Mixing Tires.

[Guest]

So, I've gotten to a point in my build that I'm ready to buy tires. Problem is, no one makes the same tire for front and rear that I'm looking for (130-90-18 rear, and 120-90-17 front). Both the tires I'm looking at are Aramid belted, tubeless, and of the "sport touring" variety. My question is, will they work together? Will they be safe?


Here are the two I'm looking at...


Rear:

http://www.motorcycle-superstore.com/1/28/395/6188/ITEM/Shinko-230-Tour-Master-Rear-Tire.aspx

Front:

http://www.motorcycle-superstore.com/3/31/401/41865/ITEM/Michelin-Commander-II-Cruiser-Front-Tire.aspx

[tkent02]

Some mismatches work fine, others handle like crap.
What's the point? There are good matched pairs of tires available.

[TheCafeKid]

Are you using a stock GS front rim? 120 is way too wide. It will crown/pinch and actually reduce contact patch rather than increase it. On a stock GS rim 100 or 110 on some later models is the widest advisable.

Nevermind I just re-read and saw your front is a 17". Off of what??

[DrunkenChekhov]

'03 CBR954RR. Thus, no one makes a modern sport bike front, and old standard rear tire combination.

[TheCafeKid]

'03 CBR954RR. Thus, no one makes a modern sport bike front, and old standard rear tire combination.

Did you use the entire front end or just the rim?? Got a pic? Just curious. I like seeing some of the mods people come up with...gives me ideas..

[DrunkenChekhov]

Whole front end. You can see a very terrible picture of it in my build thread in my sig.

[bwringer]

Mixing brands is no big deal.

However, that oddball size combination will handle a little strange -- I'm thinking the front will end up feeling really heavy.

Anyhoo, that aside, I'd install a 70-series 110 up front -- that 120/90 would be WAY too stretched out on that wide front. A sporty 110/70-17 is easy to find in radial or bias -- it's the stock front size on the GS500.

[DrunkenChekhov]

Well, the reason I was thinking such a giant front tire is this: If you look at the photos of my bike with the front end, its got a pretty insane rake going on. The 954rr's front end is a lot shorter than my stock GS, couple that with the fact that the 954 rim is shorter, and the new springs raised the rear a hair, I feel like my steering is going to be insanely twitchy if I rock a 70 series tire.


Correct me if I'm wrong here, but the taller the tire, the slower the steering, right? So if my steering is really twitchy because of the rake, a tall tire in the front will solve this problem, yes?



Last question, what do you mean the 120/90 will be stretched? Not sure I understand. The front comes stock with a 120/70, btw.

[bwringer]

Last question, what do you mean the 120/90 will be stretched? Not sure I understand. The front comes stock with a 120/70, btw.

Solving the handling problems arising from that drastically shorter fork will take much, much more than a taller tire. You may have fancy forks that work better in their intended environment, but if the nose is a lot closer to the ground, you're going to drag the engine cases long before you can realize any handling benefit. And as you mentioned, it will be very, very twitchy if not completely unrideable. (And what about spring and damping rates -- what's the weight and weight distribution difference between the CBR and your 650?)



Anyway, what I meant about the tire is that the 90-series front tire is meant for a much narrower rim (2.75") than the 70-series tire (probably 3.5"). This is going to stretch the tire horizontally, and you'll end up with a very strange profile. Envision the tire's cross-section when mounted on the correct rim width (smooth arc), then envision the beads pulled apart. The profile is going to flatten out, and it does not flatten out evenly because of the limitations of the construction.