Please educate me about tire sizes

[gianfri]

Hello, I need to replace the tires of my 2014 RT. I am confused about the size. I currently have 165/55R15 in the front and 225/50R15 in the rear (I think these are stock original tires). I am looking at car tires and cannot find an exact size match. What are the numbers that I must match? And for the other numbers, what differences in riding experience should I expect if I depart from what I currently have?

Thanks!

[SPECTACUALR SPIDERMAN]

Oy vey

[Batmobil-F3]

Hello gianfri,
here you find the tires in the desired size
165/55R15 https://www.carid.com/tires/165-55-r15/
225/50R15 https://www.carid.com/tires/225-50-r15/
The original Kenda tires tend to aquaplaning, so many Spyder riders switch to other brands.

[CopperSpyder]

https://www.spyderlovers.com/forums/...n-Tireshttp:// Go down to post #5 look over the thread also do a search to find other info.

[h0gr1der]

Quick answer is there is little to no support for our exact tire size, AND IMHO the O.E. tires are raging crap. So with all that said, here goes. I'm a newb going through the same things.

Combinations that work (from what I've read).

175/55R15 Front with 205/60R15 Rear. Using generic numbers there's about 1.8% difference from O.E. roll-out overall.

175/60R15 (165/65R15 alternate) Front and 215/60R15 Rear. Same as above, but even less rolling difference. .4% from O.E. tires roll-out.

Why is the difference in tire rollout important? I don't know for sure, but I've read some references to the Nanny (this thing has more computer control than the space shuttle) having a problem with overly large rear tires, causing limp home mode. Good idea to keep the ratios of increase front to rear the same, or as close to the same as feasible. Understand, each tire manufacturer may not have the exact spec size for a given sidewall measurement, meaning one guys 205/60R15 may be larger or smaller diameter and/or width than the other guys.

There is a few tire brands I've read about. I'm currently trying the Vredestein Quatrac 5. You have to source them from different places. Tire rack has the fronts, Vulcan tire has the rear, but they have a 1 month processing time for the single tire.

Other brands I've read good things about. General Altimax RT43 for the Rear. Yokohama S Drives. Continental ContactPro. It's hard to match front and rear brands and styles. Check the UTQG and traction ratings. The Altimax has a 700 UTQG rating, which may mean a whole lot of mileage before wearing out. Better if you like traveling more, wrenching less. May not handle as good, but I can't comment on that as I haven't run one. My first set is the Vredesteins, they have a UTQG rating of 400. Kind of a mid range mileage tire. But may stick better because of softer compound. Dry handling isn't as important to me as wet handling because of my driving style. Slick roads pose the biggest hazard to me, so that's what I focus on. Some other brands of tires not mentioned here lose wet traction at about half wear (as reviewed by others). Read a lot, search hard and long before making your decision. A poor choice on the front is easily remedied, a lot of car tire places can mount new ones for cheap. The rear is a pretty big obligation to change, so make a wise choice.

Also, be aware you are running car tires, designed to carry more weight than the Spyder. You may be using less air pressure than you are used to. I'm currently in tire testing, and I'm down to 18 PSI on my front 175/55R15 Veredesteins. (Read about the tire 4 PSI rule). At 20 PSI, the tires only increased 2 PSI, indicating a slightly high pressure. I've lowered the pressure to 18 PSI, waiting on weather to re-test.

Do not decrease the pressure on the Kenda tires. I had 28 PSI in the rear for the first test and it did build to 32 PSI. My front Kenda's came off at 804 miles due to unable to balance. They were out of round. With Kenda it's hit or miss. I got some bad ones. Weighed each tire, there was a 10 ounce difference in the weights.

Hope this helps to start the journey.

[Bob Denman]

Tire discussions ranging from what size... to what brand... to even what type: have been ongoing in here ever since these things have been on the market.
I hate to say it; but my head hurts from them!
If you use the "Search" feature: you'll have enough reading for a lifetime!
Happy hunting!

[Highwayman2013]

Google the front tire size and you will find options. I use the Federal Formoza AZ01 in the stock size,. The rear is harder but the 215/60/15 size has many options and I am using a General Altimax RT43.

[gianfri]

Tire discussions ranging from what size... to what brand... to even what type: have been ongoing in here ever since these things have been on the market.
I hate to say it; but my head hurts from them!
If you use the "Search" feature: you'll have enough reading for a lifetime!
Happy hunting!

That is exactly my problem. I just do not understand what measures from my original tires can be different in the new tire. I suspect the wheel size (15) cannot be changed. How about the first two numbers (in my case, 225/50 rear and 165/55 front)? Can those be different from the original tires? If so, by how much? And what is the effect of a greater or smaller number?

[gianfri]

Google the front tire size and you will find options. I use the Federal Formoza AZ01 in the stock size,. The rear is harder but the 215/60/15 size has many options and I am using a General Altimax RT43.

I was looking at the same front tires: Federal Formoza AZ01 All-Season Radial Tire - 165/55R15, same size as my current ones.

The current rear size is 225/50R15. Can I exchange for a 215/60R15? If so, what difference would that make to the riding? and can that be matched with front size 165/55R15?

As you can see, my knowledge in the area is quite limited. Thanks!

[h0gr1der]

gianfri,

Ok, now head on over to https://www.tirerack.com/content/tir...ch_advice.html and do your due diligence. Read about tire sizing and measurements for a few days. Try to understand, it is put in very simple language.

[Lew L]

Yes, they can be changed. Usually going up or down one step/ size causes no problems and may cure some. BUT----- please read the many tire topics that have already been discussed here for your answer--- as it may not be my answer.

[Peter Aawen]

You surmised right about the 15 gianfri, which is the rim dia the tire is made to fit on expressed in inches (yeah, I know the units are a mix of imperial & metric, but that's just the way it is!?) The 225 bit of 225/50R15 is the width of the tire body in millimetres, not necessarily the tread width altho it's going to be fairly close; while the 50 is the sidewall height expressed as a percentage of the 225mm. Similarly, the 165 of 165/55 is width in mm, with 55 being the sidewall height as a percentage of the 165mm.

Rear tires can't go much wider, due to the belt & sprocket, but they can go a little taller, ie, 225/60R15's will generally fit on an RT - the only increase is sidewall height, but that does mean the rolling diameter of the tire will generally be a little larger. For that reason many drop the width, ie, go for a 215 or even a 205, as well as a taller sidewall height, ie 60 or possibly even 65, in an attempt to keep the rolling diameter close to the same as the OE tire. Usually, you'd select a 215/60 or a 205/65, but just to make things a little more difficult, the tire sizes shown on the sidewalls are only NOMINAL, and very few tires with the same sidewall nominal size are actually physically the same size.... they are just somewhere about that nominal size, altho the differences can be as much as 20mm or more difference in rolling diameter!!

Front tires can go a bit wider but not much taller, the max for the 15" rims generally being about a 175/60, altho there are a few who've managed to find & fit 185/50's or even a (small) 185/65!! Still, I'd work to 175/60 being about as big as you'd want to try without a test fit, and even so, you might need to ease the lip of the fender over the tire during fitting, just to get it on - once on, they usually run OK if the fender supports aren't bent, altho some have swapped all the hex head screws under the fender for dome type phillips head screws to minimise the chance of the screw heads rubbing on the tires as they rotate.

Why go bigger, apart from finding a tire to fit that isn't the OE stuff? A slightly larger tire size will generally have a slightly larger footprint on the road, and it's that footprint that provides traction. A larger area can mean better grip, especially if the footprint has increased proportionally more in length (along the line of travel) than it has increased in width, but that traction increase & to a certain extent, the longer more than wider footprint generally only occurs if the tire's pressure is a little lower, and that's a whole 'nuther discussion. Still, if the footprint is a longer than it is wide footprint, you'll generally get better traction/grip & directional stability and depending upon the wheel alignment being correct, you can also get a longer tread life to go with that better grip. The risks are that a less efficient tread pattern on a larger tire (especially wider) can mean there's slightly more propensity for hydro-planing, but once again tire pressure plays a big part in avoiding that; and a longer &/or wider footprint will make for a little more steering effort, but with the increases in length & width we are talking about here, you'd need some fairly sensitive equipment to measure it, unless there were other issues at play (like poor wheel alignment for one...)

The slightly narrower but taller profile rear tire can mean marginally less outright traction on dry roads, but a good wet weather tread pattern can counter that minor issue by providing noticeably better traction, especially in wet weather & less propensity for hydro-planing on wet roads; and the slightly larger rolling diameter will not only help make the (by manufacturers design) up to 10% optomistic speedo/odo readings more accurate, bringing them to within 1 or 2 mph/miles of actual instead of reading over as they do, but it will also help the tire achieve a longer tread life & have less of a tendency to 'throw the center of the tread out whole rotating' so the tire shouldn't wear the center of the tread out anywhere near as much as the OE Spec tires do!

Help any gianfri?

[gianfri]

You surmised right about the 15 gianfri, which is the rim dia the tire is made to fit on expressed in inches (yeah, I know the units are a mix of imperial & metric, but that's just the way it is!?) The 225 bit of 225/50R15 is the width of the tire body in millimetres, not necessarily the tread width altho it's going to be fairly close; while the 50 is the sidewall height expressed as a percentage of the 225mm. Similarly, the 165 of 165/55 is width in mm, with 55 being the sidewall height as a percentage of the 165mm.

Rear tires can't go much wider, due to the belt & sprocket, but they can go a little taller, ie, 225/60R15's will generally fit on an RT - the only increase is sidewall height, but that does mean the rolling diameter of the tire will generally be a little larger. For that reason many drop the width, ie, go for a 215 or even a 205, as well as a taller sidewall height, ie 60 or possibly even 65, in an attempt to keep the rolling diameter close to the same as the OE tire. Usually, you'd select a 215/60 or a 205/65, but just to make things a little more difficult, the tire sizes shown on the sidewalls are only NOMINAL, and very few tires with the same sidewall nominal size are actually physically the same size.... they are just somewhere about that nominal size, altho the differences can be as much as 20mm or more difference in rolling diameter!!

Front tires can go a bit wider but not much taller, the max for the 15" rims generally being about a 175/60, altho there are a few who've managed to find & fit 185/50's or even a (small) 185/65!! Still, I'd work to 175/60 being about as big as you'd want to try without a test fit, and even so, you might need to ease the lip of the fender over the tire during fitting, just to get it on - once on, they usually run OK if the fender supports aren't bent, altho some have swapped all the hex head screws under the fender for dome type phillips head screws to minimise the chance of the screw heads rubbing on the tires as they rotate.

Why go bigger, apart from finding a tire to fit that isn't the OE stuff? A slightly larger tire size will generally have a slightly larger footprint on the road, and it's that footprint that provides traction. A larger area can mean better grip, especially if the footprint has increased proportionally more in length (along the line of travel) than it has increased in width, but that traction increase & to a certain extent, the longer more than wider footprint generally only occurs if the tire's pressure is a little lower, and that's a whole 'nuther discussion. Still, if the footprint is a longer than it is wide footprint, you'll generally get better traction/grip & directional stability and depending upon the wheel alignment being correct, you can also get a longer tread life to go with that better grip. The risks are that a less efficient tread pattern on a larger tire (especially wider) can mean there's slightly more propensity for hydro-planing, but once again tire pressure plays a big part in avoiding that; and a longer &/or wider footprint will make for a little more steering effort, but with the increases in length & width we are talking about here, you'd need some fairly sensitive equipment to measure it, unless there were other issues at play (like poor wheel alignment for one...)

The slightly narrower but taller profile rear tire can mean marginally less outright traction on dry roads, but a good wet weather tread pattern can counter that minor issue by providing noticeably better traction, especially in wet weather & less propensity for hydro-planing on wet roads; and the slightly larger rolling diameter will not only help make the (by manufacturers design) up to 10% optomistic speedo/odo readings more accurate, bringing them to within 1 or 2 mph/miles of actual instead of reading over as they do, but it will also help the tire achieve a longer tread life & have less of a tendency to 'throw the center of the tread out whole rotating' so the tire shouldn't wear the center of the tread out anywhere near as much as the OE Spec tires do!

Help any gianfri?

Fantastic explanation, thanks. So right now I am considering the 215/60R15 General for the rear (to replace the current 225/50R15) and the federal 165/55R15 (same size as the current tires) for the front. It sounds from your writing that that should be a good combination, do you agree? Thank you!

[gianfri]

gianfri,

Ok, now head on over to https://www.tirerack.com/content/tir...ch_advice.html and do your due diligence. Read about tire sizing and measurements for a few days. Try to understand, it is put in very simple language.

Good resource for a general understanding of how the measurement system works, thank you. I still have some practical questions, which hopefully are being/will be answered in this thread.

[Revalden]

I just changed my fronts to 165/55/15 Federal Formoza AZ01 at only 10,000 miles and they looked fine. But my fellow Spyder Riders recommended the AZ01 for better cornering and ride quality. I looked all over trying to find them, but found them online at WalMart.com shipped for free. $108.00 for the pair. Had them mounted at my favorite tire shop partly cuz WalMart shop was hectic. And I had them filled with Nitrogen.

[canamjhb]

gianfri, Many of us have been through the learning process you are experiencing. There is a lot of good information in this thread in addition to others that have been previously posted. The short story..... You can usually go up or down one size on either or both axels without upsetting nanny. If you go with a 215/60R15 rear, you will eliminate almost all error that your speedo has. Whichever brand CT you choose will be a good improvement over the Kendas. After much head scratching and indecision, I settled on a General Altimax RT43, 215/60R15 for the rear. For the fronts I went with Federal Formoza AZ01 at 175/55R15. All fit well and I am happy with the performance. I went with the 175 fronts instead of the 165s because I wanted a little more rubber on the road. (And I think they look better.) I have just a little over 20,000 miles on these tires and they look great. I expect many, many more miles from them. And I run 18psi in all 3 tires. Hope this helps a little. Good luck..... Jim

[gianfri]

gianfri, Many of us have been through the learning process you are experiencing. There is a lot of good information in this thread in addition to others that have been previously posted. The short story..... You can usually go up or down one size on either or both axels without upsetting nanny. If you go with a 215/60R15 rear, you will eliminate almost all error that your speedo has. Whichever brand CT you choose will be a good improvement over the Kendas. After much head scratching and indecision, I settled on a General Altimax RT43, 215/60R15 for the rear. For the fronts I went with Federal Formoza AZ01 at 175/55R15. All fit well and I am happy with the performance. I went with the 175 fronts instead of the 165s because I wanted a little more rubber on the road. (And I think they look better.) I have just a little over 20,000 miles on these tires and they look great. I expect many, many more miles from them. And I run 18psi in all 3 tires. Hope this helps a little. Good luck..... Jim

You're right, there's a lot of good information. Nothing can replace stories from real people who went through the same process. Thank you!!
Did you have any problems fitting the bigger front tires in the fender?

[DGoebel]

gianfri, I'll piggy back Highwayman2013 above and I too use the Federal Formoza AZ01 in the stock size. The rear is harder but the 215/60/15 size has many options and I am using a General Altimax RT43.

[Peter Aawen]

Fantastic explanation, thanks. So right now I am considering the 215/60R15 General for the rear (to replace the current 225/50R15) and the federal 165/55R15 (same size as the current tires) for the front. It sounds from your writing that that should be a good combination, do you agree? Thank you!

If you are doing the rear tire now and the front tires later, there's a slight possibility that you'll have a few more Nanny interventions once you've got the bigger rear tire fitted and before the fronts go on, because the OE Spec Kendas are 'small' tires & the General & Federals aren't. So if you fit the rear first & give your Spyder a 'tail up' attitude, the Nanny might react to a few corners or other things she wouldn't normally get upset by, but it shouldn't hamper your normal ryding or in fact even spirited ryding much at all, she'll just kick in a touch earlier every now and then. And it'll only last until you fit the fronts too. However, if you are replacing all your tires at once, I reckon you'll be so pleased to be suddenly ryding on tires that grip & point & turn in when you want them to and all those other things that good tires do you'll be so stoked, and your 'miles of smiles' grin will be even wider!!

[gianfri]

If you are doing the rear tire now and the front tires later, there's a slight possibility that you'll have a few more Nanny interventions once you've got the bigger rear tire fitted and before the fronts go on, because the OE Spec Kendas are 'small' tires & the General & Federals aren't. So if you fit the rear first & give your Spyder a 'tail up' attitude, the Nanny might react to a few corners or other things she wouldn't normally get upset by, but it shouldn't hamper your normal ryding or in fact even spirited ryding much at all, she'll just kick in a touch earlier every now and then. And it'll only last until you fit the fronts too. However, if you are replacing all your tires at once, I reckon you'll be so pleased to be suddenly ryding on tires that grip & point & turn in when you want them to and all those other things that good tires do you'll be so stoked, and your 'miles of smiles' grin will be even wider!!

How about if I do the front first?

[h0gr1der]

That's where I'm at. To be honest, the O.E. Kenda rear tire is OK. Not great, but usable. I replaced the fronts first because it's easy and a lot of car tire changing places can do the swap for you. If you can change a spare on your car, you can pull the fronts off the Can Am Spyder. 3 lug bolts, a jack stand under each side, good to go to the tire place. My fronts were bad, and the swap was very much well worth it. The rear is more involved, and if you're not fairly proficient with basic hand tools and mechanical principal, you may be better off having someone do the work for you. For the 2014 Spyder, there are going to be some additional mechanical recommendations, bearing inspection, belt inspection, brakes, etc. while you have the wheels off.

[BLUEKNIGHT911]

If you are doing the rear tire now and the front tires later, there's a slight possibility that you'll have a few more Nanny interventions once you've got the bigger rear tire fitted and before the fronts go on, because the OE Spec Kendas are 'small' tires & the General & Federals aren't. So if you fit the rear first & give your Spyder a 'tail up' attitude, the Nanny might react to a few corners or other things she wouldn't normally get upset by, but it shouldn't hamper your normal ryding or in fact even spirited ryding much at all, she'll just kick in a touch earlier every now and then. And it'll only last until you fit the fronts too. However, if you are replacing all your tires at once, I reckon you'll be so pleased to be suddenly ryding on tires that grip & point & turn in when you want them to and all those other things that good tires do you'll be so stoked, and your 'miles of smiles' grin will be even wider!!

You know I agree with 99.99999999999999% of the time, but He isn't going to encounter any issues with that tire set-up ….. If He was switching to 13 inch wheels and tires probably, but not otherwise …… Mike

[Peter Aawen]

Front first still has a 'slight' chance the Nanny will react a little bit quicker, but it really is slight, and the better grip you get will transfer into better directional control and ryding.

With the bigger rear going on first, you'll get very mild understeer, where the Nanny might feel you are going into a corner slightly over-cooked, the slightly changed front/rear heights will fool the sensors into thinking you've turned hard but the Spyder isn't responding as fast as you've turned, so she'll maybe try to stop the Spyder over-running the front tires - which she WILL do if that really does happen anyway! But if you do the front tires first you'll have better, quicker, & more direct turn in so the tail may feel a fraction loose, so the Nanny might be fooled into thinking that you've turned to hard too fast, so she'll maybe try to stop you hanging the tail &/or spinning - which she WILL do if that really does happen anyway!

So whichever end you do first when you are changing tire sizes, there will be a SLIGHT CHANCE that the Nanny MIGHT try to intervervene a little more often or earlier in some instances until you fit some correspondingly taller tires on the other end! Please note the words in caps - SLIGHT, CHANCE, & MIGHT. That is not a certainty, this 'earlier intervention' is very much dependent upon a heap of things including how hard you ryde & how sticky the road surfaces you ryde on may be, but there is a SLIGHT chance that it MIGHT occur, & that can be surprising if you haven't been warned, so here's the warning. But it is a VERY slight chance and even if it occurs it shouldn't be anything drastic or upsetting or even dangerous - the Nanny we have in our Spyders is one of the best in the game at keeping you safe - most of the time you'll be hard pressed to notice any intervention anyway.

This is something that you don't need to be upset about at all, you probably run a greater risk of falling over at home than you have of your Spyder's Nanny really surprising you. Just be aware that if you change the tire size on one end of your Spyder & not on the other at the same time, because you have such a great Nanny, she might intervene just a little more often than you've become used to until you change the tire/s on the other end to correspondingly taller tires. Heck, I know for a fact that there are some people out there who have purposefully fitted slightly taller tires up front and noticeably smaller tires on the back just so they can do things within the scope of the Nanny's intervention parameters to make their ryding more exciting!! Then they've discovered that the only thing about doing is that by varying tire sizes in the way they have, they've already used up some of the Nanny's safety margins so now she steps in earlier when they try to drift so they've got no nett gain!! She's a really smart piece of kit, our Nanny!

Fit whichever end first you need to, & ryde it until you need to do the other end, safe in the knowledge that your Spyder's Nanny WILL be doing her thing all the time to keep you safe, and there's not a heap of things you can do that will escape her attention! She's STILL gonna be looking after you whatever you do! And that shouldn't detract a heap from your ryding enjoyment, altho it might just help you develop better ryding skills once you work out where & why she's intervening so you can practice ryding right up to but not over the boundaries she sets!

[h0gr1der]

My station is as a cruiser rider, not one of the racers. With the 175/55R15 Vredestein Quatrac on the front, and the OE Kenda on the back, I can say I've never been slowed down by the Nanny. Haven't yet rode in the rain, prefer not to but it's inevitable. I've taken turns harder than I ever dared to on cruiser type bikes, had all 3 tires squalling in one fairly sporty turn. I've owned the bike 17 days, about 8 of which were ridable. I've only had the fronts installed for about 200 miles, dry riding conditions only so that's all I can address. I think any of the mentioned tires is better than the O.E. Kenda tires. My bike tracks truer, and turns better with the tires I have on it.

[Ibified]

https://tiresize.com/calculator/

Great source for sorting out outside diameter on your tires. Simple explanation:

First number: the overall maximum width of the tire, in millimeters when mounted on a standard width (for specific tire size). This is not the width of the tread.

Second number: this is what's called the aspect ratio. A 55 series tire, for example, with have a sidewall height that's 55% of the first value. A 275/55-15, for example, will have a taller side wall than a 195/55-15, because 55 percent of 275 is more than 55 percent of 195.

Third number: wheel diameter - pretty self explanatory.

There are a bunch of other numbers and letters on the tires too, but you can probably look those up. If you have any questions, please feel free to pm me.

I worked at a tire shop through college - I'm familiar with most things having to do with tires.