Hi All,
I have been reading this board for the past two months now and thanks to everyone who contributes. I have learned a lot about my new baby G. I've read every tire thread I could find, including Pablo's great site and anything else that related to tires.  After putting about 1.2k miles on my bike I got a nail in the rear tire and had to get a new one.  I ended up with the folllowing:
140/70R-17 Dunlop D-208 Sportmax

The front tire is a sport touring standard size 110 bias ply.

Ok, so I just want to confirm that it is ok to run the radial on the rear and the bias ply on the front.  From what I've read here, and from what GS jack has written it is ok.
If it's not I will gladly get a new front tire as well, although I'd kinda like to wear out the one I've got 

Keep in mind that this is all new to me and I want to learn as much as possible, but being safe on the road is my number one concern.
Thanks
Michelle

I would go w/ GSJacks advise 100% He knows  IMO its best to have a matched set 


Welcome to the board 

I've run mismatched tires all over the place.  The bike won't blow up.

My main consideration when running mismatches, however, is to always have the grippiest tire on the front.  Losing the rear is no big deal, and can be quite fun.  Losing the front is generally a lot less fun and a lot more painful.  I'd guess your 'sport touring' front is a harder and less grippy tire than the D208.

The only 140/70R17 D208 rear tire I've heard of is the Dunlop D208 SM tire made for Supermoto bikes.  It's a high performance street tire sized for the 4.5" wide rims on Supermoto bikes and would be squeezed down a full inch to fit our 3.5" rear rim.  Most 140/70 tires are sized for 4.0" rims and are squeezed down only 1/2" on our rims and some are even being sized for 3.75 and 3.5 wide rims now. 

If your tire is the D208 SM tire I don't think I'd want to run it on a GS500 standard rear rim.  If I had one on my bike I guess I'd try it out carefully to see what it does.

Using a radial front with a bias rear is not approved by the tire makers and is actually illegal across the big pond to the east (EU).  A bias front with a radial rear can work OK and I've had good results with Lasertec bias fronts and Avon and Conti sport touring radial rears for example.

Mixing sport touring and supersport radials is usually done with the stickier supersport on the front.  If your front was a radial sport touring tire it still wouldn't be a good mix with the SM radial rear.

Thanks so much for the reply. I am pretty sure that is the tire I have. I did not realize a 140 would be sized different depending on the type of tire.
It does feel weird sometimes, like its fishtailing a little bit. I've only put 85 miles on it and I seem to be getting used to the different feel. It's like it feels everything on the road as opposed to my old one which was a 130 sport touring.
Being so new a riding it's hard for me to distinguish something that feels wrong as opposed to just different. It seems to be pretty stable at freeway speeds and I haven't really testing it for cornering becuase they said to go 100 miles before I reallly started leaning into corners.
If I decide to keep it on, I will put a tire to match on the front becuase I really do want to run a match set.

What are the consequences of sqeezing it down to fit the rim?  If there is any reason at all that it might not be safe it's coming off today!
Thanks again for your input.

if you like to do things by the book..... the book says do NOT mix radial and bias ply... that could be why your back end feels squirly at times.

deforming a tire to fit the rim is ok to a point from what I've read here but I'm no expert. I run 140 BT45's in the back and haven't had any issues but I think these are just squeezed the half inch... the more you mis-shape the tire the more chance you take...

just my .02.

sorry to bring the bad news side of this debate. just saying I personally wouldn't run your set up. this doesn't mean the bike is gonna blow up though, as roadstergal writes... maybe just the tire.... at speed...

I'm such a killjoy.


d

Well I wouldn't put that tire on a GS mostly because there are many better choices but like I said above if I had one on already I'd try it and most likely use it up with the present front tire unless I found something I really didn't like about the combo. 

Tires change and times change and what was good yesterday may not be so good tomorrow.  Just a couple years ago tire makers were saying to put the radial on the rear if you mix with bias and now it seems they all say just don't mix unless the tire maker or bike maker approves of the mix. More bikes are coming from the factory now with a bias/radial mix including some of the big HD cruisers.

Altering the tires shape can have an effect on handling and also on straight line stability but not often to a degree that will be dangerous, just doesn't work as well.  While it's desirable to have the stickier tire on the front if your pushing the limits it really won't make that much difference if your not even approaching the limit of the bias front tire.

Here's a bit from Sport Rider magazine about squeezing down tires on narrower rims, bike didn't blow up or even crash, just didn't work as well:

http://www.sportrider.com/tech/tires/146_0206_tire_size/index.html

As I frequently say; your bike, your life, your choice.   

One thing that always comes to my mind when talking about squeezing bigger tires down to fit narrower rims is Metzeler's campaign to sell their ME880 cruiser/touring tires on the NA market to riders wanting larger rear tires for appearance reasons.  They list Stage 1, 2, and 3 fitments with Stage 1 being ones that go on without any alterations having enough clearance for the larger tire.

Their Stage 1 fitment for a 1100 cc Honda Shadow for example is a 200/70B15 ME880 on a 3.5" wide wheel to replace the oem 170/80B15.  They have tested these fitments and consider them safe enough to sell in our overly litigeous society but one has to wonder how much they compromise on handling.   

Standard general fitment range for that 200/70B15 ME880 according to Metzeler is 5.5-6.5" rims.  I wouldn't put one of those on my 3.5" GS rim either but it does make your 140/70 D208 fitment look a lot better.   

Thanks to everyone who has responded, I have learned more about tires in the last week than I thought possible
I went back to the Suzuki service shop and had them order me a radial tire for the front. Unfortunately I can't get a match for the 208 because they don't make a 110, but at least both tires will be the same type.
The lesson I learned from this is to stick with stock unless I know exactly what the hell I am doing! And when these tires wear out I am going back to the good ole stock sport touring tires.
I did take the baby G out for a 3 hour ride yesterday and the tires performed just fine.  The weather here in Salt Lake is around 100 degrees and I noticed once the tires heated up they didn't feel as mismatched. I definitely do not reccomend having a hard tire on the front and a soft on on the back but I'm not exactly pushing the limits of anything right now.