How important?

I know I am going to get beat up for this, but here is my tire question from the experts here on the board.

How important is the circumference of a rear tire? If I need a 55 circumference will a 50 be okay? And will it make a huge difference?

The reason I ask is because I thought I ordered a 205/55/15 Yokohama S Drive. Apparently they did not have the 55 because I ordered a 205/50/15. I ordered this tire at the beginning of the week, got it yesterday and noticed the difference. I am leaving on a 4 day trip and on the 4th day I have an appointment in Springfield, MO to get the tire changed on my rear tire.

Will the 50 hurt the Spyder or can I safely run this tire?

Thanks for your opinions, I really don't know what I would do without this forum and the dedicated people who post here. You are the true hero's.

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Originally Posted by Chiisai

I know I am going to get beat up for this, but here is my tire question from the experts here on the board.

How important is the circumference of a rear tire? If I need a 55 circumference will a 50 be okay? And will it make a huge difference?

The reason I ask is because I thought I ordered a 05/55/15 Yokohama S Drive. Apparently they did not have the 55 because I ordered a 205/50/15. I ordered this tire at the beginning of the week, got it yesterday and noticed the difference. I am leaving on a 4 day trip and on the 4th day I have an appointment in Springfield, MO to get the tire changed on my rear tire.

Will the 50 hurt the Spyder of can I safely run this tire?

Thanks for your opinions, I really don't know what I would do without this forum and the dedicated people who post here. You are the true hero's.

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Your wording is confusing to me , however the difference is sooooooooo minor the Nanny won't notice ..... the " 55 " is 8/10 ths. larger in Diameter and it will have 28 less revs per MILE ,,,871 vs. 899 for the " 50 " .....hope this answers your question .......... Mike ( the tire expert :roflblack: )

Enjoy your ride and new Rear Tire.

I don't agree, you are going from a 225x50R15 down to a 205x50R15 so you are dropping noticeable in both height & width. i don't know about the nanny but handling does change and keep in mind it will be a little bit of a stretch so
you will also lose a little more height because of that.

Thanks guys. I'm going to give it a try with the 50 circumference. If I notice anything weird, I will pull the tire off and get the right tire.

SPECTACUALR SPIDERMAN

I don't agree, you are going from a 225x50R15 down to a 205x50R15 so you are dropping noticeable in both height & width. i don't know about the nanny but handling does change and keep in mind it will be a little bit of a stretch so
you will also lose a little more height because of that.

Not sure where you got the 225/50/15 - the tire I have used in the past (and have on my Spyder right now) is a 205/55/15. The tire that I purchased is a 205/50/15. So all I am doing is losing some circumference.

A little more pulling power and a little man error. Both neglagable

Quote:

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Originally Posted by Chiisai

Thanks guys. I'm going to give it a try with the 50 circumference. If I notice anything weird, I will pull the tire off and get the right tire.

SPECTACUALR SPIDERMAN

I don't agree, you are going from a 225x50R15 down to a 205x50R15 so you are dropping noticeable in both height & width. i don't know about the nanny but handling does change and keep in mind it will be a little bit of a stretch so
you will also lose a little more height because of that.

Not sure where you got the 225/50/15 - the tire I have used in the past (and have on my Spyder right now) is a 205/55/15. The tire that I purchased is a 205/50/15. So all I am doing is losing some circumference.

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The original tire from the factory is 225/50R/15.

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Originally Posted by JFD

The original tire from the factory is 225/50R/15.

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My apologies. You are correct. I have been running the Yokohama S Drive on my Spyder since the rear Kenda wore out and I guess I just forgot what the size was on the Kenda. :opps:

As an added note, about 6 weeks ago I ordered 2 Federal Formoza's for the front. I have put around 7000 miles on them since their installation. I was not impressed with them. I was especially disappointed with them in the rain. I encountered 2 different times (2 separate rain storms) when I was propelled sideways on the highway at speeds of 30 to 40 miles an hour. It was almost like the tread on the Formoza's were directing the water in that direction. It scared me so bad that I have taken them off and have now installed a set of Yokohama Avid's.

What I experienced with the Federal Formoza's was not merely hydroplaning but a definite shove sideways. Last July I was in a horrible rain storm on a toll rode just outside of Tulsa, OK. The wind was blowing 60 to 70 miles and hour and the rain was coming down so hard that you could not even see the white or yellow lines on the highway. My Spyder kept straight with no hydroplaning. Believe it or not, I still had the Kenda's on the front. Absolutely no unusual movement during the 30 minutes I drove in the blowing rain.

What I experienced with the Formoza's during those 2 rain storms in the last 3 weeks really scared me so much that I slowed my speed down to about 10 miles an hour and then pulled off of the highway to sit out the rain in a restaurant.

I had the Avid's installed yesterday and today I took a 100 mile ride. I was more than impressed with the Avid's. The grip is phenomenal. They perform as well, if not better, than the S Drive that I have on the rear. I understand that the Avid's and the S Drive are softer rubber than other tires, and I also understand they will not get the same mileage as harder rubber tires. And that's okay with me.

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Originally Posted by JFD

The original tire from the factory is 225/50R/15.

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That's true, the OE Spec tire has a NOMINAL size of 225/50R15, but it is only the 'nominal' size, not necessarily the actual size, & for whatever reason, the Kenda tires supposedly specially spec'd for our Spyders are a pretty small tire - some 205/50 & 55 tires from other manufacturers are actually LARGER in rolling diameter & width than the Kenda 225/50's!!

Btw Chiisai, it's not actually the 'circumference' of the tire you are refering to when you are talking about the 55 vs 50 thing, it's the 'Profile' - circumference in tire parlance generally refers to the total distance a specific point on the tire's tread will travel over the ground when the tire has been rolled one full turn; while profile refers to the sidewall height as a percentage of the width, so a 205/50 label means the sidewall height is only 50% of the width, while it would be 55% of a 205/55 tire, & therefore a little larger.... which admittedly would also make the circumference a little bit bigger too!! ;)

But as inferred in my first para above, tires from different manufacturers & in fact tires from the same manufacturer but with a different tread pattern or type classification are labelled with NOMINAL sizes that may be somewhat different to the ACTUAL or physical size of the fitted & inflated tire!! I've seen tires wearing the same sidewall size but made by different manufacturers that had more than 50mm/2" difference in rolling diameter (& therefore had even more difference in circumference!!) despite supposedly being tires of the same 'nominal' size!! In your case, running an a/mkt alternative sized tire where you KNOW the higher profile tire fits & works fine, you can be pretty sure that if the lower profile tire fits safely on the rim (& it should, the difference is tiny!!) then it should be OK to run, albeit giving you a little more torque & slightly better acceleration at the cost of a touch less actual top speed teamed with a speedo that tells you that you're travelling faster than you really are (so you might not realise your top end isn't quite what it was with the taller tire) & an odo/trip meter telling you that you travelled further than you really did, too! And of course, the smaller tire might try to fool you that you are getting better fuel economy cos you think you travelled further, but the reality will more likely be that you are travelling less physical distance for any given qty of fuel!

As for your Federal tires experience, what tire pressure were you running in them? Tire pressure that's too high for the tire & the load it's carrying can mean that the tire tread will never get up to its optimum operating temp to work at its best, but more importantly in this instance, that the tread is just being held too rigidly to flex & grip the road and the tread blocks & sipes simply cannot flex enough to act and pump the water away from the contact patch in the manner intended.... and if the tires are also directional or even just semi-directional but fitted so they are rotating the wrong way, you can easily get that 'real push to the side' or 'direct the water in that direction' effect if you hit a slightly deeper patch of water!! Our lightweight Spyders really NEED lower pressures in 'normal' car tires for them to work at their best, especially in the wet - even if the tread compound is soft & sticky & works OK at car pressures on dry roads, running car pressures in them (ie, pressures that are too high for the load a Spyder imposes) means that the tread blocks & sipes etc simpy cannot work as they were designed to in order to push water away from the contact patch once things get wet!

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Originally Posted by Peter Aawen

That's true, the OE Spec tire has a NOMINAL size of 225/50R15, but it is only the 'nominal' size, not necessarily the actual, & for whatever reason, the Kenda tires supposedly specially spec'd for our Spyders are a pretty small tire - some 205/50 & 55 tires from other manufacturers are actually LARGER in rolling diameter than the Kenda 225/50's!!

Btw Chiisai, it's not actually the 'circumference' of the tire you are refering to when you are talking about the 55 vs 50 thing, it's the 'Profile' - circumference in tire parlance generally refers to the total distance a specific point on the tire's tread will travel over the ground when the tire has been rolled one full turn; while profile refers to the sidewall height as a percentage of the width, so a 205/50 label means the sidewall height is only 50% of the width, while it would be 55% of a 205/55 tire, & therefore a little larger.... which would make the circumference a little bit bigger too!! ;)

But as inferred in the first para above, tires from different manufacturers & in fact tires from the same manufacturer but with a different tread pattern or type classification are labelled with NOMINAL sizes that may be somewhat different to the ACTUAL or physical size of the fitted & inflated tire!! I've seen tires wearing the same sidewall size but made by different manufacturers that had more than 50mm/2" difference in rolling diameter (& therefore had even more difference in circumference!!) despite supposedly being tires of the same 'nominal' size!! In your case, running an a/mkt alternative sized tire where you KNOW the higher profile tire fits & works fine, you can be reasonably sure that if the lower profile tire fits safely on the rim (& it should, the difference is tiny!!) then it should be OK to run, albeit giving you a little more torque & better acceleration at the cost of a touch less actual top speed teamed with a speedo that tells you that you're travelling faster than you really are (so you might not realise your top end isn't quite what it was with the taller tire) & an odo/trip meter telling you that you travelled further than you really did, too! And of course, the smaller tire might try to fool you that you are getting better fuel economy, but the reality will more likely be that you are travelling less physical distance for any given qty of fuel!

As for your Federal tires experience, what tire pressure were you running in them? Tire pressure that's too high for the tire & the load it's carrying can mean that the tire tread never gets up to its optimum operating temp and that the tread is just too rigid to flex & grip the road and the tread blocks & sipes simply cannot flex enough to act and pump the water away from the contact patch in the manner intended.... and if the tires are also diectional or even just semi-directional but fitted so they are rotating the wrong way, you can easily get that 'real push to the side' effect if you hit a slightly deeper patch of water!!

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You had the best answer out of them all

Yes, Peter had the best answer and I thank you so much for the full explaination. This helps me so much to understand my tires.

Actually, the tire pressure I was running on the Formoza's was 20. I even had a comment from a man who mounted and balanced them that he did not understand how the bead would hold with a pressure of 20. Of course he put more air in them than the 20 so I let the air out until it reached 20.