I have a 2010 street glide with a 200/50/18 metzler 880 rear tire with only 7000 miles on it cupped real bad thinking about getting a dunlap 200/55/18 . what im wondering is what is the difference in the size and tires

 

In theory you would have a taller tire. 200 is the widest part of the tire ( the section width, not the tread width), the 50 or 55 is the sidewall height in percentage. So a 200/50 would mean a tire 200 wide with a sidewall height of 100mm. A 200/55 would mean a tire 200 mm wide and a sidewall height of 110mm. Or 10% larger in overall diameter.

 

In reality the fitted dimensions of any tyre can differ significantly from the stated size. As examples I have a 160 which measures 167mm wide on my wheel, but I have also had a 140 that measured only 139mm wide. So while the theoretical differences are easy to define, the actual sizes may not be the same!

To rework Rickl's figures, a 200/50 gives a sidewall height of 100mm, or rolling diameter of 23.87", while a 200/55 gives a rolling diameter of 24.66", which will theoretically raise the seat of your bike by around 3/8".

 

Consider yourself lucky! I just put 5,850 miles on my rear 200/50 Metzeler 880 and it is SHOT!

I'm now looking to change brands and go with the Michelin Commander II's, but they only offer the rear in 200/55. I am concerned with possible rubbing under the fender going with the slightly bigger 55.

 

The 200/18 rear tire is known to cause a high speed wobble on newer baggers (09+). We recommend a 180/55/18 on that size rim which is an 18x5.5. Try the Pirelli Night Dragon.

 

The 888 is supposed to be a big improvement over the 880 as far as longevity. As far as cupping the most likely culprit is improper tire pressure.

 

My current rear is a 200/50ZR 17 and not very many manufacturers are making the 200/50 and matching 21 front. I've gone through 2 sets of 880's and at this point, I regret changing the rear rim from stock. I am almost at the point of buying the stock 2009 size rim and putting the original size tire back on, but I am running a 21 on the front and don't know if I will f'up the ride or have to change the suspension.