either riding on a 1" wide strip down the middle of the tread cos the tire's blown up like an over-inflated balloon or you'll be cornering on the very edges of the tread with the rest of it lifted right off the road surface as the Spyder leans so much that it'll either skid off the road or maybe just play dead ants & flip over to lie on it's back rather than letting the sidewalls flex enough to keep the tread on & gripping the road during cornering!! :shocked:

Dunno if I've answered all your questions, but I've got a large collection of bunf gathered during over about 40 years of study, including my own & others notes & calculations, essays, presentations, documents etc that address every point I've ever seen raised on this; I can't & won't reproduce it all here, but you're very welcome to come visit & go thru it to your hearts content (altho my Wife would dearly love to get rid of it all!! What possible benefit can I see in collecting musty 100 year old papers, stuff like the scribbles I made on the back of a lunch wrapper about the temp & air pressure changes that occurred while I was putting down 1000 miles in 12 hours on a circle track & skid pan more than 20 years ago, or the notes re other's tire pressures & tread wear that I made on our Spyder ryde last weekend!! :rolleyes: )
 
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Wait till the new airless tyres hit the scene then we'll have some debate.Compressor values are going to tank for one.Kenda will probably skimp on the honeycomb.ssc_hidingsofa2.gif
 
I have a newly purchased 2017 F3-S with 4000km on it. I just changed the front tyres to Conti Premium Contact 2 tyres 175/55-15 and, based on many forum updates, plan to run these tyres at 16psi cold.
I'll wear out the stock Kenda rear tyre before replacing it with a car tyre. The Spyder F3 owners manual and service manual both recommend 28psi for the Kenda tyre. I see several updates mentioning 18psi for rear car tyres. My question is, what pressures are people running in the stock Kenda? I guess it would be somewhere between 18 and 28, but cannot find much on this.
IanB
 
I have a newly purchased 2017 F3-S with 4000km on it. I just changed the front tyres to Conti Premium Contact 2 tyres 175/55-15 and, based on many forum updates, plan to run these tyres at 16psi cold.
I'll wear out the stock Kenda rear tyre before replacing it with a car tyre. The Spyder F3 owners manual and service manual both recommend 28psi for the Kenda tyre. I see several updates mentioning 18psi for rear car tyres. My question is, what pressures are people running in the stock Kenda? I guess it would be somewhere between 18 and 28, but cannot find much on this.
IanB

From what I've learned on this Forum, the Kenda's are garbage weak tires - Period ..... I would stick with 28 psi for the rear ( only ) .....( for auto tires 18-19 psi works best )... there is no magic psi ( for Kenda's that will change the " Wear " outcome...... Mike :thumbup:
 
I had an order in at Tire Rack for the same Contis, but the shipment they expected didn’t arrive after 10 days, and then became ETA unknown. Changed to Yokohama Avids which were the only tire in the 165/60 or 175/55 range for the F3 available. They’ve been strongly recommended by one or more forum pundits, so am hoping their $20 per tire cost is worth it. They arrived yesterday, one day after ordering. I’ll go with 16 psi cold also, unless convinced otherwise. Still have brake flush/pads, front sprocket and the tires before the “new” lady comes off the stands for her first post delivery ride. :2thumbs::ohyea:
 
Right, thanks, 28psi it is for the Kenda. No sign of wear on it so far after 2500 miles.
I bought the Contis back in July. Here in Australia I could not find Federal, Vredestein etc. For me it was the Bridgestone Potenza or the Contis. It turned out that the Potenzas were hard to get too. I like that Continental says they are hydroplane resistant, they have 3 large, deep sipes around the tyre. The 175/55 profile is very similar to the stock Kenda's 165/60, no trouble with touching the mudguards. Also, if you want, with these (almost any car tyre I guess) you can swap the front wheels. They have asymmetrical tread and care which side is in. The stock Kendas care which way they rotate (so the diagonal sipes pump water out sideways). To "rotate" the Kendas halfway through their life you must remount them on the opposite wheel.
IanB
 
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