| Author | Message | ||
     Bobsims |
All, Does anyone know the thread size for the holes located on the underside of the Uly passenger grab rails/triple tail mount? These are the holes used to mount the topmost fittings of the OEM luggage rack. I am fitting an aftermarket Fehling toprack. The kit includes metric M8 bolts for these holes. This seems a bit odd, because the other fasteners beneath the seat are all SAE 1/4" coarse thread. The M8 bolts seem to fit, but not so smoothly. Thanks in advance for any assistance. Bob | ||
| Etennuly |
I just replaced a couple of mine. They are not metric. The ones I needed were the 1/4 20's. You are looking at the larger ones on the rails. I just pulled one out to check and believe you will find them to be a 5/16 18 thread. | ||
| Florida_lime |
Bobsims, Do the directions or item sheet say that they are M8 bolts ? Could they be 5/16 bolts ? There is only a couple thousands difference between 5/16 and M8 on the O.D. I'm not sure about the pitch off the top of my head. | ||
| Chris_in_tn |
When you get a chance, I'd like to see a picture of the Fehling rack. I have Googled it since you first mentioned them and can't seem to find any more pictures or a retailer. | ||
| Jackbequick |
Most M8 bolts have a 1.25mm pitch which equates to an inch pitch of 0.4921". That works out to 20.3 TPI. A 1/4-20 TPI bolt has a thread pitch of .050" and will fit loosely in an M8 thread. But will only engage the threads lightly and threads are likely too get stripped if you try to tighten the bolt. A M8 bolt is too large (by about 1/16") to get started in a 1/4-20 thread. I don't think even a strong and persistent guy can get one started. A M8 bolt has an inch diameter of 0.315", a 5/16"-18 TPI bolt is 0.3125 inches in diameter. It will feel a little snug because of the thread mismatch but you can get either one started in a hole threaded for the other. It will keep getting tighter as more threads are engaged. The higher grade metal will prevail and some damage will take place. All this is due to an unfortunate confluence of the Metric and Imperial measuring systems on M8 and 5/16" bolt sizes. Jack | ||
| Bobsims |
Oops, I think I just snugged up two M8 bolts into 5/16"-18 holes...  I may just leave them there, as they are tight, and I'm afraid removal may damage the alloy threads beyond repair. FWIW, the left side M8 bolt went in without too much trouble, but the right side was clearly "too tight to be right". Thanks to all for the responses, esp. Etennuly and Jackbequick -- a lot more detail than I was expecting. It would be most helpful if anyone could confirm with certainty that the holes on the bottom of the passenger grab rails/triple tail mount are indeed 5/16"-18. I could try to correct my own, and pass this info along to Fehling so that they correct the hardware in their kit. Their current mounting instructions show these holes as M8. Chris_in_tn: I installed the top and side luggage racks last night, and rode to work this morning with my Givi E45 sidecases attached. I will follow-up with a review and pictures once the weather here improves a bit. In the meantime, I have some manufacturer-supplied photos of the racks on my website here. The top rack can be mounted without the side racks, or vice-versa, or they can be mounted together. Other than the bolt issue above, the kit went on easily. The racks appear to be a bit spindly at first glance, but they are strong once installed. The tubular rack design is very popular here in Germany amongst all types of riders. Thanks again to all for the responses. Bob | ||
| Etennuly |
Bob, I did pull one out and use a vernier caliper along with a thread guage. It led me to that conclusion along with testing a 5/16 18 bolt out of my bolts bin to confirm. It's not to say I had nothing else to do, I just felt like doing it. You are welcome sir!  | ||
| Lorazepam |
I like that rack set up a lot. It would be nice to be able to lower the beaver tail to the rear, which you cant do with the hb setup. Givi bags rock! I low sided with a set on a beemer, the case and the cylinder guard protected the rest of the bike really well. | ||
| Chris_in_tn |
I wonder why no one in the U.S. has them. Seems like they would be fairly popular. I would have considered them if they had been available. |
