Another Tire Question Thread

Hey guys,
I've been restoring my '82 SECA 750 and the last item I need to aquire is a rear tire to replace the Dunlop D404 which has chicken strips showing.

My concern is that I replaced the front tire last year with a 110/90 19 Metzeler ME880, which is 10 larger on the width. than the recommended 100/90.
My second concern is that the ME880 isnt available in 120/90 for the rear, however the Lasertec is offered in the 120/90

So my question would be, is it okay to run a wider tire in the front and rear?
Would I be better buying the lasertec which is gonna wear significantly faster than the Marathon I have in the front? What other tires would you recommend to compliment the me880 in the front.

Oh and I did find a ME88 in 120/90 on Dennis Kirk, but is this old tire worth $150. I thought they stopped making me88's?
Thanks in advance guys

 

You can go up to a 130 in the rear I bet, I did on my Seca 550. Make sure the tire has not been sitting around for several years. I would look at this tire for the rear.
http://www.motorcycle-superstore.com/14 ... -Tire.aspx

As long as you keep biased ply front and back there is nothing wrong with mixing the brands up.

 

I went 130 on both my Seca 750 and 900.

Whoever is selling you the tire should read you the date code - and they can legally sell the tire as "new" up to 4 years old - which sucks, so buyer beware !!

And the "chicken strips" are not the wear bars, but the portion of the edge of tread that the "non-peg-draggers" never use.

 

Lol Yeah Im a non-peg-dragger for sure. Im mostly highway and the roads are pretty straight and uneventful here in DFW Texas. The center of the tire has little tread left but the outer portions have plenty of tread. I figured thats why I'd be happy with a harder compound like the Marathon 880 and not the sticky Lasertecs

And I seem to read a lot of good things about the spitfire maybe I'll try it out.

I wonder if I should get the 130/90 18 for the rear since I'm already running a 10mm oversize in the front or just stick with the 120/90? I dont know how much the width effects the height or whether there would be any negative effect on the handling(though I assume the effect would be greater on the front).

And Im definately wary of the me88 because I'm assuming it dated even if they label it new. Guess I can try calling them and finding out.

 

The tire is shaped so it has the proper contour when mounted on the correct rim. If you go to a 130 it'll be pulled tighter at the rim than it was shaped for. It'll be rounder which will make it wear faster in the center.

The big question is how much faster.........

 

Going from a 120/90 to a 130/90 is going to be wider on each side of the tire by just less than 1/5 an inch as your increasing the overall width by 10mm total so each side is 5mm wider.

As far as height (diameter) your increasing the tire width by ~8% while maintaining the ratio (90) so the diameter will increase by 8% as well. On a 130/90 tire the stated tread width is ~5.1 inches, this is measured not across the tread path like it is on an auto tire but is measured at either just below the tread line or just above where the bead transitions to sidewall. A typical 130 tire will be around 5.5 inches wide (tread) and 5.1 inches at the bead transition. Typical 120 tire will be 5.1 inches wide (tread) and 4.7 inches at bead transition.

Although MiCarl is technically right about the change in conformation, tires are not 'one rim size only' constructions as they must be flexible because even rims rated the same width vary btn manufacturers. But to address his 'big question' since it is valid-the difference in the final tread chord (that shape a rounded tire has) could approach 4% but usually is less than max. Presuming this would equate to an equal amount of added wear (untested presumption) then a tire that you would get 10,000mi out of would wear out 400 miles sooner. Not much difference.

If you put a 130/80 18 on there you would have a stiffer sidewall and a decrease of overall diameter by just under 2%-not sure if you want that but it would be even closer to your stock as far as diameter. The 130/90 18 will increase your overall effective gear ratio slightly giving you slightly better top end or lower rpms at the same speed as before. The 80 ratio tire would lower overall e gear ratio and increase torque application (albeit very little difference). It would also be less likely to change conformation due to the stiffer shorter sidewall.

You would be fine either way. The fatter tire will improve traction under all conditions, so better BRAKING!!! Yea. fatter=better in this one instance.

One caveat is that occasionally an existing stock tire is already at the limit for the rim it is on (not the case with your seca and rare) if so the bead can pop off under lateral force. Sorry for information overload but realizing that tires are where 'the rubber literally meets the road' and hence control meets your but-I have spent too much time obsessing and learning 'tire lore.'

 

The bottom line being yes you can go "up" one size, front and rear, without any dire consequences.

 

Thanks for all the responses guys. I think I'll order the Spitfire for the rear in the 130/90 to balance out the wider front tire(I dont want the bike pitched unlevel). I also like what MercuryMan said about the higher gear ratio, since I'm going to be commuting 35 miles away all highway, top end is more important to me.
Maybe next tire change I'll go back to the OEM sizes

 

Or not... For some reason, Yamaha tended to install "undersized" tires on their bikes of the era, even by 1980's standards. A good example is the 550 Seca; the OE size rear is only a 110 when a 120 clearly fits and is a marked improvement. Fronts were often a 3.00 or 3.25 even on bigger bikes.

Even back then, when I put new tires on my Yamahas, I went one size up from stock.