Confused by Load Rating BT-023 and others

[RobsTV]

How can two tires made by the same manufacturer, both with the same load rating, have one recommended and one not?

For example, the BT-023 GT 180/55ZR17M/C (73W) is load rated the same as non-GT BT-023. The non-GT is available in my rear tire size.

My concern is that I ride fully loaded 2-up most of the time on an ST1100, so need a tire that can handle the 400-450lbs of total weight. When comparing tires, it looks like viewing load rating is useless as a comparison guide.

Noticed a post by Gene that said he had terrible rear wear 2up with the BT023 (one of the worst tire wear ever). Has anyone else used the BT023 rear fully loaded, and has decent wear?

https://www.st-owners.com/forums/showthread.php?82860-Bridgestone-BT-023&p=1036781&viewfull=1#post1036781

I was hoping to go with a set of 023's on the ST, but now it looks like Storm II rear and BT-023 front as best choice. Must have excellent rain grip, long life, and the funky ST1100 size. (original storms went 22,000 front and 11,000 rear, 2up and fully loaded).

Found a new (to me) fitment guide that shows the 023's as a correct replacement for the ST1100.
http://www.bridgestonebikersclub.co.uk/guide/


Thanks for any input,
Rob

 

[dduelin]

The 180/55 series GT spec tire may have a different rubber compound compared to the non-GT 180/55 spec yet have the same lay-up and belt construction that yields the same load rating of 805 lbs (73W). It would seem that you would run the narrower 160/70 rear that is OEM anyway which is load rated 805 lbs. If there is a problem I believe it to be in the marketing term "GT Spec" that has no basis in a standard. At least load ratings are easily understood and compared and the tire maker at least attests a tire meets the DOT standard to be so labeled and sold.

There is a USA Bridgestone site at http://www.motorcycle-karttires.com/index.aspx but it guides you to bias ply tire fitment for the ST1100.

In the UK there are requirements to mount approved tires and you can be in violation of the law or not pass the annual vehicle inspection if you are on non-approved tires. Perhaps a UK resident can chime in. There is no such requirements of course over here.

 

[RobsTV]

Besides Bridgestone's GT, I think the PR2 also comes in a heavy weight "B" version for heavier bikes, yet also has same load rating as standard non B version. Also the 020's U or "F" for heavy bikes (iirc).

At least with the Storm's, they state reinforced and bump the rating from 73 to 79 on those tires.

But the other brands say special version made for heavy bikes, yet same load rating? How can that be?

EDIT: with a load rating of 73, or 805 lbs, on a bike that weighs 700 lbs + 450 lbs = 1150 lbs, under accelleration when the front wheel is off the ground or very light, all that weight has to be supported by that 805 lb limit rear tire. So I can see where the ST needs a higher load rating than 73.

 

[dduelin]

I don't think one-wheel traveling is a problem on a touring bike but you never know.

Seriously, load ratings take into account short duration events that dramatically increase the "load" on the tire. Otherwise the first pot hole or deep curb you cross would blow the tires. There is a margin built into tire load ratings and the manufacturer has a good idea what type of tire will meet the needs of the motorcycle and places these on the DOT placard on the bike and in the owner's and service manuals. This load rating should take into account wheelieing and acceleration factors as well as overloading the bike on tires with low pressure then riding at high speed. We have to be protected from ourselves.

What was the Honda requirement for load rating originally on your ST1100? Even the BMW K1200LT which runs a 160/70-17 rear takes a load rating of 79W, 963 lbs., and it has a max gross weight of over 1300 lbs.

 

[RobsTV]

What was the Honda requirement for load rating originally on your ST1100? Even the BMW K1200LT which runs a 160/70-17 rear takes a load rating of 79W, 963 lbs., and it has a max gross weight of over 1300 lbs.

Looks like max total GVWR stamped on frame is 1078 lbs, based on stock original 1993 Bias ply tires load rating. Don't know why, but the seperate numbers on frame don't add up to total numbers on frame, with F GVWR = 403 lbs and R GVWR = 699 lbs.

Same size 160/70-17 rear that the K1200KT uses. On the ST1100, have been using the 79W Storm and Storm II, (both stamped reinforced), for last few changes.

If tires are replaced with higher load rating, then total GVWR will also go up.
At 700 + 450 (+/- mainly +) = 1150+ lbs, looks like we are over stock rated tires GVWR.

EDIT April 14th. Ended up installing a set of BT023's today.