Quick Question about tires.

I'm working on an 83 Yamaha XJ550SECA. I've been looking and I cant see that anyones tried to fit 110/90-19 tires on the front with 110/90-18's on the back. Not terribly worried about keeping it original. I have heard that 120/90-18's wont fit on the back. Anyone experimented with those tire sizes? Would the 110/90-19 tire clear the front fender?

 

A 120 will fit on the rear, but will be a little tight (a 120 rear was fairly common to use when racing). You really don't want to run the same width front and rear as it will tend to slow down the steering.
Unlike car tires, wider does not automatically equal better performance.

Either run stock sizes (metric equivalent is 90 front, 110 rear if you want more choices), or go 110 front and 120 rear (yes the 110 front will clear the fender).

 

Are you sure a 120 will fit on the rear? I wasn't planning on putting the same exact size on front and back. I was hoping to get 110 up front with a 120 on the back, if thats not gonna work i'll just buy the 100 front and 110 back. Just feeling it out before I buy tires. Mine have dry rot and leaks all over right now, so im going to have to get tires before I can do much of anything with it.

 

I know that others have sucessfully put a 120 on the rear. I am not sure of which 120 that is though (a search might help you find out).
Sidewall profile will matter since there isn't much room.

If you go with a 110 rear I think you'd be better off with a 90 up front. There is a ratio (the formula for which I can't remember to save my life) that describes how tire with affects turn-in speed. The basic rule of thumb (from what little of my memory is left) is to have 20 mm difference between the front and the rear to keep that ratio in the sweet-spot.

 

Sounds good to me! Thanks so much for the info! I was looking around and have seen some "cafe" style bikes that have bigger than stock front tires. why would someone do this? (it does look pretty "beefy") Just for Looks or does it serve some other purpose that is unknown to me?

 

There are a few who have put a rear tire on the front. I think it's just for looks. To my understanding, it would harm performance, making steering more difficult.

 

I just bought Avon A26's for mine. Correct sizes. About $180 for the set from Motorcycle Superstore.
Called around locally for mounting. One place said $20, the other $50 per. I suspect the 2nd place didn't hear me say the wheels were off the bike.

 

Here's a great article about the best tire size for the Seca 550
http://www.foreven.com/motorcycles/Tyres/YaSeca55.htm

 

I posted that last week and k-moe pointed out (rightly so), that it's 17 years old now. Sizing information is good, but shop for current tires.

 

Of course, call the 1st place back now and w/ my own tires, they want to charge $50 per. Now says $20 was if I bought from them. sheesh. What's reasonable for this? Sounds like $50 each, huh?

 

Get a set of motion pro tire irons/spoons (3 minimum) and a wood clamp or large zip ties , and do it yourself.

 

Front tires are made of a softer rubber compound for enhanced grip in corners. Rear tires use a harder compound for durability, plus it carries the most weight.
Rear tire up front will affect your steering. Front tire in the back will wear out quickly.

 

I assumed he was asking about the swap where you put a rear rim on the front. It looks kinda heavy and bulky, everything that a Seca is not supposed to be. It's a sport bike, dammit!

 

The second place is in line with shops that would prefer you also buy the tires from them.

 

And tire lube, and wheel weights, and a pair of jack-stands to rest the axle on while you blanace the tire.
It really isn't a hard job, but the first time can be a hassle.

I found the zip-ty method for tire mounting to be impossible for the rear tire I chose.

 

120 on the rear fits and works fine, it's all I've ever run, as for 110 on the front I wouldn't waste my time as the front rim is too narrow and unless your aim is to make it handle worse and turn slower 100 on the front would be the widest I'd run

Is this about looks or performance?

 

Ita just a question of how much going up a size, front and rear, so 100 up front instead of 90, and 120 in the rear, instead of 110. Wondering how much performance is actually lost, as well as if there were any benifits to it at all. Curiosity in general. I'm needing new tires and i'm not really feeling the "Rail thin" tire up front, I dont want anything silly, just wondering whats usable, without major drawbacks. If I can fit a 120 in the back GREAT! ill use that, but a 90 up front? Just looks awkward to me. If it works the BEST then I'll probably stick to that tire size. if it wont hurt going to a 100 up front and a 120 in the back.... I'll probably do that instead. Plus I ride like an old man. I'm gonna be hard pressed to find a bunch of twisties out where I live anyways.

 

Funny, that's exactly what the formula is for though------

 

The formula is a bit more involved than a straight ratio. It describes the effect of the roll-rate of a motorcycle when the distance through which the tire (tread at the contact patch) must roll is changed. And that is just the first part. Then there is the relationship between the roll rate of the front and the roll rate of the rear. I wonder which of my oft-neglected books it is in...


Oh wait...you made a joke. Too much time in the heat for me today lol

 

Just to muddy the water a little bit...
I fitted a 100/90x18 rear on the front of my XJ9, after careful examination of the profile of the old BT45 that was on there, and the new tyre - a Maxxis C907. Interestingly, I could find nothing anywhere that actually designates the C907 as rear-only. So, I gave it a go, and it handles and grips exactly the same as the BT45. It doesn't look any beefier though, and it has at least 50% more tread depth than the C906 I would have fitted. I'll see how long it lasts and how it behaves as it wears.

 

Another thing to consider is that just because a tire says it has a certian width, does not mean that is the actual tread width of the tire. There is a bit of wiggle-room to allow for differences in manufacturing.

 

All Good Info. Thanks Fellas