as title states i have a question about the speed ratings on tires.
i know what a speed rating is, however i need to know is it undesirable to have different speed ratings on the same manufacture and type of tire from front to rear.

example: looking to get pirrelli sport demons sized 120\70 17 speed rating v and a 140\70 17 speed rating H.

V= 149 Mph rating 
H= 130 Mph rating

cannot seem to find the 140\70 17 in a V rating. should i just go with a 110\70 17 in front that has an H rating also?

GS will NEVER get that fast.

 I think he's more concerned about mixing different speed rated tires and wondering if it will adversely affect the way the bike handles.

I've heard plenty about mixing radials and bias ply tires, but never anything about speed ratings. I wouldn't worry about it.

I've not been concerned with the different speed ratings as long as all are greater than the bikes speed.  Best handling tires I've had on my GSs in my opinion were a H rated bias Lasertec front with a ZR RoadAttack radial rear with a W rating. W=168mph  Other way around I ran a couple sets of ZR rated Z4 fronts with HR rated Z2 rears, all Metzeler radials.

I ran many 110/70 and 110/80 front tires but only tried one 120/70 front with a 140/70 rear, both Roadriders.  Wasn't much difference between the 110/70 and 110/80 as far as handling goes on the GSs for me but the 120/70 was different.  I liked it very much at first, it just fell into corners due to it's rounder pinched down shape but after it was half worn and shape changed it felt sluggish and I put a half worn 110/70 Roadrider mounted on anothr wheel on and liked it better.  I'll stick with the 110s on the GS fronts, can't say I wouldn't put that 120 back on if I needed it in a pinch, it wasn't that bad, just not as good as the 110.

http://img.photobucket.com/albums/v443/jcp8832/GS500tirelogs.jpg

Thank you very much for the insight gsjack. Just what I was lookin for. I suppose ill go with the 110 front and 140 rear. It ends up being a few dollars cheaper.