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  1. #1
    Very Active Member Wildrice's Avatar
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    Default Acceptable front tire width

    Currently I have the original 165/55/R15 KENDA on the front. Can I go a touch wider to 165/60/R15 or 165/65/R15 without fender interference. Has anyone spacer's out the fender w/o major work? Or just increase the width w/o shimming the fender width? Brake lines are another consideration.
    Feedback on experience requested, thank you kindly.
    Darrell

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    Very Active Member SteveLaoyster's Avatar
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    Quote Originally Posted by Wildrice View Post
    Currently I have the original 165/55/R15 KENDA on the front. Can I go a touch wider to 165/60/R15 or 165/65/R15 without fender interference. Has anyone spacer's out the fender w/o major work? Or just increase the width w/o shimming the fender width? Brake lines are another consideration.
    Feedback on experience requested, thank you kindly.
    Darrell
    The size you are changing is the height. If you want wider you would go to a 175/55R15.

    Check out this site: https://tiresize.com/calculator/

    You can get an idea about the size changes. Good luck.
    Last edited by SteveLaoyster; 10-12-2017 at 08:41 PM.
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    I'm running 175/60R15 Kumhos up front with 14-16psi in them and have no issues without any shimming or adjustments of the fenders; the only thing I've done is to swap the hex head screws on the inside of the wheel arch/fenders out in favour of lower pan head screws because the hex heads protruded out into the wheel space about 10mm & the pan heads sit pretty flush, not leaving anything for the tires to scrape on..

    I have heard/seen that some people running this sized tire at different pressures find that the tire flexes/distorts enough during hard cornering for the inside rear edge of the tire to scrape on the lower inside rear panel of the fender. I believe that this is happening because they are running pressures high enough that the tire cannot flex appropriately or quick enough during cornering so that the distortion caused by the cornering forces keep the tire distorted for longer than it would if the tire was running at slightly lower pressures. Certainly all those I've seen with this issue have been running pressures of 18-20 psi ir higher (because they felt that gave them 'more direct' steering, despite the clearly lower traction & performance evidenced on back to back slalom runs at different pressures) and the scraping stopped immediately they dropped 4 or so psi out of their tires, bringing their pressures down below 18psi. The front end of our Spyders really don't carry a great load, so they don't need a high pressure to help the tire support that load, and running pressures too high reduces the contact patch size & also forces the edges of the contact patch to lift during hard cornering, reducing it even further & holding that distorted shape for longer as the carcass of the tire rotates!! Slightly lower pressures help optimise the size of the contact patch & allow enough tire carcass flex to keep the tread contact patch firmly on the road surface instead of peeling an edge or side up & off the road, & releasing any carcass distortion almost immediately the tread leaves the road surface!!

    However, as those of us who have studied tires, pressures, & their use on vehicles are well aware, tire pressures are not a simple cut & dried one size fits all thing! Like the rest of us who have studied this, I am very aware that while running 'stronger' car tires on a Spyder rather than the lightly constructed Kendas definitely needs lower pressures, it isn't all that hard to go too low & drop your pressures below the optimum for the way YOU ryde & the tires YOU are running on your Spyder (or car, or whatever) so much so that while you will get better traction from the lower pressure, that traction comes at the cost of somewhat increased rolling resistance, sapping power & needlessly wasting fuel, as well as making the handling feel a little less than ideal cos it's so soft & spongy. Anything less than double digit pressure on a Spyder could be an issue this way! Still, the optimum tire pressure for your tires is a very personal thing, very dependant upon the way you ride & the tires you run, so what works for me may not be exactly right for you; but you can & shouldn't be scared of adjusting your pressures up & down a little from that optimum to work out what feels best for you & works best for your tires & the way you want to ryde.

    The 4psi rule can help get the optimum pressure for your tires; it aims for a 4psi increase in pressure after an hour's riding - more than a 4psi increase means your cold start pressure was too LOW, while less than a 4psi increase means your cold start pressure was too HIGH... OR you could use a temp sensor to check the tread temp at 3-5/7 or so places across the tread face & then check them again 30-60 mins later - an even temp increase across the tread face is what you want to see, while a hot strip on one side or the other of the tread face generally reveals an alignment or a loading problem; hot edge strips down each side of the tread indicates underinflation; & a hot strip in the centre of the tread indicates overinflation. These tools can help you arrive at the optimum pressure for your tires with regard to the way you ride, the load on your Spyder, the tires you have fitted, and the road surfaces you are ryding on, etc, resulting in you getting the best combination of ride, handling, traction, fuel economy, & tire life you can from those tires, and knowing that, you can generally make an informed decision on how that FEELS to YOU, or whether it will provide what YOU want from your tires, & adjust the optimum pressures up or down a little accordingly.

    Dropping your pressures a little below the ideal can soften the ride at touch, increase puncture resistance, & improve traction on marginal surfaces like wet or icy roads, but it will come at a cost in terms of greater rolling resistance, higher fuel use, & more tire wear on the edges of the tire, & if you go too low it can cause adverse handling and may also cause overheating & risk rolling the bead off the rim. Similarly, increasing your tire pressures a little above the ideal can improve the 'directness' of your steering (up to a limit, above which it just increases the potential for traction loss &/or rapid & unpredictable transition from understeer to uncontrollable oversteer or even causing the vehicle to roll!) but it comes at the cost of less traction & greater tire wear, increased risk of puncture from road debris or hazards, and a harsher ride, & if you go to far you can seriously compromise traction and handling as well as making the vehicle unstable at speed (or any speed!!)

    Hope that lot hasn't added too much to your ponderings, but with any luck, it may have helped others too!

    Ps: all other things being equal & with correct alignment, running slightly wider tires will generally increase the potential tire life, stability, & traction on dry surfaces that you can expect, as well as usually improving ride & handling. Running 'stronger' & slightly wider tires at the right pressures does all that too, but definitely will improve the responsiveness & handling of the vehicle as well as improving both wet & dry traction if you've got your pressures right, but it's essential that you get the pressures close to right, if they are too high the tire won't be able to clear water off the road surface or be at the correct temps to grip the surface properly... Lots of advantages to going up a size in width, IF you get your tire pressures right!
    Last edited by Peter Aawen; 10-12-2017 at 09:55 PM.
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  4. #4
    Very Active Member Highwayman2013's Avatar
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    You could just get the stock size Federals. Evo or Formosa.
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    Very Active Member Peteoz's Avatar
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    Like Peter A, I am running 175/60x15 KH17 Kuhmos, Darrell. I did replace any stock fender bolts that may come in contact with the tyre for lower profile “button” heads, but I don’t believe there was any real need to.

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    Very Active Member jcthorne's Avatar
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    We install Yokohama 175/55R15s and it requires no changes to the bike. They fit all 3 fender styles in OEM configuration. They fit and perform perfectly. Very smooth and great handling tire.

    Blue Flame Spyder F3-S.

  7. #7
    Very Active Member Wildrice's Avatar
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    [QUOTE=Peter Aawen;1308552]I'm running 175/60R15 Kumhos up front with 14-16psi in them and have no issues without any shimming or adjustments of the fenders; the only thing I've done is to swap the hex head screws on the inside of the wheel arch/fenders out in favour of lower pan head screws because the hex heads protruded out into the wheel space about 10mm & the pan heads sit pretty flush, not leaving anything for the tires to scrape on.. /QUOTE

    Peter,
    According to the chart SteveLaoyster posted https://tiresize.com/calculator/ (Thank You Steve)
    Tire comparison chart.JPG
    The diameter is 22.1" x 3.14==69.39" Circumference of the 165/55/R15
    The diameter is 23.3" x 3.14==73.16" Circumference of the 175/60/R15
    The chart shows the Diameter to be 5.4% larger on the 175/60/R15.

    Does this difference between rotation ratio vehicle speed front-rear tire get noticed by the "Nanny"?
    Darrell

  8. #8
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    Quote Originally Posted by Peter Aawen View Post
    ......

    The 4psi rule can help get the optimum pressure for your tires; it aims for a 4psi increase in pressure after an hour's riding - more than a 4psi increase means your cold start pressure was too LOW, while less than a 4psi increase means your cold start pressure was too HIGH...

    Very good, comprehensive info you've provided, Peter - Thanks!

    However, I have a question about the 4 psi rule. Based on what I read in your post (quoted above), it seems to imply that one way to get tire pressure to optimum levels would be to take that one hour ride, then immediately read the pressures and then subtract 4 pounds from that value. Then, once the tires have cooled (perhaps the next day), raise/lower the psi to that level.

    Is that a sensible approach? And does the 4 psi rule apply to all 3 tires or just to the fronts? And does the rule apply to the OEM tires on the Spyder?

    Thanks!

  9. #9
    Very Active Member Wildrice's Avatar
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    Default Tire pressure and checing oil level

    Quote Originally Posted by newbert View Post
    Very good, comprehensive info you've provided, Peter - Thanks!

    However, I have a question about the 4 psi rule. Based on what I read in your post (quoted above), it seems to imply that one way to get tire pressure to optimum levels would be to take that one hour ride, then immediately read the pressures and then subtract 4 pounds from that value. Then, once the tires have cooled (perhaps the next day), raise/lower the psi to that level.

    Is that a sensible approach? And does the 4 psi rule apply to all 3 tires or just to the fronts? And does the rule apply to the OEM tires on the Spyder?

    Thanks!
    I have never seen nor heard of another similar long drawn out procedure for checking the oil level or tire pressure on amy other vehicle. BRP must have a "Joke Staff Dept". Most creative procedule gets another paid holiday. Remeber when we parked the vehicle--waited a few minutes & then checked the oil level--as in a gas station fuel fill up, OR checking the tire pressure when the tires were cold???
    Darrell

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    Quote Originally Posted by newbert View Post
    Very good, comprehensive info you've provided, Peter - Thanks!

    However, I have a question about the 4 psi rule. Based on what I read in your post (quoted above), it seems to imply that one way to get tire pressure to optimum levels would be to take that one hour ride, then immediately read the pressures and then subtract 4 pounds from that value. Then, once the tires have cooled (perhaps the next day), raise/lower the psi to that level.

    Is that a sensible approach? And does the 4 psi rule apply to all 3 tires or just to the fronts? And does the rule apply to the OEM tires on the Spyder?

    Thanks!
    It doesn't work that way newbert, since the total pressure increase from cold will vary somewhat depending on what your cold start pressures were - too high to start & the pressure won't go up any; too low & it'll go up a whole lot (pressures can almost double under adverse conditions!) You hafta start with checking your cold pressures, ride, check, adjust - and you might even need to do that a few times/over a few days to get it right, but it soon becomes just a matter of checking your tires as normal & maybe adjusting your cold start pressures in response to significant riding or condition changes (bloody hot days or long fast rides might need a little higher pressure than freezing cold days &/or tootling around the city! ) But at the most basic, it is extremely easy - you check & set your pressures cold, you ride, then you check again to confirm that you set your tire pressures correctly; and you do that from a cold start often enough for you to be confident that your tires pressures are correct for you & your riding.... some might take 10 set/check cycles, some might take 30, some might even take more... most take somewhere between 10 & 20 before they are reasonable confident! I dunno what it says about me, but while testing tires, I musta done it at least 100's of thousands of times, if not millions!!

    But yeah, it might sound difficult to someone looking for reasons not to bother, but it is way more difficult explaining it than it is actually doing it! In actual practice it takes just a few moments, 1/2 of them when you start getting your bike ready, cos you hafta check your tire pressure first (got FOBO?); then the rest of those few moments when you stop for whatever about an hour down track.... You might need to check pressures every time you ride for a week or 3 initially, just to get your pressures into the right ball park & learn to recognise what changing conditions can mean, but most work it out pretty quickly & then only make their regular pressure checks & adjust accordingly to changing conditions - and we all check our tire pressures at least once a week on our daily drive, don't we?! After all, your tires are the ONLY contact there is between your bike & the road, get the pressure wrong or treat your tires poorly & it's not only YOU who is likely to suffer!!

    The 4psi rule (or the even temp increase test) works on all tires, not just those on your Spyder... fronts, rears, OEM, A/mkt... if they are pnuematic car, bike, or even 4WD tires, the 4psi rule or the even temp increase test will work. These 'rules' are simply a consistent & repeatable way of checking that your tire pressures are close to optimum for what you & your riding style, loading etc is doing to your tires.... Look after your tires consistently & you'll get a better ride, better handling, even better tire life, as well as riding safer & looking after yourself, your ride, and the other road users around you.... is doing that too hard or too much to bother with?!
    Last edited by Peter Aawen; 10-13-2017 at 10:14 PM.
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    Quote Originally Posted by Wildrice View Post
    ...The chart shows the Diameter to be 5.4% larger on the 175/60/R15.

    Does this difference between rotation ratio vehicle speed front-rear tire get noticed by the "Nanny"?
    Darrell
    I'm also running a 225/60R15 on the rear Darrell. So, since I've increased both the fronts & the rear tire dia (& therefore tire rotational speeds) by very close to the same amount all round, the Nanny doesn't care at all!! In fact, if anything, she responds/intervenes FAAAR LESS now with the more robustly constructed tires running at the right pressures than she did with the crappy Kendas; altho some of that might be attributable to the more consistent riding style I've been able to develop with a better quality tire!

    But do remember that those charts are only based on the nominal tire sizes & don't necessarily reflect the real or actual variations between different manufacturers nominal tire sizes & tire types, etc - the differences between nominal & actual can be more significant than what you've highlighted, so you must check the actual specs on whatever tires you are contemplating using! Make sense?!

    Ps, and with that tire dia increase all round, my speedo accuracy is now spot on too!
    Last edited by Peter Aawen; 10-13-2017 at 05:21 PM.
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    Very Active Member jaherbst's Avatar
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    Quote Originally Posted by Peter Aawen View Post
    I'm running 175/60R15 Kumhos up front with 14-16psi in them and have no issues without any shimming or adjustments of the fenders; the only thing I've done is to swap the hex head screws on the inside of the wheel arch/fenders out in favour of lower pan head screws because the hex heads protruded out into the wheel space about 10mm & the pan heads sit pretty flush, not leaving anything for the tires to scrape on..

    I have heard/seen that some people running this sized tire at different pressures find that the tire flexes/distorts enough during hard cornering for the inside rear edge of the tire to scrape on the lower inside rear panel of the fender. I believe that this is happening because they are running pressures high enough that the tire cannot flex appropriately or quick enough during cornering so that the distortion caused by the cornering forces keep the tire distorted for longer than it would if the tire was running at slightly lower pressures. Certainly all those I've seen with this issue have been running pressures of 18-20 psi ir higher (because they felt that gave them 'more direct' steering, despite the clearly lower traction & performance evidenced on back to back slalom runs at different pressures) and the scraping stopped immediately they dropped 4 or so psi out of their tires, bringing their pressures down below 18psi. The front end of our Spyders really don't carry a great load, so they don't need a high pressure to help the tire support that load, and running pressures too high reduces the contact patch size & also forces the edges of the contact patch to lift during hard cornering, reducing it even further & holding that distorted shape for longer as the carcass of the tire rotates!! Slightly lower pressures help optimise the size of the contact patch & allow enough tire carcass flex to keep the tread contact patch firmly on the road surface instead of peeling an edge or side up & off the road, & releasing any carcass distortion almost immediately the tread leaves the road surface!!

    However, as those of us who have studied tires, pressures, & their use on vehicles are well aware, tire pressures are not a simple cut & dried one size fits all thing! Like the rest of us who have studied this, I am very aware that while running 'stronger' car tires on a Spyder rather than the lightly constructed Kendas definitely needs lower pressures, it isn't all that hard to go too low & drop your pressures below the optimum for the way YOU ryde & the tires YOU are running on your Spyder (or car, or whatever) so much so that while you will get better traction from the lower pressure, that traction comes at the cost of somewhat increased rolling resistance, sapping power & needlessly wasting fuel, as well as making the handling feel a little less than ideal cos it's so soft & spongy. Anything less than double digit pressure on a Spyder could be an issue this way! Still, the optimum tire pressure for your tires is a very personal thing, very dependant upon the way you ride & the tires you run, so what works for me may not be exactly right for you; but you can & shouldn't be scared of adjusting your pressures up & down a little from that optimum to work out what feels best for you & works best for your tires & the way you want to ryde.

    The 4psi rule can help get the optimum pressure for your tires; it aims for a 4psi increase in pressure after an hour's riding - more than a 4psi increase means your cold start pressure was too LOW, while less than a 4psi increase means your cold start pressure was too HIGH... OR you could use a temp sensor to check the tread temp at 3-5/7 or so places across the tread face & then check them again 30-60 mins later - an even temp increase across the tread face is what you want to see, while a hot strip on one side or the other of the tread face generally reveals an alignment or a loading problem; hot edge strips down each side of the tread indicates underinflation; & a hot strip in the centre of the tread indicates overinflation. These tools can help you arrive at the optimum pressure for your tires with regard to the way you ride, the load on your Spyder, the tires you have fitted, and the road surfaces you are ryding on, etc, resulting in you getting the best combination of ride, handling, traction, fuel economy, & tire life you can from those tires, and knowing that, you can generally make an informed decision on how that FEELS to YOU, or whether it will provide what YOU want from your tires, & adjust the optimum pressures up or down a little accordingly.

    Dropping your pressures a little below the ideal can soften the ride at touch, increase puncture resistance, & improve traction on marginal surfaces like wet or icy roads, but it will come at a cost in terms of greater rolling resistance, higher fuel use, & more tire wear on the edges of the tire, & if you go too low it can cause adverse handling and may also cause overheating & risk rolling the bead off the rim. Similarly, increasing your tire pressures a little above the ideal can improve the 'directness' of your steering (up to a limit, above which it just increases the potential for traction loss &/or rapid & unpredictable transition from understeer to uncontrollable oversteer or even causing the vehicle to roll!) but it comes at the cost of less traction & greater tire wear, increased risk of puncture from road debris or hazards, and a harsher ride, & if you go to far you can seriously compromise traction and handling as well as making the vehicle unstable at speed (or any speed!!)

    Hope that lot hasn't added too much to your ponderings, but with any luck, it may have helped others too!

    Ps: all other things being equal & with correct alignment, running slightly wider tires will generally increase the potential tire life, stability, & traction on dry surfaces that you can expect, as well as usually improving ride & handling. Running 'stronger' & slightly wider tires at the right pressures does all that too, but definitely will improve the responsiveness & handling of the vehicle as well as improving both wet & dry traction if you've got your pressures right, but it's essential that you get the pressures close to right, if they are too high the tire won't be able to clear water off the road surface or be at the correct temps to grip the surface properly... Lots of advantages to going up a size in width, IF you get your tire pressures right!

    Peter you need to settle down and get a job. You have far to much time on your hands to write this long Thesis. It would take me a week to write such a

    long article with only my index finger.


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  13. #13
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    Quote Originally Posted by jaherbst View Post
    ..... It would take me a week to write such a

    long article with only my index finger.


    Jack
    Being able to Touch Type at better than 50wpm helps, but seriously, modern Voice to Text software is a wonderful thing! Besides, a lifetime of service, studying, exploring, & gathering experiences doesn't need to end with retirement just because my body can't hack the pace any more; passing on whatever I've learnt helps me keep 'active'. If I put some of that collected knowledge out there, people can take it or leave it as they will, but no-one can say I've been sitting around doing nothing. And who knows, someone might even benefit from it!
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    Quote Originally Posted by Peter Aawen View Post
    It doesn't work that way newbert, since the total pressure increase from cold will vary somewhat depending on what your cold start pressures were - too high to start & the pressure won't go up any; too low & it'll go up a whole lot (pressures can almost double under adverse conditions!) You hafta start with checking your cold pressures, ride, check, adjust - and you might even need to do that a few times/over a few days to get it right, but it soon becomes just a matter of checking your tires as normal & maybe adjusting your cold start pressures in response to significant riding or condition changes (bloody hot days or long fast rides might need a little higher pressure than freezing cold days &/or tootling around the city! )

    And yeah, it might sound difficult, but it is way more difficult explaining it than it is actually doing it! In actual practice it takes just a few moments, 1/2 of them when you start getting your bike ready, cos you hafta check your tire pressure first (got FOBO?); then the rest of those few moments when you stop for whatever about an hour down track.... You might need to check pressures every time you ride for a week or 3 initially, just to get your pressures into the right ball park & learn to recognise what changing conditions can mean, but most work it out pretty quickly & then only make their regular pressure checks & adjust accordingly to changing conditions - and we all check our tire pressures at least once a week on our daily drive, don't we?! After all, your tires are the ONLY contact there is between your bike & the road, get the pressure wrong or treat your tires poorly & it's not only YOU who is likely to suffer!!

    The 4psi rule (or the even temp increase test) works on all tires, not just those on your Spyder... fronts, rears, OEM, A/mkt... if they are pnuematic car, bike, or even 4WD tires, the 4psi rule or the even temp increase test will work. These 'rules' are simply a consistent & repeatable way of checking that your tire pressures are close to optimum for what you & your riding style, loading etc is doing to your tires.... Look after your tires consistently & you'll get a better ride, better handling, even better tire life, as well as riding safer & looking after yourself, your ride, and the other road users around you.... is doing that too hard or too much to bother with?!
    No, it's NOT too much to bother with - Hence my questions. BTW - I DO have FOBO, and check it each time before I ride. It's just that I've been going by "feel" and making sure the 2 fronts are at equal pressure (or very close) and the rear is within range of what I've seen recommended here on the forums. (FWIW, I've been running 21-22 psi in fronts and 29.5 - 31 psi in rear).

    I agree with you 100% about checking tire pressures frequently. I just have never tried to find that 4 psi "sweet spot" (although I like the feel of my ryde at this point), but I'm interested in doing so. I just needed some further clarification on how to go about it.

    Thanks again!

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    You probably won't ever find a 'sweet spot' for tire pressures if you are still running Kendas, they are made very lightly & with so little regard for consistency &/or quality that they are just all over the place in most respects!! So far, all the collective experience gathered on this Forum has shown that it doesn't really matter much what you do with them, they provide mediocre grip & handling at best; altho you must be aware that their light construction necessitates those higher pressures shown on the tire placard. Very few people who've ever experienced the greater traction, better ride & handling to be had by running 'real' car tires at appropriate pressures on their Spyders would ever choose to go back to the lesser performing Kendas!

    More 'robustly' & consistently constructed car tires won't need pressures that high, since the stronger & better constructed car tires can easily carry the heavier loads imposed by a full sized car; in fact, if you run 21-22 up front & 29-30 psi in the rear while running 'real' car tires, I would be surprised if you got as much as 1 psi increase in their pressure after an hour's riding!! Pressures that high in a car tire mounted under a relatively lightweight Spyder won't normally allow the tire to flex anywhere near enough to generate the heat necessary for the tire/tread compound to reach it's designed operating temperature, so you will likely always be running with significantly less than ideal traction & a harsh ride, as well as exposing the tires to a greater risk of puncture or internal damage from road debris or hazards, and while you might get pretty good fuel economy, the handling will probably be pretty twitchy & you'll wear out the centre of the tire tread rapidly!

    Most reasonable or better quality car tires will only need about 14-18 psi up front to carry the load of the Spyder up that end, which is generally only going to be in thevicinity of about 250-300 lbs per tire or 500-600lbs total on the front end; while the single rear tire, being a bit wider & the only drive tire, as well as only needing to carry maybe something in the vicinity of 200-500lbs depending upon the model & the way you load your Spyder, will likely only need about 18-22 psi, altho some might run as much as 24 or so psi to give them more chance of 'drifting' the rear a little in the corners! Mind you, if you've been running your car tire pressures significantly too high for some time, it might take you a bit of a while to get used to the slightly softer but more responsive ride you'll get from dropping back down to pressures closer to giving you that 4psi increase or an even temperature increase across the tread face... but you WILL get better tire life, better traction, better directional control across all weather conditions, better puncture resistance etc, it just won't necessarily feel so 'rapidly directional' or 'darty' on dry smooth roads; but your tires, Spyder, & tailbone will thank you!
    Last edited by Peter Aawen; 10-13-2017 at 10:24 PM.
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