Maximum Rear Tire size.

[GS750GUY]

I have a 78 GS750EC with the stock cast wheels and I'm wondering what is the largest size tire I can safely put on my stock rear wheel.
I replaced the rubber on both wheels a while back and found the rear tire is only just slightly fatter (or larger in appearance) than the front tire.
I like the appearance of a bulkier rear tire and next time I replace the rear rubber I want to do it with the largest that is safely possible.
I appreciate your wisdom in this.

GS750GUY

[C.V.]

Stock size is a 120 for this model? I don't think you can go any bigger than that on the E model as the rim is too narrow (don't quote me however) If you have a 130 stock, and you can clear the swingarm, yopu can run a 140, but lots of people say it compromises handling due to pinching the tread pattern (again, the narrow rims). That being said, I am currently running a 140 on the rear of my '79 850, and have noticed no handling issues. I am going back to stock size soon though.

[Hammered]

Stock on that model should be if I read correctly is a 130/90. See what size the rim is and you can cross check it to this.

http://www.dropbears.com/u/utilities/tyrerim.htm

[Nessism]

Wheel on that model is 2.15 x 18. Max tire size is a 120 on a wheel that wide.

Stock tire size was 4.00 x 18 which is about a 110 in modern sizes, although technically it's a 100.

[nisom512]

Wheel on that model is 2.15 x 18. Max tire size a 120 on a wheel that wide.

Stock tire size was 4.00 x 18 which is about a 110 in modern sizes, although technically it's a 100.

he said cast wheels so wouldnt that mean it is a 16?

[Nessism]

he said cast wheels so wouldnt that mean it is a 16?

16's were only used on L models, and on the 1100GK. Most regular GS rear wheels were 17" but a few were 18".

[GS750GUY]

Ok. I looked up the invoice from my bike file and find I purchased Dunlop D404 tires.
Front.....100/90-19
Rear......110/90-18
Does this mean from your responses that I can then safely go to a 120/90-18? But a 130 would be too big?

GS750GUY