Triumphrat

Lucid · 07-20-2008

Well after 11k on the stock Metzlers, I find myself in need of some new rubber. I'm not sure which tire I'm going to get yet, but, I have a question about sizing.

I'm thinking of going to a 140 on the rear, but, don't want to negatively affect handling. If fact, I'd like the bike to actually handle a tad quicker in the twisties. Therefore, would it make sense to go w/ a 140/80 and a 110/80 on the front to put more weight toward the front of the bike? Any thought or past experiences would be appreciated.

And not to turn this into a "what is the best tire" thread (beaten to death and highly subjective), but, I'm currently considering the Sport Demons (would be my first choice, but concerned about durability), Avon AM26 Roadriders, and have read some good reviews about the Conti Road Attacks (in my research it seems the narrowest rear is 150, which I think is wider than I'd like to go).

BTW- I was never in love w/ the Metz, which is why I'm considering a change

Gob-ny-geay · 07-20-2008

Thinner is better if you really want a bike to go faster through the twisties. The tire geometry is a very precise science, and front/rear sizes need to be calculated in carefully to give the best results. Changing the rear size without considering the front would give poor handling results.

The thinner the profile, the easier it is to "flick" through the turns. The wider profile tires will resist the lean over, which is what makes those "artistic" choppers so difficult, or near impossible, to handle.

Many books and studies done on this subject, most likely available at your local Borders, or other Bookstores. Suiffice to say that yes, you could change the rear tire width, but I would recommend considering a calculated change to the front as well for best results.

Lucid · 07-20-2008

Quote:

Originally Posted by Gob-ny-geay

Suiffice to say that yes, you could change the rear tire width, but I would recommend considering a calculated change to the front as well for best results.

Bob,

In my initial post I reference the possibility of a 110/80 (as opposed to the stock 110/90) front tire to offset the wider rear. That is precisely my question, will this change to the front (slightly lower profile) offset the wider, hence, harder (slightly) to turn in rear?

PAAS · 07-21-2008

Quote:

Originally Posted by Lucid

Bob,

In my initial post I reference the possibility of a 110/80 (as opposed to the stock 110/90) front tire to offset the wider rear. That is precisely my question, will this change to the front (slightly lower profile) offset the wider, hence, harder (slightly) to turn in rear?

What bike do you have? If it's a Thrux or Bonnie/T100 then the stock front tyre is 100/90, not 110/90. Don't know about Speedies and Americas. I run a 140/80 Metzeler Lasertec on the rear with 100/90 front Lasertec on my T100 and didn't notice any change in the speed of turn-in either way. As the 140/80 gives a slightly larger diameter to the rear wheel than the stock 130/80 and therefore jacks the rear up slightly, you might expect it to quicken the steering. In my case, if it did, it wasn't very noticeable. It's always hard making objective assessments when changing tyres as you're usually comparing brand new rubber with knackered old tyres way past their best.

My advice would be to go for Sport Demons in the standard size for the front and either standard or 140/80 for the rear. Don't expect to get 11k miles out of them though. If you do try a lower profile front tyre, remember that it will make your speedo even more inaccurate than it is already! People wanting higher mileage have had success with Metzeler 880s. Ultimately you pays your money and takes your choice. Tyres are a very personal thing so you have to try them for yourself. For example, a lot of people complained about the Bridgestones they used to fit to the Bonnie, but a few people liked them and keep using them.

Gob-ny-geay · 07-21-2008

It's all about leverage, and fulcrum points of the front/rear tire steering geometry. Different widths and aspect ratio's provide different locations for contact patch areas whens the bike is leaned over. Consider the original centerline on the ground of the bike and tires, straight up. Now lean the bike over at say 45 degrees, and visualise the off-center angle of that original centerline, and the contact patch location of the now wider rear tire. It will be off-center a tad from the front, causing the bike to handle differently than originally designed.

Now, mind you it will be miniscule if you don't overdo it in turns, and only noticable if you truly lean hard into turns. This is why some might say "Hey, I did this to mine, and it handles great!"

The bike will have a tendancy to want to stand up Vs. lean over (centripetal force). Gravity (leaning over) and Centripetal (standing up) forces need to be kept in balance to prevent the bike from low or high siding on you. Or, think of it as the front tire will be taking one specific radius path through the turn, the widened rear attempting a different specific radius from the originally designed path, the result being... not good.

What is required is to increase the tire sizes in the same exact ratio, front and rear, at the same time. That said, my humble recommendation/option for you would be to consider a different tire, but leave the tire sizes/aspect ratio's alone.

Oddly, most Bike manufacturers look for a performance / price balance on new bike tire offers. The Metzeler's are not exactly the least expensive on the market, and have had good reviews/bad reviews on this subjective forum, but predominantly good reviews on objective tests on bike related consumer testing.

How about just a straight up swap with the Sport Demons, without changing any sizes?

M700R · 07-21-2008

In the past I've gone the bigger tire route and ended up with a heavier handling bike. This time I just replaced the stockers with better tires of the same size and am very pleased. Handling improved, and the Triumph stayed easy to flick into a turn.

NewOldSkool · 07-23-2008

Go with the bigger rear tire, and drop the front 10mm. That should counter the neg effects and give your bike a meaner look, from what I imagen you are going for. Dont bother with a different size front until you have to replace it.

BeastInBlack · 07-24-2008

fat rear tyres are only needed on custom bikes that are for show, or bikes that have alot of power and need all that tyre to put it on the road.

lindsayt · 07-24-2008

Quote:

Originally Posted by BeastInBlack

fat rear tyres are only needed on custom bikes that are for show, or bikes that have alot of power and need all that tyre to put it on the road.

Yup. And in terms of what *NEEDS* all that tyre to put it on the road, keep in mind that the Suzuki Hayabusa lays down 194 hp using 180mm rubber. I'm pretty sure there's no production bike that needs more than 180mm if the Suzuki engineers deemed that acceptable for the 'busa.

And our little ~60hp motors certainly aren't going to exceed the limits of 130mm tires. I sort of think the tires should be as narrow as you can get away with for the horsepower you have, since narrower tires = better handling. I doubt even a 988 kit would merit wider tires for the power it delivers.

VTbob · 07-25-2008

Like every one has said, changing tire size will effect handling and shock tuning. If all you want is quicker turn in, you can replicate the Thuxton set up. or drop the front fork mounts to decrease the fork angle,or shorten the fron fork springs...to get similar result.

I think the safest is to get good sport tires of the same size as stock and see if that meets your needs. If not, talk to someone who has raced the Thriump and really knows how it's suppesion responds to different mods.

It is a lot easier to mess suspension tuning up than make them better.